Ventricular assist device

Abstract

This application relates to ventricular assist devices. Devices and methods are described herein, including a blood pump (20) configured to be placed within a subject's body, the blood pump including an impeller (50) and a frame (34) disposed around the impeller, the impeller including a proximal bushing and a distal bushing (64, 58), and the frame including a proximal bearing and a distal bearing (116, 118). An axial shaft (92) passes through the proximal bearing and the distal bearing (116, 118) of the frame and the proximal bushing and the distal bushing (64, 58) of the impeller (50). The impeller (50) defines a radially constrained configuration in which the impeller (50) is introduced into the subject's body and a non-radially constrained configuration in which the impeller (50) is configured to pump blood within the subject's body. By sliding the distal bushing (58) along the axial shaft (92), the impeller (50) changes from its radially constrained configuration to its non-radially constrained configuration. Other applications are also described herein.

Description

[0001] This application is a divisional application of an application with an application date of January 10, 2019, an application number of 201980007116.9, and an invention title of "Ventricular Assist Device".

[0002] Cross-reference to related applications

[0003] This application claims priority to the following applications:

[0004] U.S. Provisional Patent Application 62 / 615,538, filed on January 10, 2018, by Sohn, entitled "Ventricular assist device";

[0005] U.S. Provisional Patent Application 62 / 665,718, filed on May 2, 2018, by Sohn, entitled "Ventricular assist device";

[0006] U.S. Provisional Patent Application 62 / 681,868, filed on June 7, 2018, by Tuval, entitled "Ventricular assist device"; and

[0007] U.S. Provisional Patent Application 62 / 727,605, filed on September 6, 2018, by Tuval, entitled "Ventricular assist device".

[0008] All of the above-referenced applications are hereby incorporated by reference.

[0009] Field of embodiments of the invention

[0010] Some applications of the present invention generally relate to medical devices. Specifically, some applications of the present invention relate to ventricular assist devices and methods of using the same. Background

[0011] Ventricular assist devices are mechanical circulatory support devices that are designed to assist the heart chambers and reduce the burden on the heart chambers to maintain or increase cardiac output. They are used in patients with failing hearts and in patients at risk of deteriorating cardiac function during percutaneous coronary intervention. Most commonly, left ventricular assist devices are applied to defective hearts to assist left ventricular function. In some cases, right ventricular assist devices are used to assist right ventricular function. Such assist devices are designed to be permanently implanted or mounted on a catheter for temporary placement.

[0012] Summary of embodiments

[0013] In some applications according to the present invention, a ventricular assist device includes an impeller disposed on an axial axis, and a frame is disposed around the impeller. The ventricular assist device generally includes a tube that passes through the aortic valve of a subject such that a proximal end of the tube is disposed in the aorta of the subject and a distal end of the tube is disposed in the left ventricle of the subject. The impeller, axial axis, and frame are disposed within a distal portion of the tube in the left ventricle of the subject. Generally, the impeller is configured to pump blood from the left ventricle into the aorta by rotation. The tube generally defines one or more blood inlet openings at the distal end of the tube, and during operation of the impeller, blood flows into the tube from the left ventricle via the inlet openings. For some applications, a proximal portion of the tube defines one or more blood outlet openings, and during operation of the impeller, blood flows from the tube into the ascending aorta via the outlet openings.

[0014] 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 axis generally passes through the proximal bearing and the distal bearing of the frame and the proximal bushing and the distal bushing of the impeller. For some applications, (a) the proximal bushing of the impeller is coupled to the axial axis such that the proximal bushing remains in an axially fixed position relative to the axial axis, and (b) the distal bushing of the impeller is not coupled to the axial axis such that the distal bushing does not remain in an axially fixed position relative to the axial axis. Generally, the impeller defines a radially constrained configuration and a non-radially constrained configuration, in the radially constrained configuration, the impeller is introduced into the body of the subject, and in the non-radially constrained configuration, the impeller is configured to pump blood within the body of the subject. For some applications, by sliding the distal bushing on the axial axis, the impeller changes from its radially constrained configuration to its non-radially constrained configuration.

[0015] Generally, the axial axis does not remain in an axially fixed position relative to the proximal bearing and the distal bearing. Additionally, generally, the ventricular assist device (and / or its blood pump portion) does not include any thrust bearings configured to be disposed within the body of the subject. For some applications, the ventricular assist device includes one or more thrust bearings disposed outside the body of the subject, and the counteraction of the thrust generated by the rotation of the impeller is provided only by the one or more thrust bearings disposed outside the body of the subject.

[0016] For some applications, the motor drives the impeller by rotating the impeller to pump blood from the left ventricle to the aorta, and the impeller is configured to move axially relative to the frame in response to changes in the pressure differential between the left ventricle and the aorta. For some applications, a computer processor measures an indication of the axial movement 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 movement of the impeller. For some applications, the computer processor changes the rotational speed of the impeller at least in part based on a sensor signal. For example, the computer processor can determine the subject's left ventricular pressure at least in part based on the sensor signal, and can change the rotational speed of the impeller at least in part based 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 axial movement of the magnet, and the computer processor measures an indication of the axial movement of the impeller by measuring the magnetic flux generated by the magnet.

[0017] Typically, a drive cable extends from outside the subject's body to the axial axis and is configured to transfer rotational movement from the motor to the impeller by rotation such that the impeller pumps blood from the left ventricle to the aorta by rotating in a given direction. For some applications, at least a portion of the drive cable includes multiple wires arranged in a coiled configuration such that in response to the drive cable rotating in a given rotational direction, the multiple wires arranged in the coiled configuration at least partially unwind such that that portion of the drive cable axially shortens. For some applications, an outer tube is disposed around the drive cable, and friction between the outer tube and the drive cable typically generates debris. Optionally or additionally, a fluid (e.g., a cleansing fluid) is disposed between the outer tube and the drive cable. For some such applications, at least a portion of the drive cable is configured such that the multiple wires arranged in the coiled configuration are configured to pump debris and / or fluid toward the proximal end of the drive cable.

[0018] For some applications, the drive cable includes a first portion and a second portion, the first portion being configured to be disposed at least in part within the subject's aortic arch, the second portion being configured to be disposed at least in part within the subject's descending aorta, and the first portion being more flexible than 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, and the first number is lower 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.

[0019] For some applications, the impeller includes at least one helical elongate element (and typically three helical elongate elements), and a spring disposed interior to the helical elongate element and along the axis about which the helical elongate element is wound. Typically, a membrane of a 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 cord 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.

[0020] As described above, for some applications, a frame is disposed about the impeller. For some applications, the ventricular assist device includes a stator that includes a plurality of curved protrusions coupled to a proximal end of the frame. Typically, the curvature of the curved protrusions is opposite to the direction of rotation of the impeller. For some applications, the curvature of the curved protrusions is such that from a distal end of the curved protrusion to a proximal end of the curved protrusion, the curved protrusion gradually becomes closer to being parallel to the longitudinal axis of the frame. Typically, the curved protrusions 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.

[0021] As described above, typically the impeller is disposed within a tube (sometimes referred to herein as a "blood pump tube") that extends from a left ventricle of a subject to the aorta of the subject. For some applications, at least one blood pressure measurement tube (that defines an opening at its distal end) extends to at least an outer surface of the blood 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 external to the blood pump tube. A pressure sensor measures the blood pressure within the blood pressure measurement tube. For some applications, the blood pressure measurement tube is configured to pass along the outer surface of the blood pump tube from a proximal end of the blood pump tube until 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 that is configured to extend to the outer surface of the blood pump tube at a location along the blood pump tube proximate the impeller and within the left ventricle of the subject, and the pressure sensor is configured to measure the left ventricular pressure of the subject by measuring the blood pressure within the left ventricular blood pressure measurement tube.

[0022] Typically, a blood pump tube defines one or more blood inlet openings within a distal portion of the blood pump tube and one or more blood outlet openings within a proximal portion of the blood pump tube. For some applications, a ventricular assist device includes a radially expandable atraumatic distal end portion configured to be disposed distally relative to the one or more blood inlet openings within a left ventricle of a subject. The distal end portion is typically configured to be inserted into the left ventricle in a radially constrained configuration and to assume a non-radially constrained configuration within the left ventricle of the subject, wherein at least a radially expandable portion of the distal end portion radially expands relative to the radially constrained configuration of the distal end portion. Typically, in its non-radially constrained configuration, the radially expandable portion of the distal end portion separates the one or more blood inlet openings from internal structures of the left ventricle such as the interventricular septum, chordae tendineae, papillary muscles, and / or the apex of the left ventricle. Additionally, typically, in its non-radially constrained configuration, the radially expandable portion of the distal end portion separates the one or more blood inlet openings from the internal structures of the left ventricle in three dimensions. For some applications, in its non-radially constrained configuration, the radially expandable portion of the distal end portion directs blood flow from the left ventricle into the one or more blood inlet openings.

[0023] For some applications, in the radially constrained configuration of the distal end portion, a distal region of the distal end portion is configured to be at least semi-rigid and is shaped to radially converge along a longitudinal direction toward a distal end of the distal end portion. Typically, the ventricular assist device is configured to be inserted into a subject's body via a puncture in the subject's body. For some applications, during insertion of the ventricular assist device, the distal region of the distal end portion is configured to act as a dilator by enlarging the puncture.

[0024] Generally, in the specification and claims of the present application, the terms "proximal" and related terms, when used in reference to a device or a part thereof, shall be construed to mean the end or part of the device that is typically closer to the location through which the device is inserted into the subject's body when inserted into the subject's body. The terms "distal" and related terms, when used in reference to a device or a part thereof, shall be construed to mean the end or part of the device that is typically farther from the location through which the device is inserted into the subject's body when inserted into the subject's body.

[0025] The scope of the present invention includes the use of the devices and methods described herein in anatomical locations other than the left ventricle and the aorta. Accordingly, the ventricular assist device and / or parts thereof are sometimes referred to herein (in the specification and claims) as a blood pump.

[0026] According to some applications of the present invention, there is also provided a device comprising:

[0027] A blood pump configured to be placed within a subject's body, the blood pump comprising:

[0028] An impeller, the impeller comprising a proximal bushing and a distal bushing;

[0029] A frame configured to be disposed around the impeller, the frame comprising a proximal bearing and a distal bearing;

[0030] An axial shaft configured to pass through the proximal bearing and the distal bearing of the frame and the proximal bushing and the distal bushing of the impeller,

[0031] The proximal bushing of the impeller is coupled to the axial shaft such that the proximal bushing remains in an axially fixed position relative to the axial shaft, and

[0032] The distal bushing of the impeller is not coupled to the axial shaft such that the distal bushing does not remain in an axially fixed position relative to the axial shaft, and

[0033] The impeller defines a radially constrained configuration and a non-radially constrained configuration, in which the impeller is introduced into the subject's body in the radially constrained configuration and in which the impeller is configured to pump blood within the subject's body in the non-radial configuration, the impeller being configured to change from its radially constrained configuration to its non-radially constrained configuration by sliding on the axial shaft through the distal bushing.

[0034] In some applications, the impeller is configured to be placed within the left ventricle of a subject and is configured to pump blood from the left ventricle of the subject to the aorta of the subject. In some applications, the impeller is configured to be placed within the right ventricle of a subject and is configured to pump blood from the right ventricle of the subject to the pulmonary artery of the subject. In some applications, the impeller is configured to be placed within a blood vessel of a subject. In some applications, the impeller is configured to be placed within a heart chamber of a subject.

[0035] In some applications, the impeller comprises:

[0036] At least one helical elongate element extending from the proximal bushing to the distal bushing;

[0037] A spring disposed within the helical elongate element and along an axis about which the helical elongate element is wound;

[0038] A membrane of a material supported between the helical elongate element and the spring; and

[0039] 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.

[0040] In some applications, the device further includes a delivery catheter,

[0041] The delivery catheter being configured to maintain the impeller in its radially constrained configuration during introduction of the impeller into a subject's body,

[0042] When the impeller is released from the delivery catheter, the impeller is configured to self-expand, thereby causing the distal bushing to slide proximally along the axial axis such that the impeller assumes its non-radially constrained configuration, and

[0043] To retract the impeller from the subject's body, the delivery catheter is configured to move the distal end of the delivery catheter and the impeller relative to each other such that the distal end of the delivery catheter causes the distal bushing to slide distally along the axial axis, causing the impeller to assume its radially constrained configuration.

[0044] In some applications according to the present invention, there is also provided a device, the device comprising:

[0045] A ventricular assist device, the ventricular assist device comprising:

[0046] An impeller configured to be placed within the left ventricle of a subject;

[0047] A frame configured to be disposed around the impeller; and

[0048] A motor configured to drive the impeller by rotating the impeller to pump blood from the left ventricle to the aorta of the subject,

[0049] The impeller being configured to move axially back and forth relative to the frame in response to periodic variations in the pressure differential between the left ventricle and the aorta.

[0050] In some applications:

[0051] The impeller includes a proximal bushing and a distal bushing;

[0052] The frame includes a proximal bearing and a distal bearing; and

[0053] The ventricular assist device further includes an axial shaft configured to pass through the proximal bearing and the distal bearing defined by the frame and the proximal bushing and the distal bushing of the impeller, the axial shaft:

[0054] At least one of the proximal bushing and the distal bushing coupled to the impeller such that the at least one bushing is held in an axially fixed position relative to the axial axis, and

[0055] is not held in an axially fixed position relative to the proximal bearing and the distal bearing.

[0056] In some applications, the ventricular assist device does not include any thrust bearings configured to be disposed within the body of a subject.

[0057] In some applications, the ventricular assist device further includes one or more thrust bearings configured to be disposed external to the body of a subject, and wherein counteraction of the thrust generated by rotation of the impeller is provided only by the one or more thrust bearings disposed external to the body of the subject.

[0058] In some applications,

[0059] the motor is configured to drive the impeller to pump blood from the left ventricle of a subject to the aorta of the subject by rotating the impeller in a given direction of rotation; and

[0060] the ventricular assist device further includes:

[0061] an axial axis on which the impeller is disposed; and

[0062] a drive cable configured to extend from external to the body of the subject to the axial axis, the drive cable configured to transmit rotational movement from the motor to the impeller by rotation, at least a portion of the drive cable including multiple wires disposed in a coiled configuration such that in response to rotation of the drive cable in the given direction of rotation, the multiple wires disposed in the coiled configuration at least partially unwind such that the portion of the drive cable axially shortens.

