Inlet guard and thrust bearing for blood pump

Abstract

An apparatus and method are described that includes an axial shaft (92) configured to be inserted into and rotate within a ventricle of a subject's heart. An impeller (50) is coupled to the axial shaft (92), and a frame (34) surrounds the impeller. A pump outlet tube (24) surrounds the frame such that, as the axial shaft (92) rotates, the impeller (50) pumps blood proximally from the ventricle through the pump outlet tube (24). An inlet guard (400) shaped to define one or more holes (402) is disposed around the axial shaft (92) and within the frame (34) distal to the impeller (50) so that blood flows through the holes (402) to the impeller (50). Other applications are also described.

Description

[Technical Field]

[0001] (CROSS-REFERENCE TO RELATED APPLICATIONS) This application is U.S. Provisional Patent Application No. 63 / 406,427, entitled "Ventricular assist device," filed September 14, 2022, by Tuval; U.S. Provisional Patent Application No. 63 / 432,496, filed December 14, 2022, to Tuval, entitled "Ventricular assist device"; U.S. Provisional Patent Application No. 63 / 443,519, entitled "Ventricular assist device," to Tuval, filed February 6, 2023; and This application claims priority to U.S. Provisional Patent Application No. 63 / 470,259, entitled "Ventricular assist device," filed June 1, 2023, to Tuval.

[0002] All of the above US provisional applications are incorporated herein by reference.

[0003] Some applications of the present invention relate generally to medical devices, and more particularly to ventricular assist devices and methods of use thereof. [Background technology]

[0004] Ventricular assist devices are mechanical circulatory assist devices designed to assist and unload heart chambers to maintain or enhance cardiac output. They are used in patients suffering from heart failure and in patients at risk of compromised cardiac function during percutaneous coronary intervention. Most commonly, left ventricular assist devices are applied to failing hearts to assist left ventricular function. In some cases, right ventricular assist devices are used to assist right ventricular function. Such ventricular assist devices are designed to be permanently implanted or attached for temporary placement on a catheter. Summary of the Invention

[0005] According to some applications of the present invention, a ventricular assist device includes an axial shaft configured to be inserted into and rotate within a ventricle of a subject's heart, an impeller coupled to the axial shaft, and a frame surrounding the impeller. A pump outlet tube surrounds the frame, and as the axial shaft rotates, the impeller pumps blood proximally from the ventricle through the pump outlet tube. An inlet guard shaped to define one or more holes is disposed around the axial shaft and within the frame distal to the impeller, such that blood flows through the holes to the impeller.

[0006] In some applications, the inlet guard is flat and / or disposed perpendicular to the axial shaft (i.e., the longitudinal axis of the frame), thus advantageously occupying relatively little space and / or providing a favorable flow direction for the blood. Typically, the inlet guard is annular.

[0007] For some applications, the frame is assembled with the inlet guard therein in the following manner: During assembly of the pump head, the proximal end of the frame is typically open. For some applications, the inlet guard is supported on a rod (e.g., a mandrel) and placed through the open proximal end of the frame. The inlet guard typically has a generally torus shape, the edges of which define an inner circle and an outer circle. The inner circle defined by the inlet guard typically connects to the axial shaft (or distal bearing housing), and the outer circle connects to the frame struts, pump outlet tubing, and / or frame lining. For some applications, the inlet guard is connected to other portions of the device using sutures, hooks, adhesives, and / or heat seals.

[0008] As mentioned above, in some embodiments, the inlet guard is coupled to a distal bearing housing, which may house the radial and / or thrust bearings. In such embodiments, the distal bearing housing is typically disposed partially or completely within the frame. For example, at least 10%, 50%, or 80% of the length of the bearing housing may be disposed within the frame. Also, in applications where the blood pump does not include an inlet guard, the distal bearing housing may extend into the frame.

[0009] For some applications, the ventricular assist device includes a thrust bearing configured to reduce or prevent axial movement of the axial shaft in response to changes in the pressure gradient against which the impeller delivers (and typically thereby prevent the impeller from undergoing axial movement in response to changes in the pressure gradient against which the impeller delivers).

[0010] For some applications, a thrust bearing is disposed within the distal bearing housing adjacent the distal end of the axial shaft. Typically, the distal end of the axial shaft is configured to contact the distal thrust bearing. When the impeller pumps blood proximally, the axial shaft is urged distally. The thrust bearing prevents distal movement of the axial shaft, such that the axial shaft and the impeller typically remain in an axially fixed position within the frame.

[0011] In some embodiments, the thrust bearing portion includes a proximally facing ceramic surface, e.g., comprising zirconia. A distally facing ceramic cover, e.g., comprising zirconia, covers the distal end of the axial shaft such that the ceramic cover contacts the ceramic surface as the axial shaft rotates. Advantageously, therefore, there is a low-friction interface between the axial shaft and the thrust bearing portion.

[0012] In some embodiments, the axial shaft is shaped to define a shaft lumen. For some applications, the thrust bearing defines a bearing lumen therethrough. Typically, the bearing lumen serves as part of a continuous lumen through the device used for guidewire insertion and / or as a purge fluid channel. In other words, the bearing lumen is continuous with the shaft lumen.

[0013] For some applications, at least a portion of the bearing lumen is frusto-conical, with a wider end of the bearing lumen facing distally. In other words, at its distal end, the lumen defines a portion of a cone, with the wider end of the cone facing distally. Typically, the frusto-conical portion of the lumen facilitates advancement of a guidewire through the thrust bearing in a distal-to-proximal direction.

[0014] In some applications, the drive cable of the ventricular assist device is coupled to the axial shaft within a proximal bearing housing disposed within the frame. In other words, the interface between the distal end of the drive cable and the proximal end of the axial shaft (i.e., where the drive cable and axial shaft are coupled to one another) is within the proximal bearing housing. Because the proximal bearing housing is typically rigid, it protects the location where the drive cable and axial shaft are coupled to one another from forces, such as bending forces, that could weaken the coupling and damage the ventricular assist device. For example, the proximal bearing housing may restrict the drive cable from bending within the bearing housing.

[0015] Typically, in such embodiments, the radial distance between the proximal bearing housing and the distal end of the drive cable within the proximal bearing housing is less than 2 mm, e.g., less than 1 mm, which has the advantage that it can help to constrain bending of the drive cable.

[0016] In general, in the specification and claims of this application, the term "proximal" and related terms, when used with respect to a device or portion thereof, should be interpreted to mean the end of the device or portion thereof that is closer to the location where the device would normally be inserted into the subject's body when inserted into the subject's body. The term "distal" and related terms, when used with respect to a device or portion thereof, should be interpreted to mean the end of the device or portion thereof that is further from the location where the device would normally be inserted into the subject's body when inserted into the subject's body.

[0017] Thus, according to some embodiments of the present invention: an axial shaft configured to be inserted into a ventricle of the subject's heart and to rotate within the ventricle; an impeller coupled to the axial shaft; a frame surrounding the impeller; a pump outlet tube surrounding the frame, wherein as the axial shaft rotates, an impeller pumps blood proximally from the ventricle through the pump outlet tube; An apparatus is provided that includes an inlet guard shaped to define one or more holes, the inlet guard disposed about the axial shaft and within the frame distal to the impeller such that blood flows through the holes to the impeller.

[0018] In some embodiments, the pump outlet tube has an open distal end.

[0019] In some embodiments, the device further includes a drive cable, the axial shaft being coupled to the drive cable for rotation therewith.

[0020] In some embodiments, a drive cable is included and the axial shaft is a distal portion of the drive cable.

[0021] In some embodiments, the inlet guard is perpendicular to the axial shaft.

[0022] In some embodiments, the entrance guard is flat.

[0023] In some embodiments, the entrance guard is toroidal.

[0024] In some embodiments, the frame includes a plurality of struts, and the entrance guard is connected to the struts.

[0025] In some embodiments, the inlet guard is coupled to the inner wall of the pump outlet tube.

[0026] In some embodiments, the device further includes a liner lining the inside of the frame, the entry guard being coupled to the liner.

[0027] In some embodiments, the entrance guard is made of a polymer.

[0028] In some embodiments, the entrance guard has a thickness of 40 to 100 microns.

[0029] In some embodiments, the device further includes a thrust bearing disposed distally from the axial shaft, the thrust bearing preventing distal movement of the axial shaft beyond the thrust bearing.

[0030] In some embodiments, the holes are shaped such that for each hole, the span of the hole in at least one direction is less than 1 mm.

[0031] In some embodiments, each hole has an area of ​​0.05 to 5 mm 2 is.

[0032] In some embodiments, the inlet guard has a porosity of at least 40%.

[0033] In some embodiments, each hole is hexagonal.

[0034] In some embodiments, the distance between each pair of adjacent holes is 0.01 to 0.1 mm.

[0035] In some embodiments, the apparatus further comprises: a bearing configured to stabilize the axial shaft while the axial shaft rotates; a bearing housing that houses the bearing and is coupled to the inlet guard.

[0036] In some embodiments, at least 10% of the length of the bearing housing is disposed within the frame.

[0037] In some embodiments, at least 50% of the length of the bearing housing is disposed within the frame.

[0038] In some embodiments, at least 80% of the length of the bearing housing is disposed within the frame.

[0039] In some embodiments, the bearing housing is disposed entirely within the frame.

[0040] In some embodiments, the bearing includes a thrust bearing disposed distally from the axial shaft that prevents distal movement of the axial shaft beyond the thrust bearing.

[0041] In some embodiments, the frame includes a central cylindrical portion and a distal conical portion, and the entrance guard is disposed within 1 mm of the distal end of the central cylindrical portion.

[0042] In some embodiments, the distal end of the pump outlet tube is proximal to the distal end of the distal cone.

[0043] In some embodiments, the distal end of the pump outlet tubing is within 1 mm of the distal end of the central barrel.

[0044] According to some embodiments of the present invention, an axial shaft configured to be inserted into and rotate within a subject's body; an impeller coupled to the axial shaft to pump blood through the subject when the axial shaft rotates; a thrust bearing portion including a proximally facing ceramic surface disposed distally from the axial shaft to prevent distal movement of the axial shaft beyond the thrust bearing portion; a distally facing ceramic cover covering the distal end of the axial shaft so as to contact the ceramic surface as the axial shaft rotates; There is further provided an apparatus including a blood pump comprising:

[0045] In some embodiments, the device further includes a drive cable, the axial shaft being coupled to the drive cable for rotation therewith.

[0046] In some embodiments, the device further includes a drive cable, and the axial shaft is a distal portion of the drive cable.

[0047] In some embodiments, the thrust bearing portion includes a ceramic piece including a proximally facing ceramic surface.

[0048] In some embodiments, the thrust bearing portion includes a proximally facing ceramic surface that is coated with a ceramic coating.

[0049] In some embodiments, the proximally facing ceramic surface comprises zirconia.

[0050] In some embodiments, the distally facing ceramic cover comprises zirconia.

[0051] In some embodiments, the blood pump further includes a distal bearing housing that houses the distal thrust bearing, and a distal radial bearing housed within the distal bearing housing and configured to radially stabilize the axial shaft while the axial shaft rotates.

[0052] In some embodiments, the axial shaft is configured to be inserted over a guidewire and is shaped to define a shaft lumen through which the guidewire passes, and the thrust bearing portion is shaped to define a bearing lumen configured to be continuous with the shaft lumen.

[0053] In some embodiments, at least a portion of the bearing lumen is frustoconical, with a wider end of the bearing lumen facing distally.

[0054] In some embodiments, the bearing lumen is a first bearing lumen and the thrust bearing portion is further shaped to define at least one second bearing lumen configured to direct purge fluid through the second bearing lumen in a proximal direction to an interface between the axial shaft and the thrust bearing portion.

[0055] In some embodiments, the blood pump includes a ceramic cover and a ceramic cap that fits around the distal end of the axial shaft.

[0056] In some embodiments, the blood pump includes a distal radial bearing configured to radially stabilize the axial shaft while the axial shaft rotates, and the ceramic cap includes a ceramic sleeve configured to cover a distal portion of the axial shaft that rotates within the distal radial bearing as the axial shaft rotates.

[0057] According to some embodiments of the present invention, there is provided an axial shaft configured to be inserted into a body of a subject over a guidewire and to rotate within the body, the axial shaft comprising: an axial shaft shaped to define a shaft lumen through which a guidewire passes; an impeller coupled to the axial shaft to pump blood through the subject when the axial shaft rotates; a thrust bearing portion disposed distally from the axial shaft to prevent distal movement of the axial shaft beyond the thrust bearing portion, the thrust bearing portion shaped to define a bearing lumen configured to be continuous with the shaft lumen; There is further provided an apparatus including a blood pump comprising:

[0058] In some embodiments, the device further includes a drive cable, the axial shaft being coupled to the drive cable for rotation therewith.

[0059] In some embodiments, the device further includes a drive cable, and the axial shaft is a distal portion of the drive cable.

[0060] In some embodiments, at least a portion of the bearing lumen is frusto-conical, with a wider end of the bearing lumen facing distally.

[0061] In some embodiments, the bearing lumen is a first bearing lumen and the thrust bearing portion is further shaped to define at least one second bearing lumen configured to direct purge fluid through the second bearing lumen in a proximal direction to an interface between the axial shaft and the thrust bearing portion.

[0062] In some embodiments, the thrust bearing portion includes a proximally facing ceramic surface, and the blood pump includes a distally facing ceramic cover that covers the distal end of the axial shaft so as to contact the ceramic surface when the axial shaft rotates.

[0063] In some embodiments, the thrust bearing portion includes a ceramic piece including a proximally facing ceramic surface.

[0064] In some embodiments, the thrust bearing portion includes a proximally facing ceramic surface that is coated with a ceramic coating.

[0065] In some embodiments, the proximally facing ceramic surface comprises zirconia.

[0066] In some embodiments, the distally facing ceramic cover comprises zirconia.

[0067] In some embodiments, the blood pump further includes a distal bearing housing that houses the distal thrust bearing, and a distal radial bearing housed within the distal bearing housing and configured to radially stabilize the axial shaft while the axial shaft rotates.

[0068] In some embodiments, the blood pump further includes a ceramic cap that fits around the distal end of the axial shaft and includes a ceramic cover.

[0069] In some embodiments, the blood pump includes a distal radial bearing configured to radially stabilize the axial shaft while the axial shaft rotates, and the ceramic cap includes a ceramic sleeve configured to cover a distal portion of the axial shaft that rotates within the distal radial bearing as the axial shaft rotates.

[0070] According to some embodiments of the present invention, there is provided a device for performing a method of performing a surgical instrument, the device comprising: an axial shaft configured to be inserted into and rotate within a body of a subject; an impeller coupled to the axial shaft to pump blood through the subject when the axial shaft rotates; a frame surrounding the impeller and including a distal cone; a bearing portion adjacent to the axial shaft and configured to stabilize the axial shaft during rotation of the axial shaft; a bearing housing that houses the bearing and is at least partially disposed within the distal cone portion of the frame; There is further provided an apparatus including a blood pump comprising:

[0071] In some embodiments, the device further includes a drive cable, the axial shaft being coupled to the drive cable for rotation therewith.

[0072] In some embodiments, the device further includes a drive cable, and the axial shaft is a distal portion of the drive cable.

[0073] In some embodiments, the bearing housing occupies at least 10% of the length of the distal cone of the frame.

[0074] In some embodiments, the bearing comprises a radial bearing configured to radially stabilize the axial shaft while the axial shaft rotates.

[0075] In some embodiments, the bearing comprises a thrust bearing configured to axially stabilize the axial shaft while the axial shaft rotates.

[0076] In some embodiments, the frame further includes a cylindrical portion proximal to the distal conical portion, the bearing housing being at least partially disposed within the cylindrical portion.

[0077] In some embodiments, at least 10% of the length of the bearing housing is disposed within the frame.

[0078] In some embodiments, at least 50% of the length of the bearing housing is disposed within the frame.

[0079] In some embodiments, at least 80% of the length of the bearing housing is disposed within the frame.

[0080] In some embodiments, the bearing housing is disposed entirely within the frame.

[0081] In some embodiments, the bearing is a distal bearing and the bearing housing is a distal bearing housing; The frame further includes a proximal cone; The blood pump also a proximal bearing portion adjacent the axial shaft proximally of the distal bearing portion and configured to stabilize the axial shaft during rotation of the axial shaft; a proximal bearing housing that houses the proximal bearing and is at least partially disposed within the proximal cone portion of the frame.

[0082] In some embodiments, at least 10% of the length of the proximal bearing housing is disposed within the frame.

[0083] In some embodiments, at least 50% of the length of the proximal bearing housing is disposed within the frame.

[0084] In some embodiments, at least 80% of the length of the proximal bearing housing is disposed within the frame.

[0085] In some embodiments, the proximal bearing housing is disposed entirely within the frame.

[0086] In some embodiments, the proximal bearing includes a proximal radial bearing configured to radially stabilize the axial shaft while the axial shaft rotates.

[0087] In some embodiments, the proximal bearing includes a proximal thrust bearing configured to axially stabilize the axial shaft while the axial shaft rotates.

[0088] In some embodiments, the frame further includes a cylindrical portion between the proximal cone and the distal cone, the proximal bearing housing being at least partially disposed within the cylindrical portion.

[0089] In some embodiments, the distance between the proximal end of the proximal bearing housing and the distal end of the distal bearing housing is less than 10% greater than the length of the frame. [Brief explanation of the drawings]

[0090] [Figures 1A-1C]1 is a schematic illustration of a ventricular assist device configured with a distal end to be placed in the left ventricle of a subject, in accordance with some applications of the present invention. [Figure 2] 1 is a schematic diagram of a frame housing an impeller of a ventricular assist device, in accordance with some applications of the present invention. [Figure 3A-3G] 1 is a schematic diagram of an impeller or portion thereof of a ventricular assist device, in accordance with some applications of the present invention. [Figure 4] 1 is a schematic diagram of an impeller disposed inside a frame of a ventricular assist device, in accordance with some applications of the present invention. [Figure 5A-5B] 1A-1C are schematic diagrams of an impeller and frame of a ventricular assist device in radially unconstrained and radially constrained states, respectively, in accordance with some applications of the present invention. [Figure 5C] 1 is an enlarged schematic view of a proximal end of a frame of a ventricular assist device, in accordance with some applications of the present invention. [Figure 5D-5F] 1 is a schematic diagram of a coupling element, according to some applications of the present invention; [Figures 6A-6B] 1A-1C are schematic illustrations of a ventricular assist device at different stages of a motion cycle of an impeller of the ventricular assist device relative to a frame of the ventricular assist device, in accordance with some applications of the present invention. [Figure 6C-6D] 1 is a schematic diagram of a ventricular assist device including a motion damping spring, in accordance with some applications of the present invention. [Figures 7A-7D] 1 is a schematic diagram of a motor unit and / or a driven magnet unit of a ventricular assist device, according to some applications of the present invention. [Figure 7E] 1 is a schematic diagram of a motor unit, according to some applications of the present invention. [Figure 7F] 1 illustrates a cross-sectional view of a portion of a motor unit, according to some embodiments of the present invention. [Figure 8A] 1 is a graph illustrating the variation in length of a drive cable of a ventricular assist device as a function of varying pressure gradients relative to the delivery by the impeller of a blood pump, as measured in experiments conducted in accordance with some applications of the present invention. [Figure 8B-8C]10 is a graph demonstrating the correlation between a phase difference signal and a pressure gradient for pumping by an impeller of a blood pump, according to some applications of the present invention. [Figure 9A-9B] 1 is a schematic diagram of a ventricular assist device including one or more blood pressure measurement tubes and / or fibers, in accordance with some applications of the present invention. [Figures 10A-10C] 1 is a schematic diagram of a ventricular assist device including a liner inside the frame that houses the impeller, in accordance with some applications of the present invention. [Figures 11A-11E] 1 is a schematic diagram of a pump outlet tube defining a blood inlet opening at a distal end, in accordance with some applications of the present invention. [Figures 12A-12C] 1 is a schematic diagram of a drive cable for a ventricular assist device, in accordance with some applications of the present invention. [Figure 12D] 1 is a schematic diagram of a drive cable bearing tube, in accordance with some applications of the present invention; [Figures 12E-12H] 1 is a schematic diagram of a laser cut tube used for a drive cable bearing tube, in accordance with some applications of the present invention. [Figure 12I] 1 is a schematic diagram of a portion of a drive cable and drive cable bearing tube, in accordance with some applications of the present invention. [Figure 13] 1 is a schematic diagram of a delivery tube for a left ventricular assist device, in accordance with some applications of the present invention. [Figures 14A-14H] 1 is a schematic diagram of an interface between a drive cable and an axial shaft, in accordance with some applications of the present invention. [Figures 15A-15C] 1 is a schematic diagram of a portion of a continuous lumen defined by a ventricular assist device, in accordance with some applications of the present invention. [Figure 16A] 1 is a schematic diagram of a pump head portion of a ventricular assist device including a thrust bearing portion, in accordance with some applications of the present invention. [Figure 16B] 1 is a schematic diagram of a pump head portion of a ventricular assist device, according to some embodiments of the present invention. [Figure 16C] FIG. 16C is a schematic diagram of a distal portion of the pump head shown in FIG. 16B, according to some embodiments of the present invention. [Figure 16D]FIG. 16C is a schematic diagram of a proximal portion of the pump head shown in FIG. 16B, according to some embodiments of the present invention. [Figure 16E] 1 is a schematic illustration of a pump head portion of a ventricular assist device, the proximal portion including a thrust bearing portion, according to some embodiments of the present invention. [Figures 17A-17D] 1 is a schematic diagram of a distal tip of a ventricular assist device, in accordance with some applications of the present invention. [Figure 18] 1 is a schematic illustration of a steering mechanism used to steer a frame of a ventricular assist device relative to a proximally disposed portion of the ventricular assist device, in accordance with some applications of the present invention. [Figures 19A-19B] 1 is a schematic illustration of an expandable element surrounding a delivery tube of a ventricular assist device, in accordance with some applications of the present invention. [Figures 20A-20E] 1 is a schematic diagram of a pump outlet tubing of a ventricular assist device, in accordance with some applications of the present invention. [Figures 21A-21B] 1 is a schematic diagram of a distal bearing housing of a ventricular assist device, in accordance with some applications of the present invention. [Figures 22A-22D] 1 is a schematic diagram of a portion of a ventricular assist device including an inlet guard disposed within a frame of a pump head of the ventricular assist device, in accordance with some applications of the present invention. [Figure 23] 10 is a schematic diagram of a distal bearing housing of a ventricular assist device extending into a frame of a pump head, according to some applications of the present invention. [Figure 24] 1 is a schematic diagram of a distal tip of a ventricular assist device including a bidirectional valve, in accordance with some applications of the present invention. [Figures 25A-25B] 1 is a schematic diagram of a driven magnet unit including a two-way valve, according to some applications of the present invention. [Figures 26A-26B] 10 is a schematic diagram of a locking unit for securing a delivery tube to a delivery catheter, according to some applications of the present invention. [Figures 27A-27B] 10A-10C are schematic diagrams of locking units for securing a delivery tube to a delivery catheter, according to some alternative applications of the present invention. [Figures 28A-28B]10 is a schematic diagram of a locking unit for securing a delivery tube to an introducer sheath, according to some applications of the present invention. [Figure 29] 1 is a schematic illustration of a left ventricular assist device, in accordance with some applications of the present invention. [Figure 30] 1 is a schematic illustration of a ventricular assist device deployed within a subject, in accordance with some applications of the present invention. [Figure 31] 1 is a schematic illustration of a left ventricular assist device including a band on the pump outlet tubing, in accordance with some applications of the present invention. [Figure 32A-32B] 10A-10D collectively illustrate the assembly of portions of a left ventricular assist device, in accordance with some applications of the present invention. [Figures 33A-33C] 1 is a schematic diagram of a proximal end of a pump outlet tube, according to some applications of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0091] Reference is now made to Figures 1A, 1B, and 1C, which are schematic illustrations of a ventricular assist device 20 having a distal end configured for placement in a subject's left ventricle 22, in accordance with some applications of the present invention. Figure 1A shows an overview of the ventricular assist device system, including a control console 21 and a motor unit 23. Figure 1B shows the ventricular assist device being inserted into a subject's left ventricle, and Figure 1C shows a pump head portion 27 of the ventricular assist device in greater detail.

[0092] As shown in FIG. 1B , the ventricular assist device includes a pump outlet tubing 24 that traverses a subject's aortic valve 26 such that a proximal end 28 of the pump outlet tubing is disposed in a subject's aorta 30 and a distal end 32 of the pump outlet tubing is disposed within the left ventricle 22. Typically, the pump outlet tubing 24 (sometimes referred to as a "blood pump tubing") is an elongated tube, and the axial length of the pump outlet tubing is typically significantly longer than its diameter. The scope of the present invention includes use of the apparatus and methods described herein in anatomical locations other than the left ventricle and aorta. Accordingly, the ventricular assist device and / or portions thereof may be referred to herein (in the specification and claims) as a blood pump.

[0093] In some applications, ventricular assist devices are used to support the function of a subject's left ventricle during percutaneous coronary intervention. In such cases, ventricular assist devices are typically used for up to 6 hours (e.g., up to 10 hours) during a period of risk for developing hemodynamic instability (e.g., during or immediately after percutaneous coronary intervention). Alternatively or additionally, ventricular assist devices are used to support the function of a subject's left ventricle for longer periods (e.g., 2-20 days, e.g., 4-14 days) when a patient is suffering from cardiogenic shock, which may include a low cardiac output condition (e.g., acute myocardial infarction, myocarditis, cardiomyopathy, postpartum, etc.). In some applications, ventricular assist devices are used to support the function of a subject's left ventricle for even longer periods (e.g., weeks or months), for example, in "bridge to recovery" therapy. In some such applications, the ventricular assist device is permanently or semi-permanently implanted and the impeller of the ventricular assist device is powered percutaneously, for example, using an external antenna magnetically coupled to the impeller.

[0094] As shown in FIG. 1B , which illustrates the steps of deploying a ventricular assist device within the left ventricle, typically, the distal end of a ventricular assist device is guided into the left ventricle over a guidewire 10. During insertion of the distal end of the device into the left ventricle, a delivery catheter 143 is disposed over the distal end of the device. Once the distal end of the device is disposed in the left ventricle, the delivery catheter is typically retracted into the aorta and the guidewire is withdrawn from the subject's body. Retraction of the delivery catheter typically causes the self-expandable component at the distal end of the device to assume a radially unconstrained configuration, as described in more detail below. Typically, ventricular assist devices are inserted into a subject's body to provide acute treatment to the subject. In some applications, to withdraw the left ventricular device from the subject's body at the end of treatment, a delivery catheter is advanced over the distal end of the device, causing the self-expandable component at the distal end of the device to assume a radially constrained configuration. Alternatively or additionally, retraction of the distal end of the device into the delivery catheter causes the self-expandable component at the distal end of the device to assume a radially constrained configuration.

[0095] In some applications (not shown), the ventricular assist device and / or delivery catheter 143 includes an ultrasound transducer at its distal end, and the ventricular assist device is advanced under ultrasound guidance toward the target ventricle.

[0096] Reference is now made to FIG. 1C , which illustrates the pump head portion 27 of the ventricular assist device 20 in more detail, according to some applications of the present invention. Typically, an impeller 50 is disposed within the distal portion 102 of the pump outlet tubing 24 and is configured to rotate to pump blood from the left ventricle into the aorta. Typically, the pump outlet tubing defines one or more blood inlet openings 108 at its distal end, through which blood flows from the left ventricle into the pump outlet tubing during operation of the impeller. As shown in FIG. 1C , for some applications, the pump outlet tubing defines a single axially oriented blood inlet opening. Alternatively, the pump outlet tubing defines multiple lateral blood inlet openings (e.g., as shown in FIG. 1B ), as described in further detail below. For some applications, a proximal portion 106 of the pump outlet tubing defines one or more blood outlet openings 109 through which blood flows from the pump outlet tubing into the ascending aorta during operation of the impeller.

[0097] In some applications, a control console 21 (shown in FIG. 1A ), typically including a computer processor 25, drives the impeller to rotate. For example, the computer processor may control a motor 74 (shown in FIG. 7B ), disposed in a motor unit 23 (shown in FIG. 1A ), which drives the impeller to rotate via a drive cable 130 (shown in FIG. 12A ). In some applications, the computer processor is configured to detect physiological parameters of interest (e.g., left ventricular pressure, cardiac afterload, rate of change of left ventricular pressure, etc.) and control the rotation of the impeller accordingly, as described in more detail below. Typically, the operations described herein, performed by the computer processor, transform the physical state of memory, which is an actual physical item in communication with the computer processor, to have different magnetic polarities, charges, etc., depending on the memory technology used. The computer processor 25 is typically a hardware device programmed with computer program instructions to create a special-purpose computer. For example, when programmed to execute the techniques described herein, the computer processor 25 typically functions as a special-purpose ventricular assist computer processor and / or a special-purpose blood pump computer processor.

[0098] In some applications, a purge system 29 (shown in FIG. 1A) passes a fluid (e.g., a glucose solution) through portions of the ventricular assist device 20, for example, to cool portions of the device, to purge and / or lubricate interfaces between rotating portions and stationary bearings, and / or to flush debris from portions of the device.

[0099] Typically, a frame 34 is disposed along the distal portion 102 of the pump outlet tubing 24 and around the impeller 50 within the pump outlet tubing. The frame is typically made of a shape memory alloy, such as Nitinol. For some applications, the shape memory alloy of the frame is configured such that at least a portion of the frame (and thus the distal portion 102 of the tubing 24) assumes a generally circular, elliptical, or polygonal cross-sectional shape when no force is applied to the distal portion 102 of the tubing 24. By assuming a generally circular, elliptical, or polygonal cross-sectional shape, the frame is configured to hold the distal portion of the pump outlet tubing open. Typically, during operation of the ventricular assist device, the distal portion of the pump outlet tubing is configured to be placed within a subject's body so that it is at least partially disposed within the left ventricle.

[0100] For some applications, the frame is not disposed within the pump outlet tubing along the proximal portion 106 of the pump outlet tubing 24, and therefore the pump outlet tubing is not supported open by the frame 34. The pump outlet tubing 24 is typically made of a blood-impermeable, collapsible material to make it collapsible. For example, the pump outlet tubing 24 may include polyurethane, polyester, and / or silicone. Alternatively or additionally, the pump outlet tubing is made of polyethylene terephthalate (PET) and / or polyether block amide (e.g., PEBAX®). For some applications (not shown), the pump outlet tubing is reinforced with a reinforcing structure, e.g., a braided reinforcing structure such as a braided nitinol tubing. Typically, the proximal portion of the pump outlet tubing is configured to be positioned such that at least a portion of the pump outlet tubing is disposed within the subject's ascending aorta. For some applications, as shown in FIG. 1B , the proximal portion of the pump outlet tubing crosses the subject's aortic valve and passes from the subject's left ventricle to the subject's ascending aorta.

