Ventricular Assist Devices

Abstract

To provide a ventricular assist device.SOLUTION: A blood pump inside the body of a subject comprises an impeller (50) comprising proximal and distal bushings (64, 58) and a frame (34) disposed around the impeller and comprising proximal and distal bearings (116, 118). An axial shaft (92) passes through the proximal and distal bearings (116, 118) of the frame and the proximal and distal bushings (64, 58) of the impeller (50). The impeller (50) defines a radially-constrained configuration and a non-radially-constrained configuration. In the radially-constrained configuration, the impeller (50) is introduced into the subject's body. In the non-radially-constrained configuration, the impeller (50) pumps blood within the subject's body. The impeller (50) changes from its radially-constrained configuration to its non-radially-constrained configuration by the distal bushing (58) sliding over the axial shaft (92).SELECTED DRAWING: Figure 5A

Description

[Technical field]

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS This application claims priority from: U.S. Provisional Patent Application No. 62 / 615,538 by Sohn, entitled “Ventricular assist device,” filed on January 10, 2018; U.S. Provisional Patent Application No. 62 / 665,718 by Sohn, entitled “Ventricular assist device,” filed May 2, 2018; No. 62 / 681,868 by Tuval, entitled "Ventricular assist device," filed June 7, 2018; and U.S. Provisional Patent Application No. 62 / 727,605 by Tuval, entitled “Ventricular assist device,” filed September 6, 2018.

[0002] All of the above referenced applications are incorporated herein by reference. Some applications of the present invention relate generally to medical devices and, more particularly, to ventricular assist devices and methods of use thereof. [Background technology]

[0003] Ventricular assist devices are mechanical circulatory support devices designed to assist and unload the heart chambers to maintain or increase cardiac output. They are used in patients suffering from heart failure and in patients at risk of deterioration of cardiac function during percutaneous coronary intervention. Most commonly, left ventricular assist devices are applied to failing hearts to assist left ventricular function. In some cases, right ventricular assist devices are used to assist right ventricular function. Such assist devices are either designed to be permanently implanted or to be worn over a catheter for temporary placement. Summary of the Invention [Means for solving the problem]

[0004] According to some applications of the present invention, the ventricular assist device includes an impeller disposed on an axial shaft with a frame disposed around the impeller. The ventricular assist device typically includes a tube that traverses the subject's aortic valve, such that a proximal end of the tube is disposed in the subject's aorta and a distal end of the tube is disposed in the subject's left ventricle. The impeller, the axial shaft, and the frame are disposed in a distal portion of the tube inside the subject's left ventricle. Typically, the impeller is configured to pump blood from the left ventricle into the aorta by rotating. The tube typically defines one or more blood inlet openings at a 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 through which blood flows from the tube into the ascending aorta during operation of the impeller.

[0005] For some applications, the impeller includes a proximal bushing and a distal bushing, and the frame includes a proximal bearing and a distal bearing. The axial shaft typically passes through the proximal and distal bearings of the frame and the proximal and distal bushings of the impeller. For some applications, (a) the proximal bushing of the impeller (a) the impeller is coupled to the axial shaft such that the proximal bushing is held in an axially fixed position relative to the axial shaft, and (b) the impeller's distal bushing is not coupled to the axial shaft such that the distal bushing is not held in an axially fixed position relative to the axial shaft. Typically, the impeller defines a radially constrained configuration and a radially unconstrained configuration, in which the impeller is introduced into a subject's body and in which the impeller is configured to pump blood into the subject's body. For some applications, the impeller changes from its radially constrained configuration to its radially unconstrained configuration by the distal bushing sliding over the axial shaft.

[0006] Typically, the axial shaft is not held in an axially fixed position relative to the proximal and distal bearings. More typically, the ventricular assist device (and / or blood pump portion thereof) does not include any thrust bearings configured to be disposed within the subject's body. For some applications, the ventricular assist device includes one or more thrust bearings disposed outside the subject's body, and opposition to thrust generated by rotation of the impeller is provided solely by the one or more thrust bearings disposed outside the subject's body.

[0007] For some applications, the motor drives the impeller to pump blood from the left ventricle to the aorta by rotating the impeller, the impeller configured to undergo axial motion relative to the frame in response to a changing pressure differential between the left ventricle and the aorta. For some applications, the computer processor measures an indication of the axial motion of the impeller. For some applications, the computer processor derives the subject's cardiac cycle, the pressure differential between the left ventricle and the aorta, and / or the subject's left ventricular pressure based on the measured indication of the axial motion of the impeller. For some applications, the computer processor varies a rotational speed of the impeller based at least in part on the sensor signal. For example, the computer processor can determine the subject's left ventricular pressure based at least in part on the sensor signal and vary a rotational speed of the impeller based at least in part on the determined left ventricular pressure. For some applications, the computer processor reduces the rotational speed of the impeller in response to determining that the subject's left ventricular pressure has decreased. For some applications, the impeller is coupled to a magnet such that axial movement of the impeller causes the magnet to experience axial movement, and the computer processor measures an indication of the axial movement of the impeller by measuring magnetic flux generated by the magnet.

[0008] Typically, the drive cable extends from outside the subject's body to the axial shaft and is configured to rotate to impart rotational motion from the motor to the impeller, which rotates in a given direction to pump blood from the left ventricle to the aorta. For some applications, at least a portion of the drive cable includes a plurality of wires arranged in a coiled configuration such that in response to the drive cable rotating in a given direction of rotation, the plurality of wires arranged in the coiled configuration at least partially unwind and a portion of the drive cable shortens in the axial direction. For some applications, an outer tube is disposed around the drive cable, and frictional forces between the outer tube and the drive cable typically generate debris. Alternatively or additionally, a fluid (e.g., a purging fluid) is disposed between the outer tube and the drive cable. For some such applications, the coiled configuration is configured to at least partially unwind and ... At least a portion of the drive cable is configured such that the plurality of wires are configured to pump debris and / or fluid toward a proximal end of the drive cable.

[0009] For some applications, the drive cable includes a first portion configured to be disposed at least partially in the subject's aortic arch and a second portion configured to be disposed at least partially in the subject's descending aorta, the flexibility of the first portion being greater than the flexibility of the second portion. For example, the first portion of the drive cable can include a first number of wires arranged in a coiled configuration and the second portion of the drive cable can include a second number of wires arranged in a coiled configuration, the first number being less than the second number. For example, the first portion of the drive cable can include between 4 and 8 wires arranged in a coiled configuration and the second portion of the drive cable can include between 8 and 12 wires arranged in a coiled configuration.

[0010] For some applications, the impeller includes at least one helical elongate element (and typically three helical elongate elements) and a spring, the spring being disposed inside the helical elongate element along the axis about which the helical elongate element winds. Typically, a film of material (e.g., silicone) is supported between the helical elongate element and the spring. For some applications, at least one elongate element (e.g., a string or wire) extends from the spring to the helical elongate element and is configured to maintain the helical elongate element within a given distance from the spring.

[0011] As described above, for some applications, the frame is disposed around the impeller. For some applications, the ventricular assist device includes a stator including a plurality of curved projections coupled to a proximal end of the frame. Typically, the curvature of the curved projections opposes a direction of rotation of the impeller. For some applications, the curvature of the curved projections is such that from a distal end of the curved projections to a proximal end of the curved projections, the curved projections are progressively closer to being parallel to a longitudinal axis of the frame. Typically, the curved projections include a plurality of curved struts integral with the frame and a flexible material (e.g., silicone) extending from the curved struts. For some applications, the flexible material is shaped to define a lumen therethrough.

[0012] As described above, typically the impeller is disposed in a tube (which may be referred to herein as a "blood pressure pump tube") extending from the subject's left ventricle into the subject's aorta. For some applications, at least one blood pressure measurement tube (which defines an opening at its distal end) extends at least to an outer surface of the blood pressure pump tube, such that the opening at the distal end of the blood pressure measurement tube is in direct fluid communication with the subject's blood flow outside the blood pressure pump tube. The pressure sensor measures the pressure of the blood in the blood pressure measurement tube. For some applications, the blood pressure measurement tube is configured to pass along the outer surface of the blood pressure pump tube from the proximal end of the blood pressure pump tube to the opening at the distal end of the blood pressure measurement tube. Typically, the blood pressure measurement tube is a left ventricular blood pressure measurement tube configured to extend to an outer surface of the blood pressure pump tube at a location along the blood pressure pump tube configured to be within the subject's left ventricle proximal to the impeller, and the pressure sensor is configured to measure the subject's left ventricular pressure by measuring the pressure of blood in the left ventricular blood pressure measurement tube.

[0013] Typically, the blood pressure pump tubing defines one or more blood inlet openings in a distal portion of the blood pressure pump tubing and one or more blood outlet openings in a proximal portion of the blood pressure pump tubing. For some applications, the ventricular assist device includes a radially expandable atraumatic distal tip portion configured to be disposed in a left ventricle of a subject distal to the one or more blood inlet openings. The distal tip portion is typically configured to be inserted into the left ventricle in a radially constrained configuration and configured to assume a radially unconstrained configuration within the left ventricle of the subject, where in the radially unconstrained configuration, at least a radially expandable portion of the distal tip portion is radially expanded relative to the radially constrained configuration of the distal tip portion. Typically, in its radially unconstrained configuration, the radially expandable portion of the distal tip portion separates the one or more blood inlet openings from an interior structure of the left ventricle, such as the interventricular septum, tendon tendons, papillary muscles, and / or the apex of the left ventricle. More typically, in its radially unconstrained configuration, the radially expandable portion of the distal tip portion separates the one or more blood inlet openings in three dimensions from an interior structure of the left ventricle. For some applications, in its radially unconstrained configuration, the radially expandable portion of the distal tip portion directs blood flow from the left ventricle into the one or more blood inlet openings.

[0014] For some applications, in the radially constrained configuration of the distal tip portion, a distal region of the distal tip portion is configured to be at least semi-rigid and configured to radially converge along a longitudinal direction toward a distal end of the distal tip portion. Typically, the ventricular assist device is configured to be inserted into a subject's body through a puncture in the subject's body. For some applications, during insertion of the ventricular assist device, the distal region of the distal tip portion is configured to act as a dilator by dilating the puncture.

[0015] Generally, in the specification of this application and in the claims, the term "proximal" and related terms, when used in connection with a device or portion thereof, should be interpreted to mean the end of the device or portion thereof that is closer to the location through which the device is inserted into the subject's body when inserted into the subject's body. The term "distal" and related terms, when used in connection with a device or portion thereof, should be interpreted to mean the end of the device or portion thereof that is farther from the location through which the device is inserted into the subject's body when inserted into the subject's body.

[0016] The scope of the present invention includes the use of the apparatus and methods described herein in anatomical locations other than the left ventricle and aorta, and therefore, the ventricular assist device and / or portions thereof may be referred to herein (in the specification and claims) as a blood pump.

[0017] Thus, according to some applications of the present invention, an apparatus is provided, the apparatus comprising: a blood pump configured to be placed inside a subject's body; The blood pump is an impeller including a proximal bushing and a distal bushing; a frame configured to be disposed about the impeller, the frame including a proximal bearing and a distal bearing; an axial shaft configured to pass through proximal and distal bearings of the frame and proximal and distal bushings of the impeller; Including, a proximal bushing of the impeller coupled to the axial shaft such that the proximal bushing is held in an axially fixed position relative to the axial shaft; a distal bushing of the impeller is not coupled to the axial shaft such that the distal bushing is not held in an axially fixed position relative to the axial shaft; An apparatus is provided in which the impeller defines a radially constrained configuration and a radially unconstrained configuration, in which the impeller is configured to be introduced into a subject's body and in which the impeller is configured to pump blood into the subject's body, and in which the impeller is configured to change from its radially constrained configuration to its radially unconstrained configuration by a distal bushing sliding over the axial shaft.

[0018] For some applications, the impeller is configured to be placed inside a left ventricle of the subject and configured to pump blood from the left ventricle of the subject to an aorta of the subject. For some applications, the impeller is configured to be placed inside a right ventricle of the subject and configured to pump blood from the right ventricle of the subject to a pulmonary artery of the subject. For some applications, the impeller is configured to be placed inside a blood vessel of the subject. For some applications, the impeller is configured to be placed inside a heart chamber of the subject.

[0019] In some applications, the impeller may be at least one helical elongate element extending from the proximal bushing to the distal bushing; a spring disposed inside the helical elongated element along an axis around which the helical elongated element winds; a film of material supported between the helical elongate element and the spring; at least one flexible elongate element extending from the spring to the helical elongate element and configured to maintain the helical elongate element within a given distance from the spring, the at least one flexible elongate element being selected from the group consisting of a string and a wire; Includes.

[0020] For some applications, the apparatus further includes a delivery catheter; the delivery catheter is configured to maintain the impeller in its radially constrained configuration during introduction of the impeller into the subject's body; When the impeller is released from the delivery catheter, the impeller is configured to self-expand, thereby causing the distal bushing to slide proximally over the axial shaft, causing the impeller to assume its radially unconstrained configuration; and To retract the impeller from the subject's body, the distal end of the delivery catheter and the impeller are moved relative to one another, with the distal end of the delivery catheter being configured to cause the distal bushing to slide distally over the axial shaft, thereby causing the impeller to assume its radially constrained configuration.

[0021] According to some applications of the present invention, an apparatus is provided, the apparatus comprising: ventricular assist devices, Ventricular assist devices are an impeller configured to be placed inside the left ventricle of the subject; a frame configured to be disposed about the impeller; a motor configured to drive the impeller to rotate the impeller and thereby pump blood from the left ventricle to the aorta of the subject; Including, An apparatus is further provided, wherein the impeller is configured to undergo axial forward and backward movement relative to the frame in response to cyclic changes in pressure differential between the left ventricle and the aorta.

[0022] In some applications, The impeller includes a proximal bushing and a distal bushing. The frame includes a proximal bearing and a distal bearing. The ventricular assist device further includes an axial shaft configured to pass through proximal and distal bearings defined by the frame and through proximal and distal bushings of the impeller; the axial shaft is coupled to at least one of the proximal and distal bushings of the impeller such that the at least one bushing is held in an axially fixed position relative to the axial shaft; The axial shaft is not held in an axially fixed position relative to the proximal and distal bearings.

[0023] For some applications, the ventricular assist device does not include any thrust bearing configured to be disposed within the subject's body. In some applications, the ventricular assist device further includes one or more thrust bearings configured to be disposed outside the subject's body, and opposition to the thrust generated by rotation of the impeller is provided solely by the one or more thrust bearings disposed outside the subject's body.

[0024] In some applications, the motor is configured to drive the impeller to rotate the impeller in a given direction of rotation, thereby pumping blood from the subject's left ventricle to the subject's aorta; Ventricular assist devices are an axial shaft, the impeller being disposed on the axial shaft; a drive cable configured to extend from outside a subject's body to an axial shaft, the drive cable configured to rotate to impart rotational motion from a motor to an impeller, at least a portion of the drive cable including a plurality of wires arranged in a coiled configuration, the coiled configuration being such that in response to the drive cable rotating in a given direction of rotation, the plurality of wires arranged in the coiled configuration at least partially unwind, causing a portion of the drive cable to axially shorten; Further includes:

[0025] In some applications, the apparatus comprises: a sensor configured to detect an indication of axial movement of the impeller and to generate a sensor signal in response thereto; and a computer processor configured to receive the sensor signal and configured to generate an output in response thereto; With Further includes:

[0026] For some applications, the computer processor is configured to generate an output indicative of a cardiac cycle of the subject in response to receiving the sensor signal. For some applications, the computer processor is configured to determine a left ventricular pressure of the subject based at least in part on the sensor signal. For some applications, the computer processor is configured to vary a rotational speed of the impeller based at least in part on the sensor signal.

[0027] In some applications, the computer processor: configured to determine a left ventricular pressure of the subject based at least in part on the sensor signal; The system is configured to vary the rotational speed of the impeller based at least in part on the determined left ventricular pressure.

[0028] For some applications, the computer processor is configured to reduce the rotational speed of the impeller in response to determining that the subject's left ventricular pressure has decreased.

[0029] In some applications, the apparatus comprises: a magnet, the impeller being coupled to the magnet such that axial movement of the impeller causes the magnet to experience axial movement; a sensor configured to detect magnetic flux generated by the magnet and to generate a sensor signal in response thereto; a computer processor configured to receive the sensor signal and to generate an output in response thereto; Further includes:

[0030] For some applications, the computer processor is configured to generate an output indicative of a cardiac cycle of the subject in response to receiving the sensor signal. For some applications, the computer processor is configured to determine a left ventricular pressure of the subject based at least in part on the sensor signal. For some applications, the computer processor is configured to vary a rotational speed of the impeller based at least in part on the sensor signal.

[0031] In some applications, the computer processor: configured to determine a left ventricular pressure of the subject based at least in part on the sensor signal; The system is configured to vary the rotational speed of the impeller based at least in part on the determined left ventricular pressure.

[0032] For some applications, the computer processor is configured to reduce the rotational speed of the impeller in response to determining that the subject's left ventricular pressure has decreased.

[0033] In some applications, The impeller includes a proximal bushing and a distal bushing. The frame includes a proximal bearing and a distal bearing. The ventricular assist device further includes an axial shaft configured to pass through proximal and distal bearings of the frame and proximal and distal bushings of the impeller; The impeller is coupled to the axial shaft such that the impeller causes the axial shaft to undergo axial forward and backward movement relative to proximal and distal bearings of the frame.

[0034] For some applications, the axial shaft is configured to undergo axial forward and backward movement relative to the proximal and distal bearings of the frame to clean the interface between the axial shaft and the proximal and distal bearings of the frame. For some applications, the axial shaft is configured to undergo axial forward and backward movement relative to the proximal and distal bearings of the frame to reduce heating at the interface between the axial shaft and the proximal and distal bearings of the frame, as opposed to if the axial shaft did not undergo axial forward and backward movement relative to the proximal and distal bearings of the frame.

[0035] According to some applications of the present invention, an apparatus is provided, the apparatus comprising: Including a blood pump, The blood pump is an impeller including a proximal bushing and a distal bushing, the impeller configured to pump blood through a body of a subject; a frame configured to be disposed about the impeller, the frame including a proximal bearing and a distal bearing; an axial shaft configured to pass through proximal and distal bearings of the frame and proximal and distal bushings of the impeller; Including, the axial shaft is coupled to at least one of the proximal and distal bushings of the impeller such that the at least one bushing is held in an axially fixed position relative to the axial shaft; An apparatus is further provided in which the axial shaft is not held in an axially fixed position relative to the proximal and distal bearings.

[0036] For some applications, the blood pump does not include any thrust bearings configured to be disposed within the subject's body. For some applications, the blood pump further includes one or more thrust bearings configured to be disposed outside the subject's body, and opposition to thrust generated by rotation of the impeller is provided solely by the one or more thrust bearings disposed outside the subject's body.

[0037] In some applications, the apparatus comprises: a sensor configured to detect an indication of axial movement of the impeller and to generate a sensor signal in response thereto; and a computer processor configured to receive the sensor signal and to generate an output in response thereto; Further includes:

[0038] For some applications, the computer processor is configured to generate an output indicative of the subject's cardiac cycle in response to receiving the sensor signal. For some applications, the computer processor generates an output indicative of the subject's cardiac cycle based at least in part on the sensor signal. For some applications, the computer processor is configured to vary a rotational speed of the impeller based at least in part on the sensor signal to determine a left ventricular pressure of the subject.

[0039] In some applications, the computer processor: configured to determine a left ventricular pressure of the subject based at least in part on the sensor signal; The system is configured to vary the rotational speed of the impeller based at least in part on the determined left ventricular pressure.

[0040] For some applications, the computer processor is configured to reduce the rotational speed of the impeller in response to determining that the subject's left ventricular pressure has decreased.

[0041] In some applications, the apparatus comprises: a magnet, the impeller being coupled to the magnet such that axial movement of the impeller causes the magnet to experience axial movement; a sensor configured to detect magnetic flux generated by the magnet and to generate a sensor signal in response thereto; a computer processor configured to receive the sensor signal and to generate an output in response thereto; Further includes:

[0042] For some applications, the computer processor is configured to generate an output indicative of a cardiac cycle of the subject in response to receiving the sensor signal. For some applications, the computer processor is configured to determine a left ventricular pressure of the subject based at least in part on the sensor signal. For some applications, the computer processor is configured to vary a rotational speed of the impeller based at least in part on the sensor signal.

[0043] In some applications, the computer processor: configured to determine a left ventricular pressure of the subject based at least in part on the sensor signal; The system is configured to vary the rotational speed of the impeller based at least in part on the determined left ventricular pressure.

[0044] For some applications, the computer processor is configured to reduce the rotational speed of the impeller in response to determining that the subject's left ventricular pressure has decreased.

[0045] For some applications, the impeller is configured to pump blood from a first location in the subject's body to a second location in the subject's body, the impeller configured to undergo axial forward and backward motion relative to the frame in response to a periodic change in a pressure differential between the first location and the second location. For some applications, the impeller is configured to pump blood from a left ventricle of the subject to an aorta of the subject, the impeller configured to undergo axial forward and backward motion relative to the frame in response to a periodic change in a pressure differential between the left ventricle and the aorta. For some applications, the impeller is configured to pump blood from a right ventricle of the subject to a pulmonary artery of the subject, the impeller configured to undergo axial forward and backward motion relative to the frame in response to a periodic change in a pressure differential between the right ventricle and the pulmonary artery. In some applications, the impeller is configured to pump blood from a right atrium of the subject to a right ventricle of the subject, the impeller being configured to undergo axial forward and backward motion relative to the frame in response to a periodic change in a pressure differential between the right atrium and the right ventricle. In some applications, the impeller is configured to pump blood from a vena cava of the subject to a right ventricle of the subject, the impeller being configured to undergo axial forward and backward motion relative to the frame in response to a periodic change in a pressure differential between the vena cava and the right ventricle. In some applications, the impeller is configured to pump blood from a right atrium of the subject to a pulmonary artery of the subject, the impeller being configured to undergo axial forward and backward motion relative to the frame in response to a periodic change in a pressure differential between the right atrium and the pulmonary artery. In some applications, the impeller is configured to pump blood from the subject's vena cava to the subject's pulmonary artery, and the impeller is configured to undergo axial forward and backward movement relative to the frame in response to periodic changes in pressure differential between the vena cava and the pulmonary artery.

[0046] In some applications, the apparatus comprises: a motor configured to drive the impeller to rotate the impeller in a given direction of rotation, thereby pumping blood through the subject's body; a drive cable configured to extend from outside a subject's body to an axial shaft, the drive cable configured to rotate to impart rotational motion from a motor to an impeller, at least a portion of the drive cable including a plurality of wires arranged in a coiled configuration, the coiled configuration being such that in response to the drive cable rotating in a given direction of rotation, the plurality of wires arranged in the coiled configuration at least partially unwind, causing a portion of the drive cable to axially shorten; Further includes:

[0047] For some applications, the impeller is coupled to the axial shaft such that the impeller causes the axial shaft to experience axial forward and backward movement relative to the proximal and distal bearings of the frame. For some applications, the axial shaft is configured to clean an interface between the axial shaft and the proximal and distal bearings of the frame by experiencing axial forward and backward movement relative to the proximal and distal bearings of the frame. For some applications, the axial shaft is configured to reduce heat generation at an interface between the axial shaft and the proximal and distal bearings of the frame by experiencing axial forward and backward movement relative to the proximal and distal bearings of the frame, as opposed to if the axial shaft did not experience axial forward and backward movement relative to the proximal and distal bearings of the frame.

[0048] According to some applications of the present invention, an apparatus is provided, the apparatus comprising: Including a blood pump, The blood pump is an impeller configured to be placed inside a body of a subject and configured to pump blood through the body of the subject; a frame configured to be disposed around the impeller; and Including, An apparatus is further provided, wherein the blood pump does not include any thrust bearing configured to be disposed within a subject's body.

[0049] In some applications, the blood pump further includes one or more thrust bearings configured to be disposed outside the subject's body, and opposition to the thrust generated by rotation of the impeller is provided solely by the one or more thrust bearings disposed outside the subject's body.

[0050] In some applications, the apparatus comprises: a sensor configured to detect an indication of axial movement of the impeller and to generate a sensor signal in response thereto; and a computer processor configured to receive the sensor signal and to generate an output in response thereto; Further includes:

[0051] For some applications, the computer processor is configured to generate an output indicative of a cardiac cycle of the subject in response to receiving the sensor signal. For some applications, the computer processor is configured to determine a left ventricular pressure of the subject based at least in part on the sensor signal. For some applications, the computer processor is configured to vary a rotational speed of the impeller based at least in part on the sensor signal.

[0052] In some applications, the computer processor: configured to determine a left ventricular pressure of the subject based at least in part on the sensor signal; The system is configured to vary the rotational speed of the impeller based at least in part on the determined left ventricular pressure.

[0053] For some applications, the computer processor is configured to reduce the rotational speed of the impeller in response to determining that the subject's left ventricular pressure has decreased.

[0054] In some applications, the apparatus comprises: a magnet, the impeller being coupled to the magnet such that axial movement of the impeller causes the magnet to experience axial movement; a sensor configured to detect magnetic flux generated by the magnet and to generate a sensor signal in response thereto; a computer processor configured to receive the sensor signal and to generate an output in response thereto; Further includes:

[0055] For some applications, the computer processor is configured to generate an output indicative of a cardiac cycle of the subject in response to receiving the sensor signal. For some applications, the computer processor is configured to determine a left ventricular pressure of the subject based at least in part on the sensor signal. For some applications, the computer processor is configured to vary a rotational speed of the impeller based at least in part on the sensor signal.

[0056] In some applications, the computer processor: and configured to determine a left ventricular pressure of the subject based at least in part on the sensor signal. It has been made, The system is configured to vary the rotational speed of the impeller based at least in part on the determined left ventricular pressure.

[0057] For some applications, the computer processor is configured to reduce the rotational speed of the impeller in response to determining that the subject's left ventricular pressure has decreased.

[0058] For some applications, the impeller is configured to pump blood from a first location in the subject's body to a second location in the subject's body, the impeller configured to undergo axial forward and backward motion relative to the frame in response to a periodic change in a pressure differential between the first location and the second location. For some applications, the impeller is configured to pump blood from a left ventricle of the subject to an aorta of the subject, the impeller configured to undergo axial forward and backward motion relative to the frame in response to a periodic change in a pressure differential between the left ventricle and the aorta. For some applications, the impeller is configured to pump blood from a right ventricle of the subject to a pulmonary artery of the subject, the impeller configured to undergo axial forward and backward motion relative to the frame in response to a periodic change in a pressure differential between the right ventricle and the pulmonary artery. For some applications, the impeller is configured to pump blood from a right atrium of the subject to a right ventricle of the subject, the impeller being configured to undergo axial forward and backward motion relative to the frame in response to a periodic change in a pressure differential between the right atrium and the right ventricle. For some applications, the impeller is configured to pump blood from a vena cava of the subject to a right ventricle of the subject, the impeller being configured to undergo axial forward and backward motion relative to the frame in response to a periodic change in a pressure differential between the vena cava and the right ventricle. For some applications, the impeller is configured to pump blood from a right atrium of the subject to a pulmonary artery of the subject, the impeller being configured to undergo axial forward and backward motion relative to the frame in response to a periodic change in a pressure differential between the right atrium and the pulmonary artery. In some applications, the impeller is configured to pump blood from the subject's vena cava to the subject's pulmonary artery, and the impeller is configured to undergo axial forward and backward movement relative to the frame in response to periodic changes in pressure differential between the vena cava and the pulmonary artery.

