Ventricular assist device

Abstract

Apparatuses and methods including an impeller (50) are described, the impeller including a proximal hub (64) and a distal hub (58). Two or more helical elongate elements (52) extend from the proximal hub (64) to the distal hub (58), and an axial structure (54) is disposed inside the two or more helical elongate elements (52) and along an axis about which the helical elongate elements (52) are wrapped. The impeller (50) includes an impeller overexpansion prevention element (72). The impeller overexpansion prevention element is a single integrated structure including a ring (73) disposed about the axial structure (54), and a plurality of elongate elements (67), each elongate element (67) extending from the ring to a respective helical elongate element (52) and coupled to the respective helical elongate element (52) to prevent radial expansion of the impeller (50). Other applications are also described.

Description

[0001] Cross Reference to Related Applications

[0002] This application claims priority to the following applications:

[0003] U.S. Provisional Patent Application 63 / 006,122 to Tuval, filed April 7, 2020, entitled “Ventricular assist device”;

[0004] U.S. Provisional Patent Application 63 / 114,136 to Tuval, filed November 16, 2020, entitled “Ventricular assist device”;

[0005] U.S. Provisional Patent Application 63 / 129,983 to Tuval, filed December 23, 2020, entitled “Ventricular assist device”.

[0006] Each of the above-cited U.S. provisional applications is incorporated herein by reference.

[0007] Field of Embodiments of the Invention

[0008] Some applications of the present invention relate generally to medical devices. In particular, some applications of the present invention relate to ventricular assist devices and methods of using the same. BACKGROUND

[0009] Ventricular assist devices are mechanical circulatory support devices designed to assist a heart chamber and unload the heart chamber load to maintain or increase cardiac output. They are used for patients with heart failure and for patients at risk of worsening cardiac function during percutaneous coronary intervention. Most commonly, left ventricular assist devices are applied to a defective heart to assist left ventricular function. In some cases, right ventricular assist devices are used to assist right ventricular function. Such assist devices are either designed to be permanently implanted or mounted on a catheter for temporary placement.

[0010] SUMMARY OF EMBODIMENTS

[0011] According to some applications of the present invention, the blood pump includes an impeller. The impeller includes a proximal hub and a distal hub, and two or more helical elongate elements (and typically three helical elongate elements) extending from the proximal hub to the distal hub. An axial structure (e.g., a cylindrical axial structure, such as a spring) is disposed inside the two or more helical elongate elements and along an axis around which the helical elongate elements are wound. A film of material is supported between the helical elongate elements and the axial structure, such that each of the helical elongate elements with the film of material coupled thereto defines a respective blade of the impeller. A prevent impeller overexpansion element is disposed within the impeller. The prevent impeller overexpansion element is a single integrated structure that includes a ring disposed around the axial structure and a plurality of elongate elements. Each of the elongate elements extends from the ring to a respective helical elongate element and is coupled to the respective helical elongate element to prevent radial expansion of the impeller. Typically, the elongate elements are configured to not resist compression, and the elongate elements are configured to prevent radial expansion of the impeller by applying a pulling force to the helical elongate elements.

[0012] For some applications, along at least a portion of the length of the impeller, as the film of material transitions from one impeller blade to an adjacent blade, the film of material forms a continuous U-shaped curve, where the U-shaped curvature of the film of material is substantially uninterrupted at the axial structure. For some applications, when viewed from a distal end of the impeller, a pressure side of each blade of the impeller (i.e., the side configured to push against blood during operation of the impeller) is convex in a distal region of the impeller and is concave in a proximal region of the impeller. Typically, the pressure side of each blade of the impeller transitions to be substantially radially oriented in a region of the elongate element within the impeller blade.

[0013] For some applications, the impeller is manufactured by forming a structure having first and second hubs at a proximal end and a distal end of the structure, the first and second hubs connected to each other by at least one elongate element. The at least one elongate element is radially expanded and a helical elongate element is formed at least in part by axially compressing the structure. The at least one helical elongate element is coated with a coupling agent configured to enhance bonding between the helical elongate element and an elastomer layer. The coated helical elongate element is then coated with the elastomer layer. Subsequently, an elastomer film is coupled to the at least one helical elongate element such that the at least one helical elongate element with the elastomer film coupled thereto defines a blade of the impeller. For example, the helical elongate element can be dipped into an elastomer material from which the elastomer layer is made. For some applications, the elastomer film includes an elastomeric material having an ultimate elongation greater than 300%, a melt flow index of at least 4, and / or an ultimate tensile strength greater than 6000 psi.

[0014] For some applications, the impeller is driven in rotation by one or more drive magnets (coupled to a motor) that drive one or more driven magnets in rotation, and the driven magnets are coupled to the impeller via a drive cable. According to some applications of the present invention, a magnetic phase difference between the one or more driven magnets and the one or more drive magnets is measured, and a physiological parameter of the subject is determined at least partially in response to the measured magnetic phase difference. For example, based at least in part on changes in the phase difference, the computer processor can determine a difference between left ventricular pressure of the subject and aortic pressure of the subject, left ventricular pressure of the subject, an event in a cardiac cycle of the subject, cardiac afterload of the subject, and / or a different physiological parameter. For some applications, the physiological parameter is determined based on the phase difference measurement in combination with one or more additional measurements (e.g., magnetic flux amplitude measurements, power consumed by the motor, and / or current consumed by the motor). Typically, such measurements are combined in a mathematical model, e.g., a linear regression model, and / or a spatial state model.

[0015] For some applications of the present invention, during operation of a ventricular assist device used as a blood pump, arterial pulsations of the subject are measured, and a parameter is derived from the arterial pulsations of the subject. Typically, as the rotational rate of the impeller increases, the flow rate generated by the blood pump increases. Typically, the flow generated by the blood pump is non-pulsatile, as the blood pump is a continuous flow blood pump rather than a pulsatile blood pump. Thus, typically, as the rotational rate of the impeller increases and the flow rate generated by the blood pump increases, the arterial pulsations of the subject decrease. For some applications, the arterial pulsations of the subject are measured as a function of the rotational rate of the impeller. Based on the above measurements, a relationship between the arterial pulsations and the rotational rate of the impeller and / or the pump flow rate is derived. For some applications, based on the above relationship, the natural cardiac output of the subject is derived. For some such applications, when the arterial pulsations of the subject reach zero, the relationship between the arterial pulsations of the subject and the pump flow rate is extrapolated to determine what the pump flow rate would be. Presumably, at this value, the blood pump is replacing the intrinsic function of the heart, and the flow rate generated by the pump at this value provides an approximation of the natural cardiac output of the subject.

[0016] Thus, according to some applications of the present invention, there is provided an apparatus, the apparatus comprising:

[0017] a blood pump configured to be placed within a body of a subject, the blood pump comprising:

[0018] an impeller, the impeller comprising:

[0019] a proximal hub and a distal hub;

[0020] two or more helical elongated elements, the helical elongated elements extending from the proximal hub to the distal hub;

[0021] an axial structure disposed inside the two or more helical elongated elements and along an axis around which the helical elongated elements are wrapped; and

[0022] a film of material supported between the helical elongated elements and the axial structure, such that each of the helical elongated elements with the film of material coupled thereto defines a respective blade of the impeller; and

[0023] an impeller overexpansion prevention element that is a single integrated structure comprising a ring disposed around the axial structure,

[0024] each elongated element extending from the ring to a respective helical elongated element and coupled to the respective helical elongated element to prevent radial expansion of the impeller.

[0025] In some applications, the impeller includes three helical elongated elements, such that the three helical elongated elements with the film of material coupled thereto define three blades of the impeller, and a respective elongated element extends from the ring to each of the three helical elongated elements, such that there is a respective elongated element within each of the three blades of the impeller.

[0026] In some applications, the elongated elements are configured to not resist compression, and the elongated elements are configured to prevent radial expansion of the impeller by applying a pulling force to the helical elongated elements.

[0027] In some applications, along at least a portion of the length of the impeller, as the film of material transitions from one impeller blade to an adjacent blade, the film of material forms a continuous U-shaped curve, where the U-shaped curvature of the film of material is substantially uninterrupted at the axial structure.

[0028] In some applications, a pressure side of each blade of the impeller, which is configured to push against blood during operation of the impeller, is convex in a distal region of the impeller and concave in a proximal region of the impeller, when viewed from a distal end of the impeller. In some applications, the pressure side of each blade of the impeller transitions to be substantially radially oriented in a region of the elongated element within the impeller blade.

[0029] In some applications, the helical elongated elements are coated with a coupling agent configured to enhance bonding between the helical elongated elements and the film of material. In some applications, the film of material includes an elastomeric material, and the coupling agent includes at least two functional groups configured to bond with the helical elongated elements and the elastomeric material, respectively. In some applications, the coupling agent includes a silane compound.

[0030] In some applications, the apparatus further comprises a layer of elastomer disposed between the film of material and the coupling agent. In some applications, the layer of elastomer is configured to round the helical elongate elements. In some applications, the film of material is made of an elastomer. In some applications, the elastomer comprises a polycarbonate-based thermoplastic polyurethane.

[0031] In some applications, the axial structure comprises a spring. In some applications, the spring comprises a tube at a middle position along a length of the spring, and the ring is disposed around the tube.

[0032] Accordingly, in some applications according to the present invention, there is provided a method comprising:

[0033] manufacturing an impeller by:

[0034] forming a structure having first and second bushings at proximal and distal ends of the structure, the first and second bushings being connected to each other by at least one elongate element;

[0035] radially expanding the at least one elongate element and forming at least one helical elongate element, at least in part by axially compressing the structure;

[0036] coating the at least one helical elongate element with a coupling agent, the coupling agent being configured to enhance bonding between the helical elongate element and a layer of elastomer;

[0037] coating the coated helical elongate element with a layer of elastomer; and

[0038] subsequently coupling a film of elastomer to the at least one helical elongate element, such that the at least one helical elongate element with the film of elastomer coupled thereto defines a blade of an impeller.

[0039] In some applications, coupling the film of elastomer to the at least one helical elongate element such that the at least one helical elongate element with the film of elastomer coupled thereto defines a blade of an impeller comprises immersing the helical elongate element in an elastomeric material from which the film of elastomer is made.

[0040] In some applications, the film of elastomer comprises an elastomeric material having an ultimate elongation exceeding 300%. In some applications, the film of elastomer comprises an elastomeric material having a melt flow index of at least 4. In some applications, the film of elastomer comprises an elastomeric material having an ultimate tensile strength greater than 6000 psi.

[0041] In some applications, coating the at least one helical elongated element with a coupling agent includes coating the at least one helical elongated element with a silane compound, the silane compound containing a first functional group configured to bind with the helical elongated element and a second functional group configured to bind with the elastomer layer.

[0042] In some applications, the elastomer layer is made of a given elastomer material, and the elastomer film is made of the given elastomer material. In some applications, the elastomer layer is made of a first elastomer material, and the elastomer film is made of a second elastomer material different from the first elastomer material.

[0043] In some applications, coating the coated helical elongated element with the elastomer layer includes spraying the elastomer onto the coated helical elongated element. In some applications, coating the coated helical elongated element with the elastomer layer includes at least partially rounding the coated helical elongated element.

[0044] In some applications, coating the coated helical elongated element with the elastomer layer includes coating the coated helical elongated element with the elastomer layer within a given period of time of coating the at least one helical elongated element with the coupling agent. In some applications, coating the coated helical elongated element with the elastomer layer further includes, after coating the coated helical elongated element with the elastomer layer within the given period of time of coating the at least one helical elongated element with the coupling agent, spraying additional elastomer material onto the coated helical elongated element.

[0045] According to some applications of the invention, there is also provided an apparatus, the apparatus comprising:

[0046] A ventricular assist device, the ventricular assist device comprising:

[0047] An impeller configured to be placed within a left ventricle of a subject;

[0048] A motor;

[0049] At least one drive magnet coupled to the motor and configured to be rotated by the motor;

[0050] At least one driven magnet magnetically coupled to the drive magnet and configured to be rotated by the drive magnet;

[0051] A drive cable extending from the driven magnet and configured to transmit rotational motion from the driven magnet to the impeller;

[0052] A set of sensors configured to detect a magnetic phase difference between the driven magnet and the drive magnet; and

[0053] a computer processor configured to receive the detected magnetic phase difference and determine a physiological parameter of the subject at least partially in response to the detected magnetic phase difference.

[0054] In some applications, the set of sensors is further configured to measure a magnetic flux amplitude signal, and the computer processor is configured to determine the physiological parameter of the subject based at least in part on a combination of the magnetic flux amplitude signal and the detected magnetic phase difference.

[0055] In some applications, the computer processor is configured to determine a pressure difference between the left ventricle of the subject and the aorta of the subject at least partially in response to the magnetic phase difference between the driven magnet and the drive magnet. In some applications, the computer processor is configured to determine a left ventricular pressure of the subject at least partially in response to the magnetic phase difference between the driven magnet and the drive magnet. In some applications, the computer processor is configured to determine an event in a cardiac cycle of the subject at least partially in response to the magnetic phase difference between the driven magnet and the drive magnet.

[0056] In some applications, the set of sensors includes a first magnetometer configured to measure a magnetic phase of the driven magnet and a second magnetometer configured to measure a magnetic phase of the drive magnet. In some applications, the second magnetometer is configured to measure the magnetic phase of the drive magnet by measuring a magnetic phase of the motor.

[0057] In some applications, the computer processor is configured to receive a signal indicative of a current draw of the motor, and is configured to determine the physiological parameter of the subject based at least in part on a combination of the current draw of the motor and the detected magnetic phase difference. In some applications, the set of sensors is further configured to measure a magnetic flux amplitude signal, and the computer processor is configured to determine the physiological parameter of the subject based at least in part on a combination of the current draw of the motor, the magnetic flux amplitude signal, and the detected magnetic phase difference.

[0058] According to some applications of the invention, there is also provided an apparatus, comprising:

[0059] a ventricular assist device comprising an impeller configured to be placed within a left ventricle of a subject and configured to pump blood from the left ventricle of the subject to an aorta of the subject;

[0060] a blood pressure sensor configured to measure an aortic pressure of the subject;

[0061] a computer processor configured to:

[0062] derive an arterial pulsation of the subject based on the measured aortic pressure; and

[0063] Estimating the natural cardiac output of a subject based at least in part on arterial pulse estimation.

[0064] According to some applications of the invention, there is also provided an apparatus comprising:

[0065] A left ventricular assist device configured to assist left ventricular function of a subject, the left ventricular assist device comprising:

[0066] An impeller;

[0067] A frame disposed about the impeller,

[0068] A rigid axial shaft extending from a proximal end of the frame to a distal end of the frame, the impeller being coupled to the rigid axial shaft, and the rigid axial shaft comprising a proximal portion and a distal portion coupled to one another via a joint, the proximal portion and the distal portion being configured to bend relative to one another via the joint.

[0069] For some applications, the frame has a length exceeding 25 mm.

[0070] According to some applications of the invention, there is also provided an apparatus comprising:

[0071] An impeller comprising:

[0072] A proximal bushing and a distal bushing;

[0073] A plurality of helical elongated elements;

[0074] An axial structure disposed inside the helical elongated elements and along an axis about which the helical elongated elements are wound; and

[0075] A membrane of elastomeric material supported between the helical elongated elements and the axial structure, such that each helical elongated element with the membrane of elastomeric material coupled thereto defines a respective blade of the impeller,

[0076] Along at least a portion of the length of the impeller, as the membrane of elastomeric material transitions from one impeller blade to an adjacent blade, the elastomeric membrane forms a continuous U-shaped curvature, wherein the U-shaped curvature of the membrane of elastomeric material is substantially uninterrupted at the axial structure.

[0077] In some applications, the axial structure comprises a cylindrical axial structure. In some applications, the cylindrical axial structure comprises a spring.

[0078] According to some applications of the invention, there is also provided a method comprising:

[0079] Inserting a ventricular assist device through an arterial incision and into a subject's vasculature via an introducer sheath, the ventricular assist device comprising a delivery catheter, a drive cable, and an outer tube surrounding the drive cable;

[0080] Removing the introducer sheath while the ventricular assist device is still within the subject's vasculature; and

[0081] Maintaining sterility of the arterial incision using a sterile sleeve disposed between the outer tube and the delivery catheter while allowing movement of the outer tube relative to the delivery catheter.

[0082] According to some applications of the invention, there is also provided an apparatus, the apparatus comprising:

[0083] A blood pump, the blood pump comprising:

[0084] An axial shaft;

[0085] An impeller, the impeller being disposed on the axial shaft;

[0086] A motor unit, the motor unit comprising a motor, the motor being configured to drive the impeller to pump blood from a distal end of the impeller to a proximal end of the impeller by rotating the impeller in a given rotational direction;

[0087] A drive cable, the drive cable being configured to extend from the motor unit to the axial shaft, the drive cable being configured to transmit rotational motion from the motor to the impeller by rotation,

[0088] At least a portion of the drive cable comprises two or more layers, each layer comprising a plurality of wires,

[0089] The plurality of wires of each of the two or more layers is arranged in a coiled configuration, the coiled configuration being such that in response to the drive cable being rotated in the given rotational direction, the wires of each layer at least partially uncoil such that the portion of the drive cable axially shortens, and

[0090] The drive cable is maintained in a pre-tensioned state such that the drive cable is stretched relative to its resting state even when the impeller is in a resting state.

[0091] According to some applications of the invention, there is also provided an apparatus, the apparatus comprising:

[0092] A blood pump, the blood pump comprising:

[0093] An axial shaft;

[0094] An impeller, the impeller being disposed on the axial shaft;

[0095] a motor unit comprising a motor configured to drive the impeller so as to pump blood from the distal end of the impeller to the proximal end of the impeller by rotating the impeller in a clockwise direction when viewed from the proximal end of the impeller to the distal end of the impeller;

[0096] a drive cable configured to extend from the motor unit to the axial shaft, the drive cable being configured to transmit rotational motion from the motor to the impeller by rotation,

[0097] at least a portion of the drive cable comprises two or more layers, each layer comprising a plurality of wires,

[0098] the plurality of wires of each of the two or more layers are arranged in a left-hand lay configuration.

[0099] According to some applications of the present invention, there is also provided an apparatus comprising:

[0100] a blood pump comprising:

[0101] an axial shaft;

[0102] an impeller arranged on the axial shaft;

[0103] a motor unit comprising a motor configured to drive the impeller so as to pump blood from the distal end of the impeller to the proximal end of the impeller by rotating the impeller in a clockwise direction when viewed from the proximal end of the impeller to the distal end of the impeller;

[0104] a drive cable configured to extend from the motor unit to the axial shaft, the drive cable being configured to transmit rotational motion from the motor to the impeller by rotation,

[0105] at least a portion of the drive cable comprises two or more layers, each layer comprising a plurality of wires,

[0106] the plurality of wires of each of the two or more layers are arranged in a right-hand lay configuration.

[0107] According to some applications of the present invention, there is also provided an apparatus comprising:

[0108] a blood pump comprising:

[0109] an axial shaft;

[0110] an impeller arranged on the axial shaft;

[0111] a motor unit comprising a motor configured to drive the impeller so as to pump blood from the distal end of the impeller to the proximal end of the impeller by rotating the impeller in a given rotational direction;

[0112] a drive cable configured to extend from the motor unit to the axial shaft, the drive cable configured to transmit rotational motion from the motor to the impeller by rotation,

[0113] At least a portion of the drive cable comprises an inner layer and an outer layer coaxial to each other, and each layer comprises a plurality of wires arranged in a coiled configuration,

[0114] The ratio between the number of wires within the outer layer and the number of wires within the inner layer is between 2:3 and 2:5, and the ratio between the diameter of the wires within the outer layer and the diameter of the wires within the inner layer is between 3:2 and 5:2.

[0115] According to some applications of the present application, there is also provided an apparatus comprising:

[0116] a blood pump comprising:

[0117] an axial shaft;

[0118] an impeller arranged on the axial shaft;

[0119] a motor unit comprising a motor configured to drive the impeller so as to pump blood from a distal end of the impeller to a proximal end of the impeller by rotating the impeller in a given rotational direction;

[0120] a drive cable configured to extend from the motor unit to the axial shaft, the drive cable configured to transmit rotational motion from the motor to the impeller by rotation; and

[0121] a drive cable support tube in which the drive cable is configured to rotate, at least a portion of the drive cable support tube comprising:

[0122] an inner layer and an outer layer, the inner layer and the outer layer comprising respective materials different from each other; and

[0123] a coiled wire embedded between the inner layer and the outer layer, the coiled wire configured to maintain a substantially circular cross-section of the drive cable support tube even within areas in which the drive cable support tube undergoes substantial bending.

[0124] In general, in the specification and claims of the present application, when the term "proximal" and related terms are used with respect to a device or a portion thereof, the term "proximal" and related terms are to be interpreted to mean that an end of the device or the portion thereof is generally closer to the location through which the device is inserted into the body of a subject when the device or the portion thereof is inserted into the body of a subject. When the term "distal" and related terms are used with respect to a device or a portion thereof, the term "distal" and related terms are to be interpreted to mean that an end of the device or the portion thereof is generally further from the location through which the device is inserted into the body of a subject when the device or the portion thereof is inserted into the body of a subject.

[0125] The scope of the present application includes the use of the devices and methods described herein in anatomical locations other than the left ventricle and the aorta. Thus, ventricular assist devices and / or portions thereof are sometimes referred to herein (in the specification and claims) as blood pumps.

[0126] The present application will be more fully understood from the following detailed description of embodiments of the application, taken in conjunction with the accompanying drawings, in which: BRIEF DESCRIPTION OF DRAWINGS

[0128] FIG. 1A 、 FIG. 1B 、 FIG. 1C and FIG. 1D are schematic views of ventricular assist devices according to some applications of the present application, the distal end of which is configured to be placed in the left ventricle of a subject;

[0129] FIG. 1E and FIG. 1F are schematic views of ventricular assist devices according to some applications of the present application, comprising a braided structure and / or mesh in the distal region, configured to separate the blood inlet opening of the ventricular assist device from the internal structure of the ventricle;

[0130] FIG. 2 is a schematic view of a frame housing the impeller of a ventricular assist device according to some applications of the present application;

[0131] FIG. 3A 、 FIG. 3B 、 FIG. 3C 、 FIG. 3D 、 FIG. 3E and FIG. 3F are schematic views of an impeller of a ventricular assist device according to some applications of the present application, or portions thereof;

[0132] FIG. 3Gi and FIG. 3Gii are pictures of an impeller of a ventricular assist device according to some applications of the present application;

[0133] FIG. 4 is a schematic view of an impeller disposed inside the frame of a ventricular assist device according to some applications of the present application;

[0134] FIG. 5A and FIG. 5B are schematic views of an impeller and frame of a ventricular assist device according to some applications of the present application, respectively in a non-radially constrained state and in a radially constrained state;

[0135] FIG. 6A and FIG. 6Bis a schematic view of a ventricular assist device according to some applications of the present invention in a phase of the movement cycle of the impeller of the ventricular assist device relative to the frame of the ventricular assist device;

[0136] FIG. 6C is a schematic view of a distal end element of a ventricular assist device according to some applications of the present invention, the distal end element comprising an axial shaft receiving tube and a distal end portion;

[0137] FIG. 6D and 6E is a schematic view of a coupling element for coupling to the impeller bushing according to some applications of the present invention, the coupling element extending proximally and serving as a stop;

[0138] FIG. 7A is a schematic view of a motor unit of a ventricular assist device according to some applications of the present invention;

[0139] FIG. 7Bi and FIG. 7Bii is a schematic view of a motor unit of a ventricular assist device according to some applications of the present invention;

[0140] FIG. 8A is a chart representing the length of the drive cable of a ventricular assist device as measured in an experiment as a function of the pressure gradient against which the impeller of the blood pump is opposed;

[0141] FIG. 8B and FIG. 8C is a chart representing the results of a magnetic phase measurement performed on a blood pump as a function of the pressure gradient against which the impeller of the blood pump is opposed as measured in an experiment;

[0142] FIG. 9A , FIG. 9B , FIG. 9C , FIG. 9D , FIG. 9E , FIG. 9F and FIG. 9G is a schematic view of a motor unit support configured to support the motor unit on the leg of a patient according to some applications of the present invention;

[0143] FIG. 10A , FIG. 10B and FIG. 10C is a schematic view of a drive cable of a ventricular assist device according to some applications of the present invention;

[0144] FIG. 10D is a schematic view of a drive cable support tube according to some applications of the present invention;

[0145] FIG. 11A , FIG. 11B , FIG. 11C , FIG. 11D andFIG. 11E This is a schematic diagram of an apparatus and method for cleaning drive cables, radial supports, and / or impeller bushings of a ventricular assist device according to some applications of the present invention;

[0146] FIG. 12A and FIG. 12B This is a schematic diagram of a ventricular assist device according to some applications of the present invention, the ventricular assist device including an inner liner located on the inside of a frame housing an impeller;

[0147] FIG. 13 This is a schematic diagram of a ventricular assist device according to some applications of the present invention, the ventricular assist device having a frame that houses an impeller, the frame defining a cylindrical portion, at least the distal portion of which is not covered;

[0148] FIG. 14 This is a schematic diagram of a ventricular assist device placed in the left ventricle of a subject according to some applications of the present invention, wherein a cross-sectional view of the left ventricle is shown;

[0149] FIG. 15A , FIG. 15B , FIG. 15C and FIG. 15D This is a schematic diagram of a distal end element of a ventricular assist device according to some applications of the present invention, which is at least partially bent to define a question mark shape or a tennis racket shape;

[0150] FIG. 16A and FIG. 16B This is according to some applications of the present invention. FIG. 15D A schematic diagram of a ventricular assist device, which is placed in the left ventricle of a subject;

[0151] FIG. 17Ai and FIG. 17Aii This is a schematic diagram of a ventricular assist device according to some applications of the present invention, which has a balloon disposed on its distal end portion, the balloon being configured to facilitate movement of an axial shaft relative to the wall of the ventricle;

[0152] FIG. 17Bi and FIG. 17Bii This is a schematic diagram of a ventricular assist device according to some applications of the present invention, the ventricular assist device having a connector configured to facilitate pivoting of a distal end portion of the ventricular assist device relative to an axial shaft of the ventricular assist device;

[0153] FIG. 17C This is a schematic diagram of a ventricular assist device according to some applications of the present invention. The outer tube of the ventricular assist device is shaped with a predetermined curvature such that when the axial shaft is placed in the left ventricle of the subject, the axial shaft of the ventricular assist device remains in a substantially straight configuration.