[0101] As described above, the pump outlet tubing typically defines one or more blood inlet openings 108 at its distal end, through which blood flows from the left ventricle into the pump outlet tubing during impeller operation. In some applications, the proximal portion of the pump outlet tubing defines one or more blood outlet openings 109, through which blood flows from the pump outlet tubing into the ascending aorta during impeller operation. Typically, the pump outlet tubing defines multiple blood outlet openings 109, e.g., two to eight blood outlet openings (e.g., two to four blood outlet openings). During impeller operation, the pressure of blood flow through the pump outlet tubing typically keeps the proximal portion of the tubing open. In some applications, the proximal portion of the pump outlet tubing is configured to collapse inward in response to pressure outside the proximal portion of the pump outlet tubing exceeding pressure inside the proximal portion of the pump outlet tubing, for example, in the event of an impeller malfunction. In this way, the proximal portion of the pump outlet tubing acts as a safety valve, preventing retrograde blood flow from the aorta into the left ventricle.

[0102] 1C, for some applications, the frame 34 is shaped to define a proximal cone portion 36, a central cylindrical portion 38, and a distal cone portion 40. Typically, the proximal cone portion faces proximally, i.e., the narrow end of the cone is oriented proximally relative to the wide end of the cone. Further, typically, the distal cone portion faces distally, i.e., the narrow end of the cone is oriented distally relative to the wide end of the cone.

[0103] For some applications, a liner 39, such as that shown in FIG. 4, lines the frame within at least a portion of the frame 34 (e.g., along all or part of the central cylindrical portion of the frame). Depending on the application, the liner partially or completely overlaps the pump outlet tube 24 in the portion of the frame that it lines, as described in more detail below with reference to FIGS. 10A-B. For other applications, the pump head does not include the liner 39, as shown in FIG. 1C.

[0104] Typically, pump outlet tube 24 includes a conical proximal section 42 and a cylindrical central section 44. The proximal conical section typically faces proximally, i.e., the narrow end of the cone is oriented proximally relative to the wide end of the cone. Typically, a blood outlet opening 109 is defined by pump outlet tube 24 such that it extends at least partially along the proximal conical section of tube 24. In some such applications, the blood outlet opening is teardrop-shaped, as shown in FIG. 1C . Typically, the teardrop-shaped feature of the blood outlet opening, combined with the fact that this opening extends at least partially along the proximal conical section of tube 24, causes blood to exit the blood outlet opening along a flow line that is substantially parallel to the longitudinal axis of tube 24 at the location of the blood outlet opening.

[0105] In some applications (not shown), the diameter of the pump outlet tubing 24 varies along the length of the central portion of the pump outlet tubing such that the central portion of the pump outlet tubing has a frusto-conical shape. For example, the central portion of the pump outlet tubing may widen from its proximal end to its distal end, or may narrow from its proximal end to its distal end. In some applications, the central portion of the pump outlet tubing has a diameter of 5-7 mm at its proximal end and a diameter of 8-12 mm at its distal end.

[0106] Referring again to FIG. 1C , the ventricular assist device typically includes a distal tip element 107 disposed distally relative to the frame 34 and including an axial shaft receiving tube 126 and a distal tip 120. Typically, the axial shaft receiving tube is configured to receive a distal portion of the pump head's axial shaft 92 ( FIG. 4 ) during axial back-and-forth movement of the axial shaft (described in more detail below) and / or during delivery of the ventricular assist device. (Typically, during delivery of the ventricular assist device, the frame is maintained in a radially constrained configuration, so that the orientation of the axial shaft relative to the frame is different from its orientation relative to the frame during operation of the ventricular assist device.) Typically, as shown in FIG. 1C , for example, the distal tip 120 is configured to assume a curved shape when deployed within the subject's left ventricle. For some applications, the curvature of the distal tip is configured to provide an atraumatic tip for the ventricular assist device 20. Alternatively or additionally, the distal tip is configured to space a blood inlet opening 108 of the ventricular assist device from the wall of the left ventricle.

[0107] As shown in the enlarged portion of FIG. 1B, in some applications, the pump outlet tube 24 extends to the end of the distal cone portion 40 of the frame, and the pump outlet tube defines multiple lateral blood inlet openings 108, as described in more detail below. In such applications, the pump outlet tube typically faces distally, i.e., defines a distal cone in which the narrow end of the cone is distal to the wide end of the cone. In some such applications (not shown), the pump outlet tube defines two to four lateral blood inlet openings (e.g., four lateral blood inlet openings). Typically, in such applications, each of the blood inlet openings defines an area greater than 20 square millimeters (e.g., greater than 30 square millimeters) and / or less than 60 square millimeters (e.g., less than 50 square millimeters), e.g., between 20 and 60 square millimeters, or between 30 and 50 square millimeters. Alternatively or additionally, the outlet tube defines a larger number of smaller lateral blood inlet openings, such as more than 10 blood inlet openings, more than 50 blood inlet openings, more than 200 blood inlet openings, or more than 400 blood inlet openings, e.g., between 50 and 100 blood inlet openings, between 100 and 400 blood inlet openings, or between 400 and 600 blood inlet openings. In some such applications, each of the blood inlet openings defines an area of ​​more than 0.05 square mm (e.g., more than 0.1 square mm) and / or less than 3 square mm (e.g., less than 1 square mm), e.g., between 0.05 and 3 square mm, or between 0.1 and 1 square mm. Alternatively, each of the blood inlet openings defines an area greater than 0.1 mm 2 (e.g., greater than 0.3 mm 2 ) and / or less than 5 mm 2 (e.g., less than 1 mm 2 ), e.g., between 0.1 and 5 mm 2 , or between 0.3 and 1 mm 2 . Such applications are described in further detail below, e.g., with reference to Figures 11A-E.

[0108] It should be noted that the lateral blood inlet opening is typically defined by the distal conical portion of the pump outlet tubing. Therefore, even blood inlet openings described as "lateral blood inlet openings" typically are not oriented completely transversely to the longitudinal axis of the pump outlet tubing. Rather, the blood inlet opening is disposed obliquely relative to the longitudinal axis of the pump outlet tubing. However, in some embodiments, the blood outlet opening is described as a "laterally oriented blood outlet opening" because, in such embodiments, the blood outlet opening is disposed transversely to the longitudinal axis of the pump outlet tubing because it is defined by the central cylindrical portion of the pump outlet tubing. It should be noted that in other embodiments, the blood outlet opening is disposed obliquely relative to the longitudinal axis of the pump outlet tubing because it is at least partially defined by the proximal conical portion of the pump outlet tubing.

[0109] In general, the scope of the present disclosure includes combining a pump outlet tube defining a single axially oriented blood inlet opening 108 as shown in FIG. 1C or a pump outlet tube defining multiple lateral blood inlet openings 108 as shown in FIG. 1B in combination with other features of the ventricular assist devices described herein, mutatis mutandis.

[0110] Reference is now made to FIG. 2, which is a schematic illustration of a frame 34 housing the impeller of a ventricular assist device 20, in accordance with some applications of the present invention. The frame 34 is typically made of a shape-memory alloy, such as Nitinol, that is shaped so that a central portion 38 of the frame (and thus the tube 24) assumes a generally circular, elliptical, or polygonal cross-sectional shape when no force is applied to the pump outlet tube 24. By assuming that generally circular, elliptical, or polygonal cross-sectional shape, the frame is configured to hold the distal portion of the tube open. (Typically, assuming that the central portion 38 of the frame has a circular cross-section, the central portion of the frame is also referred to herein as the "cylindrical portion" of the frame.)

[0111] Typically, the frame is a stent-like frame because it includes struts that define cells. Furthermore, the frame is typically covered by the pump outlet tube 24 and / or by a liner 39, described below with reference to FIGS. 10A-B. As described below, in some applications, the impeller 50 moves axially back and forth relative to the frame 34. Typically, the location of the portion of the impeller that defines the maximum span of the impeller during its movement relative to the frame is disposed within the central cylindrical portion 38 of the frame 34. In some cases, if the cells in the central cylindrical portion 38 of the frame 34 are too large, the pump outlet tube 24 and / or the liner 39 may be stretched between the edges of the cells, causing the pump outlet tube 24 and / or the liner 39 to no longer define a circular cross-section. In some applications, if this occurs in the region where the portion of the impeller defining the maximum span of the impeller is located, a substantially non-constant gap will result between the edges of the impeller blades and the tube 24 (and / or lining) at that location during the impeller's rotational cycle, which may lead to increased hemolysis compared to a substantially constant gap between the edges of the impeller blades and the tube 24 (and / or lining) at that location during the impeller's rotational cycle.

[0112] Referring to Figure 2, and at least partially in consideration of the problems described in the paragraph above, within the central cylindrical portion 38 of the frame 34, the frame defines a number of relatively small cells. Typically, when the frame is disposed in its radially unconstrained configuration, the maximum cell width CW of each cell within the cylindrical portion of the frame (i.e., the distance measured along the circumference of the cylindrical portion 38 from the inner edge of a strut at the central junction on one side of the cell to the inner edge of a strut at the central junction on the other side of the cell) is less than 2 mm, e.g., 1.4 mm to 1.6 mm, or 1.6 mm to 1.8 mm. Because the cells are relatively small, the liner 39 defines a substantially circular cross-section within the cylindrical portion of the frame.

[0113] 2, beginning at the distal end of the frame (on the right side of the figure), the frame typically defines (a) a junction 31 that couples the frame to the distal bearing housing 118H (shown in FIG. 5A) of the ventricular assist device, (b) a distal conical section 40, (c) a central cylindrical section 38, (d) a proximal conical section 36, and (e) a proximal strut junction 33. As shown, as the frame moves from the proximal end of the frame toward the center of the frame (e.g., as the frame moves from the proximal strut junction 33 through the proximal conical section 36 to the central cylindrical section 38), struts 37 of the frame pass through junction 35, where a single strut bifurcates into two struts in a Y-shape. As described in more detail below, the frame 34 typically extends axially to be disposed in a radially constrained (i.e., crimped) configuration within the delivery catheter 143. Additionally, the frame typically transmits its radial narrowing to the impeller, which is radially constrained by its axial expansion within the frame. For some applications, the struts of the frame configured as described above facilitate the transmission of axial extension from the delivery catheter (or other device configured to crimp the frame) to the frame, which in turn facilitates the transmission of axial extension to the impeller. This is because the pair of struts branching from each junction 35 are configured to rotate about the junction and move closer together to fill the space between them.

[0114] Continuing with reference to FIG. 2, during assembly of the ventricular assist device, the distal coupling 31 is first coupled to the distal bearing housing 118H (shown in FIG. 5A), for example, via a snap-fit ​​mechanism. In some applications, the proximal strut joint 33 is still held open at this stage to allow placement of the impeller within the frame through the proximal end of the frame. The frame 34 configuration shown in FIG. 2 is typically used in applications where the pump outlet tubing extends to the distal end of the frame 34 (e.g., as shown in FIG. 1B). In such cases, the distal end of the frame is covered by the pump outlet tubing 24, preventing insertion of the impeller through the distal end of the frame. During assembly of the ventricular assist device, after insertion of the impeller through the proximal end of the frame, the proximal strut joint is closed. In some applications, the proximal strut joint is closed around the outside of the proximal bearing housing 116H (shown in FIG. 5A), as described in more detail below with reference to FIGS. 5A-B. Typically, a fixation element 117 (eg, a ring as shown in FIG. 5A) holds the strut joint in its closed configuration around the outside of the proximal bearing housing 116H.

[0115] Typically, when disposed in its radially unconstrained configuration, frame 34 has an overall length greater than 25 mm (e.g., greater than 30 mm) and / or less than 50 mm (e.g., less than 45 mm), e.g., 25-50 mm, or 30-45 mm. Typically, when disposed in its radially constrained configuration (within delivery catheter 143), the length of the frame increases by 2-5 mm. Typically, when disposed in its radially unconstrained configuration, the length of the central cylindrical portion of frame 34 is greater than 10 mm (e.g., greater than 12 mm) and / or less than 25 mm (e.g., less than 20 mm), e.g., 10-25 mm, or 12-20 mm. In some applications, the ratio of the length of the central cylindrical portion of the frame to the overall length of the frame is greater than 1:4 and / or less than 1:2, e.g., 1:4 to 1:2.

[0116] Reference is now made to FIGS. 3A-E, which are schematic illustrations of an impeller 50, or a portion thereof, according to some applications of the present invention. Typically, the impeller includes at least one outer helical elongated element 52 wound around a central axial spring 54, with the helix defined by the helical elongated element being coaxial with the central axial spring. Typically, the impeller includes two or more helical elongated elements (e.g., three helical elongated elements shown in FIGS. 3A-C). For some applications, the helical elongated elements and the central axial spring are made of a shape-memory material, e.g., a shape-memory alloy such as Nitinol. Typically, each helical elongated element and the central axial spring supports a membrane 56 of material (e.g., an elastomer such as polyurethane and / or silicone) therebetween. For some applications, the membrane of material includes a piece of Nitinol embedded therein, e.g., to strengthen the membrane of material. For illustrative purposes, the impeller is shown in FIG. 3A without the material. Figures 3B and 3C are diagrams of an impeller with material supported between a helical elongate element and a spring, respectively, and Figures 3D and 3E are diagrams of an impeller similar to that shown in Figures 3B and 3C, but with some features of the impeller that differ from those shown in Figures 3B and 3C, as will be described in more detail below.

[0117] Each helical elongate element, together with a membrane extending from the helical elongate element to the spring, defines a respective impeller blade, with the helical elongate element defining the outer edge of the blade and the axial spring defining the axis of the impeller. Typically, the membrane of material extends along and covers the spring. For some applications, the helical elongate element is wrapped with suture 53 (e.g., polyester suture as shown in FIGS. 3A-C). Typically, the suture is configured to facilitate bonding between the membrane of material (typically an elastomer such as polyurethane or silicone) and the helical elongate element (typically a shape memory alloy such as Nitinol). For some applications, spring 54 is wrapped with suture (e.g., polyester suture, not shown). Typically, the suture is configured to facilitate bonding between the membrane of material (typically an elastomer such as polyurethane or silicone) and the spring (typically a shape memory alloy such as Nitinol).

[0118] Typically, the proximal ends of the spring 54 and the helical elongate element 52 extend from the impeller's proximal bushing (i.e., sleeve bearing) 64 such that the proximal ends of the spring 54 and the helical elongate element 52 are disposed at similar radial distances from the longitudinal axis of the impeller. Similarly, the distal ends of the spring 54 and the helical elongate element 52 typically extend from the impeller's distal bushing 58 such that the distal ends of the spring 54 and the helical elongate element 52 are disposed at similar radial distances from the longitudinal axis of the impeller. The helical elongate element typically rises gradually from the proximal bushing, reaches a maximum span, and then descends gradually toward the distal bushing. Typically, the helical elongate element is symmetrical along its length, such that the ascending portion of its length is symmetrical to the descending portion of its length. The impeller typically defines a lumen 62 therethrough (shown in FIG. 3C), which typically extends through and is defined by the spring 54 and the proximal and distal bushings 64, 58 of the impeller.

[0119] Reference is now made to Figure 4, which is a schematic illustration of an impeller 50 disposed inside a frame 34 of a ventricular assist device 20, in accordance with some applications of the present invention. In some applications, a liner 39 lines the frame within at least a portion of the frame 34 (e.g., along all or a portion of the central cylindrical portion 38 of the frame). Depending on the application, the liner may partially or completely overlap the pump outlet tube 24 in the portion of the frame that it lines, as described in more detail below with reference to Figures 9A-B.

[0120] As shown in FIG. 4 , even at the maximum span of the impeller, there is typically a gap G between the outer edge of the impeller blades and the liner 39. In some applications, a relatively small gap between the outer edge of the impeller blades and the liner 39 is desirable so that the impeller can efficiently pump blood from the subject's left ventricle to the subject's aorta. (Note that the relatively small gap between the outer edge of the impeller 50 and the liner 39, even at the maximum span of the impeller, and the impeller's shape, cause the impeller to function as an axial-flow impeller, pumping blood axially from the distal end of the pump outlet tubing 24 to the proximal end of the pump outlet tubing.) It is also desirable to maintain the gap between the outer edge of the impeller blades and the inner surface of the frame 34 throughout the impeller's rotation within the frame 34, for example, to reduce the risk of hemolysis.

[0121] In some applications, when both the impeller 50 and the frame 34 are disposed in a radially unconstrained configuration, and prior to operation of the impeller, the gap G between the outer edge of the impeller and the lining 39 at the location where the impeller span is at its maximum is greater than 0.05 mm (e.g., greater than 0.1 mm) and / or less than 1 mm (e.g., less than 0.4 mm), e.g., between 0.05 and 1 mm, or between 0.1 and 0.4 mm. In some applications, when the impeller is disposed in a radially unconstrained configuration, and prior to operation of the impeller, the outer diameter of the impeller at the location where the outer diameter is at its maximum is greater than 7 mm (e.g., greater than 8 mm) and / or less than 10 mm (e.g., less than 9 mm), e.g., between 7 and 10 mm, or between 8 and 9 mm. For some applications, the inner diameter of frame 34 (measured from the inside of liner 39 on one side of the frame to the inside of the liner on the opposite side of the frame) when frame 34 is disposed in its radially unconstrained configuration is greater than 7.5 mm (e.g., greater than 8.5 mm) and / or less than 10.5 mm (e.g., less than 9.5 mm), e.g., between 7.5 and 10.5 mm, or between 8.5 and 9.5 mm. For some applications, the outer diameter of frame 34 when the frame is disposed in its radially unconstrained configuration is greater than 8 mm (e.g., greater than 9 mm) and / or less than 13 mm (e.g., less than 12 mm), e.g., between 8 and 13 mm, or between 9 and 12 mm.

[0122] Typically, the axial shaft 92 passes through the axis of the impeller 50 via the impeller lumen 62. In some applications, the axial shaft is rigid, e.g., a rigid tube. In some applications, the axial shaft is made of a shape-memory material (e.g., a shape-memory alloy such as Nitinol). Typically, such materials have some elasticity, so that even if the axial shaft is bent (e.g., during delivery of the pump head into the left ventricle), the axial shaft will assume a straight shape once deployed within the subject's body.

[0123] The proximal bushing 64 is disposed on the axial shaft 92, and the distal bushing 58 is disposed on the axial shaft distal from the proximal bushing. In some applications, the impeller proximal bushing 64 is coupled to the shaft such that the axial position of the proximal bushing relative to the shaft is fixed, and the impeller distal bushing 58 is slidable relative to (i.e., slidable along) the shaft. For example, the proximal bushing may be coupled to a coupling element 65 disposed on the axial shaft (shown in FIG. 4 ), e.g., via a snap-fit ​​mechanism. Alternatively, the impeller distal bushing 58 is coupled to the shaft such that the axial position of the distal bushing relative to the shaft is fixed, and the impeller proximal bushing 64 is slidable relative to the shaft.

[0124] The axial shaft itself is radially stabilized via proximal and distal radial bearings 116, 118 (FIG. 5A). The axial shaft then passes through a lumen 62 defined by the impeller, radially stabilizing the impeller against the inner surface of the frame 34, maintaining even a relatively small gap (such as that described above) between the outer edges of the impeller blades and the inner surface of the frame 34 during impeller rotation.

[0125] 3A-C, in some applications, the impeller includes a plurality of elongated elements 67 extending radially from the central axial spring 54 to the outer helical elongated element 52. The elongated elements are typically flexible but substantially inextensible along the axis defined by the elongated elements. Furthermore, typically, each of the elongated elements is configured to exert no force on the helical elongated element unless a force acting on the impeller is acting to move the helical elongated element radially outward, such that the spacing between the helical elongated element and the central axial spring (in its absence) is greater than the length of the elongated element. For example, the elongated elements may include string (such as polyester and / or another polymer or natural material, including fiber) and / or wire (such as Nitinol wire and / or wire made of another alloy or metal).

[0126] In some applications, the elongated elements 67 maintain the helical elongated elements 52 (which define the outer edges of the impeller blades) within a given distance relative to the central axial spring. In this manner, the elongated elements are configured to prevent the outer edges of the impeller from being forced radially outward due to forces exerted on the impeller during rotation of the impeller. The elongated elements are thereby configured to maintain a gap between the outer edges of the impeller blades and the inner surface of the frame 34 during rotation of the impeller. Typically, two or more (e.g., three or more) and / or seven or fewer (e.g., three or fewer) elongated elements 67 are used in an impeller, and each of the elongated elements is typically double (i.e., extending radially from the central axial spring 54 to the outer helical elongated element 52, then back from the helical element to the central axial spring). For some applications, the multiple elongate elements, each extending from the spring to a respective helical elongate element and back to the spring, are formed from a single string or wire.

[0127] Reference is now made to FIGS. 3D and 3E, which are schematic illustrations of impeller 50 including a single, integrated impeller over-expansion prevention element 72 defining multiple elongated elements 67, according to some applications of the present invention. For some applications, impeller over-expansion prevention element 72 (defining multiple elongated elements 67) is used as an alternative to elongated elements 67 shown in FIGS. 3A-C. For some applications, element 72 defines a ring 73 and multiple elongated elements 67 extending radially from the ring. For some applications, rather than wrapping string and / or wire around spring 54, ring 73 of element 72 is disposed around (coupled to) spring 54, for example, by placing it around tube 70, typically disposed at the longitudinal center of the spring. The ends of corresponding elongated elements 67 are then coupled to corresponding helical elongated elements 52. As noted above, elongated elements 67 are typically flexible but substantially inextensible along the axis defined by the elongated elements. Further, typically, each of the elongated elements 67 is configured to provide substantially no resistance to compression. Rather, each elongated element 67 is configured to exert a tension on the helical elongated element 52 that prevents the helical elongated element 52 from moving radially outward, such that (in the absence of the elongated element 67) the spacing between the helical elongated element 52 and the central axial spring 54 is greater than the length of the elongated element 67. The impeller over-expansion prevention element is configured to prevent radial expansion of the impeller when a force that would move the helical elongated element 52 radially outward is acting on the impeller (in the absence of the elongated element 67). Typically, each elongated element 67 is disposed within one of the impeller blades and configured to prevent the impeller blade from expanding radially. For some applications, the elements 72 are made of polyester and / or another polymer or natural material, including fiber, and / or nitinol (or a similar shape memory alloy).

[0128] It should be noted that the scope of the present invention includes the use of a single integrated impeller over-expansion prevention element 72 with impellers having configurations different from those shown in Figures 3D-E. For example, a single integrated impeller over-expansion prevention element 72 can be used with impellers having an axial configuration different from that of spring 54 (but typically nevertheless defining a lumen therethrough, such as impellers defining lumen 62 therethrough). Alternatively or additionally, a single integrated impeller over-expansion prevention element 72 can be used with the impellers described below with reference to Figures 3F-G.

[0129] In some applications, the following assembly techniques are used to manufacture impellers while enhancing the bonding of the elastomeric material used to form the membrane 56 to the at least one helical elongate element. Typically, the bonding of the elastomeric material to the at least one helical elongate element is performed in a manner that does not cause the elastomeric material to protrude beyond the active edge of the impeller blade. More typically, the bonding of the elastomeric material to the at least one helical elongate element is performed in a manner that causes the elastomeric material to round the edges of the helical elongate element, thereby providing a rounded outer edge to the impeller blade. The proximal bushing 64, the distal bushing 58, and the helical elongate element 52 are cut from a tube of shape-memory material, such as Nitinol. The tube is cut and the shape-memory material is typically set so that the helical elongate element and bushing are defined by the cut and set tube of shape-memory material.

[0130] In some applications, the helical elongate element is plasma-treated before being bonded to the spring 54. Alternatively or additionally, the helical elongate element is coated with a bonding agent before being bonded to the spring 54. Typically, a bonding agent is selected having at least two functional groups configured to bond with the helical elongate element and the elastomeric material, respectively. For example, a silane compound such as n-(2-aminoethyl)-3-aminopropyltrimethoxysilane may be used, which includes a first functional group (e.g., (OH)) configured to bond with the helical elongate element (usually made of an alloy such as Nitinol) and a second functional group (e.g., (NH)) configured to bond with the elastomeric material. Typically, the functional groups of the bonding agent are only active for a limited period of time (e.g., less than about one hour). Therefore, during this period, a coating of elastomeric material is applied around the helical elongate element. Typically, the coating of elastomeric material is the same or a similar elastomeric material as used for the membrane 56. For example, a polycarbonate-based thermoplastic polyurethane such as Aromatic Carbothane™ (e.g., Aromatic Carbothane™ 75A) may be used for the membrane 56, and the coating may be the same polycarbonate-based thermoplastic polyurethane or a similar polycarbonate-based thermoplastic polyurethane such as Pellethane™ (e.g., Pellethane™ 90A).

[0131] As described above, the proximal bushing 64, the distal bushing 58, and the helical elongate element 52 are typically cut from a tube of shape-memory material, such as Nitinol. In some applications, the spring 54 is coupled to the helical elongate element 52 after a coating is applied to the helical elongate element. Typically, the spring 54 is inserted into a cut and shape-set tube, such that the spring extends along the length of the tube from at least the proximal bushing to the distal bushing. In some applications, the spring is inserted into the cut and shape-set tube while the spring is in axial compression, and the spring is configured to be held in place relative to the tube by exerting a radial force on the proximal and distal bushings. Alternatively or additionally, portions of the spring are welded to the proximal and distal bushings. In some applications, the spring is cut from a tube of shape-memory material, such as Nitinol. In some applications, the spring is configured so that when the spring is disposed in a radially unconstrained configuration (as the spring is typically disposed during operation of the impeller), there is substantially no gap between the windings of the spring and adjacent windings.

[0132] Typically, at this stage, the over-expansion prevention element 72 is placed between the spring and the helical elongate element as described above, resulting in an assembly comprising the coated helical elongate element 52, the spring 54, and the over-expansion prevention element 72.

[0133] In some applications, the coated assembly of the helical elongate element 52, spring 54, and overextension prevention element 72 is sprayed with an additional layer of elastomeric material at this stage. Typically, the sprayed elastomeric material is the same or a similar elastomeric material used as the membrane 56. For example, if a polycarbonate-based thermoplastic polyurethane such as Aromatic Carbothane™ (e.g., Aromatic Carbothane™ 75A) is used as the membrane 56, the sprayed material may be the same polycarbonate-based thermoplastic polyurethane or a similar polycarbonate-based thermoplastic polyurethane such as Pellethane™ (e.g., Pellethane™ 90A). In some applications, spraying the helical elongate element rounds the helical elongate element. Typically, if the helical elongate element has a rounded cross-section, the elastomeric material forms a layer with a substantially uniform thickness at the interface with the helical elongate element. For some applications, as described above, applying a coating of elastomeric material to the helical elongate element causes the helical elongate element to become at least partially round.

[0134] In some applications, after spraying, the coated assembly of the helical elongate element 52, spring 54, and overextension prevention element 72 is immersed in an elastomer from which the membrane 56 is made. In some applications, the material from which the membrane is made is an elastomer with an ultimate elongation greater than 300 percent, e.g., greater than 400 percent. Typically, the material has a relatively low molecular weight. In some applications, the material has a melt index (an indirect measure of molecular weight) of at least 4, e.g., at least 4.3. In some applications, the material has an ultimate tensile strength greater than 6000 psi, e.g., greater than 7000 psi, or greater than 7500 psi. In some applications, the material is a polycarbonate-based thermoplastic polyurethane, such as Carbothane™. In some applications, Aromatic Carbothane™ (e.g., Aromatic Carbothane™ 75A) is used. Typically, such materials have one or more of the following characteristics: no outer diameter loss during the dipping process, fatigue resistance, resistance to deformation due to crimping, and low outer diameter loss upon crimping. The material is then hardened, for example, by drying, so that it solidifies. At this stage, the impeller is typically disposed on a mandrel that passes through a lumen 62 defined by a bushing and spring, thereby maintaining the lumen during drying. In some applications, the impeller rotates while the membrane material dries, typically facilitating the formation of a membrane of material having a substantially uniform thickness within each impeller blade. Once the material is dry, the mandrel is typically removed from the lumen 62.

[0135] In accordance with the above description of applying the film 56 to the helical elongate element, the scope of the present disclosure includes any technique in which an additional layer of the same elastomeric material, a different elastomeric material, and / or an intermediary material is applied to the helical elongate element, whether by spraying, dipping, or a different coating method, before the helical elongate element is immersed in the elastomeric material from which the film 56 is made. In some applications, the additional layer of elastomeric material is configured to curl the helical elongate element and / or act as an intermediary to strengthen the bond between the helical elongate element and the film of material 56. In some applications, the intermediary material (such as a silane) is configured to act as an intermediary to strengthen the bond between the helical elongate element and the film of material 56.

[0136] Typically, the impeller 50 is inserted transcatheterically into the left ventricle in a radially constrained configuration. In the radially constrained configuration, both the helical elongate element 52 and the central axial spring 54 are axially stretched and radially constrained. Typically, a membrane 56 of material (e.g., silicone and / or polyurethane) changes shape to match the shape changes of the helical elongate element and axial support spring that support it. Typically, using a spring to support the inner edge of the membrane allows the membrane to change shape without breaking or collapsing because the spring provides a large surface area to which the inner edge of the membrane bonds. In some applications, for example, compared to using a rigid shaft to support the inner edge of the membrane, using a spring to support the inner edge of the membrane allows the diameter of the spring itself to be reduced by axial stretching, thereby reducing the diameter to which the impeller can be radially constrained.

[0137] As noted above, in some applications, the proximal bushing 64 of the impeller 50 is coupled to the axial shaft 92 such that the axial position of the proximal bushing relative to the shaft is fixed, and the distal bushing 58 of the impeller is slidable relative to the shaft. For example, the proximal bushing may be coupled to a coupling element 65 (shown in FIG. 4 ) disposed on the axial shaft, e.g., via a snap-fit ​​mechanism. In some applications, the distal bushing slides distally along the axial shaft, thereby axially extending the impeller, when the impeller is radially constrained for insertion into a cardiac chamber or for withdrawal from a subject's body. Alternatively (not shown), the distal bushing 58 of the impeller is coupled to the shaft such that the axial position of the distal bushing relative to the shaft is fixed, and the proximal bushing 64 of the impeller is slidable relative to the shaft. In some such applications, when the impeller is radially constrained for purposes of inserting the impeller into a cardiac ventricle or withdrawing the impeller from a subject's body, the proximal bushing slides proximally along the axial shaft, causing the impeller to extend axially. After release within the subject's body, the impeller assumes its radially unconstrained configuration (in which the impeller is normally disposed during operation), as shown in Figures 3A-E.

[0138] Reference is now made to Figures 3F and 3G, which are schematic illustrations of impeller 50, in accordance with some applications of the present invention. The impeller shown in Figures 3F and 3G is generally similar to the impeller described above with reference to Figures 3A-E, except for the following differences.

[0139] For some applications, each impeller blade includes an inner helical elongate element 52i, an outer helical elongate element 52o, and a film of material 56 extending between the inner and outer helical elongate elements. Each blade is proximally coupled to a proximal bushing 64 and distally coupled to a distal bushing 58 such that when the axial shaft 92 ( FIG. 4 ) rotates, the blade rotates, thereby pumping blood through the subject. For example, as shown in FIG. 3F , each inner helical elongate element and each outer helical elongate element may be proximally coupled to a proximal bushing and distally coupled to a distal bushing. Alternatively, only one of the helical elongate elements may be coupled to a bushing at the proximal and / or distal end of the blade, with the other helical elongate element being coupled to the previous helical elongate element. Typically, the inner helical elongate element extends between the proximal bushing 64 and the distal bushing 58 to define a radial gap 55 between the axial shaft (which may be surrounded by the central axial spring 54, as described above with reference to FIG. 4 ) and the inner helical elongate element. The radial gap 55 is open, i.e., no film of material extends between the axial shaft (or central axial spring) and the inner helical elongate element. Thus, a radial gap 55 typically exists between the central axial spring and the impeller blades. In some applications, defining a radial gap increases the efficiency with which the impeller pumps blood and / or reduces hemolysis caused by the impeller compared to a generally similar impeller that does not define such a gap.