[0059] In some applications, the apparatus comprises: a motor configured to drive the impeller to rotate the impeller in a given direction of rotation, thereby pumping blood through the subject's body; an axial shaft, the impeller being coupled to the axial shaft; a drive cable configured to extend from outside a subject's body to an axial shaft, the drive cable configured to rotate to impart rotational motion from a motor to an impeller, at least a portion of the drive cable including a plurality of wires arranged in a coiled configuration, the coiled configuration being such that in response to the drive cable rotating in a given direction of rotation, the plurality of wires arranged in the coiled configuration at least partially unwind, causing a portion of the drive cable to axially shorten; Further includes:

[0060] In some applications, The impeller includes a proximal bushing and a distal bushing. The frame includes a proximal bearing and a distal bearing. The apparatus further includes an axial shaft; the axial shaft passes through proximal and distal bearings defined by the frame and proximal and distal bushings of the impeller; the axial shaft is coupled to at least one of the proximal and distal bushings of the impeller such that the at least one bushing is held in an axially fixed position relative to the axial shaft; the axial shaft is not held in an axially fixed position relative to the proximal and distal bearings; The impeller causes the axial shaft to undergo axial forward and backward movement relative to proximal and distal bearings in the frame.

[0061] For some applications, the axial shaft is configured to undergo axial forward and backward movement relative to the proximal and distal bearings of the frame to clean the interface between the axial shaft and the proximal and distal bearings of the frame. For some applications, the axial shaft is configured to undergo axial forward and backward movement relative to the proximal and distal bearings of the frame to reduce heating at the interface between the axial shaft and the proximal and distal bearings of the frame, as opposed to if the axial shaft did not undergo axial forward and backward movement relative to the proximal and distal bearings of the frame.

[0062] According to some applications of the present invention, the following inventive concepts are further provided. Inventive concept 1. An apparatus, comprising: Including the impeller, The impeller is at least one helical elongated element; a spring disposed inside the helical elongated element along an axis around which the helical elongated element winds; a film of material supported between the helical elongate element and the spring; at least one flexible elongate element extending from the spring to the helical elongate element and configured to maintain the helical elongate element within a given distance from the spring, the at least one flexible elongate element being selected from the group consisting of a string and a wire; 13. An apparatus comprising:

[0063] Inventive concept 2. The apparatus of inventive concept 1, wherein the impeller is configured such that in the impeller's radially unconstrained configuration, the outer diameter of the impeller at its largest location is less than 8 mm.

[0064] Inventive concept 3. The apparatus of inventive concept 1, wherein the at least one helical elongate element includes a plurality of helical elongate elements, and at least one flexible elongate element extends from the spring to each of the helical elongate elements.

[0065] Inventive concept 4. The device of any one of Inventive Concepts 1-3, wherein the impeller is configured to pump blood through the body of the subject. Inventive concept 5. The device of inventive concept 4, wherein the impeller is configured to be placed within a blood vessel of a subject.

[0066] Inventive concept 6. The apparatus of inventive concept 4, wherein the impeller is configured to be placed within a cardiac chamber of a subject. Inventive concept 7. An impeller pumps blood from the subject's left ventricle to the subject's aorta. 5. An apparatus according to inventive concept 4, configured to:

[0067] Inventive concept 8. The apparatus of inventive concept 4, wherein the impeller is configured to pump blood from the subject's right ventricle to the subject's pulmonary artery. Inventive concept 9. A method, comprising: placing an impeller within a body of a subject; The impeller is at least one helical elongated element; a spring disposed inside the helical elongated element along an axis around which the helical elongated element winds; a film of material supported between the helical elongate element and the spring; at least one flexible elongate element extending from the spring to the helical elongate element, the helical elongate element being selected from the group consisting of a string and a wire; Including, Also, the method is Pumping blood through the subject's body by rotating the impeller, the flexible elongated element maintaining the helical elongated element within a given distance from the spring during rotation of the impeller. 13. An apparatus comprising:

[0068] Inventive concept 10. An apparatus, comprising: Including a blood pump, The blood pump is an impeller configured to be placed inside a chamber of a subject's heart; a frame configured to be disposed about the impeller; a motor configured to drive the impeller to rotate the impeller and thereby pump blood from the heart chamber to a blood vessel of the subject; Including, The device, wherein the impeller is configured to undergo axial motion relative to the frame in response to cyclic changes in pressure differential between the heart chamber and the blood vessel.

[0069] Inventive concept 11. A method, comprising: placing an impeller of the blood pump inside a chamber of the subject's heart with a frame disposed around the impeller; driving the impeller to rotate the impeller and thereby pump blood from the heart chamber to a blood vessel of the subject; Including, The method includes mounting the impeller inside the heart chamber such that the impeller is permitted to undergo axial movement relative to the frame in response to cyclic changes in pressure differential between the heart chamber and the blood vessel.

[0070] Inventive concept 12. An apparatus, comprising: Including a blood pump, The blood pump is an impeller configured to be placed inside a first blood vessel of a subject; a frame configured to be disposed about the impeller; a motor configured to drive the impeller to rotate the impeller and thereby pump blood from a first blood vessel to a second blood vessel of the subject; Including, The impeller is configured to undergo axial motion relative to the frame in response to a periodic change in a pressure differential between the first vessel and the second vessel, the device.

[0071] Inventive concept 13. A method, comprising: placing an impeller of the blood pump inside a first blood vessel of the subject with a frame disposed around the impeller; driving the impeller to rotate the impeller and thereby pump blood from a first blood vessel to a second blood vessel of the subject; Including, The method, wherein the placement of the impeller inside the first blood vessel is such that the impeller is permitted to undergo axial movement relative to the frame in response to cyclic changes in pressure differential between the heart chamber and the blood vessel.

[0072] Inventive concept 14. An apparatus, comprising: Including a blood pump, The blood pump is an impeller configured to be placed inside a body of a subject and configured to rotate and pump blood through the body of the subject; a frame configured to be disposed about the impeller; one or more thrust bearings configured to be disposed outside the subject's body, wherein opposition to a thrust generated by rotation of the impeller is provided solely by the one or more thrust bearings disposed outside the subject's body; A method comprising:

[0073] Inventive concept 15. A method, comprising: placing an impeller of the blood pump inside a subject's body with a frame disposed around the impeller; driving the impeller to rotate and thereby pump blood through the subject's body, wherein opposition to thrust generated by the rotation of the impeller is provided solely by one or more thrust bearings disposed outside the subject's body; A method comprising:

[0074] Inventive concept 16. An apparatus, comprising: A blood pressure pump tube; a blood pump configured to be disposed within a blood pressure pump tube and configured to pump blood through the blood pressure pump tube; at least one blood pressure measurement tube defining an opening at a distal end thereof, the at least one blood pressure measurement tube configured to extend at least to an outer surface of the blood pressure pump tube, the opening at the distal end of the blood pressure measurement tube being in direct fluid communication with the subject's blood flow outside the blood pressure pump tube; at least one pressure sensor configured to measure the pressure of the subject's blood flow outside the blood pressure pump tubing by measuring the pressure of the blood in the blood pressure measurement tubing; 13. An apparatus comprising:

[0075] Inventive concept 17. The apparatus of inventive concept 16, wherein the blood pump includes an impeller configured to rotate to pump blood through the blood pressure pump tube.

[0076] Inventive concept 18. The apparatus of inventive concept 16, wherein the blood pressure measurement tube is configured to pass along an outer surface of the blood pressure pump tube from a proximal end of the blood pressure pump tube to an opening at the distal end of the blood pressure measurement tube.

[0077] Inventive concept 19. The apparatus of inventive concept 16, further comprising at least one computer processor configured to receive an indication of blood pressure measured in the blood pressure measuring tube and configured to control pumping of blood by the blood pump in response to the blood pressure measured in the blood pressure pump tube.

[0078] Inventive Concept 20. An apparatus according to any one of Inventive Concepts 16 to 19, wherein the at least one blood pressure measurement tube includes at least one left ventricular blood pressure measurement tube configured to extend to an outer surface of the blood pressure pump tube at a location along the tube configured to be within the subject's left ventricle proximal to the blood pump, and the pressure sensor is configured to measure the subject's left ventricular pressure by measuring the pressure of blood in the left ventricular blood pressure measurement tube.

[0079] Inventive concept 21. An apparatus as described in inventive concept 20, wherein the at least one blood pressure measurement tube includes two or more left ventricular blood pressure measurement tubes configured to extend to an outer surface of the blood pressure pump tube at a location along the blood pressure pump tube configured to be within the subject's left ventricle proximal to the blood pump, and the at least one pressure sensor is configured to measure the subject's left ventricular pressure by measuring the pressure of blood in at least one of the left ventricular blood pressure measurement tubes.

[0080] Inventive concept 22. At least one pressure sensor is configured to measure the pressure of blood in each of two or more left ventricular blood pressure measuring tubes; The apparatus further includes at least one computer processor, the at least one computer processor comprising: configured to receive an indication of blood pressure measured in each of the two or more left ventricular blood pressure measuring tubes; in response thereto, configured to determine that an opening of one of the two or more left ventricular blood pressure measurement tubes is blocked; In response thereto, the apparatus according to inventive concept 21 is configured to determine the subject's left ventricular pressure based on blood pressure measured in a different one of the two or more left ventricular blood pressure measuring tubes.

[0081] Inventive concept 23. The apparatus of inventive concept 20, wherein the at least one blood pressure measurement tube further comprises at least one aortic blood pressure measurement tube, the at least one aortic blood pressure measurement tube configured to extend to an outer surface of the blood pressure pump tube at a location along the blood pressure pump tube configured to be within the subject's aorta, and the pressure sensor configured to measure the subject's aortic pressure by measuring the pressure of blood in the aortic blood pressure measurement tube.

[0082] Inventive concept 24. The at least one aortic blood pressure measuring tube includes two or more aortic blood pressure measuring tubes, the two or more aortic blood pressure measuring tubes being in the aorta of the subject. 24. The apparatus of claim 23, wherein the at least one pressure sensor is configured to extend to an outer surface of the blood pressure pump tube at a location along the blood pressure pump tube, and the at least one pressure sensor is configured to measure aortic pressure of the subject by measuring the pressure of blood in at least one of the aortic blood pressure measurement tubes.

[0083] Inventive Concept 25. An apparatus according to any one of Inventive Concepts 16 to 19, wherein the at least one blood pressure measurement tube includes at least one aortic blood pressure measurement tube, the at least one aortic blood pressure measurement tube configured to extend to an outer surface of the blood pressure pump tube at a location along the blood pressure pump tube such that the at least one aortic blood pressure measurement tube is configured to be within the aorta of the subject, and the pressure sensor is configured to measure the aortic pressure of the subject by measuring the pressure of blood in the aortic blood pressure measurement tube.

[0084] Inventive concept 26. Apparatus according to inventive concept 25, wherein the at least one aortic blood pressure measuring tube includes two or more aortic blood pressure measuring tubes configured to extend to an outer surface of the blood pressure pump tube at a location along the blood pressure pump tube configured to be within the subject's aorta, and the at least one pressure sensor is configured to measure the subject's aortic pressure by measuring the pressure of blood in at least one of the aortic blood pressure measuring tubes.

[0085] Inventive concept 27. At least one pressure sensor is configured to measure the pressure of blood in each of two or more aortic blood pressure measuring tubes; The apparatus further includes at least one computer processor, the at least one computer processor comprising: configured to receive an indication of blood pressure measured in each of the two or more aortic blood pressure measuring tubes; in response thereto, configured to determine that an opening of one of the two or more aortic blood pressure measurement tubes is occluded; In response thereto, the apparatus of inventive concept 26 is configured to determine the subject's aortic pressure based on blood pressure measured in a different one of the two or more aortic blood pressure measuring tubes.

[0086] Inventive Concept 28. An apparatus according to any one of Inventive Concepts 16 to 19, wherein the blood pressure measurement tube is configured to extend from outside the subject's body to an opening at a distal end, and at least one pressure sensor is configured to be disposed outside the subject's body.

[0087] Inventive concept 29. A blood pump includes an impeller disposed on an axial shaft, the impeller being configured to rotate to pump blood from a left ventricle to an aorta, the apparatus comprising: a motor disposed outside the subject's body, the motor configured to drive the impeller to rotate; and a drive cable extending from outside the subject's body to the axial shaft, the drive cable configured to rotate to impart rotational motion from the motor to the impeller; an outer tube configured to extend from outside the subject's body into the blood pressure pump tube; Further comprising: 29. The apparatus of inventive concept 28, wherein the drive cable and blood pressure measurement tubing are configured to be disposed within the outer tube.

[0088] Inventive concept 30. The at least one blood pressure measurement tube includes at least one left ventricular blood pressure measurement tube configured to extend to an outer surface of the blood pressure pump tube at a location along the blood pressure pump tube configured to be in the left ventricle of the subject proximal to the blood pump, and the at least one pressure sensor configured to measure a left ventricular pressure of the subject by measuring a pressure of blood in the left ventricular blood pressure measurement tube; the device further includes an aortic blood pressure measurement tube defining an opening at a distal end thereof, the aortic blood pressure measurement tube configured to extend from outside the subject's body to an outer surface of the outer tube within the subject's aorta, such that the opening at the distal end of the blood pressure measurement tube is in direct fluid communication with the subject's aortic blood flow; 30. The apparatus of inventive concept 29, wherein the at least one pressure sensor is further configured to measure the subject's aortic pressure by measuring the pressure of blood in the aortic blood pressure measuring tube.

[0089] Inventive concept 31. The at least one blood pressure measurement tube includes at least one left ventricular blood pressure measurement tube configured to extend to an outer surface of the blood pressure pump tube at a location along the blood pressure pump tube configured to be in the left ventricle of the subject proximal to the blood pump, and the at least one pressure sensor configured to measure a left ventricular pressure of the subject by measuring a pressure of blood in the left ventricular blood pressure measurement tube; the device further includes an aortic blood pressure measurement tube defining an opening at a distal end thereof, the aortic blood pressure measurement tube configured to extend from outside the subject's body to a portion of an outer surface of the outer tube disposed within the blood pressure pump tube, such that the opening at the distal end of the blood pressure measurement tube is in direct fluid communication with the subject's aortic blood flow; 30. The apparatus of inventive concept 29, wherein the at least one pressure sensor is further configured to measure the subject's aortic pressure by measuring the pressure of blood in the aortic blood pressure measuring tube.

[0090] Inventive concept 32. An apparatus as described in inventive concept 29, wherein the outer tube defines a groove in a portion of an outer surface of the outer tube configured to be disposed within the blood pressure pump tube, and a portion of the blood pressure measurement tube configured to extend from within the blood pressure pump tube to the outer surface of the blood pressure pump tube during insertion of the ventricular assist device into the subject's body is configured to be disposed within the groove, such that the portion of the blood pressure measurement tube does not protrude from the outer surface of the outer tube.

[0091] Inventive concept 33. The apparatus of inventive concept 28, wherein the diameter of the blood pressure measuring tube, at least in a distal portion of the blood pressure measuring tube, is less than 0.5 mm. Inventive concept 34. The apparatus of inventive concept 33, wherein the diameter of the blood pressure measuring tube, at least in a distal portion of the blood pressure measuring tube, is greater than 0.2 mm.

[0092] Inventive concept 35. A method, comprising: Blood pressure pump tubing, a blood pump disposed within the blood pressure pump tube; and At least one blood pressure measurement tube, the at least one blood pressure measurement tube defining an opening at a distal end thereof, the at least one blood pressure measurement tube extending to at least an outer surface of the blood pressure pump tube, such that the opening at the distal end of the blood pressure measurement tube is in direct fluid communication with the blood flow of the subject outside the blood pressure pump tube, is inserted into the body of the subject. and pumping blood through a blood pressure pump tube using a blood pump; measuring the pressure of the subject's blood flow outside the blood pressure pump tubing by measuring the pressure of the blood in the blood pressure measurement tubing; A method comprising:

[0093] Inventive concept 36. An apparatus, comprising: Including a blood pump, The blood pump is Tube and an impeller configured to be disposed within the tube and configured to rotate and pump blood through the tube; A frame disposed around the impeller; a stator configured to reduce a rotational flow component from the blood flow generated by rotation of the impeller; and Including, The stator is a plurality of struts, the plurality of struts being integral with the frame, the plurality of struts being curved; a flexible material connected to the curved struts and adapted to form a plurality of curved projections; 13. An apparatus comprising:

[0094] Inventive concept 37. The apparatus of inventive concept 36, wherein the curvature of the curved protrusion opposes the direction of rotation of the impeller. Inventive concept 38. The device of inventive concept 36, wherein the curvature of the curved protrusion is such that from the distal end of the curved protrusion to the proximal end of the curved protrusion, the curved protrusion becomes progressively closer to being parallel to the longitudinal axis of the frame.

[0095] Inventive concept 39. The device of inventive concept 36, wherein the flexible material is shaped to define a lumen therethrough. Inventive concept 40. A method, comprising: placing a blood pump within a body of a subject; The blood pump is Tube and an impeller configured to be disposed within the tube; A frame disposed around the impeller; A stator including a plurality of struts and a flexible material, the plurality of struts being integral with a frame, the plurality of struts being curved, and the flexible material being coupled to the curved struts to form a plurality of curved projections. Including, Also, the method is Pumping blood through a tube using an impeller, the stator reducing rotational flow components from the blood flow generated by rotation of the impeller. A method comprising:

[0096] Inventive concept 41. An apparatus, comprising: ventricular assist devices, Ventricular assist devices are An axial shaft; an impeller disposed on the axial shaft, the impeller configured to be placed in a left ventricle of a subject; and a motor configured to be disposed outside a body of a subject, the motor configured to drive an impeller to rotate the impeller and thereby pump blood from a left ventricle to an aorta of the subject; a drive cable configured to extend from outside the subject's body to the axial shaft, the drive cable configured to rotate to impart rotational motion from the motor to the impeller, the drive cable including a first portion configured to be at least partially disposed within the subject's aortic arch and a second portion configured to be at least partially disposed within the subject's descending aorta; Including, The device, wherein a first portion of the drive cable includes a first number of wires arranged in a coiled configuration and a second portion of the drive cable includes a second number of wires arranged in a coiled configuration, the first number being smaller than the second number.

[0097] Inventive concept 42. The apparatus of inventive concept 41, wherein the length of the first portion of the drive cable is between 20 cm and 40 cm. Inventive concept 43. The apparatus of inventive concept 41, wherein the length of the second portion of the drive cable is between 60 cm and 100 cm.

[0098] Inventive concept 44. An apparatus as described in inventive concept 41, wherein a first portion of the drive cable includes between 4 and 8 wires arranged in a coiled configuration and a second portion of the drive cable includes between 8 and 12 wires arranged in a coiled configuration.

[0099] Inventive concept 45. An apparatus, comprising: Including a blood pump, The blood pump is An axial shaft; an impeller disposed on the axial shaft; a motor configured to be disposed outside a body of a subject, the motor configured to drive an impeller to rotate the impeller and thereby pump blood through the body of the subject; a drive cable configured to extend from outside the subject's body to the axial shaft, the drive cable configured to rotate to impart rotational motion from the motor to the impeller, the drive cable including a first portion configured to be at least partially disposed in a curved portion of the subject's vasculature and a second portion configured to be at least partially disposed in a straight portion of the subject's vasculature; Including, The device, wherein a first portion of the drive cable includes a first number of wires arranged in a coiled configuration and a second portion of the drive cable includes a second number of wires arranged in a coiled configuration, the first number being smaller than the second number.

[0100] Inventive concept 46. An apparatus, comprising: Including a blood pump, The blood pump is An axial shaft; an impeller disposed on the axial shaft; a motor configured to be disposed outside a body of a subject, the motor configured to drive an impeller to rotate the impeller in a given direction of rotation, thereby pumping blood from a distal end of the impeller to a proximal end of the impeller; a drive cable configured to extend from outside the subject's body to the axial shaft, the drive cable configured to rotate to impart rotational motion from the motor to the impeller; and Including, The device, wherein at least a portion of the drive cable includes a plurality of wires arranged in a coiled configuration, the coiled configuration being such that in response to the drive cable rotating in a given direction of rotation, the plurality of wires arranged in the coiled configuration at least partially unwind, causing a portion of the drive cable to axially shorten.

[0101] Inventive concept 47. A device as described in inventive concept 46, wherein the impeller is configured to pump blood from a first location to a second location, and the impeller is configured to undergo axial forward and backward motion in response to a cyclic change in pressure differential between the first location and the second location.

[0102] Inventive concept 48. A method, comprising: placing a blood pump within a body of a subject; The blood pump is An axial shaft; an impeller disposed on the axial shaft; a drive cable extending from outside the subject's body to the axial shaft; Including, Also, the method is driving the impeller to pump blood from a distal end of the impeller to a proximal end of the impeller by imparting rotational motion to the impeller via a drive cable, at least a portion of the drive cable including a plurality of wires arranged in a coiled configuration such that in response to the drive cable rotating in a given direction of rotation, the plurality of wires arranged in the coiled configuration at least partially unwinds, causing a portion of the drive cable to axially shorten. A method comprising:

[0103] Inventive concept 49. An apparatus, comprising: Including a blood pump, The blood pump is An axial shaft; an impeller disposed on the axial shaft; a motor configured to be disposed outside a body of a subject, the motor configured to drive an impeller to pump blood in a proximal direction by rotating the impeller in a given direction of rotation; a drive cable, the drive cable being disposed outside the subject's body; a drive cable configured to extend from a proximal end of the cable to a distal end of the drive cable, the distal end of the drive cable being coupled to the axial shaft, the drive cable configured to rotate to impart rotational motion from the motor to the impeller; an outer tube disposed around the drive cable; a fluid disposed between the outer tube and the drive cable; Including, The device, wherein at least a portion of the drive cable includes a plurality of wires arranged in a coiled configuration, the coiled configuration being such that in response to the drive cable rotating in a given direction of rotation, the plurality of wires are configured to pump fluid toward a proximal end of the drive cable.

[0104] Inventive concept 50. A method, comprising: placing a blood pump within a body of a subject; The blood pump is An axial shaft; an impeller disposed on the axial shaft; a drive cable extending from outside the subject's body to the axial shaft, an outer tube being disposed about the drive cable; a fluid disposed between the drive cable and the outer tube; Including, Also, the method is driving the impeller to pump blood from a distal end of the impeller to a proximal end of the impeller by imparting rotational motion to the impeller via a drive cable, at least a portion of the drive cable including a plurality of wires arranged in a coiled configuration such that in response to the drive cable rotating in a given direction of rotation, the plurality of wires are configured to pump fluid toward the proximal end of the drive cable. A method comprising:

[0105] Inventive concept 51. An apparatus, comprising: Including a blood pump, The blood pump is The impeller, a motor configured to drive an impeller to rotate the impeller and thereby pump blood, the impeller being configured to undergo axial motion in response to changes in a pressure differential against which the impeller is pumping blood; and a magnet, the impeller being coupled to the magnet such that axial movement of the impeller causes the magnet to experience axial movement; a sensor configured to detect magnetic flux generated by the magnet and, in response thereto, generate a sensor signal; and a computer processor configured to receive the sensor signal and, in response thereto, generate an output; 13. An apparatus comprising:

[0106] Inventive concept 52. The method of inventive concept 51, wherein the computer processor is configured to generate an output indicative of the subject's cardiac cycle in response to receiving the sensor signal. The apparatus described.

[0107] Inventive concept 53. The apparatus of inventive concept 51, wherein the computer processor is configured to determine a left ventricular pressure of the subject based at least in part on the sensor signal.

[0108] Inventive concept 54. The apparatus of any one of inventive concepts 51-53, wherein the computer processor is configured to vary the rotational speed of the impeller based at least in part on the sensor signal.

[0109] Inventive Concept 55. A computer processor is configured to determine a left ventricular pressure of the subject based at least in part on the sensor signal; 55. An apparatus according to inventive concept 54, configured to vary the rotational speed of the impeller based at least in part on the determined left ventricular pressure.

[0110] Inventive concept 56. The apparatus of inventive concept 55, wherein the computer processor is configured to reduce the rotational speed of the impeller in response to determining that the subject's left ventricular pressure has decreased.

[0111] Inventive concept 57. An apparatus, comprising: Including a blood pump, The blood pump is The impeller, a motor configured to drive an impeller to rotate the impeller and thereby pump blood, the impeller being configured to undergo axial motion in response to changes in a pressure differential against which the impeller is pumping blood; and a sensor configured to detect an indication of axial movement of the impeller and, in response thereto, generate a sensor signal; and a computer processor configured to receive the sensor signal and, in response thereto, generate an output; 13. An apparatus comprising:

[0112] Inventive concept 58. A method, comprising: placing a blood pump inside a subject's body, the blood pump including an impeller; driving the impeller to rotate and thereby pump blood, the impeller being configured to undergo axial motion in response to changes in the pressure differential against which the impeller is pumping blood; detecting an indication of axial movement of the impeller and, in response thereto, generating a sensor signal; receiving a sensor signal and, in response thereto, generating an output; A method comprising:

[0113] Inventive concept 59. An apparatus, comprising: Including a blood pump, The blood pump is The impeller, Frame and Including, the impeller and the frame are configured to be inserted into a body of a subject such that the frame is disposed about the impeller within the body of the subject; The device also includes: An apparatus comprising: a computer processor configured to drive a motor unit to simultaneously (a) drive an impeller to rotate, thereby pumping blood through a subject's body, and (b) drive the impeller to move axially within a frame in a forward and backward motion.

[0114] Inventive concept 60. A method, comprising: placing a blood pump including an impeller and a frame into a body of a subject, the frame being adapted to be disposed about the impeller; at the same time, driving the impeller to rotate and thereby pump blood through the body of the subject; driving the impeller to move axially through the frame in a forward and backward motion; A method comprising:

[0115] Inventive concept 61. An apparatus, comprising: Including a blood pump, The blood pump is An axial shaft; an impeller disposed on the axial shaft and configured to be placed within a left ventricle of a subject; and a motor configured to be disposed outside a body of a subject and configured to drive the impeller to rotate; and a drive cable configured to extend from outside the subject's body to the axial shaft through the subject's aortic arch, the drive cable configured to rotate to impart rotational motion from the motor to the impeller; a tube, the drive cable configured to be disposed within the tube during rotation of the drive cable, the tube configured to remain stationary during rotation of the drive cable; and a plurality of ball bearings configured to be disposed between the drive cable and the tube, the plurality of ball bearings configured to reduce friction between the drive cable and the tube during movement of the drive cable relative to the tube; 13. An apparatus comprising:

[0116] Inventive concept 62. An apparatus as described in inventive concept 61, wherein the ball bearing is configured to be disposed between the drive cable and the tube, at least a portion of the drive cable and the tube being configured to be disposed in the aortic arch of the subject during rotation of the impeller.

[0117] Inventive concept 63. An apparatus, comprising: Including a blood pump, The blood pump is An axial shaft; an impeller disposed on the axial shaft and configured to be placed inside a body of a subject; and a motor configured to be disposed outside a body of a subject; a drive cable configured to extend from outside the subject's body to the axial shaft; precisely two drive magnets arranged in a drive magnet housing, the drive magnet housing being connected to the motor; a driven magnet, the driven magnet coupled to the drive cable and disposed between the drive magnets such that axial overlap exists between the drive magnet and the driven magnet, the driven magnet defining a single north pole and a single south pole split along an axial length of the driven magnet, and a motor configured to impart rotational motion to the impeller by rotating the drive magnet housing, thereby rotating the driven magnet, thereby rotating the drive cable; and 13. An apparatus comprising:

[0118] Inventive concept 64. A method, comprising: placing a blood pump within a body of a subject; The blood pump is An axial shaft; an impeller disposed on the axial shaft; a drive cable extending from outside the subject's body to the axial shaft; Including, Also, the method is Driving the impeller in rotation by using the motor to rotate precisely two drive magnets disposed in a drive magnet housing connected to the motor. Including, The method, wherein the drive magnet is configured to thereby drive the driven magnet to rotate, the driven magnet is coupled to a drive cable and disposed between the drive magnets such that axial overlap exists between the drive magnet and the driven magnet, and the driven magnet defines a single north pole and a single south pole split along the axial length of the driven magnet.