[0154] FIG. 17D is a schematic view of a ventricular assist device having a distal tip configured to anchor to tissue of a left ventricular apex;

[0155] FIG. 18A , FIG. 18B and FIG. 18C are schematic views of a distal radial support of a ventricular assist device according to respective applications of the present invention;

[0156] FIG. 19A , FIG. 19B , FIG. 19C , FIG. 19D and FIG. 19E are schematic views of a ventricular assist device according to some applications of the present invention, the ventricular assist device comprising a pump outlet tube configured to become curved when blood is pumped through the pump outlet tube, the pump outlet tube being rotatable relative to a distal tip portion of the ventricular assist device;

[0157] FIG. 19F is a schematic view of a ventricular assist device according to some applications of the present invention, the ventricular assist device comprising a curved element made of a shape memory material and configured to provide a predetermined curvature to a portion of the ventricular assist device, the curved element being rotatable relative to a distal tip portion of the ventricular assist device;

[0158] FIG. 20A , FIG. 20B and FIG. 20C are schematic views of a ventricular assist device according to some applications of the present invention, an axial shaft of the ventricular assist device comprising a joint, e.g. a universal joint;

[0159] FIG. 21 is a schematic view of a ventricular assist device according to some applications of the present invention comprising one or more blood pressure measurement tubes;

[0160] FIG. 22A and FIG. 22B are schematic views of a sterile sleeve according to some applications of the present invention, the sterile sleeve being configured to form a seal between a delivery catheter and an outer tube of a ventricular assist device;

[0161] FIG. 23A , FIG. 23B and FIG. 23C are schematic views of a tip straightener for straightening a distal tip when inserting a guide wire into a distal tip of a ventricular assist device according to some applications of the present invention; and

[0162] FIG. 24A , FIG. 24B and FIG. 24Cis a graph showing measurements performed during use of a left ventricular assist device according to some applications of the present invention.

[0163] Detailed Description of Embodiments

[0164] Reference is now made to FIG. 1A , FIG. 1B and FIG. 1C which are schematic illustrations of a ventricular assist device 20 according to some applications of the present invention, the distal end of the ventricular assist device being configured to be disposed in the left ventricle 22 of a subject. FIG. 1A An overview of a ventricular assist device system including a console 21 and a motor unit 23 is shown. (As described below, typically the motor unit is a handle that houses a motor.) FIG. 1B A ventricular assist device inserted into the left ventricle of a subject is shown, and FIG. 1C A pump portion 27 of the ventricular assist device is shown in more detail. The ventricular assist device includes a pump outlet tube 24 that passes through the aortic valve 26 of the subject, such that a proximal end 28 of the pump outlet tube is disposed in the aorta 30 of the subject and a distal end 32 of the pump outlet tube is disposed within the left ventricle 22. The pump outlet tube 24 is typically an elongate tube, typically having an axial length that is substantially greater than its diameter. The scope of the present invention includes use of the devices and methods described herein in anatomical locations other than the left ventricle and aorta. Thus, the ventricular assist device and / or portions thereof are sometimes referred to herein (in the specification and claims) as a blood pump.

[0165] For some applications, the ventricular assist device is used to assist the function of the left ventricle of a subject during a percutaneous coronary intervention. In this case, the ventricular assist device is typically used for a period of up to 10 hours (e.g., up to 6 hours) during which there is a risk of hemodynamic instability (e.g., during or immediately following a percutaneous coronary intervention). Alternatively or additionally, the ventricular assist device is used to assist the function of the left ventricle of a subject for a longer period of time (e.g., 2-20 days, e.g., 4-14 days) in a patient suffering from cardiogenic shock, which can include any low cardiac output state (e.g., acute myocardial infarction, myocarditis, cardiomyopathy, post-partum, etc.). For some applications, the ventricular assist device is used to assist the function of the left ventricle of a subject for an even longer period of time (e.g., weeks or months), e.g., in a "bridge to recovery" therapy. For some such applications, the ventricular assist device is permanently or semi-permanently implanted, and the impeller of the ventricular assist device is percutaneously powered, e.g., using an external antenna that is magnetically coupled to the impeller.

[0166] As shown in FIG. 1B ,FIG. 1B Steps of deploying a ventricular assist device in the left ventricle are shown, typically the distal end of the ventricular assist device is guided to the left ventricle by a guide wire 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 guide wire is withdrawn from the subject’s body. Typically, the retraction of the delivery catheter causes the self-expanding component of the distal end of the device to assume a non-radially constrained configuration, as described in further detail below. Typically, the ventricular assist device is inserted into the subject’s body in order to provide acute treatment to the subject. For some applications, in order to withdraw the left ventricular device from the subject’s body at the end of the treatment, the delivery catheter is advanced over the distal end of the device, which causes the self-expanding component of the distal end of the device to assume a radially constrained configuration. Alternatively or additionally, the distal end of the device is retracted into the delivery catheter, which causes the self-expanding component of the distal end of the device to assume a radially constrained configuration.

[0167] For some applications (not shown), the ventricular assist device and / or the delivery catheter 143 comprise an ultrasound transducer at their distal end, and the ventricular assist device is advanced towards the subject’s ventricle under ultrasound guidance.

[0168] Reference is now made to FIG. 1C which shows the pump portion 27 of the ventricular assist device 20 in further detail. Typically, the impeller 50 is disposed within a distal segment 102 of the pump outlet tube 24, and is configured to pump blood from the left ventricle into the aorta by rotation. The pump outlet tube typically defines one or more blood inlet openings 108 at the distal end 32 of the pump outlet tube, via which blood flows from the left ventricle into the pump outlet tube during operation of the impeller. For some applications, the proximal segment 106 of the pump outlet tube defines one or more blood outlet openings 109, via which blood flows from the pump outlet tube into the ascending aorta during operation of the impeller.

[0169] For some applications, a control console 21, typically comprising a computer processor 25 (as shown, for example, in FIG. 1A controls the rotation of the impeller. For example, the computer processor can control a motor 74 (as shown, for example, in FIG. 7A which is disposed within a motor unit 23 (as shown, for example, in FIG. 1A which is disposed within a motor unit 23 (as shown, for example, in FIG. 7AThe impeller is driven to rotate. For some applications, the computer processor is configured to detect a physiological parameter of the subject (e.g., left ventricular pressure, cardiac afterload, rate of change of left ventricular pressure, etc.) and to control the rotation of the impeller in response thereto, as described in further detail below. Typically, the operations described herein as being performed by a computer processor convert the physical state of memory into having different magnetic polarity, charge, etc., according to the memory technology used, the memory being a real physical article of manufacture in communication with the computer processor. The computer processor 25 is typically a hardware device programmed with computer program instructions to produce a special purpose computer. For example, when programmed to perform the techniques described herein, the computer processor 25 typically acts as a special purpose ventricular assist computer processor and / or a special purpose blood pump computer processor.

[0170] For some applications, a cleaning system 29 (shown in FIG. 1A ) drives fluid (e.g., a glucose solution) through portions of the ventricular assist device 20, e.g., to cool portions of the device and / or to flush debris from portions of the device. The cleaning system 29 is described in further detail below.

[0171] Typically, along the distal segment 102 of the pump outlet tube 24, the frame 34 is disposed within the pump outlet tube around the impeller 50. The frame is typically made of a shape memory alloy, e.g., Nitinol. For some applications, the shape memory alloy of the frame is shaped such that, in the absence of any force being applied to the distal segment 102 of the tube 24, at least a portion of the frame (and thus the distal segment 102 of the tube 24) assumes a substantially circular, elliptical, or polygonal cross-sectional shape. By assuming its substantially circular, elliptical, or polygonal cross-sectional shape, the frame is configured to hold the distal portion of the pump outlet tube in an open state. Typically, during operation of the ventricular assist device, the distal portion of the pump outlet tube is configured to be placed within the body of the subject such that the distal portion of the pump outlet tube is at least partially disposed within the left ventricle.

[0172] For some applications, a frame is not disposed within the pump outlet tube along a proximal segment 106 of the pump outlet tube 24, and thus the pump outlet tube is not supported in an open state by the frame 34. The pump outlet tube 24 is typically made of a collapsible material that is impermeable to blood. For example, the pump outlet tube 24 can comprise polyurethane, polyester, and / or silicone. Alternatively or additionally, the pump outlet tube is made of polyethylene terephthalate (PET) and / or polyether block amide (e.g., PEBAX®). For some applications (not shown), the pump outlet tube is reinforced with a reinforcing structure, such as a braided reinforcing structure, such as a braided nitinol tube. Typically, the proximal portion of the pump outlet tube is configured to be placed such that it is disposed at least partially within the subject’s ascending aorta. For some applications, the proximal portion of the pump outlet tube passes through the subject’s aortic valve, from the subject’s left ventricle into the subject’s ascending aorta, as shown in FIG. 1. FIG. 1B

[0173] As noted above, the pump outlet tube typically defines one or more blood inlet openings 108 at a distal end of the pump outlet tube, through which blood flows from the left ventricle into the pump outlet tube during operation of the impeller. For some applications, the proximal portion of the pump outlet tube defines one or more blood outlet openings 109, through which blood flows from the pump outlet tube into the ascending aorta during operation of the impeller. Typically, the pump outlet tube defines a plurality of blood outlet openings 109, for example, between two blood outlet openings and eight blood outlet openings (e.g., between two blood outlet openings and four blood outlet openings). The pressure of the blood flow through the pump outlet tube typically maintains the proximal portion of the tube in an open state during operation of the impeller. For some applications, for example, in the event of a failure of the impeller, the proximal portion of the pump outlet tube is configured to collapse inwardly in response to a pressure outside the proximal portion of the pump outlet tube exceeding a pressure within the proximal portion of the pump outlet tube. In this way, the proximal portion of the pump outlet tube acts as a safety valve, preventing blood flow from the aorta into the left ventricle in reverse.

[0174] Referring again to FIG. 1C For some applications, the frame 34 is shaped such that the frame defines a proximal tapered portion 36, a central cylindrical portion 38, and a distal tapered portion 40. Typically, the proximal tapered portion is such that the narrow end of the taper is proximal relative to the wide end of the taper. More typically, the distal tapered portion is such that the narrow end of the taper is distal relative to the wide end of the taper. For some applications, the pump outlet tube 24 extends to a distal end of the cylindrical portion 38 (or slightly proximal or distal thereto), such that the distal end of the pump outlet tube defines a single axially-facing blood inlet opening 108, as shown in FIG. 1. FIG. 1C For some applications, the inner liner 39 lines the frame 34 at least along a portion of the frame, as described below with reference to FIG. 12A-FIG. 12B ​The inner liner partially overlaps or completely overlaps the pump outlet tube 24 over the portion of the frame that is lined by the inner liner, depending on the respective application. For such applications, the distal end of the inner liner defines a single axially facing blood inlet opening 108. For some applications, both the pump outlet tube and the inner liner terminate before the distal end of the cylindrical portion of the frame, such that a distal portion of the cylindrical portion of the frame is uncovered, as described below with reference to FIG. 13 The inner liner partially overlaps or completely overlaps the pump outlet tube 24 over the portion of the frame that is lined by the inner liner, depending on the respective application. For such applications, the distal end of the inner liner defines a single axially facing blood inlet opening 108. For some applications, both the pump outlet tube and the inner liner terminate before the distal end of the cylindrical portion of the frame, such that a distal portion of the cylindrical portion of the frame is uncovered, as described below with reference to

[0175] Typically, the pump outlet tube 24 comprises a conical proximal portion 42 and a cylindrical central portion 44. (Typically, the conical proximal portion 42 is disposed entirely within the proximal segment 106 described above, and the cylindrical central portion typically extends from within the proximal segment 106 to the distal segment 102.) The proximal conical portion is typically such that the narrow end of the cone is proximal relative to the wide end of the cone. Typically, a blood outlet opening 109 is defined by the pump outlet tube 24, such that the opening extends at least partially along the proximal conical portion 42 of the tube 24. For some such applications, the blood outlet opening is teardrop-shaped, as shown in FIG. 1C Typically, the teardrop-shaped nature of the blood outlet opening is combined with the opening extending at least partially along the proximal conical segment of the tube 24, such that blood flows out of the blood outlet opening at the location of the blood outlet opening along streamlines that are substantially parallel to the longitudinal axis of the tube 24.

[0176] For some applications (not shown), the diameter of the pump outlet tube 24 varies along the length of the central portion of the pump outlet tube, such that the central portion of the pump outlet tube has a frustoconical shape. For example, the central portion of the pump outlet tube can widen from its proximal end to its distal end, or can narrow from its proximal end to its distal end. For some applications, at its proximal end, the central portion of the pump outlet tube has a diameter of between 5 mm and 7 mm, and at its distal end, the central portion of the pump outlet tube has a diameter of between 8 mm and 12 mm.

[0177] Referring again to FIG. 1C , the ventricular assist device typically comprises a distal tip element 107 that is disposed distally relative to the frame 34 and comprises an axial shaft receiving tube 126 and a distal tip portion 120, which are described in further detail below.

[0178] Referring now to FIG. 1D , FIG. 1Dis a schematic view of a ventricular assist device 20 according to some applications of the present application, in which the pump outlet tube 24 extends to the end of the distal tapered portion 40 of the frame, and the pump outlet tube defines a plurality of lateral blood inlet openings 108. For such applications, the pump outlet tube typically defines a distal tapered portion 46 in which the narrow end of the taper is distal relative to the wide end of the taper. For some such applications, the pump outlet tube defines two to four lateral blood inlet openings. Typically, for such applications, each blood inlet opening 108 defines an area that is 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., 20-60 square millimeters or 30-50 square millimeters. Alternatively or additionally, the outlet tube defines a larger number of smaller blood inlet openings (not shown), e.g., 10 or more small blood inlet openings, 50 or more small blood inlet openings, 100 or more small blood inlet openings, or 150 or more small blood inlet openings, e.g., 50-100 small blood inlet openings, 100-150 small blood inlet openings, or 150-200 small blood inlet openings. For some such applications, each small blood inlet opening defines an area that is greater than 0.1 square millimeters (e.g., greater than 0.3 square millimeters) and / or less than 5 square millimeters (e.g., less than 1 square millimeter), e.g., 0.1-5 square millimeters, 0.2-0.5 square millimeters, or 0.3-1 square millimeters.

[0179] Typically, the distal tapered portion 46 of the pump outlet tube is configured to reduce the risk of structures from the left ventricle (e.g., chordae tendinae, papillary muscles, and / or papillary muscle) entering the frame and possibly being damaged by the impeller and / or the axial shaft (on which the impeller is mounted) and / or causing damage to the left ventricular assist device. Thus, for some applications, the small blood inlet openings are shaped such that the width (or span) of the openings 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 small widths (or spans), it is typically the case that structures from the left ventricle (e.g., chordae tendinae, papillary muscles, and / or papillary muscle) are prevented from entering the frame. For some applications, the small blood inlet openings define a generally rectangular (or elliptical) shape. For some such applications, the length to width ratio of the small blood inlet openings is between 1.1 : 1 and 4: 1, e.g., between 3:2 and 5:2. For some applications, by having such a shape, the small blood inlet openings are configured to (a) prevent structures from the left ventricle (e.g., chordae tendinae, papillary muscles, and / or papillary muscle) from entering the frame, but (b) provide a portion of the pump outlet tube defining the small blood inlet openings that has a relatively high porosity. Typically, the portion of the pump outlet tube defining the small blood inlet openings has a porosity that is greater than 40%, e.g., greater than 50% (where porosity is defined as the percentage of the area of the portion that is porous for blood flow).

[0180] Reference is now made to FIG. 1E and FIG. 1F , FIG. 1E and FIG. 1F is a schematic illustration of a ventricular assist device 20, which, according to some applications of the present application, includes a braided structure 260 and / or a mesh 282 in a distal region of the device, the braided structure and / or mesh being configured to separate a blood inlet opening of the ventricular assist device from an internal structure of the ventricle. The braided structure 260 is typically substantially similar to the braided structure 260 described with respect to US 2019 / 0209758 to Tuval, which is incorporated herein by reference. The mesh 282 is substantially similar to the mesh 282 described with respect to US 2019 / 0209758 to Tuval, which is incorporated herein by reference. FIG. 20B FIG. 21 D, which is incorporated herein by reference.

[0181] Reference is now made to FIG. 1E , for some applications, a braided structure 260 (e.g., of braided metal or alloy, such as shape memory alloy (e.g., Nitinol)) is disposed in a distal region of the device. For example, the braided material can be disposed at a distal end of the device. Alternatively or additionally, the device can include a distal tip element 107 (which is typically as described with reference to FIG. 14-FIG. 16B , and the braided material is disposed around a portion of the device so as to cover a portion of the distal tip element. For some applications, the braided material is disposed over at least a portion of the frame 34. For example, the braided material can be disposed around a portion of the frame that extends distally from at least one longitudinal location along the frame at which the blood outlet tube 24 ends and / or the inner liner 39 ends, up to a distal end of the frame. For some applications, the braided structure is disposed so as to cover the blood inlet opening 108.

[0182] As shown in FIG. 1F , for some applications, an outer surface of the distal tip element 107 includes a radially expandable mesh 282 configured to self-expand when the distal tip element 107 is disposed within the left ventricle of a subject. For some applications, the device includes a distal tip element substantially as described with reference to FIG. 14-FIG. 16B , and the mesh is disposed around a portion of the device so as to cover a portion of the distal tip element. For some applications, the mesh is disposed over at least a portion of the frame 34. For example, the mesh can be disposed around a portion of the frame that extends distally from at least one longitudinal location along the frame at which the blood outlet tube 24 ends and / or the inner liner 39 ends, up to a distal end of the frame. For some applications, the mesh is disposed so as to cover the blood inlet opening 108. ​

[0183] Typically, the braided structure 260 and / or the mesh 282 separates the one or more blood inlet openings 108 from the three-dimensional interior structure of the left ventricle. In this way, the braided structure 260 and / or the mesh 282 separates the one or more blood inlet openings 108 from the interventricular septum, chordae tendineae, papillary muscles, the trabeculae carneae, and / or the apex of the left ventricle. As an alternative or in addition to the braided structure and / or the mesh for separating the one or more blood inlet openings 108 from the interior structure of the left ventricle, the cells of the frame 34 in the vicinity of the blood inlet openings 108 are configured to define openings that are smaller than the openings in other portions of the frame. For example, the cells in the distal conical portion of the frame are capable of defining openings that are smaller than the openings defined by the cells in the proximal conical portion of the frame. Alternatively or additionally, the cells in the distal conical portion of the frame are capable of defining openings that are smaller than the openings defined by the cells in the cylindrical portion of the frame.

[0184] Reference is now made to FIG. 2 , FIG. 2 is a schematic illustration of a frame 34 that houses an impeller of a ventricular assist device 20, in accordance with some applications of the present application. As described hereinabove, the frame 34 is typically made of a shape memory alloy, such as Nitinol, and the shape memory alloy of the frame is shaped such that the frame (and thus the tube 24) assumes a generally circular, elliptical or polygonal cross-sectional shape in the absence of any force being applied to the pump outlet tube 24 and / or the frame 34. By assuming its generally circular, elliptical or polygonal cross-sectional shape, the frame is configured to hold the distal portion of the tube in an open state.

[0185] Typically, the frame is a stent-like frame, in that it comprises struts that in turn define cells. More typically, the frame is covered by the pump outlet tube 24, and / or is covered by the inner liner 39, as described hereinbelow with reference to FIG. 12A-FIG. 12B As described hereinbelow, for some applications, the impeller 50 undergoes axial reciprocating motion relative to the frame 34. Typically, during the motion of the impeller relative to the frame, the portion of the impeller that defines the impeller maximum span is disposed within the cylindrical portion 38 of the frame 34. In some cases, if the cells of the cylindrical portion 38 of the frame 34 are too large, the pump outlet tube 24 and / or the inner liner 39 is stretched between the edges of the cells, such that the pump outlet tube 24 and / or the inner liner 39 does not define a circular cross-section. For some applications, if this occurs in the area in which the portion of the impeller that defines the impeller maximum span is disposed, this results in a non-constant gap between the edges of the impeller blades and the tube 24 (and / or the inner liner) at that location during the impeller rotation cycle. For some applications, this can result in increased hemolysis, as compared to a situation in which there is a constant gap between the edges of the impeller blades and the tube 24 (and / or the inner liner) at that location during the impeller rotation cycle.

[0186] Reference is made to FIG. 2 , at least in part in view of the problems described in the previous paragraph, within the cylindrical portion 38 of the frame 34, the frame defines a large number of relatively small cells. Typically, when the frame is disposed in its non-radially constrained configuration, the maximum cell width CW of each cell within the cylindrical portion of the frame (i.e., the distance, as measured around the circumference of the cylindrical portion 38, from the inner edge of the strut at the central junction on one side of the cell to the inner edge of the strut at the central junction on the other side of the cell) is less than 2 mm, for example between 1.4 mm and 1.6 mm, or between 1.6 and 1.8 mm. Due to the relatively small cells, the pump outlet tube 24 (and / or the inner liner) defines a substantially circular cross-section within the cylindrical portion of the frame.

[0187] Still referring to FIG. 2 , and starting from the proximal end of the frame (on the left side of the figures), the frame typically defines the following portions: (a) a coupling portion 31 via which the frame is coupled to a proximal support 116 of the ventricular assist device (shown in FIG. 4 ), (b) a proximal tapered portion 36, (c) a cylindrical portion 38, (d) a distal tapered portion 40, and (e) a distal strut junction 33. As shown, as the frame transitions from the proximal end of the frame to the center of the frame (e.g., as the frame passes through the coupling portion 31, through the proximal tapered portion 36, and transitions to the cylindrical portion 38), the struts 37 of the frame pass through junctions 35 at which two struts branch off from a single strut in a Y-shaped shape. As described in further detail below, typically, the frame 34 is placed in a radially constrained (i.e., crimped) configuration in the delivery catheter 143 by the frame being axially elongated. Moreover, typically, the frame transfers its radial narrowing to the impeller, and the impeller becomes radially constrained by being axially elongated within the frame. For some applications, the struts of the frame configured in the manner described above facilitate the transfer of axial elongation from the delivery catheter (or other device configured to crimp the frame) to the frame, which in turn facilitates the transfer of axial elongation to the impeller. This is because the pairs of struts branching off from each junction 35 are configured to pivot around the junction and move close to each other, thereby closing.