[0140] Typically, the materials used for the impeller blades shown in Figures 3F-G are generally similar to those described above with reference to Figures 3A-E. For example, the material film may be elastomeric and / or may have Nitinol pieces embedded therein. Furthermore, the material film is typically bonded to the helical elongate elements using techniques generally similar to those described above. For example, sutures 53 (Figures 3A-C) may bond the material film to the inner and outer helical elongate elements.

[0141] In some applications, the proximal bushing 64, the distal bushing 58, the inner helical elongate element 52i, and the outer helical elongate element 52o are cut from a tube of shape memory material such as Nitinol. In some applications, the inner helical elongate element, the outer helical elongate element, and the proximal and distal bushings are all formed from a single, integral structure, e.g., a single tube of a shape memory alloy such as Nitinol. Structures are typically cut and shaped to define the aforementioned structures. Alternatively, the outer helical elongate element and the proximal and distal bushings are formed from a first structure (a single, integral structure), and the inner helical elongate element is formed from one or more additional structures coupled to the first structure. For example, the outer helical elongate element and the proximal and distal bushings may be formed from a first tube of a shape memory alloy such as Nitinol, and the inner helical elongate element may be cut and formed from a second tube of a shape memory alloy such as Nitinol. Further alternatively, the inner helical elongate element and the proximal and distal bushings are formed from a first structure (a single, unitary structure), and the outer helical elongate element is formed from one or more additional structures coupled to the first structure. For example, the inner helical elongate element and the proximal and distal bushings may be formed from a first tube of a shape memory alloy, such as Nitinol, and the outer helical elongate element may be cut and formed from a second tube of a shape memory alloy, such as Nitinol.

[0142] As shown in FIG. 3G, for some applications, the impeller also includes respective elongated elements 67 configured to couple the blades to springs 54 (extending between the proximal and distal bushings) and resist tension, thereby preventing radial expansion of the impeller. For example, elongated elements 67 may couple the blades directly to springs 54, as in FIGS. 3A-C. Alternatively, as shown in FIG. 3D, the impeller may include an impeller over-expansion prevention element 72 including elongated elements 67 coupled to ring 73, thereby coupling the blades to the springs.

[0143] Typically, in such an application as shown in Figure 3G, the elongated element 67 is coupled to the outer helical elongated element 52o. Optionally, the elongated element may wrap around the outer helical elongated element 52o and / or pass through the inner helical elongated element 52i.

[0144] Typically, for each blade, the distance D0 between the inner and outer helical elongate elements increases moving from the proximal or distal end of the blade toward the middle of the blade. For example, D0 may reach a maximum value midway between the proximal bushing 64 and the distal bushing 58 and / or at the maximum radial span of the outer helical elongate element. In some applications, the maximum value of D0 is between 1 and 3.5 mm.

[0145] Reference is now made to Figures 5A and 5B, which are schematic illustrations of the impeller 50 and frame 34 of the ventricular assist device 20 in a radially unconstrained state and a radially constrained state, respectively, in accordance with some applications of the present invention. The impeller and frame are typically disposed in a radially constrained state during transcatheter insertion of the impeller and frame into a subject's body, and in a radially unconstrained state while the impeller is operating within the subject's left ventricle. Reference is also made to Figure 5C, which is an enlarged schematic illustration of the proximal end of the frame of the ventricular assist device, in accordance with some applications of the present invention.

[0146] As shown in FIG. 5B, the frame and impeller are typically maintained in a radially constrained configuration by a delivery catheter 143. Typically, in the impeller's radially constrained configuration, the impeller has an overall length greater than 15 mm (e.g., greater than 20 mm) and / or less than 30 mm (e.g., less than 25 mm), e.g., between 15 and 30 mm, or between 20 and 25 mm. More typically, in the impeller's radially unconstrained configuration, the impeller has a length greater than 8 mm (e.g., greater than 10 mm) and / or less than 18 mm (e.g., less than 15 mm), e.g., between 8 and 18 mm, or between 10 and 15 mm. More typically, when the impeller and frame 34 are arranged in a radially constrained configuration (as shown in FIG. 5B), the impeller has an outer diameter less than 2 mm (e.g., less than 1.6 mm) and the frame has an outer diameter less than 2.5 mm (e.g., less than 2.1 mm).

[0147] As noted above, typically, the axial shaft 92 passes through the axis of the impeller 50 via the impeller lumen 62. Typically, the impeller proximal bushing 64 is coupled to the shaft via coupling element 65 such that the axial position of the proximal bushing relative to the shaft is fixed, and the impeller distal bushing 58 is slidable relative to the shaft. Alternatively, the impeller distal bushing 58 is coupled to the shaft such that the axial position of the distal bushing relative to the shaft is fixed, and the impeller proximal bushing 64 is slidable relative to the shaft.

[0148] The axial shaft itself is radially stabilized via proximal and distal radial bearings 116, 118. Typically, a proximal bearing housing 116H is disposed around and houses the proximal bearing, and a distal bearing housing 118H is disposed around and houses the distal bearing. In some such applications, the radial bearings and bearing housings are made of different materials. For example, the radial bearings may be made of a first material having a relatively high hardness, such as a ceramic (e.g., zirconia), and the bearing housings may be made of a second material, such as a metal or alloy, that can be molded to a desired shape (e.g., stainless steel, cobalt chrome, and / or nitinol).

[0149] In some applications, the axial shaft 92 is made of a metal or an alloy such as stainless steel. In some such applications, the axial shaft is covered with a ceramic sleeve 240 (e.g., a zirconia sleeve) along the region of the axial shaft that contacts either the proximal or distal bearings 116, 118 during operation of the ventricular assist device. Thus, the radial interfaces between the axial shaft and the proximal and distal bearings are ceramic-ceramic interfaces. As described in more detail herein, the impeller and axial shaft are typically configured to undergo axial back-and-forth motion during operation of the ventricular assist device. Thus, in some applications, the axial shaft is covered with a ceramic sleeve along a length greater than 5 mm, e.g., greater than 7 mm, at locations along the axial shaft corresponding to the proximal and distal bearings, respectively. In this manner, the ceramic sleeve remains in contact with the radial bearings during axial back-and-forth motion of the axial shaft.

[0150] For some applications, along each portion of the axial shaft that is covered by the ceramic sleeve, the shaft is shaped (e.g., by milling, molding, or a different forming process) to define one or more grooves or depressions 95, as shown in the cross-sectional view of Figure 5C. Alternatively or additionally (not shown), the inner surface of the ceramic sleeve is shaped to define one or more grooves or depressions. For some such applications, to bond the sleeve to the axial shaft, an adhesive is injected into the grooves or depressions, which then spreads from the grooves or depressions to the interface between the axial shaft and the sleeve.

[0151] In some applications, the proximal bearing housing 116H and the distal bearing housing 118H perform additional functions. First, regarding the proximal bearing housing described above, in some applications, the proximal strut joint 33 of the frame 34 is closed around the outside of the proximal bearing housing. In some applications, the outer surface of the proximal bearing housing defines a groove shaped to receive the proximal strut joint. For example, as shown, the proximal strut joint has a wide head, and the outer surface of the proximal bearing housing defines a groove shaped to match the wide head of the proximal strut joint. Typically, a fixation element 117 (typically comprising a ring) holds the strut joint in its closed configuration around the outside of the proximal bearing housing 116H.

[0152] In some applications, additional portions of the ventricular assist device are coupled to the proximal bearing housing. For example, in some applications, a drive cable 130 extends from outside the subject's body to the axial shaft 92 and is coupled to the axial shaft so that the axial shaft rotates with the drive cable. Typically, the drive cable rotates within a first outer tube 140, which serves as a drive cable bearing tube and extends from outside the subject's body to the proximal bearing housing. In some applications, the first outer tube is disposed within a second outer tube 142 (also referred to herein as a "delivery tube") that also extends from outside the subject's body to the proximal bearing housing. In some applications, the first outer tube 140 and / or the second outer tube 142 are coupled to the proximal bearing housing (e.g., with an adhesive). For example, the first outer tube 140 may be coupled to an inner surface of the proximal bearing housing, and the second outer tube 142 may be coupled to an outer surface of the proximal bearing housing.

[0153] Referring now to the distal bearing housing 118H, in some applications, the distal coupling portion 31 of the frame 34 is coupled to an outer surface of the distal bearing housing 118H, for example, via a snap-fit ​​mechanism. For example, the outer surface of the proximal-most portion 119 of the distal bearing housing may include a snap-fit ​​mechanism to which the distal coupling portion 31 of the frame 34 is coupled. In some applications, as shown in FIG. 5A , the distal bearing 118 is disposed within the proximal-most portion 119 of the distal bearing housing. As noted above, in some applications, the pump outlet tubing 24 extends to the distal end of the frame 34 and defines the lateral blood inlet opening 108. In some such applications, a coupling 41 (e.g., a tubular coupling) extends distally from the pump outlet tubing, and the coupling is coupled to the distal bearing housing to secure the distal end of the pump outlet tubing. For some applications, the intermediate portion 123 of the distal bearing housing defines a ridged or threaded outer surface to which the pump outlet tubing coupling portion 41 is bonded (e.g., with an adhesive). For some applications, the outer surface is ridged to enhance the bond between the distal bearing housing and the pump outlet tubing coupling portion 41. For some applications, the outer surface is threaded to enhance the bond between the distal bearing housing and the pump outlet tubing coupling portion 41 and to facilitate the application of an adhesive between the outer surface and the pump outlet tubing coupling portion 41, as described in more detail below with reference to FIG. 12B . For some applications, the distal portion 121 of the distal bearing housing is configured to reinforce the region of the distal tip element 107 (e.g., the axial shaft-receiving tube 126, or a portion thereof) into which the distal end of the shaft 92 enters. Typically, the distal tip element 107 is bonded (e.g., with an adhesive) to the outer surface of the distal portion 121 of the distal bearing housing. For some applications, at least a portion of the outer surface of the distal portion 121 of the distal bearing housing is ridged and / or threaded to enhance the connection between the distal tip element 107 and the distal bearing housing.

[0154] As noted above, the axial shaft 92 is radially stabilized via the proximal and distal radial bearings 116, 118. The axial shaft then passes through the lumen 62 defined by the impeller, thereby radially stabilizing the impeller against the inner surface of the frame 34 and the lining 39, as noted above, such that even a relatively small gap (e.g., the gap noted above) between the outer edges of the impeller blades and the lining 39 is maintained during impeller rotation. Typically, the impeller itself is not disposed directly within any radial or thrust bearings. Rather, the bearings 116 and 118 function as radial bearings for the axial shaft.

[0155] In some embodiments, the pump head 27 (or more generally the ventricular assist device 20) is configured to be disposed within a subject's body and does not include a thrust bearing configured to oppose the thrust generated by the rotation of the impeller. For some applications, one or more thrust bearings are disposed outside the subject's body (e.g., in the motor unit 23 shown in FIGS. 1A and 7A-B), and opposition to the thrust generated by the rotation of the impeller is provided solely by the thrust bearing(s) disposed outside the subject's body. For some applications, mechanical and / or magnetic elements are configured to maintain the impeller within a given range of axial position. For example, a magnet (e.g., magnet 82, described below with reference to FIG. 7B) disposed at the proximal end of the drive cable (e.g., outside the subject's body) may be configured to impart axial motion to the impeller and / or maintain the impeller within a given range of axial position.

[0156] In another embodiment, the axial shaft 92 is omitted, and instead the impeller is coupled to a distal portion of the drive cable 130, e.g., the drive cable may pass through the lumen 62 (FIG. 3E) of the impeller. In other words, the distal portion of the drive cable may function as the axial shaft. Accordingly, it should be understood that the distal portion of the drive cable, which may sometimes be referred to as the “axial shaft,” may be substituted for the axial shaft 92 throughout this description.

[0157] 5D, 5E, and 5F, which are schematic illustrations of coupling element 65, according to some applications of the present invention. As noted above, in some applications, proximal bushing 64 of impeller 50 is coupled to axial shaft 92 such that the axial position of the proximal bushing relative to the shaft is fixed, and distal bushing 58 of the impeller is slidable relative to the shaft. In some applications, the proximal bushing is coupled to the axial shaft via coupling element 65, for example, via a snap-fit ​​mechanism. Typically, the coupling element includes a first region (or "portion") 66 disposed about axial shaft 92 and a second region (or "portion") 71, which may also be disposed about axial shaft 92.

[0158] The coupling element is coupled to the proximal bushing 64 at the second region 71. This coupling may be achieved via a snap-fit ​​mechanism, as described above. For example, the second region 71 may be shaped to define one or more protrusions 19, the proximal bushing 64 may be shaped to define one or more recesses 18, and the proximal bushing may be coupled to the second region 71 by the protrusions 19 snapping into the recesses 18. Alternatively, the proximal bushing may be shaped to define the protrusions 19, the second region 71 may be shaped to define the recesses 18, and the proximal bushing may be coupled to the second region 71 by the protrusions snapping into the recesses.

[0159] The coupling element is coupled to the axial shaft 92 at the first region 66. For example, in some applications, the first region of the coupling element is welded to the shaft. In other applications, the coupling element (or at least the first region 66) is made of a shape-memory material (e.g., a shape-memory alloy such as nitinol or cobalt chromium). For example, the coupling element may include a tube of shape-memory material cut to define the first and second regions. In some such applications, at least the first region of the coupling element (or the entire coupling element) is configured to have an inner diameter smaller than the outer diameter of the axial shaft (e.g., 0.01 to 0.1 mm smaller). For example, the axial shaft may have an outer diameter of 0.9 mm, and the inner diameter of the first region of the coupling element may be 0.85 to 0.89 mm (e.g., 0.87 mm). Thus, after the first region is positioned around the axial shaft, the first region is radially constrained around the axial shaft and is thus fixed in place relative to the axial shaft. In some applications, coupling the coupling element to the axial shaft in this manner rather than by welding is desirable because the coupling element and / or the axial shaft may be weakened by heating during welding.

[0160] For some applications, the first region of the coupling element is shaped to define one or more slits 75, such as by including a tube defining slits 75. The slits 75 facilitate radial expansion of the first region so that the first region can be positioned about the axial shaft. After being positioned about the axial shaft, the first region may contract radially about the axial shaft as described above.

[0161] The slits 75 may incorporate various mechanisms to facilitate expansion of the first region 66. For example, in some embodiments, one or more of the slits 75 are open-ended slits 75o, each having an open end. The open-ended slits 75o may include one or more proximal open slits 75op, which are open at the proximal end of the first region 66, and / or one or more distal open slits 75od, which are open at the distal end of the first region. Optionally, the length L0 of each open-ended slit may be 5-40% of the length L1 of the coupling element. Instead of or in addition to the open-ended slits 75o, one or more of the slits 75 may be closed-ended slits 75c, which do not each have an open end. In some embodiments, as shown in FIGS. 5D-F, the closed-ended slits 75c alternate with the open-ended slits 75o along the periphery of the first region 66.

[0162] In manufacturing the blood pump, the first region 66 is disposed about the axial shaft 92 such that the first region is radially constrained about the axial shaft, as described above. Typically, in addition to the first region 66, a second region 71 is disposed about the axial shaft.

[0163] Typically, the coupling element is coupled to the axial shaft in the above manner without changing the temperature of the coupling element or any portion thereof. Alternatively, in some applications, the temperature of the coupling element is varied to facilitate coupling of the coupling element to the axial shaft. For example, the first region may be radially expanded (with the slits 75 facilitating radial expansion) while the temperature of the first region is below the transformation temperature of the shape memory material, and then the first region may be placed around the axial shaft while the first region is radially expanded. In other words, prior to radial expansion, the coupling element may be cooled below the transformation temperature of the shape memory material, which is typically lower than ambient temperature, which increases the flexibility of the shape memory material. The coupling element may then be placed around the axial shaft while in its expanded configuration. The coupling element is then heated above its transformation temperature, causing it to contract radially toward its configured shape. As described above, at least the first region of the coupling element (or the entire coupling element) is configured to have an inner diameter smaller (e.g., 0.01 to 0.1 mm smaller) than the outer diameter of the axial shaft. Thus, when the coupling element contracts radially, it exerts an inward radial pressure on the axial shaft, locking it in place relative to the axial shaft.

[0164] After coupling the coupling element to the axial shaft, the impeller is coupled to the axial shaft by coupling the proximal bushing 64 to the second region of the coupling element. As noted above, this coupling may be performed by a snap-fit ​​mechanism, for example, by snapping the protrusion 19 into the recess 18. Thus, when the axial shaft rotates, the blades of the impeller rotate, thereby pumping blood through the subject.

[0165] In another embodiment, the second region 71 is coupled to the distal bushing 58 (e.g., via a snap-fit ​​mechanism as described above) such that the distal bushing is fixed in position relative to the axial shaft and the proximal bushing 64 is slidable along the axial shaft.

[0166] Reference is now made to Figures 6A and 6B, which are schematic illustrations of ventricular assist device 20 at various stages in a motion cycle of ventricular assist device impeller 50 relative to ventricular assist device frame 34, in accordance with some applications of the present invention. In some applications, while the impeller rotates to pump blood through vessel 24, axial shaft 92 (to which the impeller is fixed) is driven to move the impeller axially back and forth within frame 34 by moving the axial shaft in a back and forth axial motion, as described in more detail below with reference to Figure 7A. Alternatively or additionally, the impeller and axial shaft are configured to move axially back and forth within frame 34 in response to forces acting on the impeller, without the need to actively drive the axial shaft to move in a back and forth axial motion. Typically, during a subject's cardiac cycle, the pressure differential between the left ventricle and the aorta varies from near zero during ventricular systole (hereinafter "systole") to a relatively large pressure differential (e.g., 50-70 mmHg) during ventricular diastole (hereinafter "diastole"). In some applications, the impeller is pushed distally relative to the frame 34 during diastole due to the increased pressure differential for impeller delivery during diastole (and the extensible drive cable 130), compared to the position of the impeller relative to the frame 34 during systole. Because the impeller is connected to the axial shaft, the axial shaft then moves forward. During systole, the impeller (and thus the axial shaft) returns to its systolic position. Thus, the axial back-and-forth motion of the impeller and axial shaft is passively generated, i.e., the axial shaft and impeller do not require active actuation to perform this motion. Figures 6A and 6B show the impeller and axial shaft positioned within the frame 34 during the aforementioned cycle of back-and-forth axial motion.

[0167] In some applications, by moving in an axial back-and-forth motion, the portion of the axial shaft in contact with the proximal and distal bearings 116, 118 is constantly changing. In some such applications, in this manner, other things being equal, the frictional force exerted by the bearings on the axial shaft is spread over a larger area of ​​the axial shaft than if the axial shaft were not moving relative to the bearings, thereby reducing wear on the axial shaft. Alternatively or additionally, by moving in a back-and-forth motion relative to the bearings, the axial shaft cleans the interface between the axial shaft and the bearings from residue, such as blood residue.

[0168] For some applications, as shown in FIG. 6A , at the impeller's most proximal position during its motion cycle, the proximal end of the impeller is disposed within the proximal conical section of the frame 34. For some applications, at the impeller's most distal position during its motion cycle, the distal end of the impeller is disposed within the distal end of the cylindrical section of the frame 34. Alternatively, as shown in FIG. 6B , even at the impeller's most distal position during its motion cycle, the distal end of the impeller is disposed proximal to the distal end of the cylindrical section of the frame 34. Typically, during the entire cardiac cycle, the section of the impeller with the greatest span is disposed within the cylindrical portion of the frame 34. Meanwhile, the proximal portion of the impeller is typically disposed within the proximal conical section of the frame during at least a portion of the cardiac cycle.

[0169] Referring again to Figures 6A and 6B, the distal tip element 107 is typically a single, integrated element that includes both the axial shaft receiving tube 126 and the distal tip 120. The axial shaft receiving tube is typically configured to receive the distal portion of the pump head axial shaft 92 during axial back-and-forth movement of the axial shaft (described in more detail below) and / or during delivery of the ventricular assist device. (During delivery of the ventricular assist device, the frame is typically maintained in a radially constrained configuration, typically disposing the axial shaft in a different position relative to the frame than it would be during operation of the ventricular assist device.) In some applications, the distal tip 120 is configured to be flexible and therefore non-traumatic when it comes into contact with target tissue (e.g., tissue of the left ventricle). For example, the distal tip 120, or the entire distal tip element, may be made of silicone, polyethylene terephthalate (PET), and / or polyether block amide (e.g., PEBAX®). For some applications, the distal tip defines a lumen 122 therethrough. In some such applications, during insertion of the ventricular assist device into the left ventricle, a guidewire 10 ( FIG. 1B ) is first inserted into the left ventricle, for example, according to known techniques. The distal tip of the ventricular assist device is then navigated into the left ventricle by advancing the guidewire over the guidewire with the guidewire disposed within the lumen 122. For some applications, a duckbill valve 390 (or a different type of valve) is disposed at the distal end of the lumen 122 of the distal tip 120.

[0170] Typically, during insertion of the ventricular assist device into a subject's ventricle, a delivery catheter 143 ( FIG. 5B ) is positioned over the impeller 50 and frame 34 to maintain the impeller and frame in their radially constrained configuration. For some applications, as shown in FIG. 1B , a distal tip element 107 extends distally from the delivery catheter during insertion of the delivery catheter into a subject's ventricle. For some applications, the distal tip element has a protrusion 110 near its proximal end. Referring to FIG. 5B (showing the pump head disposed within the delivery catheter 143), for some applications, during insertion of the ventricular assist device into a subject's ventricle, the delivery catheter extends to the proximal side of the protrusion, such that the delivery catheter and the protrusion form a smooth, continuous surface. The distal side of the protrusion 110 is tapered, such that the vasculature is exposed to a tapered diameter change but is not exposed to any edges resulting from an abrupt change in diameter at the interface between the delivery catheter and the distal tip element.

[0171] For some applications, distal tip element 107 defines an overall curvature similar to that of a question mark or tennis racket, defining a straight proximal portion and a bulge on one side of the longitudinal axis of the straight proximal portion. Typically, as described above, a ventricular assist device is introduced into a subject's ventricle over a guidewire. Distal tip 120 defines a lumen 122 such that the distal tip is maintained in a straight configuration during introduction of the ventricular assist device into the subject's ventricle (e.g., as shown in the left frame of FIG. 1B). For some applications, the distal tip is configured to assume its curved shape when the guidewire is removed.

[0172] 6A-B , for some applications, the axial shaft receiving tube 126 extends proximally from the distal tip 120 of the distal tip element 107. As described above, the axial shaft typically undergoes axial back-and-forth motion during operation of the impeller 50. The axial shaft receiving tube 126 defines a lumen 127 configured to receive the axial shaft when it extends beyond the distal bearing portion 118. For some applications, the axial shaft receiving tube defines a stopper 128 at its distal end, the stopper configured to prevent advancement of the axial shaft beyond the stopper. For some applications, the stopper comprises a rigid component inserted (e.g., embedded) into the distal end of the shaft receiving tube. Alternatively (not shown), the stopper comprises a shoulder between the lumen 127 of the axial shaft receiving tube and the lumen 122 of the distal tip 120.

[0173] Typically, during normal operation of the impeller, even when the drive cable 130 (shown in FIG. 5A ) is fully extended (e.g., during diastole), the axial shaft does not contact the stopper 128. However, the stopper 128 is configured to prevent the axial shaft from protruding into the tip when the delivery catheter is advanced through the impeller 50 and frame 34 during retraction of the ventricular assist device 20 from the subject's ventricle. In some cases, the drive cable is at risk of breaking during advancement of the delivery catheter through the frame and impeller. In such cases, without the stopper 128, the axial shaft could protrude into the tip. Even if the drive cable were to break, the stopper 128 prevents this from happening.

[0174] Note that at the proximal end of the frame 34, the proximal radial bearing 116 also functions as a stop by preventing the coupling element 65 and / or the proximal bushing 64 of the impeller 50 from being able to move beyond the proximal radial bearing. Typically, the coupling element 65 and the proximal bushing 64 do not contact the proximal radial bearing 116 during normal operation of the impeller. However, the proximal radial bearing 116 is configured to prevent the coupling element 65 and / or the proximal bushing 64 of the impeller 50 from moving proximally from within the frame, for example, when the impeller and frame are held in a radially constrained (i.e., crimped) configuration within the delivery catheter 143. Typically, the coupling element and / or the proximal bushing extends proximally to prevent the central region of the impeller (where the impeller span is greatest) from sliding proximally into the proximal cone of the frame 34. For example, during the systolic phase of the impeller's motion cycle (shown in FIG. 6A ), if the impeller slides proximally beyond a given amount, the coupling element will contact the proximal radial bearing 116, thereby preventing further proximal movement of the impeller. In some applications, the coupling element and / or the proximal bushing extend proximally to have an overall length greater than 1.5 mm, e.g., greater than 4 mm. In some applications (not shown), a separate stop element is disposed on the axial shaft proximal to the coupling element and / or proximal bushing 64. Typically, the stop is configured as described with respect to the coupling element. That is, if the impeller slides proximally beyond a given amount, the stop element will contact the proximal radial bearing 116, thereby preventing further proximal movement of the impeller.

[0175] Typically, the impeller is disposed relatively close to the distal tip during operation of the ventricular assist device and throughout the impeller's axial back-and-forth cycle of motion. For example, the distance to the impeller's distal tip may be within the most distal 50 percent, e.g., the most distal 30 percent (or the most distal 20 percent) of the tube 24 throughout the impeller's axial back-and-forth cycle of motion.

[0176] Reference is now made to Figures 6C and 6D, which are schematic illustrations of a ventricular assist device including a motion damping spring 68, according to some applications of the present invention. As will be described in more detail below, the impeller typically undergoes axial back-and-forth motion during operation of the ventricular assist device (i.e., when the impeller is rotating). In some applications, the motion damping spring is configured to act as a shock absorber to provide damping to the motion as the impeller undergoes axial back-and-forth motion. Figure 6C illustrates the impeller during the systolic phase of its motion cycle, and Figure 6D illustrates the impeller during the diastolic phase of its motion cycle. As shown, the motion damping spring is further compressed as the impeller moves distally from its systolic position to its diastolic position. In some applications, the impeller is configured to be radially constrained (i.e., crimped) by axial stretching, and the motion damping spring is configured to be compressed to correspond to the axial stretch of the impeller. Normally, when the impeller is in a radially constrained configuration, during insertion of the pump head into the left ventricle, the impeller expands axially such that the distal end of the impeller is disposed further distally within the frame 34 and the spring is further compressed relative to the impeller and spring configuration shown in FIG. 6D.

[0177] Typically, the motion damping spring is disposed around the axial shaft 92 between the distal end of the impeller (e.g., the impeller distal bushing 58) and the distal bearing 118. In some applications, the motion damping spring is coupled to the distal bearing 118 or the distal bearing housing 118H and extends proximally on the axial shaft 92 from the distal bearing or the distal bearing housing 118H. Typically, in such cases, the motion damping spring remains rotationally stationary as the impeller rotates, and the impeller is configured to rotate relative to the motion damping spring. Alternatively or additionally, the motion damping spring is coupled to the distal end of the impeller (e.g., the impeller distal bushing 58) and / or extends distally on the axial shaft 92 from the distal end of the impeller (e.g., the impeller distal bushing 58). In some such applications, the motion damping spring is configured to rotate with the impeller. Alternatively, the motion damping spring extends from a radial bearing disposed around the distal end of the impeller (e.g., the impeller's distal bushing 58), such that the motion damping spring remains rotationally stationary as the impeller rotates, while the impeller is configured to rotate relative to the motion damping spring.

[0178] For some applications, the motion damping spring is coupled to an elastomeric material 69 (such as polyurethane and / or silicone) such that at least a portion of the axial shaft 92 between the distal end of the impeller and the distal radial bearing is covered with the elastomeric material. For some applications, coupling the elastomeric material to the spring reduces the risk of the spring causing thrombus and / or hemolysis compared to if the spring were not coupled to the elastomeric material. However, the scope of this disclosure includes providing a motion damping spring in the absence of an elastomeric material, which may be desirable in some cases.

[0179] 6C and 6D show a spring coated with an elastomeric material that extends between adjacent windings of the spring. Alternatively, the spring is embedded in the elastomeric material. Typically, the elastomeric material is generally similar to the elastomeric material used for the film of material 56 in the impeller 50. Furthermore, the elastomeric material is typically coupled to the motion damper spring in a manner generally similar to that described above with respect to coupling the film of elastomeric material to the spring of the impeller. Typically, the elastomeric material is coupled to the motion damper spring such that the elastomeric material changes shape (e.g., by stretching and compressing) to match the shape changes the motion damper spring undergoes (e.g., as the motion damper spring stretches and compresses). Furthermore, the elastomeric material is typically configured to undergo these shape changes without breaking or collapsing or without crumpling when the spring is compressed.

[0180] Typically, a purge fluid is pumped between the first outer tube 140 and the second outer tube 142. Typically, within the pump head, a portion of the purge fluid flows within a lumen defined by the axial shaft 92 and then exits the axial shaft near the distal bearing 118 to purge the interface between the axial shaft and the distal bearing. In some applications, the purge system is configured to flow the purge fluid from the distal bearing in a proximal direction along the interface between the axial shaft and the elastomeric material. In this manner, the interface between the axial shaft and the elastomeric material is purged and / or lubricated.

[0181] In some applications (not shown), a proximal motion damping spring is disposed proximal to the impeller. In some such applications, the proximal motion damping spring is disposed around the axial shaft 92 between the proximal end of the impeller (e.g., the impeller's proximal bushing 64) and the proximal bearing 116. In some applications, the proximal motion damping spring is coupled to the proximal bearing 116 or the proximal bearing housing 116H and extends distally from the proximal bearing or the proximal bearing housing on the axial shaft 92. Typically, in such cases, the proximal motion damping spring is configured to remain rotationally stationary as the impeller rotates, and the impeller rotates relative to the motion damping spring. Alternatively or additionally, the proximal motion damping spring is coupled to the proximal end of the impeller (e.g., impeller proximal bushing 64) and / or extends distally on axial shaft 92 from the proximal end of the impeller (e.g., impeller proximal bushing 64). In some such applications, the motion damping spring is configured to rotate with the impeller. Alternatively, the proximal motion damping spring extends from a radial bearing disposed around the proximal end of the impeller (e.g., impeller proximal bushing 64), such that the motion damping spring remains rotationally stationary as the impeller rotates, and the impeller is configured to rotate relative to the motion damping spring.

[0182] In some applications, the pump head includes both a proximal motion damping spring disposed proximal to the impeller and a distal motion damping spring disposed distal to the impeller, such that axial movement of the impeller in the distal or proximal direction is damped by these motion damping springs.