[0063] In some applications, the device further includes:

[0064] a sensor configured to detect an indication of axial movement of the impeller and configured to generate a sensor signal in response thereto; and

[0065] a computer processor configured to receive the sensor signal and configured to generate an output in response thereto.

[0066] In 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. In some applications, the computer processor is configured to determine the left ventricular pressure of the subject at least in part based on the sensor signal. In some applications, the computer processor is configured to change the rotational speed of the impeller at least in part based on the sensor signal.

[0067] In some applications, the computer processor is configured to:

[0068] determine the left ventricular pressure of the subject at least in part based on the sensor signal, and

[0069] change the rotational speed of the impeller at least in part based on the determined left ventricular pressure.

[0070] In some applications, the computer processor is configured to reduce the rotational speed of the impeller in response to determining that the left ventricular pressure of the subject has decreased.

[0071] In some applications, the device further comprises:

[0072] a magnet, the impeller being coupled to the magnet such that axial movement of the impeller causes axial movement of the magnet;

[0073] a sensor configured to detect the magnetic flux generated by the magnet and configured to generate a sensor signal in response thereto; and

[0074] a computer processor configured to receive the sensor signal and configured to generate an output in response thereto.

[0075] In 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. In some applications, the computer processor is configured to determine the left ventricular pressure of the subject at least in part based on the sensor signal. In some applications, the computer processor is configured to change the rotational speed of the impeller at least in part based on the sensor signal.

[0076] In some applications, the computer processor is configured to:

[0077] determine the left ventricular pressure of the subject at least in part based on the sensor signal, and

[0078] change the rotational speed of the impeller at least in part based on the determined left ventricular pressure.

[0079] In some applications, the computer processor is configured to reduce the rotational speed of the impeller in response to determining that the left ventricular pressure of the subject has decreased.

[0080] In some applications:

[0081] The impeller includes a proximal bushing and a distal bushing;

[0082] The frame includes a proximal bearing and a distal bearing;

[0083] The ventricular assist device further includes an axial shaft configured to pass through the proximal bearing and the distal bearing of the frame and the proximal bushing and the distal bushing of the impeller;

[0084] The impeller is coupled to the axial shaft such that the impeller causes the axial shaft to move axially back and forth relative to the proximal bearing and the distal bearing of the frame.

[0085] In some applications, the axial shaft is configured to clean the interface between the axial shaft and the proximal bearing and the distal bearing of the frame by making the axial back-and-forth movement relative to the proximal bearing and the distal bearing of the frame. In some applications, the axial shaft is configured to reduce heat accumulation at the interface between the axial shaft and the proximal bearing and the distal bearing of the frame by making the axial back-and-forth movement relative to the proximal bearing and the distal bearing of the frame, as compared to the case where the axial shaft does not make the axial back-and-forth movement relative to the proximal bearing and the distal bearing of the frame.

[0086] According to some applications of the present invention, an apparatus is further provided, the apparatus including:

[0087] A blood pump, the blood pump including:

[0088] An impeller, the impeller including a proximal bushing and a distal bushing and configured to pump blood through the body of a subject;

[0089] A frame configured to be disposed around the impeller, the frame including a proximal bearing and a distal bearing;

[0090] An axial shaft configured to pass through the proximal bearing and the distal bearing of the frame and the proximal bushing and the distal bushing of the impeller, the axial shaft:

[0091] Is coupled to at least one of the proximal bushing and the distal bushing of the impeller such that the at least one bushing remains in an axially fixed position relative to the axial shaft, and

[0092] is not held in an axially fixed position relative to the proximal bearing and the distal bearing.

[0093] In some applications, the blood pump does not include any thrust bearings configured to be disposed within a subject's body. In some applications, where the blood pump further includes one or more thrust bearings, the one or more thrust bearings are configured to be disposed outside the subject's body, and where counteraction of the thrust generated by rotation of the impeller is provided only by the one or more thrust bearings disposed outside the subject's body.

[0094] In some applications, the device further includes:

[0095] a sensor configured to detect an indication of axial movement of the impeller and configured to generate a sensor signal in response thereto; and

[0096] a computer processor configured to receive the sensor signal and configured to generate an output in response thereto.

[0097] In some applications, the computer processor is configured to generate an output indicative of a subject's cardiac cycle in response to receiving the sensor signal. In some applications, the computer processor is configured to determine a subject's left ventricular pressure at least in part based on the sensor signal. In some applications, the computer processor is configured to change a rotational rate of the impeller at least in part based on the sensor signal.

[0098] In some applications, the computer processor is configured to:

[0099] determine a subject's left ventricular pressure at least in part based on the sensor signal, and

[0100] change a rotational rate of the impeller at least in part based on the determined left ventricular pressure.

[0101] In some applications, the computer processor is configured to reduce the rotational rate of the impeller in response to determining that a subject's left ventricular pressure has decreased.

[0102] In some applications, the device further includes:

[0103] a magnet, the impeller being coupled to the magnet such that axial movement of the impeller causes axial movement of the magnet;

[0104] a sensor configured to detect magnetic flux generated by the magnet and configured to generate a sensor signal in response thereto; and

[0105] A computer processor configured to receive the sensor signal and configured to generate an output in response thereto.

[0106] In some applications, the computer processor is configured to generate an output indicative of a subject's cardiac cycle in response to receiving the sensor signal. In some applications, the computer processor is configured to determine a subject's left ventricular pressure at least in part based on the sensor signal. In some applications, the computer processor is configured to change a rotational rate of the impeller at least in part based on the sensor signal.

[0107] In some applications, the computer processor is configured to:

[0108] Determine a subject's left ventricular pressure at least in part based on the sensor signal, and

[0109] Change a rotational rate of the impeller at least in part based on the determined left ventricular pressure.

[0110] In some applications, the computer processor is configured to reduce the rotational rate of the impeller in response to determining that a subject's left ventricular pressure has decreased.

[0111] In some applications, the impeller is configured to pump blood from a first location within a subject's body to a second location within the subject's body, and the impeller is configured to move axially back and forth relative to the frame in response to a periodic change in the pressure differential between the first location and the second location. In some applications, the impeller is configured to pump blood from the left ventricle of the subject to the aorta of the subject, and the impeller is configured to move axially back and forth relative to the frame in response to a periodic change in the pressure differential between the left ventricle and the aorta. In some applications, the impeller is configured to pump blood from the right ventricle of the subject to the pulmonary artery of the subject, and the impeller is configured to move axially back and forth relative to the frame in response to a periodic change in the pressure differential between the right ventricle and the pulmonary artery. In some applications, the impeller is configured to pump blood from the right atrium of the subject to the right ventricle of the subject, and the impeller is configured to move axially back and forth relative to the frame in response to a periodic change in the pressure differential between the right atrium and the right ventricle. In some applications, the impeller is configured to pump blood from the vena cava of the subject to the right ventricle of the subject, and the impeller is configured to move axially back and forth relative to the frame in response to a periodic change in the pressure differential between the vena cava and the right ventricle. In some applications, the impeller is configured to pump blood from the right atrium of the subject to the pulmonary artery of the subject, and the impeller is configured to move axially back and forth relative to the frame in response to a periodic change in the pressure differential between the right atrium and the pulmonary artery. In some applications, the impeller is configured to pump blood from the vena cava of the subject to the pulmonary artery of the subject, and the impeller is configured to move axially back and forth relative to the frame in response to a periodic change in the pressure differential between the vena cava and the pulmonary artery.

[0112] In some applications, the device further comprises:

[0113] a motor configured to drive the impeller to pump blood through the subject's body by rotating the impeller in a given rotational direction; and

[0114] a drive cable configured to extend from outside the subject's body to the axial shaft, the drive cable being configured to transmit rotational movement from the motor to the impeller by rotation, at least a portion of the drive cable comprising multiple wires arranged in a coiled configuration such that in response to rotation of the drive cable in the given rotational direction, the multiple wires arranged in the coiled configuration at least partially unwind, causing the portion of the drive cable to shorten axially.

[0115] In some applications, the impeller is coupled to the axial shaft such that the impeller causes the axial shaft to move axially back and forth relative to the proximal bearing and the distal bearing of the frame. In some applications, the axial shaft is configured to clean the junction between the axial shaft and the proximal bearing and the distal bearing of the frame by making the axial back-and-forth movement relative to the proximal bearing and the distal bearing of the frame. In some applications, the axial shaft is configured to reduce heat accumulation at the junction between the axial shaft and the proximal bearing and the distal bearing of the frame by making the axial back-and-forth movement relative to the proximal bearing and the distal bearing of the frame as compared to the case where the axial shaft does not make the axial back-and-forth movement relative to the proximal bearing and the distal bearing of the frame.

[0116] According to some applications of the present invention, there is also provided an apparatus, the apparatus comprising:

[0117] A blood pump, the blood pump comprising:

[0118] An impeller configured to be placed within a subject's body and configured to pump blood through the subject's body;

[0119] A frame configured to be disposed around the impeller,

[0120] The blood pump does not include any thrust bearings configured to be disposed within the subject's body.

[0121] In some applications, the blood pump further includes one or more thrust bearings configured to be disposed outside the subject's body, and the counteraction to the thrust generated by the rotation of the impeller is provided only by the one or more thrust bearings disposed outside the subject's body.

[0122] In some applications, the apparatus further includes:

[0123] A sensor configured to detect an indication of the axial movement of the impeller and configured to generate a sensor signal in response thereto; and

[0124] A computer processor configured to receive the sensor signal and configured to generate an output in response thereto.

[0125] In 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. In some applications, the computer processor is configured to determine the left ventricular pressure of the subject at least in part based on the sensor signal. In some applications, the computer processor is configured to change the rotational speed of the impeller at least in part based on the sensor signal.

[0126] In some applications, the computer processor is configured to:

[0127] determine the left ventricular pressure of the subject at least in part based on the sensor signal, and

[0128] change the rotational speed of the impeller at least in part based on the determined left ventricular pressure.

[0129] In some applications, the computer processor is configured to reduce the rotational speed of the impeller in response to determining that the left ventricular pressure of the subject has decreased.

[0130] In some applications, the device further comprises:

[0131] a magnet, the impeller being coupled to the magnet such that axial movement of the impeller causes axial movement of the magnet;

[0132] a sensor configured to detect the magnetic flux generated by the magnet and configured to generate a sensor signal in response thereto; and

[0133] a computer processor configured to receive the sensor signal and configured to generate an output in response thereto.

[0134] In 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. In some applications, the computer processor is configured to determine the left ventricular pressure of the subject at least in part based on the sensor signal. In some applications, the computer processor is configured to change the rotational speed of the impeller at least in part based on the sensor signal.

[0135] In some applications, the computer processor is configured to:

[0136] determine the left ventricular pressure of the subject at least in part based on the sensor signal, and

[0137] change the rotational speed of the impeller at least in part based on the determined left ventricular pressure.

[0138] In some applications, the computer processor is configured to reduce the rotational rate of the impeller in response to determining that the left ventricular pressure of the subject has decreased.

[0139] In some applications, 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 move axially back and forth relative to the frame in response to a periodic change in the pressure difference between the first location and the second location. In some applications, the impeller is configured to pump blood from the left ventricle of the subject to the aorta of the subject, and the impeller is configured to move axially back and forth relative to the frame in response to a periodic change in the pressure difference between the left ventricle and the aorta. In some applications, the impeller is configured to pump blood from the right ventricle of the subject to the pulmonary artery of the subject, and the impeller is configured to move axially back and forth relative to the frame in response to a periodic change in the pressure difference between the right ventricle and the pulmonary artery. In some applications, the impeller is configured to pump blood from the right atrium of the subject to the right ventricle of the subject, and the impeller is configured to move axially back and forth relative to the frame in response to a periodic change in the pressure difference between the right atrium and the right ventricle. In some applications, the impeller is configured to pump blood from the vena cava of the subject to the right ventricle of the subject, and the impeller is configured to move axially back and forth relative to the frame in response to a periodic change in the pressure difference between the vena cava and the right ventricle. In some applications, the impeller is configured to pump blood from the right atrium of the subject to the pulmonary artery of the subject, and the impeller is configured to move axially back and forth relative to the frame in response to a periodic change in the pressure difference between the right atrium and the pulmonary artery. In some applications, the impeller is configured to pump blood from the vena cava of the subject to the pulmonary artery of the subject, and the impeller is configured to move axially back and forth relative to the frame in response to a periodic change in the pressure difference between the vena cava and the pulmonary artery.

[0140] In some applications, the device further comprises:

[0141] a motor configured to drive the impeller to pump blood through the subject's body by rotating the impeller in a given rotational direction;

[0142] an axial shaft to which the impeller is coupled; and

[0143] A drive cable configured to extend from outside the subject's body to the axial shaft, the drive cable configured to transmit rotational motion from the motor to the impeller by rotation, at least a portion of the drive cable including multiple wires arranged in a coiled configuration such that in response to rotation of the drive cable in the given rotational direction, the multiple wires arranged in the coiled configuration at least partially unwind, causing the portion of the drive cable to shorten axially.

[0144] In some applications:

[0145] The impeller includes a proximal bushing and a distal bushing;

[0146] The frame includes a proximal bearing and a distal bearing;

[0147] The device further includes an axial shaft that:

[0148] Passes through the proximal bearing and the distal bearing defined by the frame and the proximal bushing and the distal bushing of the impeller,

[0149] Is coupled to at least one of the proximal bushing and the distal bushing of the impeller such that the at least one bushing is maintained in an axially fixed position relative to the axial shaft,

[0150] Is not maintained in an axially fixed position relative to the proximal bearing and the distal bearing,

[0151] Such that the impeller causes the axial shaft to move axially back and forth relative to the proximal bearing and the distal bearing of the frame.

[0152] In some applications, the axial shaft is configured to clean the interface between the axial shaft and the proximal bearing and the distal bearing of the frame by making the axial back-and-forth movement relative to the proximal bearing and the distal bearing of the frame. In some applications, the axial shaft is configured to reduce heat accumulation at the interface between the axial shaft and the proximal bearing and the distal bearing of the frame by making the axial back-and-forth movement relative to the proximal bearing and the distal bearing of the frame, as compared to the case where the axial shaft does not make the axial back-and-forth movement relative to the proximal bearing and the distal bearing of the frame.