[0119] Inventive concept 65. An apparatus, comprising: Including a blood pump, The blood pump is An axial shaft; an impeller disposed on the axial shaft and configured to be placed inside a body of a subject; and a motor configured to be disposed outside a body of a subject; a drive cable configured to extend from outside the subject's body to the axial shaft; precisely two driven magnets disposed in a driven magnet housing, the drive magnet housing being connected to the motor; a drive magnet coupled to the motor and disposed between the driven magnets such that an axial overlap exists between the driven magnet and the drive magnet, the drive magnet defining a single north pole and a single south pole split along an axial length of the drive magnet, the motor rotating the drive magnet; Thus, the drive magnet is configured to rotate the drive cable by rotating the driven magnet, thereby imparting rotational motion to the impeller. 13. An apparatus comprising:

[0120] Inventive concept 66. A method, comprising: placing a blood pump within a body of a subject; The blood pump is An axial shaft; an impeller disposed on the axial shaft; a drive cable extending from outside the subject's body to the axial shaft; Including, Also, the method is Driving the impeller in rotation by using the motor to rotate a drive magnet coupled to the motor, the drive magnet defining a single north pole and a single south pole split along an axial length of the drive magnet. Including, The method, wherein the drive magnet is configured to thereby drive the driven magnet to rotate, the driven magnet including precisely two driven magnets disposed in a driven magnet housing, the driven magnet housing being coupled to the drive cable and disposed around the drive magnet.

[0121] Inventive concept 67. An apparatus, comprising: Including a blood pump, The blood pump is An axial shaft; an impeller disposed on the axial shaft and configured to be placed inside a body of a subject; and a motor configured to be disposed outside a subject's body and configured to drive an impeller to rotate the impeller in a given direction of rotation and thereby pump blood; a drive cable configured to extend from outside a subject's body to an axial shaft, the drive cable configured to rotate to impart rotational motion from the motor to the impeller, the drive cable including a plurality of wires, the plurality of wires being arranged in a coiled configuration, the plurality of wires being coupled to the axial shaft; Including, The apparatus, wherein the axial shaft defines a groove at an interface between the drive cable and the axial shaft, the groove being configured such that stresses generated by the wire at the interface are spread across a radius of the groove.

[0122] Inventive concept 68. An apparatus, comprising: Including a blood pump, The blood pump is An axial shaft; an impeller disposed on the axial shaft and configured to be placed inside a body of a subject; and a motor configured to be disposed outside a subject's body and configured to drive an impeller to rotate the impeller in a given direction of rotation and thereby pump blood; a drive cable configured to extend from outside a subject's body to an axial shaft, the drive cable configured to rotate to impart rotational motion from the motor to the impeller, the drive cable including a plurality of wires, the plurality of wires being arranged in a coiled configuration, the plurality of wires being coupled to the axial shaft; Including, The coiled wire is configured such that as the coiled wire approaches the interface between the drive cable and the axial shaft, the pitch of the wire is increased such that stresses at the location where the drive cable wire is coupled to the axial shaft are reduced relative to if the pitch of the wire was not increased.

[0123] Inventive concept 69. An apparatus, comprising: Including a blood pump, The blood pump is An axial shaft; an impeller disposed on the axial shaft and configured to be placed inside a body of a subject; and a motor configured to be disposed outside a subject's body and configured to drive an impeller to rotate the impeller in a given direction of rotation and thereby pump blood; a drive cable configured to extend from outside the subject's body to the axial shaft, the drive cable configured to rotate to impart rotational motion from the motor to the impeller; a drive cable including first and second portions, the first portion of the drive cable including a first number of wires arranged in a coiled configuration, and the second portion of the drive cable including a second number of wires arranged in a coiled configuration, the first number being less than the second number; an interface component, wherein the first and second portions of the drive cable are coupled to one another via the interface component; the interface component defines a groove at an interface between at least one of the drive cable portions and the interface component, the groove being configured such that stresses generated by the wire at the interface are spread across a radius of the groove; 13. An apparatus comprising:

[0124] Inventive concept 70. An apparatus, comprising: Including a blood pump, The blood pump is An axial shaft; an impeller disposed on the axial shaft and configured to be placed inside a body of a subject; and a motor configured to be disposed outside a subject's body and configured to drive an impeller to rotate the impeller in a given direction of rotation and thereby pump blood; a drive cable configured to extend from outside the subject's body to the axial shaft, the drive cable configured to rotate to impart rotational motion from the motor to the impeller; The drive cable includes first and second sections, the first section of the drive cable including a first number of wires arranged in a coiled configuration, and the second section of the drive cable including a first number of wires arranged in a coiled configuration. a drive cable including a second number of wires arranged in a coiled configuration, the first number being less than the second number; an interface component, wherein the first and second portions of the drive cable are coupled to one another via the interface component; a coiled wire of at least one of the portions of the drive cable is configured such that the pitch of the coiled wire is increased as the coiled wire approaches the interface component such that stresses at the location where the wire is coupled to the interface component are reduced relative to if the pitch of the wire was not increased; and 13. An apparatus comprising:

[0125] Inventive concept 71. An apparatus, comprising: ventricular assist devices, Ventricular assist devices are a tube configured to traverse an aortic valve of a subject such that a proximal portion of the tube is disposed within the aorta of the subject and a distal portion of the tube is disposed within a left ventricle of the subject, the tube defining one or more blood inlet openings in the distal portion of the tube and one or more blood outlet openings in the proximal portion of the tube; a blood pump configured to be disposed within the tube and configured to pump blood from the left ventricle into the tube through one or more blood inlet openings and out of the tube into the aorta through one or more blood outlet openings; a radially expandable atraumatic distal tip portion configured to be disposed within a left ventricle of a subject distal to one or more blood inlet openings, the distal tip portion configured to be inserted into the left ventricle in a radially constrained configuration and configured to assume a radially unconstrained configuration within the left ventricle of the subject, wherein in the radially unconstrained configuration, at least the radially expandable portion of the distal tip portion is radially expanded relative to the radially constrained configuration of the distal tip portion; 13. An apparatus comprising:

[0126] Inventive concept 72. The device of inventive concept 71, wherein the distal tip portion comprises a braided shape memory alloy that is at least partially covered by a blood impermeable material. Inventive concept 73. The device of inventive concept 71, wherein the distal tip portion is configured such that in a radially unconstrained configuration of the distal tip portion, a radially expandable portion of the distal tip portion separates one or more blood inlet openings from the interventricular septum in the left ventricle.

[0127] Inventive concept 74. The device of inventive concept 71, wherein the distal tip portion is configured such that in a radially unconstrained configuration of the distal tip portion, a radially expandable portion of the distal tip portion separates one or more blood inlet openings from a tendon in the left ventricle.

[0128] Inventive concept 75. The device of inventive concept 71, wherein the distal tip portion is configured such that in a radially unconstrained configuration of the distal tip portion, a radially expandable portion of the distal tip portion separates one or more blood inlet openings from papillary muscles within the left ventricle.

[0129] Inventive concept 76. The device of inventive concept 71, wherein the distal tip portion is configured such that in a radially unconstrained configuration of the distal tip portion, a radially expandable portion of the distal tip portion separates one or more blood inlet openings from the apex within the left ventricle.

[0130] Inventive concept 77. The device of inventive concept 71, wherein the distal tip portion is configured such that in a radially unconstrained configuration of the distal tip portion, the radially expandable portion of the distal tip portion three-dimensionally separates one or more blood inlet openings from internal structures within the left ventricle.

[0131] Inventive concept 78. The device of inventive concept 71, wherein the distal tip portion is configured such that in a radially unconstrained configuration of the distal tip portion, the radially expandable portion of the distal tip portion directs blood flow from the left ventricle into one or more blood inlet openings.

[0132] Inventive concept 79. In a radially constrained configuration of the distal tip portion, a distal region of the distal tip portion is configured to be at least semi-rigid and configured to radially converge along a longitudinal direction toward a distal end of the distal tip portion; the ventricular assist device is configured to be inserted into a body of a subject via a puncture in the body of the subject; An apparatus according to any one of inventive concepts 71-78, wherein a distal region of the distal tip portion is configured to act as a dilator by dilating the puncture during insertion of the ventricular assist device.

[0133] Inventive concept 80. A device according to any one of inventive concepts 71-78, wherein the distal tip portion is configured such that in a radially unconstrained configuration of the distal tip portion, a distal end of the distal tip portion is encased within a radially expandable portion of the distal tip portion.

[0134] Inventive concept 81. The device of inventive concept 80, wherein the distal tip portion is configured to prevent the distal end of the distal tip portion from becoming entangled in the left ventricular tendon by being encased within the radially enlarged portion of the distal tip portion.

[0135] Inventive concept 82. The device of inventive concept 80, wherein the distal tip portion is configured to prevent the distal end of the distal tip portion from causing trauma to internal structures of the left ventricle by encasing the distal end of the distal tip portion within the radially expandable portion of the distal tip portion.

[0136] Inventive concept 83. A device as described in inventive concept 80, wherein a distal end of the distal tip portion is configured to be enveloped within the radially expandable portion of the distal tip portion by everting the distal end of the distal tip portion.

[0137] Inventive concept 84. A device as described in inventive concept 80, wherein a distal end of the distal tip portion is configured to be enveloped within the radially expandable portion of the distal tip portion by retracting the distal end of the distal tip portion proximally, such that the distal end is disposed within the radially expandable portion of the distal tip portion.

[0138] Inventive concept 85. An apparatus, comprising: a ventricular assist device configured to be inserted into the body of the subject through the puncture; Ventricular assist devices are a tube configured to traverse an aortic valve of a subject such that a proximal portion of the tube is disposed within the aorta of the subject and a distal portion of the tube is disposed within a left ventricle of the subject, the tube defining one or more blood inlet openings in the distal portion of the tube and one or more blood outlet openings in the proximal portion of the tube; a blood pump configured to be disposed within the tube and configured to pump blood from the left ventricle into the tube through one or more blood inlet openings and out of the tube into the aorta through one or more blood outlet openings; a distal tip portion, the distal tip portion is configured to have a radially constrained configuration, in which a distal region of the distal tip portion is at least partially rigid and shaped to converge radially along a longitudinal direction toward a distal end of the distal tip portion, the distal region being configured to act as a dilator by dilating the puncture during insertion of the ventricular assist device into the body of a subject; and a distal tip portion configured to have a radially unconstrained configuration, the distal tip region configured to assume a radially unconstrained configuration within a left ventricle of a subject, wherein in the radially unconstrained configuration, a radially expandable portion of the distal tip portion is configured to be atraumatic and to separate the one or more blood inlet openings from internal structures of the left ventricle of the subject. 13. An apparatus comprising:

[0139] Inventive concept 86. A method, comprising: operating a blood pump; The blood pump is An axial shaft; an impeller disposed on the axial shaft and disposed within a left ventricle of the subject; a motor, the motor disposed outside the subject's body and configured to drive the impeller to rotate; and a drive cable that extends from outside the subject's body through the subject's aortic arch to the axial shaft and is configured to rotate to impart rotational motion from the motor to the impeller; and a tube, the drive cable being disposed within the tube, the tube being configured to remain stationary during rotation of the drive cable; Including, Also, the method is While operating the blood pump, pumping fluid into a space between the drive cable and the tubing such that the fluid fills the space between the drive cable and the tubing but does not release fluid into the subject's blood stream. A method comprising:

[0140] Inventive concept 87. A method, comprising: operating a blood pump; The blood pump is An axial shaft; an impeller disposed on the axial shaft and disposed within a left ventricle of the subject; a motor, the motor disposed outside the subject's body and configured to drive the impeller to rotate; and a drive cable that extends from outside the subject's body through the subject's aortic arch to the axial shaft and is configured to rotate to impart rotational motion from the motor to the impeller; and a tube, the drive cable being disposed within the tube, the tube being configured to remain stationary during rotation of the drive cable; Including, Also, the method is pumping fluid into a space between the drive cable and the tubing prior to operating the blood pump, such that the fluid fills the space between the drive cable and the tubing but does not release fluid into the subject's blood stream; leaving fluid in the space between the drive cable and the tubing during operation of the blood pump; A method comprising:

[0141] Inventive concept 88. An apparatus, comprising: a left ventricular assist device configured to assist left ventricular function in the subject; Left ventricular assist devices a tube configured to traverse an aortic valve of a subject such that a proximal portion of the tube is at least partially disposed in an ascending aorta of the subject and a distal portion of the tube is at least partially disposed in a left ventricle of the subject; a frame disposed within the distal portion of the tube, the frame configured to hold the distal portion of the tube open; the frame is not disposed within the proximal portion of the tube, whereby the proximal portion of the tube is configured to collapse inwardly in response to pressure outside the proximal portion of the tube exceeding pressure inside the proximal portion of the tube; and a pump disposed within the frame and configured to pump blood through a tube from a left ventricle of the subject to an aorta of the subject, the proximal portion of the tube being maintained in an open state when blood pressure generated by the blood pump in a proximal portion of the tube exceeds the subject's aortic pressure outside the proximal portion of the tube; a plurality of elongated commissure elements disposed within a proximal portion of the tube such that when the proximal portion of the tube collapses inwardly, respective portions of the circumference of the tube form cusps that contact one another; 13. An apparatus comprising:

[0142] Inventive concept 89. The apparatus of inventive concept 88, further comprising a computer processor, the computer processor configured to control pumping of blood through the tube by the blood pump such that blood pressure generated by the blood pump in the tube exceeds a systolic aortic pressure of the subject and is less than a diastolic aortic pressure of the subject.

[0143] Inventive concept 90. The apparatus of inventive concept 88, further comprising a pressure sensor configured to measure an aortic blood pressure of the subject, the computer processor configured to receive an indication of the measured aortic blood pressure and configured to control pumping of blood through the tube by the blood pump responsive to the measured aortic blood pressure.

[0144] Inventive concept 91. The apparatus of inventive concept 88, further comprising a pressure sensor configured to measure a left ventricular blood pressure of the subject, the computer processor configured to receive an indication of the measured left ventricular blood pressure and configured to control pumping of blood through the tube by the blood pump responsive to the measured left ventricular blood pressure.

[0145] Inventive concept 92. An apparatus for use with a delivery device, the apparatus comprising: The impeller, A frame disposed around the impeller, the impeller and the frame are configured to be inserted into a blood vessel of a subject via a delivery device while disposed in a radially constrained configuration, and the frame is configured to be released from the delivery device to assume a radially unconstrained configuration; a coupling element including a first portion and a second portion, the first portion being disposed on the impeller and the second portion being disposed on the frame and configured to engage with the first portion, the coupling element being configured to facilitate radial contraction of the impeller by retaining an end of the impeller such that the impeller can elongate axially without radial contraction of the frame; 13. An apparatus comprising:

[0146] Inventive concept 93. An apparatus, comprising: A blood pressure pump tube; an impeller configured to be disposed within a blood pressure pump tube and configured to pump blood from a first location to a second location by pumping blood through the blood pressure pump tube; a motor, the motor disposed outside the subject's body and configured to drive the impeller to rotate; and a drive cable extending from outside the subject's body to the axial shaft and configured to rotate to impart rotational motion from the motor to the impeller; and an outer tube disposed about a drive cable configured to extend from outside the subject's body into a blood pressure pump tube, the outer tube defining first and second openings over a portion of the outer tube that is disposed within the blood pressure pump tube; a flow obstruction disposed above a first opening, the first opening configured to function as a stagnation pressure tap and the second opening configured to function as a stationary pressure tap; at least one pressure sensor configured to measure a pressure in a stagnation pressure tap and a pressure in a static pressure tap; a computer processor configured to determine a flow through the blood pressure pump tubing based at least in part on the pressure measured at the stagnation pressure tap and the pressure measured at the stationary pressure tap; 13. An apparatus comprising:

[0147] Inventive concept 94. A method, comprising: inserting a blood pump into a subject; The blood pump is an impeller including a proximal bushing and a distal bushing; a frame disposed around the impeller, the frame including a proximal bearing and a distal bearing; an axial shaft, the axial shaft passing through proximal and distal bearings of the frame and proximal and distal bushings of the impeller, the proximal bushing of the impeller being connected to the axial shaft such that the proximal bushing is held in an axially fixed position relative to the axial shaft, and the distal bushing of the impeller not being connected to the axial shaft such that the distal bushing is not held in an axially fixed position relative to the axial shaft; and Including, the impeller is maintained in a radially constrained configuration by a delivery catheter while the impeller is inserted into the subject's body; Also, the method is causing the impeller to change from its radially constrained configuration to a radially unconstrained configuration by allowing the distal bushing to slide over the axial shaft by releasing the impeller from the catheter when the impeller is disposed within the subject's body; and pumping blood through the subject's body using the impeller while the impeller is disposed in a radially unconstrained configuration.

[0148] Inventive concept 95. A method, comprising: placing an impeller of the ventricular assist device inside the left ventricle of the subject with a frame disposed around the impeller; driving the impeller to rotate the impeller and thereby pump blood from the left ventricle to the aorta of the subject; Including, The method includes mounting the impeller inside the left ventricle such that the impeller is permitted to undergo axial movement relative to the frame in response to cyclic changes in pressure differential between the left ventricle and the aorta.

[0149] Inventive concept 96. A method, comprising: placing a blood pump inside the subject; The blood pump is an impeller comprising a frame disposed about the impeller, the impeller including a proximal bushing and a distal bushing, the frame including a proximal bearing and a distal bearing; an axial shaft, the axial shaft passing through proximal and distal bearings of the frame and proximal and distal bushings of the impeller, the axial shaft being coupled to at least one of the proximal and distal bushings of the impeller such that the at least one bushing is held in an axially fixed position relative to the axial shaft and is not held in an axially fixed position relative to the proximal and distal bearings; Including, The method also includes using an impeller to pump blood through the subject's body. The method includes the steps of:

[0150] Inventive concept 97. A method, comprising: placing an impeller of the blood pump inside a subject's body with a frame disposed around the impeller; driving the impeller to pump blood through the subject's body without the use of any thrust bearings disposed within the subject's body to provide opposition to the thrust generated by rotation of the impeller; A method comprising:

[0151] The present invention will be more fully understood from the following detailed description of the embodiments thereof, considered in conjunction with the drawings. [Brief description of the drawings]

[0152] [Figure 1A] FIG. 1 is a schematic illustration of a ventricular assist device according to some applications of the present invention, showing a distal end of the ventricular assist device disposed within the left ventricle of a subject. [Figure 1B] FIG. 1 is a schematic illustration of a ventricular assist device according to some applications of the present invention, showing a distal end of the ventricular assist device disposed within the left ventricle of a subject. [Figure 2A]1 is a schematic illustration of a pump portion of a ventricular assist device according to some applications of the present invention. [Figure 2B] 1 is a schematic illustration of a pump portion of a ventricular assist device according to some applications of the present invention. [Figure 2C] 1 is a schematic illustration of a pump portion of a ventricular assist device according to some applications of the present invention. [Diagram 3] 3A, 3B, and 3C are schematic illustrations of an impeller of a ventricular assist device, according to some applications of the present invention; [Figure 4] 1 is a schematic illustration of an impeller disposed inside a frame of a ventricular assist device, according to some applications of the present invention. [Figure 5A] 1 is a schematic illustration of an impeller and frame of a ventricular assist device in its radially unconstrained state, in accordance with some applications of the present invention. [Figure 5B] 1 is a schematic illustration of an impeller and frame of a ventricular assist device in its radially constrained state, in accordance with some applications of the present invention. [Figure 5C] FIG. 1 is a schematic illustration of a typical bearing assembly used in a prior art axial impeller-based blood pump. [Figure 6] Figure 6A is a schematic illustration of a ventricular assist device at various stages in a motion cycle of an impeller of the ventricular assist device relative to a frame of the ventricular assist device, according to some applications of the present invention; Figure 6B is a schematic illustration of a ventricular assist device at various stages in a motion cycle of an impeller of the ventricular assist device relative to a frame of the ventricular assist device, according to some applications of the present invention; Figure 6C is a schematic illustration of an axial shaft receiving tube and distal tip portion of a ventricular assist device, according to some applications of the present invention; [Figure 7]1 is a schematic illustration of a motor unit of a ventricular assist device according to some applications of the present invention. [Figure 8] 8A and 8B are schematic illustrations of a motor unit of a ventricular assist device, according to some applications of the present invention; [Figure 9] 1 is a graph showing the variation in length of a drive cable of a ventricular assist device against a varying pressure gradient opposed by a blood pump impeller, as measured in experiments performed by the inventors of the present application. [Figure 10A] 1 is a schematic illustration of a drive cable for a ventricular assist device, in accordance with some applications of the present invention. [Figure 10B] 1 is a schematic illustration of a drive cable for a ventricular assist device, in accordance with some applications of the present invention. [Figure 10C] 1 is a schematic illustration of a drive cable for a ventricular assist device, in accordance with some applications of the present invention. [Figure 11A] 1 is a schematic illustration of interface components that form an interface between respective portions of a drive cable of a ventricular assist device, according to some applications of the present invention. [Figure 11B] 1 is a schematic illustration of interface components that form an interface between respective portions of a drive cable of a ventricular assist device, according to some applications of the present invention. [Figure 11C] 1 is a schematic illustration of an interface between a drive cable and an axial shaft of a ventricular assist device, in accordance with some applications of the present invention. [Figure 11D] 1 is a schematic illustration of an interface between a drive cable and an axial shaft of a ventricular assist device, in accordance with some applications of the present invention. [Figure 11E] 1 is a schematic illustration of an interface between a drive cable and an axial shaft of a ventricular assist device, in accordance with some applications of the present invention. [Figure 12]1 is a schematic illustration of a drive cable of a ventricular assist device including a friction-reducing element disposed about at least a portion of the drive cable, in accordance with some applications of the present invention. [Figure 13] 1A-1C are schematic illustrations of a procedure for purging a drive cable and / or radial bearing of a ventricular assist device, according to some applications of the present invention. [Figure 14A] FIG. 2 is a schematic illustration of a frame of a ventricular assist device according to some applications of the present invention, with a stator coupled to a proximal portion of the frame. [Figure 14B] FIG. 2 is a schematic illustration of a frame of a ventricular assist device according to some applications of the present invention, with a stator coupled to a proximal portion of the frame. [Figure 15A] 1 is a schematic illustration of a flattened profile of a frame of a ventricular assist device according to some applications of the present invention. [Figure 15B] FIG. 2 is a schematic illustration showing an enlarged view of the proximal end of a frame of a ventricular assist device according to some applications of the present invention. [Figure 15C] FIG. 1 is a schematic illustration of a frame of a ventricular assist device according to some applications of the present invention, with material defining curved protrusions coupled to the frame. [Figure 16A] 1 is a schematic illustration of a ventricular assist device including one or more blood pressure measuring tubes, in accordance with some applications of the present invention. [Figure 16B] 1 is a schematic illustration of a ventricular assist device including one or more blood pressure measuring tubes, in accordance with some applications of the present invention. [Figure 16C] 1 is a schematic illustration of a ventricular assist device including one or more blood pressure measuring tubes, in accordance with some applications of the present invention. [Figure 16D] 1 is a schematic illustration of a ventricular assist device including one or more blood pressure measuring tubes, in accordance with some applications of the present invention. [Figure 17A]FIG. 1 is a schematic illustration of a ventricular assist device including a pitot tube configured to measure blood flow through a tube of the device, in accordance with some applications of the present invention. [Figure 17B] FIG. 1 is a schematic illustration of a ventricular assist device including a pitot tube configured to measure blood flow through a tube of the device, in accordance with some applications of the present invention. [Figure 17C] FIG. 1 is a schematic illustration of a ventricular assist device including a pitot tube configured to measure blood flow through a tube of the device, in accordance with some applications of the present invention. [Figure 18] FIG. 1 is a schematic illustration of a ventricular assist device according to some applications of the present invention, the tip portion of the device being a radially expandable atraumatic distal tip portion. [Figure 19] 19A and 19B are schematic illustrations of a ventricular assist device, in accordance with some applications of the present invention, where a tip portion of the device is a radially expandable atraumatic distal tip portion; [Figure 20] 20A and 20B are schematic illustrations of a ventricular assist device, in accordance with some applications of the present invention, where a tip portion of the device is a radially expandable atraumatic distal tip portion; [Figure 21A] 1 is a schematic illustration of a distal tip portion of a ventricular assist device according to some applications of the present invention. [Figure 21B] 1 is a schematic illustration of a distal tip portion of a ventricular assist device according to some applications of the present invention. [Figure 21C] 1 is a schematic illustration of a distal tip portion of a ventricular assist device according to some applications of the present invention. [Figure 21D]1 is a schematic illustration of a distal tip portion of a ventricular assist device according to some applications of the present invention. [Figure 22] 22A and 22B are schematic illustrations of a distal tip portion of a ventricular assist device, according to some applications of the present invention, in an axially stiffened configuration and in a non-axially stiffened configuration. [Diagram 23] 23A and 23B are schematic illustrations of a distal tip portion of a ventricular assist device, according to some applications of the present invention, in a radially constrained configuration and in a radially unconstrained configuration, respectively. [Figure 24] 24A and 24B are schematic illustrations of a distal tip portion of a ventricular assist device, according to some applications of the present invention, in a radially constrained configuration and in a radially unconstrained configuration, respectively. [Diagram 25] FIG. 25A is a schematic illustration of a first portion and a second portion of a coupling element configured to facilitate radial contraction (e.g., during crimping) of an impeller according to some applications of the present invention; FIG. 25B is a schematic illustration of various stages of crimping of an impeller according to some applications of the present invention; and FIG. 25C is a schematic illustration of various stages of crimping of an impeller according to some applications of the present invention. [Figure 26] FIG. 13 is a schematic illustration of a stopper configured to prevent distal advancement of an impeller of a ventricular assist device during withdrawal of the ventricular assist device from a subject's body, according to some applications of the present invention. [Figure 27A] FIG. 1 is a schematic illustration of a ventricular assist device according to some applications of the present invention, the device including a valve to prevent backflow of blood, for example, in the event that the impeller of the ventricular assist device fails. [Figure 27B]FIG. 1 is a schematic illustration of a ventricular assist device according to some applications of the present invention, the device including a valve to prevent backflow of blood, for example, in the event that the impeller of the ventricular assist device fails. [Figure 28A] FIG. 1 is a schematic illustration of a ventricular assist device according to some applications of the present invention, the device including a safety balloon to prevent backflow of blood, for example, in the event that the impeller of the ventricular assist device fails. [Figure 28B] FIG. 1 is a schematic illustration of a ventricular assist device according to some applications of the present invention, the device including a safety balloon to prevent backflow of blood, for example, in the event that the impeller of the ventricular assist device fails. [Figure 28C] FIG. 1 is a schematic illustration of a ventricular assist device according to some applications of the present invention, the device including a safety balloon to prevent backflow of blood, for example, in the event that the impeller of the ventricular assist device fails. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0153] Reference is now made to Figures 1A and 1B, which are schematic illustrations of a ventricular assist device 20 according to some applications of the present invention, with a distal end of the ventricular assist device 20 disposed in a left ventricle 22 of a subject. The ventricular assist device includes a tube 24 that traverses an aortic valve 26 of the subject, with a proximal end 28 of the tube disposed in an aorta 30 of the subject, and a distal end 32 of the tube disposed in the left ventricle 22. The tube 24 (which may be referred to herein as a "blood pressure pump tube") is typically an elongated tube, with the axial length of the tube typically being substantially greater than its diameter. The scope of the present invention includes the use of the apparatus and methods described herein in anatomical locations other than the left ventricle and aorta. Thus, the ventricular assist device and / or portions thereof may be referred to herein (in the specification and claims) as a blood pump.