[0183] Reference is now made to Figures 7A-D, which are schematic illustrations of the motor unit 23 and / or the driven magnet unit 310 of the ventricular assist device 20, according to some applications of the present invention. Figure 7A shows a perspective view of the motor unit and the driven magnet unit, Figure 7B shows an exploded view of the motor unit and the driven magnet unit, Figure 7C shows a cross-sectional view of the driven magnet unit, and Figure 7D shows a perspective view of the driven magnet unit.

[0184] 7B, motor unit 23 typically includes motor 74 configured to provide rotational motion to impeller 50 via drive cable 130. For some applications, motor unit 23 includes ribs 90 configured to dissipate heat generated by the motor. For some applications, motor unit 23 includes vibration damping portions 94 and 96 configured to damp vibrations of the motor unit caused by rotational and / or back-and-forth axial motion of components of the ventricular assist device.

[0185] Typically, the motor is magnetically coupled to the drive cable. In some applications, the motor is magnetically coupled to the drive cable as shown in FIG. 7B. As shown in the cross-sectional frame of FIG. 7B, a drive magnet set (or "drive magnet") 77 is coupled to the motor via a drive magnet housing 78. In some applications, the drive magnet housing includes a ring (as shown), and the drive magnet is bonded to the inner surface of the ring. In some applications, a spacer 85 is bonded to the inner surface of the drive magnet housing between the two drive magnets, as shown. A driven magnet 82 is disposed between the drive magnets such that there is axial overlap between the drive magnet and the driven magnet. The driven magnet is coupled to a pin 131 that extends beyond the distal end of the driven magnet 82, and the pin is coupled to the proximal end of the drive cable 130, as shown in FIG. 7C. For example, the driven magnet may be cylindrical and define a hole therethrough, and the pin 131 may be bonded to the inner surface of the driven magnet that defines the hole. For some applications, the driven magnet is cylindrical and includes a north pole and a south pole that are separated from one another along the length of the cylinder as shown. For some applications, the driven magnet is housed within cylindrical housing 87. Typically, pin 131 defines a lumen 133 that includes a portion of a continuous lumen that extends through the ventricular assist device, as described in more detail below.

[0186] Note that in the application shown in Figure 7B, the drive magnet is disposed outside the driven magnet. However, the scope of this application includes, mutatis mutandis, reversing the configuration of the drive magnet and driven magnet. For example, the proximal end of the drive cable may be coupled to two or more driven magnets disposed around the drive magnet such that there is axial overlap between the driven magnets.

[0187] Typically, the magnet 82 and pin 131 are held in an axially fixed position within the motor unit 23. In some applications, the driven magnet unit 310 includes snap-fit ​​prongs 91 (shown in FIG. 7C) through which the magnetic coupling unit is reversibly coupled to the motor unit 23, and the magnetic force between the drive magnet and driven magnet holds the drive magnet in a relatively fixed axial position.

[0188] Referring now to FIG. 7C , in some applications, pin 131 is disposed within radial bearing 96, which supports the pin as it rotates. Typically, the pin is coupled at its distal end to the proximal end of drive cable 130 (e.g., using the coupling techniques described below with reference to FIGS. 14A-H ). Thus, the proximal end of the drive cable is typically held in an axially fixed position by the pin. Typically, drive cable 130 extends from pin 131 to axial shaft 92 (disposed within pump head 27), thereby at least partially fixing the axial position of the axial shaft, and thus impeller 50. (Alternatively, as described above, the distal end of drive cable 130 may function as the axial shaft.) In some applications, the drive cable is somewhat flexible. For example, the drive cable may be made of a flexible coiled wire. In some applications, the device does not include a thrust bearing at or near the pump head. In some applications, the drive cable typically allows the axial shaft (and therefore the impeller) to assume a range of axial positions (by allowing the drive cable to stretch somewhat), but restricts the axial movement of the axial shaft and impeller within a specific range of motion (by holding the proximal end of the drive cable in an axially fixed position and by limiting the stretchability of the drive cable).

[0189] 7C, typically, the drive cable rotates within a first outer tube 140 that serves as a drive cable bearing tube and extends from the driven magnet unit 310 (disposed outside the subject's body) to the pump head 27 (e.g., to the pump head's proximal bearing housing 116H). In some applications, the first outer tube is disposed within a second outer tube 142 that also extends from the driven magnet unit 310 (disposed outside the subject's body) to the pump head 27 (e.g., to the pump head's proximal bearing housing 116H).

[0190] 7B, it should be noted that motor 74 is typically mechanically coupled to and configured to rotate drive magnet 77. Idler magnet 82 axially overlaps drive magnet 77 such that when the motor rotates the drive magnet, the Idler magnet rotates. Drive cable 130 is coupled to Idler magnet 82 (e.g., via pin 131) such that as the Idler magnet rotates, the impeller pumps the subject's blood through the subject's body while the axial position of the impeller, and therefore the Idler magnet, changes with the subject's cardiac cycle.

[0191] For some applications, ventricular assist device 20 includes a magnetic sensor 84 configured to detect changes in the magnetic field caused by changes in the axial position of the driven magnet. For example, magnetic sensor 84 may include a magnetometer (e.g., a Hall sensor) disposed within motor unit 23, as shown in FIG. 7B. (In some cases, sensor 84 is referred to herein as magnetometer 84.)

[0192] Reference is now made to Figure 7E, which is a schematic illustration of motor unit 23, in accordance with some applications of the present invention, and Figure 7F, which shows a cross-sectional view of a portion of motor unit 23, in accordance with some applications of the present invention.

[0193] In some applications, the printed circuit board 104 is disposed within a protective enclosure 105. In some applications, the magnetometer 84 is contained within a magnetometer housing 112 that orients the magnetometer at the interface between the drive magnet 77 and the driven magnet 82 to facilitate detection of changes in magnetic flux density and / or magnetic phase by the magnetometer. In some applications, the magnetometer is disposed behind a metal element 113 that is shaped to act as a passive magnetic lens by directing changes in magnetic flux and magnetic phase generated at the interface between the drive magnet and the driven magnet to the magnetometer.

[0194] Referring now to FIG. 7D , a ventricular assist device is typically delivered to a subject's ventricle via a delivery catheter 143. In some applications, the proximal end of the delivery catheter is sealingly coupled to a driven magnet unit 310 via an annular mating mechanism 101. A sterile sleeve 100 typically extends proximally from the annular mating mechanism, thereby enabling relative movement between the driven magnet unit and the proximal end of the delivery catheter while maintaining sterility. In some applications, a fixation unit 97 is configured to reversibly fix the position of the driven magnet unit relative to the proximal end of the delivery catheter. For example, once the pump head is positioned within the patient's ventricle, the fixation unit may be used to fix the position of the driven magnet unit relative to the proximal end of the delivery catheter. In some applications, the fixation unit is configured such that the position of the driven magnet unit is fixed relative to the proximal end of the delivery catheter by threading a portion of the fixation unit. For example, the fixation unit may include a Tuohy Borst adapter.

[0195] Referring again to FIG. 7C , in some applications, an additional sheath 98 covers the second outer tube 142 within at least a portion of the sterile sleeve 100. In some applications, the driven magnet housing 87 defines a valve 99 at its proximal end. Typically, the guidewire 10 (shown in FIG. 1B ) exits the proximal end of the ventricular assist device through the valve 99. Typically, the ventricular assist device is delivered to the subject's ventricle over the guidewire, as described above. Further typically, once the pump head is deployed within the ventricle, the guidewire is retracted from the proximal end of the device through the valve 99. After removal of the guidewire, the driven magnet unit is typically coupled to the motor unit 23.

[0196] As noted above, a purge system 29 (shown in FIG. 1A ) is typically used in conjunction with the ventricular assist device 20. The driven magnet unit 310 typically includes an inlet port 86 and an outlet port 88 for use with the purge system. In some applications, a purge fluid is continuously or periodically pumped into the ventricular assist device via the inlet port 86 and out of the ventricular assist device via the outlet port 88. In some applications, an additional purge fluid inlet port 89 ( FIG. 7D ) is provided for pumping fluid between the delivery catheter 143 and the outer tube 142.

[0197] Reference is now made to FIG. 8A, which is a graph showing experimentally measured changes in the length of a ventricular assist device's drive cable as a function of varying pressure gradients relative to the device's impeller. Using the impeller and drive cable described herein, a glycerin-based solution was pumped into a chamber configured to replicate the left ventricle and aorta, with the solution having properties similar to those of blood (e.g., density and viscosity). The pressure gradient relative to the impeller was varied pulsatilely to represent the pulsating pressure gradient relative to normal pumping when the impeller is pumping blood from the left ventricle to the aorta. Simultaneously, images of the drive cable's movement were captured, and the change in drive cable length was determined by analysis of these images. The graph shown in FIG. 8A illustrates the measured change in drive cable length as a function of pressure gradient. As shown in FIG. 8A, as the pressure gradient relative to the impeller increased, the drive cable gradually stretched. 8A, and as described above, the impeller typically moves back and forth relative to the frame 34 in response to changes in pressure against which the impeller pumps blood (e.g., the pressure difference between the left ventricle and the aorta). The movement of the impeller, in turn, causes some elongation of the drive cable 130.

[0198] For some applications, during operation of the ventricular assist device, computer processor 25 of control console 21 ( FIG. 1A ) is configured to measure an indicator of pressure exerted on the impeller (indicative of the pressure difference between the left ventricle and the aorta) by measuring an indicator of tension in drive cable 130 and / or axial movement of the drive cable. For some applications, based on the measured indicators, the computer processor detects events in the subject's cardiac cycle, determines the subject's left ventricular pressure, and / or determines the subject's cardiac afterload. For some applications, the computer processor controls rotation of the impeller and / or corresponding back and forth axial movement of the axial shaft.

[0199] In some applications, the driven magnets are held in place relative to the drive magnet(s) via a magnetic coupling rather than a rigid mechanical coupling, so that axial back-and-forth movement of the impeller does indeed cause measurable back-and-forth movement of the inner driven magnet 82 relative to the outer drive magnet(s) 77 (FIG. 7B). It should be noted that the axial movement of the magnets is substantially smaller than the axial movement of the impeller because the full range of motion of the impeller is typically not transmitted along the length of the drive cable (the drive cable is typically somewhat flexible). In some applications, a magnetometer measures the change in the magnetic field generated by one of the magnets to measure the axial movement of the drive cable 130 and then determine the pressure on the impeller pumping. For example, the inner driven magnet 82 may be axially longer than the outer drive magnet 77. Because the inner magnet is longer than the outer magnet, there are magnetic field lines emanating from the inner magnet that do not reach the outer magnet, and the magnetic flux generated by these lines, as measured by the magnetometer, changes as the drive cable, and therefore the inner magnet, moves axially. During operation, motor 74 rotates, generating an AC signal at the magnetometer, typically having a frequency between 200 Hz and 800 Hz. As the tension in the drive cable changes, typically with the subject's cardiac cycle, a low-frequency envelope appears in the signal measured by the magnetometer, typically having a frequency between 0.5 and 2 Hz. In some applications, a computer processor measures the low-frequency envelope and derives the subject's cardiac cycle from the measured envelope.

[0200] In some applications, the magnetometer measurements are first calibrated so that the change in magnetic flux per unit change in pressure relative to impeller pumping (i.e., per unit change in pressure difference between the left ventricle and the aorta, or per unit change in pressure gradient) is known. In most subjects, it is known that the left ventricular pressure is equal to the aortic pressure during systole. Therefore, in some applications, the subject's aortic pressure is measured, and the subject's left ventricular pressure at a given time is then calculated by a computer processor based on (a) the measured aortic pressure and (b) the difference between the magnetic flux measured by the magnetometer at that time and the magnetic flux measured by the magnetometer during systole (when the left ventricle pressure is assumed to be equal to the aortic pressure). For example, as described in more detail below with reference to FIG. 12A , the subject's aortic pressure may be measured by measuring the pressure within a channel 224 defined by the delivery catheter 143. In some applications, the above techniques are used to determine alternative or additional physiological parameters. For example, events in the subject's cardiac cycle and / or the subject's cardiac afterload may be determined.

[0201] In some applications, techniques generally similar to those described in the paragraph above are used, but instead of or in addition to utilizing magnetometer measurements, another parameter is measured to determine left ventricular blood pressure (and / or another physiological parameter, such as an event in the subject's cardiac cycle and / or the subject's cardiac afterload) at a given time. For example, it is true that there is typically a relationship between the amount of power (and / or current) required to power impeller rotation at a given rotational speed and the pressure difference generated by the impeller. (Note that a portion of the pressure difference generated by the impeller is used to overcome the pressure gradient against which the impeller pushes, and also to actively pump blood from the left ventricle into the aorta by creating a positive pressure difference between the left ventricle and the aorta. Furthermore, the relationship between the above-mentioned components typically changes during the cardiac cycle.) In some applications, calibration measurements are performed so that the relationship between (a) the power (and / or current) consumption by the motor required to rotate the impeller at a given rotational speed and (b) the pressure difference generated by the impeller is known. In some applications, the subject's aortic pressure is measured, and the subject's left ventricular pressure at a given time point is then calculated by a computer processor based on (a) the measured aortic pressure, (b) the power (and / or current) consumption by the motor required to rotate the impeller at a given rotational speed at that time, and (c) a predetermined relationship between the power (and / or current) consumption by the motor required to rotate the impeller at a given rotational speed and the pressure difference generated by the impeller. In some applications, the above technique is performed while maintaining the impeller rotational speed at a constant speed. Alternatively or additionally, the impeller rotational speed is varied, and the change in impeller rotational speed is taken into account in the above calculation. In some applications, the above technique is used to determine alternative or additional physiological parameters. For example, events in the subject's cardiac cycle and / or the subject's cardiac afterload may be determined.

[0202] Typically, the tube 24 has a known cross-sectional area (when the tube is open for blood flow therethrough). For some applications, the flow through the tube 24 generated by the impeller is determined based on the determined pressure differential generated by the impeller and the known cross-sectional area of ​​the tube. For some applications, such flow rate calculations incorporate calibration parameters to account for factors such as flow resistance inherent in the ventricular assist device (or type of ventricular assist device) performing the calculation. For some applications, a ventricular pressure-volume loop is derived based on the determined ventricular pressure.

[0203] In some applications, the computer processor determines one or more physiological parameters of the subject based on data received via the ventricular assist device. Typically, the following parameters are sensed via the ventricular assist device: arterial pressure (AP), current consumption by the motor (I), and revolutions per minute (RPM) of the impeller. In some applications, left ventricular pressure (LVP), left ventricular end-diastolic pressure (LVEDP), and / or pump flow are obtained.

[0204] As noted above, in some applications, the pressure difference (dP) between the left ventricle and the aorta is obtained based on the current consumption by the motor (I) and the revolutions per minute (RPM) of the impeller. The left ventricular pressure (LVP) is obtained by subtracting the pressure difference (dP) from the arterial pressure (AP). The left ventricular end-diastolic pressure (LVEDP) is then obtained by analyzing the LVP curve, and the pump flow rate (together with the device's empirically determined pump performance parameters) is obtained by integrating the pressure difference over time.

[0205] In some applications, the dP curve is obtained by determining real-time values ​​of (a) the maximum dP within a given first current period (e.g., within the last second, within the last 0.5 seconds, or within a different period, typically between 0.1 and 2 seconds, i.e., at a first frequency of 0.5 Hz to 2 Hz), (b) the minimum dP within a given first current period (e.g., within the last second, within the last 0.5 seconds, or within a different period, typically between 0.1 and 2 seconds, i.e., at a first frequency of 0.5 Hz to 2 Hz), and (c) the dP within a given second current period (e.g., within the current 1 / 100th of a second, or within a different period, typically between the current 1 / 50th of a second and the current 1 / 200th of a second, i.e., at a second frequency of 50 Hz to 200 Hz). Typically, the second period is smaller than the first period, i.e., the second frequency is greater than the first frequency.

[0206] Typically, each of the values ​​(a), (b), and (c) is obtained using a linear model. More typically, within the first current period, the real-time value of dP (detected at the second frequency) is corrected based on the maximum dP and minimum dP (detected at the first frequency) to generate a corrected dP curve. The LVP curve is then obtained from the corrected dP curve. This typically results in a more accurate LVP value than if uncorrected real-time values ​​of dP were used.

[0207] Referring again to FIG. 7B , in some applications, in addition to magnetometer 84 configured to measure the magnetic flux density generated by the driven magnet, a second magnetometer 84A (e.g., a second Hall sensor) measures an indication of the magnetic flux density generated by the drive magnet. In some applications, a motor directly drives the drive magnet to rotate, and therefore the second magnetometer measures the motor's magnetic flux density, which is indicative of the drive magnet's magnetic flux density period. Typically, a torque is generated on the impeller as it rotates to pump blood. Furthermore, the magnitude of the torque typically depends on various parameters, such as the flow generated by the impeller, the impeller's rotational speed, and / or the pressure gradient against which the impeller pumps. In some applications, the driven magnet is held in place relative to the drive magnet via a magnetic coupling rather than a rigid mechanical coupling, so that the torque generated on the impeller actually produces a measurable torque on the inner driven magnet 82 relative to the outer drive magnet 77. It should be noted that the torque generated on the driven magnet is substantially less than that generated on the impeller because the torque generated on the impeller is not typically transmitted along the length of the drive cable, although it is true that the torque generated on the impeller is typically transmitted at least in part to the driven magnet via the drive cable.

[0208] Torque transmitted to the driven magnet typically induces a phase difference between the signal measured by magnetometer 84 (which measures the magnetic flux density of the driven magnet) and the signal measured by second magnetometer 84A (which measures the magnetic flux density of the motor and / or drive magnet). In some applications, as the torque of the impeller changes, the phase difference between the signal measured by magnetometer 84 and the signal measured by second magnetometer 84A changes. In some applications, a computer processor detects the change in this phase difference and determines a physiological parameter of the subject, at least in part, accordingly. For example, based at least in part on the change in phase difference, the computer processor may determine the difference between the subject's left ventricular pressure and the subject's aortic pressure, the subject's left ventricular pressure, an event in the subject's cardiac cycle, the subject's cardiac afterload, and / or another physiological parameter. In some applications, the techniques described in this paragraph are used in place of the above techniques for determining physiological parameters using magnetic flux density measurements and / or power consumption measurements. Alternatively, two or more of these techniques are used in combination with each other. For example, a subject's physiological parameter may be determined based on a mathematical model incorporating two or more measurements, and / or one of these techniques may be used to validate an estimate of a subject's physiological parameter made using another of these techniques.

[0209] Reference is now made to Figures 8B and 8C, which are graphs demonstrating the correlation between the phase difference signal and the pressure gradient for delivery by impeller 50, in accordance with some applications of the present invention.

[0210] The graph shown in FIG. 8B shows experimental results in which a ventricular assist device described herein was used to pump blood against various pressure gradients in a static in vitro system (i.e., an in vitro system in which the pressure gradient was constant when each measurement was taken). A linear regression model was used to estimate the pressure gradient relative to impeller pumping based on a combination of the phase difference signal, the magnetic flux amplitude signal, and the current consumed by the motor. The graph shown in FIG. 8B shows the estimated pressure gradient relative to the measured pressure gradient. As can be seen, the linear regression model incorporating the phase difference measurement provides a reliable method for estimating the pressure gradient relative to impeller pumping.

[0211] The graph shown in FIG. 8C illustrates experimental results in which a ventricular assist device described herein was used to pump blood against various pressure gradients in a pulsatile in vitro system (i.e., an in vitro system in which the pressure gradient varied pulsatilely). A space state model was used to estimate the pressure gradient relative to impeller pumping based on a combination of the phase difference signal, the magnetic flux amplitude signal, and the current consumed by the motor. The graph shown in FIG. 8C shows the estimated pressure gradient superimposed on the measured pressure gradient. As can be seen, the space state model incorporating the phase difference measurement provides a reliable method for estimating the pressure gradient relative to impeller pumping.

[0212] In accordance with the above, and in accordance with some applications of the present invention, a magnetic phase difference between one or more driven magnets and one or more drive magnets is measured, and a physiological parameter of the subject is determined, at least in part, in response thereto. For example, based at least in part on changes in the phase difference, a computer processor may determine the difference between the subject's left ventricular pressure and the subject's aortic pressure, the subject's left ventricular pressure, an event in the subject's cardiac cycle, the subject's cardiac afterload, and / or another physiological parameter. In some applications, the physiological parameter is determined based on a combination of the phase difference measurement and one or more additional measurements, such as a magnetic flux amplitude measurement, power consumed by the motor, and / or current consumed by the motor. Typically, such measurements are integrated into a mathematical model, such as a linear regression model and / or a space state model.

[0213] Reference is now made to Figures 9A and 9B, which are schematic illustrations of a ventricular assist device including one or more blood pressure measurement tubes 222 and / or fibers 228, in accordance with some applications of the present invention.

[0214] FIG. 9A is a schematic diagram of a ventricular assist device including one or more blood pressure measurement tubes 222, according to some applications of the present invention. As described above, a ventricular assist device typically includes a pump outlet tube 24 that crosses a subject's aortic valve, such that a proximal end of the tube is disposed within the subject's aorta and a distal end of the tube is disposed within the subject's left ventricle. A blood pump (typically including an impeller 50) is typically disposed within the tube 24 within the subject's left ventricle and configured to pump blood from the left ventricle to the subject's aorta via the tube 24. In some applications, the ventricular blood pressure measurement tube 222 extends at least to an outer surface 213 of the tube 24, such that an opening 214 at the distal end of the blood pressure measurement tube is configured to be in direct fluid communication with the patient's blood flow outside the tube 24. Typically, the opening 214 is configured to be proximal to the blood pump (e.g., proximal to the impeller 50) within the subject's left ventricle. A pressure sensor 216 (schematically shown in FIG. 1A) measures the pressure of the blood within the ventricular blood pressure measurement tube. Typically, the pressure sensor measures the subject's blood pressure (i.e., left ventricular blood pressure) outside of tubing 24 by measuring the pressure of blood in the left ventricular blood pressure measurement tubing. Typically, blood pressure measurement tubing 222 extends from outside the subject's body to an opening 214 at the distal end of tubing 222, and pressure sensor 216 is disposed near the proximal end of tubing 222, e.g., outside the subject's body. In some applications, computer processor 25 (FIG. 1A) receives an indication of the measured blood pressure and controls the pumping of blood by the impeller in response to the measured blood pressure.

[0215] For some applications, the ventricular assist device includes two or more such ventricular blood pressure measurement tubes 222, as shown, for example, in FIG. 9A . For some applications, based on the blood pressure measured within each left ventricular blood pressure measurement tube, computer processor 25 determines whether the opening of one of the two or more ventricular blood pressure measurement tubes is occluded. This may occur, for example, due to the opening contacting the wall of the interventricular septum and / or a portion within a different ventricle. Typically, in response to determining that one opening of the two or more ventricular blood pressure measurement tubes is occluded, the computer processor determines the subject's left ventricular pressure based on the blood pressure measured within another of the two or more ventricular blood pressure measurement tubes.

[0216] For some applications, second outer tube 142 defines a groove 215 in a portion of its outer surface that is configured to be disposed within tube 24. Typically, during insertion of the ventricular assist device into a subject's body, the portion of ventricular blood pressure measurement tubing 222 that extends from within tube 24 to at least the outer surface of tube 24 is disposed within the groove, and is configured so that this portion of the ventricular blood pressure measurement tubing does not protrude from the outer surface of the outer tube.

[0217] In some applications (not shown), the distal portion of the blood pressure measurement tubing 222 is disposed outside of the pump outlet tubing 24. For example, the blood pressure measurement tubing 222 may extend from the outer tube 142 to the proximal end of the pump outlet tubing 24, and then the blood pressure measurement tubing may be integrated into the exterior of the pump outlet tubing 24, as shown, for example, in FIG. 16D of U.S. Pat. No. 10,881,770 to Tuval, which is incorporated herein by reference.

[0218] As noted above, in some applications, the drive cable 130 extends from a motor external to the subject's body to the axial shaft 92 on which the impeller 50 is disposed. Typically, the drive cable is disposed within the first and second outer tubes 140 and 142, as described above. In some applications, as shown in the cross-sectional view of FIG. 9A , the proximal portion of the blood pressure measurement tubing 222 includes a channel between the first and second outer tubes 140 and 142. It should be noted that in this regard, the blood pressure measurement tubing refers to a continuous lumen extending from the pressure sensor 216 to the outside of the pump outlet tubing 24 within the subject's left ventricle, regardless of whether there are changes in the lumen's configuration along its length. As noted above, a purge fluid is also typically delivered between the outer tubes 140 and 142, and in some applications, the purge fluid is delivered via a purge fluid channel 226. 9A , the blood pressure measurement tubing 222 typically occupies a larger portion of the cross-sectional area defined between the first outer tube 140 and the second outer tube 142 than the purge fluid channel 226. For example, the ratio of (a) the cross-sectional area defined between the first outer tube 140 and the second outer tube 142 occupied by the blood pressure measurement tubing 222 to (b) the cross-sectional area defined between the first outer tube 140 and the second outer tube 142 occupied by the purge fluid channel 226 is typically greater than 3:2, greater than 3:1, or greater than 5:1. In some applications, the blood pressure measurement tubing 222 occupies a relatively large portion of the cross-sectional area defined between the first outer tube 140 and the second outer tube 142 to communicate blood pressure outside the pump outlet tubing 24 within the subject's left ventricle proximally to the pressure sensor 216.

[0219] 9B, in some applications, optical fiber 228 is configured to extend to at least outer surface 213 (FIG. 9A) of vessel 24 such that a distal end 230 of the optical fiber is directly exposed to the patient's bloodstream outside vessel 24. Typically, the optical fiber extends from a proximal end of the fiber that is outside the subject's body (e.g., within motor unit 23) to distal end 230. Further typically, a light source and a light detector (not shown) are disposed at the proximal end of the optical fiber and configured to detect blood pressure at the distal end of the optical fiber by directing light through the optical fiber and detecting reflected light.

[0220] Typically, distal end 230 of optical fiber 228 is configured to be proximal to the blood pump (e.g., proximal to impeller 50) within the subject's left ventricle. Typically, the pressure sensor measures the subject's blood pressure (i.e., left ventricular blood pressure) outside tube 24 by measuring the pressure of the blood at distal end 230 of optical fiber 228. In some applications, computer processor 25 (FIG. 1A) receives an indication of the measured blood pressure and controls the pumping of blood by the impeller in response to the measured blood pressure.

[0221] For some applications, the ventricular assist device includes two or more such optical fibers 228, for example, as shown in FIG. 9B . For some applications, based on the blood pressure measured using each of the optical fibers, the computer processor 25 determines whether the distal end of one of the optical fibers is not exposed to left ventricular blood flow. This may occur, for example, because the distal end of one of the optical fibers has contacted the wall of the interventricular septum and / or a portion within a different ventricle. Typically, in response to determining that the distal end of one of the optical fibers is not exposed to left ventricular blood flow, the computer processor determines the subject's left ventricular pressure based on the blood pressure measured using another of the two or more optical fibers 228.

[0222] In some applications, the optical fiber is disposed within the second outer tube 142 along its length. Typically, at the distal end of the second outer tube, the optical fiber is coupled to the proximal cone 36 of the frame 34, such that the optical fiber extends radially to the outer surface of the pump outlet tubing 24. For example, as shown in FIG. 9B , the optical fiber may be sutured or tied to the proximal cone of the frame 34 using a coupling element 232 (e.g., a thread). In some applications (not shown), the distal portion of the optical fiber 228 is disposed outside the pump outlet tubing 24. For example (not shown), the optical fiber 228 may extend from the second outer tube 142 to the proximal end of the pump outlet tubing 24, and then the optical fiber may be coupled to the outer surface of the pump outlet tubing 24.

[0223] It should be noted that with respect to both the blood pressure measuring tubing 222 and the optical fiber 228, the distal end of the tubing or fiber is typically in direct fluid communication with the subject's left ventricular blood flow at a location proximal to the proximal-most portion of the one or more blood inlet openings 108 (e.g., at least 1 cm, or at least 1.5 cm proximal to the proximal-most portion of the one or more blood inlet openings 108). As such, the distal end of the tubing or fiber is typically exposed to blood having a pressure that reflects the blood pressure of the left ventricle itself and that is not affected by pressure changes that occur near the blood inlet openings as a result of fluid flow dynamics occurring at the blood inlet openings.

[0224] With respect to both the blood pressure measurement tube 222 and the optical fiber 228, in some applications, the tube or fiber is coupled to the outer surface of the second outer tube 142. In some applications, the tube or fiber terminates within the aorta (e.g., on the second outer tube 142 or at the proximal end of the pump outlet tube 24) to measure aortic pressure. In some applications, the tube or fiber terminates outside the pump outlet tube near the frame 34 and is configured to measure left ventricular pressure. In some such applications, the computer processor determines whether it is properly positioned relative to the aortic valve and left ventricle based on the blood pressure measured using the tube or fiber. In some applications, the tube or fiber terminates at the distal bearing housing 118H or the distal tip element 107 and is configured to measure pressure near the blood inlet opening. In some applications, the tube or fiber runs along the outside of at least a portion of the pump outlet tube (e.g., from the proximal end of the pump outlet tube to near the frame 34).

[0225] In some applications, the tube or fiber is bonded to the outside of the pump outlet tubing by sandwiching the tube or fiber between the polymer film and the outer surface of the pump outlet tubing using a bonding method such as thermal bonding, dipping, or adhesive bonding. In some applications, the tube or fiber is bonded to the outside of the pump outlet tubing (e.g., using the methods described above) along the entire length of the overlap between the tube or fiber and the pump outlet tubing. Alternatively, the tube or fiber is bonded to the outside of the pump outlet tubing (e.g., using the methods described above) only at segmented locations along the length of the overlap between the tube or fiber and the pump outlet tubing. In some applications, by bonding the tube or fiber only at segmented locations, the flexibility of the pump outlet tubing is greater than if the tube or fiber were bonded to the pump outlet tubing along the entire length of the overlap between the tube or fiber and the pump outlet tubing. As described above, in some applications, the tube or fiber is bonded to the outside of the pump outlet tubing by sandwiching the tube or fiber between the polymer film and the outer surface of the pump outlet tubing. In some applications, the polymer layer is applied at segmented locations. For some applications, a ring-shaped polymer layer is applied around the entire circumference of the pump outlet tubing at each segmented location. Alternatively, as described below with reference to FIG. 31 , one or more bands are applied around only a portion of the circumference of the pump outlet tubing at each segmented location (or along the entire length of the overlap between the tube or fiber and the pump outlet tubing). For some applications, the bands are bonded to the pump outlet tubing to cause the pump outlet tubing to assume a desired curvature when deployed within a subject's body. For some applications, the bands are bonded to the pump outlet tubing to cause different regions of the pump outlet tubing to assume different degrees of curvature and / or to cause the pump outlet tubing to twist as blood is pumped through the pump outlet tubing.