[0188] Still referring to FIG. 2 , for some applications, when the frame is coupled to the axial shaft 92 (shown in FIG. 4 ), the distal strut junction 33 is not circumferentially connected and is typically configured to remain in an open state in order for the impeller to be placed within the frame via the distal end of the frame. Subsequently, the distal strut portion closes around the outside of the distal support 118, as described in further detail below with reference to FIG. 5A-FIG. 5B . For some applications, the proximal end of the distal tip element 107 (as shown in FIG. 1CThe distal strut portions are held in their closed configuration about the outside of the distal support 118.

[0189] Typically, the frame 34 has a total 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, when disposed in its non-radially constrained configuration. Typically, the length of the frame increases by 2 to 5 mm when disposed in its radially constrained configuration (within the delivery catheter 143). Typically, the cylindrical portion of the frame 34 has a length 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, when disposed in its non-radially constrained configuration. For some applications, the ratio of the length of the cylindrical portion of the frame to the total length of the frame is greater than 1 :4 and / or less than 1 :2, e.g., between 1 :4 and 1 :2.

[0190] Reference is now made to FIG. 3A-FIG. 3C , FIG. 3A-FIG. 3C is a schematic illustration of an impeller 50 or portion thereof according to some applications of the present application. Typically, the impeller includes at least one outer helical elongated element 52 that is wrapped around a central axial spring 54 such that the helical structure defined by the helical elongated element is coaxial with the central axial spring. (As described in further detail below, typically, the central axial spring includes a tube 70 at an intermediate position along its length. Also, as described below, the scope of the present application includes the use of other axial structures in place of a spring. Thus, in some aspects, the present application is directed to an "axial structure 54".) Typically, the impeller includes two or more helical elongated elements (e.g., three helical elongated elements, as shown in FIG. 3A-FIG. 3C 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 support a film 56 of a material (e.g., an elastomer such as polyurethane, and / or silicone). For some applications, the film of material includes a Nitinol sheet embedded therein, e.g., in order to reinforce the film of material. For illustrative purposes, the impeller is shown in FIG. 3A without the film of material. FIG. 3B and FIG. 3C respectively show perspective views of the impeller with the film of material supported between the helical elongated elements and the spring.

[0191] 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 an outer edge of the blade and the axial spring defining an axis of the impeller. Typically, the membrane of material extends along and wraps around the spring. For some applications, a suture 53 (e.g., a polyester suture, such as FIG. 3B and FIG. 3C shown) is wrapped around the helical elongate element, e.g., as described in US 10,864,310 to Schwammenthal, which is incorporated herein by reference. Typically, the suture is configured to facilitate bonding between the membrane of material (which is typically an elastomer, e.g., polyurethane, or silicone) and the helical elongate element (which is typically a shape memory alloy, e.g., nitinol). For some applications, a suture (e.g., a polyester suture, not shown) is wrapped around the spring 54. Typically, the suture is configured to facilitate bonding between the membrane of material (which is typically an elastomer, e.g., polyurethane, or silicone) and the spring (which is typically a shape memory alloy, e.g., nitinol).

[0192] FIG. 3C Magnified views A and B of FIG. 5 show two alternative ways in which the suture is tied around the helical elongate element 52. For some applications, the suture is tied around the outer surface of the helical elongate element, as shown in magnified view A. Alternatively, the helical elongate elements define grooves 45 on their outer surfaces, and the suture is embedded within the grooves, as shown in magnified view B. Typically, by embedding the suture within the grooves, the suture does not add to the outer profile of the impeller, and the outer profile of the impeller is defined by the outer surfaces of the helical elongate elements.

[0193] Typically, the proximal end of the spring 54 and the proximal end of the helical elongate element 52 extend from a proximal bushing (i.e., sleeve bearing) 64 of the impeller, such that the proximal end of the spring 54 and the proximal end of the helical elongate element 52 are disposed at approximately the same location and have a similar radial distance from the longitudinal axis of the impeller. Similarly, typically, the distal end of the spring 54 and the distal end of the helical elongate element 52 extend from a distal bushing 58 of the impeller, such that the distal end of the spring 54 and the distal end of the helical elongate element 52 are disposed at approximately the same location and have a similar radial distance from the longitudinal axis of the impeller. Typically, the spring 54, as well as the proximal and distal bushings 64, 58 of the impeller, define a cavity therethrough, such that the impeller defines a continuous cavity 62 therethrough (as shown in FIG. 3C FIG. 6).

[0194] Reference is now made to FIG. 4FIG. 3 is a schematic view of an impeller 50 disposed within a frame 34 of a ventricular assist device 20, in accordance with some applications of the present application. For some applications, within at least a portion of the frame 34, an inner liner 39 lines the frame, as described below with reference to FIG. 4. Depending on the respective application, the inner liner partially or completely overlaps the pump outlet tube 24 over the portion of the frame that is lined by the inner liner. For some applications, both the pump outlet tube and the inner liner terminate before the distal end of the cylindrical portion 38 of the frame, such that a distal portion of the cylindrical portion of the frame is uncovered, as described below with reference to FIG. 5. For some applications, the pump outlet tube continues to cover the distal conical portion of the frame, as described below with reference to FIG. 6. For some applications, the inner liner lines the cylindrical portion of the frame, and the pump outlet tube 24 does not cover the cylindrical portion of the frame, as shown in FIG. 7. However, the scope of the present application includes applying the apparatus and methods described with reference to FIG. 4 to any one of the applications described with reference to FIGS. 5, 6, or 7. FIG. 12A-FIG. 12B FIG. 13 FIG. 1D FIG. 4 FIG. 4 FIG. 1D FIG. 12A-FIG. 12B FIG. 13

[0195] FIG. 4 As shown, typically, there is a gap G between the outer edge of the impeller 50 and the inner liner 39, even at the location where the impeller spans are the largest. For some applications, it is desirable for the gap between the outer edge of the blades of the impeller and the inner liner 39 to be relatively small, so that the impeller effectively pumps blood from the left ventricle of the subject into the aorta of the subject. However, it is also desirable for the gap between the outer edge of the blades of the impeller and the inner surface of the frame 34 to remain substantially constant throughout the rotation of the impeller within the frame 34, e.g., so as to reduce the risk of hemolysis.

[0196] ​​​​​​​​​For some applications, when both the impeller and the frame 34 are set to their non-radially-constrained configurations, the gap G between the outer edge of the impeller and the inner liner 39 at the location of the impeller span 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., 0.05-1 mm, or 0.1-0.4 mm. For some applications, when the impeller is set to its non-radially-constrained configuration, the outer diameter of the impeller at the location of the impeller outer diameter 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., 7-10 mm, or 8-9 mm. For some applications, when the frame 34 is set to its non-radially-constrained configuration, the inner diameter of the frame 34 (measured from the inner side of the inner liner 39 on one side of the frame to the inner side of the inner liner on the opposite side of the frame) 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., 7.5-10.5 mm, or 8.5-9.5 mm. For some applications, when the frame is set to its non-radially-constrained configuration, the outer diameter of the frame 34 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., 8-13 mm, or 9-12 mm.

[0197] Typically, the axial shaft 92 passes through the axis of the impeller 50 via the cavity 62 of the impeller. More typically, the axial shaft is rigid, e.g., a rigid tube. (For some applications, at least a portion of the axial shaft is at least partially flexible, e.g., as described with reference to FIG. 20A-FIG. 20C For some applications, the proximal bushing 64 of the impeller is coupled to the shaft 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. The axial shaft is itself radially stabilized via the proximal radial bearing 116 and the distal radial bearing 118. In turn, the axial shaft radially stabilizes the impeller relative to the inner surface of the frame 34 such that, during rotation of the impeller, even a relatively small gap (e.g., a gap as described above) between the outer edges of the blades of the impeller and the inner surface of the frame 34 is maintained.

[0198] Again with reference to FIG. 3A-FIG. 3CFor 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 67 are typically flexible, but substantially inelastic along an axis defined by the elongated elements 67. Further typically, each of the elongated elements 67 is configured to be substantially inelastic against compression. Instead, each elongated element 67 is configured to exert a tensile force 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 elements 67) the spacing between the helical elongated element 52 and the central axial spring 54 would be greater than the length of the elongated elements 67. For example, the elongated elements 67 can include a cord (e.g., a polyester, and / or another polymer or natural material that includes fibers) and / or a wire (e.g., a nitinol wire, and / or a wire made of a different alloy or metal). In this way, the elongated elements prevent the impeller from expanding radially by exerting a tensile force on the helical elongated element.

[0199] For some applications, the elongated elements 67 hold the helical elongated element 52 (which defines the outer edge of the blades of the impeller) within a given distance relative to the central axial spring 54. In this way, the elongated elements 67 are configured to prevent the outer edge of the impeller from being forced radially outward due to forces exerted on the impeller during rotation of the impeller. In other words, the elongated elements 67 act as an anti-expansion element for the impeller. The elongated elements 67 are thereby configured to maintain a gap between the outer edge of the blades of the impeller and the inner surface of the frame 34 during rotation of the impeller. Typically, more than one (e.g., more than two) and / or fewer than eight (e.g., fewer than four) elongated elements 67 are used in the impeller, where each elongated element 67 is typically doubled back (i.e., extending radially from the central axial spring 54 to the outer edge of the helical elongated element 52, and then back from the helical elongated element to the central axial spring). For some applications, the plurality of elongated elements 67 are formed from a single cord or a single wire, where each elongated element 67 extends from the spring to a respective helical elongated element 52 and back to the central axial spring 54.

[0200] For some applications, the impeller is manufactured in the following manner. The proximal bushing 64, the distal bushing 58, and the helical elongated elements 52 are cut from a tube of shape memory material (e.g., Nitinol). The cutting of the tube and the setting of the shape memory material is typically performed in such a way that the helical elongated elements and the bushings are defined by a tube of shape memory material that is cut and set, for example, using techniques generally similar to those described in US 10,039,874 to Schwammenthal. Typically, the spring 54 is inserted into the cut and set tube such that the spring extends along the length of the tube at least from the proximal bushing to the distal bushing. For some applications, the spring is inserted into the cut and set tube when the spring is in an axially compressed state, and the spring is configured to remain 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. For some applications, the spring is cut from a tube of shape memory material (e.g., Nitinol). For some such applications, the spring is configured such that when the spring is disposed in a non-radially constrained configuration (in which the spring is typically disposed during operation of the impeller), there is substantially no gap between a turn of the spring and its adjacent turn.

[0201] For some applications, after the spring 54 is inserted into the cut and set tube, elongated elements 67 as described above are placed to extend between the spring and one or more of the helical elongated elements 52, for example, in the following manner. A mandrel (e.g., a polyether ether ketone (PEEK) and / or a polytetrafluoroethylene (PTFE) mandrel) is inserted through the cavity defined by the spring and the bushings. A cord or wire is then threaded in such a way that the cord or wire (a) passes from the mandrel to a first one of the helical elongated elements 52, (b) returns from the first one of the helical elongated elements 52 to the mandrel, (c) passes around the mandrel, and to a second one of the helical elongated elements 52, (d) returns from the second one of the helical elongated elements 52 to the mandrel, and so on. Once the cord or wire has been threaded from the mandrel to each of the helical elongated elements 52 and back again, the ends of the cord or wire are coupled to one another, for example, by tying them to one another. For some applications, a separate cord or wire is used for each of the helical elongated elements 52. Typically, each cord or wire is threaded from a helical elongated element around the mandrel and back to the helical elongated element, the two ends of the cord being tied to one another. For some applications, as shown, at a longitudinally central location of the spring 54, the spring is shaped to define a tube 70 (i.e., at that location the spring does not define a turn), and the cord or wire is wrapped around that tube. For some applications, the cord or wire is not wrapped around that tube, and does not pass through the longitudinal axis of the impeller. Rather, the cord or wire is secured relative to the tube 70 by a securing element 75 (e.g., a loop), as described in further detail below. FIG. 3F For some applications, after the spring 54 is inserted into the cut and set tube, elongated elements 67 as described above are placed to extend between the spring and one or more of the helical elongated elements 52, for example, in the following manner. A mandrel (e.g., a polyether ether ketone (PEEK) and / or a polytetrafluoroethylene (PTFE) mandrel) is inserted through the cavity defined by the spring and the bushings. A cord or wire is then threaded in such a way that the cord or wire (a) passes from the mandrel to a first one of the helical elongated elements 52, (b) returns from the first one of the helical elongated elements 52 to the mandrel, (c) passes around the mandrel, and to a second one of the helical elongated elements 52, (d) returns from the second one of the helical elongated elements 52 to the mandrel, and so on. Once the cord or wire has been threaded from the mandrel to each of the helical elongated elements 52 and back again, the ends of the cord or wire are coupled to one another, for example, by tying them to one another. For some applications, a separate cord or wire is used for each of the helical elongated elements 52. Typically, each cord or wire is threaded from a helical elongated element around the mandrel and back to the helical elongated element, the two ends of the cord being tied to one another. For some applications, as shown, at a longitudinally central location of the spring 54, the spring is shaped to define a tube 70 (i.e., at that location the spring does not define a turn), and the cord or wire is wrapped around that tube. For some applications, the cord or wire is not wrapped around that tube, and does not pass through the longitudinal axis of the impeller. Rather, the cord or wire is secured relative to the tube 70 by a securing element 75 (e.g., a loop), as described in further detail below.

[0202] For some applications, at this stage, sutures 53 (e.g., polyester sutures) are wrapped around the helical long elements 52 in order to facilitate bonding between a membrane of material (which is typically an elastomer, such as polyurethane, or silicone) and the helical long elements 52 (which are typically a shape memory alloy, such as Nitinol) in subsequent stages of impeller manufacturing. For some applications, sutures (e.g., polyester sutures, not shown) are wrapped around the springs 54. Typically, the sutures are configured to facilitate bonding between a membrane of material (which is typically an elastomer, such as polyurethane, or silicone) and the springs (which are typically a shape memory alloy, such as Nitinol) in subsequent stages of impeller manufacturing.

[0203] Typically, at this stage, a structure 59 as shown in FIG. 3A is assembled. The structure includes a cut and shaped tube that defines proximal bushings and distal sleeves, helical long elements, and springs (and, optionally, long elements and sutures). The structure is immersed in a material that defines a membrane 56. For some applications, the assembled structure is immersed in the material with a mandrel disposed through the cavity defined by the springs and bushings, although it should be noted that a mandrel is not shown in FIG. 3A . Typically, the material from which the membrane is made is silicone and / or polyurethane (and / or similar elastomers), and the assembled structure is immersed in the material while the material is in an uncured, liquid state. Subsequently, the material is cured so that it solidifies, e.g., by drying it. For some applications, the assembled structure is rotated while the material is drying, which typically facilitates forming a membrane of material having a substantially uniform thickness within each impeller blade. Once the material has dried, the mandrel is typically removed from the cavity defined by the bushings and springs.

[0204] Typically, as a result of the above-described process, a continuous membrane of material extends between each helical long element and a spring, and the continuous membrane of material also extends along the length of the spring so as to define a tube in which the spring is embedded. The portions of the membrane that extend from each helical long element to a spring define an impeller blade. For applications in which the impeller includes long elements 67, the long elements are typically embedded within these portions of the membrane.

[0205] Typically, the elongated elements 67 are configured to limit the radial expansion of the impeller blades, as described in detail above. For some applications, the span of the impeller blades that the elongated elements allow to expand is set using the following technique. As described in the paragraph above, the two ends of the string or cord within the respective blade are tied to each other. Typically, the ends of the string or cord in each blade are tied such that the span of the impeller blade is set to be less than the desired span of the impeller, and such that there is some slack in the knot that ties the two ends of the string or cord to each other. Subsequently, the outer edges of the impeller blades are pulled apart from each other by tightening the knot between the ends of the string or cord within each blade in order to increase the span of the impeller blades. This process is repeated and the span of the impeller blades is measured until the desired span of the impeller blades is reached. Subsequently, the structure 59 with the string or cord tied to it is immersed in the elastomeric material from which the membrane 56 is made, and the elastomeric material is allowed to dry such that the string or cord remains tied to itself with the desired span of the impeller blades.

[0206] Typically, the impeller 50 is inserted into the left ventricle via a catheter while the impeller 50 is in a radially constrained configuration. In the radially constrained configuration, both the helical elongated elements 52 and the central axial spring 54 become axially elongated and radially constrained. Typically, the membrane 56 of material (e.g., silicone and / or polyurethane) changes shape to conform to the change in shape of the helical elongated elements and the central axial spring, both of which support the membrane of material. Typically, the use of springs to support the inner edges of the membrane allows the membrane to change shape without breaking or collapsing because the springs provide a large surface area to which the inner edges of the membrane are coupled. For some applications, the use of springs to support the inner edges of the membrane reduces the diameter to which the impeller can be radially constrained compared to, for example, the use of rigid shafts to support the inner edges of the membrane because the diameter of the springs themselves can be reduced by axially elongating the springs.

[0207] As described above, for some applications, the proximal hub 64 of the impeller 50 is coupled to the axial shaft 92 such that the axial position of the proximal hub relative to the shaft is fixed and the distal hub 58 of the impeller is slidable relative to the shaft. For some applications, when the impeller is radially constrained in order to insert the impeller into a ventricle or to withdraw the impeller from within the body of a subject, the impeller is axially elongated by sliding the distal hub distally along the axial shaft. As shown in FIG. 1 1, after the impeller is released within the body of a subject, the impeller assumes its non-radially constrained configuration (in which the impeller is typically set during operation of the impeller). FIG. 3A-FIG. 3C

[0208] Note that for illustrative purposes, in some figures, the impeller 50 is shown as not including the proximal hub 64 and the distal hub 58. For some applications, the proximal hub and the distal hub are coupled to the central shaft 92 and the helical elongated elements 52, respectively, as described above. FIG. 3A-FIG. 3C ​All features of the impellers shown and described. For example, some of the figures show impellers that do not include sutures 53 and / or elongated elements 67. The scope of this application includes impellers having any of the features shown and described herein in combination with any of the devices and methods described herein. FIG. 3A-FIG. 3C impellers having any of the features shown and described.

[0209] For some applications, the following technique is used to enhance the bonding of the elastomeric material to the at least one helical elongated element in a manner that does not result in protrusions from the effective edge of the impeller blade. Prior to immersion in the elastomeric material, the helical elongated element is coated with a coupling agent. Typically, the coupling agent is selected to have at least two functional groups that are configured to bond to the helical elongated element and the elastomeric material, respectively. For example, a silane compound such as n-(2-aminoethyl)-3-aminopropyltrimethoxysilane can be used that contains a first functional group (e.g., (OH)) that is configured to bond to the helical elongated element (which is typically made of an alloy such as Nitinol) and a second functional group (e.g., (NH2)) that is configured to bond to the elastomeric material. Typically, the functional groups in the coupling agent are only effective for a given period of time (e.g., on the order of an hour or less). Thus, within this period of time, a layer of elastomeric material is applied around the helical elongated element. Typically, the layer of elastomeric material is the same elastomeric material or a similar elastomeric material as used in the membrane 56. For example, a polycarbonate-based thermoplastic polyurethane such as Aromatic Carbothane TM (Aromatic Carbothane TM 75A) can be used in the membrane 56 and the coating layer can be the same polycarbonate-based thermoplastic polyurethane or a similar polycarbonate-based thermoplastic polyurethane such as Pellethane® (e.g., Pellethane® 90A).

[0210] For some applications, after the coating layer has been applied to the helical elongated element, the coated helical elongated element is sprayed with another layer of elastomeric material. Typically, the elastomeric material that is sprayed is the same elastomeric material or a similar elastomeric material as used as the elastomeric material for the membrane 56. For example, a polycarbonate-based thermoplastic polyurethane such as Aromatic Carbothane TM (Aromatic Carbothane TM75A), and the sprayed material can be the same polycarbonate-based thermoplastic polyurethane, or a similar polycarbonate-based thermoplastic polyurethane, such as Pellethane® (e.g., Pellethane® 90A). For some applications, the application of the spray to the helical elongated element rounds the helical elongated element. Typically, when the helical elongated element has a circular cross-section, the elastomeric material forms a layer having a substantially uniform thickness at the interface with the helical elongated element. For some applications, as described in the previous paragraph, the step of applying a layer of elastomeric material at least partially rounds the helical elongated element.

[0211] For some applications, after the spray has been applied to the helical elongated element, the structure 59 is immersed in an elastomer from which the film 56 is made, e.g., as described above. For some applications, the material used to make the film is an elastomeric material having an ultimate elongation greater than 300%, e.g., greater than 400%. Typically, the material has a relatively low molecular weight. For some applications, the material has a melt flow index (which is an indirect measure of molecular weight) of at least 4, e.g., at least 4.3. For some applications, the material has an ultimate tensile strength in excess of 6000 psi, e.g., in excess of 7000 psi, or in excess of 7500 psi. For some applications, the material is a thermoplastic polyurethane, e.g., Carbothane TM . For some applications, Aromatic Carbothane TM 75A. Typically, such a material combines one or more of the following properties: no loss of outside diameter during the immersion process, resistance to fatigue, resistance to deformation from kinking, and low loss of outside diameter during kinking.

[0212] In accordance with the above description of applying the film 56 to the helical elongated element, the scope of the present application includes any technique of applying additional layers of the same elastomeric material, a different elastomeric material, and / or an intermediary material to the helical elongated element prior to immersing the helical elongated element in the elastomeric material from which the film 56 is made, whether by spraying, immersion, or a different coating method. For some applications, the additional layers of elastomeric material are configured to round the helical elongated element, and / or to act as an intermediary to enhance the bond between the helical elongated element and the film 56 of material. For some applications, the intermediary material (e.g., silane) is configured to act as an intermediary to enhance the bond between the helical elongated element and the film 56 of material.

[0213] Reference is now made to FIG. 3D and FIG. 3E , FIG. 3D and FIG. 3Eis a schematic view of an impeller 50 including a single integrated anti-impeller overexpansion element 72 defining a plurality of elongate elements 67, in accordance with some applications of the present application. For illustrative purposes, FIG. 3D and FIG. 3E The impeller is shown without the membrane 56 of material. For some applications, the element 72 defines a ring 73 and a plurality of elongate elements 67 extending radially from the ring. For some applications, instead of threading a rope and / or wire around the spring 54, the ring 73 of the element 72 is placed around the spring, for example, by being placed around the tube 70, which is typically disposed at a longitudinally central location of the spring. The ends of the respective elongate elements 67 are then coupled to the respective helical elongate elements 52. As noted above, the elongate elements 67 are typically flexible, but substantially inelastic along the axis defined by the elongate element. Further typically, each of the elongate elements 67 is configured to be substantially incompressible. More specifically, each elongate element 67 is configured to exert a tensile force on the helical elongate elements 52 that prevents the helical elongate elements 52 from moving radially outward, such that the spacing between the helical elongate elements 52 and the central axial spring 54 would be greater than the length of the elongate elements 67 (in the absence of the elongate elements 67). When a force acting on the impeller would cause the helical elongate elements 52 to move radially outward (in the absence of the elongate elements 67), the anti-impeller overexpansion element is configured to prevent radial expansion of the impeller. Typically, a respective elongate element 67 is disposed within each impeller blade and is configured to prevent radial expansion of the impeller blade. For some applications, the element 72 is made of polyester and / or another polymer or a natural material containing fibers and / or nitinol (or a similar shape memory alloy).

[0214] Note that the scope of the present application includes the use of the single integrated anti-impeller overexpansion element 72 with impellers having structures other than that shown in FIG. 3D-FIG. 3E For example, the single integrated anti-impeller overexpansion element 72 can be used with impellers having axial structures other than the configuration of the spring 54. Typically, the axial structure defines a cavity therethrough, such that the impeller defines a cavity 62 therethrough.