[0154] As shown in FIG. 1B (FIG. 1B shows a step in the deployment of a ventricular assist device in the left ventricle), typically, the distal end of the ventricular assist device is guided over the guidewire 10 into the left ventricle. During insertion of the distal end of the device into the left ventricle, a delivery catheter 143 is disposed over the distal end of the device. Once the distal end of the device is disposed in the left ventricle, the delivery catheter is typically retracted into the aorta and the guidewire is withdrawn from the subject's body. Retraction of the delivery catheter typically causes the self-expandable component at the distal end of the device to assume a radially unconstrained configuration, as described in more detail below. Typically, the ventricular assist device is inserted into the subject's body to provide acute therapy to the subject. For some applications, to withdraw the left ventricular device from the subject's body at the end of therapy, a delivery catheter is advanced over the distal end of the device, which causes the self-expandable component at 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-expandable components at the distal end of the device to assume a radially constrained configuration.

[0155] Reference is also made to Figures 2A, 2B, and 2C, which are schematic illustrations of the blood pump portion 27 of the ventricular assist device 20 according to some applications of the present invention. Typically, an impeller 50 is disposed in the distal portion 102 of the tube 24 and is configured to rotate to pump blood from the left ventricle into the aorta. 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, a 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.

[0156] For some applications, the control console 21 typically includes a computer processor 25 (shown in FIG. 1A), and the control console 21 is rotatably The computer processor 25 drives the impeller. For example, the computer processor can control a motor 74 (shown in FIG. 7), which is disposed in the motor unit 23, and which drives the impeller to rotate via a drive cable 130 (also shown in FIG. 7). For some applications, the computer processor is configured to detect physiological parameters of the subject (e.g., left ventricular pressure, cardiac afterload, etc.) and to control the rotation of the impeller in response thereto, as described in more detail below. Typically, the operations described herein performed by the computer processor transform the physical state of the memory (which is an actual physical item in communication with the computer processor) to have different magnetic polarities, charges, etc., depending on the technology of the memory being used. The computer processor 25 is typically a hardware device programmed with computer program instructions to create a special-purpose computer. For example, when programmed to implement the techniques described herein, the computer processor 25 typically acts as a special-purpose ventricular assist computer processor.

[0157] For some applications, the purging system 29 drives a fluid (e.g., a glucose solution) through a portion of the ventricular assist device 20, for example, to cool a portion of the device and / or to flush debris from a portion of the device. The purging system 29 is described in further detail below.

[0158] Typically, along the distal portion 102 of the tube 24, a frame 34 is disposed within the tube. The frame is typically made of a shape memory alloy, such as Nitinol. For some applications, the shape memory alloy of the frame is shape set such that the frame (and thereby the tube) assumes a generally circular, elliptical, or polygonal cross-sectional shape in the absence of any force being applied to the tube. 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. Typically, during operation of the ventricular assist device, the distal portion of the tube is configured to be placed within the subject's body such that the distal portion of the tube is at least partially disposed within the left ventricle.

[0159] For some applications (not shown), during operation of the ventricular assist device, the distal portion of the tube is at least partially disposed within the native aortic valve, and the frame is configured to hold the aortic valve open by assuming its generally circular, elliptical, or polygonal cross-sectional shape. For some applications, the tube 24 is sized such that the shape memory alloy of the frame 34 prevents it from fully assuming its shape-set dimensions. In this manner, the frame is "pretensioned" such that the frame will not be radially compressed when the aortic valve applies a radial compressive force to the tube and frame because the frame is already maintained in a partial radially restrained state by the tube. For some applications, the frame includes a plurality of rigid struts 111 that are disposed parallel to one another and to a longitudinal axis of the frame. The rigid struts are configured such that at least a portion 110 of the frame (along which the struts are disposed) maintains a substantially straight longitudinal axis even when subjected to anatomical forces within the left ventricle and / or aortic valve. Typically, the frame 34 changes from a radially constrained configuration (the frame is typically disposed in a radially constrained configuration during introduction of the frame into the subject's body) to a radially unconstrained configuration (the frame is typically disposed in a radially unconstrained configuration during operation of the ventricular assist device). The rigid struts are configured such that when the rigid struts are moved, their length does not change.

[0160] For some applications, along a proximal portion 106 of the tube 24, a frame is not disposed within the tube, and thus the tube is not supported open by the frame 34. The tube 24 is typically made of a blood-impermeable collapsible material. For example, the tube 24 can include polyurethane, polyester, and / or silicone. Typically, the proximal portion of the tube is configured to be installed such that it is disposed at least partially within the subject's ascending aorta. For some applications, the proximal portion of the tube traverses the subject's aortic valve and passes from the subject's left ventricle into the subject's ascending aorta, as shown in FIG. 1B. As described above, the tube typically defines one or more blood inlet openings 108 at a 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. Typically, the tube defines a plurality of blood outlet openings 109, for example, between two and eight blood outlet openings (e.g., between two and four blood outlet openings). During operation of the impeller, the pressure of blood flow through the tube typically maintains the proximal portion of the tube open. For some applications, for example, in the event of an impeller failure, the proximal portion of the tube is configured to collapse inward in response to pressure outside the proximal portion of the tube exceeding pressure inside the proximal portion of the tube. In this manner, the proximal portion of the tube acts as a safety valve and prevents retrograde blood flow from the aorta into the left ventricle.

[0161] For some applications, computer processor 25 of control console 21 (shown in FIG. 1A ) is configured to control the pumping of the blood pump (e.g., by controlling the rotation of the impeller) such that the blood pressure generated by the pump in tube 24 exceeds the subject's systolic aortic pressure during systole, but is less than the subject's diastolic aortic pressure during diastole. During systole, proximal portion 106 of tube 24 is held open because the blood pressure in the tube exceeds the aortic pressure exerted on the tube from outside the tube. During diastole, proximal portion 106 of tube 24 closes because the aortic pressure exerted on the tube from outside the tube exceeds the blood pressure in the tube. In this manner, the impeller pumps blood from the left ventricle to the aorta in a pulsatile manner (i.e., by pumping blood from the left ventricle to the aorta only during diastole). For some applications, the computer processor is configured to measure the subject's aortic pressure, left ventricular pressure, and / or flow through tube 24, for example, using techniques such as those described below with reference to FIG. 9, FIG. 16A-FIG. 16D, and / or FIG. 17. For some such applications, based on the measured aortic pressure, left ventricular pressure, and / or flow, the computer processor controls the rotation of the impeller in the manner described above. Alternatively, the computer processor controls the rotation of the impeller based on the measured aortic pressure, left ventricular pressure, and / or flow in a manner different from that described above. For example, the computer processor may be configured to vary the rotational speed of the impeller based on the measured aortic pressure, left ventricular pressure, and / or flow, but in a manner that results in the impeller pumping blood from the left ventricle to the aorta in a non-pulsatile, continuous manner.

[0162] Typically, pumping blood by the impeller increases aortic pressure and decreases left ventricular pressure. When the flow through the tube 24 reaches a critical value (above which the aortic pressure is higher than the left ventricular pressure even during ventricular systole (hereafter "systole")), the aortic valve remains closed around the outside of the tube 24 throughout the cardiac cycle and flow from the ventricle to the aorta occurs exclusively through the tube. Typically, above this point of decoupling aortic pressure from ventricular pressure, the left ventricle no longer performs net external work (defined as volume change times pressure change) since it is not moving any volume. In this mode, oxygen consumption by the left ventricle depends on the cyclic pressure generation against the closed aortic valve, wall tension resulting from the size of the left ventricle, wall thickness, and baseline metabolic demand (including calcium cycling). Below this critical point of impeller activity, the aortic valve is typically at least partially open during systole, and left ventricular outflow occurs both between the outside of the tube and the aortic valve (due to left ventricular contraction) and through the tube (due to impeller rotation and pumping). For a given impeller RPM, the larger the cross-sectional area of ​​the sleeve, the greater the flow through the tube will typically be. At the same time, the larger the cross-sectional area of ​​the tube, the more space it takes up in the left ventricular outflow tract, and the smaller the remaining outflow area, resulting in the left ventricle having to overcome a higher outflow resistance to pump around the outside of the tube.

[0163] Thus, typically, there is a trade-off between the efficiency of the impeller in assisting the left ventricle (which favorably increases with tube diameter) and the residual resistance to outflow around the outside of the tube 24 (which unfavorably increases with tube diameter). The higher the flow through the tube provided by the impeller (for a given tube diameter), the less of an effect of the reduced cross-sectional outflow area on the effective outflow resistance may be an issue, since the remaining cross-sectional area may be adequate for the remaining small stroke volume that the ventricle must expel, i.e., the reduced residual outflow tract area may not provide too much resistance to outflow. Conversely, however, if a fixed tube diameter is selected, as the flow through the tube decreases, the effective resistance to outflow increases, since now a larger proportion of the left ventricular stroke volume must pass through the residual outflow tract area around the tube. Thus, for some applications, the left ventricular outflow resistance is configured to automatically adjust to compensate for changes in blood flow through the tube caused by the impeller. For example, the tube may be made of a flexible material whose flexibility is such that a reduction in flow through the tube and subsequent drop in expansion pressure results in a reduction in sleeve diameter, thereby increasing the outflow area available to the left ventricle.Typically, the material properties of the flexible material are defined such that (a) maximum tube expansion is reached at or near the point when the luminal pressure generated by the pump flow exceeds the aortic pressure (regardless of the point in the cardiac cycle), and thus remains above the left ventricular pressure throughout the cardiac cycle, and (b) a fully collapsed state of the tube is reached when the flow through the tube generated by the impeller becomes zero.

[0164] 2B, for some applications, a plurality of elongated commissure elements 107 extend along at least some of the proximal portion 106 of the tube 24. As explained above, for some applications, the computer processor 25 is configured to drive the impeller 50 to pump blood from the left ventricle to the aorta in a pulsatile manner. For some applications, the commissure elements are configured to facilitate opening and closing of the proximal portion of the tube in a manner similar to the opening and closing of the leaflets of a natural valve, such that respective portions of the circumference of the tube form cusps that contact one another when the tube is closed. For some applications, the ventricular assist device includes three elongated commissure elements, and the proximal portion of the tube 24 is configured to close in a manner similar to that of a tricuspid valve. (FIG. 2B illustrates such an embodiment, but with one of the commissure elements hidden from view.) For some applications (not shown), the ventricular assist device includes two elongated commissure elements, and the proximal portion of the tube 24 is configured to close in a manner similar to that of a bicuspid valve. For some applications, the proximal portion of the tube 24 is placed across the subject's aortic valve, and the commissure elements are rotationally aligned with the commissures of the native valve. In this manner, the artificial cusps of the proximal portion of the tube are aligned with the native aortic valve cusps.

[0165] 2A-2C, for some applications, the frame 34 is shaped such that it defines a proximal conical portion 36, a central cylindrical portion 38, and a distal conical portion 40. Typically, the proximal conical portion is such that the narrow end of the cone is proximal to the wide end of the cone. More typically, the distal conical portion is such that the narrow end of the cone is distal to the wide end of the cone. For some applications, the tube 24 extends to the end of the cylindrical portion 38 such that the distal end of the tube defines a single axially facing blood inlet opening 108, as shown in FIGS. 2A and 2B. Alternatively, the tube 24 extends to the end of the distal conical portion 40 such that the tube defines one or more lateral blood inlet openings, as shown in FIG. 2C. For such applications, the tube typically defines from two to four lateral blood inlet openings.

[0166] Typically, the tube 24 includes a conical proximal portion 42 and a cylindrical central portion 44. The proximal conical portion typically has a narrow end of the cone proximal to a wider end of the cone. As explained above, for some applications, the tube extends to the end of the distal conical portion 40 of the frame 34. For such applications, the tube typically defines a distal conical portion 46 with a narrow end of the cone distal to the wider end of the cone, as shown in FIG. 2C. For some applications (not shown), the diameter of the tube 24 varies along the length of the central portion of the tube, such that the central portion of the tube has a frusto-conical shape. For example, the central portion of the tube can be wider from its proximal end to its distal end, or narrower from its proximal end to its distal end. For some applications, at its proximal end, the central portion of the tube has a diameter between 5 mm and 7 mm, and at its distal end, the central portion of the tube has a diameter between 8 mm and 12 mm.

[0167] Reference is now made to Figures 3A-3C, which are schematic illustrations of an impeller 50 according to some applications of the present invention. Typically, the impeller includes at least one outer helical elongated element 52 that is wound around a central axial spring 54 such that the helix defined by the helical elongated element is coaxial with the central axial spring. Typically, the impeller includes two or more helical elongated elements (e.g., three helical elongated elements as shown in Figures 3A-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 of the helical elongated elements and the central axial spring supports a film 56 of a material (e.g., a polymer, e.g., polyurethane and / or silicone) between them. For illustrative purposes, the impeller is shown without its material in Figure 3A. Figures 3B and 3C show respective views of the impeller with material supported between the helical elongated element and a spring.

[0168] Each of the helical elongate elements defines a respective impeller blade with a film extending from the helical elongate element to the spring, with the helical elongate element defining the outer edge of the blade and the axial spring defining the axis of the impeller. Typically, the film of material extends along and covers the spring. For some applications, a suture 53 (e.g., polyester suture as shown in Figures 3B and 3C) is wrapped around the helical elongate element, as described, for example, in US Patent Application Publication No. 2016 / 0022890 to Schwammenthal, which is incorporated herein by reference. Typically, the suture is configured to promote bonding between the film of material (which is typically a polymer, such as polyurethane or silicone) and the helical elongate element (which is typically a shape memory alloy, such as 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 promote bonding between the film of material (which is typically a polymer, such as polyurethane or silicone) and the spring (which is typically a shape memory alloy, such as Nitinol).

[0169] Typically, the proximal ends of the spring 54 and the helical elongate element 52 extend from an impeller proximal bushing (i.e., sleeve bearing) 64 such that the proximal ends of the spring 54 and the helical elongate element 52 are disposed at similar radial distances from the longitudinal axis of the impeller. Similarly, typically, the distal ends of the spring 54 and the helical elongate element 52 extend from an impeller distal bushing 58 such that the distal ends of the spring 54 and the helical elongate element 52 are disposed at similar radial distances from the longitudinal axis of the impeller. Typically, the spring 54 and the impeller proximal bushing 64 and distal bushing 58 define a lumen 62 therethrough.

[0170] Reference is now made to Figure 4, which is a schematic illustration of an impeller 50 disposed inside the frame 34 of the ventricular assist device 20, according to some applications of the present invention. As shown, there is typically a gap G between the outer edge of the impeller 50 and the inner surface of the frame 34, even where the span of the impeller is at its maximum. For some applications, it is desirable that the gap between the outer edge of the impeller blades and the inner surface of the frame 34 be relatively small so that the impeller efficiently pumps blood from the subject's left ventricle into the subject's aorta. However, it is also desirable that a gap between the outer edge of the impeller blades and the inner surface of the frame 34 can be maintained, for example, to reduce the risk of hemolysis.

[0171] For some applications, the gap G between the outer edge of the impeller and the inner surface of the frame 34 where the span of the impeller is at its maximum is greater than 0.05 mm (e.g., greater than 0.1 mm) and / or less than 1 mm (e.g., less than 0.4 mm), such as between 0.05 mm and 1 mm, or between 0.1 mm and 0.4 mm. For some applications, the outer diameter of the impeller where the outer diameter of the impeller is at its maximum is greater than 6 mm (e.g., greater than 6.5 mm) and / or less than 8 mm (e.g., less than 7 mm), such as between 6 and 8 mm, or between 6.5 and 7 mm. For some applications, the inner diameter of the frame 34 is greater than 6.5 mm (e.g., greater than 7 mm) and / or less than 8.5 mm (e.g., less than 7.5 mm), such as between 6 and 8 mm. For example, it is 6.5 to 8.5 mm or 7 to 7.5 mm.

[0172] Typically, an axial shaft 92 passes through the axis of the impeller 50 via the impeller lumen 62. Typically, the impeller proximal bushing 64 is coupled to the shaft such that the axial position of the proximal bushing relative to the shaft is fixed, and the impeller distal bushing 58 is slidable relative to the shaft. The axial shaft itself is radially stabilized via proximal and distal radial bearings 116 and 118 defined by the frame 34. And, by passing through the lumen 62 defined by the impeller, the axial shaft radially stabilizes the impeller relative to the inner surface of the frame 34 such that even a relatively small gap (e.g., as described above) between the outer edges of the impeller blades and the inner surface of the frame 34 is maintained during rotation of the impeller.

[0173] 3A-3C, for some applications, the impeller includes a plurality of elongated elements 67 extending radially from the central axial spring 54 to the outer helical elongated element 52. The elongated elements are typically flexible, but substantially non-stretchable along an axis defined by the elongated elements. More typically, each of the elongated elements is configured to exert no force on the helical elongated element when no force is acting on the impeller (the force causing the helical elongated element to move radially outward such that the separation between the helical elongated element and the central axial spring is greater than the length of the elongated element (if the elongated element is not present)). For example, the elongated elements can include strings (e.g., polyester and / or another polymer or natural material containing fibers, etc.) and / or wires (e.g., Nitinol wires and / or wires made of different alloys or metals, etc.).

[0174] For some applications, the elongated elements 67 maintain the helical elongated elements (which define the outer edges of the impeller blades) within a given distance relative to the central axial spring. In this manner, the elongated elements are configured to prevent the outer edges of the impeller from being pushed radially outward due to forces exerted on the impeller during impeller rotation. The elongated elements are thereby configured to maintain a gap between the outer edges of the impeller blades and the inner surface of the frame 34 during impeller rotation. Typically, two or more (e.g., three or more) and / or fewer than eight (e.g., fewer than four) elongated elements 67 are used in the impeller, with each of the elongated elements typically being doubled (i.e., extending radially from the central axial spring 54 to the outer helical elongated element 52 and then back from the helical elongated element to the central axial spring). For some applications, multiple elongate elements (each of which extends from the spring to a respective helical elongate element and back to the spring) are formed from a single piece of string or from a single wire, as described in more detail below.

[0175] For some applications, the impeller is manufactured in the following manner: the proximal bushing 64, the distal bushing 58, and the helical elongate element 52 are cut from a tube of shape memory material, such as Nitinol. The cutting of the tube and the shape setting of the shape memory material may be performed using techniques generally similar to those described, for example, in U.S. Patent Application Publication No. 2016 / 0022890 to Schwammenthal. The spring is typically implemented such that a helical elongated element is defined by a shape memory material using a spring 54. Typically, the spring is inserted into the cut and shape 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 configured to be inserted into the cut and shape set tube while the spring is in an axially compressed state, and the spring is held in position relative to the tube by exerting a radial force on the proximal and distal bushings. Alternatively or additionally, a portion of the spring is welded to the proximal and distal bushings. For some applications, the spring is cut from a tube of a shape memory material, such as Nitinol. For some such applications, the spring is configured such that when the spring is disposed in a radially unconstrained configuration (as the spring is typically disposed in during operation of the impeller), there is substantially no gap between the windings of the spring and adjacent windings.

[0176] For some applications, at this stage, the elongate element 67 is placed to extend between the spring and one or more of the helical elongate elements, as described above, for example, in the following manner: A mandrel (e.g., a polyetheretherketone (PEEK) and / or polytetrafluoroethylene (PTFE) mandrel) is inserted through a lumen defined by the spring and the bushing. The string or wire is then threaded (a) from the mandrel to a first one of the helical elongate elements, (b) from the first one of the helical elongate elements back to the mandrel, (c) around the mandrel and to a second one of the helical elongate elements, (d) from the second one of the helical elongate elements back to the mandrel, etc. Once the string or wire has been threaded from the mandrel to each of the helical elongate elements and back again, the ends of the string or wire are connected to one another, for example, by tying them together. For some applications, a suture 53 (e.g., a polyester suture) is wound around the helical elongate element to promote bonding between the film of material (which is typically a polymer, such as polyurethane or silicone) and the helical elongate element (which is typically a shape memory alloy, such as Nitinol) at a subsequent stage of manufacture of the impeller. For some applications, a suture (e.g., a polyester suture (not shown)) is wound around the spring 54. Typically, the suture is configured to promote bonding between the film of material (which is typically a polymer, such as polyurethane or silicone) and the spring (which is typically a shape memory alloy, such as Nitinol) at a subsequent stage of manufacture of the impeller.

[0177] Typically, at this stage, a structure 59 as shown in FIG. 3A has been assembled. The structure includes cut and shape-set tubes defining proximal and distal bushings and a helical elongate element, springs, and optionally elongate elements and sutures. This structure is dipped into a material defining a film 56. It is noted that for some applications, the assembled structure is dipped into the material with a mandrel disposed through the lumen defined by the springs and bushings, although the mandrel is not shown in FIG. 3A. Typically, the material from which the film is made is silicone (and / or similar polymers), and the assembled structure is dipped into the material while the material is in an uncured liquid state. The material is then cured, for example by being left to dry, so that the material solidifies. Once the material is dry, the mandrel is typically When the needle is in the position shown in FIG.

[0178] The result of the process described above is typically that there is a continuous film of material extending into the springs between each of the helical elongate elements and along the length of the springs to define a tube within which the springs are embedded. The portions of the film extending from each of the helical elongate elements into the springs define the impeller blades. For applications in which the impeller includes elongate elements 67, the elongate elements will typically be embedded within these portions of the film.

[0179] Typically, the impeller 50 is inserted transcatheterically into the left ventricle with the impeller 50 in a radially constrained configuration. In the radially constrained configuration, both the helical elongate element 52 and the central axial spring 54 are axially elongated and radially constrained. Typically, the film of material (e.g., silicone) 56 changes shape to match the shape changes of the helical elongate element and the axial support spring, both of which support the film of material. Typically, using a spring to support the inner edge of the film allows the film to change shape without tearing or collapsing due to the spring providing a large surface area to which the inner edge of the film bonds. For some applications, using a spring to support the inner edge of the film reduces the diameter at which the impeller can be radially constrained, for example, compared to if a rigid shaft were used to support the inner edge of the film. This is because the diameter of the spring itself can be reduced by elongating the spring axially.

[0180] As explained above, for some applications, the proximal bushing 64 of the impeller 50 is coupled to the axial shaft 92 such that the axial position of the proximal bushing relative to the shaft is fixed, and the distal bushing 58 of the impeller is slidable relative to the shaft. For some applications, when the impeller is radially constrained for purposes of inserting the impeller into a cardiac ventricle or for purposes of withdrawing the impeller from a subject's body, the impeller is axially elongated by the distal bushing sliding distally along the axial shaft.

[0181] Following release inside the subject's body, the impeller assumes its radially unconstrained configuration (in which the impeller is typically disposed during impeller operation) as shown in Figures 3A-3C. Typically, the pitch of each of the helical elongated elements 52 is greater than 1 mm (e.g., greater than 6 mm) and / or less than 20 mm (e.g., less than 10 mm) when the impeller 50 is in a radially unconstrained configuration (e.g., inside the subject's ventricle). Typically, other things being equal, the greater the pitch of the helical elongated elements (and thus the impeller blades), the greater the blood flow generated by the impeller. Thus, as described, the pitch of the helical elongated elements 52 is typically greater than 1 mm (e.g., greater than 6 mm) when the impeller 50 is in a radially unconstrained configuration. On the other hand, it is typically desired that the impeller occlude the backflow of blood into the subject's left ventricle. Other things being equal, it is typically the case that the smaller the pitch of the helical elongated element (and thus the impeller blades), the greater the occlusion provided by the impeller. Thus, As described, when the impeller 50 is in a radially unconstrained configuration, the pitch of the helical elongated element 52 is typically less than 20 mm (e.g., less than 10 mm).

[0182] For some applications, the pitch of the helical elongate element (and thus the impeller blades) varies along the length of the helical elongate element, at least when the impeller is in a radially unconstrained configuration. Typically, for such applications, the pitch increases from the distal end of the impeller (i.e., the end inserted further into the subject's body and located upstream relative to the direction of antegrade blood flow) to the proximal end of the impeller (i.e., the end located downstream relative to the direction of antegrade blood flow), such that the pitch increases in the direction of blood flow. Typically, blood flow velocity increases along the impeller in the direction of blood flow. Thus, the pitch is increased along the direction of blood flow to further accelerate the blood.

[0183] It is noted that for illustrative purposes, in some of the figures, impeller 50 is shown without including all of the features of the impeller as shown and described with reference to Figures 3A-3C. For example, some of the figures show an impeller that does not include suture 53 and / or elongated element 67. The scope of the present application includes the use of an impeller having any of the features shown and described with reference to Figures 3A-3C in combination with any of the devices and methods described herein.

[0184] Reference is now made to Figures 5A and 5B, which are schematic illustrations of the impeller 50 and frame 34 of the ventricular assist device 20 in their radially unconstrained and radially constrained states, respectively, according to some applications of the present invention. The impeller and frame are typically disposed in a radially unconstrained state during transcatheter insertion of the impeller and frame into the subject's body, and during operation of the impeller inside the subject's left ventricle. As explained above, typically the tube 24 extends from at least a distal portion of the frame and proximally therefrom. However, for illustrative purposes, the frame and impeller are shown in Figures 5A-5B without the tube 24 present. As shown in Figure 5B, the frame and impeller are typically maintained in a radially constrained configuration by a delivery catheter 143.

[0185] Reference is also made to FIG. 5C, which illustrates a typical bearing assembly used in a prior art axial impeller-based blood pump. FIG. 5C is illustrated for the purpose of serving as a point of reference for some of the applications of the invention described herein. As illustrated in FIG. 5C, the bearing assembly typically includes a radial bearing (represented by an oval 200) and a thrust bearing (represented by a circle 202). The radial bearing is configured to reduce radial motion of the impeller by maintaining the axis of the impeller at a given radial position. In response to the impeller pumping blood in a first direction, the forces acting on the impeller typically push the impeller to move in a direction opposite the first direction. The purpose of the thrust bearing is to counter such motion of the impeller and maintain the axial position of the impeller. In the example shown in FIG. 5C, in response to the impeller pumping blood in the direction of arrow 204, the impeller becomes pushed in the direction of arrow 206, and the thrust bearing opposes this motion. Typically, the bearings experience a significant amount of heating and wear due to the frictional forces exerted on them. Because the frictional forces exerted on thrust bearings are typically less than those of radial bearings, Due to the fact that they are spread across opposing surfaces having a large contact area therebetween, thrust bearings are typically exposed to significant heating and wear.