[0226] Reference is now made to FIGS. 10A and 10B, which are schematic illustrations of a ventricular assist device 20 including a liner 39 lining the inside of a frame 34 that houses an impeller 50, according to some applications of the present invention. In some applications, the liner 39 is disposed on the inside of the frame 34 to provide a smooth inner surface (e.g., a smooth inner surface having a substantially circular cross-sectional shape) through which blood is pumped by the impeller. By providing a smooth surface, the coating material typically reduces hemolysis caused by the pumping of blood by the impeller compared to when blood is pumped between the impeller and the struts of the frame 34. In some applications, the liner 39 includes polyurethane, polyester, and / or silicone. Alternatively or additionally, the liner includes polyethylene terephthalate (PET) and / or polyether block amide (PEBAX®).

[0227] Typically, the liner is disposed on at least a portion of the inner surface of the central cylindrical portion 38 of the frame 34. In some applications, the pump outlet tube 24 also covers the central cylindrical portion 38 of the frame 34 around the outside of the frame, such that the pump outlet tube 24 and the liner 39 overlap over at least 50 percent of the liner's length, and along the entire length of the cylindrical portion of the frame 34, as shown, for example, in FIG. 10A . In some applications, the pump outlet tube 24 and the liner 39 only partially overlap, as shown, for example, in FIG. 10B . For example, the pump outlet tube 24 may overlap the liner 39 along less than 50 percent of the liner's length (e.g., along less than 25 percent). In some such applications, during insertion of the ventricular assist device 20 into the subject's body, the impeller advances distally within the frame 34, such that the impeller is no longer disposed within the overlapping area between the pump outlet tube and the liner, and there is no longitudinal position where the impeller, pump outlet tube 24, frame 34, and liner 39 all overlap one another. 10A and 10B, in some applications, the distal end of the pump outlet tube and / or liner defines a single axially oriented blood inlet opening 108. Alternatively, the liner is disposed on at least a portion of the inner surface of the central cylindrical portion 38 of the frame 34, and the pump outlet tube extends to the distal end of the frame, defining multiple lateral blood inlet openings 108. Such applications are described in further detail below, for example, with reference to FIGS.

[0228] Typically, in the overlap area between the liner 39 and the pump outlet tube 24, the liner is shaped to form a smooth surface (e.g., to reduce hemolysis, as described above), and the pump outlet tube 24 is shaped to match the struts of the frame 34 (e.g., as shown in cross section in FIG. 10A ). Furthermore, typically, the liner has a substantially circular cross section (e.g., due to the relatively small cell width within the central cylindrical portion of the frame, as described above with reference to FIG. 2 ). In some applications, in the overlap area between the liner 39 and the pump outlet tube 24, the pump outlet tube and the liner are bonded to one another, for example, by vacuum, adhesive, and / or using a thermoforming procedure.

[0229] In some applications, the liner 39 and the pump outlet tube 24 are made of different materials. For example, the liner may be made of polyurethane and the pump outlet tube may be made of polyether block amide (PEBAX®). Typically, in such applications, the material from which the liner is made has a higher thermoforming temperature than the material from which the pump outlet tube is made. Alternatively, the liner 39 and the pump outlet tube 24 are made of the same material. For example, both the liner and the pump outlet tube may be made of polyurethane or polyether block amide (PEBAX®).

[0230] In some applications, the pump outlet tube and the liner are bonded to each other and / or the frame as follows: In some applications, the liner is bonded directly to the inner surface of the frame, and then the pump outlet tube is bonded to the outside of the frame. Note that by directly bonding the liner to the inner surface of the frame (rather than simply bonding the liner to the pump outlet tube, thereby sandwiching the frame between the liner and the pump outlet tube), air bubbles, creases, and other interruptions to the surface smoothness imparted by the liner are typically avoided. In some applications, the bond between the liner and the inner surface of the frame is strengthened using techniques similar to those described above for strengthening the bond between the elastomeric film and the helical elongated element of the impeller. In some applications, the frame is first treated to strengthen the bond between the liner and the inner surface of the frame. For some applications, treating the frame includes subjecting the frame (e.g., to an inner surface of the frame) to a plasma treatment, immersing the frame in a bonding agent (e.g., a silane solution) having at least two functional groups configured to bond with each of the materials from which the frame and liner are made, and / or immersing the frame in a solution containing the material from which the liner is made (e.g., a polyurethane solution). For some applications, the liner is made of an elastomeric material (e.g., polyurethane), and the bonding agent is a silane solution, such as a solution of n-(2-aminoethyl)-3-aminopropyltrimethoxysilane, where the silane contains a first functional group (e.g., (OH)) configured to bond with the frame (usually made of an alloy such as Nitinol) and a second functional group (e.g., (NH)) configured to bond with the elastomeric material.

[0231] In some applications, the central cylindrical portion of the frame is then sprayed with a solution containing the material from which the liner will be made (e.g., a polyurethane solution). Once the inner surface of the frame has been treated, the liner is bonded to the inner surface of the central cylindrical portion of the frame (e.g., to the inner surface of the central cylindrical portion of the frame). Typically, the liner (formed as a tube) is placed on a mandrel, the frame is placed over the liner, and pressure is applied via a heat shrinking process. Furthermore, the liner and frame assembly is typically heated in an oven.

[0232] After bonding the liner to the frame, a portion of the pump outlet tube 24 is placed around the outside of the frame. As noted above, in some applications, the liner 39 and the pump outlet tube 24 are made of different materials. For example, the liner may be made of polyurethane, and the pump outlet tube may be made of polyether block amide (PEBAX®). Typically, in such applications, the material from which the liner is made has a higher thermoforming temperature than the material from which the pump outlet tube is made. In some applications, the frame is heated to a temperature above the thermoforming temperature of the pump outlet tube 24 but below the thermoforming temperature of the liner 39 to mold the pump outlet tube 24 to match the struts of the frame 34 without deforming the liner.

[0233] Typically, the frame is heated from the inside using a mandrel. Typically, while the frame is heated to the above-mentioned temperature, an outer tube (typically made of silicone) applies pressure to the pump outlet tube 24, pushing it radially inward, to conform to the shape of the struts of the frame, as shown in the cross-sectional view of FIG. 10A. In some applications, at this stage, the mandrel placed inside the liner and heating the liner is shorter than the length of the liner. The mandrel is typically placed inside the liner so that there is a margin outside the mandrel at each end of the liner. Typically, the liner acts as a shield to protect the pump outlet tube from overheating and being damaged by the heating of the mandrel. Placing the liner over the mandrel as described above prevents the mandrel from coming into direct contact with the frame and / or the pump outlet tube. In some applications, the combination of the frame, liner, and the portion of the pump outlet tube 24 disposed around the frame is then set to the desired shape and dimensions using setting techniques known in the art.

[0234] Reference is now made to Figure 10C, which is a schematic illustration of a liner including an extension 39e extending proximally beyond the cylindrical portion 38 of the frame 34, in accordance with some applications of the present invention. In some applications, the liner extension 39e is not bonded to the inner surface of the frame 34; rather, the material comprising the extension is free to flap in the blood flow generated by the impeller. In some cases, the liner extension increases the efficiency of blood pumping by the impeller, for example, by modifying the nonlinear flow path of blood generated by the pumping of the impeller.

[0235] Reference is now made to FIGS. 11A-E, which are schematic illustrations of pump outlet tube 24, or a portion thereof, configured to define a lateral blood inlet opening 108 at its distal end, according to some applications of the present invention. In some applications, the pump outlet tube extends substantially to the distal end of distal cone 40 of frame 34. In such applications, the pump outlet tube typically defines a distal cone 46 that is distally oriented, i.e., oriented such that the narrow end of the cone is distal to the wide end of the cone. Typically, the pump outlet tube includes a coupling 41 (e.g., the tubular coupling shown in the figures) extending distally from the pump outlet tube. As noted above, the coupling is coupled to the distal bearing housing to secure the distal end of the pump outlet tube.

[0236] In some applications (not shown), the pump outlet tube defines two to four lateral blood inlet openings. Typically, in such applications, each of the blood inlet openings defines an area greater than 20 square millimeters (e.g., greater than 30 square millimeters) and / or less than 60 square millimeters (e.g., less than 50 square millimeters), e.g., between 20 and 60 square millimeters, or between 30 and 50 square millimeters. Alternatively or additionally, the outlet tube defines more or smaller blood inlet openings 108, e.g., greater than 10 blood inlet openings, greater than 50 blood inlet openings, greater than 100 blood inlet openings, or greater than 150 blood inlet openings, e.g., between 50 and 100 blood inlet openings, 100 and 150 blood inlet openings, or 150 and 200 blood inlet openings. For some applications, the blood inlet opening is sized to (a) allow blood to enter the tube from the subject's left ventricle and (b) prevent left ventricular structures from entering the frame. Typically, for such applications, the distal conical portion 46 of the pump outlet tube 24 is configured to reduce the risk of left ventricular structures (such as chordae tendineae, trabeculae, and / or papillary muscles) entering the frame 34 and potentially being damaged by the impeller and / or axial shaft, and / or damaging the left ventricular assist device. Thus, for some applications, the blood inlet opening is shaped such that the width (or span) of the opening in at least one direction is less than 1 mm, e.g., 0.1-1 mm, or 0.3-0.8 mm. By defining such a small width (or span), left ventricular structures (such as chordae tendineae, trabeculae, and / or papillary muscles) are typically prevented from entering the frame 34. In some such applications, each of the blood inlet openings defines an area of ​​more than 0.05 square mm (e.g., more than 0.1 square mm) and / or less than 3 square mm (e.g., less than 1 square mm), e.g., between 0.05 and 3 square mm, or between 0.1 and 1 square mm. Alternatively, each of the blood inlet openings defines an area of ​​more than 0.1 square mm (e.g., more than 0.3 square mm) and / or less than 5 square mm (e.g., less than 1 square mm), e.g., between 0.1 and 5 square mm, or between 0.3 and 1 square mm.

[0237] Typically, the portion of the pump outlet tubing that defines the blood inlet opening has a porosity (porosity being defined as the percentage of the area of ​​this porous portion that is available for blood flow) of more than 40 percent, for example more than 50 percent, or even more than 60 percent. Thus, on the one hand, the blood inlet opening is relatively small (to prevent left ventricular structures from entering the frame), but on the other hand, the porosity of the portion of the pump outlet tubing that defines the blood inlet opening is relatively high, allowing sufficient blood to flow into the pump outlet tubing.

[0238] For some applications, each of the blood inlet openings has a circular or polygonal shape. For some applications, as shown in FIGS. 11A-E, each of the blood inlet openings has a hexagonal shape. Typically, using openings with a hexagonal shape allows the portion of the pump outlet tubing defining the blood inlet openings to have a relatively high porosity (e.g., as described above), while providing sufficient material between the openings in the portion of the pump outlet tubing defining the blood inlet openings to prevent tearing and / or stretching of the material. For some applications, as shown in FIG. 11B, the gap width W between adjacent hexagonal (or other polygonal) openings is greater than 0.01 mm (e.g., greater than 0.04 mm) and / or less than 0.1 mm (e.g., less than 0.08 mm), e.g., between 0.01 and 0.1 mm, or between 0.04 and 0.08 mm. In some applications, the distance D between each opposing side of a hexagon (or other type of polygon) is greater than 0.2 mm (e.g., greater than 0.4 mm) and / or less than 0.8 mm (e.g., less than 0.6 mm), e.g., 0.2 to 0.8 mm, or 0.4 to 0.6 mm. As shown in FIG. 11B, typically, each polygon encloses a circle (i.e., structures that cannot pass through such a circle cannot pass through the polygon). Typically, the diameter of the circle enclosed by the polygon is equal to the distance D, e.g., greater than 0.2 mm (e.g., greater than 0.4 mm) and / or less than 0.8 mm (e.g., less than 0.6 mm), e.g., 0.2 to 0.8 mm, or 0.4 to 0.6 mm.

[0239] FIG. 11D illustrates a portion of the distal conical section 46 of the pump outlet tubing 24 according to some applications of the present invention. The portion is flattened out in the view of FIG. 11D for illustrative purposes. As shown in FIG. 11D, for some applications, the gap width W1 between the hexagonal (or other polygonal) holes in the proximal region 46P of the distal conical section 46 of the pump outlet tubing 24 is greater than the gap width W between the hexagonal (or other polygonal) holes in the distal region 46D of the distal conical section 46 of the pump outlet tubing. For some applications, the ratio of the gap width between adjacent blood inlet openings in the proximal region of the distal portion of the pump outlet tubing to the gap width between adjacent blood inlet openings in the distal region of the distal portion of the pump outlet tubing is greater than 3:2, e.g., 3:2 to 5:2. Typically, in such applications, the distance D1 between opposing sides of each hexagon (or other type of polygon) in the proximal region 46P of the distal conical section 46 of the pump outlet tubing 24 is less than the distance D between opposing sides of each hexagon (or other type of polygon) in the distal region 46D of the distal conical section 46 of the pump outlet tubing. (As noted above, the distances D and D1 typically also represent the diameter of a circle enclosed by a polygon of the respective size.) In some applications, the ratio of the diameter of a circle enclosed by each blood inlet opening in the distal region of the distal section of the pump outlet tubing to the diameter of a circle enclosed by each blood inlet opening in the proximal region of the distal section of the pump outlet tubing is greater than 7:6, e.g., between 7:6 and 4:3. Furthermore, typically, the distal conical section of the pump outlet tubing 24 has a higher porosity in the distal region 46D than in the proximal region 46P of the distal conical section 46 of the pump outlet tubing. For example, the ratio of porosity in distal region 46D to porosity in proximal region 46P is greater than 4:3, or greater than 3:2. For some applications, the proximal region extends along a length greater than 0.5 mm and / or less than 2 mm (e.g., less than 1.5 mm), e.g., 0.5-2 mm or 0.5-1.5 mm. For some applications, the total length of the distal cone is greater than 6 mm and / or less than 12 mm (e.g., less than 10 mm), e.g., 6-12 mm or 6-10 mm.

[0240] As described above with reference to Figures 10A-B, the pump outlet tubing is typically bonded to the frame 34 by heating. In some applications, to prevent and / or mitigate damage (e.g., tearing, thinning, and / or stretching) that may occur to the material defining the blood inlet holes during the heating process, the gaps between the blood inlet holes are wider and / or the blood inlet holes are smaller and / or the porosity is lower in the proximal region 46P of the distal cone 46 of the pump outlet tubing 24 than in the distal region 46D. In some applications, as a result of the heating process, the difference in size of the gaps between the blood inlet holes and / or the size and / or porosity of the blood inlet holes themselves between the distal region 46D and the proximal region 46P is reduced or eliminated.

[0241] Typically, the gap width W between the hexagonal (or other polygonal) holes in the distal region 46D of the distal conical section 46 of the pump outlet tubing and the distance D between opposite sides of each hexagonal (or other polygonal) hole are as described above. In some applications, the gap width W1 between adjacent hexagonal (or other polygonal) holes in the proximal region 46P of the distal conical section 46 of the pump outlet tubing 24 is greater than 0.05 mm (e.g., greater than 0.07 mm) and / or less than 0.2 mm (e.g., less than 0.15 mm), e.g., between 0.05 and 0.2 mm, or between 0.07 and 0.15 mm. In some applications, the distance D1 between opposing sides of each hexagon (or other type of polygon) within the proximal region 46P of the distal conical portion 46 of the pump outlet tube 24 is greater than 0.1 mm (e.g., greater than 0.3 mm) and / or less than 0.6 mm (e.g., less than 0.5 mm), for example, between 0.1 and 0.6 mm, or between 0.3 and 0.5 mm.

[0242] The scope of the present disclosure includes having lateral blood inlet openings of non-uniform size and / or shape (e.g., circular, rectangular, polygonal, and / or hexagonal lateral blood inlet openings) arranged in any arrangement along the distal conical portion 46 of the pump outlet tubing. Similarly, the scope of the present disclosure includes configuring the distal conical portion 46 of the pump outlet tubing defining the lateral blood inlet openings to have non-uniform porosity that varies in different regions of the distal cone. In some applications, the shape and / or size of the lateral blood inlet openings and / or the porosity of the distal cone vary to accommodate different hemodynamics in different regions of the distal cone. Alternatively or additionally, the shape and / or size of the lateral blood inlet openings and / or the porosity of the distal cone vary to accommodate the varying shapes along the length of the distal cone.

[0243] In some applications, along the distal conical portion 46 of the pump outlet tubing 24, the thickness of the polymeric material from which the pump outlet tubing is made is greater than the thickness in other regions of the pump outlet tubing (e.g., within the central cylindrical portion and / or proximal conical portion of the pump outlet tubing). In some such applications, the tubing is manufactured in this manner to prevent tubing from splitting within the distal conical portion 46, which defines the blood inlet opening 108, and which may (in some cases) be at greater risk of splitting than other portions of the pump outlet tubing.

[0244] Reference is now made to FIG. 11E, which is an enlarged schematic illustration of the interface between the distal end of the pump outlet tubing 24 and the distal tip element 107. Typically, the pump outlet tubing includes a coupling 41 (e.g., a tubular coupling as shown) extending distally from the pump outlet tubing. As noted above, the coupling is coupled to the distal bearing housing 118H to secure the distal end of the pump outlet tubing. As further noted above, the pump outlet tubing is typically coupled to the outside of the central cylindrical portion of the frame. In some applications, the distal cone 46 of the pump outlet tubing itself is not joined to the distal cone 40 of the frame. Rather, the distal cone 46 of the pump outlet tubing is held in place relative to the distal cone 40 of the frame by coupling the coupling 41 to the distal bearing housing 118H and coupling the pump outlet tubing to the outside of the central cylindrical portion of the frame. Alternatively, the distal cone 46 of the pump outlet tubing is directly coupled (e.g., by heat shrinking) to the distal cone 40 of the frame.

[0245] As described above, in some applications, the coupling portion 41 is coupled to the outer surface of the portion 123 of the distal bearing housing 118H. In some applications, the coupling portion 41 defines a hole 111 (e.g., near the distal end of the coupling portion), as shown in FIG. 11E . In some applications, adhesive is applied through the hole between the coupling portion 41 and the outer surface of the portion 123 of the distal bearing housing 118H. In some applications, the outer surface of the portion 123 of the distal bearing housing 118H is threaded. Typically, the threaded outer surface allows the adhesive to spread gradually and evenly between the coupling portion 41 and the outer surface of the portion 123 of the distal bearing housing 118H. Furthermore, the coupling portion is typically transparent, such that the adhesive spread is visible through the coupling portion. Thus, in some applications, application of the adhesive is terminated when the adhesive has sufficiently spread between the coupling portion 41 and the outer surface of the portion 123 of the distal bearing housing 118H (e.g., when the outer surface of the portion 123 is covered with adhesive).

[0246] Reference is now made to Figures 12A, 12B, and 12C, which are schematic illustrations of a drive cable 130 of a ventricular assist device 20, according to some applications of the present invention. Typically, rotational motion of the motor is transmitted to the axial shaft via a drive cable. Typically, the drive cable extends from the motor unit 23 (which is typically disposed outside the subject's body) to the proximal end of the axial shaft 92 (the connection between the distal end of the drive cable and the proximal end of the axial shaft is shown, for example, in one of the close-ups in Figure 5A). In some applications, the drive cable includes multiple wires 134 arranged in a coiled configuration to provide the drive cable with sufficient strength and flexibility so that a portion of the cable can be maintained within the aortic arch while the cable rotates and moves in an axial back-and-forth motion.

[0247] For some applications, the drive cable includes multiple coaxial layers of coiled wire. For example, as shown in FIGS. 12A-C, the drive cable includes an outer layer 136, a middle layer 138, and an inner layer 156, which are coaxial with one another and each include a coiled wire. For some applications, the inner and outer layers are wound in a first direction (e.g., left-handed) and the middle layer is wound in another direction (e.g., right-handed, or vice versa). For some applications, the drive cable includes more or fewer layers of coiled wire (e.g., four layers or two layers). For some applications, each layer includes 2 to 8 wires, e.g., 4 to 6 wires, within the coil. For some such applications, the diameter of the drive cable is greater than 1.05 mm, e.g., 1.1 to 1.4 mm, e.g., 1.1 mm, 1.2 mm, or 1.3 mm.

[0248] The drive cable is typically disposed within a first outer tube 140 configured to remain stationary while the drive cable undergoes rotational and / or axial back-and-forth movement. The first outer tube is configured to effectively act as a bearing tube for the drive cable along its length. For this reason, the first outer tube is also referred to herein as a drive cable bearing tube. Drive cable bearing tubes are described in more detail below with reference to FIGS. 12D-I. In some applications, the drive cable bearing tube is disposed within a second outer tube 142, which is typically made of a more flexible material (e.g., nylon and / or polyether block amide) and is typically thicker than the drive cable bearing tube. The second outer tube 142 may also be referred to herein as a mechanical property tube 142 or a delivery tube 142. The second outer tube 142 is described in more detail below with reference to FIG. 13.

[0249] Typically, during insertion of the impeller and frame into the left ventricle, the impeller 50 and frame 34 are maintained in a radially constrained configuration by the delivery catheter 143. As described above, the delivery catheter is retracted to allow the impeller and frame to assume a radially unconstrained configuration. In some applications, as shown in FIG. 12A , the delivery catheter remains within the subject's aorta and the outer tube 142 is disposed within the delivery catheter during operation of the left ventricular device. (Although FIG. 12A shows the distal end of the delivery catheter disposed within the aortic arch, in some applications, the distal end of the delivery catheter is disposed within the descending aorta during operation of the left ventricular device.) In some applications, a channel 224 is defined between the delivery catheter 143 and the outer tube 142 during operation of the left ventricular device. (Note that for illustrative purposes, the channel shown in FIG. 12A is not to scale.) In some such applications, the subject's aortic blood pressure is measured by measuring the pressure of blood within the channel 224. For example, pressure sensor 216 (shown schematically in FIG. 1A ) may be in fluid communication with channel 224 and may be configured to measure the subject's aortic pressure by measuring the pressure of blood in channel 224. Typically, to retract the left ventricular device from the subject's body, a delivery catheter is advanced over the impeller and frame, causing the impeller and frame to assume a radially constrained configuration. The catheter is then withdrawn from the subject's body.

[0250] Reference is now made to FIG. 12D , which is a schematic illustration of a first outer tube 140 that functions as a drive cable bearing tube, according to some applications of the present invention. For some applications, the drive cable bearing tube includes an outer layer 141 and an inner layer 144, each typically made of a biocompatible polymeric material, and a coil 153 embedded between the outer and inner layers. For some applications, the outer layer 141 is made of Pebax, the inner layer 144 is made of PTFE and / or polyimide (e.g., a blend of PTFE and / or polyimide), and the coil is made of an alloy such as stainless steel. Typically, the inner layer includes a material configured to provide low levels of friction and high wear resistance. Furthermore, typically, the outer layer is configured to provide additional strength to the drive cable bearing tube while still providing the drive cable bearing tube with sufficient flexibility to conform to the curvature of, for example, the aortic arch. Typically, the coil is configured to maintain the substantially circular cross-section of the drive cable bearing tube, even in regions where the drive cable bearing tube is highly curved (e.g., within the aortic arch). Typically, in the absence of a coil, the drive cable bearing tube tends to flatten in such areas, forming an oval cross section.

[0251] For some applications, the outer coiled wire of the drive cable is swaged to flatten the wire within the coil within at least a portion of the drive cable. For some applications, the outer coiled wire of the drive cable is swaged as described above along the portion of the drive cable that is disposed within the aortic arch. Typically, when the outer coiled wire is round, the outer coiled wire of the drive cable contacts the inner surface of the drive cable bearing tube only outside the circular cross section of each wire, so that the frictional force that each wire exerts on the inner surface of the drive cable bearing tube is concentrated at that location. On the other hand, when the wire is flat, the frictional force that each wire exerts on the inner surface of the drive cable bearing tube is spread evenly around the entire circumference of the drive cable.

[0252] Reference is now made to FIGS. 12E, 12F, 12G, and 12H, which are schematic illustrations of a laser-cut tube 145 comprising at least a portion of the first outer tube (i.e., drive cable bearing tube) 140, according to some applications of the present invention. In some applications, the first outer tube is made of a laser-cut shape-memory material (e.g., a shape-memory alloy such as Nitinol or Cobalt Chromium) that is covered with and / or embedded in a polymeric material, such as a polyether block amide (e.g., PEBAX®) or a thermoplastic polyurethane (e.g., Pellethane®). FIGS. 12E-H show the laser-cut tube when cross-sectioned and laid flat. As shown, slits, openings, curves, and / or other shapes are typically cut into the tube to impart flexibility to the tube. In some applications, different regions of the tube are cut differently from one another to impart different respective flexibility to different regions of the tube. For example, a region of the tube configured to be positioned within the aortic arch or the ascending aorta may be configured to have greater flexibility than a portion configured to be positioned within the descending aorta.

[0253] In some applications (not shown), the bearing tube is made of one or more layers of coiled wire (e.g., as described above for the drive cable). Typically, the coiled wire is covered with and / or embedded in a polymeric material, such as a polyether block amide (e.g., PEBAX®) or a thermoplastic polyurethane (e.g., Pellethane®). In some applications, the coiled wire is flattened, for example, using a swaging process. In some applications, different regions of the tube are formed using different numbers of layers of wire and / or different numbers of wires within each layer to impart different respective flexibility to different regions of the tube. For example, a region of the tube configured to be positioned in the aortic arch or the ascending aorta may be configured to have greater flexibility than a portion configured to be positioned in the descending aorta.

[0254] In some applications, beads are disposed between the drive cable and the drive cable bearing tube to reduce friction between the drive cable and the drive cable bearing tube. Typically, the beads have a diameter of 0.05 mm to 0.15 mm. Furthermore, typically, the beads are not held in a fixed position within the space between the drive cable and the drive cable bearing tube, but are allowed to move within this space, thereby facilitating movement of the drive cable relative to the drive cable bearing tube.

[0255] Reference is now made to FIG. 12I, which is a schematic illustration of a portion of drive cable 130 and drive cable bearing tube 140, in accordance with some applications of the present invention.

[0256] For some applications, drive cable bearing tube 140 includes one or more interior-facing ceramic portions, and drive cable 130 includes one or more exterior-facing ceramic portions. Drive cable 130 is configured to pass through the drive cable bearing tube so that the exterior-facing ceramic portions are aligned with the interior-facing ceramic portions, i.e., in one or more regions, the interface between the drive cable and the interior surface of the drive cable bearing tube is ceramic-on-ceramic. Drive cable 130 is further configured at a distal end of the drive cable bearing tube to couple to an intracorporeal device, such as a blood pump, and to rotate within the drive cable bearing tube, thereby rotating the intracorporeal device while the exterior-facing ceramic portions are aligned with the interior-facing ceramic portions. In some embodiments, the interior-facing ceramic portions and / or the exterior-facing ceramic portions comprise zirconia.

[0257] In some embodiments, the ceramic portion facing the inside of the drive cable bearing tube includes a respective ceramic sleeve 147 that may line the inside of the drive cable bearing tube body or, alternatively, may be integral with the drive cable bearing tube body. For example, the drive cable bearing tube body may include a structure (or wire or braid or coil) such as a laser-cut tube 145 that is covered with or embedded within a polymeric material 148. The ceramic sleeve 147 may line or alternatively replace the structure in certain locations, as shown, for example, in FIG. 12I.

[0258] Similarly, the outwardly facing ceramic portion of the drive cable may include a respective ceramic sleeve 146 that may cover the body of the drive cable or, alternatively, may be integral with the body of the drive cable.

[0259] Typically, the regions of drive cable 130 and drive cable bearing tube 140 along which the drive cable exerts high frictional forces against the inner surface of the drive cable bearing tube are configured in this manner to prevent wear and heat buildup along such regions. For example, in embodiments in which the drive cable bearing tube is configured to pass through the subject's aorta, the drive cable bearing tube may include an inwardly facing ceramic portion in a section of the drive cable bearing tube configured to be located (i.e., disposed) within the subject's aortic arch and / or in a section of the drive cable bearing tube configured to be located within the subject's ascending aorta. Thus, the drive cable bearing tube may be inserted through the aorta such that the inwardly facing ceramic portion resides within the subject's aortic arch and / or ascending aorta.

[0260] In some embodiments, each of the inwardly facing ceramic portions is 10-200% longer than each of the outwardly facing ceramic portions, so that the outwardly facing ceramic portions may remain aligned with the inwardly facing ceramic portions as the drive cable moves axially within the drive cable bearing tube.

[0261] Reference is now made to Figure 13, which is a schematic illustration of a delivery tube 142, in accordance with some applications of the present invention.

[0262] As described above, the drive cable 130 typically passes through a first outer tube 140, which functions as a drive cable bearing tube and then passes through a delivery tube, before passing through the delivery tube 142. Typically, both the drive cable bearing tube 140 and the delivery tube extend from the motor unit 23 to the proximal bearing housing 116H. Furthermore, typically, during delivery of the pump head 27 to the left ventricle, the pump head, drive cable 130, drive cable bearing tube 140, and delivery tube 142 are disposed within a delivery catheter 143, which maintains the pump head in a radially constrained configuration. Once the pump head 27 is delivered to the left ventricle, the delivery catheter is retracted (e.g., into the descending aorta, as shown in FIG. 13 ), allowing the pump head to radially expand into a radially unconstrained configuration of the frame and impeller. The drive cable 130 then rotates the impeller to pump the target blood from the left ventricle into the aorta.

[0263] Typically, delivery tube 142 is configured to impart corresponding mechanical properties to a corresponding portion of the length of the drive cable. Additionally, typically, a purge fluid is pumped between drive cable bearing tube 140 and the delivery tube so that the purge fluid flows to the pump head and purges the interfaces between axial shaft 92 and proximal and distal radial bearings 116 and 118, as described, for example, with reference to Figures 11A-C of Tuval, US 2022 / 0226632, which is incorporated herein by reference.

[0264] As shown in the enlarged view of delivery tube 142, the delivery tube typically comprises an outer layer 167 with an optional braid 157 (e.g., a metal or alloy (e.g., stainless steel) braid) or wire disposed within outer layer 167.

[0265] For some applications, delivery tube 142 is configured to provide different mechanical properties to regions along the delivery tube. For example, outer layer 167 may vary along the length of the delivery tube, e.g., by having different compositions and / or different thicknesses. Instead of or in addition to outer layer 167 varying along the length of the delivery tube, braid 157 may have a pick density that varies along the length of the delivery tube, or the coil (substituting for braid 157) may have a pitch that varies along the length of the delivery tube. Due to this variation in outer layer 167 and / or braid 157 (or the coil), the bending stiffness (or “stiffness”) of the delivery tube at a first portion P1 of the delivery tube configured to cross the subject's aortic valve is less than the bending stiffness at a second portion P2 of the delivery tube configured to cross at least a portion of the subject's aortic arch, which in turn is less than the bending stiffness at a third portion P3 of the delivery tube configured to cross the subject's descending aorta. Advantageously, this change in bending stiffness facilitates passage of the delivery tube through the aorta and into the left ventricle.

[0266] For example, the outer layer 167 may comprise a (thermoplastic) polyurethane (e.g., Pellethane®) jacket (or “coating”) in the first portion P1, a polyether block amide (e.g., PEBAX®) jacket in the second portion P2, and a polyamide (e.g., Grilamid®) jacket in the third portion P3.