[0215] Reference is now made to FIG. 3FIt is a schematic view of an impeller 50 that, according to some applications of the present application, includes a securing element 75 configured to secure the elongated element 67 relative to the tube 70. For some applications, the cord or line that includes the elongated element 67 is not wrapped around the tube 70 and does not pass through the longitudinal axis of the impeller. Rather, the cord or line is secured relative to the tube 70 by the securing element 75. Typically, the cord or line is secured to the outer surface of the tube 70 at a location on the outer surface of the tube that is proximate to the largest span of the helical elongated element (to which the end of the cord or line is tethered). For some applications, the securing element includes a ring, as shown. For some such applications, the ring defines small notches (or eyelets) 80 through which the cord or line passes between the ring and the tube 70.

[0216] Reference is now made to FIG. 3Gi and FIG. 3Gii These figures are pictures of an impeller 50 according to some applications of the present application. As shown, for some applications, the impeller is manufactured by using the method described above, adjacent blades 51 of the impeller 50 are shaped to define a continuous U-shaped curve. As shown by the curve 55, the curve 55 is added to the FIG. 3Gii When the membrane 56 of the elastomeric material transitions from one blade to an adjacent blade, the membrane forms a continuous U-shaped curve. Note that even at the spring 54, which extends along the axis of the impeller, the curvature of the membrane of the material is substantially uninterrupted. For some applications, the membrane of the material assumes the curvature described above as a result of the impeller being formed in the manner described above. Typically, by defining a continuous U-shaped curve, the impeller blades are configured to provide a smooth flow line along which blood flows through the impeller, thereby improving the efficiency of the impeller in pumping blood and / or reducing the risk of hemolysis relative to the case in which adjacent blades do not define a continuous curve (e.g., relative to the case in which the curvature is interrupted at the spring 54). For some applications, a substantially similar impeller is used in which the impeller has an axial structure that is configured differently than the axial structure of the spring 54 (e.g., a cylindrical axial structure). Typically, the axial structure defines a cavity therethrough, such that the impeller defines a cavity 62 therethrough. Alternatively, the impeller includes the spring 54 (which includes the tube 70) as the axial structure, as shown.

[0217] When viewed from the distal end of the impeller, the pressure side of each blade of the impeller (i.e., the side that pushes against blood during operation of the impeller) is convex in the distal region of the impeller, transitions to a substantially radially oriented in the region of the elongated element 67, and then is concave in the proximal region of the impeller. (For purposes of illustration, the opposite side of the pressure side of the impeller blade (i.e., the "non-pressure side") is convex in the distal region of the impeller, transitions to a substantially radially oriented in the region of the elongated element 67, and then is concave in the proximal region of the impeller.) FIG. 3GiiAs indicated above, the blood pumped by the impeller is first pumped by the convex impeller surfaces and then by the concave impeller surfaces when in use. For some applications, the elongated element 67 is disposed at about half the length of the impeller blade and is configured to facilitate a transition of the membrane of material from having a convex curvature to having a concave curvature. Thus, typically, at the region of the elongated element 67 within the impeller blade, the blade is substantially radially oriented. Typically, by defining a concave surface in the proximal region of the impeller, the pressure side of the blade of the impeller is configured to increase the flow and / or pressure of the blood even after the blood has flowed and / or pressure has been exerted on it in the distal region of the impeller. Alternatively (not shown), the pressure side of each blade of the impeller (i.e., the side that pushes against the blood during operation of the impeller) is concave in the distal region of the impeller, transitions to being substantially radially oriented in the region of the elongated element 67, and then is convex in the proximal region of the impeller.

[0218] Reference is now made to FIG. 5A and FIG. 5B which are schematic illustrations of an impeller 50 and a frame 34 of a ventricular assist device 20 in its non-radially constrained state and radially constrained state, respectively, in accordance with some applications of the present application. The impeller and frame are typically disposed in the radially constrained state during their catheter insertion into the body of a subject, and are disposed in the non-radially constrained state during operation of the impeller within the left ventricle of the subject. As described above, typically, the pump outlet tube 24 is disposed over at least a portion of the frame and extends proximally from at least a portion of the frame. However, for illustrative purposes, the frame and impeller are shown in FIG. 5A-FIG. 5B without the pump outlet tube 24.

[0219] As shown in FIG. 5B , the frame and impeller are typically held in the radially constrained configuration by a delivery catheter 143. Typically, in the radially constrained configuration of the impeller, the impeller has a total length of greater than 15 mm (e.g., greater than 20 mm), and / or less than 30 mm (e.g., less than 25 mm), e.g., 15-30 mm, or 20-25 mm. Further typically, in the non-radially constrained configuration of the impeller, the impeller has a length of greater than 8 mm (e.g., greater than 10 mm), and / or less than 18 mm (e.g., less than 15 mm), e.g., 8-18 mm, or 10-15 mm. In addition, typically, when the impeller and frame 34 are arranged in the radially constrained configuration (as shown in FIG. 5B ), the impeller has an outer diameter of less than 2 mm (e.g., less than 1.6 mm), and the frame has an outer diameter of less than 2.5 mm (e.g., less than 2.1 mm).

[0220] As described above, typically, the axial shaft 92 is passed through the lumen 62 of the impeller (the lumen 62 is in theFIG. 3C The axis through the impeller 50 is shown. Typically, the proximal bushing 64 of the impeller is coupled to the shaft via a coupling element 65 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. The axial shaft itself is radially stabilized via the proximal radial bearing 116 and the distal radial bearing 118.

[0221] Typically, the coupling portion 31 of the frame 34 is coupled to the proximal radial bearing 116, e.g., via a snap-fit coupling and / or via welding. Typically, at the distal end of the frame 34, the distal strut engagement 33 is placed into a groove defined by the outer surface of the distal radial bearing 118, the groove being shaped to conform to the shape of the distal strut portion. As shown, the proximal end of the distal tip element 107, which defines the distal tip portion 120, typically holds the distal strut portion in its closed configuration around the outside of the distal radial bearing 118. For some applications, the device includes a distal extension 121 that extends distally from the distal radial bearing. Typically, the extension is configured to reinforce the area of the distal tip element into which the distal end of the shaft 92 is moved (e.g., the axial shaft receiving tube 126 or a portion thereof described below).

[0222] As noted above, the axial shaft 92 is radially stabilized via the proximal radial bearing 116 and the distal radial bearing 118. In turn, the axial shaft radially stabilizes the impeller relative to the inner surface of the frame 34 by passing through the cavity 62 defined by the impeller, such that, as noted above, even a relatively small gap (e.g., a gap as described above) between the outer edges of the blades of the impeller and the inner surface of the frame 34 is maintained during rotation of the impeller. For some applications, the axial shaft 92 is made of stainless steel, and the proximal bearing 116 and / or the distal bearing 118 are made of hardened steel. Typically, when the impeller and frame are crimped (i.e., radially constrained) for insertion into the body of a subject, the distal bushing 58 of the impeller is configured to slide along the axial shaft in the distal direction such that the impeller becomes axially elongated, while the proximal bushing remains in an axially fixed position relative to the axial shaft. More generally, by sliding the distal bushing over the axial shaft, while the proximal bushing remains in an axially fixed position relative to the axial shaft, the impeller is changed from its radially constrained configuration to its non-radially constrained configuration, and vice versa.

[0223] Typically, the impeller itself is not directly disposed within any radial or thrust bearing. Rather, the bearings 116 and 118 act as radial bearings with respect to the axial shaft. Typically, the pump portion 27 (and more generally the ventricular assist device 20) does not include any thrust bearing configured to be disposed within the subject's body and configured to resist thrust forces resulting from rotation of the impeller. For some applications, one or more thrust bearings are disposed outside the subject's body (e.g., within the motor unit 23 as shown in FIG. 1A , FIG. 7A-FIG. 7Bii For some applications, the mechanical and / or magnetic elements are configured to maintain the impeller within a given axial position range. For example, a magnet (e.g., magnet 82, described below with reference to FIG. 7A , disposed at the proximal end of the drive cable 130 (e.g., outside the subject's body) can be configured to apply axial motion to the impeller, and / or maintain the impeller within a given axial position range.

[0224] Reference is now made to FIG. 6A and FIG. 6B , which are schematic illustrations of the ventricular assist device 20 at various stages of a motion cycle of the impeller 50 of the ventricular assist device with respect to the frame 34 of the ventricular assist device, in accordance with some applications of the present application. For some applications, as the impeller pumps blood through the tube 24 by rotation, the axial shaft 92 (to which the impeller is fixed) is driven to move the impeller in an axial reciprocating manner within the frame 34 by moving the axial shaft in an axial reciprocating manner, as described in further detail below with reference to FIG. 7A-FIG. 7Bii Alternatively or additionally, the impeller and the axial shaft are configured to move in an axial reciprocating manner within the frame 34 in response to forces acting on the impeller, without the need to actively drive the axial shaft to move the axial shaft in an axial reciprocating manner. Typically, during the cardiac cycle of the subject, the pressure difference between the left ventricle and the aorta varies from approximately zero during the ventricular systole (hereinafter "systole") to a relatively large pressure difference (e.g., 50 mmHg - 70 mmHg) during the ventricular diastole (hereinafter "diastole"). For some applications, due to the increase in the pressure difference against which the impeller pumps during diastole (and due to the drive cable 130 being stretchable), the impeller is pushed distally with respect to the frame 34 during diastole, as compared to the position of the impeller with respect to the frame 34 during systole. In turn, due to the impeller being connected to the axial shaft, the axial shaft moves forward. During systole, the impeller (and in turn the axial shaft) moves back to its systole position. In this manner, the axial reciprocating motion of the impeller and the axial shaft is generated in a passive manner, i.e., without the need to actively drive the axial shaft and the impeller to undergo such motion.FIG. 6A The impeller and axial shaft are shown positioned at their typical contraction point, and FIG. 6B The impeller and axial shaft are shown in their typical diastolic position.

[0225] In some applications, the portion of the axial shaft in contact with the proximal support 116 and the distal support 118 changes continuously due to its axial reciprocating motion. In some such applications, assuming all else is equal, the frictional force exerted on the axial shaft by the supports is distributed over a larger area of ​​the axial shaft compared to when the axial shaft does not move relative to the supports, thereby reducing wear on the axial shaft. Alternatively or additionally, by reciprocating relative to the supports, the axial shaft removes any residue, such as blood residue, from the interface between the axial shaft and the supports.

[0226] For some applications, when the frame 34 and impeller 50 are in their non-radially constrained configuration (e.g., when the frame and impeller are deployed in the left ventricle), the length of the frame exceeds the length of the impeller by at least 2 mm (e.g., at least 4 mm, or at least 8 mm). Typically, the proximal support 116 and the distal support 118 are each 2 mm to 4 mm in length (e.g., 2 mm to 3 mm). More typically, the impeller and axial shaft are configured to reciprocate axially within the frame at least along the length of each of the proximal and distal supports, or at least along twice the length of each of these supports. Thus, during the reciprocating axial movement of the axial shaft, either side of each of these supports is wiped clean.

[0227] For some applications, the range of impeller motion is as follows: FIG. 6A-FIG. 6B As shown, where FIG. 6A The impeller is positioned closest to the heart during the cardiac cycle (typically, the impeller is positioned in this order during systole), and FIG. 6B This indicates the impeller's furthest position during the cardiac cycle (typically, the impeller is positioned this way during diastole). For example... FIG. 6A As shown, for some applications, at the closest position to the impeller, the proximal end of the impeller is positioned at location I. P At that location, I P Within the proximal conical segment of frame 34. (e.g.) FIG. 6B As shown, for some applications, at the farthest position of the impeller, the far end of the impeller is set at position I. D At that location, I D At the distal end of the columnar segment of frame 34. For the purposes of this application, the frame from I P To I DThe entire segment of the frame can be considered to house the impeller, as this entire segment of the frame typically houses at least a portion of the impeller during at least a portion of the cardiac cycle. Typically, throughout the cardiac cycle, the segment of the impeller having the greatest impeller span is disposed within the cylindrical portion of the frame 34. However, during at least a portion of the cardiac cycle, the proximal portion of the impeller is typically disposed within the proximal conical segment of the frame.

[0228] Referring again to FIG. 6A and FIG. 6B and also referring to FIG. 6C , FIG. 6C is a magnified schematic view of a distal tip element 107 according to some applications of the present application, the distal tip element 107 including an axial shaft receiving tube 126 and a distal tip portion 120 of a ventricular assist device 20. Typically, the distal tip element 107 is a single integrated element that includes both the axial shaft receiving tube 126 and the distal tip portion 120. For some applications, the distal tip element 107 is configured to be soft, such that the distal tip portion is configured not to injure the subject tissue even if the distal tip portion comes into contact with tissue (e.g., tissue of the left ventricle). For example, the distal tip element 107 can be made of silicone, polyethylene terephthalate (PET), and / or polyether block amide (e.g., PEBAX®). For some applications, the distal tip portion defines a lumen 122 therethrough. For some such applications, during insertion of the ventricular assist device into the left ventricle, a guide wire 10 ( FIG. 1B ) is first inserted into the left ventricle according to, for example, known techniques. Then, the distal tip portion of the ventricular assist device is guided to the left ventricle by advancing the distal tip portion over the guide wire, with the guide wire being disposed within the lumen 122. For some applications, a duckbill valve 390 (or a different type of hemostatic valve) is disposed at the distal end of the lumen 122 of the distal tip portion 120.

[0229] Typically, during insertion of the ventricular assist device into the subject's ventricle, a delivery catheter 143 is placed over the impeller 50 and the frame 34 and holds the impeller and frame in their radially constrained configuration. For some applications, during insertion of the delivery catheter into the subject's ventricle, the distal tip element 107 extends distally from the delivery catheter. For some applications, at the proximal end of the distal tip element, the distal tip element has a flared portion 124 that acts as a stop and prevents the delivery catheter from being advanced beyond the flared portion.

[0230] It should be noted that, FIG. 6A-FIG. 6CThe outer shape of the distal tip portion in (and some other figures) is shown to define a complete loop, with the distal end of the distal tip portion, which has a duckbill valve 390 disposed within it, spanning over the more proximal portion of the distal tip portion. Typically, due to having a guide wire inserted therethrough (during insertion of the ventricular assist device into the left ventricle), the distal tip portion remains partially straightened, even after the guide wire is removed from the distal tip portion. Typically, the partial straightening of the distal tip portion is such that, when the distal tip portion is disposed within the left ventricle, the distal tip portion does not define a complete loop without an external force acting on the distal tip portion, e.g., as shown in FIG. 1B , FIG. 15D and FIG. 16A For some applications, to insert a guide wire through the distal tip portion, a straightening element 270 is used, as described in further detail below, e.g., with reference to FIG. 23A-FIG. 23C Further aspects of the distal tip portion shape will be described in further detail below.

[0231] Reference is now made to FIG. 6D and FIG. 6E which are schematic views of the impeller 50, according to some applications of the present application, the proximal bushing 64 of the impeller is coupled to a coupling element 65 which extends proximally so as to act as a stopper. FIG. 6D The impeller is shown in the contraction phase of its motion cycle, and FIG. 6E The impeller is shown in the diastolic phase of its motion cycle. Typically, the coupling element extends proximally so as to prevent the central region of the impeller, at which the impeller is at its maximum span, from sliding proximally into the proximal tapered portion of the frame 34. For example, if the impeller slides further proximally beyond a given amount, in the contraction phase of the impeller motion cycle (shown in FIG. 6D , the proximally extending coupling element will contact the proximal radial bearing 116, thereby preventing further proximal motion of the impeller. For some applications, the coupling element extends proximally so that it has a total length of more than 1.5 mm, e.g., more than 4 mm. For some applications (not shown), as an alternative or in addition to the proximally extending coupling element, a separate stopper element is disposed on the axial shaft proximally relative to the coupling element. Typically, the stopper is configured as described with reference to the proximally extending coupling element. I.e., if the impeller slides further proximally beyond a given amount, the stopper element will contact the proximal radial bearing 116, thereby preventing further proximal motion of the impeller.

[0232] Reference is now made to FIG. 7Awhich is a schematic illustration of an exploded view of a motor unit 23 of a ventricular assist device 20 in accordance with some applications of the present invention. As shown, the motor unit is typically a handle that is configured to be disposed outside of the subject's body and house the motor. Thus, the motor unit can alternatively be referred to as a handle unit.

[0233] For some applications, the computer processor 25 that controls rotation of the impeller 50 of the console 21 FIG. 1A is also configured to control reciprocation of the axial shaft. Typically, both types of motion are generated using the motor unit 23. The scope of the present invention includes controlling reciprocation of any frequency. For some applications, an indication of the subject's cardiac cycle is detected (e.g., by detecting the subject's ECG), and the reciprocation of the axial shaft is synchronized with the subject's cardiac cycle.

[0234] Typically, the motor unit 23 includes a motor 74 that is configured to impart rotational motion to the impeller 50 via a drive cable 130. As described in further detail below, typically the motor is magnetically coupled to the drive cable. For some applications, an axial motion driver 76 is configured to drive the motor to move in an axial reciprocating manner (as indicated by double-headed arrow 79). Typically, due to the magnetic coupling of the motor to the drive cable, the motor imparts the reciprocating motion to the drive cable, which in turn imparts the motion to the impeller. As described above and below, for some applications, the drive cable, impeller, and / or axial shaft reciprocate in a passive manner, e.g., due to periodic changes in the pressure gradient against which the impeller pumps blood. Typically, for such applications, the motor unit 23 does not include an axial motion driver 76.

[0235] For some applications, the magnetic coupling of the motor to the drive cable is as FIG. 7A indicated. As FIG. 7AAs shown, at least one more drive magnet 77 (e.g., two drive magnets 77) is coupled to the motor via a drive magnet housing 78. For some applications, the drive magnet housing includes a ring 81 (e.g., a steel ring), and the drive magnets are adhered to the inner surface of the ring. For some applications, as shown, a spacer 85 is adhered to the inner surface of the ring 81 between the two drive magnets. At least one follower magnet 82 is disposed between the drive magnets such that there is axial overlap between the drive magnets and the follower magnet. The follower magnet is coupled to a pin 131 that extends beyond the distal end of the follower magnet 82, with the pin being coupled to the proximal end of the drive cable 130. For example, the follower magnet can be cylindrical and define a hole therethrough, and the pin 131 can be adhered to the inner surface of the follower magnet that defines the hole. For some applications, the follower magnet is cylindrical, and the magnet includes a north pole and a south pole that are separated from one another along a line 83 that bisects the cylinder along the length of the cylinder, as shown. For some applications, the follower magnet is housed within a cylindrical housing 87. Typically, the pin 131 defines a cavity 133 via which the guide wire 10 is inserted through the pin.

[0236] Note that in the applications shown, the drive magnets are disposed outside of the follower magnet. However, the scope of the present application includes reversing the configuration of the drive magnets and the follower magnet (with necessary modifications). For example, the proximal end of the drive cable can be coupled to two or more follower magnets that are disposed around the drive magnet such that there is axial overlap between the follower magnets and the drive magnet. FIG. 7A

[0237] As noted above, typically, a cleaning system 29 (as shown, for example) is used with the ventricular assist device 20. Typically, the motor unit 23 includes an inlet port 86 and an outlet port 88 for use with the cleaning system. For some applications, a cleaning fluid is pumped continuously or periodically into the ventricular assist device via the inlet port 86 and out of the ventricular assist device via the outlet port 88. Other aspects of the cleaning system will be described below. FIG. 1A

[0238] ​​Typically, the magnet 82 and the pin 131 are held in axially relatively fixed positions within the motor unit 23. (For some applications, the magnet 82 does have a small degree of freedom of axial and / or rotational movement relative to other components of the motor unit, such as the drive magnet 77. For some applications, this movement is measurable, as described in further detail below.) Typically, the proximal end of the drive cable is coupled to the pin 131, and is held in an axially fixed position relative thereto. Typically, the drive cable 130 extends from the pin 131 to the axial shaft 92, and thereby at least partially fixes the axial position of the axial shaft, and in turn the impeller 50. For some applications, the drive cable is somewhat stretchable. For example, the drive cable can be made of stretchable coiled wire, as described in further detail below. The drive cable typically allows the axial shaft (and in turn the impeller) to assume a range of axial positions (by the drive cable becoming more or less stretched), but limits the axial movement of the axial shaft and impeller to a certain range of motion (by holding the proximal end of the drive cable in an axially relatively fixed position, and by limiting the stretchability of the drive cable).

[0239] Reference is now made to FIG. 7Bi and FIG. 7Bii , which are schematic illustrations of motor units 23 according to some applications of the present application. Generally, the motor units 23 shown in FIG. 7Bi and FIG. 7Bii are similar to the motor units shown in FIG. 7A , unless otherwise noted. The motor units 23 shown in FIG. 7Bi and FIG. 7Bii contain similar components to the motor units 23 shown in FIG. 7A . For some applications, the motor units include a heat sink 90 configured to dissipate heat generated by the motor. Alternatively or additionally, the motor units include a vent port 93 configured to facilitate dissipation of heat generated by the motor. For some applications, the motor units include dampeners 94 and 96 configured to dampen vibrations of the motor unit caused by rotational movement and / or axial reciprocating movement of components of the ventricular assist device.

[0240] As noted above, for some applications, the impeller 50 and the axial shaft 92 are configured to move axially within the frame 34 in response to forces acting on the impeller, without the need to actively drive the axial shaft to move in an axially reciprocating manner. Typically, during the cardiac cycle of a subject, the pressure differential between the left ventricle and the aorta varies from approximately zero during the systolic phase to a relatively large pressure differential (e.g., 50 mmHg - 70 mmHg) during the diastolic phase. For some applications, as the pressure differential against which the impeller pumps increases during the diastolic phase (and as the drive cable is stretchable), the impeller is pushed distally relative to the frame 34 during the diastolic phase than it is relative to the frame 34 during the systolic phase. In turn, as the impeller is connected to the axial shaft, the axial shaft moves forward. During the systolic phase, the impeller (and in turn the axial shaft) moves back to its systolic phase position. In this way, the axial reciprocation of the impeller and the axial shaft occurs in a passive manner, i.e., without the need to actively drive the axial shaft and the impeller to undergo such motion.

[0241] Reference is now made to FIG. 8A FIG. 6 is a graph showing the change in length of a drive cable of a ventricular assist device as a function of the pressure gradient against which an impeller of the ventricular assist device pumps, as measured in an experiment. The impeller and drive cable described herein were used to pump a glycerol-based solution through a chamber, where the chamber was arranged to reproduce the left ventricle and the aorta, and the solution had similar properties to blood (e.g., density and viscosity). The pressure gradient against which the impeller pumps was varied in a pulsatile manner to represent the pulsatility of the pressure gradient against which the impeller typically pumps as it pumps blood from the left ventricle to the aorta. At the same time, the movement of the drive cable was imaged, and the change in drive cable length was determined via analysis of the images. FIG. 8A The graph shown in FIG. 6 shows the measured change in length of the drive cable as a function of the pressure gradient. As shown, as the pressure gradient against which the impeller pumps increases, the drive cable becomes increasingly longer. FIG. 8A As shown by the results shown in FIG. 6 and described above, typically, the impeller moves reciprocally relative to the frame 34 in response to changes in the pressure against which the impeller pumps blood (e.g., the pressure differential between the left ventricle and the aorta). In turn, the movement of the impeller causes the drive cable 130 to become more or less elongated. FIG. 8A

[0242] For some applications, during operation of the ventricular assist device, the console 21 (and in turn the drive cable 130) is configured to move axially within the frame 34 in response to forces acting on the impeller, without the need to actively drive the axial shaft to move in an axially reciprocating manner. Typically, during the cardiac cycle of a subject, the pressure differential between the left ventricle and the aorta varies from approximately zero during the systolic phase to a relatively large pressure differential (e.g., 50 mmHg - 70 mmHg) during the diastolic phase. For some applications, as the pressure differential against which the impeller pumps increases during the diastolic phase (and as the drive cable is stretchable), the impeller is pushed distally relative to the frame 34 during the diastolic phase than it is relative to the frame 34 during the systolic phase. In turn, as the impeller is connected to the axial shaft, the axial shaft moves forward. During the systolic phase, the impeller (and in turn the axial shaft) moves back to its systolic phase position. In this way, the axial reciprocation of the impeller and the axial shaft occurs in a passive manner, i.e., without the need to actively drive the axial shaft and the impeller to undergo such motion. FIG. 1A ​The computer processor 25 of the system 10 (FIG. 1) is configured to measure a value indicative of the pressure exerted on the impeller (which is indicative of the pressure difference between the left ventricle and the aorta) by measuring a value of the tension in the drive cable 130 and / or the axial motion of the drive cable. For some applications, based on the measured value, the computer processor detects events in the cardiac cycle of the subject, determines the left ventricular pressure of the subject, and / or determines the cardiac afterload of the subject. For some applications, the computer processor controls the rotation of the impeller, and / or controls the axial reciprocation of the axial shaft in response thereto.