[0153] According to some applications of the present invention, the following inventive concepts are also provided:

[0154] Inventive Concept 1. A device, the device including:

[0155] An impeller, the impeller including:

[0156] At least one helical elongated element;

[0157] A spring, the spring being disposed within the helical elongate element and along the axis about which the helical elongate element is wound;

[0158] A membrane of a material, the membrane of the material being supported between the helical elongate element and the spring; and

[0159] At least one flexible elongate element, the 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 thread.

[0160] Inventive concept 2. The device according to inventive concept 1, wherein the impeller is configured such that in a non-radially constrained configuration of the impeller, the outer diameter of the impeller at the position where the outer diameter is at its maximum value is less than 8 mm.

[0161] Inventive concept 3. The device according to inventive concept 1, wherein the at least one helical elongate element comprises a plurality of helical elongate elements, and wherein the at least one flexible elongate element extends from the spring to each of the helical elongate elements.

[0162] Inventive concept 4. The device according to any one of inventive concepts 1-3, wherein the impeller is configured to pump blood through a subject's body.

[0163] Inventive concept 5. The device according to inventive concept 4, wherein the impeller is configured to be placed within a blood vessel of a subject.

[0164] Inventive concept 6. The device according to inventive concept 4, wherein the impeller is configured to be placed within a heart chamber of a subject.

[0165] Inventive concept 7. The device according to inventive concept 4, wherein the impeller is configured to pump blood from the left ventricle of a subject to the aorta of the subject.

[0166] Inventive concept 8. The device according to inventive concept 4, wherein the impeller is configured to pump blood from the right ventricle of a subject to the pulmonary artery of the subject.

[0167] Inventive concept 9. A method, the method comprising:

[0168] Placing an impeller into a subject's body, the impeller comprising:

[0169] At least one helical elongate element;

[0170] A spring, the spring being disposed within the helical elongate element and along the axis about which the helical elongate element is wound;

[0171] A membrane of a material, the membrane of the material being supported between a helical elongate element and a spring; and

[0172] At least one flexible elongate element extending from the spring to the helical elongate element, selected from the group consisting of: string and wire; and

[0173] By rotating the impeller to pump blood through the body of a subject, during the rotation of the impeller, the flexible elongate element holds the helical elongate element within a given distance from the spring.

[0174] Inventive concept 10. An apparatus, the apparatus comprising:

[0175] A blood pump, the blood pump comprising:

[0176] An impeller configured to be placed within a heart chamber of a subject;

[0177] A frame configured to be disposed around the impeller; and

[0178] A motor configured to drive the impeller by rotating the impeller to pump blood from the heart chamber of the subject to a blood vessel,

[0179] The impeller is configured to perform an axial movement relative to the frame in response to a periodic change in the pressure difference between the heart chamber and the blood vessel.

[0180] Inventive concept 11. A method, the method comprising:

[0181] Placing an impeller of a blood pump within a heart chamber of a subject, with a frame disposed around the impeller; and

[0182] Driving the impeller by rotating the impeller to pump blood from the heart chamber of the subject to a blood vessel,

[0183] The placement of the impeller within the heart chamber allows the impeller to perform an axial movement relative to the frame in response to a periodic change in the pressure difference between the heart chamber and the blood vessel.

[0184] Inventive concept 12. An apparatus, the apparatus comprising:

[0185] A blood pump, the blood pump comprising:

[0186] An impeller configured to be placed within a first blood vessel of a subject;

[0187] A frame configured to be disposed around the impeller; and

[0188] A motor configured to drive the impeller by rotating the impeller to pump blood from the first blood vessel of the subject to a second blood vessel,

[0189] The impeller is configured to axially move relative to the frame in response to periodic variations in the pressure difference between a first blood vessel and a second blood vessel.

[0190] Inventive Concept 13. A method, the method comprising:

[0191] Placing an impeller of a blood pump within a first blood vessel of a subject, the impeller being surrounded by a frame; and

[0192] Driving the impeller by rotating the impeller to pump blood from the first blood vessel of the subject to a second blood vessel,

[0193] Placement of the impeller within the first blood vessel allows the impeller to axially move relative to the frame in response to periodic variations in the pressure difference between the heart chamber and the blood vessel.

[0194] Inventive Concept 14. An apparatus, the apparatus comprising:

[0195] A blood pump, the blood pump comprising:

[0196] An impeller configured to be placed within the body of a subject and configured to rotate to pump blood through the body of the subject;

[0197] A frame configured to be disposed around the impeller; and

[0198] One or more thrust bearings configured to be disposed outside the body of the subject, wherein counteraction of the thrust generated by rotation of the impeller is provided only by the one or more thrust bearings disposed outside the body of the subject.

[0199] Inventive Concept 15. A method, the method comprising:

[0200] Placing an impeller of a blood pump within the body of a subject, the impeller being surrounded by a frame; and

[0201] Driving the impeller by rotating the impeller to pump blood through the body of the subject, wherein counteraction of the thrust generated by rotation of the impeller is provided only by the one or more thrust bearings disposed outside the body of the subject.

[0202] Inventive Concept 16. An apparatus, the apparatus comprising:

[0203] A blood pump tube;

[0204] A blood pump configured to be disposed within the blood pump tube and configured to pump blood through the blood pump tube;

[0205] At least one blood pressure measurement tube that defines an opening at its distal end and is configured to extend to the outer surface of at least the blood 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 external to the blood pump tube; and

[0206] At least one pressure sensor configured to measure the blood flow pressure of the subject external to the blood pump tube by measuring the blood pressure within the blood pressure measurement tube.

[0207] Inventive concept 17. The device according to inventive concept 16, wherein the blood pump includes an impeller configured to pump blood through the blood pump tube by rotation.

[0208] Inventive concept 18. The device according to inventive concept 16, wherein the blood pressure measurement tube is configured to pass along the outer surface of the blood pump tube from the proximal end of the blood pump tube until the opening at the distal end of the blood pressure measurement tube.

[0209] Inventive concept 19. The device according to inventive concept 16, further comprising at least one computer processor configured to receive an indication of the blood pressure measured within the blood pressure measurement tube and configured to control the pumping of blood through the blood pump in response to the blood pressure measured within the blood pump tube.

[0210] Inventive concept 20. The device according to any one of inventive concepts 16-19, wherein the at least one blood pressure measurement tube includes at least one left ventricular blood pressure measurement tube configured to extend to the outer surface of the blood pump tube at a position along the tube configured to be within the left ventricle of the subject near the blood pump, and wherein the pressure sensor is configured to measure the left ventricular pressure of the subject by measuring the blood pressure within the left ventricular blood pressure measurement tube.

[0211] Inventive concept 21. The device according to 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 the outer surface of the blood pump tube at a position along the blood pump tube configured to be within the left ventricle of the subject near the blood pump, and wherein at least one pressure sensor is configured to measure the left ventricular pressure of the subject by measuring the blood pressure within at least one of the left ventricular blood pressure measurement tubes.

[0212] Inventive concept 22. The device according to inventive concept 21,

[0213] wherein at least one pressure sensor is configured to measure the blood pressure within each of the two or more left ventricular blood pressure measurement tubes,

[0214] the device further comprising at least one computer processor configured to:

[0215] Receiving an indication of the blood pressure measured within each of two or more left ventricular blood pressure measurement tubes,

[0216] Determining in response thereto that an opening of one of the two or more left ventricular blood pressure measurement tubes is blocked, and

[0217] Determining in response thereto the left ventricular pressure of the subject based on the blood pressure measured within a different one of the two or more left ventricular blood pressure measurement tubes.

[0218] Inventive concept 23. The apparatus according to inventive concept 20, wherein at least one blood pressure measurement tube further comprises at least one aortic blood pressure measurement tube configured to extend to an outer surface of the blood pump tube at a location along the blood pump tube configured to be within the aorta of the subject, and wherein the pressure sensor is configured to measure the aortic pressure of the subject by measuring the blood pressure within the aortic blood pressure measurement tube.

[0219] Inventive concept 24. The apparatus according to inventive concept 23, wherein at least one aortic blood pressure measurement tube comprises two or more aortic blood pressure measurement tubes configured to extend to an outer surface of the blood pump tube at a location along the blood pump tube configured to be within the aorta of the subject, and wherein at least one pressure sensor is configured to measure the aortic pressure of the subject by measuring the blood pressure within the at least one aortic blood pressure measurement tube.

[0220] Inventive concept 25. The apparatus according to any one of inventive concepts 16-19, wherein at least one blood pressure measurement tube comprises at least one aortic blood pressure measurement tube configured to extend to an outer surface of the blood pump tube at a location along the blood pump tube configured to be within the aorta of the subject, and wherein the pressure sensor is configured to measure the aortic pressure of the subject by measuring the blood pressure within the aortic blood pressure measurement tube.

[0221] Inventive concept 26. The apparatus according to inventive concept 25, wherein at least one aortic blood pressure measurement tube comprises two or more aortic blood pressure measurement tubes configured to extend to an outer surface of the blood pump tube at a location along the blood pump tube configured to be within the aorta of the subject, and wherein at least one pressure sensor is configured to measure the aortic pressure of the subject by measuring the blood pressure within the at least one aortic blood pressure measurement tube.

[0222] Inventive concept 27. The apparatus according to inventive concept 26,

[0223] wherein at least one pressure sensor is configured to measure the blood pressure within each of the two or more aortic blood pressure measurement tubes,

[0224] The device further includes at least one computer processor configured to:

[0225] receive an indication of blood pressure measured within each of two or more aortic blood pressure measurement tubes,

[0226] in response thereto determine that an opening of one of the two or more aortic blood pressure measurement tubes is blocked, and

[0227] in response thereto determine the aortic pressure of the subject based on blood pressure measured within a different one of the two or more aortic blood pressure measurement tubes.

[0228] Inventive concept 28. The device according to any one of inventive concepts 16 - 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 wherein the at least one pressure sensor is configured to be disposed outside the subject's body.

[0229] Inventive concept 29. The device according to inventive concept 28, wherein the blood pump includes an impeller disposed on an axial shaft, the impeller being configured to pump blood from the left ventricle to the aorta by rotation, and wherein the device further includes:

[0230] a motor disposed outside the subject's body and configured to drive the impeller to rotate;

[0231] a drive cable extending from outside the subject's body to the axial shaft and configured to transmit rotational motion from the motor to the impeller by rotation; and

[0232] an outer tube configured to extend from outside the subject's body into the blood pump tube,

[0233] wherein the drive cable and the blood pressure measurement tube are configured to be disposed within the outer tube.

[0234] Inventive concept 30. The device according to inventive concept 29,

[0235] 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 pump tube at a position along the blood pump tube configured to be within the subject's left ventricle and near the blood pump, and wherein the at least one pressure sensor is configured to measure the subject's left ventricular pressure by measuring the blood pressure within the left ventricular blood pressure measurement tube;

[0236] the device further includes an aortic blood pressure measurement tube that defines an opening at its distal end and is 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;

[0237] At least one of the pressure sensors is further configured to measure the aortic pressure of the subject by measuring the blood pressure within the aortic blood pressure measurement tube.

[0238] Inventive concept 31. The device according to inventive concept 29,

[0239] 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 pump tube at a position close to the blood pump along the blood pump tube configured to be within the left ventricle of the subject, and wherein the at least one pressure sensor is configured to measure the left ventricular pressure of the subject by measuring the blood pressure within the left ventricular blood pressure measurement tube;

[0240] The device further includes an aortic blood pressure measurement tube that defines an opening at its distal end and is configured to extend from outside the subject's body to a portion of the outer surface of an outer tube disposed within the blood pump tube such that the opening at the distal end of the blood pressure measurement tube is in direct fluid communication with the aortic blood flow of the subject;

[0241] wherein the at least one pressure sensor is further configured to measure the aortic pressure of the subject by measuring the blood pressure within the aortic blood pressure measurement tube.

[0242] Inventive concept 32. The device according to inventive concept 29, wherein the outer tube defines a groove in a portion of the outer surface of the outer tube configured to be disposed within the blood pump tube, and wherein, during insertion of the ventricular assist device into the subject's body, the portion of the blood pressure measurement tube configured to extend from within the blood pump tube to the outer surface of the blood pump tube is configured to be disposed within the groove such that this portion of the blood pressure measurement tube does not protrude from the outer surface of the outer tube.

[0243] Inventive concept 33. The device according to inventive concept 28, wherein the diameter of the blood pressure measurement tube is less than 0.5 mm at least within the distal portion of the blood pressure measurement tube.

[0244] Inventive concept 34. The device according to inventive concept 33, wherein the diameter of the blood pressure measurement tube is greater than 0.2 mm at least within the distal portion of the blood pressure measurement tube.

[0245] Inventive concept 35. A method, the method comprising:

[0246] Placing into the subject's body:

[0247] A blood pump tube,

[0248] A blood pump disposed within the blood pump tube, and

[0249] At least one blood pressure measurement tube that defines an opening at its distal end and extends to at least the outer surface of the blood 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 external to the blood pump tube;

[0250] Using a blood pump to pump blood through the blood pump tube; and

[0251] Measuring the blood flow pressure of the subject external to the blood pump tube by measuring the blood pressure within the blood pressure measurement tube.

[0252] Inventive Concept 36. An apparatus comprising:

[0253] A blood pump comprising:

[0254] A tube;

[0255] An impeller configured to be disposed within the tube and configured to rotate to pump blood through the tube;

[0256] A frame disposed around the impeller; and

[0257] A stator configured to reduce the rotational flow component of the blood flow generated by the rotation of the impeller, the stator comprising:

[0258] A plurality of struts integral with the frame and curved; and

[0259] A flexible material coupled to the curved struts such that a plurality of curved protrusions are formed.

[0260] Inventive Concept 37. The apparatus according to Inventive Concept 36, wherein the curvature of the curved protrusion is opposite to the direction of rotation of the impeller.

[0261] Inventive Concept 38. The apparatus according to Inventive Concept 36, the curvature of the curved protrusion being such that from the distal end of the curved protrusion to the proximal end of the curved protrusion, the curved protrusion gradually becomes closer to being parallel to the longitudinal axis of the frame.

[0262] Inventive Concept 39. The apparatus according to Inventive Concept 36, wherein the flexible material is shaped to define a lumen therethrough.