[0267] For some applications, the ratio of the pick density of the braid in the first portion P1 of the delivery tube to the pick density of the braid in the third portion P3 of the delivery tube is between 3:2 and 5:2. For some applications, the pick density of the braid in the first portion of the delivery tube is between 30 and 50 picks per inch, and the pick density of the braid in the third portion of the delivery tube is between 15 and 25 picks per inch.

[0268] In some embodiments, the bending stiffness of delivery tube 142 increases monotonically between first portion P1 and third portion P3. For example, between a polyurethane jacket at first portion P1 and a polyamide jacket at third portion P3, outer layer 167 may comprise a polyether block amide jacket or multiple polyether block amide jackets of increasing durometer moving proximally along the tube.

[0269] For some applications, the delivery tube defines a first region R1, a second region R2, and a third region R3, where the first region R1 comprises a first portion P1, the second region R2 comprises a second portion P2, and the third region R3 comprises a third portion P3.

[0270] Typically, the first region R1 is configured to extend proximally from the proximal end of the frame (e.g., from the proximal bearing housing 116H), through the aortic valve, and into the ascending aorta. In some applications, the first region R1 has a length of 70 mm to 100 mm, e.g., 75 mm to 95 mm.

[0271] Typically, the second region R2 extends proximally from the proximal end of the first region R1 around at least a portion of the aortic arch. For some applications, the second region R2 has a length of 40 mm to 80 mm (e.g., 50 mm to 70 mm). Alternatively, the second region R2 has a length of 150 mm to 210 mm (e.g., 160 mm to 200 mm). For some applications, the flexibility of the delivery tube gradually decreases (i.e., the bending stiffness gradually increases) along the second region R2. For example, along the second region R2, the outer layer 167 may comprise multiple polyether block amide jackets with increasing durometers moving proximally along the tube. Alternatively, the bending stiffness of the delivery tube 142 may be uniform along the second region R2.

[0272] Typically, third region R3 extends from the proximal end of second region R2 along the descending aorta, out of the patient's vasculature (e.g., via a femoral puncture FP), and to motor unit 23. For some applications, third region R3 is 1200 mm to 1500 mm in length (e.g., 1250 mm to 1450 mm). In some embodiments, flexibility gradually decreases from the distal end of region R3 to third portion P3. For example, along region R3 distal to third portion P3, outer layer 167 may comprise multiple polyether block amide jackets with increasing durometers moving proximally along the tube.

[0273] In some embodiments, the bending stiffness at the distal end of the delivery tube, identified in FIG. 13 as region R1d distal to first region R1 and which couples to the pump head (e.g., the proximal end of the proximal bearing housing), is greater than the bending stiffness at first portion P1. Advantageously, this greater bending stiffness may facilitate coupling of the delivery tube to the pump head. Typically, in such embodiments, the bending stiffness at the distal end of the delivery tube is between the bending stiffness at first portion P1 and the bending stiffness at third portion P3. For some applications, R1d is between 5 mm and 15 mm (e.g., 8 mm and 12 mm) in length.

[0274] For example, the outer layer 167 may include a polyurethane jacket on the first portion P1 and a polyether block amide (e.g., PEBAX®) jacket on the distal end. The outer layer may further include a polyamide jacket on the third portion P3, such that the bending stiffness at the distal end is between the bending stiffness of the first portion P1 and the bending stiffness of the third portion P3.

[0275] In some such embodiments, the bending stiffness increases monotonically between the first portion P1 and the distal end of the delivery tube (thus, the bending stiffness increases monotonically moving both proximally and distally from the first portion P1). For example, distal to the first portion P1, the outer layer 167 may comprise a plurality of polyether block amide jackets that increase in durometer moving distally along the tube.

[0276] In some embodiments, the bending stiffness of the fourth portion P4 of the delivery tube, which is configured to span an insertion point into a subject's body (e.g., the femoral puncture FP), is less than the bending stiffness of the third portion P3. Advantageously, this less bending stiffness may facilitate insertion into the body. Nevertheless, even in such embodiments, the bending stiffness at the proximal end of the delivery tube, i.e., proximal to the fourth portion P4 along the proximal-most portion of the third region R3, which may have a length of 360 mm to 460 mm (e.g., 380 mm to 440 mm), is greater than the bending stiffness of the fourth portion P4 (optionally greater than the bending stiffness of the third portion P3) to facilitate advancing and retracting this portion of the delivery tube relative to the handle 149 and / or to facilitate tightening of the delivery tube without kinking the delivery tube. For example, proximal to the fourth portion P4, the outer layer 167 may comprise a polyether block amide (e.g., PEBAX®) jacket with a high-performance polyamide (e.g., Grilamid®) outer coating. In some embodiments, along this proximal-most portion of the delivery tube, the delivery tube comprises a coil or metal frame positioned between the braid 157 and the outer layer 167, for example, between the fibers 159, described immediately below, and the outer layer 167. Advantageously, the coil or metal frame may also restrain kinking of the delivery tube.

[0277] In some embodiments, the delivery tube further includes at least one fiber 159 (e.g., an aromatic polyamide (i.e., aramid) fiber) extending along the length of the delivery tube 142 that increases the tensile stiffness (or “tensile strength”) of the delivery tube compared to if the delivery tube did not include the fiber 159. In other words, the fiber 159 resists elongation, thereby inhibiting stretching of the delivery tube. Thus, while the braid 157 resists bending (with the degree of this resistance optionally varying along the length of the delivery tube) and stretching, the fiber 159 provides additional resistance to stretching (i.e., the fiber provides additional tensile strength). In some applications, a relatively high resistance to stretching (i.e., a relatively high tensile strength) is desirable along the entire length of the delivery tube to prevent stretching of the delivery tube when the delivery tube is disposed inside the delivery catheter 143.

[0278] Typically, the fibers 159 are disposed inside the outer layer 167. For example, as shown in Figure 13, the fibers 159 may be disposed between the braid 157 and the outer layer 167. Alternatively, the fibers 159 may be woven into the braid 157.

[0279] Typically, the tensile stiffness of the delivery tube is more uniform than the bending stiffness of the delivery tube.

[0280] For example, (a) the ratio of the tensile strength of the third portion P3 to the tensile strength of the first portion P1 may be lower than (b) the ratio of the bending stiffness of the third portion P3 to the bending stiffness of the first portion P1. For example, the ratio of the tensile strength of the third portion P3 to the tensile strength of the first portion P1 is typically 3:2 to 5:2 (e.g., 2:1), and the ratio of the bending stiffness of the third portion P3 to the bending stiffness of the first portion P1 is 5:2 to 7:2 (e.g., 3:1). Therefore, in some applications, the ratio of the former ratio to the latter ratio is 4:3 to 5:3, e.g., 3:2.

[0281] Alternatively or additionally, the ratio of the tensile stiffness in the second portion P2 to the tensile stiffness in the first portion P1 may be less than the ratio of the bending stiffness in the second portion P2 to the bending stiffness in the first portion P1. Alternatively or additionally, the ratio of the tensile stiffness in the third portion P3 to the tensile stiffness in the second portion P2 may be less than the ratio of the bending stiffness in the third portion P3 to the bending stiffness in the second portion P2. This latter ratio, i.e., the ratio of the bending stiffness of the third portion P3 to the average bending stiffness of the second region R2 in embodiments in which the second region R2 has a variable bending stiffness, is typically 3:2 to 5:2 (e.g., 2:1).

[0282] Typically, the delivery tube has a uniform inner surface despite the non-uniformity of the outer layer 167 and / or braid 157. For example, the braid 157 may be coated with a uniform polymeric lining 155 (e.g., a thermoplastic polyurethane (e.g., Pellethane®) lining) along the length of the delivery tube 142. Thus, advantageously, the outer tube 140 (or, in some embodiments, the drive cable itself) is exposed to a uniform inner surface.

[0283] In some embodiments, the outer layer 167 is at least partially fused to the inner portion of the delivery tube 142 during its manufacture, for example via a reflow soldering process.

[0284] In relation to the above discussion regarding the bending stiffness of each portion of the delivery tube 142, it should be noted that a measure for quantifying bending stiffness is Young's modulus multiplied by the cross-sectional moment of inertia (also known as the cross-sectional moment of inertia).

[0285] Reference is now made to Figures 14A and 14B, which are schematic illustrations of the interface between drive cable 130 and axial shaft 92, in accordance with some applications of the present invention.

[0286] As noted above, a drive cable, typically comprising multiple (e.g., three layers) of coiled wire 134, extends from the motor unit 23 (disposed outside the subject's body) to the hollow axial shaft 92. Rotational motion generated by a motor within the motor unit is typically transferred to the axial shaft (and thus to the impeller) via the drive cable.

[0287] In some applications, the drive cable is coupled to the axial shaft by welding. However, in some cases, the interface between the drive cable and the axial shaft may be weakened as a result of the heat to which the drive cable and the axial shaft are subjected during welding. Therefore, in some applications, the drive cable is coupled to the axial shaft by a coupling technique other than welding. To facilitate this coupling technique, the proximal end of the axial shaft may be shaped to define a plurality of shaft holes 152.

[0288] More specifically, in some applications, a porous coupling tube 150 (which may be made of a polymer) is disposed around the distal end of the drive cable and the proximal end of the axial shaft. In other words, the distal end of the drive cable and the proximal end of the axial shaft are inserted into opposite ends of the coupling tube 150, which is shaped to define a plurality of coupling lumens 173. Then, while the ends of the drive cable and axial shaft are inside the coupling tube, a molten bonding material is flowed through the coupling lumens 173 between the coiled wire 134 at the distal end of the drive cable, through the coupling lumens and shaft lumens 152, and into the proximal end of the axial shaft. Upon solidification, the bonding material bonds the drive cable to the axial shaft. Typically, the distal end of the drive cable, the proximal end of the axial shaft, and the coupling tube are compressed and heated while the molten bonding material solidifies.

[0289] Typically, the drive cable is also hollow, and it is desirable that the drive cable and axial shaft be shaped to define a continuous lumen after the bonding material solidifies. Therefore, before the molten bonding material flows, the drive cable and axial shaft are placed on a mandrel to maintain a continuous lumen. (This continuous lumen is shown, for example, at 132 in FIG. 15B.)

[0290] Typically, the molten material comprises a molten polymer, including, for example, polyetheretherketone (PEEK). The polymer is heated so that it passes through the coupling tube lumen 173, flows between the wires of the drive cable, and enters the shaft. Upon drying and solidifying, the polymeric material couples the drive cable to the axial shaft. Figure 14A shows a porous coupling tube disposed around the distal end of the drive cable and the proximal end of the axial shaft, while Figure 14B shows an exploded view (for illustrative purposes) in which the porous coupling tube is shown separated from the distal end of the drive cable and the proximal end of the axial shaft.

[0291] In some embodiments, the molten material is flowed using a heat shrinking process. Specifically, a bonding material sleeve (e.g., a PEEK sleeve) is placed around the coupling tube, and an outer sleeve (e.g., made of polytetrafluoroethylene) is placed around the bonding material sleeve. Heat is then applied to the bonding material sleeve and the outer sleeve. The applied heat melts the bonding material sleeve, thereby forming a molten material, and causes the outer sleeve to shrink, forcing the molten material between the coiled wire 134 and into the proximal end of the axial shaft. After the molten material solidifies, the outer sleeve and any protruding pieces of solidified molten material may be removed.

[0292] In some applications, the axial shaft (or at least its proximal end) has a smaller outer diameter than the drive cable (or at least its distal end). For example, the axial shaft may have a diameter of 0.9 mm, and the drive cable may have a diameter of 1.1 mm, 1.2 mm, or 1.3 mm. In some such applications, before the proximal end of the axial shaft is inserted into the coupling tube, a porous adapter tube 151 shaped to define a plurality of adapter lumens 129 is disposed around the proximal end of the axial shaft to increase the outer diameter of the axial shaft, e.g., so that the outer diameter of the axial shaft around which the adapter tube 151 is disposed is approximately equal to the outer diameter of the distal end of the drive cable. The porous coupling tube 150 is then disposed over the distal end of the drive cable and over the porous adapter tube (which is then disposed over the proximal end of the axial shaft). Molten material is then allowed to flow into the axial shaft through the adapter lumens 129.

[0293] In some embodiments, the adapter tube 151 is made of a polymer. In other embodiments, the adapter tube comprises a metal alloy.

[0294] In some applications, the distal end of the drive cable is coupled to the proximal end of the axial shaft using the following procedure: A porous adapter tube 151 is placed over the proximal end of the axial shaft, and then a porous coupling tube is placed over the distal end of the drive cable and over the porous adapter tube. The above assembly is then placed over a mandrel that passes through the lumen defined by the axial shaft and the distal end of the drive cable. A polymeric material, such as polyetheretherketone, is heated (e.g., using a heat shrinking process) so that it passes through the porous coupling tube, the bore of the porous adapter tube, and into the bore 152 of the axial shaft. Typically, the mandrel prevents the polymeric material from entering the lumen defined by the axial shaft and the distal end of the drive cable. Once dried and solidified, the polymeric material couples the drive cable to the axial shaft.

[0295] As noted above, delivery tube 142 is typically coupled to proximal bearing housing 116H (FIG. 5A). In some embodiments, after coupling the drive cable to the axial shaft, the drive cable (along with the axial shaft) is inserted through the delivery tube such that the distal end of the drive cable is disposed within the proximal bearing housing proximal to proximal radial bearing 116. Thus, the proximal bearing housing may advantageously help prevent weakening of the coupling between the drive cable and the axial shaft.

[0296] 14B, in some applications, prior to inserting the distal end of the drive cable into the coupling tube, wires 134 are coupled at the distal end of the drive cable to strengthen the distal end. For example, a molten material (e.g., PEEK) may be flowed between wires 134 at the distal end such that the distal end of the drive cable is formed to define a tube when the molten material solidifies.

[0297] Reference is now made to Figures 14C-D, which are schematic illustrations of the interface between drive cable 130 and axial shaft 92, in accordance with some applications of the present invention. Figure 14C shows a porous coupling tube disposed around the distal end of the drive cable and the proximal end of the axial shaft, while Figure 14D shows an exploded view (for illustrative purposes) in which the porous coupling tube is shown separated from the distal end of the drive cable and the proximal end of the axial shaft.

[0298] In some embodiments, the coupling tube 150 is compliant to fit both the larger outer diameter of the drive cable and the smaller outer diameter of the axial shaft, thus typically eliminating the need for an adapter tube 151 .

[0299] Reference is now made to Figures 14E-F, which are schematic illustrations of the interface between drive cable 130 and axial shaft 92, in accordance with some applications of the present invention. Figure 14E shows a porous coupling tube disposed around the distal end of the drive cable and the proximal end of the axial shaft, while Figure 14F shows an exploded view (for illustrative purposes) in which the porous coupling tube is shown separated from the distal end of the drive cable and the proximal end of the axial shaft.

[0300] In some embodiments, the wall of the coupling tube 150 is shaped to define a plurality of tabs 154. Before the molten material flows, at least some of the tabs 154 are pressed into the shaft bore 152 so that they protrude into the shaft bore (FIG. 14D), thereby enhancing the coupling of the drive cable to the axial shaft. In embodiments in which an adapter tube 151 is used, the tabs are typically pressed into the shaft bore through the adapter bore 129, so that the tabs protrude into the shaft bore through the adapter bore.

[0301] In some embodiments, to further strengthen the connection, at least two of the tabs pressed into the shaft bore 152 have different orientations relative to the longitudinal axis of the coupling tube. In other words, at least two of these tabs are rotatable about rotational axes that have different orientations relative to the longitudinal axis. For example, in the embodiment shown in FIGS. 14E-F, one tab 154a is oriented parallel to the longitudinal axis of the coupling tube because tab 154a is rotatable about rotational axis 139a that is perpendicular to the longitudinal axis of the coupling tube, while another tab 154b is oriented perpendicular to the longitudinal axis because tab 154b is rotatable about another rotational axis 139b that is parallel to the longitudinal axis. Tabs 154a and 154b together help to withstand both axial and rotational forces.

[0302] In some embodiments, the tabs pressed into the shaft holes 152 are shaped to define corresponding holes 137 that allow molten material to flow therethrough.

[0303] Reference is now made to Figures 14G-H, which are schematic illustrations of the interface between drive cable 130 and axial shaft 92, in accordance with some applications of the present invention. Figure 14G shows a porous coupling tube disposed around the distal end of the drive cable and the proximal end of the axial shaft, while Figure 14H shows an exploded view (for illustrative purposes) in which the porous coupling tube is shown separated from the distal end of the drive cable and the proximal end of the axial shaft.

[0304] In some embodiments, before the molten material flows between the coiled wires 134 at the distal end of the drive cable and into the proximal end of the axial shaft, portions of the tabs 154 are pressed between the coiled wires so that the tabs protrude between the coiled wires, thereby strengthening the bond of the drive cable to the axial shaft. The tabs may have any shape that allows them to fit between the coiled wires, which may be different from the shape of the tabs pressed into the shaft bore. For example, in some embodiments, U-shaped tabs 154c are pressed between the coiled wires.

[0305] In some embodiments, at least one of the coiled wires (in any one or more layers of the drive cable) is cut at the distal end of the drive cable to define one or more enlarged gaps between successive windings of the coiled wire, and a portion of the tab (such as U-shaped tab 154c) is pressed into the enlarged gap. Such a cut 135 is shown in FIG. 14H.

[0306] It should be noted that the scope of the present invention includes the use of tabs 154 to strengthen the connection of the drive cable to the axial shaft, even if molten material does not subsequently flow through connection lumen 173.

[0307] In some embodiments, as shown in Figures 14E-H, the coupling bore 173 is pre-formed and the tab 154 extends into the coupling bore before being pressed into the shaft bore or between the coiled wires (thus expanding the coupling bore as the tab is pressed in). In other embodiments, the coupling bore 173 is formed as the tab is pressed in, i.e., the pressing of the tab forms the coupling bore 173 in the wall of the coupling tube.

[0308] Alternatively, or in addition to coupling the distal end of the drive cable to the proximal end of the axial shaft, the techniques described above may be used to couple the proximal end of the drive cable to the distal end of another hollow shaft configured to couple the drive cable to a rotation element configured to rotate the drive cable. For example, as described above with reference to FIG. 7A , in some applications, at the proximal end of the drive cable, the drive cable is coupled to driven magnet 82 (which is a rotation element configured to rotate the drive cable) via pin 131 (which is a hollow shaft). In some applications, the proximal end of the drive cable is coupled to the distal end of pin 131 using techniques generally similar to those described with reference to FIGS. 14A-H for coupling the distal end of the drive cable to the proximal end of axial shaft 92. The scope of the present disclosure includes coupling any two tubular and / or rod-shaped components to one another using the devices and techniques described with reference to FIGS. 14A-H , mutatis mutandis.

[0309] In some applications, the drive cable continues inside the pump head rather than terminating at a connection to the axial shaft. In some such applications, a reinforcing element is added inside the drive cable within the pump head to increase the stiffness of the drive cable within the pump head. Typically, the reinforcing element defines a lumen therethrough that functions as part of a continuous lumen, as described below with reference to FIGS. 15A-C.

[0310] In some applications, the ventricular assist device does not define a lumen within the pump head, i.e., the axial shaft coupled to the impeller is solid. In some such applications, the axial shaft may have a relatively small diameter, such as a diameter of less than 1 mm, e.g., less than 0.8 mm, 0.6 mm, or 0.4 mm. Accordingly, the axial shaft may have a smaller diameter than the drive cable (which, as noted above, is typically hollow to facilitate the flow of purge fluid therethrough). For example, the drive cable may have an outer diameter greater than 1 mm (e.g., 1 mm to 1.5 mm), and the axial shaft may have a diameter less than 1 mm, e.g., less than 0.8 mm, 0.6 mm, or 0.4 mm. Advantageously, as a result of the axial shaft defining a small diameter, the pump head portion may be radially constrained (i.e., crimped) to a smaller diameter.

[0311] Optionally, the drive cable may be coupled to the small diameter axial shaft as described above with reference to Figures 14A-H. Alternatively or additionally, the drive cable may be coupled to the small diameter axial shaft within the proximal bearing housing, such that the proximal bearing housing helps to prevent these two elements from separating from one another.

[0312] Reference is now made to Figures 15A-C, which are schematic diagrams illustrating lumens used as guidewire and purge fluid lumens, according to some applications of the present invention. In some applications, a continuous lumen extends from the proximal end of the driven magnet unit 310 (shown in Figure 15C) to the distal end of the distal tip element 107 (shown in Figures 15A-B). Typically, the lumens are defined by corresponding components at corresponding portions along the length of the ventricular assist device. More typically, starting from the proximal end, the lumens are defined by the lumen 133 of the pin 131 (Figure 15C), the lumen 132 of the drive cable 130 and axial shaft 92 (Figure 15B), and the lumen 122 of the distal tip element 107 (Figure 15A).

[0313] Referring to FIG. 15A , in some such applications, the ventricular device is guided into the aorta and left ventricle via a guidewire 10. Typically, a valve 160 (such as a duckbill valve) is disposed at the distal end of a lumen 122 in the distal tip element 107, and the guidewire is inserted through the valve. The guidewire passes through the lumen 122 (at the distal tip) and then enters a lumen 132 defined by the axial shaft at that point. The guidewire then continues through the lumen 132 all the way to the proximal end of the drive cable. From the proximal end of the drive cable, the guidewire passes through a lumen 133 defined by a pin 131 disposed outside the subject's body, even after the distal end of the ventricular assist device 20 has been inserted into the subject's left ventricle. Typically, a valve 99 (such as a duckbill valve) is disposed at the proximal end of the lumen 133 in the driven magnet unit 310, as shown in FIG. 15C , and the guidewire exits the proximal end of the driven magnet unit through the valve. Typically, when the distal end of the ventricular assist device is disposed within the subject's left ventricle, the guidewire is retracted from the subject's body by pulling it out of the proximal end of lumen 133. The axial position of driven magnet 82 (with pin 131 disposed therein) is then fixed so that it is disposed between drive magnets 77, as shown in FIG. 7A. For example, the portion of motor unit 23 in which the driven magnet is disposed may be coupled to the portion of the motor unit in which drive magnet 77 is disposed using snap-fit ​​prongs 91 (FIG. 15C).

[0314] In some applications, the use of the axial shaft and cable lumen 132 as described above eliminates the need for an additional guidewire guide for use during insertion of the left ventricular assist device 20. In some applications, the axial shaft and drive cable each have an outer diameter greater than 0.6 mm (e.g., greater than 0.8 mm) and / or less than 1.4 mm (e.g., less than 1 mm), such as 0.6 to 1.2 mm or 0.8 to 1 mm, e.g., 0.6 to 1.4 mm. In some applications, the diameter of the lumen 132 defined by the shaft and cable is greater than 0.3 mm (e.g., greater than 0.4 mm) and / or less than 0.7 mm (e.g., less than 0.6 mm), e.g., 0.3 to 0.7 mm, or 0.4 to 0.6 mm. In some applications, drive cable 130 has a total length greater than 1 meter (e.g., greater than 1.1 meters) and / or less than 1.4 meters (e.g., less than 1.3 meters), such as between 1 and 1.4 meters, or between 1.1 and 1.3 meters. Typically, the diameters of lumen 122 and lumen 133 are generally similar to the diameter of lumen 132.

[0315] For some applications, the continuous lumen is also used by the ventricular assist device's purge system 29 (shown in FIG. 1A). Typically, both the first and second outer tubes 140, 142 are stationary during drive cable rotation. For some applications, the purge system 29 controls the flow of a purge fluid (e.g., a fluid containing glucose or dextrose) through the inlet port 86 and the outlet port 88 (FIG. 15C). The fluid is configured to remove air from the space between the drive cable and the first outer tube 140, and / or to reduce friction between the drive cable 130 (which rotates) and the first outer tube 140 (which is stationary during drive cable rotation), and / or to reduce friction between the axial shaft 92 and the proximal bearing 116 (FIG. 5A) and / or the distal bearing 118.

[0316] 15B , for some applications, purge fluid is pumped between the first and second outer tubes 140, 142, with an opening 161 in the first outer tube near the proximal bearing. For some applications, purge fluid is pumped through a purge fluid channel 226 defined between the first and second outer tubes. For some applications, purge fluid flows between the first outer tube 140 and the drive cable 130 through the opening 161, as shown by purge fluid flow arrow 162a in FIG. 15B . In this manner, the interface between the drive cable 130 (which rotates) and the first outer tube 140 (which serves as a drive cable bearing tube during drive cable rotation and remains stationary) is purged. For some applications, a portion of the purge fluid also flows to the interface between the axial shaft and the proximal bearing 116, thereby purging the interface (and / or reducing frictional forces at the interface), as shown by another purge fluid flow arrow 162b in FIG. 15B . Generally, the flow of purge fluid in the direction of arrow 162b also prevents blood from flowing into the interface between the axial shaft and the proximal bearing.

[0317] As noted above, the drive cable typically includes multiple coiled wires. In some applications, purge fluid enters the lumen 132 defined by the drive cable through interstices between the coiled wires. Once disposed within the lumen 132, the purge fluid flows in both proximal and distal directions, as indicated by bidirectional purge fluid flow arrows 162c in FIG. 15B. Distal-flowing purge fluid typically exits the distal end of the lumen 132 and flows toward the lumen 122 defined by the distal tip 120 (FIG. 15A). At the end of the distal tip, the purge fluid is typically prevented from exiting the distal tip by a valve 160. Thus, a portion of the purge fluid typically flows to the interface between the axial shaft and the distal bearing 118, thereby purging the interface (and / or reducing frictional forces at the interface), as indicated by purge fluid flow arrow 162d in FIG. 15B. Generally, the flow of purge fluid in the direction of arrow 162d also prevents blood from entering the interface between the axial shaft and the distal bearing.

[0318] As noted above, when the purge fluid is disposed within the lumen 132, it flows in both the proximal and distal directions, as indicated by arrows 162c in FIG. 15B. Referring now to FIG. 15C, the purge fluid typically enters the channel between the first and second outer tubes 140, 142 via the inlet port 86. Typically, the purge fluid flows back toward the proximal end of the device via the drive cable. More typically, at the proximal end of the device, the purge fluid flows out the proximal end of the lumen 132 and then out the proximal end of the lumen 133 defined by the pin 131. Typically, the purge fluid flows to purge the interface between the pin 131 and the radial bearing 96, thereby reducing frictional forces at these interfaces. In some applications, the purge fluid flows around the driven magnet 82 to reduce frictional forces experienced by the driven magnet. In some applications, the purge fluid then flows out the outlet port 88. Typically, the purge fluid is then discarded. Alternatively, the purge fluid is returned to the device via inlet port 86 .

[0319] 7D , in some applications, the ventricular assist device 20 typically includes an additional purge fluid inlet port 89 used to pump purge fluid into a channel 224 ( FIG. 12A ) between the delivery catheter 143 and the second outer tube 142. In some applications, rather than continuously pumping purge fluid into the channel 224, fluid is pumped into the channel periodically to flush the channel. In some applications, the port 89 and the channel 224 are used to sense aortic pressure. For example, the pressure sensor 216 (shown schematically in FIG. 1A ) may be configured to measure pressure within the channel 224, within the port 89, and / or at another location in fluid communication with the channel 224.

[0320] Reference is now made to Figure 16A, which is a schematic illustration of a pump head portion of a ventricular assist device including a distal thrust bearing 260, in accordance with some applications of the present invention. Typically, bearing 260 functions as both a distal radial bearing and a distal thrust bearing. The upper view of the ventricular device shown in Figure 16A shows the device in a radially constrained (i.e., crimped) configuration, while the lower view shows the device in a radially unconstrained configuration, with arrows indicating movement of portions of the device between these two configurations.

[0321] Some applications of the present invention are described above as being directed to a ventricular assist device that does not include a thrust bearing disposed within a subject and is configured to allow axial back and forth movement of the impeller 50 and axial shaft 92. In some alternative applications, the ventricular assist device includes a thrust bearing disposed distally from the axial shaft 92 to prevent distal movement of the axial shaft beyond the thrust bearing. Optionally, the thrust bearing may also prevent proximal movement of the axial shaft, such that the thrust bearing prevents axial movement of the axial shaft. For example, in some embodiments, the thrust bearing 260 prevents the axial shaft 92 from undergoing axial movement in response to changes in the pressure gradient against which the impeller is pumping (which typically prevents the impeller from undergoing axial movement in response to changes in the pressure gradient against which the impeller is pumping).

[0322] In some applications, the thrust bearing 260 is disposed within the frame 34 as shown. For example, the thrust bearing may be disposed within a cylindrical portion of the frame or within a distal conical portion of the frame. In some applications, at the distal end of the axial shaft, the axial shaft defines a widened portion 262 configured to engage the thrust bearing and prevent the axial shaft (and thus the impeller) from undergoing axial movement. (The widened portion of the axial shaft is also radially constrained by the bearing 260, so that the bearing also functions as a distal radial bearing.) In some applications, the thrust bearing is coupled to the frame via a connecting strut 264 extending radially inward from the frame to the thrust bearing. Typically, to manufacture the frame 34, the frame is cut from a tube of a shape memory alloy, such as Nitinol. In some applications, the connecting struts 264 are cut from the tube from which the frame is cut, such that the frame and connecting struts form a single, integrated unit without having to be joined together (e.g., by adhesive, welding, etc.). Generally, in some applications, the frame and connecting struts are cut from a single piece of material to form a single, integrated unit. In some applications, the connecting struts 264 and the thrust bearings 260 themselves are cut from the tube from which the frame is cut, such that the frame, connecting struts, and thrust bearings form a single, integrated unit without having to be joined together (e.g., by adhesive, welding, etc.). Generally, in some applications, the frame, connecting struts, and thrust bearings 260 themselves are cut from a single piece of material to form a single, integrated unit.

[0323] Reference is now made to Figure 16B, which is a schematic illustration of pump head 27 of ventricular assist device 20, in accordance with some applications of the present invention. As shown in Figure 16B, the distal portion of pump head 27 is enlarged in Figure 16C, while the proximal portion of pump head 27 is enlarged in Figure 16D.

[0324] Reference is now made to Figure 16C. As noted with reference to Figure 16A, while some applications of the present invention have been described above as being directed to a ventricular assist device that does not include a thrust bearing disposed within a subject's body and that is configured to allow axial back and forth movement of the impeller 50 and axial shaft 92, in some alternative applications, the ventricular assist device includes a thrust bearing configured to reduce or impede axial movement of the axial shaft 92 in response to changes in the pressure gradient against which the impeller is pumped (and typically thereby prevent the impeller from undergoing axial movement in response to changes in the pressure gradient against which the impeller is pumped).

[0325] For some applications, a thrust bearing 270 is disposed within the distal bearing housing 118H adjacent the distal end of the axial shaft 92. Typically, the distal end of the axial shaft is configured to contact the distal thrust bearing. When the impeller pumps blood proximally, the axial shaft is urged distally. The thrust bearing prevents distal movement of the axial shaft, so that the axial shaft and impeller typically remain in an axially fixed position within the frame 34.

[0326] In some embodiments, thrust bearing portion 270 includes a proximally facing ceramic surface 271, e.g., comprising zirconia. A distally facing ceramic cover 273, e.g., comprising zirconia, covers the distal end of axial shaft 92 such that ceramic cover 273 contacts ceramic surface 271 as the axial shaft rotates. Advantageously, therefore, there is a low-friction interface between the axial shaft and the thrust bearing portion.