[0243] Referring again to FIG. 7A For some applications, the ventricular assist device 20 includes a sensor 84. For example, the sensor can include a magnetometer (e.g., a Hall sensor) disposed within the motor unit 23, as shown in FIG. 7A For some applications, the situation is that, because the driven magnets are held in place relative to the drive magnets by magnetic coupling rather than rigid mechanical linkage, axial reciprocation of the impeller causes measurable reciprocation of the inner driven magnet 82 relative to the outer one or more drive magnets 77. Note that typically the axial motion of the magnets is substantially less than the axial motion of the impeller, because the entire range of motion of the impeller is not transmitted along the length of the drive cable. For some applications, the magnetometer measures changes in the magnetic field produced by one of the magnets in order to measure the axial motion of the drive cable 130, and in turn determine the pressure against which the impeller is pumping. For example, the inner driven magnet 82 can be longer in the axial direction than the outer drive magnets 77. Because the inner magnet is longer than the outer magnets, the magnetic field lines emanating from the inner magnet do not pass to the outer magnets, and the magnetic flux produced by these field lines, as measured by the magnetometer, changes due to the drive cable, and in turn causes the inner magnet to move axially. During operation, the motor 74 rotates, thereby producing an AC signal in the magnetometer, which has a frequency typically between 200 Hz and 800 Hz. Typically, when the tension in the drive cable changes due to the cardiac cycle of the subject, this produces a low frequency envelope in the signal measured by the magnetometer, which typically has a frequency of 0.5 Hz - 2 Hz. For some applications, the computer processor measures the low frequency envelope, and from the measured envelope derives the cardiac cycle of the subject.

[0244] For some applications, the magnetometer measurements are initially calibrated so that the change in magnetic flux per unit change in pressure that the impeller pumps against (i.e., per unit change in the pressure difference between the left ventricle and the aorta, or per unit change in the pressure gradient) is known. It is known that, in most subjects, during systole, the left ventricular pressure is equal to the aortic pressure. Thus, for some applications, the subject's aortic pressure is measured, and then the subject's left ventricular pressure at a given time is 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 pressure in the left ventricle is assumed to be equal to the pressure of the aorta). For example, the subject's aortic pressure can be measured by measuring the pressure in the passageway 224 defined by the delivery catheter 143, as described in further detail below. For some applications, the above-described 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 can be determined.

[0245] For some applications, techniques similar to those described in the preceding paragraph are typically used, but instead of or in addition to measuring with the magnetometer, a different parameter is measured to determine left ventricular blood pressure at a given time (and / or a different physiological parameter, such as an event in the subject's cardiac cycle and / or the subject's cardiac afterload). For example, it is typically the case that there is a relationship between the amount of power (and / or current) required to drive the impeller to rotate at a given rotational rate and the pressure differential produced by the impeller. (Note that a portion of the pressure differential produced by the impeller is used to overcome the pressure gradient against which the impeller pumps, and a portion of the pressure differential produced by the impeller is used to actively pump blood from the left ventricle to the aorta by creating a positive pressure differential between the left ventricle and the aorta. Also, typically the relationship between the above-described components changes over the course of a cardiac cycle.) For some applications, calibration measurements are performed so that the relationship between (a) the motor power (and / or current) required to rotate the impeller at a given rotational rate and (b) the pressure differential produced by the impeller is known. For some applications, the subject's aortic pressure is measured, and the subject's left ventricular pressure at a given time is calculated by a computer processor based on (a) the measured aortic pressure, (b) the motor power (and / or current) required to rotate the impeller at a given rotational rate at the given time, and (c) a predetermined relationship between the motor power (and / or current) required to rotate the impeller at a given rotational rate and the pressure differential produced by the impeller. For some applications, the above-described techniques are performed while keeping the impeller rotational rate constant. Alternatively or additionally, the rotational rate of the impeller is varied, and the variations in the rotational rate of the impeller are taken into account in the above-described calculations. For some applications, the above-described techniques are used to determine alternative or additional physiological parameters. For example, an event in the subject's cardiac cycle and / or the subject's cardiac afterload can be determined.

[0246] Typically, the tube 24 has a known cross-sectional area (when the tube is in an open state due to blood flowing through the tube). For some applications, the flow rate through the tube 24 produced by the impeller is determined based on the determined pressure differential produced by the impeller and the known cross-sectional area of the tube. For some applications, this flow rate calculation incorporates calibration parameters in order to account for factors such as flow resistance that are specific to the ventricular assist device (or type of ventricular assist device) for which the calculations are being performed. For some applications, a ventricular pressure-volume loop is derived based on the determined ventricular pressure.

[0247] Referring again to FIG. 7AFor some applications, in addition to the magnetometer 84 that is configured to measure the magnetic flux density generated by the driven magnet, a second magnetometer 84A (e.g., a second Hall sensor) measures the indication of the magnetic flux density generated by the drive magnet. For some applications, the second magnetometer measures the magnetic flux density of the motor, which is indicative of the magnetic flux density cycle of the drive magnet, as the motor directly drives the drive magnet to rotate. Typically, a torque is generated on the impeller as it rotates, such as to pump blood. Further typically, the strength of the torque depends on various parameters, such as the flow rate generated by the impeller, the rate of rotation of the impeller, and / or the pressure gradient against which the impeller pumps. For some applications, the torque generated on the impeller generates a measurable torque on the inner driven magnet 82 relative to the outer drive magnet 77, as the driven magnet is held in place relative to the drive magnet by magnetic coupling rather than rigid mechanical linkage. Note that the torque typically generated on the driven magnet is much smaller than the torque generated on the impeller, as the torque generated on the impeller is not transmitted along the length of the drive cable. However, it is typical that at least some of the torque generated on the impeller is transmitted to the driven magnet via the drive cable.

[0248] The torque transmitted to the driven magnet typically causes a phase difference between the signal measured by the magnetometer 84 (which measures the magnetic flux density of the driven magnet) and the signal measured by the second magnetometer 84A (which measures the magnetic flux density of the motor and / or the drive magnet). For some applications, when the torque on the impeller changes, this causes a change in the phase difference between the signal measured by the magnetometer 84 and the signal measured by the second magnetometer 84A. For some applications, the computer processor detects the change in the above-described phase difference and determines a physiological parameter of the subject at least partially in response to the change in the above-described phase difference. For example, based at least in part on the change in the phase difference, the computer processor can determine the difference between the left ventricular pressure of the subject and the aortic pressure of the subject, the left ventricular pressure of the subject, an event in the cardiac cycle of the subject, the cardiac afterload of the subject, and / or a different physiological parameter. For some applications, the techniques described in this paragraph are used as an alternative to the above-described techniques for determining a physiological parameter using magnetic flux density measurements and / or power consumption measurements. Alternatively, two or more of the techniques are used in conjunction with one another. For example, a physiological parameter of the subject can be determined based on a mathematical model that incorporates two or more measurements, and / or an estimate of a physiological parameter of the subject made using one of the techniques can be verified using another of the techniques.

[0249] Reference is now made to FIG. 8B and FIG. 8C which show plots of the correlation between the phase difference signal and the pressure gradient against which the impeller 50 pumps, in accordance with some applications of the present application.

[0250] FIG. 8BThe graph shown in FIG. 2 illustrates the results of an experiment in which a ventricular assist device as described herein was used to pump blood against a corresponding pressure gradient in a static in-vitro system (i.e., the pressure gradient was constant when each measurement was taken). From the phase difference signal, the magnetic flux amplitude signal, and the current consumed by the motor, a linear regression model was used to estimate the pressure gradient against which the impeller was pumping. FIG. 8B The graph shown in FIG. 3 illustrates the estimated pressure gradient superimposed on the measured pressure gradient. As shown, the linear regression model in combination with the phase difference measurement provides a reliable method for estimating the pressure gradient against which the impeller is pumping.

[0251] FIG. 8C The graph shown in FIG. 2 illustrates the results of an experiment in which a ventricular assist device as described herein was used to pump blood against a corresponding pressure gradient in a static in-vitro system (i.e., the pressure gradient was constant when each measurement was taken). From the phase difference signal, the magnetic flux amplitude signal, and the current consumed by the motor, a linear regression model was used to estimate the pressure gradient against which the impeller was pumping. FIG. 8C The graph shown in FIG. 3 illustrates the estimated pressure gradient superimposed on the measured pressure gradient. As shown, the linear regression model in combination with the phase difference measurement provides a reliable method for estimating the pressure gradient against which the impeller is pumping.

[0252] According to the above, and according to some applications of the present application, a magnetic phase difference between one or more driven magnets and one or more driving magnets is measured, and a physiological parameter of a subject is determined at least partially in response to the magnetic phase difference. For example, based at least in part on changes in the phase difference, a computer processor can determine a difference between a left ventricular pressure of the subject and an aortic pressure of the subject, a left ventricular pressure of the subject, an event in a cardiac cycle of the subject, a cardiac afterload of the subject, and / or a different physiological parameter. For some applications, the physiological parameter is determined based on the phase difference measurement in combination with one or more additional measurements, such as a magnetic flux amplitude measurement, a power consumed by the motor, and / or a current consumed by the motor. Typically, such measurements are combined in a mathematical model, such as a linear regression model, and / or a spatial state model.

[0253] Reference is now made to FIG. 9A-FIG. 9G FIGS. 17A-17C are schematic illustrations of various views of a motor unit support 170 configured to support the motor unit 23 on a patient's leg 172, according to some applications of the present application. For some applications, the ventricular assist device is inserted into the patient's body via a femoral access point 173, and the motor unit support is configured to rest on the patient's thigh below the femoral access point, as shown. Typically, the motor unit support is configured to at least partially isolate the patient's leg from vibrations and / or heat generated by the motor unit during operation of the motor unit.

[0254] For some applications, the motor unit support includes a curved base 176 configured to rest on a patient's thigh, and a motor unit dock 178 on which the motor unit rests. Typically, there is a gap 179 between the motor unit dock and the curved base of the motor unit support, such that the patient's leg passes through the gap and separates the motor unit from the patient's leg during operation of the motor unit, which serves to at least partially isolate the patient's leg from vibrations and / or heat generated by the motor unit. For some applications, the motor unit support is configured to receive a strap 174 through the gap, which serves to bind the motor unit support to the patient's leg. Typically, the strap is elastic and / or adjustable to fit the patient's leg.

[0255] Typically, the motor unit support includes a coupling element 180 (e.g., shown in FIG. 9D ) for coupling the motor unit dock to the motor unit. As noted above, for some applications, the motor unit includes a vented port 93 configured to facilitate dissipation of heat generated by the motor. For some such applications, the coupling element includes a snap-fit coupling element, e.g., as shown in FIG. 9E , which is configured to couple the motor unit dock to the motor unit by snapping the coupling element into the vented port of the motor unit. For some applications, the motor unit includes vented ports on both sides of the motor unit, such that either side of the motor unit can be coupled to the motor unit dock.

[0256] Reference is now made to FIG. 10A , FIG. 10B , and FIG. 10C , which are schematic illustrations of a drive cable 130 of a ventricular assist device 20 according to some applications of the present application. Typically, rotational motion of the motor is transmitted to the axial shaft via the 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 (e.g., the connection between the distal end of the drive cable and the proximal end of the axial shaft is shown in the enlarged portion on the left side of FIG. 5A . For some applications, the drive cable includes a plurality of wires 134 which are disposed in a coiled configuration so as to impart sufficient strength and flexibility to the drive cable such that a portion of the cable can be held within the aortic arch (e.g., the portion corresponding to arrow 145 in FIG. 10A ) while the cable rotates and moves in an axial reciprocating motion. For some applications, the drive cable includes a plurality of coaxial coiled wire layers. For example, as shown in FIG. 10A-FIG. 10C , the drive cable can include an outer layer 136 and an inner layer 138 which are coaxial to each other, and each of which includes coiled wires.

[0257] Typically, the drive cable is disposed within a first outer tube 140, which is configured to remain stationary as the drive cable undergoes rotational and / or axial reciprocating motion. The first outer tube is configured to effectively act as a support tube for the drive cable along the length of the drive cable. Thus, the first outer tube is also referred to herein as a drive cable support tube. Reference will be made to the drive cable support tube below FIG. 10D The drive cable support tube is described in further detail. For some applications, the drive cable support tube is disposed within a second outer tube 142, which is typically made of a material having greater flexibility than the drive cable support tube (e.g., nylon and / or polyether block amide), and typically has a greater thickness than the drive cable support tube.

[0258] Typically, during insertion of the impeller and frame into the left ventricle, the impeller 50 and frame 34 are held in a radially constrained configuration by the delivery catheter 143. As described above, to cause the impeller and frame to assume a non-radially constrained configuration, the delivery catheter is retracted. For some applications, as described above, the delivery catheter is retracted by pulling on the proximal end of the delivery catheter. FIG. 10A As shown, during operation of the left ventricular device, the delivery catheter is held in the subject's aorta, and the outer tube 142 is disposed inside the delivery catheter. (Although FIG. 10A The distal end of the delivery catheter is shown disposed within the aortic arch, but for some applications, the distal end of the delivery catheter is disposed within the descending aorta during operation of the left ventricular device. For some applications, a passageway 224 is defined between the delivery catheter 143 and the outer tube 142 during operation of the left ventricular device. (Note that the passageway shown in FIG. 10A is not to scale.) For some such applications, the subject's aortic blood pressure is measured by measuring the blood pressure within the passageway 224. For example, a pressure sensor 216 (schematically shown in FIG. 1A ) can be in fluid communication with the passageway 224, and can be configured to measure the subject's aortic pressure by measuring the blood pressure within the passageway 224. Typically, to retract the left ventricular device from the subject, the delivery catheter is advanced over the impeller and frame, causing the impeller and frame to assume their radially constrained configurations. The catheter is then withdrawn from the subject.

[0259] For some applications, the drive cable 130 is composed of a plurality of coaxial layers, each coaxial layer including a plurality of coiled wires 134. For example, as shown in FIG. 10A-FIG. 10CAs shown, the drive cable includes an outer layer 136 and an inner layer 138, each layer comprising a coiled wire. Typically, when the impeller begins to rotate, if the direction of rotation of the impeller causes the rotation of the drive cable in that direction to at least partially tighten the coiled wire of the drive cable, this will also cause the impeller to advance relative to the frame due to the tightening of the coiled wire (i.e., the winding reduces the radius of the coil) and thus axial elongation. For some applications, at least a portion of the drive cable is configured such that (a) in response to the impeller rotating in a predetermined direction of rotation to pump blood from the left ventricle to the aorta, (b) the rotation of the drive cable in that direction causes the coiled wire of the drive cable to at least partially unwind along a portion of the drive cable, causing that portion of the drive cable to axially shorten (e.g., become loose, thereby increasing the radius of the coil). For some applications, the impeller is configured to rotate counterclockwise when viewed from the proximal end to the distal end of the impeller, and the coiled wire in each layer of the drive cable is configured to be placed in the left hand position. When the impeller rotates counterclockwise, the counter-pressure applied to each layer of the drive cable's coils causes them to partially unwind, thereby shortening each layer of the drive cable. Alternatively, the impeller is configured to rotate clockwise when viewed from the proximal end to the distal end of the impeller, and the coils in each layer of the drive cable are configured to be right-handed.

[0260] Refer again FIG. 6A and 6B These demonstrate, according to some applications of the invention, the range of axial reciprocating motion of the impeller within the frame 34 during the cardiac cycle. As described above, FIG. 6A The impeller is positioned closest to the heart during the cardiac cycle (typically, the impeller is positioned in this order during systole), and FIG. 6B This indicates the impeller's furthest position during the cardiac cycle (typically, the impeller is positioned this way during diastole). For example... FIG. 6A As shown, for some applications, at the closest position to the impeller, the proximal end of the impeller is positioned at location I. P At that location, I P Within the proximal conical segment of frame 34. (e.g.) FIG. 6B As shown, for some applications, at the farthest position of the impeller, the far end of the impeller is set at position Id, which is at the far end of the cylindrical segment of frame 34.

[0261] Refer again FIG. 10A-10CAnd with the configuration of the drive cable described with reference to these figures, typically, the drive cable is configured in the manner described above, when the impeller and drive cable begin to rotate, the length of the frame 34 does not need to accommodate distal movement of the impeller due to axial elongation of the drive cable due to device cable tightening. Note that for some applications, the drive cable does not shorten due to the drive cable support tube 140 limiting the extent to which the drive cable can unspool and thereby shorten axially (and / or for other reasons). Also, for some applications, while theoretically the drive cable would shorten if the impeller were to rotate without any fluid, in practice, the drive cable does not shorten when the impeller is rotating in the subject's blood flow. This is because, when the impeller is rotating in the subject's blood flow, the impeller is pushed distally due to the back pressure of the blood being pumped by the impeller, thereby counteracting the unspooling of the drive cable (which would cause the drive cable to shorten). For some applications, during diastole, the drive cable actually lengthens relative to when the impeller is at rest, due to the increased pressure gradient against which the impeller is pumping relative to during systole. Typically, even in such applications, at least during systole, due to the winding of the coil being configured as described above, the drive cable is configured not to become elongated relative to when the impeller is at rest.

[0262] For some applications, in addition to the direction of the coiled wire within the drive cable being configured in the manner described above, the drive cable is initially held within the frame 34 in a preloaded (i.e., pre-tensioned) state, such that even before the drive cable and impeller begin to rotate, the drive cable is already stretched. That is, even before the drive cable and impeller begin to rotate, the drive cable is in a stretched state relative to the drive cable at rest state (i.e., the state of the drive cable when no external forces are acting on the drive cable). For example, the coupling element 65 (which in some applications extends proximally, as described above with reference to FIG. 3) is configured to apply a force to the drive cable to keep the drive cable in a preloaded state. For some applications, the coupling element 65 is configured to apply a force to the drive cable to keep the drive cable in a preloaded state even when the impeller is not rotating. For some applications, the coupling element 65 is configured to apply a force to the drive cable to keep the drive cable in a preloaded state only when the impeller is rotating. FIG. 6D-FIG. 6EThe proximal bearing 116 can be engaged, for example, to hold the drive cable in a preloaded state. Typically, (a) because of the orientation of the coiled wire within the drive cable is configured in the above-described manner, and / or (b) because the drive cable is held within the frame 34 in a preloaded state, in this case, the drive cable does not become elongated when the impeller and drive cable begin to rotate, even during diastole (e.g., even when the impeller is pumping against a pressure gradient of 50-70 mmHg). For some applications, the drive cable does not become elongated during diastole until the impeller is rotating at a rotational rate that exceeds 6,000 RPM or that exceeds 8,000 RPM. For some applications, by configuring the drive cable in this manner, the amount by which the drive cable lengthens during a cardiac cycle, even when the impeller is rotating at more than 20,000 RPM, is limited to less than 5 mm (and typically less than 4 mm). Moreover, for some applications, by configuring the drive cable in this manner, the widest portion of the impeller (typically located at the center of the length of the impeller) is disposed within the proximal half of the frame 34 for more than 50% of the duration of a cardiac cycle, even when the impeller is rotating at more than 20,000 RPM.

[0263] For some applications, the ventricular assist device is configured such that there is an axial distance between the impeller position at which the impeller is at its maximum diameter and the blood inlet opening, even during diastole, even when the impeller is rotating at more than 20,000 RPM. For example, the ventricular assist device is configured such that there is an axial distance of more than 3 mm (e.g., more than 5 mm) between the impeller position at which the impeller is at its maximum diameter and the blood inlet opening during diastole, even when the impeller is rotating at more than 20,000 RPM. For some such applications, this reduces hemolysis (relative to if there were a smaller axial distance or no axial distance between the impeller position at which the impeller is at its maximum diameter and the blood inlet opening) and / or improves the efficiency of the impeller by reducing turbulence, by allowing the blood streamlines that enter the blood inlet opening to become at least partially aligned with the longitudinal axis of the impeller before being pumped by the impeller.

[0264] Typically, there are fewer coiled wires within the outer layer 136 of the drive cable than within the inner layer 138, and each wire is wider than the wires within the inner layer. For example, the ratio of the number of wires within the outer layer to the number of wires within the inner layer can be between 2:3 and 2:5. For some applications, the outer layer contains 4-8 wires, while the inner layer contains 10-14 wires. For some applications, the ratio of the wire diameter within the outer layer to the wire diameter within the inner layer is between 3:2 and 5:2. For some applications, the wire diameter within the outer layer is between 0.15 mm and 0.2 mm, while the wire diameter within the inner layer is between 0.075 mm and 0.125 mm. Typically, the coiled wires of both layers are made of an alloy. For some applications, the inner diameter of the drive cable (i.e., the diameter of the lumen 132) is between 0.4 mm and 0.7 mm. Further typically, the outer diameter of the drive cable (defined by the outer layer 138) is between 1 mm and 1.2 mm. For some applications, the drive cable 130 has a total length that is greater than 1 m (e.g., greater than 1.1 m), and / or less than 1.4 m (e.g., less than 1.3 m), e.g., 1-1.4 m, or 1.1-1.3 m. Typically, the diameters of the lumens 122 and 133 are substantially similar to the diameter of the lumen 132.

[0265] For some applications, the drive cable includes a first (distal) portion and a second (proximal) portion. Typically, the first portion is configured to be disposed in the aortic arch of the subject, while the second portion is configured to be disposed along the descending aorta, and typically extends to the motor unit 23, outside the subject’s body. Typically, at locations where the drive cable 130 undergoes significant bending, such as at the aortic arch, it is desirable for the drive cable to be relatively flexible. However, drive cables with greater flexibility are also typically more axially stretchable than drive cables with lesser flexibility. Thus, for some applications, there is a tradeoff between desiring the drive cable to be flexible enough to conform to the curvature of the aortic arch, but on the other hand, not desiring the drive cable to undergo significant axial stretching, which can result in loss of control over the axial position of the impeller. For some applications, respective portions of the drive cable have respective degrees of flexibility. For example, a first portion of the drive cable, configured to be disposed in the aortic arch, can have a first flexibility, while a second portion of the drive cable, configured to be disposed in the descending aorta, can have a second flexibility, the first flexibility being greater than the second flexibility.

[0266] For some applications, the distal portion of the drive cable is configured to have more flexibility than the proximal portion, due to the coils of wire 134 in the distal portion having different parameters than those used in the proximal portion. For some applications, the distal portion has substantially similar parameters to those described above (i.e., with respect to the inner and outer layers). For some applications, the proximal portion of the guide wire includes a single layer of coiled wire. Typically, there is less coiled wire in the proximal portion of the drive cable than in the outer layer of the distal portion of the drive cable. Typically, the ratio of the number of wires in the outer layer of the distal portion of the drive cable to the number of wires in the proximal portion of the drive cable is between 3:2 and 5:2. For some applications, there are 3 to 6 wires in the proximal portion of the drive cable. Typically, the diameter of the coiled wire in the proximal portion of the drive cable is even greater than the diameter of the coiled wire in the outer layer of the distal portion of the drive cable. For some applications, the ratio of the wire diameter in the proximal portion to the wire diameter in the outer layer of the distal portion is between 3:2 and 5:2. For some applications, the wire diameter in the distal portion of the drive cable is between 0.2 mm and 0.35 mm. Typically, the inner and outer diameters of both the distal and proximal portions of the drive cable are similar (or the same) to each other, and are typically as described above.