[0263] Inventive Concept 40. A method comprising:

[0264] Placing a blood pump into a subject's body, the blood pump comprising:

[0265] A tube,

[0266] An impeller configured to be disposed within the tube,

[0267] A frame disposed around the impeller, and

[0268] A stator, the stator including a plurality of struts that are integral with and curved with respect to a frame, and a flexible material coupled to the curved struts such that a plurality of curved protrusions are formed; and

[0269] Using an impeller to pump blood through a tube, the stator reduces the rotational flow component of the blood flow generated by the rotation of the impeller.

[0270] Inventive Concept 41. An apparatus, the apparatus comprising:

[0271] A ventricular assist device, the device comprising:

[0272] An axial shaft;

[0273] An impeller, the impeller being disposed on the axial shaft and configured to be placed in the left ventricle of a subject;

[0274] A motor, the motor being configured to be disposed outside the body of the subject and configured to drive the impeller to rotate to pump blood from the left ventricle to the aorta of the subject by rotating the impeller;

[0275] A drive cable, the drive cable being configured to extend from outside the body of the subject to the axial shaft, the drive cable being configured to transmit rotational motion from the motor to the impeller by rotation, the drive cable including a first portion configured to be disposed at least partially within the aortic arch of the subject and a second portion configured to be disposed at least partially within the descending aorta of the subject,

[0276] The first portion of the drive cable includes a first number of wires disposed in a coiled configuration, and the second portion of the drive cable includes a second number of wires disposed in a coiled configuration, the first number being lower than the second number.

[0277] Inventive Concept 42. The apparatus according to Inventive Concept 41, wherein the length of the first portion of the drive cable is between 20 cm and 40 cm.

[0278] Inventive Concept 43. The apparatus according to Inventive Concept 41, wherein the length of the second portion of the drive cable is between 60 cm and 100 cm.

[0279] Inventive Concept 44. The apparatus according to Inventive Concept 41, wherein the first portion of the drive cable includes between 4 and 8 wires disposed in a coiled configuration, and the second portion of the drive cable includes between 8 and 12 wires disposed in a coiled configuration.

[0280] Inventive Concept 45. An apparatus, the apparatus comprising:

[0281] A blood pump, the blood pump comprising:

[0282] An axial shaft;

[0283] An impeller, the impeller being disposed on an axial shaft;

[0284] A motor, the motor being configured to be disposed outside the body of a subject and being configured to drive the impeller to pump blood through the body of the subject by rotating the impeller;

[0285] A drive cable, the drive cable being configured to extend from outside the body of the subject to the axial shaft, the drive cable being configured to transmit rotational motion from the motor to the impeller by rotation, the drive cable including a first portion configured to be disposed at least partially within a curved portion of the vasculature of the subject and a second portion configured to be disposed at least partially within a straight portion of the vasculature of the subject,

[0286] The first portion of the drive cable includes a first number of wires disposed in a coiled configuration, and the second portion of the drive cable includes a second number of wires disposed in a coiled configuration, the first number being lower than the second number.

[0287] Inventive concept 46. An apparatus, the apparatus including:

[0288] A blood pump, the blood pump including:

[0289] An axial shaft;

[0290] An impeller, the impeller being disposed on the axial shaft;

[0291] A motor, the motor being configured to be disposed outside the body of a subject and being configured to drive the impeller to pump blood from a distal end of the impeller to a proximal end of the impeller by rotating the impeller in a given rotational direction;

[0292] A drive cable, the drive cable being configured to extend from outside the body of the subject to the axial shaft, the drive cable being configured to transmit rotational motion from the motor to the impeller by rotation,

[0293] At least a portion of the drive cable includes a plurality of wires disposed in a coiled configuration such that in response to the drive cable rotating in a given rotational direction, the plurality of wires disposed in the coiled configuration at least partially unwind, causing the portion of the drive cable to axially shorten.

[0294] Inventive concept 47. The apparatus according to inventive concept 46, wherein the impeller is configured to pump blood from a first position to a second position, and wherein the impeller is configured to perform an axial back-and-forth motion in response to a periodic change in the pressure difference between the first position and the second position.

[0295] Inventive concept 48. A method, the method including:

[0296] Placing a blood pump into the body of a subject, the blood pump including:

[0297] Axial shaft,

[0298] An impeller disposed on the axial shaft, and

[0299] A drive cable extending from outside the subject's body to the axial shaft; and

[0300] Driving the impeller to pump blood from the distal end of the impeller to the proximal end of the impeller by transmitting rotational motion to the impeller via the drive cable, at least a portion of the drive cable including multiple wires arranged in a coiled configuration such that in response to rotation of the drive cable in a given rotational direction, the multiple wires arranged in the coiled configuration at least partially unwind, causing that portion of the drive cable to axially shorten.

[0301] Inventive concept 49. An apparatus comprising:

[0302] A blood pump comprising:

[0303] An axial shaft;

[0304] An impeller disposed on the axial shaft;

[0305] A motor configured to be disposed outside the subject's body and configured to drive the impeller to pump blood in a proximal direction by rotating the impeller in a given rotational direction;

[0306] A drive cable configured to extend from a proximal end of the drive cable disposed outside the subject's body to a distal end of the drive cable, the drive cable being coupled to the axial shaft and configured to transmit rotational motion from the motor to the impeller by rotation;

[0307] An outer tube disposed around the drive cable; and

[0308] A fluid disposed between the outer tube and the drive cable,

[0309] At least a portion of the drive cable includes multiple wires arranged in a coiled configuration such that in response to rotation of the drive cable in a given rotational direction, the multiple wires are configured to pump the fluid toward the proximal end of the drive cable.

[0310] Inventive concept 50. A method comprising:

[0311] Placing a blood pump into a subject's body, the blood pump comprising:

[0312] An axial shaft,

[0313] An impeller disposed on the axial shaft,

[0314] A drive cable extending from outside the subject's body to the axial shaft,

[0315] An outer tube disposed around the drive cable, and

[0316] A fluid disposed between the drive cable and the outer tube; and

[0317] By transmitting rotational motion to the impeller via the drive cable to drive the impeller to pump blood from the distal end of the impeller to the proximal end of the impeller, at least a portion of the drive cable includes a plurality of wires disposed in a coiled configuration such that in response to the drive cable rotating in a given rotational direction, the plurality of wires are configured to pump the fluid towards the proximal end of the drive cable.

[0318] Inventive concept 51. An apparatus comprising:

[0319] A blood pump comprising:

[0320] An impeller;

[0321] A motor configured to drive the impeller to pump blood by rotating the impeller, the impeller being configured to move axially in response to a change in the pressure differential against which the impeller pumps blood;

[0322] A magnet, the impeller being coupled to the magnet such that axial movement of the impeller causes axial movement of the magnet;

[0323] A sensor configured to detect the magnetic flux generated by the magnet and configured to generate a sensor signal in response thereto; and

[0324] A computer processor configured to receive the sensor signal and configured to generate an output in response thereto.

[0325] Inventive concept 52. The apparatus according to inventive concept 51, wherein the computer processor is configured to generate an output indicative of the cardiac cycle of the subject in response to receiving the sensor signal.

[0326] Inventive concept 53. The apparatus according to inventive concept 51, wherein the computer processor is configured to determine the left ventricular pressure of the subject at least in part based on the sensor signal.

[0327] Inventive concept 54. The apparatus according to any one of inventive concepts 51-53, wherein the computer processor is configured to change the rotational speed of the impeller at least in part based on the sensor signal.

[0328] Inventive concept 55. The apparatus according to inventive concept 54, wherein the computer processor is configured to:

[0329] Determine the left ventricular pressure of the subject at least in part based on the sensor signal, and

[0330] At least partially change the rotational speed of the impeller based on the determined left ventricular pressure.

[0331] Inventive concept 56. The device according to inventive concept 55, wherein the computer processor is configured to reduce the rotational speed of the impeller in response to determining that the left ventricular pressure of the subject has decreased.

[0332] Inventive concept 57. A device, the device comprising:

[0333] A blood pump, the blood pump comprising:

[0334] An impeller;

[0335] A motor configured to drive the impeller to pump blood by rotating the impeller, the impeller being configured to axially move in response to a change in the pressure difference against which the impeller pumps blood;

[0336] A sensor configured to detect an indication of the axial movement of the impeller and configured to generate a sensor signal in response thereto; and

[0337] A computer processor configured to receive the sensor signal and configured to generate an output in response thereto.

[0338] Inventive concept 58. A method, the method comprising:

[0339] Placing a blood pump into a subject's body, the blood pump comprising an impeller;

[0340] Driving the impeller to pump blood by rotating the impeller, the impeller being configured to axially move in response to a change in the pressure difference against which the impeller pumps blood;

[0341] Detecting an indication of the axial movement of the impeller and generating a sensor signal in response thereto; and

[0342] Receiving the sensor signal and generating an output in response thereto.

[0343] Inventive concept 59. A device, the device comprising:

[0344] A blood pump, the blood pump comprising:

[0345] An impeller;

[0346] A frame,

[0347] The impeller and the frame are configured to be inserted into the subject's body such that, within the subject's body, the frame is disposed around the impeller; and

[0348] A computer processor configured to drive a motor unit to simultaneously (a) drive an impeller to rotate to pump blood through a subject's body by rotating the impeller, and (b) drive the impeller to axially move in a reciprocating motion within a frame.

[0349] Inventive Concept 60. A method comprising:

[0350] Placing a blood pump including an impeller and a frame into a subject's body such that the frame is disposed around the impeller; and

[0351] Simultaneously:

[0352] Driving the impeller to rotate to pump blood through the subject's body by rotating the impeller; and

[0353] Driving the impeller to axially move in a reciprocating motion within the frame.

[0354] Inventive Concept 61. An apparatus comprising:

[0355] A blood pump including:

[0356] An axial shaft;

[0357] An impeller disposed on the axial shaft and configured to be placed in a subject's left ventricle;

[0358] A motor configured to be disposed outside the subject's body and configured to drive the impeller to rotate;

[0359] A drive cable configured to extend from outside the subject's body to the axial shaft via the subject's aortic arch, the drive cable being configured to transmit rotational motion from the motor to the impeller by rotation;

[0360] A tube, the drive cable being configured to be disposed within the tube during rotation of the drive cable, the tube being configured to remain stationary during rotation of the drive cable; and

[0361] A plurality of ball bearings configured to be disposed between the drive cable and the tube to reduce friction between the drive cable and the tube during relative movement of the drive cable with respect to the tube.

[0362] Inventive Concept 62. The apparatus according to Inventive Concept 61, wherein the ball bearings are configured to be disposed between the drive cable and the tube during rotation of the impeller, at least at portions of the drive cable and the tube configured to be disposed within the subject's aortic arch.

[0363] Inventive Concept 63. An apparatus comprising:

[0364] A blood pump including:

[0365] Axial shaft;

[0366] An impeller disposed on the axial shaft and configured to be placed within a subject's body;

[0367] A motor configured to be disposed outside the subject's body;

[0368] A drive cable configured to extend from outside the subject's body to the axial shaft;

[0369] Exactly two drive magnets disposed within a drive magnet housing coupled to the motor; and

[0370] A driven magnet coupled to the drive cable and disposed between the drive magnets such that there is an axial overlap between the drive magnets and the driven magnet, the driven magnet defining a single north pole and a single south pole separated along the axial length of the driven magnet, the motor being configured to rotate the driven magnet by rotating the drive magnet housing to rotate the drive cable to transmit rotational movement to the impeller.

[0371] Inventive Concept 64. A method comprising:

[0372] Placing a blood pump into a subject's body, the blood pump comprising:

[0373] An axial shaft,

[0374] An impeller disposed on the axial shaft, and

[0375] A drive cable extending from outside the subject's body to the axial shaft; and driving the impeller to rotate by:

[0376] Using a motor to rotate exactly two drive magnets disposed within a drive magnet housing coupled to the motor,

[0377] The drive magnets being configured to thereby drive a driven magnet to rotate, the driven magnet being coupled to the drive cable and disposed between the drive magnets such that there is an axial overlap between the drive magnets and the driven magnet, the driven magnet defining a single north pole and a single south pole separated along the axial length of the driven magnet.

[0378] Inventive Concept 65. An apparatus comprising:

[0379] A blood pump comprising:

[0380] An axial shaft;

[0381] An impeller disposed on the axial shaft and configured to be placed within a subject's body;

[0382] A motor configured to be disposed outside a subject's body;

[0383] A drive cable configured to extend from outside the subject's body to an axial shaft;

[0384] Exactly two driven magnets disposed in a driven magnet housing coupled to the drive cable; and

[0385] A drive magnet coupled to the motor and disposed between the driven magnets such that there is an axial overlap between the driven magnets and the drive magnet, the drive magnet defining a single north pole and a single south pole separated along the axial length of the drive magnet, the motor being configured to rotate the driven magnets by rotating the drive magnet to rotate the drive cable to transmit rotational motion to an impeller.

[0386] Inventive concept 66. A method comprising:

[0387] Placing a blood pump into a subject's body, the blood pump comprising:

[0388] An axial shaft,

[0389] An impeller disposed on the axial shaft, and

[0390] A drive cable extending from outside the subject's body to the axial shaft; and driving the impeller to rotate by:

[0391] Using a motor to rotate a drive magnet coupled to the motor, the drive magnet defining a single north pole and a single south pole separated along the axial length of the drive magnet,

[0392] The drive magnet being configured to thereby drive the driven magnets to rotate, the driven magnets comprising exactly two driven magnets disposed in a driven magnet housing coupled to the drive cable and disposed around the drive magnet.

[0393] Inventive concept 67. An apparatus comprising:

[0394] A blood pump comprising:

[0395] An axial shaft;

[0396] An impeller disposed on the axial shaft and configured to be placed within a subject's body;

[0397] A motor configured to be disposed outside a subject's body and configured to drive the impeller to pump blood by rotating the impeller in a given rotational direction;

[0398] A drive cable configured to extend from outside a subject's body to an axial shaft, the drive cable configured to transfer rotational movement from a motor to an impeller by rotation, and the drive cable including a plurality of wires arranged in a coiled configuration and coupled to the axial shaft,

[0399] The axial shaft defines a groove at the junction between the drive cable and the axial shaft, the groove configured such that stress generated by the wires at the junction is distributed over the radius of the groove.