[0327] For some applications, the thrust bearing portion is made of a ceramic material (e.g., zirconia), i.e., the thrust bearing portion comprises a ceramic piece that includes a proximally facing ceramic surface 271. In other embodiments, the thrust bearing portion is made of a different material but is coated with a ceramic material, i.e., the thrust bearing portion is coated with a ceramic coating to provide a proximally facing ceramic surface.

[0328] It should be noted that thrust bearing portion 270 differs from thrust bearing portion 260 of Figure 16A in that thrust bearing portion 270 is completely distal from the distal end of the axial shaft, although the features described herein for thrust bearing portion 270, such as the low friction ceramic-to-ceramic interface, may be implemented in thrust bearing portion 260 as well.

[0329] As noted above, in some such applications, the axial shaft is covered with a ceramic sleeve 240 (e.g., a zirconia sleeve) along the region of the axial shaft that contacts either the proximal bearing portion 116 or the distal bearing portion 118 during operation of the ventricular assist device. Thus, the radial interface between the axial shaft and the proximal and distal bearing portions is a ceramic-ceramic interface. In some applications, the ceramic sleeve at the distal end of the axial shaft extends around the distal end of the axial shaft, resulting in a ceramic-ceramic interface between the axial shaft and the thrust bearing portion 270. In other words, a ceramic cap including a ceramic cover 273 fits around the distal end of the axial shaft, such that the ceramic cap covers both the distal end and the sidewall of the axial shaft. (Thus, essentially, the ceramic cover 273 and the ceramic sleeve 240 are combined into a single element.) In other embodiments, as shown in FIG. 16C , a separate ceramic cover is applied to the distal end of the axial shaft, resulting in a ceramic-ceramic interface between the axial shaft and the thrust bearing portion 270. In other words, ceramic cover 273 covers the distal end of the axial shaft, while ceramic sleeve 240 covers the sidewall of the axial shaft. (Typically, in such embodiments, ceramic cover 273 is bonded to ceramic sleeve 240.)

[0330] In some embodiments, the axial shaft 92 is shaped to define a shaft lumen 132d that is the distal portion of the lumen 132 (FIG. 15B) that extends through the drive cable and axial shaft. For some applications, the thrust bearing defines a bearing lumen 272 therethrough. Typically, the bearing lumen 272 serves as part of a continuous lumen through the device used for guidewire insertion and / or as a purge fluid channel, as described above with reference to FIG. 15A. In other words, the bearing lumen 272 is continuous with the shaft lumen 132d.

[0331] For some applications, at least a portion of bearing lumen 272 is frusto-conical, with the wider end of the bearing lumen facing distally. In other words, at its distal end 272d, the lumen defines a portion of a cone, with the wider end of the cone facing distally. Typically, the frusto-conical portion of the lumen facilitates advancement of a guidewire through the thrust bearing in a distal-to-proximal direction.

[0332] In some applications, the thrust bearing 270 is configured to allow proximal (or "reverse") flow of fluid (particularly purge fluid) to the interface between the distal end of the axial shaft and the thrust bearing (e.g., between the ceramic cover 273 and the proximally-facing ceramic surface 271). In some such applications, the thrust bearing defines at least one additional bearing lumen (not shown) for proximal flow of purge fluid through the additional bearing lumen and into the interface. In other words, the thrust bearing may define one or more additional flow paths to facilitate distal-to-proximal flow of purge fluid and flow through the interface between the thrust bearing and the axial shaft.

[0333] Now refer to Figure 16D.

[0334] Typically, when a ventricular assist device includes a thrust bearing within the pump head, the impeller and axial shaft do not undergo axial back and forth movement because the impeller, pumping blood proximally, urges the axial shaft distally. The thrust bearing prevents distal movement of the axial shaft, so that the axial shaft and impeller remain in an axially fixed position within the frame 34.

[0335] In some such applications, and even in some applications where there is no thrust bearing (the proximal bearing housing 116H houses the proximal radial bearing 116 but not the thrust bearing, and the impeller and axial shaft undergo axial motion), the drive cable 130 is coupled to the axial shaft 92 within the proximal bearing housing. In other words, the interface between the distal end of the drive cable 130 and the proximal end of the axial shaft 92 (i.e., where the drive cable and axial shaft are coupled to one another) is within the proximal bearing housing 116H. Because the proximal bearing housing is typically rigid, the proximal bearing housing protects the area where the drive cable and axial shaft are coupled to one another from forces, such as bending forces, that could weaken the coupling and damage the ventricular assist device. For example, the proximal bearing housing may restrict the drive cable from bending within the bearing housing.

[0336] Typically, in such embodiments, the radial distance between the proximal bearing housing and the distal end of the drive cable within the proximal bearing housing is less than 2 mm, e.g., less than 1 mm, which has the advantage that it can help to constrain bending of the drive cable.

[0337] 14A-H. Thus, for example, FIG. 16D shows a coupling tube 150 partially disposed within a proximal bearing housing. In some applications, the coupling tube 150 (used to couple the drive cable to the axial shaft) itself is made of ceramic (e.g., zirconia) and configured to provide the functionality of the sleeve 240, thereby typically eliminating the need for the sleeve 240 in addition to the coupling tube 150.

[0338] As described above, the proximal radial bearing 116 surrounds the axial shaft and is configured to radially stabilize the axial shaft while it rotates. The proximal sleeve 240 is disposed about the axial shaft such that the proximal sleeve 240 contacts the proximal radial bearing 116 as the axial shaft rotates. Similarly, the distal radial bearing 118 (FIG. 16C) surrounds the axial shaft distally from the proximal radial bearing and is configured to radially stabilize the axial shaft while it rotates. The distal sleeve 240 is disposed about the axial shaft distally from the proximal sleeve such that the distal sleeve contacts the distal radial bearing as the axial shaft rotates.

[0339] In some applications, when the ventricular assist device includes thrust bearings within the pump head (and thus the impeller and axial shaft do not undergo axial back-and-forth motion), the sleeve 240 (disposed around the axial shaft at the interfaces between the axial shaft and the proximal and distal radial bearings) is shorter than when the ventricular assist device does not include thrust bearings within the pump head (and the impeller and axial shaft undergo axial back-and-forth motion). This is because the portions of the axial shaft located at the interfaces with the proximal and distal radial bearings are relatively fixed. In some applications, the length of each of the proximal and distal radial bearings is 2-4 mm (e.g., approximately 3 mm), and the length of each of the sleeves is 2.5-4.5 mm (e.g., approximately 3.5 mm). In some applications, the length of each of the sleeves is 4-6 mm (e.g., approximately 5 mm) to provide more clearance at the ends of the radial bearings.

[0340] In some applications, the axial shaft is more flexible than the sleeve. For example, the sleeve may be made of a ceramic material (e.g., zirconia) and the axial shaft may be made of a material that is more flexible than the ceramic, such as nitinol or other shape memory alloy. Typically, it is desirable for the axial shaft to be flexible enough to negotiate curves in the vasculature during delivery of the device to the left ventricle, yet rigid enough to support the impeller during operation of the impeller without the axial shaft vibrating.

[0341] In some such applications, the length of the sleeve relative to the length of the shaft is configured to provide a desired overall flexibility for the axial shaft and / or to provide a desired flexibility for each portion of the axial shaft. For example, the ratio of the length of the axial shaft to the combined length of the proximal and distal sleeves may be greater than 2:1 (e.g., greater than 3:1) and / or less than 6:1 (e.g., less than 5:1), e.g., 2:1 to 6:1 or 3:1 to 5:1. In some such applications, the length of the axial shaft is 30 to 50 mm, e.g., 35 to 45 mm. As noted above, to provide more clearance at the ends of the radial bearings, the length of each of the proximal and distal sleeves may be 4 to 6 mm (e.g., about 5 mm), resulting in a total sleeve length of 8 to 12 mm.

[0342] Reference is now made to FIG. 16E , which is a schematic illustration of a pump head 27 of a ventricular assist device 20 including a thrust bearing 274, according to some applications of the present invention. For some applications, the thrust bearing 274 is disposed within the proximal bearing housing 116H adjacent to a proximal portion of the axial shaft 92. For some such applications, a flange 276 extends radially from the proximal portion of the axial shaft 92. For some applications, the thrust bearing is made of a ceramic material (e.g., zirconia). For some such applications, the flange 276 is coated with (or made of) a ceramic material (e.g., zirconia). Thus, the interface between the flange and the thrust bearing is a ceramic-ceramic interface. Typically, the flange is configured to contact the proximal thrust bearing. When the impeller pumps blood proximally, the axial shaft is urged distally. The thrust bearing prevents distal movement of the axial shaft by holding the flange in place, so that the axial shaft and impeller remain in an axially fixed position within the frame 34. For some applications, the thrust bearing 274 comprises a first portion of a molded element (e.g., a molded ceramic element), which defines a second portion that functions as the proximal radial bearing 116.

[0343] Reference is now made to Figures 17A, 17B, 17C, and 17D, which are schematic illustrations of the distal tip 120 of the ventricular assist device 20, according to some applications of the present invention. As noted above, the distal tip 120 typically forms a portion of the distal tip element 107, which also includes the axial shaft receiving tube 126. Typically, the distal tip element 107 is configured such that, in its unconstrained configuration (i.e., no forces acting on the distal tip), the distal tip element is at least partially curved. Referring to Figure 17A, for some applications, within a given plane, the distal tip element 107 has a proximal straight portion 346 (typically at least a portion of which comprises the axial shaft receiving tube 126). The proximal straight portion of the distal tip element 107 defines a longitudinal axis 348. The curved portion of the distal tip element 107 curves in a first direction away from the longitudinal axis 348, then passes through an inflection point and curves in the opposite direction relative to the longitudinal axis 348. For example, as shown in FIG. 17A , within the plane of the page, the distal tip element first curves toward the top of the page and then toward the bottom of the page. Typically, when shaped as shown in FIG. 17A , the distal tip element defines an overall curvature similar to a question mark or a tennis racket, with the distal tip element defining a bulge 351 on one side of the longitudinal axis of the straight proximal straight portion of the distal tip element. For some applications, the bulge is generally semi-elliptical. (Note that in this context, the term “semi-ellipse” includes a semicircle. Further, note that in some cases, the tip does not define an exact semi-ellipse, but rather defines a bulging shape substantially similar to a semi-ellipse.) Typically, the curvature of the curved portion of the distal tip element 107 is configured to provide an atraumatic tip for the ventricular assist device 20 when deployed within a subject's left ventricle. Further, typically, the distal tip element is configured to space the inlet opening 108 of the ventricular assist device from the wall of the left ventricle.

[0344] Referring now to Figures 17B and 17C, it should first be noted that these figures show a cross-sectional view of the left ventricle 22 with the septum 338 disposed on the left side of the page and the free wall 334 disposed on the right side of the page. In this view, the left atrium 359 and left atrial appendage 358 are visible above the left ventricle, and the right ventricle 340 is visible to the left of the left ventricle. It should be noted that the views of the aorta and left ventricle shown in Figures 17B and 17C differ from those shown, for example, in Figure 1B. Figure 1B is a schematic view provided for illustrative purposes and does not properly depict the scale and orientation of the ventricular assist device relative to the anatomy.

[0345] For some applications, the distal tip element 107 is configured to separate the blood inlet opening from the posterior wall of the subject's left ventricle when the distal tip element is positioned against the apex of the subject's left ventricle. Typically, the distal tip element is configured to separate the blood inlet opening from the septum of the subject's left ventricle when the distal tip element contacts the apex of the subject's left ventricle.

[0346] Typically, the distal tip element 107 is inserted into the left ventricle, resulting in the bulge 351 expanding toward the septum 338. When deployed in this configuration, in response to the distal tip element 107 being pressed against the apex (e.g., because the physician advances the device or in response to movement of the left ventricle), the blood inlet opening 108 is typically pushed toward the free wall 334 and away from the septum 338 (in the direction of the arrow shown in FIG. 17C ). This is typically because the proximal straight portion 346 rotates about the question-mark-shaped curved portion, as shown. However, when tips of other shapes are deployed in a similar orientation, the blood inlet opening may be pushed toward the septum. For example, if the distal tip element has a pigtail tip (the tip is bent in a single direction of curvature) oriented so that the pigtail curve is on the free wall side of the longitudinal axis of the straight portion of the distal tip element, pushing the tip distally will typically tighten the loop of the pigtail curve, thereby moving the blood inlet opening toward the septum. Notwithstanding the above, it should be noted that in some embodiments, the distal tip element 107 has a pigtail shape.

[0347] 17D, for some applications, in addition to the above-described curvature of the distal tip, the distal tip has an additional curvature in a different plane than the above-described curvature. Specifically, the distal tip includes a distal curved portion 349 as well as a proximal curved portion 350 that is not in the same plane as the distal curved portion. (The two planes are different in the sense that they are not parallel to each other.)

[0348] In some embodiments, the tip further comprises a straight section 353 proximal to the proximal curved section 350. The straight section 353 may be configured to receive the axial shaft while it rotates, as described above with reference to FIG. 17A for the straight section 346. Alternatively or additionally, a purge fluid may flow through the straight section 353. For some applications, once the purge fluid flows to the distal end of the distal tip, a valve 160 ( FIG. 15A , e.g., a duckbill valve) described herein prevents the purge fluid from flowing out the distal end of the distal tip.

[0349] In some embodiments, the angle between the distal end of the proximal curved portion and the axial shaft is between 100 degrees and 170 degrees. Alternatively or additionally, the angle between the distal end of the proximal curved portion and the plane on which the distal curved portion 349 lies is between 25 degrees and 65 degrees, for example, between 35 degrees and 55 degrees. For some applications, the angle between the distal end of the proximal curved portion and the plane on which the distal curved portion 349 lies is between 60 degrees and 120 degrees.

[0350] 17D, the proximal curved portion 350 may be curved toward the apex 342 of the left ventricle, also known as the apex of the heart. In other words, the proximal curved portion may be curved such that the distal end of the proximal curved portion (where the proximal curved portion meets the distal curved portion 349) points toward the apex 342 after the axial shaft is inserted through the aorta and into the left ventricle.

[0351] In some embodiments, distal to the proximal curved portion 350, the distal tip undergoes the aforementioned curvature in a second plane (i.e., a curvature resembling a question mark or the curvature of a tennis racket). In other words, the distal curved portion 349 includes a straight segment 355 (similar to the straight segment 346 in FIG. 17A ) defining a longitudinal axis, and a curved segment distal to the straight segment 355 that curves in a first direction relative to the longitudinal axis, passes through an inflection point, and curves in a second direction relative to the longitudinal axis, defining a bulge 351 on one side of the longitudinal axis. In other embodiments, the distal curved portion 349 has a pigtail shape. For some applications, the proximal and distal curved portions are continuous with each other. Typically, for such applications, the distal tip does not include the straight segment 355 between the proximal and distal curved portions.

[0352] Typically, lumen 122 (FIG. 15A) passes through proximal curve 350 and distal curve 349. Also typically, valve 160 (FIG. 15A) is located at the distal end of distal curve 349.

[0353] In some embodiments, the blood pump impeller rotates (i.e., the blood pump operates) while the distal curved portion 349 pushes against the apex 342. For some applications, the proximal curved portion is configured such that when the tip is pressed against the apex 342, even if the distal curved portion 349 curls, the tip bends around the proximal curved portion 350 such that the distal blood inlet opening 108 is still pushed toward the free wall 334 and away from the septum 338.

[0354] Reference is now made to Figure 18, which is a schematic illustration of a steering mechanism used to steer frame 34 relative to a piece of equipment disposed proximally thereto, in accordance with some applications of the present invention.

[0355] In some embodiments, one or more steering wires 301 are coupled to the frame 34 and configured to extend from the frame to outside the subject's body while the frame is in the body. In some embodiments, the steering wires 301 pass through the delivery tube 142. For example, the steering wires may be disposed between the drive cable bearing tube 140 and the delivery tube.

[0356] In some embodiments, one of the steering wires is coupled to the proximal end of the frame 34. Alternatively or additionally, one of the steering wires may be coupled to the distal end of the frame 34. This coupling may be via the proximal bearing housing 116H or the distal bearing housing 118H, i.e., the steering wire may be coupled to the frame by being coupled to either the proximal or distal bearing housing.

[0357] Typically, in such applications, the handle 149 of the ventricular assist device includes a steering control 300, and the steering wires are coupled to the steering control 300 so as to be controllable via the steering control.

[0358] Advantageously, the steering wires 301 may be configured to orient the frame, for example, prior to rotating the impeller to pump blood through a subject. For example, the steering wires may be configured to extend from the frame while the frame is within the left ventricle of the subject's heart, and the steering wires may be configured to orient the frame within the left ventricle, for example, so that the frame extends toward the apex of the left ventricle. The frame may be oriented by applying a force to a steering wire coupled to a proximal end of the frame and simultaneously applying a counter force to another steering wire coupled to a distal end of the delivery tube or frame.

[0359] In some such applications, the controller steers the proximal end of the frame relative to a portion of the device disposed proximally thereto, for example, to orient the distal end of the frame to extend toward the apex of the left ventricle. Typically, once the pump head is released within the left ventricle, the operator steers the proximal end of the frame in the manner described above to conform to the target anatomy (e.g., the shape of the left ventricle).

[0360] 9B, for some applications, the ventricular assist device includes optical fiber 228 for measuring blood pressure, which extends from the proximal end of the device to the proximal end of the frame, for example. In some applications, optical fiber 228 is also used as a steering wire, as described above. (In other words, the steering wires include the respective optical fibers.) In other embodiments, one or more of the steering wires include a stretch-resistant fiber, such as an aramid fiber.

[0361] Reference is now made to Figures 19A-B, which are schematic illustrations of an expandable element surrounding a delivery tube 142, in accordance with some applications of the present invention.

[0362] In some embodiments, an expandable element 314, such as an expandable stent, an expandable braided element, or an inflatable element 316 (e.g., balloon 114), surrounds the delivery tube 142 proximal to the blood outlet opening 109, and the length of the delivery tube between the expandable element 314 and the blood outlet opening is less than 30 mm. For example, the expandable element 314 may be disposed near the interface between the delivery tube 142 and the area where the proximal end of the pump outlet tube 24 is coupled to the delivery tube (as shown in FIG. 19A ).

[0363] In some embodiments, the expandable element 314 is entirely proximal to the pump outlet tubing, as shown in Figure 19A. In other embodiments, the expandable element 314 is an inflatable element 316 (e.g., balloon 114) that, when inflated, is at least partially, e.g., completely, disposed within the pump outlet tubing 24, as shown in Figure 19B.

[0364] Typically, the expandable element 314, whether configured as shown in Figures 19A, 19B (or 20A or 20B), is configured to center a portion of the ventricular assist device within the aorta (e.g., a portion of the delivery tube 142, specifically the portion of the delivery tube near the pump outlet tube 24) by contacting the aortic wall or, if the expandable element is within the pump outlet tube, by pressing the wall of the pump outlet tube against the aortic wall.

[0365] In some embodiments, the expandable element 314 is an inflatable element 316 that is shaped to direct blood through the blood outlet opening 109, as shown by the blood flow arrows 318 in Figure 19B. For example, the distal end of the expandable element may have a width that narrows as one moves distally, e.g., the distal end may be frusto-conical, such that blood is directed by the distal end of the expandable element through the blood outlet opening at an angle.

[0366] In some applications, the expandable element (e.g., balloon) is inflated using a fluid (e.g., a purge fluid) pumped through the ventricular assist device. For example, as shown in FIG. 19B , the wall of the delivery tube may be shaped to define one or more openings 320, and the expandable element 316 may surround the openings 320 such that fluid flowing from the delivery tube through the openings into the expandable element inflates the expandable element. This fluid may include a purge fluid that purges the interface between the axial shaft and a radial bearing that does not rotate with the axial shaft, distal to the openings 320.

[0367] It should be noted that the expandable element 314 may be combined with any of the embodiments of the pump outlet tube 24 described below with reference to Figures 33A-C.

[0368] As shown in FIG. 19A , for some applications, regardless of whether the ventricular assist device includes an expandable element 314, proximal to the pump outlet tubing's proximal conical section, the pump outlet tubing defines a tubular joint 45 through which the proximal end of the pump outlet tubing is joined (e.g., via adhesive) to the second, outer tubing 142 of the ventricular assist device. For some applications, the pump outlet tubing is manufactured using a single, continuous tube, with sections of the pump outlet tubing molded to define the tubular joint, the proximal conical section, the distal conical section, and the cylindrical central section. Typically, in such cases, the blood inlet and outlet openings are cut (e.g., laser cut) from the tube. For some applications, rather than molding the tube to define the proximal conical section and the tubular joint, the section of the tube that will form the proximal conical section and the tubular joint is first molded into a cylindrical shape (usually continuous with the cylindrical shape of the central section). Next, strips are cut (e.g., laser cut) from the tube at its proximal end, while other strips remain attached to and extend proximally from the central cylindrical section of the tube. The proximal ends of the strips are then bonded to the outer tube 142 of the ventricular assist device to define the conical section of the pump outlet tubing that defines the blood outlet opening. (In some applications, some of the blood outlet openings are laser cut from the tube, while other blood outlet openings are formed by bonding the strips to a second outer tube 142 of the ventricular assist device.) In some applications, using the latter method to form the conical section and blood outlet opening of the pump outlet tubing results in a thinner layer of the pump outlet tubing bonded to the outer tube 142 than the thickness of the tubular joint formed by the former method. In some applications, this reduces the abruptness of the diameter change at the interface between the outer tube 142 and the region where the proximal end of the pump outlet tubing is bonded to the outer tube.

[0369] In some applications, the pump outlet tubing is manufactured using a single continuous tube, with each section of the pump outlet tubing being molded to define a tubular joint, a proximal conical section, a distal conical section, and a cylindrical center section, similar to the former method described in the paragraph above, except that before bonding the tubular joint to the outer tubing 142 of the ventricular assist device, the tubular joint is cut (e.g., tapered) to reduce the thickness of the layer of pump outlet tubing that is bonded to the outer tubing 142 and / or to prevent creases in the tubular joint of the pump outlet tubing.

[0370] Typically, (a) the blood outlet opening 109 is defined by a portion of the wall of the blood outlet tubing that extends at least partially into the proximal cone of the pump outlet tubing, as shown, for example, in FIG. 19A , and / or (b) the blood outlet opening 109 is transversely oriented by being defined by a central cylindrical portion of the pump outlet tubing 24, as shown, for example, in FIG. 19B . (As noted above, a "transversely oriented blood outlet opening" should be interpreted to mean that the blood outlet opening is disposed transversely relative to the longitudinal axis of the pump outlet tubing by being defined by a central cylindrical portion of the pump outlet tubing. This is in contrast to blood inlet openings, typically described as "transversely oriented blood inlet openings," which are not oriented completely transversely relative to the longitudinal axis of the pump outlet tubing. Rather, they are disposed obliquely relative to the longitudinal axis of the pump outlet tubing.) Examples of each type of blood outlet opening are shown in the figures herein. The scope of the present disclosure includes combining other features of the pump outlet tubing and / or other portions of the ventricular assist device with any configuration of blood outlet openings described and / or shown herein.

[0371] Reference is now made to Figures 20A, 20B, 20C, and 20D, which are schematic illustrations of a ventricular assist device 20, in accordance with some applications of the present invention.

[0372] FIG. 20A is similar to FIG. 19B in that FIG. 20A illustrates an expandable element 314 disposed within the pump outlet tubing 24, typically near the blood outlet opening. For some such applications, the blood outlet opening is configured as described above. According to some applications, the expandable element is an inflatable element 316, e.g., balloon 114, as shown in FIG. 20A. For some applications, the balloon is inflated using purge fluid pumped through the ventricular assist device. Alternatively or additionally, the balloon is inflated by a separate fluid, e.g., a dedicated fluid for inflating the balloon (e.g., air or saline).

[0373] For some applications, the expandable element is configured to act as a blood flow director by directing blood from the proximal end of the pump outlet tubing through the blood outlet opening, as indicated by blood flow arrow 360. For some applications, the expandable element is shaped to direct blood flow in this manner. For example, the expandable element may have angled and / or curved surfaces configured to direct blood flow in this manner. For some applications, directing blood flow in this manner improves the overall pumping efficiency of the device compared to a device without the expandable element.

[0374] As described above, the expandable element 314 is typically configured to center a portion of the ventricular assist device (e.g., a portion of the delivery tube 142, specifically the portion of the delivery tube near the pump outlet tube 24) within the aorta by contacting the aortic wall or, if the expandable element is within the pump outlet tube, by pressing the wall of the pump outlet tube against the aortic wall.

[0375] 20B , in some applications, the expandable element 314 is a porous expandable element, such as an expandable cage or stent 172, that surrounds the delivery tube 142 at the interior or proximal end of the pump outlet tube, such that blood is pumped through the porous expandable element. For example, the porous expandable element may be disposed at the proximal end of the pump outlet tube, which may be coupled to the delivery tube 142 via the porous expandable element. In some such applications, the pump outlet tube does not define a blood outlet opening 109 ( FIG. 20A ). Rather, blood exits the pump outlet tube only through the porous expandable element, as indicated by blood flow arrows 174. In some applications, the porous expandable element comprises a structure made of a shape memory alloy, such as a laser-cut shape memory alloy and / or a braided shape memory alloy.

[0376] As described above, the porous expandable element is typically configured to center a portion of the ventricular assist device (e.g., a portion of the delivery tube 142, specifically the portion of the delivery tube near the pump outlet tube 24) within the aorta by contacting the aortic wall or, if the expandable element is within the pump outlet tube, by pressing the wall of the pump outlet tube against the aortic wall.

[0377] 20C , for some applications, a proximal portion 178 of the pump outlet tube 24, which defines the blood outlet opening 109, is bent inward toward the distal end of the pump outlet tube. Typically, as shown, the proximal portion 178 is bent inward so that the blood outlet opening directs blood proximally (substantially parallel to the axis of the outer tube 142) rather than radially outward (away from the axis of the outer tube 142), as indicated by blood flow arrows 362. For some applications, the proximal portion 178 is bent inward so that the blood outlet tube forms a protective layer between the blood exiting the blood outlet opening and the wall of the subject's aorta.

[0378] 20D, in some applications, the blood outlet opening 109 is not defined by a side of the pump outlet tubing, but rather by a generally proximally facing surface 190 of the pump outlet tubing. Typically, in such applications, blood flow from the pump outlet tubing is directed axially, as indicated by blood flow arrow 364.

[0379] Reference is now made to FIG. 20E, which is a schematic illustration of pump outlet tubing 24 defining a blood flow chamber 366 at its proximal end, according to some applications of the present invention. In some applications, the blood flow chamber is defined by an internal membrane 368 disposed within the proximal end of the pump outlet tubing and defining a hole 370 therethrough. Blood flows into the blood flow chamber through the hole, as indicated by blood flow arrow 372. The blood then flows out of the blood flow chamber, as indicated by blood flow arrow 374, and into the subject's aorta through blood outlet opening 109 (generally as described above). Typically, as blood flows through the blood flow chamber, the blood flow chamber expands to contact the aortic wall, thereby centering a portion of the left ventricular assist device (e.g., the delivery tubing, specifically the portion of the delivery tubing proximal to pump outlet tubing 24) within the aorta. Typically, the internal membrane is shaped to direct blood flow out of the blood outlet opening.

[0380] In some applications, the inner membrane 368 is an extension of the pump outlet tubing 24, and the inner membrane is covered by an outer membrane, which defines the blood outlet opening and forms the outer surface of the blood flow chamber 366. In such applications, the proximal end of the blood outlet tubing is shaped to direct blood flow out of the blood outlet opening.

[0381] Typically, the combination of the proximal end of the blood outlet tube and the additional membrane (either internal or external) is configured to define a blood flow chamber 366 that typically functions as described above. In general, the scope of the present disclosure includes any structure that provides a blood flow chamber disposed at the proximal end of the pump outlet tube, the blood flow chamber defining (a) a hole 370 through which blood enters the blood flow chamber and (b) a blood outlet opening 109 configured to be disposed within the aorta and through which blood exits the blood flow chamber and flows into the aorta.

[0382] Reference is now made to FIGS. 21A and 21B, which are schematic illustrations of a distal bearing housing 118H of a ventricular assist device 20, according to some applications of the present invention. For some applications, the bearing housing is constructed using a cylindrical tube 180 having substantially smooth outer and inner surfaces and a uniform thickness (i.e., without the varying thickness and surface areas described with reference to FIG. 11E). Typically, the cylindrical tube is made from an alloy or metal, such as cobalt chromium and / or stainless steel. For some applications, a coupling element 182 is coupled to the outer surface of the cylindrical tube, and the distal end of the frame 34 is coupled to the bearing housing via the coupling element. (For example, the distal end of the frame may be coupled to the coupling element via a snap-fit ​​mechanism.) For some applications, the distal bearing 118 itself comprises an inner cylindrical element coupled to the inner surface of the distal bearing housing. As noted above, the bearing is typically made from a ceramic material, such as zirconia. For some applications, a distal thrust bearing 270 is disposed within the distal bearing housing 118H, as shown. The distal thrust bearing is generally as described above. For some applications, the proximal bearing housing also comprises a cylindrical tube having substantially smooth outer and inner surfaces and a uniform thickness, as described mutatis mutandis for the distal bearing housing.

[0383] Reference is now made to Figures 22A, 22B, 22C, and 22D, which are schematic illustrations of portions of a ventricular assist device 20 including an inlet guard 400 disposed within a frame 34, in accordance with some applications of the present invention. The inlet guard 400 is shaped to define one or more holes 402, shown enlarged in Figure 22D, disposed about the axial shaft and within the frame 34 distal to the impeller, such that blood flows to the impeller through the holes 402. The inlet guard may be coupled to struts of the frame 34, the frame liner 39 (Figure 4), the inner wall of the pump outlet tube 24, and / or the distal bearing housing 118H.

[0384] In some applications, the inlet guard 400 is flat and / or disposed perpendicular to the axial shaft (i.e., the longitudinal axis of the frame). Advantageously, the inlet guard may therefore occupy relatively little space and / or provide a favorable flow direction for the blood. Typically, the inlet guard is annular.

[0385] As explained above (with reference to FIGS. 16A-E), for some applications, the ventricular assist device includes a thrust bearing in the pump head 27. Typically, in such applications, the impeller does not move distally of the cylindrical portion 38 of the frame 34 (during delivery of the device to the left ventricle or during operation of the device).

[0386] For some applications, the inlet guard is located within or near the distal end of the central barrel of the frame, for example, within 1 mm of the distal end of the barrel, which may simplify assembly of the blood pump.

[0387] Typically, the inlet guard is polymeric, i.e., made from a polymeric material (such as polyurethane (e.g., Pellethane®), polyethylene terephthalate ("PET"), ultra-high molecular weight polyethylene ("UHMWPE"), and / or polyether block amide (e.g., Pebax®)) that is molded to define the holes 402. In some applications, the inlet guard has a thickness greater than 40 microns (e.g., greater than 50 microns) and / or less than 100 microns (e.g., less than 80 microns), for example, between 40 and 100 microns or between 50 and 80 microns. Thus, the inlet guard may be configured to be crimpable while still being pressure resistant.