[0267] Referring now to FIG. 10D , which is a schematic illustration of a first outer tube 140 according to some applications of the present invention, which acts as a drive cable support tube. For some applications, the drive cable support tube includes an outer layer 141 and an inner layer 144, each typically made of a biocompatible polymer material, and coils 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 mixture of PTFE and / or polyimide), and the coils are made of an alloy (e.g., stainless steel). Typically, the inner layer includes a material configured to provide a low level of friction and high wear resistance. Furthermore, typically, the outer layer is configured to provide additional strength to the drive cable support tube, while still providing sufficient flexibility to the drive cable support tube to enable it to conform to, for example, the curvature of the aortic arch. Typically, the coils are configured such that the substantially circular cross-section of the drive cable support tube is maintained even within areas where the drive cable support tube experiences significant bending (e.g., within the aortic arch). Typically, without the coils, the drive cable support tube would have a tendency to flatten and form an elliptical cross-section within these areas.

[0268] Referring now to FIG. 11A , FIG. 11B , FIG. 11C , FIG. 11D and FIG. 11Ewhich are schematic illustrations of devices and methods for cleaning the drive cable 130, the radial bearings 116, 118, and / or the impeller bushing 58 of a ventricular assist device 20 in accordance with some applications of the present invention.

[0269] Referring first to FIG. 11A , typically, the axial shaft and the drive cable define a continuous lumen 132 therethrough. For some applications, the left ventricular device is guided to the aorta and the left ventricle by placing the axial shaft and cable over the guide wire 10 (as described above) such that the guide wire is disposed within the lumen 132. Typically, the guide wire is inserted through a duckbill valve 390 (or other hemostatic valve) disposed at the distal end of the distal tip portion of the distal tip member 107. The guide wire passes through the lumen 122 (of the distal tip portion) and then into the lumen 132 defined by the axial shaft at this point. The guide wire 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 guide wire passes through the lumen 133 defined by the pin 131, which is disposed outside of the subject's body even after the distal end of the ventricular assist device 20 is inserted into the subject's left ventricle. Typically, when the distal end of the ventricular assist device is disposed inside the subject's left ventricle, the guide wire is retracted from the subject's body by pulling the guide wire out of the proximal end of the lumen 133. Subsequently, the axial position of the driven magnet 82 (within which the pin 131 is disposed) is fixed so as to be disposed between the drive magnets 77, as shown in FIG. 7A . For example, the portion of the motor unit 23 in which the driven magnet is disposed can be coupled to the portion of the motor unit in which the drive magnets 77 are disposed using a detent element 150 (as shown in FIG. 11B . For some applications, the technique described below with reference to FIG. 23A-FIG. 23C is used to insert the guide wire into the distal tip member 107. For some applications, by using the lumen 132 of the axial shaft and cable in the manner described above, there is no need to provide an additional guide wire guide for use during insertion of the left ventricular assist device 20.

[0270] For some applications, the lumen 132 is additionally used by the cleaning system 29 (as shown in FIG. 1A of the ventricular assist device. Typically, both the first outer tube 140 and the second outer tube 142 remain stationary during rotation of the drive cable. For some applications, the cleaning system 29 is used via the inlet port 86 and the outlet port 88 (in FIGS. 7A-7Bii , FIG. 11B and FIG. 11CThe control system 200 (shown in FIG. 2) controls the flow of cleaning fluid (e.g., a fluid containing glucose or dextrose). The fluid is configured to remove air from the space between the drive cable and the outer tube, and / or to reduce friction between the drive cable 130 (which rotates) and the outer tube 140 (which remains stationary during rotation of the drive cable), and / or to reduce friction between the axial shaft 92 and the proximal bearing 116 and / or the distal bearing 118.

[0271] Referring again to FIG. 11A For some applications, cleaning fluid is pumped between the first outer tube 140 and the second outer tube 142, and there is an opening 146 in the first outer tube near the proximal bearing. For some applications, cleaning fluid is pumped through a cleaning fluid channel 226 defined between the first outer tube and the second outer tube, as described below with reference to FIG. 21 For further detail. For some applications, cleaning fluid flows between the first outer tube 140 and the drive cable 130 via the opening 146, as indicated by cleaning fluid flow arrows 148 in FIG. 11A This way, the interface between the drive cable 130 (which rotates) and the outer tube 140 (which acts as a drive cable bearing tube and remains stationary during rotation of the drive cable) is cleaned. For some applications, some of the cleaning fluid additionally flows to the interface between the axial shaft and the proximal bearing 116, cleaning that interface (and / or reducing friction at that interface), as indicated by cleaning fluid flow arrows 149 in FIG. 11A Typically, flow of cleaning fluid in the direction of arrows 149 also prevents blood from flowing into the interface between the axial shaft and the proximal bearing.

[0272] As described above (with reference to FIGS. 10A-10C ), the drive cable typically includes a plurality of coiled wires. For some applications, cleaning fluid enters the cavity 132 defined by the drive cable via gaps in the coiled wires. Once the cleaning fluid is disposed within the cavity 132, the cleaning fluid flows in the proximal direction and the distal direction, as indicated by arrows 151 in FIG. 11A As indicated by arrows 152 in FIG. 11A Typically, cleaning fluid flowing in the distal direction exits the distal end of the cavity 132 and flows toward the cavity 122 defined by the distal tip portion. At the end of the distal tip portion, the cleaning fluid is typically prevented from exiting the distal tip portion by a duckbill valve 390. Thus, some of the cleaning fluid typically flows to the interface between the axial shaft and the distal bearing 118, cleaning that interface (and / or reducing friction at that interface), as indicated by cleaning fluid flow arrows 154 in FIG. 11A Typically, flow of cleaning fluid in the direction of arrows 154 also prevents blood from flowing into the interface between the axial shaft and the distal bearing.

[0273] As described above, once the cleaning fluid is placed within the cavity 132, the cleaning fluid flows in both the proximal and distal directions, such as... FIG. 11A As shown by arrow 151. Now refer to... FIG. 11B Typically, at the proximal end of the ventricular assist device 20, the cleaning fluid flows out of the proximal end of the cavity 132 in the direction of arrow 156, and subsequently out of the proximal end of the cavity 133 defined by pin 131. In some applications, the cleaning fluid then flows in the direction of arrow 157 and around the driven magnet 82 to reduce frictional forces on the driven magnet 82. In some applications, the cleaning fluid then flows out of the outlet port 88 in the direction of arrow 158. Typically, the cleaning fluid is then disposed of. Alternatively, the cleaning fluid is pumped back into the device via the inlet port 86.

[0274] Referring to the above description of the cleaning process typically used for the ventricular assist device 20, it should be noted that cavities 122, 132 and 133 (as described above, which were previously used to facilitate insertion of the device over the guide wire 10) typically serve as flow channels for cleaning fluid during use of the ventricular assist device.

[0275] Now for reference FIG. 11C For some applications, the ventricular assist device includes an additional cleaning fluid inlet port 89, typically used to pump cleaning fluid into a channel 224 between the delivery catheter 143 and the outer tubing 142. For some applications, the cleaning fluid is pumped into this channel at a sufficiently low pressure to allow aortic blood pressure to still be detected via this channel, as described elsewhere in this application. For some applications, instead of continuously pumping cleaning fluid into channel 224, fluid is pumped into the channel periodically to flush it. For some applications, port 89 and channel 224 are used for aortic pressure sensing. For example, pressure sensor 216 (which...) FIG. 1A (Illustrated in the diagram) can be located within channel 224, within port 89, and / or at different locations in fluid communication with channel 224.

[0276] refer to FIG. 11D and FIG. 11EFor some applications, the axial shaft 92 includes a purge fluid hole configured to allow purge fluid to flow out of a cavity 132 defined by the axial shaft 92. For some applications, the axial shaft defines a purge fluid hole 190 near the distal bushing 58 of the impeller 50. As described above, for some applications, the distal bushing is configured to be slidable relative to the axial shaft. For some such applications, the interface between the distal bushing and the axial shaft is purged by purge fluid flowing out of the purge fluid hole 190. For some applications, the axial shaft defines a hole 192 near the distal radial bearing 118. For some such applications, the interface between the distal radial bearing and the axial shaft is purged by purge fluid flowing out of the purge fluid hole 192. For some applications, the axial shaft defines a hole 194 near the proximal radial bearing 116. For some such applications, the interface between the distal radial bearing and the axial shaft is purged by purge fluid flowing out of the purge fluid hole 194.

[0277] Reference is now made to FIG. 12A and FIG. 12B which are schematic illustrations of a ventricular assist device 20 including an inner liner 39 lining the interior of the frame 34 that houses the impeller 50, in accordance with some applications of the present application. (The inner liner 39 and the pump outlet tube 24 on the side of the device facing out of the page are shown as transparent in FIGS. 12A-12B for illustrative purposes.) For some applications, the inner liner 39 is disposed within the frame 34 so as to provide a smooth inner surface through which blood is pumped by the impeller. Typically, by providing a smooth surface, the covering material reduces hemolysis caused by the impeller pumping blood relative to pumping blood between the impeller and the struts of the frame 34. For some applications, the inner liner includes polyurethane, polyester, and / or silicone. Alternatively or additionally, the inner liner includes polyethylene terephthalate (PET) and / or polyether block amide (PEBAX®).

[0278] Typically, the inner liner is disposed over at least the inner surface of the cylindrical portion of the frame 34 (e.g., the cylindrical portion is shown in FIGS. 12A-12B ). For some applications, the pump outlet tube 24 also covers the cylindrical portion 38 of the frame 34, e.g., around the outside of the frame, such that the pump outlet tube 24 and the inner liner 39 overlap over at least 50% of the length of the inner liner, e.g., over the entire length of the cylindrical portion of the frame 34, e.g., as shown in FIG. 12A . For some applications, there is only partial overlap between the pump outlet tube 24 and the inner liner 39, e.g., as shown in FIG. 12BThe pump outlet tube 24 can overlap the inner liner along less than 50% of the length of the inner liner (e.g., less than 25%). For some such applications, during insertion of the ventricular assist device 20 into a subject, the impeller is advanced distally within the frame 34 such that the impeller is not disposed within the overlap region between the pump outlet tube and the inner liner, such that there is no longitudinal position in which the impeller, pump outlet tube 24, frame 34, and inner liner 39 all overlap one another. As noted above, with reference to FIG. 1D For some applications, the pump outlet tube 24 extends to the end of the distal tapered portion 40 of the frame, and the pump outlet tube defines a plurality of lateral blood inlet openings. For some such applications, the cylindrical portion of the frame is lined with the inner liner 39.

[0279] Typically, over any overlap region between the inner liner 39 and the pump outlet tube 24, the inner liner is shaped to form a smooth surface (e.g., to reduce hemolysis, as noted above), and the pump outlet tube 24 is shaped to conform to the struts of the frame 34 (e.g., as shown in the cross-section of FIG. 12A Typically, over the overlap region between the inner liner 39 and the pump outlet tube 24, the pump outlet tube and the inner liner are coupled to one another, e.g., via a vacuum, via an adhesive, and / or using a thermoforming process, e.g., as described below.

[0280] For some applications, the inner liner 39 and the pump outlet tube 24 are made of different materials. For example, the inner liner can be made of polyurethane, while the pump outlet tube can be made of polyether block amide (PEBAX®). Typically, the material from which the inner liner is made has a higher thermoforming temperature than the material from which the pump outlet tube is made. For some applications in which the inner liner and the pump outlet tube overlap along at least a portion of the frame 34 (e.g., along the cylindrical portion of the frame 34), the pump outlet tube and the inner liner are bonded to one another and / or to the frame in the following manner. Initially, the inner liner is placed over a mandrel. Subsequently, the frame is placed over the inner liner. Subsequently, the pump outlet tube 24 is placed around the outside of the frame. For some applications, in order for the pump outlet tube 24 to be molded to conform to the struts of the frame 34 without causing the inner liner to deform, the frame is heated to a temperature that is higher than the thermoforming temperature of the pump outlet tube 24 but lower than the thermoforming temperature of the inner liner 39. Typically, the frame is heated from the inside of the frame using a mandrel. Typically, while the frame is heated to the above-mentioned temperature, an outer tube (which is typically made of silicone) exerts pressure on the pump outlet tube 24, causing the pump outlet tube 24 to be pushed radially inward so as to conform to the shape of the struts of the frame, as shown in the cross-section of FIG. 12A For some applications, the combination of the frame, the inner liner, and the portion of the pump outlet tube 24 that is disposed around the frame is subsequently shaped to the desired shape and size using a setting technique known in the art.

[0281] For some applications (not shown), the density of the frame struts at the distal end of the columnar portion of the frame is greater than the density of the struts in other parts of the columnar portion of the frame. For some such applications, the increased density of the frame struts at the distal end of the columnar portion of the frame facilitates the bonding of the liner and / or pump outlet pipe to the frame. For some applications, the liner and / or pump outlet pipe does not extend all the way to the end of the columnar portion of the frame, for example, as referenced... FIG. 13 As described above. For some such applications, at the longitudinal position along the columnar section of the frame, where the liner and / or pump outlet pipe terminates, the density of the frame supports increases relative to other positions along the columnar section of the frame.

[0282] Now for reference FIG. 13 This is a schematic diagram of a ventricular assist device 20 according to some applications of the present invention, wherein at least the distal portion 333 of the cylindrical portion 38 of the frame 34 is not covered. For some applications, during the axial reciprocating motion cycle of the impeller, even when the impeller is positioned at its furthest point within the frame 34, the portion of the impeller at its maximum span will not advance beyond a given position within the cylindrical portion of the frame (e.g., as referenced above). FIGS. 10A-10C (As described above). For some applications, a portion of the frame (which extends distally beyond that location) is not covered by the pump outlet pipe 24 or the liner 39. (Note that for illustrative purposes, the frame is shown without the liner 39. However, for some applications, the frame is lined with the liner 39. Typically, even in such applications, the distal portion 333 of the columnar section of the frame is not covered by the pump outlet pipe 24 or the liner 39.)

[0283] For some applications, the uncovered distal portion of the columnar section of the frame effectively widens the entrance because (e.g.) FIG. 13 (As indicated by the blood flow arrows in the diagram) Blood flows into the cylindrical portion of the frame from the side. For some applications, this reduces hemolysis caused by the impeller pumping blood. Optionally or additionally, the diameter of pump portion 27 can be reduced when the pump portion is in its radially constrained configuration by leaving a portion of the cylindrical portion of the frame uncovered. For example, the pump portion can be radially constrained such that the widest portion of the impeller overlaps with the uncovered portion of the cylindrical portion of the frame to reduce the diameter of the pump portion of the ventricular assist device (as opposed to if the widest portion of the impeller overlaps with the covered portion of the cylindrical portion of the frame, such that the widest portion of the impeller overlaps with the frame and the covering material).

[0284] For some applications, ventricular assist devices are configured such that, even during diastole, there is an axial distance between the impeller position at its maximum diameter and the blood inlet opening. For example, a ventricular assist device is configured such that, during diastole, there is an axial distance exceeding 3 mm (e.g., exceeding 5 mm) between the impeller position at its maximum diameter and the blood inlet opening (e.g., as referenced above). FIGS. 10A-10C (as described above). For some such applications, this reduces hemolysis (relative to a smaller or no axial distance between the impeller position at its maximum diameter and the blood inlet opening) and / or improves impeller efficiency by reducing turbulence, by allowing the blood flow lines entering the blood inlet opening to become at least partially aligned with the longitudinal axis of the impeller before being pumped by the impeller.

[0285] Now for reference FIG. 14 This is a schematic diagram (showing a cross-sectional view of the left ventricle) of a ventricular assist device 20 placed within the left ventricle 22 of a subject according to some applications of the present invention. For illustrative purposes, FIG. 14 The aortic valve 26 is shown covering a cross-section of the left ventricle, although the aortic valve lies in a different plane than the plane of the main sectional view. Also referenced... FIGS. 15A-15D These figures are schematic diagrams of the distal end element 107 of a ventricular assist device according to some applications of the invention, which is at least partially curved to define a curvature resembling a question mark, and also refer to... FIG. 16A and FIG. 16B These figures are arrangements placed in the left ventricle of a subject according to some applications of the present invention. FIGS. 15C-15D A schematic diagram of a ventricular assist device.

[0286] In some applications, the ventricular assist device is guided by a guide wire, through which it is inserted toward the apex 342 of the left ventricle. The wall of the left ventricle can be considered to consist of a septal wall 338 (which separates the left ventricle from the right ventricle 340), a posterior wall 336 (from which papillary muscles 341 protrude, and the mitral valve device is positioned above the posterior wall 336), and a free wall 334, each of which occupies approximately one-third of the circumference of the left ventricle (e.g., ...). FIG. 14the dashed line shown in the middle third of the left ventricle). Typically, it is undesirable for the distal tip element (or any other portion of the ventricular assist device) to come into contact with the septal wall, as this can potentially lead to a risk of arrhythmia. More typically, it is desirable to maintain a distance between the distal tip element (and any other portion of the ventricular assist device) and the posterior wall, so as not to interfere with the mitral valve apparatus, and to prevent the mitral valve apparatus from interfering with the function of the ventricular assist apparatus. Thus, the ventricular assist device is typically guided towards the apex in such a way that, if and when the distal tip element contacts the inner wall of the left ventricle, the ventricular assist device contacts the free wall 334, as FIG. 14 and FIGS. 16A-16B indicated.

[0287] Typically, as described above, the ventricular assist device is introduced into the subject's ventricle via a guide wire. The distal tip portion 120 defines a lumen 122 such that the distal tip portion is maintained in a straightened configuration during introduction of the ventricular assist device into the subject's ventricle. For some applications, the distal tip portion is configured to assume its curved shape when the guide wire is removed. Note that, FIGS. 15A-15D indicates the shape that the distal tip portion 120 initially forms. Typically, due to the insertion of the guide wire through the lumen 122 (thereby temporarily straightening the distal portion), the curvature of the distal tip portion when deployed within the subject's left ventricle is less than the curvature indicated in at least some of FIGS. 15A-15D For example, FIG. 15C indicates that the curvature of the distal tip portion is such that the curved portion of the distal tip portion forms a complete loop. However, FIG. 15C the distal tip portion of the ventricular assist device is shown in FIG. 16A deployed within the subject's left ventricle, and the distal tip portion does not form a complete loop.

[0288] As described above, the distal tip portion 120 typically forms a portion of the distal tip element 107, which also includes an axial shaft receiving tube 126. Typically, the distal tip element 107 is configured such that, in its unconstrained configuration (i.e., in the absence of any force acting on the distal tip portion), the distal tip element is at least partially curved. For some applications, the distal tip element 107 has a proximal straight portion 346 (which typically includes at least a portion of the axial shaft receiving tube 126) within a given plane. 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 away from the longitudinal axis 348 in a first direction, and then passes through an inflection point and curves in an opposite direction relative to the longitudinal axis 348. For example, as FIGS. 15A-15B indicated, within the plane of the paper, the distal tip element first curves towards the top of the paper, then curves towards the bottom of the paper, and as FIGS. 15C-15DAs shown, in the plane of the paper, the distal tip element first bends toward the bottom of the paper, and then bends toward the top of the paper. Typically, when shaped as shown FIGS. 15A-15D As shown, when shaped as shown, the distal tip element defines an overall curvature similar to a question mark or tennis racquet, the distal tip element defining a hump 351 on one side of the longitudinal axis of the straight proximal straight portion of the distal tip element. For some applications, the hump is shaped approximately as a semi-ellipse. (It should be noted that in this context, the term "semi-ellipse" includes a semi-circle. It should also be noted that in some cases, the tip does not define a precise semi-ellipse, but rather a hump that is substantially similar to a semi-ellipse.)

[0289] As shown FIGS. 15A-15B For some applications, after passing the inflection point, the distal tip element continues to bend such that the distal tip element crosses back over the longitudinal axis 348. FIG. 15A An example is shown in which the end of the distal tip element has not yet crossed back over the longitudinal axis, and there is a large gap between the distal end of the distal tip element and the proximal end of the curved portion. FIG. 15B An example is shown in which the end of the distal tip element has crossed back over the longitudinal axis, and there is a small gap between the distal end of the distal tip element and the proximal end of the curved portion. As shown FIGS. 15C-15D As shown (these figures are a cross-sectional view and an isometric view, respectively, of the same shaped distal tip element), for some applications, after passing the inflection point, the tip does not bend such that the distal tip element crosses back over the longitudinal axis 348. Rather, all of the curvature of the curved portion of the distal tip element occurs on one side of the longitudinal axis 348.

[0290] Referring to FIG. 15C Typically, a hemostatic valve (e.g., duckbill valve 390) is disposed within the distal segment of the distal tip portion 120, and is configured to prevent blood from flowing into the lumen 122. Typically, the duckbill valve has a maximum width of less than 3 mm, e.g., less than 2 mm, and typically, the entire duckbill valve is disposed within the distal segment of the distal tip portion, which is disposed within the distal-most 10 mm of the distal tip portion, e.g., the distal-most 5 mm of the distal tip portion. For some applications, the duckbill valve faces proximally (i.e., such that the wide inlet of the valve faces the distal end of the distal tip portion, and such that the narrow tip of the valve faces away from the distal end of the distal tip portion 120). Typically, when deployed within the left ventricle of a subject, the curvature of the curved portion of the distal tip element 107 is configured to provide a trauma-free tip for the ventricular assist device 20. More typically, the distal tip element is configured to separate the inlet opening 108 of the ventricular assist device from the wall of the left ventricle.

[0291] Referring now to FIG. 16A andFIG. 16B It is first noted that these illustrations show cross-sectional views of the left ventricle 22, with the septal wall 338 disposed to the left of the page and the free wall 334 disposed to the right of the page. In this view, the left atrium 359 and the left atrial appendage 358 are visible above the left ventricle, and the right ventricle 340 is visible to the left of the left ventricle. Note that the view of the aorta and left ventricle shown in FIGS. 16A-16B (and FIGS. 17Ai-17D ) is different from the view shown in, for example, FIG. 1B FIG. 1B are schematic illustrations provided for purposes of illustration and do not necessarily depict the proportions and orientations of the ventricular assist device relative to the anatomical structures appropriately.

[0292] 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 placed against the apex of the subject's left ventricle. Typically, the distal tip element is configured to separate the blood inlet opening from the septal wall of the subject's left ventricle when the distal tip element contacts the apex of the subject's left ventricle.

[0293] Typically, the distal tip element 107 is inserted into the left ventricle such that the hump 351 is humped toward the septal wall 338. When disposed in this configuration, in response to the distal tip element 107 being pushed toward the apex (e.g., due to the physician advancing the device or in response to movement of the left ventricle), the blood inlet opening 108 is typically pushed in the direction of the free wall 334 and away from the septal wall 338 (in the direction of the arrow shown in FIG. 16B ). Typically, this is due to the proximal straight portion 346 pivoting about the curved portion of the question mark shape, as shown. By contrast, other shaped tips, if disposed in similar orientations, can result in the blood inlet opening being pushed toward the septal wall. For example, if the distal tip element has a pigtail tip (in which the tip is curved in a single curvature direction), the pigtail tip is oriented such that the pigtail curvature is to the free wall side of the longitudinal axis of the straight portion of the distal tip element, then pushing the tip distally typically causes the blood inlet opening to be directed toward the septal wall due to the pigtail curvature loop tightening.

[0294] Referring to all of the figures in FIGS. 14-16B , it is noted that the scope of the present invention includes the use of a question mark or tennis racket shaped distal tip element in combination with any ventricular assist device, even without other features and / or portions of the distal tip element 107 (e.g., the axial shaft receiving tube 126). It is also noted that typically, the curvatures of the distal tip portion are all in a single plane.

[0295] Reference is now made to FIG. 17Ai and FIG. 17Aii ​, which are schematic views of ventricular assist device 20 having balloon 220 disposed on distal tip element 107 of the device, the balloon configured to facilitate movement of axial shaft 92 relative to the wall of the ventricle, according to some applications of the present application.