[0186] As described above, the axial shaft 92 typically passes through the axis of the impeller 50 via the impeller lumen 62. Typically, the impeller proximal bushing 64 is coupled to the shaft via a coupling element 65 such that the axial position of the proximal bushing relative to the shaft is fixed, and the impeller distal bushing 58 is slidable relative to the shaft. The axial shaft itself is radially stabilized via proximal and distal radial bearings 116 and 118 defined by the frame 34. And, by passing through the lumen 62 defined by the impeller, the axial shaft radially stabilizes the impeller relative to the inner surface of the frame 34, so that even a relatively small gap (e.g., a gap as described above) between the outer edges of the impeller blades and the inner surface of the frame 34 is maintained during rotation of the impeller, as described above. For some applications, the axial shaft 92 is made from stainless steel and the proximal and / or distal bearings 116, 118 are made from hardened steel. Typically, the impeller's distal bushing 58 is configured to slide distally along the axial shaft when the impeller and frame are crimped (i.e., radially constrained) for purposes of inserting the impeller and frame into the subject's body, causing the impeller to elongate axially, as described above. More generally, the impeller changes from its radially constrained to its radially unconstrained configuration by the distal bushing sliding over the axial shaft, and vice versa.

[0187] Typically, the impeller itself is not disposed directly in any radial or thrust bearings. Rather, bearings 116 and 118 act as radial bearings for the axial shaft. For some applications, there are no thrust bearings in contact with any surfaces that may generate thrust forces during rotation of the impeller because, as described in more detail below, the impeller is configured to move axially within frame 34 while it rotates. Typically, pump portion 27 (and, more generally, ventricular assist device 20) is configured to be disposed within a subject's body and does not include any thrust bearings configured to counter the thrust generated by rotation of the impeller. For some applications, one or more thrust bearings are disposed outside the subject's body (e.g., in the motor unit 23 shown in Figs. 1A, 7, and 8A-8B), and opposition to the thrust generated by the rotation of the impeller is provided solely by the one or more thrust bearings disposed outside the subject's body. For some applications, the mechanical and / or magnetic elements are configured to maintain the impeller within a given range of axial positions. For example, a magnet (e.g., magnet 82 described below with reference to Fig. 7) disposed at a proximal end of the drive cable (e.g., outside the subject's body) may be configured to impart axial motion to the impeller and to maintain the impeller within a given range of axial positions.

[0188] For some alternative applications of the present invention, the ventricular assist device includes an impeller that is not configured to move in an axial forward and backward motion. For some such applications (not shown), a thrust bearing is used to maintain the axial position of the impeller, and the thrust bearing is disposed within a portion of the ventricular assist device proximal to the impeller such that the thrust bearing does not contact the subject's blood. For example, the thrust bearing may be disposed in an outer tube in which the drive shaft of the impeller is disposed. Alternatively or additionally, the thrust bearing may be disposed outside the subject's body. For some such applications, since the thrust bearing is disposed outside the subject's body, the size of the thrust bearing is not constrained by the need to be deployed in a small anatomical location. Thus, in such cases, the contact area between the two opposing surfaces of the thrust bearing is typically greater than 20 square mm. For some applications (not shown), the thrust bearing is disposed distal to the impeller and in contact with the subject's blood, such that the thrust bearing is cooled by the subject's blood.

[0189] Reference is now made to Figures 6A and 6B, which are schematic illustrations of the ventricular assist device 20 at different stages of a motion cycle of the ventricular assist device's impeller 50 relative to the ventricular assist device's frame 34, according to some applications of the present invention. For some applications, while the impeller rotates to pump blood through the tube 24, the axial shaft 92 (to which the impeller is fixed) is driven to move the impeller axially back and forth within the frame 34 by the axial shaft moving in an axial forward and backward motion, as described in more detail below with reference to Figure 7. Alternatively or additionally, the impeller and axial shaft are configured to move axially back and forth within the frame 34 in response to forces acting on the impeller and without the axial shaft having to be actively driven to move in an axial forward and backward motion, e.g., as described in more detail below with reference to Figure 9.

[0190] For some applications, by moving in an advancing and retreating motion, the portion of the axial shaft in contact with the proximal and distal bearings 116, 118 is constantly changing. For some such applications, the frictional forces exerted on the axial shaft by the bearings are thus spread over a larger area of ​​the axial shaft than would be the case if the axial shaft were not moving relative to the bearings, thereby reducing wear on the axial shaft, all other things being equal. Alternatively or additionally, by moving in an advancing and retreating motion relative to the bearings, the axial shaft cleans the interface between the axial shaft and the bearings from any residue, such as blood residue.

[0191] For some applications, when the frame 34 and impeller 50 are in their radially unconstrained 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 bearing 116 and the distal bearing 118 are each 2-4 mm in length. More typically, the impeller and the axial shaft are configured to move axially within the frame in a forward and backward motion at least along the length of each of the proximal and distal bearings, or at least twice the length of each of the bearings. Thus, during forward and backward axial movement of the axial shaft, the axial shaft is wiped clean on either side of each of the bearings.

[0192] Reference is again made to Figures 6A and 6B, and also to Figure 6C, which is a schematic illustration of an axial shaft receiving tube 126 and distal tip portion 120 of a ventricular assist device 20, in accordance with some applications of the present invention. For some applications, the distal tip portion of the ventricular assist device is configured to be soft, such that even when the distal tip portion contacts tissue (e.g., tissue of the left ventricle), the distal tip portion is configured not to injure the subject's tissue. For example, the distal tip portion may be made of silicone. For some applications, the distal tip portion may be configured to have a loop therethrough, such that the distal tip portion is configured to be flexible and not injure the subject's tissue even when the distal tip portion contacts tissue (e.g., tissue of the left ventricle). ... The distal tip portion 120 defines a lumen 122. For some such applications, during insertion of the ventricular assist device into the left ventricle, the guidewire 10 (FIG. 1B) is first inserted into the left ventricle, for example, according to known techniques. The distal tip portion of the ventricular assist device is then guided into the left ventricle by advancing the distal tip portion over the guidewire with the guidewire disposed inside the lumen 122. For some applications, a hemostatic valve 152 is disposed at the distal end of the lumen 122 of the distal tip portion 120 such that the distal tip portion is sealed after the guidewire is retracted from the lumen 122. Typically, during insertion of the ventricular assist device into the subject's ventricle, a delivery catheter 143 is placed over the impeller 50 and frame 34 to maintain the impeller and frame in their radially constrained configuration. For some applications, distal tip portion 120 extends distally from the delivery catheter during insertion of the delivery catheter into the subject's ventricle. For some applications, at a proximal end of the distal tip portion, the distal tip portion has a flared portion 124 that acts as a stop and prevents the delivery catheter from advancing beyond the flared portion.

[0193] For some applications, the axial shaft receiving tube 126 extends proximally from the distal tip portion 120. As explained above, typically, the axial shaft undergoes axial forward and backward movement during operation of the impeller 50. The shaft receiving tube 126 defines a lumen 127 configured to receive the axial shaft when the axial shaft extends beyond the distal bearing 118. For some applications, the shaft receiving tube defines a stopper 128 at its distal end configured to prevent advancement of the axial shaft beyond the stopper. For some applications, the stopper includes a rigid component inserted (e.g., embedded) into the distal end of the shaft receiving tube. Alternatively, the stopper includes a shoulder between the lumen 127 of the axial shaft receiving tube and the lumen 122 of the tip portion 120. Typically, such a shoulder is present because lumen 122 of tip section 120 is narrower than lumen 127. (This is because lumen 127 is typically configured to accommodate the axial shaft, while lumen 122 is configured to accommodate guidewire 10, which is itself configured to accommodate guidewire 10 within its inner lumen 132 (shown in FIGS. 10B and 10C), making the axial shaft typically wider than guidewire 10.) Typically, during normal operation of the impeller, the axial shaft does not extend all the way to stopper 128, even when drive cable 130 (shown in FIG. 7) is maximally extended. However, stopper 128 is configured to prevent the axial shaft from protruding into the tip section when a delivery catheter is advanced over impeller 50 and frame 34 during retraction of ventricular assist device 20 from the subject's ventricle. In some cases, during advancement of the delivery catheter over the frame and impeller, the drive cable is at risk of snapping.In such a case, the axial shaft could protrude into the tip portion if the stopper 128 was not present. The stopper 128 prevents this from happening even if the drive cable snaps.

[0194] Typically, during operation of the ventricular assist device and throughout the impeller's forward and backward axial motion cycle, the impeller is disposed relatively very proximal to the distal tip portion. For example, the distance of the impeller to the distal tip portion can be within the most distal 50 percent, e.g., the most distal 30 percent (or the most distal 20 percent) of the tube 24 throughout the impeller's forward and backward axial motion cycle.

[0195] For some applications (not shown), a portion of the frame 34 extends into a proximal portion of the distal tip portion 120. The portion of the frame is configured to cause the proximal portion of the tip to experience radial expansion when deployed into the subject's left ventricle by shape-setting the portion of the frame into a radially expanded configuration. For some applications, the entire tip portion is made from a material having a uniform stiffness, but the portion of the frame 34 that extends into the proximal portion of the tip portion imparts rigidity to the proximal portion of the tip portion such that the proximal portion of the tip portion has greater rigidity than the distal portion of the tip portion.

[0196] For some applications, the tip portion has a different configuration than that shown in FIG. 6C, e.g., as described in more detail below with reference to FIGs. 18-24B. For some applications, the distal tip portion combines certain features described in connection with FIG. 6C with features described below with reference to FIGs. 13 and 18-24B, e.g., as described below with reference to FIGs. 18-24B. For example, the internal structure of the tip portion and the proximal extension of the axial shaft receiving tube 126 from the tip portion can be as described with reference to FIGs. 6 and / or 13, and the external shape of the tip portion can be as described with reference to any one of FIGs. 18-24B.

[0197] Reference is now made to FIG. 7, which is a schematic illustration of an exploded view of the motor unit 23 of the ventricular assist device 20 according to some applications of the present invention. For some applications, the computer processor 25 (FIG. 1A) of the control console 21 that controls the rotation of the impeller 50 is also configured to control the forward and backward motion of the axial shaft. Typically, both types of motion are generated using the motor unit 23. The scope of the present invention includes controlling the forward and backward motion at 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 forward and backward motion of the axial shaft is synchronized to the subject's cardiac cycle.

[0198] Typically, the motor unit 23 includes a motor 74 configured to impart rotational motion to the impeller 50 via a drive cable 130. As described in more detail below, the motor is typically 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 forward and backward motion, as indicated by double arrow 79. Typically, due to the magnetic coupling of the motor to the drive cable, the motor imparts forward and backward motion to the drive cable, which imparts this motion to the impeller. As described below, for some applications, the drive cable, impeller, and / or axial shaft experience axial forward and backward motion in a passive manner, for example, due to cyclic changes in the pressure gradient against which the impeller is pumping blood. Typically, for such applications, the motor unit 23 does not include an axial motion driver 76.

[0199] For some applications, the magnetic coupling of the motor to the drive cable is as shown in FIG. 7. As shown in FIG. 7, a set of drive magnets 77 are 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 bonded to the inner surface of the ring. For some applications, a spacer 85 is bonded to the inner surface of the ring 81 between the two drive magnets as shown. Driven magnets 82 are disposed between the drive magnets and have axial overlap. The driven magnet 82 is coupled to a proximal end of the drive cable 130 such that a pin is between the drive magnet and the driven magnet. For example, the driven magnet can be cylindrically shaped and can define a bore therethrough, and the proximal end of the drive cable can be attached to an inner surface of the driven magnet that defines the bore. For some applications, the driven magnet is cylindrically shaped and includes a north pole and a south pole that are split from one another along the length of the cylinder along a line 83 that bisects the cylinder, as shown. For some applications, the driven magnet is housed inside a cylindrically shaped housing 87.

[0200] Magnetic coupling is strongest when the magnetic field density is maximized. It is therefore desirable to use relatively strong magnets for the drive and driven magnets, have a small air gap between the drive and driven magnets, and try to minimize field leakage. Typically, the drive and driven magnets are neodymium magnets, which are relatively strong. More typically, the gap between each of the drive magnets and the driven magnet is less than 2 mm, e.g., approximately 1 mm. To reduce field leakage, typically fewer than four magnets (e.g., exactly two magnets as shown) are used as drive magnets for the following reasons:

[0201] Typically, it is desirable to minimize the diameter of the driven magnet, for example, to stabilize the driven magnet. As explained above, the driven magnet is cylindrical in shape and includes a north and south pole, which are split from one another along the length of the cylinder along split line 83. In the region of the periphery of the driven magnet closest to the split line between the north and south poles of the magnet, the magnetic field lines pass directly from the north pole to the south pole of the magnet, rather than crossing the air gap to the first outer magnet, passing through the outer magnet, around the ring 81, across the second driving magnet, and back to the south pole of the driven magnet. As an approximation, any magnetic field lines that may be drawn between the north and south poles (whose length is at least less than the sum of the air gaps between the driven magnet and the driving magnet) will pass from the north pole of the driven magnet to the south pole of the driven magnet, rather than taking an alternative route. Assuming this results in all the magnetic field lines extending around 2mm of the perimeter of the driven magnet on either side of the dividing line between the north and south poles of the driven magnet, that is a total of 4mm of the total perimeter of the driven magnet that does not contribute towards magnetic coupling between the drive and driven magnets. If the driven magnet had four poles instead of just two poles, and correspondingly there were four drive magnets, there would be four 2mm long wasted perimeter sections throughout the perimeter, resulting in a total of 8mm of the 12mm of the perimeter of the inner magnet with wasted magnetic field lines. Some of this loss would be compensated for by the addition of the two additional drive magnets, which increases the field strength. However, the additional outer magnets would be relatively close to each other, which would result in a field leaking between the drive magnets. With the above in mind, typically the motor unit will include fewer than four magnets as the drive magnet (e.g., exactly two magnets as shown), and the driven magnet will be divided into fewer than four poles (e.g., exactly two poles as shown).

[0202] It is noted that in the application shown in FIG. 7, the drive magnets are disposed outside the driven magnets. However, the scope of this application includes, mutatis mutandis, reversing the configuration of the drive and driven magnets. For example, the proximal end of the drive cable may be coupled to two or more driven magnets, the two or more driven magnets being disposed around the drive magnet such that there is axial overlap between the driven and driving magnets. The discussion above regarding the number of magnets to be used as outer magnets and the number of poles into which the inner magnets should be divided is equally applicable to such a configuration. For such a configuration, typically the motor unit includes fewer than four magnets as the driven magnet (e.g., exactly two magnets as shown), and the drive magnet is divided into fewer than four poles (e.g., exactly two poles as shown).

[0203] As described above, a purging system 29 (shown in FIG. 1A ) is typically 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 purging system. For some applications, purging fluid is continuously or periodically pumped into the ventricular assist device via the inlet port 86 and out of the ventricular assist device via the outlet port 88. For some applications, purging fluid is pumped into the ventricular assist device, and the inlet and outlet ports are placed in fluid communication with one another such that a given volume of purging fluid circulates through the device for a period of time. Additional aspects of the purging system are described below.

[0204] Reference is now made to Figures 8A and 8B, which are schematic illustrations of a motor unit 23 according to some applications of the present invention. In general, the motor unit 23 as shown in Figures 8A and 8B is similar to that shown in Figure 7, and unless otherwise stated, the motor unit 23 as shown in Figures 8A and 8B contains similar components as the motor unit 23 as shown in Figure 7. For some applications, the motor unit includes a heat sink 90, which is configured to dissipate heat generated by the motor. Alternatively or additionally, the motor unit includes a ventilation port 93, which is configured to facilitate dissipation of heat generated by the motor. For some applications, the motor unit includes vibration dampers 94 and 96, which are configured to damp vibrations of the motor unit caused by rotational and / or axial back-and-forth movements of components of the ventricular assist device.

[0205] For some applications, the impeller 50 and axial shaft 92 are configured to move axially back and forth within the frame 34 in response to forces acting on the impeller and without the axial shaft having to be actively driven to move in an axial forward and backward motion. Typically, during a subject's cardiac cycle, the pressure difference between the left ventricle and the aorta changes from approximately zero during ventricular systole (hereafter "systole") to a relatively large pressure difference (e.g., 60-100 mmHg) during ventricular diastole (hereafter "diastole"). For some applications, due to the increased pressure difference (against which the impeller is pumping against during diastole), the impeller is pushed distally relative to the frame 34 during diastole, relative to the location of the impeller relative to the frame 34 during systole. And, because the impeller is connected to the axial shaft, the axial shaft is moved forward. During cardiac systole, the impeller (and axial shaft) move back to their systolic positions. Thus, the axial forward and backward movement of the impeller and axial shaft is generated in a passive manner, i.e., without the need for active actuation of the axial shaft and impeller to cause the impeller and axial shaft to undergo this movement.

[0206] Reference is now made to Figure 9, which is a graph showing the variation in length of the drive cable of a ventricular assist device as a function of the pressure gradient against which the impeller of the ventricular assist device varies, as measured in experiments performed by the inventors of the present application. The impeller and drive cable as shown were used to pump a glycerin-based solution through a chamber set up to replicate the left ventricle and aorta, the solution having properties similar to those of blood (e.g., density and viscosity). Due to the increasing volume of fluid disposed in the chamber (which the impeller was pumping into the chamber), the pressure gradient (against which the impeller was pumping) changed. Simultaneously, the movement of the drive cable was imaged and the change in length of the drive cable was determined via machine vision analysis of the images. The graph shown in FIG. 9 shows the change in length of the drive cable measured as a function of the pressure gradient. The y-axis of the graph shown in FIG. 9 is such that 0 mm extension represents the length of the drive cable when the impeller is at rest. It is noted that the graph begins at a pressure gradient value of 65 mmHg and that at this pressure, the extension is negative (approximately -0.25 mm), i.e., the drive cable is shortened relative to the length of the drive cable prior to the start of impeller rotation. This was because the drive cable was configured such that when the impeller first began pumping, it shortened (relative to its length before the impeller was activated) due to coils in the drive cable unwinding, as described in more detail below. As can be seen in the section of the curve shown in Figure 9, after the initial shortening of the drive cable resulting from the effects described above, it was then the case that the drive cable became increasingly elongated as the pressure gradient increased.

[0207] 9 and as explained above, it is typically the case that the impeller moves back and forth relative to the frame 34 in response to fluctuations in pressure (e.g., pressure difference between the left ventricle and the aorta) against which the impeller is pumping blood. And the movement of the impeller causes the drive cable 130 to become more or less elongated.

[0208] For some applications, during operation of the ventricular assist device, computer processor 25 of control console 21 (FIG. 1A) is configured to measure an indication of the pressure exerted on the impeller (which is indicative of the pressure difference between the left ventricle and the aorta) by measuring an indication of tension in drive cable 130 and / or axial movement of the drive cable. For some applications, based on the measured indications, the computer processor detects an event in the subject's cardiac cycle, determines the subject's left ventricular pressure, and / or determines the subject's cardiac afterload. For some applications, the computer processor controls rotation of the impeller and / or responsively controls axial forward and backward movement of the axial shaft.

[0209] For some applications, generally similar techniques are applied to a right ventricular assist device configured to pump blood from the right ventricle to the pulmonary artery, and the computer processor is configured, mutatis mutandis, to determine the pressure differential between the right ventricle and the pulmonary artery in a generally similar manner. For some applications, generally similar techniques are applied to a cardiac assist device configured to pump blood from a first location to a second location (e.g., from the vena cava to the right ventricle, from the right atrium to the right ventricle, from the vena cava to the pulmonary artery, and / or from the right atrium to the pulmonary artery, etc.), and the computer processor is configured, mutatis mutandis, to determine the pressure differential between the first location and the second location in a generally similar manner.

[0210] 7, for some applications, the ventricular assist device 20 includes a sensor 84. For example, the sensor may include a Hall sensor, The sensor is disposed in the motor unit 23 as shown in FIG. 7. For some applications, the Hall sensor measures the variation of the magnetic field generated by one of the magnets to measure the axial movement of the drive cable 130 and to determine the pressure against which the impeller is pumping. For example, the inner driven magnet 82 can be axially longer than the outer driving magnet 77. Due to the inner magnet being longer than the outer magnet, there are magnetic field lines emanating from the inner magnet that do not pass through the outer magnet, and the magnetic flux generated by those magnetic field lines changes as the drive cable and inner magnet move axially, as measured by the Hall sensor. During operation, the motor 74 rotates and generates an AC signal in the Hall sensor, which typically has a frequency between 200 Hz and 800 Hz. Typically, when tension in the drive cable changes due to the subject's cardiac cycle, this produces a low frequency envelope in the signal measured by the Hall sensor, the low frequency envelope typically having a frequency of 0.5-2 Hz. For some applications, a computer processor measures the low frequency envelope and derives the subject's cardiac cycle from the measured envelope. It is noted that typically the axial motion of the magnet is substantially less than that of the impeller, because the full range of motion of the impeller is not transmitted along the length of the drive cable. However, it is true that typically the axial forward and backward motion of the impeller produces a measurable forward and backward motion of the magnet.

[0211] For some applications, the Hall sensor measurements are initially calibrated so that the change in magnetic flux per unit change in pressure against which the impeller is pumping (i.e., per unit change in pressure difference between the left ventricle and the aorta) is known. It is known that in most subjects, the left ventricular pressure is equal to the aortic pressure during systole. Thus, for some applications, the subject's aortic pressure is measured, and the subject's left ventricular pressure at a given time is then calculated by a computer processor based on (a) the measured aortic pressure, and (b) the difference between the magnetic flux measured by the Hall sensor at that time and the magnetic flux measured by the Hall sensor during systole (when the pressure in the left ventricle is assumed to be equal to the aortic pressure).

[0212] Reference is now made to Figures 10A, 10B, and 10C, which are schematic illustrations of the drive cable 130 of the ventricular assist device 20 according to some applications of the present invention. Typically, the rotational motion of the impeller (which is imparted via the axial shaft) and the axial forward and backward motion of the axial shaft as described above are imparted to the axial shaft via the drive cable, as described above. 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 (as shown in Figure 10C, which shows the connection between the distal end of the drive cable and the proximal end of the axial shaft). For some applications, the drive cable includes a plurality of wires 134 arranged in a tightly coiled configuration to provide sufficient strength and flexibility to the drive cable such that a portion of the cable can be maintained within the aortic arch (corresponding to arrow 145 in FIG. 10A ) while the cable rotates and moves in an axial forward and backward motion. The drive cable is typically disposed within a first outer tube 140 that is configured to remain stationary while the drive cable undergoes rotational and / or axial forward and backward motion. The first outer tube is configured to effectively act as a bearing along the length of the drive cable. Typically, the first outer tube is made of a polymer (e.g., polyetheretherketone, etc.), which is a polymer that is used to bond the drive cable and the first outer tube. The first outer tube is configured to be highly resistant to fatigue even under frictional forces generated by relative motion between the tubes. However, because such polymers are typically relatively rigid, only a thin layer of polymer is typically used in the first outer tube. For some applications, the first outer tube is disposed within a second outer tube 142, the second outer tube 142 being made of a material having greater flexibility than the flexibility of the first outer tube (e.g., nylon and / or polyether block amide), and the thickness of the second outer tube is greater than the thickness of the first outer tube.

[0213] Typically, during insertion of the impeller and cage into the left ventricle, the impeller 50 and frame 34 are maintained in a radially constrained configuration by the delivery catheter 143. As explained above, the delivery catheter is retracted to cause the impeller and frame to assume a radially unconstrained configuration. For some applications, as shown in FIG. 10A, the delivery catheter remains in the subject's aorta during operation of the left ventricular device, and the outer tube 142 is disposed inside the delivery catheter. To retract the left ventricular device from the subject's body, the delivery catheter is advanced over the impeller and frame, causing the impeller and frame to assume their radially constrained configuration. The catheter is then withdrawn from the subject's body.

[0214] 10C, typically the axial shaft and cable define a continuous lumen 132 therethrough. For some applications, the left ventricular device is guided to the aorta and to the left ventricle by placing the axial shaft and cable over a guidewire 10 (described above), with the guidewire disposed inside the lumen 132. For some applications, by using the lumen of the axial shaft and cable in this manner, it is not necessary to provide an additional guidewire guide for use during insertion of the left ventricular assist device 20. For some applications, the axial shaft and cable have an outer diameter greater than 0.6 mm (e.g., greater than 0.8 mm) and / or less than 1.2 mm (e.g., less than 1 mm), e.g., 0.6-1.2 mm or 0.8-1 mm, respectively. For some applications, the diameter of the lumen 132 defined by the shaft and cable is greater than 0.3 mm (e.g., greater than 0.4 mm) and / or less than 0.7 mm (e.g., less than 0.6 mm), e.g., between 0.3 and 0.7 mm, or between 0.4 and 0.6 mm. For some applications, the drive cable 130 has a total length 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., between 1 and 1.4 m, or between 1.1 and 1.3 m. As described above, for some applications, a guidewire additionally passes through the lumen 122 of the distal tip portion 120. Typically, the diameter of the lumen 122 is generally similar to the diameter of the lumen 132.

[0215] 10B, for some applications, the drive cable 130 is comprised of a plurality of coiled wires 134. Typically, due to the impeller having to pump against a pressure gradient during diastole, the impeller is pushed distally relative to the frame 34, relative to the position of the impeller relative to the frame during systole, as described above. If the direction of rotation of the impeller is such that rotation of the drive cable in this direction results in the coiled wires of the drive cable being at least partially tightened, this will result in the coiled wires tightening (i.e., retracting to a wound state such that the radius of the coil is reduced). As the impeller begins to rotate, due to the impeller being rotated in a predetermined rotational direction, and thereby due to the axial elongation, it also causes the impeller to advance relative to the frame. For some applications, at least a portion of the drive cable is configured such that (a) in response to the impeller pumping blood from the left ventricle to the aorta by rotating in a predetermined rotational direction, (b) rotation of the drive cable in this direction results in the coiled wire of the drive cable along a portion of the drive cable at least partially unwinding, causing the portion of the drive cable to axially shorten. By configuring the drive cable in the above manner, the length of the frame 34 does not need to accommodate distal movement of the impeller resulting from drive cable axial elongation in addition to accommodating distal movement of the impeller within the frame resulting from pressure changes due to the subject's cardiac cycle (as described above). For some applications, the extent to which the drive cable can unwind and thereby axially shorten is limited by the outer tube in which the drive cable is disposed, preventing the drive cable from expanding radially. Thus, for some applications, the axial shortening of the drive cable is only a relatively small amount. For some applications, the drive cable does not shorten due to the outer tube limiting the extent to which the drive cable can unwind and thereby axially shorten. However, even in such applications, the drive cable is typically configured not to elongate due to the winding of the coil configured as described above.

[0216] Alternatively or additionally, the impeller is inserted into the frame 34 with the drive cable already in a preloaded state (i.e., the impeller exerts tension on the drive cable, which causes the drive cable to elongate axially relative to its rest state). Due to the preloading of the drive cable, when rotation of the impeller is initiated, this does not cause the drive cable to elongate axially because the drive cable is already axially elongated relative to its rest state. For some such applications, the impeller is still configured to experience axial forward and backward movement as a result of pressure changes due to the subject's cardiac cycle (as described above).

[0217] For some applications, debris is generated by frictional forces between the drive cable and the outer tube 140. Alternatively or additionally, a fluid (e.g., a purging fluid) is disposed between the drive cable and the outer tube. Typically, due to the coiled drive cable wrap, the drive cable acts as an impeller and pumps debris and / or fluid axially relative to the outer tube 140. For some applications, the drive cable wrap is oriented such that the drive cable is configured to pump debris and / or fluid toward the proximal end of the ventricular assist device and not toward the distal end of the ventricular assist device toward the patient's left ventricle by rotating in a given rotational direction.