[0388] Typically, in applications in which the ventricular assist device 20 includes an inlet guard 400 disposed within the frame 34, the pump outlet tubing 24 does not extend to the distal end of the distal conical portion 40 of the frame 34. Alternatively, the pump outlet tubing 24 may have an open distal end rather than terminating at the distal conical portion. (Thus, the inlet guard may simplify manufacturing of the blood pump.) The distal end of the pump outlet tubing may be proximal to the distal end of the distal conical portion of the frame. For example, the distal end of the pump outlet tubing may be within 1 mm of the distal end of the central cylindrical portion of the frame 34; i.e., the pump outlet tubing may extend only to or near the end of the cylindrical portion of the frame 34. Thus, blood may enter the frame 34 through an opening defined by the distal conical portion of the frame.

[0389] For some applications, the holes 402 in the inlet guard 400 are sized to (a) allow blood to flow from the subject's left ventricle into the pump outlet tubing 24, and (b) prevent structures of the subject's left ventricle from entering the pump outlet tubing. Typically, for such applications, the inlet guard is configured to reduce the risk of left ventricular structures (such as chordae tendineae, trabeculae, and / or papillary muscles) entering the pump outlet tubing 24 and potentially being damaged by the impeller and / or axial shaft and / or damaging the ventricular assist device.

[0390] For some applications, the inlet guard 400 defines more than 10 holes, more than 50 holes, more than 100 holes, or more than 150 holes, e.g., 50-100 holes, 100-150 holes, or 150-200 holes. For some applications, the holes are sized to (a) allow blood to flow from the subject's left ventricle into the tube and (b) prevent structures of the subject's left ventricle from entering the frame. Typically, for such applications, the inlet guard is configured to reduce the risk of left ventricular structures (such as chordae tendineae, trabeculae, and / or papillary muscles) entering the cylindrical portion of the frame 34 and potentially being damaged by the impeller and / or axial shaft and / or damaging the left ventricular assist device. Thus, for some applications, the holes are shaped such that, for each hole, the span of the hole in at least one direction is less than 1 mm, e.g., 0.1-1 mm, or 0.3-0.8 mm. It is true that defining such a small width (or span) typically prevents left ventricular structures (such as chordae tendineae, trabeculae, and / or papillary muscles) from entering the cylindrical portion of frame 34.

[0391] For some applications, each of the holes defines an area of ​​more than 0.05 square mm (e.g., more than 0.1 or 0.3 square mm) and / or less than 5 square mm (e.g., less than 3 or 1 square mm), e.g., between 0.05 and 5, 0.05 and 3, 0.1 and 1, 0.1 and 5, or 0.3 and 1 square mm.

[0392] Typically, the inlet guard has a porosity of at least 40 percent, for example more than 50 percent or more than 60 percent (where porosity is defined as the percentage of the area of ​​this porous part that is open to blood flow). Thus, on the one hand, the holes are relatively small (to prevent left ventricular structures from entering the frame), but on the other hand, the porosity of the part defining the hole in the pump outlet tube is relatively high, allowing sufficient blood to enter the pump outlet tube.

[0393] For some applications, each of the holes has a circular or polygonal shape. For some applications, each of the holes has a hexagonal shape, as shown most clearly in Figure 22D. Typically, using openings with hexagonal shapes allows the inlet guard to have a relatively high degree of porosity (e.g., as described above), while providing sufficient material between the holes in the inlet guard to prevent tearing and / or stretching of the material.

[0394] As shown in FIG. 22D, in some applications, the gap width W2 between adjacent holes 402 (i.e., the distance between each pair of adjacent holes) is greater than 0.01 mm (e.g., greater than 0.04 mm) and / or less than 0.1 mm (e.g., less than 0.08 mm), for example, between 0.01 and 0.1 mm, or between 0.04 and 0.08 mm.

[0395] As further shown in FIG. 22D , in some applications, the distance D2 between each opposing side of a hexagon (or other type of polygon) is greater than 0.2 mm (e.g., greater than 0.4 mm) and / or less than 0.8 mm (e.g., less than 0.6 mm), e.g., 0.2 to 0.8 mm, or 0.4 to 0.6 mm. Typically, each polygon encloses a circle (i.e., structures that cannot pass through such a circle cannot pass through the polygon). Typically, the diameter of the circle enclosed by the polygon is equivalent to the distance D2, e.g., greater than 0.2 mm (e.g., greater than 0.4 mm) and / or less than 0.8 mm (e.g., less than 0.6 mm), e.g., 0.2 to 0.8 mm, or 0.4 to 0.6 mm.

[0396] For some applications, the frame is assembled with the inlet guard therein in the following manner: As described above, during assembly of the pump head, the proximal end of the frame 34 is generally open. For some applications, the inlet guard is supported on a rod (e.g., a mandrel) and placed through the open proximal end of the frame. The inlet guard typically has a generally torus shape, as shown in FIG. 22D , with the edges of the shape defining an inner circle and an outer circle. The inner circle defined by the inlet guard typically connects to the axial shaft (or distal bearing housing), and the outer circle connects to the struts of the frame 34, the pump outlet tube 24, and / or the lining 39. For some applications, the inlet guard is connected to other portions of the device using sutures, hooks, adhesives, and / or heat seals.

[0397] As mentioned above, in some embodiments, the inlet guard is coupled to a distal bearing housing, which may house the radial and / or thrust bearings. In such embodiments, the distal bearing housing is typically disposed partially or completely within the frame 34. For example, at least 10%, 50%, or 80% of the length of the bearing housing may be disposed within the frame. Also, in applications where the blood pump does not include the inlet guard 400, the distal bearing housing may extend into the frame.

[0398] For further details in this regard, reference is now made to Figure 23, which is a schematic illustration of ventricular assist device 20 in which distal bearing housing 118H is at least partially disposed within distal cone 40 of frame 34, i.e., extends at least partially proximally. Reference is also made to Figures 22A-C, which also show distal bearing housing 118H extending at least partially proximally within distal cone 40 of frame 34.

[0399] Typically, it is desirable for the total length of the relatively rigid portions of the pump head of the device (e.g., frame, impeller, and bearing housing) to be as short as possible to allow the device to safely pass through the curved vasculature of interest (e.g., the aortic arch). In some applications, configuring the device so that the distal bearing housing 118H extends at least partially into the distal cone of the frame 34 reduces the total length of the relatively rigid portions of the pump head of the device (e.g., frame, impeller, and bearing housing) compared to configuring the device so that the distal bearing housing 118H does not extend at least partially proximally into the distal cone of the frame 34.

[0400] In some embodiments, the bearing housing occupies at least 10% of the length of the distal conical portion of the frame. For some applications, the distal bearing housing also extends to or at least partially into the cylindrical portion 38 of the frame 34.

[0401] As described above, the distal bearing housing 118H houses radial and / or thrust bearings adjacent to the axial shaft and configured to stabilize the axial shaft (radially and / or axially) while it rotates. An advantage of the thrust bearings is that the impeller does not enter (or a portion of) the distal cone of the frame during operation of the device or during delivery of the device to the left ventricle (when the impeller is in a radially constrained configuration within the frame), which may facilitate configuring the distal bearing housing 118H to extend proximally within the distal cone of the frame 34. However, the scope of the present disclosure includes distal bearing housings that extend within the frame 34 as described above, but that house only the distal radial bearing 118H and not the thrust bearings.

[0402] Similarly, the proximal bearing housing, which houses radial and / or thrust bearings adjacent to the axial shaft and configured to stabilize the axial shaft (radially and / or axially) while the axial shaft rotates, may be partially or completely disposed within the proximal conical portion of the frame. For example, at least 10%, 50%, or 80% of the length of the proximal bearing housing may be disposed within the frame. Alternatively or additionally, the proximal bearing housing may occupy at least 10% of the length of the proximal conical portion of the frame; for example, the proximal bearing housing may be at least partially disposed within the cylindrical portion of the frame. The scope of the present disclosure includes a proximal bearing housing that extends within the frame 34 as described above, but houses only the proximal radial bearing 116 and not a thrust bearing.

[0403] In some embodiments, both the proximal and distal bearings extend within the frame as described above. In such embodiments, the distance between the proximal end of the proximal bearing housing and the distal end of the distal bearing housing may be less than 10% greater than the length of the frame, thereby reducing the overall length of the stiffer elements of the blood pump.

[0404] Reference is now made to FIG. 24 , which is a schematic illustration of a valve 160 disposed at the distal end of the lumen 122 of the distal tip 120, according to some applications of the present invention. As noted above, in some embodiments, the valve is a duckbill valve. In some applications, the duckbill valve is configured to facilitate guidewire insertion through both the distal end of the duckbill valve and the proximal end of the duckbill valve. In some applications, at both the proximal and distal ends, the valve narrows from a wide opening to a self-sealing center, guiding a guidewire from both ends of the valve toward the self-sealing center. Typically, a guidewire is inserted from the distal end of the distal tip to the distal tip before initially delivering the ventricular assist device over the guidewire into the left ventricle. In some cases, it may be desirable to insert a guidewire from the proximal end of the ventricular assist device to the distal end of the device at some subsequent stage. The shape of the duckbill valve shown in FIG. 24 typically facilitates both distal-to-proximal and proximal-to-distal insertion of a guidewire.

[0405] Reference is now made to FIGS. 25A-25B, which are schematic illustrations of a valve 99 disposed at the proximal end of a lumen 133 defined by a pin 131 of a driven magnet unit 310, according to some applications of the present invention. As noted above, in some embodiments, the valve is a duckbill valve. In some applications, the duckbill valve is configured to facilitate guidewire insertion through both the distal end of the duckbill valve and the proximal end of the duckbill valve. In some applications, at both the proximal and distal ends, the valve narrows from a wide opening to a self-sealing center, guiding a guidewire from both ends of the valve toward the self-sealing center. Typically, a guidewire is inserted from the distal end of the driven magnet unit through the valve 99 before initially delivering the ventricular assist device into the left ventricle over the guidewire. In some cases, it may be desirable to insert a guidewire from the proximal end of the ventricular assist device to the distal end of the device at some subsequent stage. The shape of the duckbill valve shown in FIGS. 25A-B typically facilitates both distal-to-proximal and proximal-to-distal insertion of a guidewire.

[0406] Reference is now made to Figures 26A and 26B, which schematically illustrate perspective and cross-sectional views, respectively, of a locking unit 279 for securing delivery tube 142 to delivery catheter 143, according to some applications of the present invention.

[0407] In some applications, it is desirable to lock the delivery tube 142 and the delivery catheter 143 in a fixed position relative to one another once the ventricular assist device has been deployed within the left ventricle and the delivery catheter has been retracted to its intraoperative position (e.g., so that its distal end is disposed within the descending aorta). In some applications, a locking unit, such as locking unit 97 (shown in FIG. 7D ), is used and is configured such that the position of the driven magnet unit is locked or unlocked relative to the proximal end of the delivery catheter by screwing in a portion of the locking unit. For example, the locking unit may include a Tuohy Borst adapter.

[0408] In other applications, instead of the fixation unit shown in FIG. 7D , a locking unit 279 configured to couple to the proximal end of the delivery catheter and including a clip 280 is used. In such applications, the delivery tube 142 extends from outside the subject's body into the left ventricle through the locking unit 279 and the delivery catheter 143. The clip 280 is configured to have only two states (or "positions"): a closed state (the clip grips the delivery tube and prevents movement of the delivery tube relative to the delivery catheter) and an open state (the clip does not grip the delivery tube). This differs from the fixation unit shown in FIG. 7D , which typically has varying degrees of closure depending on how tightly the screw mechanism is actuated. Because the clip 280 is typically an external component of the locking unit, the state of the clip 280 is easily visible to the user.

[0409] 26B, the locking unit typically includes at least one internal seal configured to surround the delivery tube and prevent backflow of the subject's blood from the delivery catheter through the locking unit while the delivery tube passes through the locking unit. For example, the locking unit may include a duckbill seal 282 and an additional seal 284.

[0410] Typically, as shown in FIG. 26B, the locking unit further includes a fluid port 281 and is shaped to define a channel 283 in fluid communication with the fluid port 281 and the delivery catheter 143. Thus, the channel 224 (FIG. 12A) between the delivery catheter and the delivery tube may be purged with a purge fluid. (Fluid port 281 and channel 283 may be collectively referred to as purge fluid inlet port 89, as shown in FIG. 26A and described above with reference to FIG. 7D.)

[0411] Reference is now made to Figures 27A and 27B, which schematically illustrate perspective and cross-sectional views, respectively, of a clip 286 for securing delivery tube 142 to delivery catheter 143, according to some alternative applications of the present invention.

[0412] In some embodiments, the clip is configured to remain in the open state after placement unless the clip is returned to the closed state, i.e., the locking mechanism can be released by opening the clip, without the user having to actively keep the locking mechanism released.

[0413] In other embodiments, the clip is configured to return to a closed position after deployment unless the clip is held open. In other words, the user must actively apply force to the clip to keep the locking mechanism unlocked. Clip 286 is an example of such a clip.

[0414] Reference is now made to Figures 28A and 28B, which schematically illustrate perspective and cross-sectional views, respectively, of another locking unit 287 for securing a delivery catheter 143 to an introducer sheath 290, in accordance with some applications of the present invention.

[0415] Typically, the delivery catheter 143 is inserted into the patient's vascular system from outside the subject's body via an introducer sheath 290 configured to extend from outside the subject's body into the subject's body. For example, the introducer sheath may be used to provide access to the subject's femoral artery, and the delivery catheter may be advanced from the femoral artery to the subject's left ventricle, as described above.

[0416] For some applications, the locking unit 287 is configured to couple to the proximal end of the introducer sheath 290, and the delivery catheter 143 is configured to pass through the locking unit 287 and the introducer sheath 290. The locking unit 287 includes a clip 288 that is used to secure the position of the delivery catheter relative to the introducer sheath (typically once the delivery catheter is positioned in a desired intraoperative location). The clip 288 is configured to have only two states (or "positions"): a closed state (where the clip grips the delivery tube and prevents movement of the delivery catheter relative to the introducer sheath) and an open state (where the clip does not grip the delivery catheter). This differs from a locking unit such as that shown in FIG. 7D , which typically has varying degrees of closure depending on how tightly the screw mechanism is actuated. Because the clip 288 is typically an external component of the locking unit 287, the state of the clip is easily visible to the user.

[0417] Typically, the locking unit 287 includes at least one internal seal 289 configured to surround the delivery catheter and prevent backflow of the subject's blood from the introducer sheath through the second locking unit while the delivery catheter is passing through the second locking unit.

[0418] Typically, the locking unit 287 further comprises a fluid port and is shaped to define a channel 291 in fluid communication with the fluid port and the introducer sheath 290. Thus, the space between the delivery catheter and the introducer sheath may be purged with a purge fluid.

[0419] In some embodiments, the clip 288 is configured to remain in the open state unless the clip is returned to the closed state after placing the second clip in the open state. In other embodiments, the clip is configured to return to the closed state unless the clip is held open after placing the clip in the open state.

[0420] Reference is now made to Figure 29, which is a schematic illustration of a left ventricular assist device, in accordance with some applications of the present invention.

[0421] In some embodiments, the proximal end of the pump outlet tube 24 is bent inward and angled relative to the longitudinal axis 324 of the pump outlet tube to define one or more surfaces 322 configured to direct blood through the blood outlet opening 109.

[0422] In some embodiments, surface 322 defines a protrusion 325, such as a frustoconical protrusion that narrows in width moving distally. Blood is directed through the blood outlet opening at an angle by protrusion 325. In such embodiments, protrusion 325 is typically distally coupled to a delivery tube.

[0423] Reference is now made to Figure 30, which is a schematic illustration of a ventricular assist device deployed within a subject, in accordance with some applications of the present invention.

[0424] In some embodiments, elongation-resistant fibers, such as aramid fibers 292 (which may be equivalent to fibers 159 shown in FIG. 13 ), run axially along the wall of delivery tube 142. The elongation-resistant properties of aramid fibers 292 cause the delivery tube to assume an orientation that minimizes the length of the aramid fibers. Thus, aramid fibers 292 bias the orientation of the delivery tube, and thereby the orientation of the blood pump, as the delivery tube traverses the aortic arch, typically by at least biasing the roll angle of the delivery tube. Typically, aramid fibers 292 bias the roll angle of the delivery tube so that the aramid fibers are disposed inside the curvature of the aortic arch, thereby minimizing the length of the aramid fibers. Typically, aramid fibers 292 extend to the distal end of the delivery tube.

[0425] In some embodiments, the aramid fibers 292 are disposed within the wall of the delivery tube (e.g., as in FIG. 13), as shown at the distal end of the delivery tube 294. For example, the wall of the delivery tube may include a braid, and the aramid fibers may be threaded through or run adjacent to the braid.

[0426] As described above, pump outlet tubing 24 is coupled to delivery tubing 142. Thus, in addition to biasing the blood pump, which is at least partially disposed within the pump outlet tubing, aramid fibers 292 bias the pump outlet tubing.

[0427] Typically, the pump outlet tubing is configured to curve within the left ventricle while the blood pump pumps blood from the left ventricle through the pump outlet tubing, as shown in Figure 30. For example, the blood pump may be at least partially disposed within a distal portion of the pump outlet tubing, and a proximal portion of the pump outlet tubing may be curved.

[0428] For example, the delivery tube may be configured to bend (even without the aramid fibers 292), and the bending of the delivery tube may cause the pump outlet tube to bend. Alternatively or additionally, the pump outlet tube may be configured to bend by being pre-formed. Alternatively or additionally, the pump outlet tube may be formed to define a plurality of openings (e.g., blood inlet openings and / or blood outlet openings) arranged in a non-axisymmetric arrangement, and the pump outlet tube may be curved by blood flowing through the openings. For some applications, the pump outlet tube is configured to bend by one or more features described with reference to Figures 19A-F of Tuval's US 2022 / 0226632, which is incorporated herein by reference. Alternatively or additionally, the pump outlet tube may be curved by one or more bands joined to the outer wall of the pump outlet tube, as described below with reference to Figure 31.

[0429] Depending on the curvature of the pump outlet tubing, the deflection properties of aramid may be particularly useful. For example, the aramid fibers may bias the orientation of the delivery tubing to curve away from the posterior wall of the left ventricle and / or the septum 338 while the delivery tubing crosses the aortic arch (and the aramid fibers bias the roll angle of the delivery tubing to be disposed inside the curvature of the aortic arch). Alternatively or additionally, the aramid fibers may bias the orientation of the delivery tubing to curve toward the apex 342 and / or free wall 334 of the left ventricle while the delivery tubing crosses the aortic arch (and the aramid fibers bias the roll angle of the delivery tubing to be disposed inside the curvature of the aortic arch).

[0430] In some embodiments, the circumferential angle between the aramid fibers and a circumferential location on the pump outlet tubing inside the bend in the pump outlet tubing is near zero, e.g., between -10 and 10 degrees. In other words, the aramid fibers are positioned on or near the inside of the bend, so that the delivery tubing bends in the same direction as the pump outlet tubing. This feature may further aid in orienting the blood pump in a desired direction.

[0431] As noted above, for some applications, the distal tip is configured to curve in a plane. For example, within a given plane, the distal tip may have a curvature as described above with reference to FIGS. 17A-C. For some applications, the plane about which the distal tip 120 curves is disposed at a roll angle theta relative to a (virtual) line extending from the distal end 292d of the aramid fiber (extending out of the page in distal end view 294). For some applications, the angle theta is between 25 and 65 degrees, e.g., between 35 and 55 degrees. Typically, the angle theta is selected so that, while the delivery tube traverses the aortic arch (and the aramid fiber biases the roll angle of the delivery tube to be disposed inside the curvature of the aortic arch), the plane about which the distal tip curves is oriented relative to the apex of the left ventricle such that the distal tip provides the distal tip function described above with reference to FIGS. 17A-C....

Claims

1. an axial shaft configured to be inserted into a ventricle of the subject's heart and to rotate within said ventricle; an impeller coupled to the axial shaft; a frame surrounding the impeller; a pump outlet tube surrounding the frame, the impeller forcing blood from the ventricle through the pump outlet tube proximally as the axial shaft rotates; an inlet guard shaped to define one or more holes, the inlet guard disposed about the axial shaft and within the frame distal to the impeller such that the blood flows through the holes to the impeller; A device comprising:

2. The device of claim 1 , wherein the pump outlet tube has an open distal end.

3. The device of claim 1 , further comprising a drive cable, the axial shaft coupled to the drive cable for rotation therewith.

4. The device of claim 1 comprising a drive cable, the axial shaft being a distal portion of the drive cable.

5. The apparatus of claim 1 , wherein the inlet guard is perpendicular to the axial shaft.

6. The apparatus of claim 1 , wherein the entrance guard is flat.

7. The apparatus of claim 1 , wherein the entrance guard is annular.

8. The apparatus of claim 1 , wherein the frame comprises a plurality of struts, and the entrance guard is connected to the struts.

9. The apparatus of claim 1 , wherein the inlet guard is coupled to an inner wall of the pump outlet tube.

10. 10. The apparatus of claim 1, further comprising a liner lining the inside of the frame, the entry guard being connected to the liner.

11. The device of claim 1 , wherein the entrance guard is made of a polymer.

12. 10. The apparatus of claim 1, wherein the entrance guard has a thickness of 40 to 100 microns.

13. 10. The device of claim 1, further comprising a thrust bearing disposed distally from the axial shaft, the thrust bearing preventing distal movement of the axial shaft beyond the thrust bearing.

14. 10. The device of claim 1, wherein the holes are shaped so that for each hole, the span of the hole in at least one direction is less than 1 mm.

15. The area of ​​each hole is 0.05 to 5 mm ２ 2. The device of claim 1, wherein:

16. 10. The apparatus of claim 1, wherein the inlet guard has a porosity of at least 40%.

17. The device of claim 1 , wherein each of the holes is hexagonal.

18. 2. The device of claim 1, wherein the distance between each pair of adjacent holes is 0.01 to 0.1 mm.

19. a bearing configured to stabilize the axial shaft while the axial shaft rotates; 19. The apparatus of claim 1, further comprising a bearing housing that houses the bearing and is coupled to the inlet guard.

20. 20. The apparatus of claim 19, wherein at least 10% of the length of the bearing housing is disposed within the frame.

21. 21. The apparatus of claim 20, wherein at least 50% of the length of the bearing housing is disposed within the frame.

22. 22. The apparatus of claim 21, wherein at least 80% of the length of the bearing housing is disposed within the frame.

23. 23. The apparatus of claim 22, wherein the bearing housing is disposed entirely within the frame.

24. 20. The device of claim 19, wherein the bearing comprises a thrust bearing disposed distally from the axial shaft and preventing distal movement of the axial shaft beyond the thrust bearing.

25. 19. The device of any one of claims 1 to 18, wherein the frame comprises a central cylindrical portion and a distal conical portion, and the entrance guard is disposed within 1 mm of the distal end of the central cylindrical portion.

26. 26. The device of claim 25, wherein the distal end of the pump outlet tube is proximal to the distal end of the distal cone.

27. 27. The device of claim 26, wherein the distal end of the pump outlet tube is within 1 mm of the distal end of the central cylindrical portion.

28. an axial shaft configured to be inserted into a body of a subject and to rotate within said body; an impeller coupled to the axial shaft to pump blood in the subject when the axial shaft rotates; a thrust bearing portion having a proximally facing ceramic surface disposed distally from the axial shaft to prevent distal movement of the axial shaft beyond the thrust bearing portion; a distally facing ceramic cover over the distal end of the axial shaft so as to contact the ceramic surface as the axial shaft rotates; A device comprising a blood pump comprising:

29. 30. The apparatus of claim 28, further comprising a drive cable, the axial shaft coupled to the drive cable for rotation therewith.

30. 30. The device of claim 28, further comprising a drive cable, the axial shaft being a distal portion of the drive cable.

31. 30. The apparatus of claim 28, wherein the thrust bearing portion comprises a ceramic piece with a ceramic surface facing in the proximal direction.

32. 29. The device of claim 28, wherein the thrust bearing portion is coated with a ceramic coating to provide a ceramic surface facing in the proximal direction.

33. 30. The device of claim 28, wherein the proximally facing ceramic surface comprises zirconia.

34. 30. The device of claim 28, wherein the distally facing ceramic cover comprises zirconia.

35. 36. The apparatus of any one of claims 28 to 35, wherein the blood pump further comprises a distal bearing housing that houses the distal thrust bearing, and a distal radial bearing housed within the distal bearing housing and configured to radially stabilize the axial shaft while it rotates.

36. 36. The device of any one of claims 28 to 35, wherein the axial shaft is configured to be inserted over a guidewire and is shaped to define a shaft lumen through which the guidewire passes, and the thrust bearing portion is shaped to define a bearing lumen configured to be continuous with the shaft lumen.

37. 37. The device of claim 36, wherein at least a portion of the bearing lumen is frustoconical, with a wider end of the bearing lumen facing distally.

38. 37. The device of claim 36, wherein the bearing lumen is a first bearing lumen, and the thrust bearing portion is further shaped to define at least one second bearing lumen configured to direct purge fluid through the second bearing lumen in a proximal direction to an interface between the axial shaft and the thrust bearing portion.

39. 36. The apparatus of any one of claims 28 to 35, wherein the blood pump comprises a ceramic cap that comprises the ceramic cover and fits around the distal end of the axial shaft.

40. 40. The apparatus of claim 39, wherein the blood pump comprises a distal radial bearing configured to radially stabilize the axial shaft while the axial shaft rotates, and the ceramic cap comprises a ceramic sleeve configured to cover a distal portion of the axial shaft that rotates within the distal radial bearing as the axial shaft rotates.

41. an axial shaft configured to be inserted into a subject's body over a guidewire and to rotate within the body, the axial shaft being shaped to define a shaft lumen through which the guidewire passes; an impeller coupled to the axial shaft to pump blood through the subject when the axial shaft rotates; a thrust bearing portion disposed distally from the axial shaft to prevent distal movement of the axial shaft beyond the thrust bearing portion, the thrust bearing portion shaped to define a bearing lumen configured to be continuous with the shaft lumen; A device comprising a blood pump comprising:

42. 42. The apparatus of claim 41, further comprising a drive cable, the axial shaft coupled to the drive cable for rotation therewith.

43. 42. The device of claim 41, further comprising a drive cable, the axial shaft being a distal portion of the drive cable.

44. 42. The device of claim 41, wherein at least a portion of the bearing lumen is frustoconical, with a wider end of the bearing lumen facing distally.

45. 42. The device of claim 41, wherein the bearing lumen is a first bearing lumen, and the thrust bearing portion is further shaped to define at least one second bearing lumen configured to direct purge fluid through the second bearing lumen in a proximal direction to an interface between the axial shaft and the thrust bearing portion.

46. 46. ​​The device of any one of claims 41 to 45, wherein the thrust bearing portion has a proximally facing ceramic surface, and the blood pump has a distally facing ceramic cover over the distal end of the axial shaft so as to contact the ceramic surface when the axial shaft rotates.

47. 47. The device of claim 46, wherein the thrust bearing portion comprises a ceramic piece with a ceramic surface facing in the proximal direction.

48. 47. The device of claim 46, wherein the thrust bearing portion is coated with a ceramic coating to provide a ceramic surface facing in the proximal direction.

49. 47. The device of claim 46, wherein the proximally facing ceramic surface comprises zirconia.

50. 47. The device of claim 46, wherein the distally facing ceramic cover comprises zirconia.

51. 47. The apparatus of claim 46, wherein the blood pump further comprises a distal bearing housing that houses the distal thrust bearing, and a distal radial bearing housed within the distal bearing housing and configured to radially stabilize the axial shaft while the axial shaft rotates.

52. 47. The apparatus of claim 46, wherein the blood pump further comprises a ceramic cap that fits around the distal end of the axial shaft and comprises the ceramic cover.

53. 53. The apparatus of claim 52, wherein the blood pump comprises a distal radial bearing configured to radially stabilize the axial shaft while the axial shaft rotates, and the ceramic cap comprises a ceramic sleeve configured to cover a distal portion of the axial shaft that rotates within the distal radial bearing as the axial shaft rotates.

54. an axial shaft configured to be inserted into a body of a subject and to rotate within said body; an impeller coupled to the axial shaft to pump blood through the subject when the axial shaft rotates; a frame surrounding the impeller and including a distal cone; a bearing portion adjacent to the axial shaft and configured to stabilize the axial shaft during rotation of the axial shaft; a bearing housing that houses the bearing and is at least partially disposed within the distal cone portion of the frame; A device comprising a blood pump comprising:

55. 55. The apparatus of claim 54, further comprising a drive cable, the axial shaft coupled to the drive cable for rotation therewith.

56. 55. The device of claim 54, further comprising a drive cable, the axial shaft being a distal portion of the drive cable.

57. 55. The device of claim 54, wherein the bearing housing occupies at least 10% of the length of the distal cone of the frame.

58. 55. The apparatus of claim 54, wherein the bearing comprises a radial bearing configured to radially stabilize the axial shaft while the axial shaft rotates.

59. 55. The apparatus of claim 54, wherein the bearing comprises a thrust bearing configured to axially stabilize the axial shaft while the axial shaft rotates.

60. 55. The device of claim 54, wherein the frame further comprises a cylindrical portion proximal to the distal conical portion, the bearing housing being at least partially disposed within the cylindrical portion.

61. 61. The apparatus of any one of claims 54 to 60, wherein at least 10% of the length of the bearing housing is disposed within the frame.

62. 62. The apparatus of claim 61, wherein at least 50% of the length of the bearing housing is disposed within the frame.

63. 63. The apparatus of claim 62, wherein at least 80% of the length of the bearing housing is disposed within the frame.

64. 64. The apparatus of claim 63, wherein the bearing housing is disposed entirely within the frame.

65. the bearing is a distal bearing, the bearing housing is a distal bearing housing, the frame further comprising a proximal cone; The blood pump further comprises: a proximal bearing portion adjacent the axial shaft proximally of the distal bearing portion and configured to stabilize the axial shaft during rotation of the axial shaft; 61. The device of any one of claims 54 to 60, comprising a proximal bearing housing that houses the proximal bearing and is at least partially disposed within the proximal cone portion of the frame.

66. 66. The device of claim 65, wherein at least 10% of the length of the proximal bearing housing is disposed within the frame.

67. 67. The device of claim 66, wherein at least 50% of the length of the proximal bearing housing is disposed within the frame.

68. 68. The device of claim 67, wherein at least 80% of the length of the proximal bearing housing is disposed within the frame.

69. 69. The device of claim 68, wherein the proximal bearing housing is disposed entirely within the frame.

70. 66. The apparatus of claim 65, wherein the proximal bearing comprises a proximal radial bearing configured to radially stabilize the axial shaft while the axial shaft rotates.

71. 66. The apparatus of claim 65, wherein the proximal bearing comprises a proximal thrust bearing configured to axially stabilize the axial shaft while the axial shaft rotates.

72. 66. The device of claim 65, wherein the frame further comprises a cylindrical portion between the proximal cone portion and the distal cone portion, and the proximal bearing housing is at least partially disposed within the cylindrical portion.

73. 66. The device of claim 65, wherein the distance between the proximal end of the proximal bearing housing and the distal end of the distal bearing housing is less than 10% greater than the length of the frame.

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