[0400] Inventive concept 68. An apparatus, the apparatus comprising:

[0401] A blood pump, the blood pump comprising:

[0402] An axial shaft;

[0403] An impeller disposed on the axial shaft and configured to be placed within a subject's body;

[0404] A motor configured to be disposed outside the subject's body and configured to drive the impeller to pump blood by rotating the impeller in a given rotational direction;

[0405] A drive cable configured to extend from outside a subject's body to the axial shaft, the drive cable configured to transfer rotational movement from the motor to the impeller by rotation, and the drive cable including a plurality of wires arranged in a coiled configuration and coupled to the axial shaft,

[0406] The coiled wires are shaped such that as the coiled wires approach the junction between the drive cable and the axial shaft, the pitch of the wires increases, such that stress at the location where the wires of the drive cable are coupled to the axial shaft is reduced relative to the case where the pitch of the wires does not increase.

[0407] Inventive concept 69. An apparatus, the apparatus comprising:

[0408] A blood pump, the blood pump comprising:

[0409] An axial shaft;

[0410] An impeller disposed on the axial shaft and configured to be placed within a subject's body;

[0411] A motor configured to be disposed outside the subject's body and configured to drive the impeller to pump blood by rotating the impeller in a given rotational direction;

[0412] A drive cable configured to extend from outside a subject's body to the axial shaft, the drive cable configured to transfer rotational movement from the motor to the impeller by rotation,

[0413] The drive cable includes a first portion and a second portion. The first portion of the drive cable includes a first number of wires arranged in a coiled configuration, and the second portion of the drive cable includes a second number of wires arranged in a coiled configuration, the first number being less than the second number; and

[0414] An interface member that couples the first and second portions of the drive cable to each other;

[0415] The interface member defines a groove at the junction between at least one of the portions of the drive cable and the interface member, the groove being configured to distribute the stress generated by the wires at the junction over the radius of the groove.

[0416] Inventive concept 70. An apparatus, the apparatus comprising:

[0417] A blood pump, the blood pump comprising:

[0418] An axial shaft;

[0419] An impeller disposed on the axial shaft and configured to be placed within a subject's body;

[0420] A motor configured to be disposed outside the subject's body and configured to drive the impeller to pump blood by rotating the impeller in a given rotational direction;

[0421] A drive cable configured to extend from outside the subject's body to the axial shaft, the drive cable configured to transmit rotational motion from the motor to the impeller by rotation;

[0422] The drive cable includes a first portion and a second portion. The first portion of the drive cable includes a first number of wires arranged in a coiled configuration, and the second portion of the drive cable includes a second number of wires arranged in a coiled configuration, the first number being less than the second number; and

[0423] An interface member that couples the first and second portions of the drive cable to each other;

[0424] The coiled wires of at least one of the portions of the drive cable are shaped such that as the coiled wires approach the interface member, the pitch of the wires increases, such that the stress at the location where the wires are coupled to the interface member is reduced relative to the case where the pitch of the wires did not increase.

[0425] Inventive concept 71. An apparatus, the apparatus comprising:

[0426] A ventricular assist device, the device comprising:

[0427] A tube configured to pass through a subject's aortic valve such that a proximal portion of the tube is disposed within the subject's aorta and a distal portion of the tube is disposed within the subject's left ventricle, the tube defining one or more blood inlet openings within the distal portion of the tube and one or more blood outlet openings within the proximal portion of the tube;

[0428] 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 to pump blood from the tube into the aorta through one or more blood outlet openings; and

[0429] A radially expandable atraumatic distal end portion configured to be disposed distally within the subject's left ventricle relative to one or more blood inlet openings, the distal end portion being configured to be inserted into the left ventricle in a radially constrained configuration and to assume a non-radially constrained configuration within the subject's left ventricle, wherein at least a radially expandable portion of the distal end portion expands radially relative to the radially constrained configuration of the distal end portion.

[0430] The device according to inventive concept 72 of inventive concept 71, wherein the distal end portion comprises a braided shape memory alloy that is at least partially covered with a blood-impermeable material.

[0431] The device according to inventive concept 73 of inventive concept 71, wherein the distal end portion is configured such that in the non-radially constrained configuration of the distal end portion, the radially expandable portion of the distal end portion separates one or more blood inlet openings from the interventricular septum within the left ventricle.

[0432] The device according to inventive concept 74 of inventive concept 71, wherein the distal end portion is configured such that in the non-radially constrained configuration of the distal end portion, the radially expandable portion of the distal end portion separates one or more blood inlet openings from the chordae tendineae within the left ventricle.

[0433] The device according to inventive concept 75 of inventive concept 71, wherein the distal end portion is configured such that in the non-radially constrained configuration of the distal end portion, the radially expandable portion of the distal end portion separates one or more blood inlet openings from the papillary muscles within the left ventricle.

[0434] The device according to inventive concept 76 of inventive concept 71, wherein the distal end portion is configured such that in the non-radially constrained configuration of the distal end portion, the radially expandable portion of the distal end portion separates one or more blood inlet openings from the apex of the left ventricle.

[0435] Inventive concept 77. The device according to inventive concept 71, wherein the distal end portion is configured such that in the non-radially constrained configuration of the distal end portion, the radially expandable portion of the distal end portion separates one or more blood inlet openings from the internal structure of the left ventricle in three dimensions.

[0436] Inventive concept 78. The device according to inventive concept 71, wherein the distal end portion is configured such that in the non-radially constrained configuration of the distal end portion, the radially expandable portion of the distal end portion directs blood flow from the left ventricle into one or more blood inlet openings.

[0437] Inventive concept 79. The device according to any one of inventive concepts 71-78, wherein:

[0438] In the radially constrained configuration of the distal end portion, the distal region of the distal end portion is configured to be at least semi-rigid and is shaped to radially converge towards the distal end of the distal end portion along the longitudinal direction;

[0439] The ventricular assist device is configured to be inserted into the subject's body via a perforation in the subject's body, and

[0440] During the insertion of the ventricular assist device, the distal region of the distal end portion is configured to act as a dilator by enlarging the perforation.

[0441] Inventive concept 80. The device according to any one of inventive concepts 71-78, wherein the distal end portion is configured such that in the non-radially constrained configuration of the distal end portion, the distal end of the distal end portion is encapsulated within the radially expandable portion of the distal end portion.

[0442] Inventive concept 81. The device according to inventive concept 80, wherein the distal end portion is configured to prevent the distal end of the distal end portion from becoming entangled with the chordae tendineae of the left ventricle by the distal end of the distal end portion being encapsulated within the radially expandable portion of the distal end.

[0443] Inventive concept 82. The device according to inventive concept 80, wherein the distal end portion is configured to prevent the distal end of the distal end portion from causing damage to the internal structure of the left ventricle by the distal end of the distal end portion being encapsulated within the radially expandable portion of the distal end portion.

[0444] Inventive concept 83. The device according to inventive concept 80, wherein the distal end of the distal end portion is configured to be encapsulated within the radially expandable portion of the distal end portion by the distal end of the distal end portion being flipped.

[0445] Inventive Concept 84. The device according to Inventive Concept 80, wherein a distal end of the distal end portion is configured to be encapsulated within a radially expandable portion of the distal end portion by retracting the distal end of the distal end portion proximally such that the distal end is disposed within the radially expandable portion of the distal end portion.

[0446] Inventive Concept 85. A device comprising:

[0447] A ventricular assist device configured to be inserted into a subject's body via a perforation, the ventricular assist device comprising:

[0448] A tube configured to pass through the subject's aortic valve such that a proximal portion of the tube is disposed within the subject's aorta and a distal portion of the tube is disposed within the subject's left ventricle, the tube defining one or more blood inlet openings within the distal portion of the tube and one or more blood outlet openings within the proximal portion of the tube;

[0449] A blood pump configured to be disposed within the tube and pump blood from the left ventricle into the tube through the one or more blood inlet openings and pump blood from the tube into the aorta through the one or more blood outlet openings; and

[0450] A distal end portion configured to:

[0451] Have a radially constrained configuration in which a distal region of the distal end portion is at least partially rigid and shaped to radially converge along a longitudinal direction toward a distal end of the distal end portion, the distal region being configured to act as a dilator by enlarging the perforation during insertion of the ventricular assist device into the subject's body, and

[0452] Have a non-radially constrained configuration, the distal end region being configured to assume the non-radially constrained configuration within the subject's left ventricle, in which the radially expandable portion of the distal end portion is configured to be atraumatic and to separate the one or more blood inlet openings from the internal structure of the subject's left ventricle.

[0453] Inventive Concept 86. A method comprising:

[0454] Operating a blood pump comprising:

[0455] An axial shaft,

[0456] An impeller disposed on the axial shaft and disposed within the subject's left ventricle;

[0457] A motor disposed outside the subject's body and configured to drive the impeller to rotate,

[0458] A drive cable that extends from outside the subject's body through the subject's aortic arch to the axial axis and is configured to transmit rotational motion from a motor to an impeller by rotation, and

[0459] A tube within which the drive cable is disposed, the tube being configured to remain stationary during rotation of the drive cable; and

[0460] While operating the blood pump, pumping fluid into the space between the drive cable and the tube such that the space between the drive cable and the tube is filled with the fluid, but not releasing the fluid into the subject's bloodstream.

[0461] Inventive concept 87. A method comprising:

[0462] Operating a blood pump that includes:

[0463] An axial axis,

[0464] An impeller disposed on the axial axis and disposed in the left ventricle of the subject,

[0465] A motor disposed outside the subject's body and configured to drive the impeller to rotate,

[0466] A drive cable that extends from outside the subject's body through the subject's aortic arch to the axial axis and is configured to transmit rotational motion from the motor to the impeller by rotation, and

[0467] A tube within which the drive cable is disposed, the tube being configured to remain stationary during rotation of the drive cable;

[0468] Before operating the blood pump, pumping fluid into the space between the drive cable and the tube such that the space between the drive cable and the tube is filled with the fluid, but not releasing the fluid into the subject's bloodstream; and

[0469] During operation of the blood pump, leaving the fluid within the space between the drive cable and the tube.

[0470] Inventive concept 88. An apparatus comprising:

[0471] A left ventricular assist device configured to assist the operation of the left ventricle of a subject, the left ventricular assist device including:

[0472] A tube configured to pass through the subject's aortic valve such that a proximal portion of the tube is at least partially disposed within the subject's ascending aorta and a distal portion of the tube is at least partially disposed within the subject's left ventricle;

[0473] A frame disposed within the distal portion of the tube, the frame being configured to hold the distal portion of the tube in an open state,

[0474] The frame is not disposed within the proximal portion of the tube, and the proximal portion of the tube is thus configured to collapse inwardly in response to pressure outside the proximal portion of the tube exceeding the pressure within the proximal portion of the tube;

[0475] A pump disposed within the frame and configured to pump blood from the left ventricle of a subject to the aorta of the subject through the tube such that the proximal portion of the tube remains in an open state when the blood pressure generated by the blood pump within the proximal portion of the tube exceeds the aortic pressure of the subject outside the proximal portion of the tube; and

[0476] A plurality of elongated commissural elements disposed within the proximal portion of the tube such that when the proximal portion of the tube collapses inwardly, corresponding portions of the circumference of the tube form cusps that contact each other.

[0477] Inventive concept 89. The apparatus according to inventive concept 88, further comprising a computer processor configured to control the pumping of blood by the blood pump through the tube such that the blood pressure generated by the blood pump within the tube exceeds the systolic aortic pressure of the subject and is less than the diastolic aortic pressure of the subject.

[0478] Inventive concept 90. The apparatus according to inventive concept 88, further comprising a pressure sensor configured to measure the aortic blood pressure of the subject, and wherein the computer processor is configured to receive an indication of the measured aortic blood pressure and is configured to control the pumping of blood by the blood pump through the tube in response to the measured aortic blood pressure.

[0479] Inventive concept 91. The apparatus according to inventive concept 88, further comprising a pressure sensor configured to measure the left ventricular blood pressure of the subject, and wherein the computer processor is configured to receive an indication of the measured left ventricular blood pressure and is configured to control the pumping of blood by the blood pump through the tube in response to the measured left ventricular blood pressure.

[0480] Inventive concept 92. An apparatus for use with a delivery device, the apparatus comprising:

[0481] An impeller;

[0482] A frame disposed around the impeller,

[0483] The impeller and the frame are configured to be inserted into a blood vessel of a subject via the delivery device while being in their radially constrained configuration and are configured to assume a non-radially constrained configuration upon release from the delivery device; and

[0484] A coupling element, the coupling element including a first portion disposed on the impeller and a second portion disposed on the frame and configured to engage with the first portion, the coupling element being configured to promote radial contraction of the impeller by holding an end of the impeller such that the impeller can axially elongate without radially contracting the frame.

[0485] Inventive concept 93. An apparatus, the apparatus comprising:

[0486] A blood pump tube:

[0487] An impeller configured to be disposed within the blood pump tube and configured to pump blood from a first location to a second location by pumping blood through the blood pump tube;

[0488] A motor disposed outside the body of the subject and configured to drive the impeller to rotate;

[0489] A drive cable extending from outside the body of the subject to an axial shaft and configured to transmit rotational motion from the motor to the impeller by rotation;

[0490] An outer tube disposed around the drive cable, the outer tube configured to extend from outside the body of the subject into the blood pump tube, the outer tube defining a first opening and a second opening on a portion of the outer tube disposed within the blood pump tube; and

[0491] A flow obstruction disposed on the first opening such that the first opening is configured to serve as a stagnation pressure tap and the second opening is configured to serve as a static pressure tap;

[0492] At least one pressure sensor configured to measure the pressure within the stagnation pressure tap and the pressure within the static pressure tap; and

[0493] A computer processor configured to determine the flow rate through the blood pump tube at least in part based on the pressure measured within the stagnation pressure tap and the pressure measured within the static pressure tap.

[0494] Inventive concept 94. A method, the method comprising:

[0495] Inserting a blood pump into a subject's body, the blood pump including:

[0496] An impeller including a proximal bushing and a distal bushing,

[0497] A frame disposed around the impeller, the frame including a proximal bearing and a distal bearing, and

[0498] An axial shaft that passes through the proximal bearing and the distal bearing of the frame and the proximal bushing and the distal bushing of the impeller. The proximal bushing of the impeller is coupled to the axial shaft such that the proximal bushing remains in an axially fixed position relative to the axial shaft, and the distal bushing of the impeller is not coupled to the axial shaft such that the distal bushing does not remain in an axially fixed position relative to the axial shaft.

[0499] While the impeller is inserted into the body of a subject, the impeller is held in a radially constrained configuration by a delivery catheter.