[0218] Reference is now made to Figures 11A and 11B, which are schematic illustrations of an interface component 154 forming an interface between respective portions of a drive cable 130 of a ventricular assist device 20 according to some applications of the present invention. For some applications, the drive cable includes a first and a second portion. Also, reference is again made to Figure 10A, where typically the first portion is configured to be disposed within the subject's aortic arch (i.e., the portion of the aorta corresponding to arrow 145) and the second portion is configured to be disposed along the descending aorta (the portion of the aorta corresponding to arrow 147), typically extending to the motor unit 23 outside the subject's body. Generally, it is desirable for the drive cable 130 to be relatively flexible in locations where it experiences significant curvature, such as the aortic arch. However, a drive cable with greater flexibility is also typically more axially stretchable than a drive cable with less flexibility. Thus, for some applications, there is a tradeoff between wanting the drive cable to be flexible enough to conform to the curvature of the aortic arch, but on the other hand not wanting the drive cable to experience significant axial stretch (which may result in loss of control over the axial position of the impeller). For some applications, each portion of the drive cable has a respective level of flexibility. For example, a first portion of the drive cable configured to be disposed in the aortic arch may have a first flexibility, while a second portion of the drive cable configured to be disposed in the descending aorta may have a second flexibility, the first flexibility being greater than the second flexibility.

[0219] For some applications, the first portion is configured to have greater flexibility than the second portion by including fewer coils of wire 134 in the first portion than in the second portion. For example, as shown in Figures 11A-11B, the first portion can include more than four wires and fewer than eight wires (e.g., 4-8 wires, or 5-7 wires, e.g., 6 wires) and the second portion can include more than eight wires and fewer than twelve wires (e.g., 8-12 wires, or 9-11 wires, e.g., 10 wires). For some applications, the length of the first portion of the drive cable is greater than 20 cm (e.g., greater than 25 cm) and less than 40 cm (e.g., less than 35 cm), e.g., 20-40 cm, or 25-35 cm. For some applications, the length of the second portion of the drive cable is greater than 60 cm (e.g., greater than 70 cm) and less than 100 cm (e.g., less than 90 cm), for example, between 60 and 100 cm, or between 70 and 90 cm.

[0220] For some applications, the two portions of the drive cable are coupled together via an interface component 154. Typically, the wires of the two portions are welded to the interface component. For some applications, a groove 157 is cut into the interface component. The groove is configured so that stresses generated by the wires at the interface are spread over a radius of the groove, as opposed to being concentrated at the point where the wires are welded to the interface component. For some such applications, the interface component additionally includes a protrusion 158 that holds the wires in place during welding of the wires to the interface component.

[0221] Reference is now made to Figures 11C, 11D, and 11E, which are schematic illustrations of an interface 156 between a drive cable and an axial shaft 92 of a ventricular assist device, according to some applications of the present invention. For some applications, techniques generally similar to those described with reference to Figures 11A-11B are used to couple the drive cable to the axial shaft. For some applications, the proximal end of the axial shaft (which defines the interface 156) includes a groove 157 and / or a protrusion 158, generally as described above and shown in Figure 11C.

[0222] 11D, for some applications, as the coiled wire approaches the interface 156, the coiled wire is at least partially straightened (i.e., the pitch of the wire is increased) so that the angle the wire makes with the interface is less sharp than it would be if the wire were straightened. By making the angle less sharp, stresses are reduced at the point where the wire is welded to the interface component. With reference to FIG. 11E, for some applications, in addition to being straightened, the wire is flattened and pushed radially inward as the wire approaches the interface 156. For some applications, the wire is flattened sufficiently so that each wire in the coil contacts its neighbors, forming a cylinder, for example, as shown. For example, the shape of the wire can be changed from having a circular cross-section with a radius of approximately 0.2 mm to an elliptical cross-section with a minor axis of 0.12 mm. For some applications, the flattening is performed along a length between 1 mm and 3 mm. For some applications, the wire is flattened by placing an overtube 159 around the wire, placing the overtube and wire over a mandrel, and crushing the overtube and wire radially inward. The overtube and flattened wire are then welded to the axial shaft 92 at the interface.

[0223] For some applications, a technique generally similar to that described with reference to FIGS. 11D and 11E is used to connect the two portions of the drive cable together. For some applications, the coiled wire is at least partially straightened (i.e., the pitch of the wire is increased) as it approaches the interface component 154 so that the angle the wire makes with the interface is less sharp than it would be if the wire had not been straightened. By making the angle less sharp, stresses are reduced at the point where the wire is welded to the interface component. For some applications, in addition to being straightened, the wire is flattened and pushed radially inward as it approaches the interface component 154. For some applications, the wire is sufficiently flattened so that each wire in the coil contacts its neighbors, for example, forming a cylinder. For example, the shape of the wire can be changed from having a circular cross-section with a radius of approximately 0.2 mm to an elliptical cross-section with a minor axis of 0.12 mm. For some applications, flattening is performed along a length between 1 mm and 3 mm. For some applications, the wire is flattened by placing an overtube (not shown, but similar to overtube 159) around the wire, placing the overtube and wire over a mandrel, and crushing the overtube and wire radially inward. The overtube and flattened wire are then welded to interface component 154.

[0224] For some applications, a crimping technique is used to connect two portions of a drive cable together. For some such applications, the ends of an inner tube and an outer tube are placed on the inside and outside, respectively, of the ends of the two portions of the drive cable, which will form an interface between the portions. The inner tube is then placed over a rigid mandrel, and the inner and outer tubes and the end of the drive cable are crimped together by applying pressure around the outside of the outer tube. The ends of the portions of the drive cable and the inner and outer tubes are crimped together by applying pressure around the outside of the outer tube. When the tubes are crimped together, this forms an interface between the portions of the drive cable. For some applications, a similar crimping technique is performed to connect the drive cable to the axial shaft at interface 156.

[0225] Reference is now made to FIG. 12, which is a schematic illustration of a drive cable 130 of a ventricular assist device 20 including a friction-reducing element 170 disposed around at least a portion of the drive cable, according to some applications of the present invention. For some applications, the friction-reducing element 170 is used to reduce friction between the drive cable 130 (which rotates during operation of the ventricular assist device) and the outer tube 142 (which remains stationary during rotation of the drive cable). In the example shown, the friction-reducing element 170 is a ball bearing. However, the scope of the present invention includes using other friction-reducing elements to reduce friction between the drive cable and the outer tube. For example, other rolling element bearings may be used, such as cylindrical rollers, spherical rollers, gear bearings, tapered rollers, needle rollers, and / or toroidal roller bearings, etc. For some applications, the friction-reducing element is used as an alternative to including the first outer tube 140 in addition to the second outer tube 142. In the example shown in FIG. 12, the friction reducing element is disposed between the drive cable and the second outer tube, and the ventricular assist device does not include first and second outer tubes.

[0226] Typically, the ventricular assist device traverses the subject's aortic arch and / or other portions of the subject's vasculature that are substantially curved. In the absence of a friction-reducing element, the drive cable 130 and the tube 142 will typically contact one another, particularly in the curved portions of the vasculature. As described above, the drive cable 130 will typically experience rotational motion, and for some applications, additionally, forward and backward axial motion with respect to the tube 142. Thus, in the absence of a friction-reducing element (or the first outer tube 140, as described above), there will be significant frictional forces that are generated where the drive cable and the outer tube 142 contact one another. Thus, for some applications, a friction-reducing element is disposed between the drive cable 130 and the outer tube 142 to reduce frictional forces that are generated where the drive cable 130 and the outer tube 142 contact one another. For some applications, friction-reducing elements are disposed between drive cable 130 and outer tube 142 substantially along the entire length of drive cable 130 and outer tube 142. Alternatively, friction-reducing elements are disposed between drive cable 130 and outer tube 142 where drive cable 130 and outer tube 142 are configured to be substantially curved, for example, where drive cable 130 and outer tube 142 are disposed in the aortic arch during operation of the ventricular assist device.

[0227] Reference is now made to FIG. 13, which is a schematic illustration of a procedure for purging the drive cable 130 of the ventricular assist device 20, according to some applications of the present invention. For some applications, the proximal bearing 116, the axial shaft 92, and the cable 130 are surrounded by the first and second outer tubes 140 and 142, as described above. Typically, both the first and second outer tubes remain stationary during rotation of the drive cable. For some applications, a purging fluid (e.g., a fluid containing glucose or dextrose) is pumped between the first and second outer tubes, and an opening 146 is present in the first outer tube near the proximal bearing. As described above, typically, the purging system 29 (shown in FIG. 1A) allows the flow of purging fluid through the inlet port 86 and the outlet port 88 (shown in FIGS. 7, 8A, and 8B). 13. For some applications, purging fluid flows between the drive cable 130 and the first outer tube 140, as shown by purging fluid flow arrow 148 in FIG. 13. In this manner, the interface between the drive cable 130 (which rotates) and the outer tube 140 (which remains stationary during rotation of the drive cable) is purged. For some applications, some of the purging fluid additionally flows to the interface between the axial shaft and the proximal bearing 116, thereby purging the interface, as shown by purging fluid flow arrow 149 in FIG. 13.

[0228] For some applications, the purging fluid is pumped through a lumen 132 defined by the drive cable 130 and the axial shaft 92 such that at least some of the fluid flows all the way to the distal end of the axial shaft. For some applications, some of the purging fluid thus flows to the interface between the axial shaft and the distal bearing 118, thereby purging the interface, as shown by the purging fluid flow arrows 150 in FIG.

[0229] For some applications, a hemostatic valve 152 is disposed at the distal end of lumen 122 of distal tip section 120, as described above. Alternatively or additionally, a plug (not shown) is disposed at the distal end of lumen 122 of tip section 120. Typically, the hemostatic valve and / or plug prevents blood from flowing into lumen 122 and / or into lumen 132. More typically, the plug prevents purging fluid from flowing out of the distal end of lumen 122, thereby causing purging fluid to flow toward the interface between axial shaft 92 and distal bearing 118, as shown by purging fluid flow arrows 150 in FIG.

[0230] For some applications, alternative techniques to those described above are used to introduce fluid (e.g., a fluid containing glucose) into the ventricular assist device. In the application shown in FIG. 13, the fluid is allowed to flow distally after passing through opening 146, as indicated by arrow 149 and as described above. However, for some applications, the flow of fluid in the distal direction is prevented (i.e., there is no fluid flow indicated by arrow 149). For some such applications, the fluid is first released into the space between drive cable 130 (which rotates) and outer tube 140 (which remains stationary during rotation of the drive cable) such that the fluid fills the space between the drive cable and outer tube 140 proximal to opening 146. For example, the fluid may be pumped into the space through the gap between first outer tube 140 and second outer tube 142, as shown. Fluid is then typically maintained in place between the drive cable and outer tube 140, proximal to opening 146, throughout operation of the ventricular assist device. The fluid is configured to remove air from the space between the drive cable and the outer tube and / or to reduce frictional forces between drive cable 130 (which rotates) and outer tube 140 (which remains stationary during rotation of the drive cable).

[0231] For some applications, a generally similar technique is implemented, but fluid is pumped between the drive cable 130 (which rotates) and the outer tube 140 (which remains stationary during rotation of the drive cable) during operation of the ventricular assist device. For example, fluid may be pumped into the space through the gap between the first outer tube 140 and the second outer tube 142 as shown. For applications, fluid is pumped between the drive cable and the outer tube continuously during operation of the ventricular assist device, or periodically between the drive cable and the outer tube during operation of the ventricular assist device. It is noted that for such applications, fluid is pumped between the drive cable and the outer tube, but does not flow into the subject's bloodstream, as distal fluid flow is prevented, as described above. The pumping of fluid is configured to remove air from the space between the drive cable and the outer tube to reduce frictional forces between the drive cable 130 (which rotates) and the outer tube 140 (which remains stationary during rotation of the drive cable) and / or to remove debris generated by the ventricular assist device from the interface between the drive cable and the outer tube.

[0232] Reference is now made to Figures 14A and 14B, which are schematic illustrations of a frame 34 of a ventricular assist device 20 according to some applications of the present invention, with a stator 182 coupled to a proximal portion of the frame. For some applications, the stator is integrally formed with the frame 34, as described in more detail below. Typically, the stator includes a plurality of curved projections 66 (e.g., more than two and / or less than eight curved projections 66) that extend from the frame 34 when the device 20 is in a radially unconstrained configuration, and the projections 66 are made of a flexible material, such as a polymer, such as polyurethane and / or silicone. The curvature of the curved projections is typically oriented to oppose the direction of rotation of the impeller, as described in more detail below. For some applications, due to the use of curved protrusions (e.g., curved to face the direction of rotation of the impeller of the ventricular assist device, as described in more detail below), the stator 182 is configured to reduce rotational flow components from the blood flow before the blood flows out the proximal end of the frame of the ventricular assist device.

[0233] As explained above, typically the device 20 is inserted transcatheterically into the subject's ventricle with the frame 34 in a radially constrained state. Upon release from the catheter, the frame automatically assumes its unconstrained shape due to the self-expansion of the frame 34. Typically, during insertion of the frame into the left ventricle, the curved projections of the stator are in a collapsed state and do not substantially increase the minimum diameter at which the frame can be radially constrained relative to if the tube did not contain the curved projections. As the frame 34 expands, the curved projections are configured to automatically assume their curved configuration due to the curved projections being coupled to the frame 34.

[0234] For some applications, the curved protrusions 66 are made from a flexible material, such as a polymer, such as polyurethane and / or silicone. The curved protrusions are typically coupled to struts 186 of the frame 34, which are curved, the curvature of the curved struts thereby defining the curvature of the curved protrusions. Typically, the flexible material is coupled to the frame 34 such that it defines a lumen 188 (FIG. 14B) therethrough, which is aligned with the longitudinal axis of the frame. The axial shaft 92 of the ventricular assist device typically passes through the lumen 188 into the proximal end of the frame.

[0235] For some applications, a plurality of elongate elements 190, e.g., strings and / or tubing, may be provided to facilitate coupling of the flexible material to the frame, to shape the flexible material into a desired shape, and / or to facilitate formation of the lumen 188. 14B 。 For some applications, the curved struts 186 define a ring 192 or other coupling element at their distal ends, and the elongated elements 190 are tied to it. The flexible material is typically coupled to the frame such that curved films of material are supported by the curved struts and the elongated elements, each of the films defining a respective curved projection. For some applications, the strings and / or wires tied to the proximal end of the frame are tied to a circle 191, which defines one of the ends of the lumen 188. For example, during formation of the stator, a mandrel may be placed through the proximal bearing 116, and the elongated elements may be tied to the ring 192 and may be caused to surround the mandrel, so as to define the pattern of elongated elements shown in FIG. 14B. The proximal end of the frame with the elongated elements and mandrel is then dipped into a material (which is typically a polymer, such as silicone, etc.) while the material is in an uncured liquid state. The material is then cured, e.g., by being left to dry, so that the material solidifies. Once the material is dry, the mandrel is typically removed. For some applications, the other end of the lumen 188 is defined by a proximal bearing 116 disposed at the proximal end of the frame 34. Typically, the flexible material extends from the circle 191 defined by the string and / or wire to the proximal bearing 116 to define the lumen 188. For some applications, sutures 189 are tied around the curved struts 186 to facilitate connection between the material and the struts, as described above with reference to the sutures 53 of the impeller 50, for example.

[0236] Reference is now made to FIG. 15A, which is a schematic illustration of a flattened profile of the frame 34 of the ventricular assist device 20 according to some applications of the present invention. As shown, the frame includes curved struts 186 at its proximal end with rings 192 disposed toward the respective tips of the struts. Reference is also made to FIG. 15B, which is a schematic illustration showing a close-up of the proximal end of the frame 34 according to some applications of the present invention. The tips 194 of the curved struts 186 typically define the orientation of the leading edge of the corresponding blades (i.e., curved projections) of the stator when a flexible material is coupled to the curved struts. Additionally, reference is made to FIG. 15C, which is a schematic illustration of the frame 34 according to some applications of the present invention, showing the frame with the material defining the curved projections 66 coupled to the frame. It can be observed that the orientation of the leading edge of the curved protrusion is defined by the orientation of the corresponding tip of the curved strut.

[0237] As shown in FIG. 15B, the tips 194 of the curved struts 186 are shaped to define an angle alpha with respect to the axial component of blood flow through the frame, which is indicated by arrow 196 and is parallel to the longitudinal axis of the frame toward the proximal end of the frame. The leading edges of the corresponding curved projections also typically define an angle with respect to the general direction of blood flow that is approximately equal to the angle alpha, as shown in FIG. 15C. (For some applications, as the struts 186 undergo radial expansion, the angle of the leading edges of the curved projections will be slightly less than alpha.) For some applications, the angle alpha will be greater than 45 degrees (e.g., greater than 60 degrees) and / or less than 85 degrees (e.g., less than 80 degrees), e.g., between 45 and 85 degrees, or between 60 and 80 degrees.

[0238] The direction of rotation of the impeller is indicated by arrow 198 in FIG. As can be seen in FIG. 1C, the curvature of the curved protrusions is typically such that it opposes the direction of rotation of the impeller, which is the direction of rotation of the rotational flow component in the blood flow as imparted to the blood flow by the impeller. From their distal ends to their proximal ends, the curved protrusions curve progressively closer to being parallel to the longitudinal axis of the frame. The curvature of the curved protrusions is such that it reduces the rotational flow component from the blood flow before the blood flows out of the proximal end of the ventricular assist device frame.

[0239] Reference is now made to Figures 16A, 16B, 16C, and 16D, which are schematic illustrations of a ventricular assist device 20 according to some applications of the present invention, the ventricular assist device including one or more blood pressure measurement tubes 210. As described above, typically, the ventricular assist device includes a tube 24 that traverses the subject's aortic valve such that a proximal end of the tube is disposed in the subject's aorta and a distal end of the tube is disposed in the subject's left ventricle. Typically, a blood pump (which typically includes an impeller 50) is disposed in the tube 24, in the subject's left ventricle, and configured to pump blood through the tube 24 from the left ventricle into the subject's aorta. For some applications, the blood pressure measurement tube 210 is configured to extend at least to the outer surface 212 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 the tube 24. A pressure sensor 216 (schematically illustrated in FIG. 1A) measures the pressure of the blood in the blood pressure measurement tube. Typically, by measuring the pressure of the blood in the blood pressure measurement tube, the pressure sensor thereby measures the subject's blood pressure outside the tube 24. Typically, the blood pressure measurement tube 210 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 towards the proximal end of the tube, e.g., outside the subject's body. For some applications, a computer processor 25 (FIG. 1A) receives an indication of the measured blood pressure and controls the pumping of blood by the impeller in response to the measured blood pressure.

[0240] 16A and 16B, for some applications, the one or more blood pressure measurement tubes include one or more left ventricular blood pressure measurement tubes 220 that are configured to extend to an outer surface of the blood pressure pump tube 24 at a location along the tube that is configured to be in the subject's left ventricle proximal to the blood pump (e.g., proximal to the impeller 50). For such applications, the pressure sensor is configured to measure the subject's left ventricular pressure by measuring the pressure of blood in the left ventricular blood pressure measurement tube. For some applications, the ventricular assist device includes two or more such left ventricular blood pressure measurement tubes, for example, as shown in FIG. 16A and 16B. For some applications, based on the blood pressure measured in each of the left ventricular blood pressure measurement tubes, the computer processor 25 determines whether an opening of one of the two or more left ventricular blood pressure measurement tubes is occluded. This may occur, for example, due to the opening contacting the wall of the ventricular septum and / or portions within different ventricles. Typically, in response to determining that the opening of one of the two or more left ventricular blood pressure measuring tubes is blocked, the computer processor determines the subject's left ventricular pressure based on the blood pressure measured in a different one of the two or more left ventricular blood pressure measuring tubes.

[0241] For some applications, the one or more blood pressure measurement tubes may include one or more aortic blood pressure measurement tubes 222, which may be configured to be in the aorta of the subject, as shown in FIG. 16C. The pressure sensor is configured to extend to an outer surface of the tube at a location along the tube. For such applications, the pressure sensor is configured to determine the aortic pressure of the subject by measuring the pressure of blood in the aortic blood pressure measurement tube. For some applications, the ventricular assist device includes two or more such aortic blood pressure measurement tubes, for example as shown in FIG. 16C. For some applications, based on the blood pressure measured in each of the aortic blood pressure measurement tubes, the computer processor 25 determines whether an opening of one of the two or more aortic blood pressure measurement tubes is occluded. This may occur, for example, due to the opening contacting the wall of the aorta. Typically, in response to determining that an opening of one of the two or more aortic blood pressure measurement tubes is occluded, the computer processor determines the aortic pressure of the subject based on the blood pressure measured in a different one of the two or more aortic blood pressure measurement tubes.

[0242] For some applications, the ventricular assist device includes both a left ventricular pressure measuring tube and an aortic pressure measuring tube, all of which extend to the outer surface of tube 24, as shown, for example, in FIG. 16C.

[0243] 16C , for some applications, the drive cable 130 extends from the motor outside the subject's body to the axial shaft 92, and the impeller 50 is disposed on the axial shaft 92, as described above. Typically, the drive cable is disposed in the outer tube 142. For some applications, the drive cable is disposed in the first outer tube 140 and the second outer tube 142, as described above. For some applications, one or more blood pressure measurement tubes are disposed in the outer tube 142 surrounding the drive cable. For some applications, a portion of the one or more blood pressure measurement tubes is defined by the wall of the outer tube 142, as shown. For some applications, within the outer tube 142, the blood pressure measurement tube has an elliptical cross-section (as shown). Typically, this increases the cross-sectional area of ​​the tube relative to if the tube had a circular cross-section. Typically, within the distal portion of each blood pressure measurement tube (which extends to opening 214), the tube has a circular cross-section. For some applications, the diameter of the distal portion of the tube is greater than 0.2 mm and / or less than 0.5 mm (e.g., between 0.2 and 0.5 mm).

[0244] As shown in FIG. 16A, for some applications, the aortic blood pressure is measured using at least one aortic blood pressure measuring tube 222, which defines an opening 219 at its distal end in the outer tube 142. The aortic blood pressure measuring tube is configured to extend from outside the subject's body to the outer surface of the outer tube 142 in the subject's aorta, such that the opening at the distal end of the aortic blood pressure measuring tube is in direct fluid communication with the subject's aortic blood flow. It is noted that for such applications, the aortic blood pressure measuring tube does not extend to the outer surface of the tube 24. The blood pressure sensor 216 is configured to measure the subject's aortic blood pressure by measuring the blood pressure in the aortic blood pressure measuring tube. For some applications, the opening 219 in the outer tube 142 is disposed in the tube 24, as shown in FIG. 16D. The aortic pressure is measured via the opening 219. This is because the pressure inside the tube 24 at a location downstream of the impeller is typically equal to the aortic pressure.

[0245] As shown in FIGS. 16A and 16B, for some applications, outer tube 142 may be configured to be disposed within tube 24. A groove 215 is defined in a portion of the surface of the outer tube 24. Typically, during insertion of the ventricular assist device into the subject's body, the portion of the blood pressure measurement tubing 210 that extends from within the tube 24 to at least the outer surface of the tube 24 is configured to be disposed in the groove such that no portion of the blood pressure measurement tubing protrudes beyond the outer surface of the outer tube.

[0246] 16D, for some applications, the distal portion of the blood pressure measurement tube 210 is disposed on the outside of the tube 24. For example, as shown, the blood pressure measurement tube 210 can extend from the outer tube 142 to the proximal end of the tube 24, after which the blood pressure measurement tube can be integrated into the outer surface of the tube 24. For some applications, the tube or tubes run along the outer surface of the tube 24 in the manner shown in FIG. 16D, but the tubes continue to the distal end of the tube 24, all the way to the tip portion 120 of the ventricular assist device. The tubes are used to inflate an inflatable portion at the tip portion, as described in more detail below with reference to FIG. 21C.

[0247] Although the ventricular assist device as described with reference to FIGS. 16A-16D has been described as including a blood pump configured to be disposed in the left ventricle of a subject, for some applications, the blood pressure measuring tube 210 and techniques described herein for use with the blood pressure measuring tube 210 are used with ventricular assist devices including a blood pump elsewhere (e.g., in the aorta of a subject). For some applications, generally similar techniques are used with right ventricular assist devices. For example, the device 20 may be inserted into the right ventricle and used to pump blood from the right ventricle to the pulmonary artery. For some such applications, the blood pressure measuring tube is used to measure pressure in the right ventricle and / or the pulmonary artery. For some applications, a device generally similar to the device 20 is used as a cardiac assist device by being used to pump blood in an antegrade direction from the right atrium to the right ventricle, from the vena cava to the right ventricle, from the right atrium to the pulmonary artery, and / or from the vena cava to the pulmonary artery. For some such applications, the blood pressure measuring tube is used to measure pressure in the right ventricle, the vena cava, the right atrium, and / or the pulmonary artery.

[0248] In general, the scope of the present invention includes the application of any of the apparatus and methods described herein, mutatis mutandis, to a right ventricular assist device. A right ventricular assist device typically has a configuration generally similar to that described herein and is used to pump blood from the right ventricle to the pulmonary artery, with tube 24 passing through the pulmonary semilunar valve. For some applications, components of device 20 are applicable to different types of blood pumps. For example, embodiments of the present invention may be applicable to pumps 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. Such embodiments may include features of pump portion 27, features of impeller 50, drive cable 130, devices and methods for measuring blood pressure, devices and methods for measuring flow, etc.

[0249] For some applications, techniques generally similar to those described with reference to blood pressure measurement tube 210 are implemented using electrical wires that extend from within blood pressure pump tube 24 (which typically extends from outside the subject's body) to an outer surface of tube 24 such that at least the tips of the wires are in electrical communication with the subject's blood flow outside tube 24. The subject's blood pressure outside tube 24 (e.g., the subject's ventricular blood pressure and / or the subject's aortic blood pressure) is measured by detecting an electrical parameter using the portion of the wire that is in electrical communication with the subject's blood flow outside tube 24.

[0250] Reference is now made to Figures 17A, 17B, and 17C, which are schematic illustrations of an outer tube 142 of a ventricular assist device 20 according to some applications of the present invention, the outer tube including a pitot tube 225 configured to measure blood flow through the tube 24 of the device. The portion of the outer tube 142 shown in Figures 17A-17C is typically disposed within the tube 24. For some applications, a flow obstruction 226 (which is typically funnel-shaped) is configured to create a stagnation region near a stagnation pressure tap 227. For some applications, as shown in Figure 17A, a flow straightener 228 is added to the outer surface of the tube 142 to remove any swirl component of the flow (which does not contribute to the axial flow rate). Alternatively, the stagnation pressure tap is disposed sufficiently proximal within the funnel-shaped flow obstruction 226 that the flow obstruction itself acts to remove the swirl component of the flow before the blood reaches the stagnation pressure tap, as shown in FIG. 17B. For some applications, the stagnation pressure tap includes a short tube 233 that protrudes from the outer tube 142 within the funnel-shaped flow obstruction 226, such that an opening of the short tube 233 faces the direction of axial blood flow through the tube 24. The outer tube 142 additionally defines an opening 219, generally as described above, which functions as the stationary pressure tap 229. The pressure within the stagnation pressure tap 227 and within the stationary pressure tap 229 is measured using a pressure sensor, e.g., a pressure sensor disposed outside the subject's body, as described above with reference to FIGS. 16A-16D.

[0251] In some applications, the flow through the tube 24 is calculated based on the pressure measurements. For example, the flow through the tube 24 may be calculated using the following formula:

[0252]

number

[0253] Where: Q is the flow through tube 24; C is a calibration constant, which is experimentally determined and takes into account factors such as impeller speed and the geometry of pressure taps 227 and 229; A is the cross-sectional area of ​​tube 24 (not including the area occupied by outer tube 142); ΔP is the difference between the stagnation pressure (measured via pressure tap 227) and the static pressure (measured via pressure tap 229); ρ is the fluid density of blood.