[0296] As noted above, axial shaft 92 typically passes through the axis of impeller 50 via the cavity 62 of the impeller. More typically, the axial shaft is rigid, e.g., a rigid tube. The axial shaft is itself radially stabilized via proximal radial bearing 116 and distal radial bearing 118. In turn, the axial shaft radially stabilizes the impeller against the inner surface of frame 34 by passing through the cavity 62 defined by the impeller. For some applications, the axial shaft enters axial shaft receiving tube 126 of distal tip element 107. Typically, if the axial shaft is bent, the frictional forces between the axial shaft and the distal and radial bearings increase. Thus, it is typically desirable for the axial shaft to remain in a straight configuration. For some applications, balloon 220 provides freedom of movement of the distal end of the distal tip element relative to the wall of the left ventricle in a manner that does not cause the proximal end of the distal tip portion (which defines the axial shaft receiving tube) to experience substantial movement. For example, as shown by the arrow near the apex 342 in FIG. 17Ai and FIG. 17Aii , the balloon can rotate relative to the apex without causing substantial movement of the axial shaft receiving tube. Thus, even if the balloon experiences movement relative to the apex (as shown in the transition from FIGS. 17Ai-17Aii , the axial shaft remains in a substantially straight configuration. For some applications, the balloon 220 is filled using a flushing fluid, e.g., using the techniques described with reference to FIG. 13 D of US2020 / 0237981, which is incorporated herein by reference.

[0297] Reference is now made to FIG. 17Bi and FIG. 17Bii , which are schematic views of ventricular assist device 20 having joint 230 configured to facilitate pivoting of the distal tip portion 120 of the device relative to its axial shaft, according to some applications of the present application. As noted above, for some applications, distal tip element 107 includes axial shaft receiving tube 126 as well as distal portion 120. For some applications, joint 230 allows distal tip portion 120 to move relative to axial shaft receiving tube 126. For example, joint 230 can be a ball and socket joint as shown, and / or it can be a rotational joint, and / or a gimbal joint. Thus, even if the distal tip portion experiences movement relative to the apex 342 of the left ventricle (as shown in the transition from FIGS. 17Bi-17Bii , the axial shaft 92 remains in a substantially straight configuration. For some such applications, distal tip portion 120 is shaped as described above.

[0298] Reference is now made to FIG. 17C which is a schematic illustration of a ventricular assist device according to some applications of the present application, the outer tube 140 and / or 142 is shaped with a predetermined curvature such that when the axial shaft is disposed within the left ventricle 22 of the subject, the axial shaft 92 of the ventricular assist device is held in a substantially straight configuration.

[0299] As mentioned above with reference to FIGS. 10A-10C for some applications, the drive cable 130 is disposed within a first outer tube 140, which is configured to act as a drive cable support tube, which remains stationary when the drive cable undergoes rotational and / or axial reciprocating motion. The first outer tube is configured to effectively act as a support along the length of the drive cable. For some applications, the first outer tube 140 is disposed within a second outer tube 142. For some applications, at least one of the first outer tube and the second outer tube is shaped such that the portion of the outer tube disposed within the aortic arch has a predetermined radius of curvature RC, which is greater than 18 mm and / or less than 32 mm (e.g., less than 24 mm), for example, 18-32 mm or 18-24 mm. For some applications, by defining such a radius of curvature, the axial shaft enters the left ventricle at such an angle that when the distal tip portion of the ventricular assist device is disposed in the vicinity of the apex 342, the axial shaft is in a substantially straight configuration.

[0300] Reference is now made to FIG. 17D which is a schematic illustration of a ventricular assist device 20 according to some applications of the present application, the device has a distal tip 240, which is configured to anchor to the tissue of the apex 342 of the left ventricle. For some applications, the distal tip 240 is a screw shaped element (e.g., a screw cone shaped element, as shown), and the distal tip is configured to be screwed into the tissue of the apex in order to anchor the distal end of the ventricular assist device to the apex. Typically, anchoring the distal tip in the apex reduces the movement of the pump portion 27 relative to the internal structure of the left ventricle, and thereby reduces the risk of damage to the internal structure of the left ventricle that can be caused by such movement.

[0301] Reference is now made to FIG. 18A , FIG. 18B and FIG. 18C which are schematic illustrations of a distal radial support 118 of a ventricular assist device according to respective applications of the present application.

[0302] Reference is made to FIG. 18AFor some applications, the radial bearing is disposed within a bearing housing 119. For some such applications, the radial bearing and the bearing housing are made of respective, different from each other materials. For example, the radial bearing can be made of a first material having a relatively high hardness (e.g., ceramic), and the bearing housing can be made of a second material that is relatively easy to shape into a desired shape, such as a metal or an alloy (e.g., stainless steel, cobalt-chrome, and / or nitinol). For some applications, the proximal radial bearing 116 is also disposed within a bearing housing, where the proximal radial bearing and the bearing housing are made of respective, different from each other materials (in a manner generally similar to that described with reference to the distal radial bearing 118). As described above, for some applications, the ventricular assist device includes a distal extension 121 configured to reinforce a region of the distal tip element into which the distal end of the axial shaft 92 moves (e.g., the axial shaft receiving tube 126 or a portion thereof described below). For applications in which the distal radial bearing 118 is disposed within a bearing housing 119, the distal extension 121 typically includes an extension that extends from the bearing housing 119 rather than from the distal radial bearing itself. As described above, typically, at the distal end of the frame 34, the distal strut junction 33 is placed into a groove defined by an outer surface of the distal radial bearing 118, the groove being shaped to conform to the shape of the distal strut portion. For some applications, the outer surface of the bearing housing (rather than the outer surface of the bearing) is shaped to define such a groove (the groove being defined by the outer surface of the bearing housing and the outer surface of the radial bearing being flush with each other). For some such applications, the outer surface of the bearing housing is shaped to define a groove that is shaped to conform to the shape of the distal strut portion, and the outer surface of the radial bearing is shaped to conform to the shape of the proximal strut portion. For some applications, the outer surface of the bearing housing is shaped to define a groove that is shaped to conform to the shape of the proximal strut portion, and the outer surface of the radial bearing is shaped to conform to the shape of the distal strut portion. FIG. 18A and FIG. 18B Reference number 127 in

[0303] Reference is now made to FIG. 18B For some applications, a layer of material 123 is disposed between the radial bearing 118 and the bearing housing 119. For some applications, the material is configured to allow some movement of the radial bearing relative to the bearing housing, and / or to cushion such movement. For example, the layer of material can include a layer of elastomeric material. For some applications, the proximal radial bearing 116 has a similar configuration, in which a material (e.g., an elastomeric material) is disposed between the radial bearing and the bearing housing, the material being configured to allow some movement of the radial bearing relative to the bearing housing, and / or to cushion such movement. For some such applications, by allowing movement between the radial bearing and the bearing housing, the layer of material allows some movement of the rigid axial shaft relative to the frame 34. For some applications, in this manner, the axial shaft 92 is allowed to become slightly misaligned with the longitudinal axis of the frame.

[0304] Reference is made to FIG. 18CFor some applications, the outer surface 125 of the distal radial bearing 118 that is contiguous with the inner surface of the bearing housing 119 has a convex curvature. For some applications, the convexly curved outer surface of the bearing is configured to allow some movement of the radial bearing relative to the bearing housing. For some applications (not shown), the inner radial surface of the bearing housing that is contiguous with the outer surface of the bearing has a convex curvature, e.g., allowing some movement of the radial bearing relative to the bearing housing. For some applications, the proximal radial bearing 116 has a similar configuration, in which the outer surface of the bearing and / or the inner radial surface of the bearing housing has a convex curvature. For some such applications, the above-described shape of the bearing and / or bearing housing allows movement of the rigid axial shaft relative to the frame 34 by allowing movement between the radial bearing and the bearing housing. For some applications, in this way, the axial shaft is allowed to become slightly misaligned with the longitudinal axis of the frame.

[0305] For some applications, the length of the radial bearing allows movement of the rigid axial shaft relative to the frame 34 such that the axial shaft is allowed to become slightly misaligned with the longitudinal axis of the frame. For example, the length of each of the proximal and distal radial bearings can be less than 2 mm, less than 1.5 mm, or less than 1 mm, e.g., 0-1.5 mm, or 0.5-1 mm.

[0306] Reference is now made to FIG. 19A , which is a schematic illustration of a ventricular assist device 20 according to some applications of the present application, the pump outlet tube 24 of which is configured to become curved when blood is pumped through the pump outlet tube, and the pump outlet tube is rotatable relative to the distal tip portion 120 of the ventricular assist device. Reference is also made to FIG. 19B , which is a schematic illustration of the pump outlet tube 24 of FIG. 19A , without other components of the ventricular assist device, according to some applications of the present application. Reference is additionally made to FIG. 19C , which is a schematic illustration of FIGS. 19A-19B , a ventricular assist device 20 disposed within the aorta 30 and left ventricle 22 of a subject, according to some applications of the present application. Note that the view of the aorta and left ventricle shown in FIG. 19C differs from the view shown in, e.g., FIG. 1B . FIG. 1B are schematic illustrations that are provided for purposes of illustration only, and are not necessarily to scale or to accurately depict the orientation of the ventricular assist device relative to the anatomical structures. Note also that the view of the aorta and left ventricle shown in FIG. 19C differs from the view shown in, e.g., FIGS. 16A-16B and FIGS. 17Ai-17D . FIG. 19C shows a cross-sectional view of the left ventricle, in which the posterior wall 336 is disposed on the left side of the page, and the free wall 334 is disposed on the right side of the page.

[0307] As described above, for some applications, along a proximal portion of the pump outlet tube 24, the frame 34 is not disposed within the tube, and thus the tube is not supported in the open state by the frame 34. The tube 24 is typically made of a collapsible material that is impermeable to blood. For example, the tube 24 can include polyurethane, polyester, and / or silicone. Alternatively or additionally, the tube is made of polyethylene terephthalate (PET) and / or polyether block amide (PEBAX®). Typically, the proximal portion of the tube is configured to be placed such that it is disposed at least partially within the subject's ascending aorta. For some applications, the proximal portion of the tube passes through the subject's aortic valve, from the subject's left ventricle into the subject's ascending aorta, as shown in FIG. 3. As described above, the tube typically defines one or more blood inlet openings 108 at the distal end of the tube, through which blood flows from the left ventricle into the tube during operation of the impeller. For some applications, the proximal portion of the tube defines one or more blood outlet openings 109, through which blood flows from the tube into the ascending aorta during operation of the impeller. The blood flow pressure through the tube typically holds the proximal portion of the tube in the open state during operation of the impeller. FIG. 1B As described above, for some applications, along a proximal portion of the pump outlet tube 24, the frame 34 is not disposed within the tube, and thus the tube is not supported in the open state by the frame 34. The tube 24 is typically made of a collapsible material that is impermeable to blood. For example, the tube 24 can include polyurethane, polyester, and / or silicone. Alternatively or additionally, the tube is made of polyethylene terephthalate (PET) and / or polyether block amide (PEBAX®). Typically, the proximal portion of the tube is configured to be placed such that it is disposed at least partially within the subject's ascending aorta. For some applications, the proximal portion of the tube passes through the subject's aortic valve, from the subject's left ventricle into the subject's ascending aorta, as shown in FIG. 3. As described above, the tube typically defines one or more blood inlet openings 108 at the distal end of the tube, through which blood flows from the left ventricle into the tube during operation of the impeller. For some applications, the proximal portion of the tube defines one or more blood outlet openings 109, through which blood flows from the tube into the ascending aorta during operation of the impeller. The blood flow pressure through the tube typically holds the proximal portion of the tube in the open state during operation of the impeller.

[0308] For some applications, the pump outlet tube 24 is pre-shaped such that, during operation of the impeller, the tube is curved when the blood flow pressure through the tube holds the proximal portion of the tube in the open state. Typically, the curvature is such that, when the proximal end of the tube is disposed within the aorta, at least a portion of the tube is disposed within the left ventricle and curves away from the posterior wall of the left ventricle, toward the apex of the left ventricle, and / or toward the free wall. Further, more typically, the curvature is such that, when the proximal end of the tube is disposed within the aorta, at least a portion of the tube is disposed within the left ventricle and curves away from the septal wall of the left ventricle, toward the apex of the left ventricle, and / or toward the free wall. For some applications, the curvature of the tube is such that a spacing between the blood inlet openings 108 and the posterior wall 336 of the left ventricle, the mitral valve leaflets 402, and / or the subvalvular portion of the mitral valve (e.g., chordae tendinae 404, papillary muscles, and / or papillary muscles 341) is maintained, as shown in FIG. 3. FIG. 19C As described above, for some applications, along a proximal portion of the pump outlet tube 24, the frame 34 is not disposed within the tube, and thus the tube is not supported in the open state by the frame 34. The tube 24 is typically made of a collapsible material that is impermeable to blood. For example, the tube 24 can include polyurethane, polyester, and / or silicone. Alternatively or additionally, the tube is made of polyethylene terephthalate (PET) and / or polyether block amide (PEBAX®). Typically, the proximal portion of the tube is configured to be placed such that it is disposed at least partially within the subject's ascending aorta. For some applications, the proximal portion of the tube passes through the subject's aortic valve, from the subject's left ventricle into the subject's ascending aorta, as shown in FIG. 3. As described above, the tube typically defines one or more blood inlet openings 108 at the distal end of the tube, through which blood flows from the left ventricle into the tube during operation of the impeller. For some applications, the proximal portion of the tube defines one or more blood outlet openings 109, through which blood flows from the tube into the ascending aorta during operation of the impeller. The blood flow pressure through the tube typically holds the proximal portion of the tube in the open state during operation of the impeller.

[0309] Typically, the tube 24 is pre-shaped in a bending mold using blow molding, or using a shaping mold after a blow molding process or a dip process. Typically, the distal portion of the tube (where the frame 34, impeller 50, and axial shaft 92 are disposed) is held in a straight and open configuration by the frame 34. The portion of the tube that is proximal to the frame 34 and that is disposed within the left ventricle is typically shaped to define the curvature described above. For some applications, the curvature is such that the angle gamma between the longitudinal axis of the tube at the proximal end of the tube and the longitudinal axis of the tube at the distal end of the tube is greater than 90 degrees (e.g., greater than 120 degrees, or greater than 140 degrees), and / or less than 180 degrees (e.g., less than 160 degrees, or less than 150 degrees), e.g., 90-180 degrees, 90-160 degrees, 120-160 degrees, or 140-150 degrees. For some applications, the curvature of the tube is such that the surface of the tube that is inside the bend defines a radius of curvature R that is greater than 10 mm, e.g., greater than 20 mm, and / or less than 200 mm (e.g., 100 mm), e.g., 10-200 mm, or 20-100 mm. (A dashed circle with a dashed line across its diameter is shown in FIG. 19B FIG. 6 to indicate the method of measuring the radius of curvature R.)

[0310] Note that, as described with reference to FIGS. 19A-19C , the pump outlet tube 24 is configured such that (a) in the absence of blood flow through the tube, the tube typically collapses in response to pressure outside the tube exceeding pressure inside the tube, and (b) when blood flows through the tube at a sufficient rate such that the pressure inside the tube exceeds the pressure outside the tube, then the tube assumes its pre-shaped curved configuration. Note also that when the tube 24 assumes its curved configuration, the portion of the drive cable 130 that is disposed within the curved portion of the tube typically also becomes curved, as shown in FIG. 19A and FIG. 19C . That is, it is the pre-shaping of the tube itself that typically causes the tube and drive cable to bend, rather than the drive cable (or a different element disposed within the tube) causing the tube to bend. Alternatively, the outer tube 140 and / or 142 (which is disposed around the drive cable) is shaped to define a bend, and the outer tube causes the drive cable and tube 24 to assume a curved shape. For some applications, both the outer tube 140 and / or 142 and the tube 24 are shaped to define a curved shape.

[0311] Referring now to FIGS. 19D-19E , these figures are schematic illustrations of a ventricular assist device 20 according to some applications of the present invention, the pump outlet tube 24 of which is configured to become curved when blood is pumped through the tube. In FIG. 19D and FIG. 19E , the tube 24 is shown without other components of the ventricular assist device (e.g., the impeller 50, frame 34, etc.) for illustrative purposes. FIG. 19Eis a schematic view of a ventricular assist device 20 disposed within the aorta 30 and left ventricle 22 of a subject in accordance with some applications of the present application. FIG. 19D FIG. 19E The view of the left ventricle shown is similar to FIG. 19C the view shown. For some applications, the inlet opening 108 and / or the outlet opening 109 are disposed in a non-axisymmetric configuration about the tube 24. Typically, the tube 24 defines the location of the inlet and / or outlet openings such that the tube 24 becomes curved and / or maintains a curvature of the tube 24 as referenced FIGS. 19A-19C above. For example, as shown, the blood inlet hole can be disposed on a side of the tube 24 that is inside a bend of the tube (or inside a desired bend of the tube). As blood flows into the blood inlet opening, this reduces the pressure in the region above the blood inlet opening, and the distal end of the tube 24 is then pulled toward this region (as indicated by arrow 310). Alternatively or additionally, the blood outlet opening 109 can be disposed on a side of the tube 24 that is at the inside of a bend of the tube (or at the inside of a desired bend of the tube). As blood flows out of the blood outlet opening, the blood impacts the aortic wall, which causes the proximal end of the tube 24 to be pushed in the opposite direction (i.e., the direction of arrow 312).

[0312] As referenced above, FIGS. 19A-19C typically, as FIG. 19E shown, the curvature of the pump outlet tube is such that a separation between the blood inlet opening 108 and the posterior wall 336 of the left ventricle, the mitral valve leaflets 402, and / or the subvalvular portion of the mitral valve (e.g., chordae 404, papillary muscle, and / or papillary muscle 341) is maintained. Typically, the curvature is such that, when the proximal end of the tube is disposed within the aorta, at least a portion of the tube is disposed within the left ventricle and curved away from the posterior wall of the left ventricle, toward the apex of the left ventricle, and / or toward the free wall. Further, more typically, the curvature is such that, when the proximal end of the tube is disposed within the aorta, at least a portion of the tube is disposed within the left ventricle and curved away from the septal wall of the left ventricle, toward the apex of the left ventricle, and / or toward the free wall.

[0313] For some applications, when deploying the ventricular assist device into the left ventricle, the distal tip portion is deployed first. As described above, the distal tip portion is typically deployed in a given orientation relative to the left ventricle anatomy. Typically, after the distal tip portion is deployed, the pump outlet tube is deployed. In some cases, the distal tip portion has been deployed in the desired orientation relative to the left ventricle anatomy, and the curved portion of the tube is not disposed in the left ventricle in the desired orientation. Thus, for some applications, the distal tip portion is rotated via the joint 212 (which allows the pump outlet tube to be rotated relative to the distal tip portion of the ventricular assist device, as FIGS. 19A-19E ​The joint can be a rotary joint and / or a ball and socket joint (e.g., as shown by ball and socket joint 230), and / or a universal joint (e.g., as shown by joint 232). For some applications, the joint is disposed within a proximal portion of distal tip element 107. Alternatively or additionally, the joint is disposed between distal tip portion 120 and axial shaft receiving tube 126 (e.g., as shown). FIGS. 17Bi-17Bii FIGS. 20A-20C FIGS. 17Bi-17Bii

[0314] Reference is now made to FIG. 19F , which is a schematic illustration of a ventricular assist device 20 according to some applications of the present application, including a curved element 218 configured to provide a predetermined curvature to tube 24. For some applications, ventricular assist device includes curved element 218 as an alternative or in addition to tube 24 itself being shaped to define a curvature (e.g., as described with reference to FIGS. 19A-19E Typically, the curved element is made of a shape memory material, such as a shape memory alloy, such as nitinol. For some applications, the curved element is formed of a nitinol tube that is cut to define a hole or slit, enabling the tube to be pre-shaped to a desired curved shape. For example, the nitinol element can be a nitinol "hypo tube" known in the art (i.e., a nitinol tube having micro-engineered features along its length). Typically, curved element 218 is disposed about drive cable 130 along a longitudinal segment of the drive cable that is proximal to (e.g., directly proximal to) proximal radial support 116. For some applications, along this longitudinal segment of the drive cable, the curved element is used in place of outer tube 142.

[0315] For some applications, the curved element is shaped to have a curvature that is substantially similar to the curvature described with reference to FIGS. 19A-19E with respect to tube 24. For some applications, the curvature is such that an angle omega between a longitudinal axis of the curved element at a proximal end of the curved element and a longitudinal axis of the curved element at a distal end of the curved element is greater than 90 degrees (e.g., greater than 120 degrees, or greater than 140 degrees), and / or less than 180 degrees (e.g., less than 160 degrees, or less than 150 degrees), e.g., 90-180 degrees, 90-160 degrees, 120-160 degrees, or 140-150 degrees. For some applications, the curvature of the tube is such that a radius of curvature defined by a surface of the curved element inside the curvature is greater than 10 mm, e.g., greater than 20 mm, and / or less than 200 mm (e.g., 100 mm), e.g., 10-200 mm, or 20-100 mm. As described with reference to FIGS. 19A-19C ​​​As noted, typically, the curvature of the tube is such that a space between the blood inlet 108 and the posterior wall 336 of the left ventricle, the mitral valve leaflets 402, and / or the subvalvular portion of the mitral valve (e.g., chordae 404, papillary muscle, and / or papillary muscle 341) is maintained, as shown. Typically, the curvature is such that, when the proximal end of the tube is disposed within the aorta, at least a portion of the tube is disposed within the left ventricle and curves away from the posterior wall of the left ventricle, toward the apex of the left ventricle, and / or toward the free wall. Further, more typically, the curvature is such that, when the proximal end of the tube is disposed within the aorta, at least a portion of the tube is disposed within the left ventricle and curves away from the septal wall of the left ventricle, toward the apex of the left ventricle, and / or toward the free wall. FIG. 19C As noted, typically, the curvature of the tube is such that a space between the blood inlet 108 and the posterior wall 336 of the left ventricle, the mitral valve leaflets 402, and / or the subvalvular portion of the mitral valve (e.g., chordae 404, papillary muscle, and / or papillary muscle 341) is maintained, as shown. Typically, the curvature is such that, when the proximal end of the tube is disposed within the aorta, at least a portion of the tube is disposed within the left ventricle and curves away from the posterior wall of the left ventricle, toward the apex of the left ventricle, and / or toward the free wall. Further, more typically, the curvature is such that, when the proximal end of the tube is disposed within the aorta, at least a portion of the tube is disposed within the left ventricle and curves away from the septal wall of the left ventricle, toward the apex of the left ventricle, and / or toward the free wall.

[0316] For some applications, when the ventricular assist device is deployed within the left ventricle, the distal tip portion is first deployed. As noted above, the distal tip portion is typically deployed in a given orientation relative to the left ventricle anatomy. Typically, after the distal tip portion is deployed, the curved element 218 is deployed. In some cases, the distal tip portion has been deployed in the desired orientation relative to the left ventricle anatomy, and the curved element 218 is not disposed within the left ventricle in the desired orientation. Thus, for some applications, the distal portion is coupled (directly or indirectly) to the curved element 218 via a joint 212 that allows the pump outlet tube to rotate relative to the distal tip portion of the ventricular assist device, as shown by arrow 210 in FIGS. 19A-19E For example, the joint can be a rotational joint and / or a ball and socket joint (e.g., ball and socket joint 230 as shown in FIGS. 17Bi-17Bii For example, the joint can be a rotational joint and / or a ball and socket joint (e.g., ball and socket joint 230 as shown in FIGS. 20A-20C For example, the joint can be a rotational joint and / or a ball and socket joint (e.g., ball and socket joint 230 as shown in FIGS. 17Bi-17Bii For example, the joint can be a rotational joint and / or a ball and socket joint (e.g., ball and socket joint 230 as shown in

[0317] Referring to FIGS. 19A-19F , note that, for some applications, due to the outer tube 142 anchoring to the aorta and the distal tip portion 120 becoming anchored to the inner wall of the left ventricle (e.g., the free wall near the apex), the tube 24 adopts a curved shape, as noted above. Note also that FIGS. 16A-16B , the curvature of the tube is less than the curvature of the tube shown in FIGS. 19A-19F , because FIGS. 16A-16B Different views of the device are shown. In the view shown in FIGS. 16A-16B , the curvature is typically less apparent than in the view shown in FIGS. 19A-19F .