[0500] When the impeller is disposed within the body of the subject, releasing the impeller from the catheter allows the distal bushing to slide on the axial shaft, thereby causing the impeller to change from its radially constrained configuration to a non-radially constrained configuration; and

[0501] Using the impeller to pump blood through the body of the subject while the impeller is disposed in its non-radially constrained configuration.

[0502] Inventive concept 95. A method comprising:

[0503] Placing an impeller of a ventricular assist device within the left ventricle of a subject, the impeller being surrounded by a frame; and

[0504] Driving the impeller by rotating the impeller to pump blood from the left ventricle of the subject to the aorta.

[0505] Placement of the impeller within the left ventricle allows the impeller to axially move relative to the frame in response to periodic variations in the pressure differential between the left ventricle and the aorta.

[0506] Inventive concept 96. A method comprising:

[0507] Placing a blood pump within the body of a subject, the blood pump comprising:

[0508] An impeller having a frame disposed around the impeller, the impeller including a proximal bushing and a distal bushing, and the frame including a proximal bearing and a distal bearing, and

[0509] An axial shaft that passes through the proximal bearing and the distal bearing of the frame and the proximal bushing and the distal bushing of the impeller, the axial shaft being coupled to at least one of the proximal bushing and the distal bushing of the impeller such that the at least one bushing remains in an axially fixed position relative to the axial shaft and does not remain in an axially fixed position relative to the proximal bearing and the distal bearing; and

[0510] Using the impeller to pump blood through the body of the subject.

[0511] Inventive concept 97. A method comprising:

[0512] Place the impeller of the blood pump within the body of a subject, with a frame disposed around the impeller; and

[0513] Drive the impeller to pump blood through the body of the subject without using any thrust bearings disposed within the body of the subject to provide a counteraction to the thrust generated by the rotation of the impeller.

[0514] The present invention will be more fully understood from the following detailed description of embodiments of the invention taken in conjunction with the accompanying drawings, in which: Brief Description of the Drawings

[0515] Figure 1A and Figure 1B are schematic views of a ventricular assist device according to some applications of the present invention, with the distal end of the ventricular assist device disposed within the left ventricle of a subject;

[0516] Figure 2A 、 Figure 2B and Figure 2C are schematic views of the pump portion of a ventricular assist device according to some applications of the present invention;

[0517] Figure 3A 、 Figure 3B and Figure 3C are schematic views of the impeller of a ventricular assist device according to some applications of the present invention;

[0518] Figure 4 is a schematic view of an impeller disposed within the frame of a ventricular assist device according to some applications of the present invention;

[0519] Figure 5A and Figure 5B are schematic views of the impeller and frame of a ventricular assist device in its non-radially constrained state and radially constrained state, respectively, according to some applications of the present invention;

[0520] Figure 5C is a schematic view of a typical bearing assembly used in an axial impeller-based blood pump of the prior art;

[0521] Figure 6A and Figure 6B are schematic views of a ventricular assist device at various stages of the movement cycle of the impeller of the ventricular assist device relative to the frame of the ventricular assist device according to some applications of the present invention;

[0522] Figure 6C is a schematic view of the axial shaft receiving tube and distal end portion of a ventricular assist device according to some applications of the present invention;

[0523] Figure 7Schematic diagram of a motor unit of a ventricular assist device according to some applications of the present invention;

[0524] Figure 8A and Figure 8B Schematic diagram of a motor unit of a ventricular assist device according to some applications of the present invention;

[0525] Figure 9 Graph showing the change in the length of the drive cable of a ventricular assist device when the pressure gradient resisted by the impeller of the blood pump changes, as measured in experiments performed by the inventors of the present application;

[0526] Figure 10A 、 Figure 10B and Figure 10C Schematic diagram of a drive cable of a ventricular assist device according to some applications of the present invention;

[0527] Figure 11A and Figure 11B Schematic diagram of an interface component according to some applications of the present invention, which forms a junction between corresponding portions of the drive cable of the ventricular assist device;

[0528] Figure 11C 、 Figure 11D and Figure 11E Schematic diagram of the junction between the drive cable and the axial shaft of a ventricular assist device according to some applications of the present invention;

[0529] Figure 12 Schematic diagram of a drive cable of a ventricular assist device according to some applications of the present invention, the drive cable including a friction reduction element provided around at least a portion of the drive cable;

[0530] Figure 13 Schematic diagram of a program for purifying the drive cable and / or radial bearing of a ventricular assist device according to some applications of the present invention;

[0531] Figure 14A and Figure 14B Schematic diagram of a frame of a ventricular assist device according to some applications of the present invention, to which a stator is coupled to the proximal portion;

[0532] Figure 15A Schematic diagram of the flat profile of a frame of a ventricular assist device according to some applications of the present invention;

[0533] Figure 15B Schematic diagram showing an enlarged view of the proximal end of a frame of a ventricular assist device according to some applications of the present invention;

[0534] Figure 15CSchematic diagram of a frame of a ventricular assist device for some applications according to the present invention, where the material defining the curved protrusion is coupled to the frame;

[0535] Figure 16A , Figure 16B , Figure 16C and Figure 16D Schematic diagram of a ventricular assist device including one or more blood pressure measurement tubes for some applications according to the present invention;

[0536] Figure 17A , Figure 17B and Figure 17C Schematic diagram of a ventricular assist device including a pitot tube configured to measure blood flow through a tube of the device for some applications according to the present invention;

[0537] Figure 18 Schematic diagram of a ventricular assist device for some applications according to the present invention, where the distal end portion of the device is a radially expandable atraumatic distal end portion;

[0538] Figure 19A and Figure 19B Schematic diagram of a ventricular assist device for some applications according to the present invention, where the distal end portion of the device is a radially expandable atraumatic distal end portion;

[0539] Figure 20A and Figure 20B Schematic diagram of a ventricular assist device for some applications according to the present invention, where the distal end portion of the device is a radially expandable atraumatic distal end portion;

[0540] Figure 21A , Figure 21B , Figure 21C and Figure 21D Schematic diagram of the distal end portion of a ventricular assist device for some applications according to the present invention;

[0541] Figure 22A and Figure 22B Schematic diagram of the distal end portion of a ventricular assist device in an axially reinforced configuration and a non-axially reinforced configuration, respectively, for some applications according to the present invention;

[0542] Figure 23A and Figure 23B Schematic diagram of the distal end portion of a ventricular assist device in a radially constrained configuration and a non-radially constrained configuration, respectively, for some applications according to the present invention;

[0543] Figure 24A and Figure 24B Schematic diagram of the distal end portion of a ventricular assist device in a radially constrained configuration and a non-radially constrained configuration, respectively, for some applications according to the present invention;

[0544] Figure 25A is a schematic view of a first portion and a second portion of a coupling element according to some applications of the present invention, the coupling element being configured to facilitate radial contraction of an impeller (e.g., during crimping);

[0545] Figure 25B and Figure 25C is a schematic view of various stages of crimping of an impeller according to some applications of the present invention;

[0546] Figure 26 is a schematic view of a blocker according to some applications of the present invention, the blocker being 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;

[0547] Figure 27A and Figure 27B is a schematic view of a ventricular assist device according to some applications of the present invention, the device including a valve to prevent backflow of blood, e.g., in the event of a failure of the impeller of the ventricular assist device; and

[0548] Figure 28A 、 Figure 28B and Figure 28C is a schematic view of a ventricular assist device according to some applications of the present invention, the device including a safety bladder to prevent backflow of blood, e.g., in the event of a failure of the impeller of the ventricular assist device. DETAILED DESCRIPTION

[0549] Now referring to Figure 1A and Figure 1B , Figure 1A and Figure 1B are schematic views of a ventricular assist device 20 according to some applications of the present invention, the distal end of the ventricular assist device 20 being disposed in the left ventricle 22 of a subject; the ventricular assist device includes a tube 24 that passes through the aortic valve 26 of the subject such that the proximal end 28 of the tube is disposed in the aorta 30 of the subject and the distal end 32 of the tube is disposed within the left ventricle 22. The tube 24 (sometimes referred to herein as the "blood pump tube") is generally an elongate tube, and the axial length of the tube is generally significantly greater than its diameter. The scope of the present invention includes the use of the devices and methods described herein in anatomical locations other than the left ventricle and aorta. Thus, the ventricular assist device and / or portions thereof are sometimes referred to herein (in the specification and claims) as a blood pump.

[0550] As Figure 1B shown in Figure 1BIllustrates the steps of deploying a ventricular assist device in the left ventricle. Generally, the distal end of the ventricular assist device is guided into the left ventricle on a guide wire 10. During insertion of the distal end of the device into the left ventricle, a delivery catheter 143 is disposed on the distal end of the device. Once the distal end of the device is disposed in the left ventricle, the delivery catheter is generally retracted into the aorta and the guide wire is withdrawn from the subject's body. Retraction of the delivery catheter generally causes the self-expandable component of the distal end of the device to assume a non-radially constrained configuration, as described in further detail below. Generally, the ventricular assist device is inserted into the subject's body to provide acute treatment to the subject. For some applications, in order to withdraw the left ventricular device from the subject's body at the end of the treatment, the delivery catheter is advanced over the distal end of the device, which causes the self-expandable component of the distal end of the device to assume a radially constrained configuration. Alternatively or additionally, the distal end of the device is retracted into the delivery catheter, which causes the self-expandable component of the distal end of the device to assume a radially constrained configuration.

[0551] Also refer to Figure 2A 、 Figure 2B and Figure 2C , Figure 2A 、 Figure 2B and Figure 2C are schematic views of the blood pump portion 27 of a ventricular assist device 20 according to some applications of the present invention; generally, an impeller 50 is disposed within the distal portion 102 of a tube 24 and is configured to pump blood from the left ventricle into the aorta by rotation. The tube generally defines one or more blood inlet openings 108 at the distal end of the tube, and during operation of the impeller, blood flows into the tube from the left ventricle via the inlet openings. For some applications, the proximal portion of the tube defines one or more blood outlet openings 109, and during operation of the impeller, blood flows from the tube into the ascending aorta via the outlet openings.

[0552] For some applications, a console 21 (which generally includes a computer processor 25 ( Figure 1A shown in Figure 7 ) drives the rotation of the impeller. For example, the computer processor can control a motor 74 ( Figure 7As shown (in [figure reference]), the drive impeller rotates. For some applications, the computer processor is configured to detect physiological parameters of the subject (such as left ventricular pressure, cardiac afterload, etc.) and is configured to control the rotation of the impeller in response thereto, as described in further detail below. Generally, the operations performed by the computer processor described herein transform the physical state of the memory into a different magnetic polarity, charge, etc., depending on the technology of the memory used, which is a real physical article in communication with the computer processor. The computer processor 25 is typically a hardware device programmed with computer program instructions to produce a special-purpose computer. For example, when programmed to perform the techniques described herein, the computer processor 25 typically acts as a special-purpose ventricular assist computer processor.

[0553] For some applications, the purification system 29 drives a fluid (e.g., a glucose solution) through portions of the ventricular assist device 20, e.g., for cooling portions of the device and / or for cleaning debris from portions of the device. The purification system 29 is described in further detail below.

[0554] Generally, along the distal portion 102 of the tube 24, the 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 shaped such that the frame (and thus the tube) assumes a generally circular, oval, or polygonal cross-sectional shape without any force being applied to the tube. By assuming its generally circular, oval, or polygonal cross-sectional shape, the frame is configured to hold the distal portion of the tube in an open state. Generally, during operation of the ventricular assist device, the distal portion of the tube is configured to be placed within the body of the subject such that the distal portion of the tube is at least partially disposed within the left ventricle.

[0555] 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 keep the aortic valve open by presenting its generally circular, elliptical, or polygonal cross-sectional shape. For some applications, the tube 24 is sized to prevent the shape memory alloy of the frame 34 from fully assuming the dimensions to which the shape memory alloy is shaped. In this way, the frame is "pre-tensioned" such that even if the aortic valve exerts a radially compressive force on the tube and the frame, the frame does not become radially compressed because the frame has been held in a partially radially constrained state by the tube. For some applications, the frame includes a plurality of rigid struts 111 that are disposed parallel to each other and parallel to the 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 generally straight longitudinal axis, even when subjected to anatomical forces within the left ventricle and / or aortic valve. Generally, the rigid struts are configured such that the length of the rigid struts does not change even if the frame 34 changes from a radially constrained configuration (in which the frame is typically disposed during introduction of the frame into the subject's body) to a non-radially constrained configuration (in which the frame is typically disposed during operation of the ventricular assist device).

[0556] For some applications, along the proximal portion 106 of the tube 24, no frame is disposed within the tube, and thus the tube is not supported in an open state by the frame 34. The tube 24 is typically made of a collapsible material that is impermeable to blood. For example, the tube 24 can include polyurethane, polyester, and / or silicone. Generally, the proximal portion of the tube is configured to be placed such that it is at least partially disposed within the subject's ascending aorta. For some applications, the proximal portion of the tube passes through the subject's aortic valve and enters the subject's ascending aorta from the subject's left ventricle, as Figure 1B shown. As described above, the tube typically defines one or more blood inlet openings 108 at the distal end of the tube, through which blood flows from the left ventricle into the tube during operation of the impeller. For some applications, the proximal portion of the tube defines one or more blood outlet openings 109, through which blood flows from the tube into the ascending aorta during operation of the impeller. Generally, 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 blood flow pressure through the tube typically holds the proximal portion of the tube in an open state. For some applications, in the event of a failure of the impeller, for example, the proximal portion of the tube is configured to collapse inwardly in response to the pressure external to the proximal portion of the tube exceeding the pressure within the proximal portion of the tube. In this way, the proximal portion of the tube acts as a safety valve to prevent blood from flowing retrograde from the aorta into the left ventricle.

[0557] For some applications, the computer processor 25 of the console 21 (shown in Figure 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 within the tube 24 exceeds the systolic blood pressure of the subject during systole, but is lower than the diastolic blood pressure of the subject during diastole. During systole, the proximal portion 106 of the tube 24 remains open because the blood pressure within the tube exceeds the aortic pressure applied to the tube from outside the tube. During diastole, the proximal portion of the tube 24 closes because the aortic pressure applied to the tube from outside the tube exceeds the blood pressure within the tube. In this way, 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 aortic pressure, left ventricular pressure, and / or the flow rate through the tube 24, e.g., using the techniques described below with reference to Figure 9 , Figure 16A - Figure 16D and / or Figure 17A - Figure 17C . For some such applications, based on the measured aortic pressure, left ventricular pressure, and / or flow rate, the computer processor controls the rotation of the impeller in the manner described above. Alternatively, the computer processor controls the rotation of the impeller in a manner different from the above based on the measured aortic pressure, left ventricular pressure, and / or flow rate. For example, the computer processor may be configured to change the rotation rate of the impeller based on the measured aortic pressure, left ventricular pressure, and / or flow rate, but in such a way that the impeller pumps blood from the left ventricle to the aorta in a non-pulsatile, continuous manner.