[0254] Reference is now made to Figure 18, which is a schematic illustration of a ventricular assist device 20 according to some applications of the present invention, where the distal tip portion 120 of the device is a radially expandable, atraumatic distal tip portion. As explained above, the ventricular assist device typically includes a tube 24 that traverses the aortic valve of a subject such that a proximal portion of the tube is disposed within the aorta of the subject and a distal portion of the tube is disposed within the left ventricle of the subject. The tube 24 defines one or more blood inlet openings 108 in the distal portion of the tube and one or more blood inlet openings 109 in the proximal portion of the tube. The ventricular assist device defines a blood outlet opening 109 or a plurality of blood outlet openings 109. The blood pump of the ventricular assist device is configured to be disposed within the tube 24 and configured to pump blood from the left ventricle into the tube 24 through the one or more blood inlet openings and out of the tube 24 into the aorta through the one or more blood outlet openings. Typically, a radially expandable atraumatic distal tip portion 120 is disposed within the subject's left ventricle distal to the one or more blood inlet openings. The distal tip portion is configured to be inserted into the left ventricle in a radially constrained configuration. Typically, at least a portion of the distal tip portion is disposed inside a delivery catheter 143 (e.g., shown in FIG. 1B) during insertion of the distal tip portion into the left ventricle, the delivery catheter maintaining the distal tip portion in the radially constrained configuration. The distal tip portion is configured to assume a radially unconstrained configuration within the subject's left ventricle, and in the radially unconstrained configuration, at least a portion 232 of the distal tip portion is radially expanded relative to the radially constrained configuration of the distal tip portion.

[0255] For some applications, the radially expandable atraumatic distal tip portion 120 includes a frame 234 made of a shape memory material (e.g., Nitinol, etc.) that is shape-set so that the frame expands radially when released from the delivery catheter. Typically, the frame is covered by a biocompatible, blood-impermeable material 236, such as polyurethane, polyester, and / or silicone, etc., that is typically configured to form a continuous surface covering the frame. For some applications, the distal tip portion additionally includes an atraumatic distal tip 238, which can have a shape similar to the distal tip portion 120, as described above with reference to FIG. 6C and / or as described below with reference to FIG. 21B.

[0256] The radially expandable atraumatic distal tip portion 120 is typically configured such that, in the radially unconstrained configuration of the distal tip portion, the radially expandable portion 232 of the distal tip portion separates the one or more blood inlet openings 108 in three dimensions from the inner structures of the left ventricle. In this manner, the radially expandable portion 232 of the distal tip portion separates the one or more blood inlet openings 108 from the interventricular septum, tendon tendons, papillary muscles, and / or the apex of the left ventricle. For some applications, the radially expandable portion 232 of the distal tip portion is shaped to direct blood flow from the left ventricle into the one or more blood inlet openings, as shown by arrows 240 in FIG.

[0257] Reference is now made to Figures 19A-19B, which are schematic illustrations of a ventricular assist device 20 according to some applications of the present invention, where the ventricular assist device distal tip portion 120 of the device is a radially expandable atraumatic distal tip portion. Reference is also made to Figures 20A-20B, which are schematic illustrations of a ventricular assist device 20 according to some alternative applications of the present invention, where the ventricular assist device distal tip portion 120 of the device is a radially expandable atraumatic distal tip portion. Figures 19A and 20A show the distal tip portion in its radially constrained configuration while disposed at least partially inside a delivery catheter 143, and Figures 19B and 20B show the distal tip portion in its radially unconstrained configuration. In general, the distal tip portion 120 as shown in Figures 19A-19B and 20A-20B has functionality generally similar to that described above with reference to the distal tip portion 120 as shown in Figure 18.

[0258] As described above, typically at least a portion of the distal tip portion 120 is disposed inside a delivery catheter 143 during insertion of the distal tip portion into the left ventricle, which maintains the distal tip portion in a radially constrained configuration, as shown in FIGS. 19A and 20A. For some applications, the distal tip portion is configured such that a distal region 244 of the distal tip portion protrudes from the distal end of the delivery catheter when the delivery catheter maintains the distal tip portion in the radially constrained configuration. Typically, at least in the radially constrained configuration of the distal tip portion, the distal region is at least semi-rigid and shaped to radially converge longitudinally toward a distal end 246 of the distal tip portion. Typically, the delivery catheter is inserted into the subject's vasculature through a puncture. For some applications, the radially converging semi-rigid distal region of the distal tip portion is configured to act as a dilator by dilating the puncture during insertion of the delivery catheter through the puncture. In this manner, the delivery catheter and components of the ventricular assist device disposed therein may be inserted into the puncture without requiring pre-dilatation of the puncture and without requiring a separate introducer device to facilitate insertion of the delivery catheter through the puncture. For some applications, the distal region is configured to enable percutaneous insertion of the catheter into the punctured blood vessel by placing a first guidewire through the distal region of the distal tip portion. Thereafter, the distal region is used to guide the catheter along the arched anatomy (e.g., the aortic arch) by tracking the course and shape of a second guidewire that is less stiff than the first guidewire. For some such applications, the delivery catheter 143 itself acts as an introducer. Typically, the delivery catheter has an inner diameter of less than 9 mm. For example, the delivery catheter can be an 8 French catheter.For some applications, the delivery catheter is inserted through the puncture via a short introducer device.

[0259] For some applications, the distal tip portion 120 is configured such that in the radially unconstrained configuration of the distal tip portion, the distal end 246 of the distal tip portion is encapsulated within the radially expandable portion 232 of the distal tip portion. For some applications, the distal end is retracted proximally such that the distal end is encapsulated within the radially expandable portion. For example, the distal tip portion can include a spring 249 and / or an elastomeric material configured to retract the distal end of the distal tip portion, as shown in the transition from FIG. 19A to FIG. 19B. For some applications, the distal end is inverted such that the distal end is encapsulated within the radially expandable portion of the distal tip portion. For example, the transition from FIG. 20A to FIG. 20B shows the distal end 246 of the distal tip portion 120 inverting, as shown by arrow 264. For some applications, by encasing the distal end within the radially expandable portion, the distal tip is prevented from becoming entangled within the tendon and / or causing trauma to the internal structures of the left ventricle.

[0260] 19B, for some applications, the distal tip portion includes a plurality of longitudinal struts 248 that are shape-set to curve radially outward. Typically, the struts are made of a shape memory material, such as Nitinol. For some applications, the struts are covered by a biocompatible, blood impermeable material 250, such as polyurethane, polyester, and / or silicone, that is typically configured to form a continuous surface covering the struts. With reference to FIG. 20B, for some applications, the distal tip portion includes a braided shape memory material 260. For some applications, the braided shape memory material may be It is at least partially covered by a biocompatible, blood-impermeable material 262, such as polyurethane, polyester, and / or silicone, which is typically configured to form a continuous surface covering the braided shape memory material, or alternatively, the braided shape memory material is uncovered.

[0261] Reference is now made to Figures 21A, 21B, 21C, and 21D, which are schematic illustrations of the distal tip portion 120 of the ventricular assist device 20 according to some applications of the present invention, where the distal tip portion is configured to be atraumatic. As shown in Figure 21A, for some applications, the distal tip portion includes a J-tip 270 at its distal end. As shown in Figure 21B, for some applications, the distal tip portion includes a bulbous tip 272 at its distal end. As shown in Figures 21A and 21B, for some applications, proximal to the J-tip or bulbous tip, the distal tip portion is externally shaped to define a frustum 274. Typically, the proximal end 276 of the frustoconical portion acts as a stop to prevent advancement of the delivery catheter 143 past it, in a manner generally similar to that described with respect to the flared portion 124 with reference to FIG. 6C.

[0262] For some applications, the tip portion has a straightened configuration, in which the tip portion is shaped to define a frustum, the frustum extending from a proximal end of the frustum to a distal tip of the distal tip portion. For example, a guidewire (such as guidewire 10) inserted through lumen 122 (shown in FIGS. 6A-6C) defined by the tip portion can maintain the tip portion in its straightened configuration. For some such applications, the tip portion has an unconstrained configuration (the tip portion is configured to assume an unconstrained configuration inside the ventricle (e.g., due to the guidewire being removed from inside the tip portion)), in which the distal portion of the frustum is shaped as a J-tip, as shown in FIG.

[0263] As shown in FIG. 21C, for some applications, the outer surface of the distal tip portion includes an inflatable portion 278 (e.g., a balloon) that is configured to be inflated when the distal tip portion is disposed inside the left ventricle of a subject. For some such applications, an inflation lumen for inflating the inflatable portion is configured to pass through the outer tube 142 and then along the outer surface of the tube 24 to the inflatable portion of the distal tip portion. For example, the inflation lumen may be configured in a manner generally similar to that of the blood pressure measurement tube 210 as shown in FIG. 16D, but may continue to run along the outer surface of the tube 24 to the distal end of the tube and then continue to the inflatable portion of the distal tip portion. For some applications, the distal end of the distal tip portion includes a rounded portion 280. As described above, the distal tip portion typically includes a hemostasis valve 152 at its distal end.

[0264] As shown in FIG. 21D, for some applications, the outer surface of the distal tip portion includes a radially expandable portion 282 (e.g., a radially expandable mesh and / or a radially expandable frame, as shown), which is configured to self-expand when the distal tip portion is disposed inside the left ventricle of a subject.

[0265] As shown in FIGS. 21C and 21D, the atraumatic distal tip portion 120 includes: Typically, in the expanded or radially expanded configuration of the distal tip portion, the expanded or radially expanded portion of the distal tip portion is configured to three-dimensionally separate the one or more blood inlet openings 108 from the inner structures of the left ventricle. In this manner, the expanded or radially expanded portion of the distal tip portion separates the one or more blood inlet openings 108 from the interventricular septum, tendon tendons, papillary muscles, and / or the apex of the left ventricle. For some applications, the expanded or radially expanded portion of the distal tip portion is shaped to direct blood flow from the left ventricle into the one or more blood inlet openings, as described above with reference to the distal tip portion 120 as shown in FIG. 18.

[0266] Reference is now made to Figures 22A and 22B, which are schematic illustrations of the distal tip portion 120 of the ventricular assist device 20 according to some applications of the present invention in axially stiffened and non-axially stiffened configurations, respectively. As explained above, for some applications, the distal tip portion is configured such that a distal region 244 of the distal tip portion protrudes from the distal end of the delivery catheter when the delivery catheter maintains the distal tip portion in a radially constrained configuration. Typically, in at least the axially stiffened configuration of the distal tip portion, the distal region is at least semi-rigid and is shaped to converge longitudinally and radially toward the distal end 246 of the distal tip portion. Typically, the delivery catheter is inserted into the vasculature of the subject through a puncture. More typically, the distal tip portion defines a lumen 122 through which the guidewire 10 is inserted as described above. For some applications, the radially converging semi-rigid distal region of the distal tip portion is configured to act as a dilator by dilating the puncture during insertion of the delivery catheter through the puncture. In this manner, the delivery catheter and components of the ventricular assist device disposed therein may be inserted into the puncture without requiring pre-dilatation of the puncture to facilitate insertion of the delivery catheter through the puncture and without requiring a separate introducer device. For some applications, the distal region is configured to enable percutaneous insertion of the catheter into the punctured blood vessel by placing a first guidewire through the distal region of the distal tip portion. Thereafter, the distal region is used to guide the catheter along an arched anatomy (e.g., the aortic arch) by tracking the course and shape of a second guidewire that is less stiff than the first guidewire. For some such applications, the delivery catheter 143 itself acts as an introducer. Typically, the delivery catheter has an inner diameter of less than 9 mm.For example, the delivery catheter can be an 8 French catheter. For some applications, the delivery catheter is inserted through the puncture via a short introducer device.

[0267] For some applications, the distal tip portion is made of a flexible material (e.g., silicone, etc.) with a spring 290 disposed around lumen 122. During insertion of the ventricular assist device into the subject's body, a rigid or semi-rigid reinforcing element 292 (e.g., a rigid or semi-rigid tube) is placed inside the distal region 244 of the distal tip portion to stiffen the distal region. This configuration is shown in FIG. 22A. Thereafter, the reinforcing element is retracted so that the distal region of the distal tip portion becomes atraumatic (e.g., resilient and flexible), as shown in FIG. 22B.

[0268] Reference is now made to Figures 23A and 23B, which are schematic illustrations of a distal tip portion 120 of a ventricular assist device 20 in accordance with some applications of the present invention in radially constrained and radially unconstrained configurations, respectively. For some applications, the distal region 144 of the distal tip portion is shaped as a cone with a slit 294 (e.g., two slits) in the cone. During insertion of the ventricular assist device into the subject's body, the distal region is maintained in its cone-like shape by the delivery catheter 143. This configuration is shown in FIG. 23A. Thereafter, when the delivery catheter is retracted, the distal region is configured to form a two-dimensional circular or elliptical shape by splitting into two semicircles 296 or semi-ellipses around the slit, as shown in FIG. 23B. In the configuration shown in FIG. 23B, the distal tip portion is typically configured to be atraumatic and configured to separate one or more blood inlet openings 108 from the inner structures of the left ventricle in two dimensions. In this manner, the distal tip portion separates one or more blood inlet openings 108 from the ventricular septum, tendon grafts, papillary muscles, and / or the apex of the left ventricle.

[0269] Reference is now made to Figures 24A and 24B, which are schematic illustrations of the distal tip portion 120 of the ventricular assist device 20 according to some applications of the present invention in radially constrained and radially unconstrained configurations, respectively. For some applications, the distal region 244 of the distal tip portion is shaped as a cone and includes slits 294 (e.g., four slits) in the cone. During insertion of the ventricular assist device into the subject's body, the distal region is maintained in its cone-like shape by the delivery catheter 143. This configuration is shown in Figure 24A. Thereafter, when the delivery catheter is retracted, the distal region is configured to form a three-dimensional basket shape by splitting into four arms 298 around the slits, as shown in Figure 24B. (It is noted that the fourth arm is hidden from view in FIG. 24B.) In the configuration shown in FIG. 24B, the distal tip portion is typically configured to be atraumatic and to separate one or more blood inlet openings 108 in three dimensions from the interior structures of the left ventricle. In this manner, the distal tip portion separates one or more blood inlet openings 108 from the interventricular septum, tendon grafts, papillary muscles, and / or the apex of the left ventricle.

[0270] For some applications, the distal tip portion 120 has a pointed distal region 244, with the diameter of the distal tip portion at the proximal end of the distal region being approximately equal to the diameter of the delivery catheter 143. Typically, the pointed distal region 244 has a length that is less than half (e.g., less than a quarter) of the total length of the distal tip portion. More typically, the flexibility of the pointed distal region is greater than the flexibility of the proximal region of the distal tip portion. Typically, the distal region is configured to straighten into a generally cone-like shape when a sufficiently stiff guidewire is inserted therein. For some applications, the distal region is configured to curl into a J-shape (e.g., as shown in FIG. 21A) in the absence of any external force acting on the distal region.

[0271] Typically, the distal region of the distal tip portion acts as a dilator for the delivery catheter 143, allowing percutaneous insertion of the catheter into the punctured blood vessel by placing a first guidewire through the distal region of the distal tip portion. The distal tip portion is then used to guide the catheter along the arched anatomy (e.g., the aortic arch) by tracking the course and shape of a second guidewire that is less stiff than the first guidewire. For some applications, the distal region of the distal tip portion is configured to curl when the second guidewire is being withdrawn, as described above.

[0272] For some applications, the features of, and techniques for implementing, the distal tip portion 120 described with reference to FIGS. 18-24B may be used in conjunction with the tip portion 120. The present invention may be combined with the features described above with reference to FIGS. 6A-6C and / or 13 and techniques for implementing the same.

[0273] Reference is now made to FIG. 25A, which is a schematic illustration of a first portion 160A and a second portion 160B of a coupling element configured to facilitate radial contraction (e.g., during crimping) of an impeller (e.g., impeller 50 described above) independent of other components of a ventricular assist device, according to some applications of the present invention. The first and second portions 160A and 160B are configured to be engaged with one another. The first portion is disposed over the impeller and the second portion is disposed over the frame 34, e.g., over the distal bearing 118 of the frame 34. It is noted that for illustrative purposes, only certain portions of the impeller are shown in FIG. 25A.

[0274] Reference is also made to Figures 25B and 25C, which are schematic illustrations of the respective stages of crimping the impeller according to some applications of the present invention. For some applications, before crimping the outer portion of the ventricular assist device (e.g., the frame 34 of the left ventricular assist device 20 as shown), the impeller is radially contracted by engaging the portions 160A and 160B with each other and by elongating the impeller axially to radially contract the impeller. The outer portion of the left ventricular assist device is then radially contracted. For some applications, crimping the impeller in this manner reduces the possibility of the impeller being damaged during crimping of the outer portion of the left ventricular assist device. Thereafter, when the impeller and the frame are disposed in the left ventricle of the subject, the first and second portions of the coupling element are released from each other, allowing the impeller to move relative to the frame 34.

[0275] 25A-25C, the impeller is configured to be crimped by having only one of its ends (e.g., the proximal end of the impeller) coupled to the axial shaft and the other end (e.g., the distal end) slidable relative to the axial shaft, as described above. The impeller is crimped by sliding the other end of the impeller along the shaft, such that the impeller is axially elongated.

[0276] Reference is now made to FIG. 26, which is a schematic illustration of a stopper 300 configured to prevent distal advancement of the impeller 50 of the ventricular assist device 20 during withdrawal of the ventricular assist device from the subject's body, according to some applications of the present invention. As explained above, typically, to withdraw the ventricular assist device from the subject's body, the delivery catheter 143 is advanced distally over the frame 34 and impeller 50, causing the frame and impeller to assume their radially constrained configuration. In some cases, there is a risk that the drive cable 130 may snap when the impeller is pushed distally by the delivery catheter. For some applications, if the drive cable snaps, then distal advancement of the proximal end of the impeller causes the stopper 300 to engage the shoulder 302, thereby preventing further advancement of the proximal end of the impeller. It is noted that the stopper is configured such that it does not engage shoulder portion 302 during normal operation of the ventricular assist device (and throughout the axial forward and backward movement cycle described above).

[0277] For some applications (not shown), multiple electrodes may be attached to the distal portion of the left ventricular assist device. The electrodes are arranged above the aortic valve. A computer processor 25 (FIG. 1A) applies a current between a distal-most electrode and a proximal-most electrode, the distal-most electrode typically configured to be disposed near the apex of the heart, and the proximal-most electrode typically configured to be disposed above the aortic valve. The conductance of the current between each pair of electrodes is then measured by the computer processor. For some applications, the application of the current and the conductance measurement are performed using techniques generally similar to those described in an article entitled "The Conductance Volume Catheter Technique for Measurement of Left Ventricular Volume in Young Piglets" by Cassidy et al. (Pediatric Research, Vol. 31, No. 1, 1992, pp. 85-90). For some applications, the computer processor is configured to derive a real-time left ventricular pressure-volume loop of the subject based on the conductance measurement. For some applications, a computer processor controls the rotational speed of the impeller in a manner responsive to a derived pressure-volume loop.

[0278] For all of the embodiments of the ventricular assist device 20 described with reference to FIGS. 1A-26, it is noted that although FIGS. 1A and 1B show the ventricular assist device 20 in the left ventricle of a subject, for some applications the device 20 is placed inside the right ventricle of a subject such that the device traverses the subject's pulmonary valve, and the techniques described herein apply mutatis mutandis. For some applications, the components of the device 20 are applicable to different types of blood pumps. For example, embodiments of the present invention may be applicable to pumps 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. Such embodiments may include features of the impeller 50, features of the pump portion 27, the drive cable 130, devices and methods for measuring blood pressure, and the like. Alternatively or additionally, device 20 and / or portions thereof (e.g., impeller 50, even when tube 24 is not present) may be placed inside a different portion of the subject's body to assist in pumping blood from that portion. For example, device 20 and / or portions thereof (e.g., impeller 50, even when tube 24 is not present) may be placed in a blood vessel and used to pump blood through the vessel. For some applications, device 20 and / or portions thereof (e.g., impeller 50, even when tube 24 is not present) may be configured to be placed, mutatis mutandis, in a subclavian or jugular vein at the junction of a vein and a lymphatic vessel, and used to increase lymph flow from the lymphatic vessel into the vein. Because the scope of the present invention 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 may be referred to herein (in the specification and claims) as a blood pump.

[0279] Reference is now made to Figures 27A and 27B, which are schematic illustrations of a ventricular assist device 308 according to some applications of the present invention, the device including a valve 70 for preventing backflow of blood, for example, if the impeller 50 of the ventricular assist device fails. Unlike the ventricular assist device 20 described above with reference to Figures 1A-26, the ventricular assist device 308 includes an impeller disposed in the aorta, rather than in the left ventricle (e.g., as described in WO 18 / 078615 by Tuval, which is incorporated herein by reference). For some applications, the impeller is configured in a manner generally similar to the impeller 50 described above. The impeller is disposed at the proximal end of a tube 312 (e.g., a polyester tube), which traverses the aortic valve and is supported by a frame 31. 27A shows the ventricular assist device as configured when the impeller of the ventricular assist device is functioning normally, such that there is blood flow from the left ventricle 22 to the aorta 30 through tube 312 (which traverses the aortic valve 26), the blood flow being indicated by arrow 72.

[0280] For some applications, tube 312 includes a valve 70 in a region of the tube that is configured to be disposed distal to impeller 50 and near the aortic valve, as shown in FIG. 27B. For example, when impeller 50 fails such that there is backflow of blood through tube 312 (as shown by blood flow arrows 73 in FIG. 27B), the leaflets of valve 70 are configured to close such that there is substantially no backflow of blood from the aorta to the left ventricle. For some applications (not shown), tube 312 includes a valve 70 at a proximal end of the tube that is configured to be disposed in the aorta.

[0281] Reference is now made to Figures 28A, 28B, and 28C, which are schematic illustrations of a ventricular assist device 308 according to some applications of the present invention, the device including a safety balloon 80 for preventing backflow of blood, for example, if the impeller of the ventricular assist device fails. Unlike the ventricular assist device 20 described above with reference to Figures 1A-26, the ventricular assist device 308 includes an impeller disposed in the aorta rather than in the left ventricle (e.g., as described in WO 18 / 078615 by Tuval, which is incorporated herein by reference). For some applications, the impeller is configured in a manner generally similar to the impeller 50 described above. The impeller is disposed at the proximal end of a tube 312 (e.g., a polyester tube), the tube 312 traverses the aortic valve, and a frame 310 supports the tube in an open configuration. FIG 28A illustrates the ventricular assist device as configured when the impeller of the ventricular assist device is functioning normally such that there is blood flow from the left ventricle 22 to the aorta 30 through the tube 312 (which traverses the aortic valve 26), blood flow indicated by arrow 72. For some applications, the ventricular assist device 308 includes a balloon 80 in a region of the tube that is configured to be disposed distal to the impeller 50 and near the aortic valve, as shown in FIG 28B. For example, if the impeller 50 fails and there is retrograde blood flow through the tube 312 (as indicated by blood flow arrow 73 in FIG 28B), the computer processor 25 is configured to inflate the balloon such that the tube 312 is occluded and there is substantially no retrograde blood flow from the aorta to the left ventricle.

[0282] For some applications, the ventricular assist device 308 includes a balloon 80 at a distal end of the tube 312, the balloon 80 configured to be disposed in the left ventricle, as shown in FIGURE 28C. For example, when the impeller 50 has failed such that there is retrograde blood flow through the tube 312 (as shown by blood flow arrows 73 in FIGURE 28C), the computer processor 25 is configured to inflate the balloon such that the tube 312 is occluded and there is substantially no retrograde blood flow from the aorta to the left ventricle.

[0283] The scope of the present invention includes combining 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 herein by reference: U.S. Provisional Patent Application No. 62 / 425 by Tuval, filed November 23, 2016 “Blood International Patent Application No. PCT / IL2017 / 051273 by Tuval entitled "Polymer-Based Hybrid Pumps" (published as WO18 / 096531); International Application No. PCT / IL2017 / 051158 by Tuval entitled "Ventricular assist device," filed October 23, 2017 (published as WO18 / 078615), which claims priority from U.S. Patent Application No. 62 / 412,631 by Tuval, filed October 25, 2016, and U.S. Patent Application No. 62 / 543,540 by Tuval, filed August 10, 2017; International Patent Application No. PCT / IL2017 / 051092 by Tuval, entitled "Blood vessel tube," filed September 28, 2017 (published as WO18-061002), which claims priority from U.S. Provisional Patent Application No. 62 / 401,403 by Tuval, filed September 29, 2016; U.S. Patent Application Publication No. 2018 / 0169313 by Schwammenthal, which is the U.S. national stage of International Patent Application No. PCT / IL2016 / 050525 by Schwammenthal, entitled "Blood pump," filed May 18, 2016 (published as WO16 / 185473), which claims priority from U.S. Provisional Patent Application No. 62 / 162,881 by Schwammenthal, entitled "Blood pump," filed May 18, 2015; U.S. Patent Application Publication No. 2017 / 0100527 by Schwammenthal, which is the U.S. national stage of International Patent Application No. PCT / IL2015 / 050532 by Schwammenthal, entitled "Blood pump," filed May 19, 2015 (published as WO15 / 177793), which claims priority from U.S. Provisional Patent Application No. 62 / 000,192 by Schwammenthal, entitled "Blood pump," filed May 19, 2014; (a) U.S. Provisional Patent Application No. 61 / 779,803, by Schwammenthal, filed March 13, 2013, entitled "Renal pump," and (b) U.S. Patent No. 10,039,874, by Schwammenthal, which is the U.S. national stage of International Patent Application No. PCT / IL2014 / 050289, by Schwammenthal, entitled "Renal pump," filed March 13, 2014 (published as WO14 / 141284), which claims priority from U.S. Provisional Patent Application No. 61 / 914,475, by Schwammenthal, filed November 11, 2013, entitled "Renal pump;" No. 9,764,113, entitled "Curved catheter," issued on September 19, 2017 by Tuval, which claims priority from U.S. Provisional Patent Application No. 61 / 914,470, entitled "Curved catheter," filed on December 11, 2013 by Tuval; and No. 9,597,205 by Tuval, which is a U.S. national phase application of International Patent Application No. PCT / IL2013 / 050495 (published as WO13 / 183060) by Tuval, entitled "Prosthetic renal valve," filed on June 6, 2013, which claims priority from U.S. Provisional Patent Application No. 61 / 656,244 by Tuval, entitled "Prosthetic renal valve," filed on June 6, 2012.