[0318] Referring now to FIGS. 20A-20C, which are schematic illustrations of ventricular assist devices 20 according to some applications of the present application, the axial shaft 92 of the device includes a joint 232 (e.g., a universal joint as shown). As shown, the joint is typically disposed within a portion of the axial shaft that is configured to be disposed between the proximal hub 64 and the distal hub 58 of the impeller. Note that in FIG. 20A , portions of the impeller (e.g., the membrane 56 and the spring 54 of the material) are not shown for illustration purposes, and in order to provide visibility of this portion of the axial shaft, which is typically disposed between the proximal hub 64 and the distal hub 58 of the impeller, within the cavity 62 defined by the impeller (e.g., the cavity 62 is shown in FIGS. 3A-3C . Alternatively, the joint is disposed along the axial shaft at a different location, e.g., proximal to the impeller or distal to the impeller.

[0319] For some applications, the joint 232 is disposed between a proximal portion 234 of the axial shaft and a distal portion 236 of the axial shaft, the proximal portion 234 and the distal portion 236 being coupled to one another by the joint such that the proximal portion and the distal portion can be bent relative to one another by the joint. Typically, the joint allows the axial shaft to adopt a shape that is consistent with the curvature of other portions of the left ventricular device and / or the anatomy of the subject. For some applications, the joint is configured to allow the axial shaft to conform to the curvature of the frame 34 such that even if the frame 34 becomes slightly curved, the proximal portion of the axial shaft is disposed coaxially relative to the proximal bearing 116 and the distal portion of the axial shaft is disposed coaxially relative to the distal bearing 118.

[0320] FIG. 21 , which are schematic illustrations of ventricular assist devices including one or more blood pressure measurement tubes 222 according to some applications of the present application. As described above, typically, the ventricular assist device includes a pump outlet tube 24 that passes through the aortic valve of the subject such that the proximal end of the tube is disposed within the aorta of the subject and the distal end of the tube is disposed within the left ventricle of the subject. Typically, a blood pump (which typically includes an impeller 50) is disposed within the tube 24, within the left ventricle of the subject, and is configured to pump blood from the left ventricle into the aorta of the subject through the tube 24. For some applications, a ventricular blood pressure measurement tube 222 is configured to extend to at least the outer surface 213 of the tube 24 such that an opening 214 at the distal end of the blood pressure measurement tube is in direct fluid communication with the patient’s blood flow outside of the tube 24. Typically, the opening 214 is configured to be within the left ventricle of the subject, proximal to the blood pump (e.g., proximal to the impeller 50). A pressure sensor 216 (in FIG. 1AThe pressure sensor measures blood pressure within the ventricular blood pressure measurement tube. Typically, the pressure sensor measures blood pressure within the left ventricular blood pressure measurement tube, thereby measuring the subject's blood pressure outside the tube 24 (i.e., left ventricular blood pressure). Typically, the blood pressure measurement tube 222 extends from outside the subject's body to the opening 214 at the distal end of the tube, and the pressure sensor 216 is disposed toward the proximal end of the tube, e.g., outside the subject's body. For some applications, the computer processor 25 FIG. 1A receives an indication of the measured blood pressure, and controls blood pumping by the impeller in response to the measured blood pressure.

[0321] For some applications, the ventricular assist device includes two or more such ventricular blood pressure measurement tubes 222, e.g., as shown in FIG. 21 the ventricular blood pressure measurement tubes 222 shown in FIG. 2. For some applications, the computer processor 25 determines whether the opening of one of the two or more ventricular blood pressure measurement tubes is occluded based on blood pressure measured within each left ventricular blood pressure measurement tube. This can occur, for example, due to the opening contacting the septal wall and / or a different intraventricular portion within the heart chamber. Typically, in response to a determination that the opening of one of the two or more ventricular blood pressure measurement tubes is occluded, the computer processor determines the left ventricular pressure of the subject based on blood pressure measured within another of the two or more ventricular blood pressure measurement tubes.

[0322] For some applications, the outer tube 142 defines a recess 215 in a portion of the outer surface of the tube configured to be disposed within the tube 24. Typically, during insertion of the ventricular assist device into the subject's body, the portion of the ventricular blood pressure measurement tube 222 extending from within the tube 24 to at least the outer surface of the tube 24 is configured to be disposed within the recess, such that the portion of the ventricular blood pressure measurement tube does not protrude from the outer surface of the outer tube.

[0323] For some applications (not shown), a distal portion of the blood pressure measurement tube 222 is disposed outside the pump outlet tube 24. For example, the blood pressure measurement tube 222 can extend from the outer tube 142 to the proximal end of the pump outlet tube 24, after which the blood pressure measurement tube can be built into the outer surface of the tube pump outlet tube 24, e.g., as shown in FIG. 16D of US 10,881,770 to Tuval, which is incorporated by reference herein.

[0324] As described above, for some applications, the drive cable 130 extends from a motor outside 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 outer tube 140 and the second outer tube 142, as described above. For some applications, a proximal portion of the blood pressure measurement tube 222 includes a passage between the first outer tube 140 and the second outer tube 142, e.g., as shown in FIG. 21of the cross-section. In this regard, it should be noted that blood pressure measurement tube is understood to refer to the continuous lumen within the subject's left ventricle, extending from pressure sensor 216 to outside of pump outlet tube 24, regardless of whether there are structural changes to the lumen along the length of the lumen. As noted above, cleaning fluid is also typically pumped between outer tube 140 and outer tube 142, and for some applications, through passageway 226. Typically, blood pressure measurement tube 222 occupies more of the cross-sectional area defined between outer tube 140 and outer tube 142 than does cleaning fluid passageway 226, as shown in FIG. 21 For example, the ratio of (a) the cross-sectional area defined between outer tube 140 and outer tube 142 that is occupied by blood pressure measurement tube to (b) the cross-sectional area defined between outer tube 140 and outer tube 142 that is occupied by cleaning fluid passageway 226 is typically greater than 3:2, greater than 3: 1, or greater than 5: 1. For some applications, blood pressure measurement tube occupies a relatively large proportion of the cross-sectional area defined between outer tube 140 and outer tube 142 in order to proximally transmit blood pressure outside of pump outlet tube 24 within the subject's left ventricle to pressure sensor 216.

[0325] Reference is now made to FIG. 22A and FIG. 22B which are schematic illustrations of a sterile sleeve 242 according to some applications of the present application, configured to form a seal between delivery catheter 143 and outer tube 142 of ventricular assist device 20. For some applications (not shown), delivery catheter 143 is inserted into an artery (e.g., femoral artery or radial artery) of a subject via an introducer sheath (not shown) that is inserted into an incision in the artery and typically remains in place within the artery throughout the entire operation of the ventricular assist device. For such applications, a sterile sleeve (generally similar to the sleeve shown in FIGS. 22A-22B is typically disposed between delivery catheter 143 and the introducer sheath (not shown) in order to allow for movement between the delivery catheter and the introducer sheath while maintaining sterility of the arterial incision.

[0326] For some alternative applications, the ventricular assist device is initially inserted through the arteriotomy with an introducer sheath, which is subsequently removed for the remainder of the operation of the ventricular assist device. For example, the ventricular assist device can be inserted through a peel-away introducer sheath. Subsequently, the delivery catheter is typically in direct contact with the arteriotomy. This typically reduces the diameter of the device that is disposed within the arteriotomy for the remainder of the procedure relative to the case where the introducer sheath remains within the arteriotomy for the entire operation of the ventricular assist device. For example, the outer diameter of the delivery catheter can be less than 3.3 mm (i.e., 10 French), and this is the diameter through the arteriotomy once the introducer sheath is removed. The inner diameter of the delivery catheter is typically less than 3 mm (i.e., 9 French), for example, the inner diameter can be 2.7 mm (i.e., 8 French). In contrast, if the introducer sheath remains in place for the entire operation of the ventricular assist device, this would increase the diameter through the arteriotomy because the thickness of the wall of the introducer sheath must additionally be accommodated by the arteriotomy. For example, it can increase the diameter by 0.3-0.6 mm (i.e., approximately 1-2 French).

[0327] For some such applications, the delivery catheter is advanced forward until the distal end of the delivery catheter is disposed at a given location within the subject's aorta (e.g., within the ascending aorta). Subsequently, the pump portion 27 of the ventricular assist device is advanced relative to the distal end of the delivery catheter by advancing the outer tube 142 relative to the delivery catheter. For such applications, the sterile sleeve 242 forms a seal between the delivery catheter 143 and the outer tube 142 of the ventricular assist device 20, for example, allowing the outer tube to move relative to the delivery catheter while maintaining the sterility of the arteriotomy. For some such applications, the ventricular assist device is provided to the user in a kit that includes the sterile sleeve 242 disposed in place between the outer tube 142 and the delivery catheter 143.

[0328] Reference is now made to FIGS. 23A-23C which is a schematic illustration of an end straightening element 270 according to some applications of the present application for straightening the distal end portion 120 of the ventricular assist device 20 during insertion of the guide wire 10 through the distal end portion 120 of the ventricular assist device 20. As described above, typically, the ventricular assist device is inserted into the subject's ventricle through the guide wire 10, which is disposed within the delivery catheter 143 (e.g., as described above with respect to FIG. 1). The distal end portion 120 of the ventricular assist device is typically disposed within the delivery catheter 143, and the guide wire 10 is disposed within the ventricular assist device 20. The guide wire 10 is typically advanced through the distal end portion 120 of the ventricular assist device 20, and the distal end portion 120 of the ventricular assist device 20 is typically straightened by the guide wire 10. Subsequently, the guide wire 10 is removed from the ventricular assist device 20, and the ventricular assist device 20 is advanced through the delivery catheter 143 and into the subject's ventricle. FIG. 1B(Illustrated schematically) Typically, the guide wire is first inserted into the ventricular assist device at the distal end of the distal terminal element 107. For some applications, to facilitate the insertion of the guide wire through the distal end of the distal terminal element (i.e., through the distal terminal portion 120), a terminal straightening element 270 is positioned around the distal terminal element, for example, to hold the distal terminal element in a straightened configuration. Typically, the straightening element is a housing defining a flat cavity 271. The straightening element is positioned around the distal terminal element such that the distal terminal element is configured in a straightened configuration within the cavity 271, and the guide wire is inserted into the distal end of the distal terminal element (i.e., through the distal portion 120), for example, as... FIG. 23B As shown. For some applications, the straightening element is configured to be removable from the distal end element, while the guide wire is disposed in the distal end element. For example, the straightening element may be notched, perforated, and / or have a slit 272 (as shown) extending along its length to facilitate removal of the straightening element from the distal end element, for example, as... FIG. 23C As shown.

[0329] Now for reference FIG. 24A , FIG. 24B and FIG. 24C These are graphs illustrating measurements performed during the use of a left ventricular assist device according to some applications of the invention. The left ventricular assist device described herein is deployed within the heart of a pig. The pig's arterial pulsation is measured using an intra-aortic pressure sensor while the left ventricular assist device operates at a corresponding rotational rate. The device is calibrated based on in vitro tests performed on it to determine the flow rate produced when the impeller rotates at the corresponding rate. FIG. 24A The graph shows the arterial pulsation versus flow rate generated by the device, measured in experiments conducted on pigs (using a predetermined correspondence between impeller rotation rate and flow rate). Then... FIG. 24A The points shown in the figure are fitted to a curve, and this curve is extrapolated to the y-intercept (i.e., when the arterial pulsation is zero), as shown. FIG. 24B As shown in the figure, by extrapolating the curve, the flow rate at zero arterial pulsation was estimated to be 5.6 L / min. In the same pig, cardiac output was measured using a Swan-Ganz catheter when the left ventricular assist device was inactive. The Swan-Ganz catheter measured the pig's natural cardiac output at 5.2 L / min, which is similar to the flow rate estimated by extrapolating the flow rate / arterial pulsation curve at zero arterial pulsation. It is assumed that at zero arterial pulsation, the left ventricular assist device largely replaces the heart's inherent function, and that at this value, the flow rate produced by the pump provides a reasonable approximation of the subject's natural cardiac output.

[0330] Based on the above experimental results, for some applications of the present application, the subject's arterial pulse is measured during operation of the ventricular assist device, and a parameter is derived from the subject's arterial pulse. Typically, as the rotational rate of the impeller is increased, the flow generated by the blood pump is increased. Typically, the flow generated by the blood pump is non-pulsatile, as the blood pump is a continuous flow blood pump rather than a pulsatile blood pump. Thus, typically, as the rotational rate of the impeller is increased and the flow generated by the blood pump is increased, the subject's arterial pulse is decreased. In some applications, the subject's arterial pulse is measured as a function of the rotational rate of the impeller. Based on the above measurements, a relationship between the arterial pulse and the rotational rate of the impeller and / or the pump flow is derived. In some applications, based on the above relationship, the subject's natural cardiac output can be derived. For some such applications, when the subject's arterial pulse reaches zero, the relationship between the subject's arterial pulse and the pump flow is extrapolated to determine what the pump flow would be. Based on the above results, it is assumed that at this value, the pump is replacing the inherent function of the heart, and the flow generated by the pump at this value provides an approximation of the subject's natural cardiac output.

[0331] With reference to FIGS. 1A-24C It should be noted that all aspects of the ventricular assist device 20 described are applicable to a variety of blood pumps. For example, aspects of the present application can be applicable to a pump used to pump blood from the vena cava and / or right atrium into the right ventricle, from the vena cava and / or right atrium into the pulmonary artery, and / or from the renal vein into the vena cava. These aspects can include features of the tube 24 (e.g., the curvature of the tube), the impeller 50, features of the pump portion 27, the drive cable 130, etc. Alternatively or additionally, the device 20 and / or a portion thereof (e.g., the impeller 50, even without the tube 24) is placed within a different portion of the subject's body to assist in pumping blood from that portion. For example, the device 20 and / or a portion thereof (e.g., the impeller 50, even without the tube 24) can be placed in a blood vessel and can be used to pump blood through the blood vessel. For some applications, the device 20 and / or a portion thereof (e.g., the impeller 50, even without the tube 24) is configured (with necessary modifications) for placement within the subclavian vein or jugular vein, at the junction of the vein with the lymphatic duct, and for increasing the flow of lymph fluid from the lymphatic duct into the vein. As the scope of the present application includes the use of the apparatus and methods described herein in anatomical locations other than the left ventricle and aorta, the ventricular assist device and / or portions thereof are sometimes referred to herein (in the specification and claims) as a blood pump. FIG. 1A and FIG. 1B The ventricular assist device 20 is shown in the subject's left ventricle, but for some applications the device 20 is placed within the subject's right ventricle, such that the device (with necessary modifications) passes through the subject's pulmonary valve, and the techniques described herein are applied. For some applications, components of the device 20 are adapted for use with different types of blood pumps. For example, aspects of the present application can be applicable to a pump used to pump blood from the vena cava and / or right atrium into the right ventricle, from the vena cava and / or right atrium into the pulmonary artery, and / or from the renal vein into the vena cava. These aspects can include features of the tube 24 (e.g., the curvature of the tube), the impeller 50, features of the pump portion 27, the drive cable 130, etc. Alternatively or additionally, the device 20 and / or a portion thereof (e.g., the impeller 50, even without the tube 24) is placed within a different portion of the subject's body to assist in pumping blood from that portion. For example, the device 20 and / or a portion thereof (e.g., the impeller 50, even without the tube 24) can be placed in a blood vessel and can be used to pump blood through the blood vessel. For some applications, the device 20 and / or a portion thereof (e.g., the impeller 50, even without the tube 24) is configured (with necessary modifications) for placement within the subclavian vein or jugular vein, at the junction of the vein with the lymphatic duct, and for increasing the flow of lymph fluid from the lymphatic duct into the vein. As the scope of the present application includes the use of the apparatus and methods described herein in anatomical locations other than the left ventricle and aorta, the ventricular assist device and / or portions thereof are sometimes referred to herein (in the specification and claims) as a blood pump.

[0332] The scope of the application includes the combination of any of the devices and methods described herein with any of the devices and methods described in one or more of the following applications, all of which are incorporated by reference herein:

[0333] US 2020 / 0237981 to Tuval, entitled “Distal tip element for a Ventricular assist device”, filed January 23, 2020, which claims priority to:

[0334] U.S. Provisional Patent Application 62 / 796,138 to Tuval, entitled “Ventricular assist device”, filed January 24, 2019;

[0335] U.S. Provisional Patent Application 62 / 851,716 to Tuval, entitled “Ventricular assist device”, filed May 23, 2019;

[0336] U.S. Provisional Patent Application 62 / 870,821 to Tuval, entitled “Ventricular assist device”, filed July 5, 2019; and

[0337] U.S. Provisional Patent Application 62 / 896,026 to Tuval, entitled “Ventricular assist device”, filed September 5, 2019.

[0338] US 10,881,770 to Tuval, which is a continuation of International Application No. PCT / IB2019 / 050186 (published as WO 19 / 138350) to Tuval, entitled “Ventricular assist device”, filed January 10, 2019, which claims priority to:

[0339] U.S. Provisional Patent Application 62 / 615,538 to Sohn, entitled “Ventricular assist device”, filed January 10, 2018;

[0340] U.S. Provisional Patent Application 62 / 665,718 to Sohn, entitled “Ventricular assist device”, filed May 2, 2018;

[0341] U.S. Provisional Patent Application 62 / 681,868 entitled "Ventricular assist device" to Tuval, filed June 7, 2018; and

[0342] U.S. Provisional Patent Application 62 / 727,605 entitled "Ventricular assist device" to Tuval, filed September 6, 2018;

[0343] US 2019 / 0269840 to Tuval, which is the U.S. National Stage of International Patent Application PCT / IL2017 / 051273 (published as WO 18 / 096531) entitled "Blood pumps" to Tuval, filed November 21, 2017, which claims priority to U.S. Provisional Patent Application 62 / 425,814 to Tuval, filed November 23, 2016;

[0344] US 2019 / 0175806 to Tuval, which is a continuation of International Application No. PCT / IL2017 / 051158 (published as WO 18 / 078615) entitled "Ventricular assist device" to Tuval, filed October 23, 2017, which claims priority to US 62 / 412,631 to Tuval, filed October 25, 2016, and US 62 / 543,540 to Tuval, filed August 10, 2017;

[0345] US 2019 / 0239998 to Tuval, which is the U.S. National Stage of International Patent Application PCT / IL2017 / 051092 (published as WO 18 / 061002) entitled "Blood vessel tube" to Tuval, filed September 28, 2017, which claims priority to U.S. Provisional Patent Application 62 / 401,403 to Tuval, filed September 29, 2016;

[0346] US 2018 / 0169313 to Schwammenthal, which is the U.S. National Stage of International Patent Application PCT / IL2016 / 050525 (published as WO 16 / 185473) entitled "Blood pump" to Schwammenthal, filed May 18, 2016, which claims priority to U.S. Provisional Patent Application 62 / 162,881 entitled "Blood pump" to Schwammenthal, filed May 18, 2015;

[0347] US 10,583,231 to Schwammenthal, which is the US national stage of International Patent Application PCT / IL2015 / 050532 (published as WO 15 / 177793) to Schwammenthal, filed May 19, 2015, entitled "Blood pump," which claims priority to U.S. Provisional Patent Application 62 / 000,192 to Schwammenthal, filed May 19, 2014, entitled "Blood pump";

[0348] US Patent 10,039,874 to Schwammenthal, which is the US national stage of International Patent Application PCT / IL2014 / 050289 (published as WO 14 / 141284) to Schwammenthal, filed March 13, 2014, entitled "Renal pump," which claims priority to (a) U.S. Provisional Patent Application 61 / 779,803 to Schwammenthal, filed March 13, 2013, entitled "Renal pump," and (b) U.S. Provisional Patent Application 61 / 914,475 to Schwammenthal, filed December 11, 2013, entitled "Renal pump";

[0349] U.S. Patent 9,764,113 to Tuval, entitled "Curved catheter," issued September 19, 2017, which claims priority to U.S. Provisional Patent Application 61 / 914,470 to Tuval, filed December 11, 2013, entitled "Curved catheter"; and

[0350] US 9,597,205 to Tuval, which is the US national stage of International Patent Application PCT / IL2013 / 050495 (published as WO 13 / 183060) to Tuval, filed June 6, 2013, entitled "Prosthetic renal valve," which claims priority to U.S. Provisional Patent Application 61 / 656,244 to Tuval, filed June 6, 2012, entitled "Prosthetic renal valve."

[0351] Those skilled in the art will realize that the application is not limited to the specifics set forth in the foregoing description and in the drawings. Rather, the scope of the application includes both combinations and sub-combinations of the various features described hereinbefore as well as modifications and variations of the application that will occur to those skilled in the art upon reading the foregoing description.

Claims

1. An apparatus comprising: a blood pump configured to be placed inside a body of a subject, the blood pump comprising: - an impeller comprising: -- a proximal hub and a distal hub; -- two or more helical elongated elements extending from the proximal hub to the distal hub; -- an axial structure disposed inside the two or more helical elongated elements and disposed along an axis around which the helical elongated elements are wound; and -- a membrane of a material supported between the helical elongated elements and the axial structure, such that each of the helical elongated elements with the membrane of the material coupled thereto defines a respective blade of the impeller; and - an impeller overexpansion prevention element, the impeller overexpansion prevention element being a single integrated structure comprising a ring disposed around the axial structure, each of the elongated elements extending from the ring to a respective helical elongated element and being coupled to the respective helical elongated element to prevent radial expansion of the impeller.

2. The apparatus of claim 1, wherein, the impeller comprises three helical elongated elements, such that the three helical elongated elements with the membrane of the material coupled thereto define three blades of the impeller, and wherein a respective elongated element extends from the ring to each of the three helical elongated elements, such that there is a respective elongated element within each of the three blades of the impeller.

3. The apparatus of claim 1, wherein, the elongated elements are configured to substantially not resist compression, and the elongated elements are configured to prevent radial expansion of the impeller by applying tension to the helical elongated elements.

4. The apparatus of claim 1, wherein, along at least a portion of a length of the impeller, as the membrane of the material transitions from one impeller blade to an adjacent blade, the membrane of the material forms a continuous U-shaped curve, wherein the U-shaped curvature of the membrane of the material is substantially uninterrupted at the axial structure.

5. The apparatus of any one of claims 1-4, wherein, a pressure side of each of the blades of the impeller is convex in a distal region of the impeller and concave in a proximal region of the impeller when viewed from a distal end of the impeller, the pressure side being configured to push blood during operation of the impeller.

6. The apparatus of claim 5, wherein, the pressure side of each of the blades of the impeller is substantially radially oriented in a region of the elongated element within the impeller blade.

7. The apparatus of any one of claims 1-4, wherein, the helical elongated elements are coated with a coupling agent configured to enhance bonding between the helical elongated elements and the membrane of the material.

8. The apparatus of claim 7, wherein, the membrane of the material comprises an elastomeric material, and wherein the coupling agent comprises at least two functional groups configured to bond with the helical elongated elements and the elastomeric material, respectively.

9. The apparatus of claim 8, wherein, the coupling agent comprises a silane compound.

10. The apparatus of claim 7, further comprising a layer of an elastomer disposed between the membrane of the material and the coupling agent.

11. The apparatus of claim 10, wherein, the layer of the elastomer is configured to round the helical elongated elements.

12. The apparatus of claim 10, wherein, the membrane of the material is made of the elastomer.

13. The apparatus of claim 12, wherein, The elastomer comprises a polycarbonate-based thermoplastic polyurethane.

14. The apparatus of any one of claims 1-4, wherein, The axial structure comprises a spring.

15. The apparatus of claim 14, wherein, The spring comprises a tube at an intermediate position along a length of the spring, and wherein the ring is disposed around the tube.

16. The apparatus of any one of claims 1-4, 6, 8-13, and 15, further comprising: a blood pressure sensor configured to measure a subject's aortic pressure; a computer processor configured to: derive an arterial pulse of the subject from the measured aortic pressure; and estimate a native cardiac output of the subject based at least in part on the arterial pulse.

Images