[0558] Typically, pumping blood through the impeller increases the aortic pressure and decreases the left ventricular pressure. Once the flow rate through tube 24 reaches a critical value (above which the aortic pressure is higher than the left ventricular pressure, even during ventricular systole (hereinafter referred to as "systole")), the aortic valve remains closed around the outside of tube 24 throughout the cardiac cycle, and the flow from the ventricle to the aorta occurs only via the tube. Typically, above this point where the aortic pressure dissociates from the ventricular pressure, the left ventricle no longer performs net external work (defined as the change in volume multiplied by the change in pressure) because it does not move any volume. In this mode, the oxygen consumption of the left ventricle depends on the circulatory pressure generated against the closed aortic valve, the wall tension caused by the size of the left ventricle, the wall thickness, and the baseline metabolic requirements (including calcium cycling). Below this critical point of impeller activity, the aortic valve typically opens at least partially during systole, and left ventricular outflow will occur simultaneously between the outside of the tube and the aortic valve (by means of left ventricular contraction) and through the tube (by means of impeller rotation and pumping). For a given number of impeller revolutions per minute, the larger the cross-sectional area of the cannula, the greater the flow rate through the tube will generally be. At the same time, the larger the cross-sectional area of the tube, the more space the tube occupies within the left ventricular outflow tract, the smaller the remaining outflow area, and thus the higher the outflow resistance that the left ventricle must overcome when pumping around the outside of the tube.

[0559] Accordingly, typically, there is a trade-off between the efficiency of the impeller-assisted left ventricle (which advantageously increases with the cannula diameter) and the remaining outflow resistance around the outside of tube 24 (which disadvantageously increases with the cannula diameter). The higher the flow rate through the tube provided by the impeller (for a given cannula diameter), the smaller the effect of the reduced cross-sectional outflow area on the effective outflow resistance may be, because the remaining cross-sectional area may be suitable for the remaining small stroke volume that the ventricle must eject, i.e., the reduced remaining outflow tract area may not impose an undue resistance to outflow. However, conversely, once a fixed cannula diameter is selected, the effective resistance to outflow increases as the flow rate through the tube decreases, because a larger proportion of the left ventricular stroke volume now needs to pass through the remaining outflow tract area around the tube. Accordingly, for some applications, the left ventricular outflow resistance is configured to automatically adjust to compensate for changes in the blood flow through the tube generated by the impeller. For example, the tube can be made of a compliant material whose compliance is such that a decrease in the flow rate through the tube and a subsequent drop in the dilation pressure result in a decrease in the cannula diameter, thereby increasing the outflow area available to the left ventricle. Typically, the material properties of the compliant material are defined such that (a) maximum tube dilation is reached exactly at or near the moment when the pressure within the lumen of the tube generated by the pumping flow exceeds the aortic pressure (irrespective of the moment in the cardiac cycle), and thus remains higher than the left ventricular pressure throughout the cardiac cycle, and (b) complete collapse of the tube is reached when the flow rate through the tube generated by the impeller becomes zero.

[0560] Now referring to Figure 2B , for some applications, a plurality of elongated commissural elements 107 extend along at least some of the proximal portion 106 of the tube 24. As described 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 commissural 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 natural valve leaflets, wherein corresponding portions of the circumference of the tube form apices that contact each other when the tube is closed. For some applications, the ventricular assist device includes three elongated commissural elements, and the proximal portion of the tube 24 is configured to close in a manner similar to the closing of a tri-leaflet valve. ( Figure 2B Such an embodiment is depicted, but one of the commissural elements is hidden from view.) For some applications (not shown), the ventricular assist device includes two elongated commissural elements, and the proximal portion of the tube 24 is configured to close in a manner similar to the closing of a bi-leaflet valve. For some applications, the proximal portion of the tube 24 is positioned such that it passes through the subject's aortic valve, and the commissural elements are rotationally aligned with the commissures of the native valve. In this manner, the artificial apices of the proximal portion of the tube are aligned with the native aortic valve leaflets.

[0561] Referring to Figure 2A - Figure 2C , for some applications, the frame 34 is shaped such that the frame defines a proximal conical portion 36, a central cylindrical portion 38, and a distal conical portion 40. Generally, the proximal conical portion is such that the narrow end of the cone is proximal relative to the wide end of the cone. Additionally, generally, the distal conical portion is such that the narrow end of the cone is distal relative 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 Figure 2A and Figure 2B . Alternatively, the tube 24 extends to the end of the distal conical portion 40, and the tube defines one or more lateral blood inlet openings, as shown in Figure 2C . For such applications, the tube generally defines two to four lateral blood inlet openings.

[0562] Generally, the tube 24 includes a conical proximal portion 42 and a cylindrical central portion 44. Generally, the proximal conical portion is such that the narrow end of the cone is proximal relative to the wide end of the cone. As described 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 generally defines a distal conical portion 46, wherein the narrow end of the cone is distal relative to the wide end of the cone, as shown in Figure 2CAs shown. For some applications (not shown), the diameter of tube 24 varies along the length of the central portion of the tube such that the central portion of the tube has a frustoconical shape. For example, the central portion of the tube can widen from its proximal end to its distal end or can narrow from its proximal end to its distal end. For some applications, at its proximal end, the central portion of the 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.

[0563] Now referring to Figure 3A - Figure 3C , Figure 3A - Figure 3C is a schematic view of an impeller 50 for some applications in accordance with the present invention. Generally, the impeller includes at least one outer helical elongate element 52 that is wound around a central axial spring 54 such that the helical member defined by the helical elongate element is coaxial with the central axial spring. Generally, the impeller includes two or more helical elongate elements (e.g., three helical elongate elements, as Figure 3A - Figure 3C shown). For some applications, the helical elongate element and the central axial spring are made of a shape memory material, e.g., a shape memory alloy such as nitinol. Generally, each of the helical elongate element and the central axial spring supports a membrane 56 of a material (e.g., a polymer such as polyurethane and / or silicone) therebetween. For purposes of illustration, an impeller without the material is shown in Figure 3A . Figure 3B and Figure 3C show views of the impeller, respectively, in which the material is supported between the helical elongate element and the spring.

[0564] Each helical elongate element, together with the membrane extending from the helical elongate element to the spring, defines a respective impeller blade, where the helical elongate element defines the outer edge of the blade and the axial spring defines the axis of the impeller. Generally, the membrane of the material extends along the spring and covers the spring. For some applications, a suture 53 (e.g., a polyester suture, shown in Figure 3B and Figure 3C ) is wound around the helical elongate element, e.g., as described in Schwammenthal's US 2016 / 0022890, which is incorporated herein by reference. Generally, the suture is configured to facilitate the bonding between the membrane of the material (generally a polymer such as polyurethane or silicone) and the helical elongate element (generally a shape memory alloy such as nitinol). For some applications, a suture (e.g., a polyester suture, not shown) is wound around the spring 54. Generally, the suture is configured to facilitate the bonding between the membrane of the material (generally a polymer such as polyurethane or silicone) and the spring (generally a shape memory alloy such as nitinol).

[0565] Typically, the proximal ends of the spring 54 and the helical elongate member 52 extend from the proximal bushing (i.e., sleeve bearing) 64 of the impeller such that the proximal ends of the spring 54 and the helical elongate member 52 are disposed at a similar radial distance from the longitudinal axis of the impeller relative to each other. Similarly, typically, the distal ends of the spring 54 and the helical elongate member 52 extend from the distal bushing 58 of the impeller such that the distal ends of the spring 54 and the helical elongate member 52 are disposed at a similar radial distance from the longitudinal axis of the impeller relative to each other. Typically, the spring 54 and the proximal bushing 64 and the distal bushing 58 of the impeller define an inner cavity 62 therethrough.

[0566] Now refer to Figure 4 , Figure 4 FIG. is a schematic view of an impeller 50 disposed within a frame 34 of a 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 at a position where the span of the impeller is at its maximum value. For some applications, it is desirable that the gap between the outer edge of the blades of the impeller and the inner surface of the frame 34 be relatively small so that the impeller effectively pumps blood from the left ventricle of a subject into the aorta of the subject. However, it is also desirable to maintain the gap between the outer edge of the blades of the impeller and the inner surface of the frame 34, for example, to reduce the risk of hemolysis.

[0567] For some applications, the gap G between the outer edge of the impeller and the inner surface of the frame 34 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) at a position where the span of the impeller is at its maximum value, e.g., 0.05 mm - 1 mm, or 0.1 mm - 0.4 mm. For some applications, the outer diameter of the impeller at a position where the outer diameter of the impeller is at its maximum value is greater than 6 mm (e.g., greater than 6.5 mm), and / or less than 8 mm (e.g., less than 7 mm), e.g., 6 mm - 8 mm, or 6.5 mm - 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), e.g., 6.5 mm - 8.5 mm, or 7 mm - 7.5 mm.

[0568] Typically, the axis of the axial shaft 92 passes through the inner cavity 62 of the impeller 50. Typically, the proximal bushing 64 of the impeller is coupled to the shaft such that the axial position of the proximal bushing relative to the shaft is fixed, and the distal bushing 58 of the impeller is slidable relative to the shaft. The axial shaft itself is radially stabilized via a proximal radial bearing 116 and a distal radial bearing 118 defined by the frame 34. In turn, by passing through the inner cavity 62 defined by the impeller, the axial shaft radially stabilizes the impeller relative to the inner surface of the frame 34 such that, during rotation of the impeller, an even relatively small clearance (e.g., the clearance as described above) between the outer edges of the blades of the impeller and the inner surface of the frame 34 is maintained.

[0569] Referring again to Figure 3A - Figure 3C , for some applications, the impeller includes a plurality of elongate elements 67 that radially extend from a central axial spring 54 to an outer helical elongate element 52. The elongate elements are typically flexible but generally inextensible along the axis defined by the elongate elements. Additionally, typically, each elongate element is configured not to exert a force on the helical elongate element unless a force acts on the impeller that causes the helical elongate element to move radially outward such that the spacing between the helical elongate element and the central axial spring would be greater than the length of the elongate element in the absence of the elongate element. For example, the elongate elements can include strings (such as polyester and / or another polymer or natural material containing fibers) and / or wires (such as nitinol wires and / or wires made of different alloys or metals).

[0570] For some applications, the elongate elements 67 maintain the helical elongate element (which defines the outer edge of the impeller blade) within a given distance relative to the central axial spring. In this manner, the elongate elements are configured to prevent the outer edge of the impeller from being radially pushed outward due to forces applied to the impeller during rotation of the impeller. The elongate elements are thus configured to maintain the clearance between the outer edges of the blades of the impeller and the inner surface of the frame 34 during rotation of the impeller. Typically, more than one (e.g., more than two) and / or less than eight (e.g., less than four) elongate elements 67 are used in the impeller, and each elongate element is typically doubled (i.e., radially extends from the central axial spring 54 to the outer helical elongate element 52 and then returns from the helical elongate element to the central axial spring). For some applications, the plurality of elongate elements are formed from a single piece of string or a single wire, with each of the plurality of elongate elements extending from the spring to a corresponding helical elongate element and back to the spring, as described in further detail below.

[0571] 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 are typically performed such that the helical elongate element is defined by the shape memory material, e.g., using techniques generally similar to those described in Schwammenthal's US 2016 / 0022890. Generally, the spring 54 is inserted into the cut and shaped tube such that the spring extends along the length of the tube from at least the proximal bushing to the distal bushing. For some applications, the spring is inserted into the cut and shaped tube while the spring is in an axially compressed state, and the spring is configured to remain in place relative to the tube by applying a radial force on the proximal bushing and the distal bushing. Optionally or additionally, portions of the spring are welded to the proximal bushing and the distal bushing. For some applications, the spring is cut from a tube of shape memory material such as nitinol. For some such applications, the spring is configured such that when the spring is set in a non-radially constrained configuration (in which the spring is typically set during the operation of the impeller), there is substantially no gap between the windings of the spring and the windings adjacent thereto.

[0572] For some applications, at this stage, the elongate element 67, as described above, is placed such that it extends between the spring and one or more helical elongate elements (e.g., in the following manner). A mandrel (e.g., a polyetheretherketone (PEEK) and / or polytetrafluoroethylene (PTFE) mandrel) is inserted through the lumen defined by the spring and the bushings. A string or wire is then passed through such that it (a) goes from the mandrel to the first helical elongate element, (b) returns from the first helical elongate element to the mandrel, (c) passes around the mandrel and goes to the second helical elongate element, (d) returns from the second helical elongate element to the mandrel, and so on. Once the string or wire has passed from the mandrel through and back to each helical elongate element, the ends of the string or wire are joined to each other, e.g., by tying them to each other. For some applications, a suture 53 (e.g., a polyester suture) is wound around the helical elongate element in order to facilitate the bonding between a film of material (usually a polymer such as polyurethane or silicone) and the helical elongate element (usually a shape memory alloy such as nitinol) in a subsequent stage of impeller manufacture. For some applications, a suture (e.g., a polyester suture, not shown) is wound around the spring 54. Generally, the suture is configured to facilitate the bonding between a film of material (usually a polymer such as polyurethane or silicone) and the spring (usually a shape memory alloy such as nitinol) in a subsequent stage of impeller manufacture.

[0573] Generally, at this stage, as Figure 3AAs shown, structure 59 has been assembled. The structure includes a cut and shaped tube that defines a proximal bushing, a distal bushing, a helical elongate element, a spring, and optionally an elongate element and a suture. The structure is immersed in a material that defines membrane 56. For some applications, the assembled structure is immersed in the material with its central axis disposed through the lumen defined by the spring and bushing, although it is noted that the mandrel is not shown in Figure 3A As shown. Typically, the material from which the membrane is made is silicone (and / or a similar polymer), and the assembled structure is immersed in the material while the material is in an uncured liquid state. Subsequently, the material is cured so that it solidifies, for example, by allowing it to dry. Once the material has dried, the mandrel is typically removed from the lumen defined by the bushing and spring.