[0284] It will be appreciated by those skilled in the art that the present invention is not limited to what has been particularly shown and described above, but rather, the scope of the present invention includes both combinations and subcombinations of the various features described above, as well as variations and modifications thereof that are not within the prior art, which will occur to those skilled in the art upon reading the foregoing description. The aspects of the present invention are as follows. [Aspect 1] An apparatus, comprising: a blood pump configured to be placed inside a subject's body; The blood pump comprises: an impeller including a proximal bushing and a distal bushing; a frame configured to be disposed about the impeller, the frame including a proximal bearing and a distal bearing; an axial shaft configured to pass through the proximal and distal bearings of the frame and the proximal and distal bushings of the impeller; Including, the proximal bushing of the impeller is coupled to the axial shaft such that the proximal bushing is held in an axially fixed position relative to the axial shaft; the distal bushing of the impeller is not coupled to the axial shaft such that the distal bushing is not held in an axially fixed position relative to the axial shaft; The impeller defines a radially constrained configuration and a radially unconstrained configuration, in which the impeller is introduced into a body of the subject, and in which the impeller is configured to pump blood into the body of the subject, the impeller being configured to move in a radially constrained configuration by sliding the distal bushing over the axial shaft. The device is configured to change from its radially constrained configuration to its radially unconstrained configuration. [Aspect 2] The device of aspect 1, wherein the impeller is configured to be placed inside the subject's left ventricle and configured to pump blood from the subject's left ventricle to the subject's aorta. [Aspect 3] The device of aspect 1, wherein the impeller is configured to be placed inside the subject's right ventricle and configured to pump blood from the subject's right ventricle to the subject's pulmonary artery. [Aspect 4] 2. The apparatus of claim 1, wherein the impeller is configured to be placed inside a blood vessel of the subject. [Aspect 5] 2. The apparatus of claim 1, wherein the impeller is configured to be placed inside a heart chamber of the subject. [Aspect 6] The impeller is at least one helical elongate element extending from the proximal bushing to the distal bushing; a spring disposed inside the helical elongated element along an axis around which the helical elongated element winds; a film of material supported between said helical elongate element and said spring; at least one flexible elongate element extending from the spring to the helical elongate element and configured to maintain the helical elongate element within a given distance from the spring, the at least one flexible elongate element being selected from the group consisting of a string and a wire; 6. The device according to any one of aspects 1 to 5, comprising: [Aspect 7] The apparatus further comprises a delivery catheter; the delivery catheter is configured to maintain the impeller in its radially constrained configuration during introduction of the impeller into the subject's body; the impeller is configured to self-expand when the impeller is released from the delivery catheter, thereby causing the distal bushing to slide proximally over the axial shaft and causing the impeller to assume its radially unconstrained configuration; and The device of any one of aspects 1-5, wherein to retract the impeller from the subject's body, the distal end of the delivery catheter and the impeller are moved relative to one another, and the distal end of the delivery catheter is configured to cause the distal bushing to slide distally over the axial shaft, thereby causing the impeller to assume its radially constrained configuration. [Aspect 8] An apparatus, comprising: ventricular assist devices, The ventricular assist device comprises: an impeller configured to be placed inside the left ventricle of the subject; a frame configured to be disposed around the impeller; a motor configured to drive the impeller to rotate the impeller and thereby pump blood from the left ventricle to the aorta of the subject; Including, The impeller is configured to undergo axial forward and backward movement relative to the frame in response to periodic changes in a pressure differential between the left ventricle and the aorta. the impeller includes a proximal bushing and a distal bushing; the frame includes a proximal bearing and a distal bearing; The ventricular assist device further includes an axial shaft configured to pass through the proximal and distal bearings defined by the frame and the proximal and distal bushings of the impeller; the axial shaft is coupled to at least one of the proximal and distal bushings of the impeller such that the at least one bushing is held in an axially fixed position relative to the axial shaft; 9. The device of embodiment 8, wherein the axial shaft is not held in an axially fixed position relative to the proximal and distal bearings. [Aspect 10] 9. The apparatus of embodiment 8, wherein the ventricular assist device does not include any thrust bearing configured to be disposed within the subject's body. [Aspect 11] The apparatus of embodiment 8, wherein the ventricular assist device further includes one or more thrust bearings configured to be disposed outside the subject's body, and wherein opposition to the thrust generated by rotation of the impeller is provided solely by the one or more thrust bearings disposed outside the subject's body. [Aspect 12] the motor is configured to drive the impeller to rotate the impeller in a given direction of rotation to pump blood from a left ventricle of the subject to an aorta of the subject; The ventricular assist device comprises: an axial shaft, the impeller being disposed on the axial shaft; a drive cable configured to extend from outside the subject's body to the axial shaft, the drive cable configured to rotate to impart rotational motion from the motor to the impeller, at least a portion of the drive cable including a plurality of wires arranged in a coiled configuration, the coiled configuration such that in response to the drive cable rotating in the given direction of rotation, the plurality of wires arranged in the coiled configuration at least partially unwind, causing the portion of the drive cable to axially shorten; 9. The apparatus of embodiment 8, further comprising: [Aspect 13] a sensor configured to detect an indication of axial movement of the impeller and to generate a sensor signal in response thereto; and a computer processor configured to receive the sensor signal and to generate an output in response thereto; 13. The device of any one of aspects 8 to 12, further comprising: [Aspect 14] 14. The apparatus of claim 13, wherein the computer processor is configured to generate an output indicative of the subject's cardiac cycle in response to receiving the sensor signal. [Aspect 15] 14. The apparatus of claim 13, wherein the computer processor is configured to determine a left ventricular pressure of the subject based at least in part on the sensor signal. [Aspect 16] 14. The apparatus of claim 13, wherein the computer processor is configured to vary a rotational speed of the impeller based at least in part on the sensor signal. [Aspect 17] The computer processor includes: configured to determine a left ventricular pressure of the subject based at least in part on the sensor signal; 17. The apparatus of embodiment 16, further configured to vary a rotational speed of the impeller based at least in part on the determined left ventricular pressure. [Aspect 18] 18. The apparatus of claim 17, wherein the computer processor is configured to reduce the rotational speed of the impeller in response to determining that the subject's left ventricular pressure has decreased. [Aspect 19] a magnet, the impeller being coupled to the magnet such that axial movement of the impeller causes the magnet to experience axial movement; a sensor configured to detect magnetic flux generated by the magnet and to generate a sensor signal in response thereto; and a computer processor configured to receive the sensor signal and to generate an output in response thereto; 13. The device of any one of aspects 8 to 12, further comprising: [Aspect 20] 20. The apparatus of embodiment 19, wherein the computer processor is configured to generate an output indicative of the subject's cardiac cycle in response to receiving the sensor signal. [Aspect 21] 20. The apparatus of embodiment 19, wherein the computer processor is configured to determine a left ventricular pressure of the subject based at least in part on the sensor signal. [Aspect 22] 20. The apparatus of embodiment 19, wherein the computer processor is configured to vary a rotational speed of the impeller based at least in part on the sensor signal. [Aspect 23] The computer processor includes: configured to determine a left ventricular pressure of the subject based at least in part on the sensor signal; 23. The apparatus of embodiment 22, further configured to vary a rotational speed of the impeller based at least in part on the determined left ventricular pressure. [Aspect 24] 24. The apparatus of claim 23, wherein the computer processor is configured to reduce the rotational speed of the impeller in response to determining that the subject's left ventricular pressure has decreased. [Aspect 25] the impeller includes a proximal bushing and a distal bushing; the frame includes a proximal bearing and a distal bearing; the ventricular assist device further includes an axial shaft configured to pass through the proximal and distal bearings of the frame and the proximal and distal bushings of the impeller; The apparatus of any one of aspects 8-12, wherein the impeller is coupled to the axial shaft such that the impeller causes the axial shaft to undergo axial forward and backward movement relative to the proximal and distal bearings of the frame. [Aspect 26] The apparatus of aspect 25, wherein the axial shaft is configured to clean an interface between the axial shaft and the proximal and distal bearings of the frame by undergoing an axial forward and backward movement relative to the proximal and distal bearings of the frame. [Aspect 27] The device of aspect 25, wherein the axial shaft is configured to experience axial forward and backward movement relative to the proximal and distal bearings of the frame, as opposed to the axial shaft not experiencing the axial forward and backward movement relative to the proximal and distal bearings of the frame, thereby reducing heating at an interface between the axial shaft and the proximal and distal bearings of the frame. [Aspect 28] An apparatus, comprising: Including a blood pump, The blood pump comprises: an impeller including a proximal bushing and a distal bushing, the impeller configured to pump blood through a body of the subject; a frame configured to be disposed about the impeller, the frame including a proximal bearing and a distal bearing; an axial shaft configured to pass through the proximal and distal bearings of the frame and the proximal and distal bushings of the impeller; Including, the axial shaft is coupled to at least one of the proximal and distal bushings of the impeller such that the at least one bushing is held in an axially fixed position relative to the axial shaft; The device, wherein the axial shaft is not held in an axially fixed position relative to the proximal and distal bearings. [Aspect 29] 30. The apparatus of embodiment 28, wherein the blood pump does not include any thrust bearing configured to be disposed within the subject's body. [Aspect 30] The blood pump further includes one or more thrust bearings configured to be disposed outside the subject's body, the thrust bearings being configured to support the thrust generated by rotation of the impeller. 30. The apparatus of claim 28, wherein resistance to thrust is provided solely by the one or more thrust bearings disposed outside the subject's body. [Aspect 31] a sensor configured to detect an indication of axial movement of the impeller and to generate a sensor signal in response thereto; and a computer processor configured to receive the sensor signal and to generate an output in response thereto; The apparatus of any one of aspects 28 to 30, further comprising: [Aspect 32] 32. The apparatus of claim 31 , wherein the computer processor is configured to generate an output indicative of the subject's cardiac cycle in response to receiving the sensor signal. [Aspect 33] 32. The apparatus of claim 31 , wherein the computer processor is configured to determine a left ventricular pressure of the subject based at least in part on the sensor signal. [Aspect 34] 32. The apparatus of claim 31, wherein the computer processor is configured to vary a rotational speed of the impeller based at least in part on the sensor signal. [Aspect 35] The computer processor includes: configured to determine a left ventricular pressure of the subject based at least in part on the sensor signal; 35. The apparatus of embodiment 34, further configured to vary a rotational speed of the impeller based at least in part on the determined left ventricular pressure. [Aspect 36] 36. The apparatus of claim 35, wherein the computer processor is configured to reduce the rotational speed of the impeller in response to determining that the subject's left ventricular pressure has decreased. [Aspect 37] a magnet, the impeller being coupled to the magnet such that axial movement of the impeller causes the magnet to experience axial movement; a sensor configured to detect magnetic flux generated by the magnet and to generate a sensor signal in response thereto; and a computer processor configured to receive the sensor signal and to generate an output in response thereto; The apparatus of any one of aspects 28 to 30, further comprising: [Aspect 38] 38. The apparatus of embodiment 37, wherein the computer processor is configured to generate an output indicative of the subject's cardiac cycle in response to receiving the sensor signal. [Aspect 39] 38. The apparatus of embodiment 37, wherein the computer processor is configured to determine a left ventricular pressure of the subject based at least in part on the sensor signal. [Aspect 40] 38. The apparatus of embodiment 37, wherein the computer processor is configured to vary the rotational speed of the impeller based at least in part on the sensor signal. [Aspect 41] The computer processor includes: configured to determine a left ventricular pressure of the subject based at least in part on the sensor signal; 41. The apparatus of embodiment 40, further configured to vary a rotational speed of the impeller based at least in part on the determined left ventricular pressure. [Aspect 42] The apparatus of embodiment 41, wherein the computer processor is configured to reduce the rotational speed of the impeller in response to determining that the subject's left ventricular pressure has decreased. [Aspect 43] The device of any one of aspects 28 to 30, wherein the impeller is configured to pump blood from a first location within the subject's body to a second location within the subject's body, and the impeller is configured to undergo axial forward and backward movement relative to the frame in response to a periodic change in pressure differential between the first location and the second location. [Aspect 44] The apparatus of aspect 43, wherein the impeller is configured to pump blood from a left ventricle of the subject to an aorta of the subject, and the impeller is configured to undergo axial forward and backward movement relative to the frame in response to periodic changes in pressure differential between the left ventricle and the aorta. [Aspect 45] The apparatus of aspect 43, wherein the impeller is configured to pump blood from a right ventricle of the subject to a pulmonary artery of the subject, and the impeller is configured to undergo axial forward and backward movement relative to the frame in response to periodic changes in pressure differential between the right ventricle and the pulmonary artery. [Aspect 46] The apparatus of aspect 43, wherein the impeller is configured to pump blood from the subject's right atrium to the subject's right ventricle, and the impeller is configured to undergo axial forward and backward movement relative to the frame in response to periodic changes in pressure differential between the right atrium and the right ventricle. [Aspect 47] The apparatus of aspect 43, wherein the impeller is configured to pump blood from the subject's vena cava to the subject's right ventricle, and the impeller is configured to undergo axial forward and backward movement relative to the frame in response to periodic changes in pressure differential between the vena cava and the right ventricle. [Aspect 48] The apparatus of aspect 43, wherein the impeller is configured to pump blood from the subject's right atrium to the subject's pulmonary artery, and the impeller is configured to undergo axial forward and backward movement relative to the frame in response to periodic changes in pressure differential between the right atrium and the pulmonary artery. [Aspect 49] The apparatus of aspect 43, wherein the impeller is configured to pump blood from the subject's vena cava to the subject's pulmonary artery, and the impeller is configured to undergo axial forward and backward movement relative to the frame in response to periodic changes in pressure differential between the vena cava and the pulmonary artery. [Aspect 50] a motor configured to drive the impeller to rotate the impeller in a given direction of rotation, thereby pumping blood through the subject's body; a drive cable configured to extend from outside the subject's body to the axial shaft, the drive cable configured to rotate to impart rotational motion from the motor to the impeller, at least a portion of the drive cable including a plurality of wires arranged in a coiled configuration, the coiled configuration such that in response to the drive cable rotating in the given direction of rotation, the plurality of wires arranged in the coiled configuration at least partially unwind, causing the portion of the drive cable to axially shorten; 44. The apparatus of embodiment 43, further comprising: [Aspect 51] The apparatus of embodiment 43, wherein the impeller is coupled to the axial shaft such that the impeller causes the axial shaft to undergo axial forward and backward movement relative to the proximal and distal bearings of the frame. [Aspect 52] The device of aspect 51, wherein the axial shaft is configured to clean an interface between the axial shaft and the proximal and distal bearings of the frame by undergoing an axial forward and backward movement relative to the proximal and distal bearings of the frame. [Aspect 53] The device of aspect 51, wherein the axial shaft is configured to experience axial forward and backward movement relative to the proximal and distal bearings of the frame, as opposed to the case in which the axial shaft does not experience the axial forward and backward movement relative to the proximal and distal bearings of the frame, thereby reducing heating at the interface between the axial shaft and the proximal and distal bearings of the frame. [Aspect 54] An apparatus, comprising: Including a blood pump, The blood pump comprises: an impeller configured to be placed inside a body of a subject and configured to pump blood through the body of the subject; a frame configured to be disposed around the impeller; and Including, The apparatus, wherein the blood pump does not include any thrust bearing configured to be disposed within the subject's body. [Aspect 55] The apparatus of aspect 54, wherein the blood pump further includes one or more thrust bearings configured to be disposed outside the subject's body, and opposition to the thrust generated by rotation of the impeller is provided solely by the one or more thrust bearings disposed outside the subject's body. [Aspect 56] a sensor configured to detect an indication of axial movement of the impeller and to generate a sensor signal in response thereto; and a computer processor configured to receive the sensor signal and to generate an output in response thereto. Processor and 56. The apparatus of embodiment 54 or embodiment 55, further comprising: [Aspect 57] 57. The apparatus of embodiment 56, wherein the computer processor is configured to generate an output indicative of the subject's cardiac cycle in response to receiving the sensor signal. [Aspect 58] 57. The apparatus of embodiment 56, wherein the computer processor is configured to determine left ventricular pressure of the subject based at least in part on the sensor signal. [Aspect 59] 57. The apparatus of embodiment 56, wherein the computer processor is configured to vary the rotational speed of the impeller based at least in part on the sensor signal. [Aspect 60] The computer processor includes: configured to determine a left ventricular pressure of the subject based at least in part on the sensor signal; 60. The apparatus of embodiment 59, further configured to vary the rotational speed of the impeller based at least in part on the determined left ventricular pressure. [Aspect 61] The apparatus of embodiment 60, wherein the computer processor is configured to reduce the rotational speed of the impeller in response to determining that the subject's left ventricular pressure has decreased. [Aspect 62] a magnet, the impeller being coupled to the magnet such that axial movement of the impeller causes the magnet to experience axial movement; a sensor configured to detect magnetic flux generated by the magnet and to generate a sensor signal in response thereto; and a computer processor configured to receive the sensor signal and to generate an output in response thereto; 56. The apparatus of embodiment 54 or embodiment 55, further comprising: [Aspect 63] 63. The apparatus of embodiment 62, wherein the computer processor is configured to generate an output indicative of the subject's cardiac cycle in response to receiving the sensor signal. [Aspect 64] 63. The apparatus of embodiment 62, wherein the computer processor is configured to determine a left ventricular pressure of the subject based at least in part on the sensor signal. [Aspect 65] 63. The apparatus of embodiment 62, wherein the computer processor is configured to vary the rotational speed of the impeller based at least in part on the sensor signal. [Aspect 66] The computer processor includes: configured to determine a left ventricular pressure of the subject based at least in part on the sensor signal; a rotational speed of the impeller based at least in part on the determined left ventricular pressure; 66. The apparatus of embodiment 65, configured to vary [Aspect 67] 67. The apparatus of embodiment 66, wherein the computer processor is configured to reduce the rotational speed of the impeller in response to determining that the subject's left ventricular pressure has decreased. [Aspect 68] The apparatus of claim 54 or 55, wherein the impeller is configured to pump blood from a first location within the subject's body to a second location within the subject's body, and the impeller is configured to undergo axial forward and backward movement relative to the frame in response to periodic changes in pressure differential between the first location and the second location. [Aspect 69] The apparatus of aspect 68, wherein the impeller is configured to pump blood from the subject's left ventricle to the subject's aorta, and the impeller is configured to undergo axial forward and backward movement relative to the frame in response to periodic changes in pressure differential between the left ventricle and the aorta. [Aspect 70] The apparatus of aspect 68, wherein the impeller is configured to pump blood from the subject's right ventricle to the subject's pulmonary artery, and the impeller is configured to undergo axial forward and backward movement relative to the frame in response to periodic changes in pressure differential between the right ventricle and the pulmonary artery. [Aspect 71] The apparatus of aspect 68, wherein the impeller is configured to pump blood from the subject's right atrium to the subject's right ventricle, and the impeller is configured to undergo axial forward and backward movement relative to the frame in response to periodic changes in pressure differential between the right atrium and the right ventricle. [Aspect 72] The apparatus of embodiment 68, wherein the impeller is configured to pump blood from the subject's vena cava to the subject's right ventricle, and the impeller is configured to undergo axial forward and backward movement relative to the frame in response to periodic changes in pressure differential between the vena cava and the right ventricle. [Aspect 73] The apparatus of aspect 68, wherein the impeller is configured to pump blood from the subject's right atrium to the subject's pulmonary artery, and the impeller is configured to undergo axial forward and backward movement relative to the frame in response to periodic changes in pressure differential between the right atrium and the pulmonary artery. [Aspect 74] The apparatus of embodiment 68, wherein the impeller is configured to pump blood from the subject's vena cava to the subject's pulmonary artery, and the impeller is configured to undergo axial forward and backward movement relative to the frame in response to periodic changes in pressure differential between the vena cava and the pulmonary artery. [Aspect 75] a motor configured to drive the impeller to rotate the impeller in a given direction of rotation, thereby pumping blood through the subject's body; an axial shaft, the impeller being coupled to the axial shaft; a drive cable configured to extend from outside the subject's body to the axial shaft, the drive cable configured to rotate to impart rotational motion from the motor to the impeller, at least one of the drive cables being configured to extend from the subject's body to the axial shaft; a drive cable, a portion of which includes a plurality of wires arranged in a coiled configuration, the coiled configuration being such that in response to the drive cable rotating in the given direction of rotation, the plurality of wires arranged in the coiled configuration at least partially unwind and the portion of the drive cable is axially shortened; 69. The apparatus of embodiment 68, further comprising: [Aspect 76] the impeller includes a proximal bushing and a distal bushing; the frame includes a proximal bearing and a distal bearing; The apparatus further includes an axial shaft; the axial shaft passes through the proximal and distal bearings defined by the frame and the proximal and distal bushings of the impeller; the axial shaft is coupled to at least one of the proximal and distal bushings of the impeller such that the at least one bushing is held in an axially fixed position relative to the axial shaft; the axial shaft is not held in an axially fixed position relative to the proximal and distal bearings; The apparatus of embodiment 68, wherein the impeller is adapted to cause the axial shaft to undergo axial forward and backward movement relative to the proximal and distal bearings of the frame. [Aspect 77] The apparatus of aspect 76, wherein the axial shaft is configured to clean an interface between the axial shaft and the proximal and distal bearings of the frame by undergoing an axial forward and backward movement relative to the proximal and distal bearings of the frame. [Aspect 78] The device of aspect 76, wherein the axial shaft is configured to experience axial forward and backward movement relative to the proximal and distal bearings of the frame, as opposed to the case in which the axial shaft does not experience the axial forward and backward movement relative to the proximal and distal bearings of the frame, thereby reducing heating at the interface between the axial shaft and the proximal and distal bearings of the frame.

Claims

1. An apparatus, comprising: ventricular assist devices, The ventricular assist device comprises: an impeller configured to be placed inside the left ventricle of the subject; a frame configured to be disposed around the impeller; a motor configured to drive the impeller to rotate the impeller and thereby pump blood from the left ventricle to the aorta of the subject; Including, the entire impeller is configured to undergo axial forward and backward movement relative to the frame in response to cyclic changes in pressure differential between the left ventricle and the aorta; the impeller includes a proximal bushing and a distal bushing; the frame includes a proximal bearing and a distal bearing; The ventricular assist device further includes an axial shaft configured to pass through the proximal and distal bearings defined by the frame and the proximal and distal bushings of the impeller; the axial shaft is coupled to at least one of the proximal and distal bushings of the impeller such that the at least one bushing is held in an axially fixed position relative to the axial shaft; The device, wherein the axial shaft is not held in an axially fixed position relative to the proximal and distal bearings.

2. The apparatus of claim 1 , wherein the ventricular assist device does not include any thrust bearings configured to be disposed within the subject's body.

3. An apparatus, comprising: ventricular assist devices, The ventricular assist device comprises: an impeller configured to be placed inside the left ventricle of the subject; a frame configured to be disposed around the impeller; a motor configured to drive the impeller to rotate the impeller and thereby pump blood from the left ventricle to the aorta of the subject; Including, the entire impeller is configured to undergo axial forward and backward movement relative to the frame in response to cyclic changes in pressure differential between the left ventricle and the aorta; the ventricular assist device further includes one or more thrust bearings configured to be disposed outside the subject's body, and opposition to thrust generated by rotation of the impeller is provided solely by the one or more thrust bearings disposed outside the subject's body.

4. An apparatus, comprising: ventricular assist devices, The ventricular assist device comprises: an impeller configured to be placed inside the left ventricle of the subject; a frame configured to be disposed around the impeller; a motor configured to drive the impeller to rotate the impeller and thereby pump blood from the left ventricle to the aorta of the subject; Including, the entire impeller is configured to undergo axial forward and backward movement relative to the frame in response to cyclic changes in pressure differential between the left ventricle and the aorta; the motor is configured to drive the impeller to rotate the impeller in a given direction of rotation to pump blood from a left ventricle of the subject to an aorta of the subject; The ventricular assist device comprises: an axial shaft, the impeller being disposed on the axial shaft; a drive cable configured to extend from outside the subject's body to the axial shaft, the drive cable configured to rotate to impart rotational motion from the motor to the impeller, at least a portion of the drive cable including a plurality of wires arranged in a coiled configuration, the coiled configuration such that in response to the drive cable rotating in the given direction of rotation, the plurality of wires arranged in the coiled configuration at least partially unwind, causing the portion of the drive cable to axially shorten; The apparatus further comprising:

5. An apparatus, comprising: ventricular assist devices, The ventricular assist device comprises: an impeller configured to be placed inside the left ventricle of the subject; a frame configured to be disposed around the impeller; a motor configured to drive the impeller to rotate the impeller and thereby pump blood from the left ventricle to the aorta of the subject; Including, the entire impeller is configured to undergo axial forward and backward movement relative to the frame in response to cyclic changes in pressure differential between the left ventricle and the aorta; a sensor configured to detect an indication of axial movement of the impeller and to generate a sensor signal in response thereto; and a computer processor configured to receive the sensor signal and to generate an output in response thereto; The apparatus further comprising:

6. The apparatus of claim 5 , wherein the computer processor is configured to vary a rotational speed of the impeller based at least in part on the sensor signal.

7. An apparatus, comprising: ventricular assist devices, The ventricular assist device comprises: an impeller configured to be placed inside the left ventricle of the subject; a frame configured to be disposed around the impeller; a motor configured to drive the impeller to rotate the impeller and thereby pump blood from the left ventricle to the aorta of the subject; Including, the entire impeller is configured to undergo axial forward and backward movement relative to the frame in response to cyclic changes in pressure differential between the left ventricle and the aorta; a magnet, the impeller being coupled to the magnet such that axial movement of the impeller causes the magnet to experience axial movement; a sensor configured to detect magnetic flux generated by the magnet and to generate a sensor signal in response thereto; and a computer processor configured to receive the sensor signal and to generate an output in response thereto; The apparatus further comprising:

8. The apparatus of claim 7 , wherein the computer processor is configured to vary a rotational speed of the impeller based at least in part on the sensor signal.

9. An apparatus, comprising: ventricular assist devices, The ventricular assist device comprises: an impeller configured to be placed inside the left ventricle of the subject; a frame configured to be disposed around the impeller; a motor configured to drive the impeller to rotate the impeller and thereby pump blood from the left ventricle to the aorta of the subject; Including, the entire impeller is configured to undergo axial forward and backward movement relative to the frame in response to cyclic changes in pressure differential between the left ventricle and the aorta; the impeller includes a proximal bushing and a distal bushing; the frame includes a proximal bearing and a distal bearing; the ventricular assist device further includes an axial shaft configured to pass through the proximal and distal bearings of the frame and the proximal and distal bushings of the impeller; The impeller is coupled to the axial shaft such that the impeller causes the axial shaft to undergo axial forward and backward movement relative to the proximal and distal bearings of the frame.

10. 10. The device of claim 9, wherein the axial shaft is configured to undergo an axial forward and backward movement relative to the proximal and distal bearings of the frame to clear an interface between the axial shaft and the proximal and distal bearings of the frame.

11. 10. The apparatus of claim 9, wherein the axial shaft is configured to experience axial forward and backward movement relative to the proximal and distal bearings of the frame, relative to a case in which the axial shaft does not experience the axial forward and backward movement relative to the proximal and distal bearings of the frame, thereby reducing heating at an interface between the axial shaft and the proximal and distal bearings of the frame.

12. An apparatus, comprising: Including a blood pump, The blood pump comprises: an impeller including a proximal bushing and a distal bushing, the impeller configured to pump blood through a body of a subject; a frame configured to be disposed about the impeller, the frame including a proximal bearing and a distal bearing; an axial shaft configured to pass through the proximal and distal bearings of the frame and the proximal and distal bushings of the impeller; Including, the axial shaft is coupled to at least one of the proximal and distal bushings of the impeller such that the at least one bushing is held in an axially fixed position relative to the axial shaft; The device, wherein the axial shaft is not held in an axially fixed position relative to the proximal and distal bearings.

13. An apparatus, comprising: Including a blood pump, The blood pump comprises: an impeller configured to be placed inside a body of a subject and configured to pump blood through the body of the subject; a frame configured to be disposed around the impeller; and Including, the blood pump does not include any thrust bearing configured to be disposed within a body of the subject; The blood pump further comprises one or more thrust bearings configured to be disposed outside the subject's body, and opposition to thrust generated by rotation of the impeller is provided solely by the one or more thrust bearings disposed outside the subject's body.

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