[0574] The result of the process described above is typically that there is a continuous membrane of material that extends between each helical elongate element to the spring and also along the length of the spring to define a tube in which the spring is embedded. The portion of the membrane that extends from each helical elongate element to the spring defines an impeller blade. For applications in which the impeller includes elongate element 67, the elongate element is typically embedded in these portions of the membrane.

[0575] Typically, impeller 50 is inserted transcatheterally into the left ventricle while impeller 50 is in a radially constrained configuration. In the radially constrained configuration, both helical elongate element 52 and central axial spring 54 become axially elongated and are radially constrained. Typically, the membrane 56 of material (such as silicone) changes shape to conform to the shape changes of the helical elongate element and the axial support spring, both of which support the membrane of material. Typically, using a spring to support the inner edge of the membrane allows the membrane to change shape without becoming ruptured or collapsed because the spring provides a large surface area that binds the inner edge of the membrane. For some applications, using a spring to support the inner edge of the membrane reduces the diameter to which the impeller can be radially constrained relative to if, for example, a rigid shaft were used to support the inner edge of the membrane because the diameter of the spring itself can be reduced by axially elongating the spring.

[0576] As described above, for some applications, proximal bushing 64 of impeller 50 is coupled to axial shaft 92 such that the axial position of the proximal bushing relative to the shaft is fixed and distal bushing 58 of the impeller is slidable relative to the shaft. For some applications, when the impeller is radially constrained for the purpose of inserting the impeller into the ventricle or for the purpose of withdrawing the impeller from the subject's body, the impeller axially elongates by sliding axially distally along the distal bushing.

[0577] As Figure 3A - Figure 3CAs shown, after being released into the body of a subject, the impeller assumes its non-radially constrained configuration (in which the impeller is typically disposed during operation of the impeller). Generally, when the impeller 50 is in the non-radially constrained configuration (e.g., within a ventricle of a subject), the pitch of each helical elongate element 52 is greater than 1 mm (e.g., greater than 6 mm), and / or less than 20 mm (e.g., less than 10 mm). Generally, all other factors being equal, the greater the pitch of the helical elongate element (and thus the impeller blades), the greater the blood flow generated by the impeller. Thus, as described, when the impeller 50 is in the non-radially constrained configuration, the pitch of the helical elongate element 52 is typically greater than 1 mm (e.g., greater than 6 mm). On the other hand, it is generally desirable for the impeller to block the backflow of blood into the left ventricle of the subject. All other factors being equal, it is generally the case that the smaller the pitch of the helical elongate element (and thus the impeller blades), the greater the blockage provided by the impeller. Thus, as described, when the impeller 50 is in the non-radially constrained configuration, the pitch of the helical elongate element 52 is typically less than 20 mm (e.g., less than 10 mm).

[0578] For some applications, at least when the impeller is in the non-radially constrained configuration, the pitch of the helical elongate element (and thus the impeller blades) varies along the length of the helical elongate element. Generally, for such applications, the pitch increases from the distal end of the impeller (i.e., the end that is inserted further into the body of the subject and is placed upstream relative to the direction of antegrade blood flow) to the proximal end of the impeller (i.e., the end that is placed downstream relative to the direction of antegrade blood flow), such that the pitch increases in the direction of blood flow. Generally, the blood flow velocity increases along the impeller, in the direction of blood flow. Thus, the pitch increases in the direction of blood flow in order to further accelerate the blood.

[0579] Note that, for purposes of illustration, in some of the figures, the impeller 50 is shown as not including all of the features of the impeller as shown and described with reference to Figure 3A - Figure 3C For example, some of the figures show an impeller that does not include the suture 53 and / or the elongate 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 Figure 3A - Figure 3C in combination with any of the devices and methods described herein.

[0580] Now refer to Figure 5A and Figure 5B , Figure 5A and Figure 5BSchematic views of the impeller 50 and the frame 34 of the ventricular assist device 20 in its non-radially constrained state and radially constrained state, respectively, for some applications in accordance with the present invention. During insertion of the impeller and the frame into a subject's body via a catheter, the impeller and the frame are typically arranged in the radially constrained state, and during operation of the impeller in the subject's left ventricle, the impeller and the frame are arranged in the non-radially constrained state. As described above, the tube 24 typically extends from at least the distal portion of the frame and extends proximally therefrom. However, for illustrative purposes, the frame and the impeller are shown in Figure 5A - Figure 5B without the tube 24. As Figure 5B indicated, the frame and the impeller are typically held in the radially constrained configuration by the delivery catheter 143.

[0581] Reference is also made to Figure 5C , Figure 5C which shows a typical bearing assembly used in prior art axial impeller blood pumps. The illustration Figure 5C is for the purpose of serving as a reference point for some applications of the present invention described herein. As Figure 5C shown, the bearing assembly typically includes a radial bearing (indicated by the ellipse 200) and a thrust bearing (indicated by the circle 202). The radial bearing is configured to reduce the radial movement 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 in a direction opposite to the first direction. The purpose of the thrust bearing is to counteract this movement of the impeller and maintain the axial position of the impeller. In the Figure 5C example shown, in response to the impeller pumping blood in the direction of arrow 204, the impeller is pushed in the direction of arrow 206, and the thrust bearing counteracts this movement. Typically, due to the frictional forces applied to the bearings, the bearings experience a significant amount of heating and wear. The thrust bearing typically experiences a significant amount of heating and wear because of the fact that the frictional forces applied to the thrust bearing are typically distributed over relatively opposing surfaces which have a smaller contact area between these surfaces compared to the case of the radial bearing.

[0582] As described above, the axis of the axial shaft 92 generally passes through the inner cavity 62 of the impeller 50. Generally, the proximal bushing 64 of the impeller is coupled to the shaft via a coupling element 65 such that the proximal bushing is fixed in its axial position relative to the shaft, and the distal bushing 58 of the impeller is slidable relative to the shaft. The axial shaft itself is radially stabilized via a proximal radial bearing 116 and a distal radial bearing 118 defined by the frame 34. In turn, by passing through the inner cavity 62 defined by the impeller, the axial shaft radially stabilizes the impeller relative to the inner surface of the frame 34 such that, during rotation of the impeller, an even relatively small clearance (e.g., the clearance described above) between the outer edges of the blades of the impeller and the inner surface of the frame 34 is maintained, as described above. For some applications, the axial shaft 92 is made of stainless steel, and the proximal bearing 116 and / or the distal bearing 118 are made of hardened steel. Generally, when the impeller and the frame are collapsed (i.e., radially constrained) for the purpose of inserting the impeller and the frame into a subject's body, the distal bushing 58 of the impeller is configured to slide along the axial shaft in the distal direction such that the impeller becomes axially elongated, as described above. More generally, by sliding the distal bushing along the axial shaft, the impeller changes from its radially constrained configuration to its non-radially constrained configuration, and vice versa.

[0583] Generally, the impeller itself is not directly disposed within any radial or thrust bearings. Instead, the bearings 116 and 118 act as radial bearings with respect to the axial shaft. For some applications, there is no thrust bearing that contacts any surface and that may generate thrust during rotation of the impeller because the impeller is configured to axially move within the frame 34 while the impeller rotates, as described in further detail below. Generally, the pump section 27 (and more generally the ventricular assist device 20) does not include any thrust bearings that are configured to be disposed within a subject's body and that are configured to oppose the thrust generated by rotation of the impeller. For some applications, one or more thrust bearings are disposed outside of the subject's body (e.g., within the motor unit 23 shown in Figure 1A , Figure 7 and Figure 8A - Figure 8B ), and the force opposing the thrust generated by rotation of the impeller is provided only by one or more thrust bearings disposed outside of the subject's body. For some applications, mechanical and / or magnetic elements are configured to hold the impeller within a given axial position range. For example, a magnet (e.g., magnet 82, described below with reference to Figure 7 ) disposed at the proximal end of the drive cable (e.g., outside of the subject's body) can be configured to transmit axial movement to the impeller and to hold the impeller within a given axial position range.

[0584] For some alternative applications of the present invention, the ventricular assist device includes an impeller that is not configured to move in an axially reciprocating manner. 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 that is proximal to the impeller such that the thrust bearing does not contact the subject's blood. For example, the thrust bearing may be disposed within an outer tube in which the drive shaft of the impeller is disposed. Alternatively or additionally, the thrust bearing may be disposed external to the subject's body. For some such applications, since the thrust bearing is disposed external to the subject's body, the size of the thrust bearing is not limited by the need to be deployed within a small anatomical location. Thus, in such cases, the contact area between two opposing surfaces of the thrust bearing is typically greater than 20 square millimeters. For some applications (not shown), the thrust bearing is disposed distally of the impeller and contacts the subject's blood such that the thrust bearing is cooled by the subject's blood.

[0585] Now refer to Figure 6A and Figure 6B , Figure 6A and Figure 6B are schematic views of a ventricular assist device 20 at various stages of a movement cycle of an impeller 50 of the ventricular assist device relative to a frame 34 of the ventricular assist device, in accordance with some applications of the present invention. For some applications, while the impeller pumps blood through a tube 24 by rotation, an axial shaft 92 (to which the impeller is fixed) is driven to axially reciprocate the impeller within the frame 34 in an axially reciprocating manner by the axial shaft, as described in further detail below with reference to Figure 7 . Alternatively or additionally, the impeller and the axial shaft are configured to axially reciprocate within the frame 34 in response to forces acting on the impeller, and do not require active driving of the axial shaft to move in an axially reciprocating manner, as described in further detail below, for example, with reference to Figure 9 .

[0586] For some applications, by moving in a reciprocating manner, the portions of the axial shaft that contact the proximal bearing 116 and the distal bearing 118 are constantly changing. For some such applications, all other factors being equal, in this way, compared to if the axial shaft did not move relative to the bearings, the frictional force applied by the bearings to the axial shaft is distributed over a larger area of the axial shaft, thereby reducing wear on the axial shaft. Alternatively or additionally, by moving in a reciprocating manner relative to the bearings, the axial shaft clears any residue, such as blood residue, at the interface between the axial shaft and the bearings.

[0587] For some applications, when the frame 34 and the impeller 50 are in their non-radially constrained configuration (e.g., when the frame and impeller are deployed within 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 mm - 4 mm in length. Additionally, typically, the impeller and the axial shaft are configured to axially move within the frame in a back-and-forth motion along at least the length of each of the proximal and distal bearings, or at least twice the length of each of the bearings. Thus, during the back-and-forth axial movement of the axial shaft, the axial shaft is wiped clean on either side of each of the bearings.

[0588] Referring again to Figure 6A and Figure 6B and also referring to Figure 6C , Figure 6C is a schematic view of the axial shaft receiving tube 126 and the distal end portion 120 of the ventricular assist device 20 for some applications in accordance with the present invention. For some applications, the distal end portion of the ventricular assist device is configured to be flexible such that the distal end portion is configured not to damage the tissue of the subject, even when the distal end portion contacts the tissue (e.g., the tissue of the left ventricle). For example, the distal end portion may be made of silicone. For some applications, the distal end portion defines a lumen 122 therethrough. For some such applications, during insertion of the ventricular assist device into the left ventricle, for example, in accordance with known techniques, a guide wire 10 ( Figure 1B ) is first inserted into the left ventricle. The distal end portion of the ventricular assist device is then guided into the left ventricle by advancing the distal end portion over the guide wire, wherein the guide wire is disposed within the lumen 122. For some applications, a hemostatic valve 152 is provided at the distal end of the lumen 122 of the distal end portion 120 such that the distal end portion becomes sealed after the guide wire is retracted from the lumen 122. Typically, during insertion of the ventricular assist device into the ventricle of the subject, a delivery catheter 143 is placed over the impeller 50 and the frame 34 and holds the impeller and the frame in their radially constrained configuration. For some applications, the distal end portion 120 extends distally from the delivery catheter during insertion of the delivery catheter into the ventricle of the subject. For some applications, at the proximal end of the distal end portion, the distal end portion has a flared portion 124 that acts as a stop and prevents the delivery catheter from advancing beyond the flared portion.

[0589] For some applications, the axial shaft receiving tube 126 extends proximally from the distal end portion 120. As described above, during operation of the impeller 50, the axial shaft typically moves axially back and forth. The shaft receiving tube 126 defines a lumen 127 that is 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 stop 128 at its distal end, which is configured to prevent the axial shaft from advancing beyond the stop. For some applications, the stop includes a rigid member that is inserted (e.g., embedded) into the distal end of the shaft receiving tube. Alternatively, the stop includes a shoulder between the lumen 127 of the axial shaft receiving tube and the lumen 122 of the end portion 120. Typically, such a shoulder exists because the lumen 122 of the end portion 120 is narrower than the lumen 127. (This is because the lumen 127 is typically configured to accommodate the axial shaft, while the lumen 122 is configured to accommodate the guide wire 10, and the axial shaft is typically wider than the guide wire 10 because the axial shaft itself is configured to accommodate the guide wire 10 within its internal lumen 132 ( Figure 10B and Figure 10C as shown in)). Typically, during normal operation of the impeller, even when the drive cable 130 (shown in Figure 7 ) is fully extended, the axial shaft does not extend beyond the stop 128. However, the stop 128 is configured to prevent the axial shaft from extending into the end portion during advancement of the delivery catheter over the impeller 50 and the frame 34 during retraction of the ventricular assist device 20 from the ventricle of the subject. In some cases, there is a risk of breakage of the drive cable during advancement of the delivery catheter over the frame and the impeller. In the absence of the stop 128, the axial shaft could extend into the end portion in such a case. The stop 128 prevents this from occurring, even in the event of breakage of the drive cable.

[0590] Typically, during operation of the ventricular assist device, and throughout the back-and-forth axial movement cycle of the impeller, the impeller is positioned relatively close to the distal end portion. For example, throughout the back-and-forth axial movement cycle of the impeller, the distance from the impeller to the distal end portion can be within 50% of the most distal side of the tube 24, such as within 30% (or 20%) of the most distal side.

[0591] For some applications (not shown), a portion of the frame 34 extends into the proximal portion of the distal end portion 120. This portion of the frame is configured to cause the proximal portion of the end to radially expand when the portion of the frame is shaped into a radially expanding configuration and deployed within the left ventricle of the subject. For some applications, the entire end portion is made of a material with uniform stiffness, but a portion of the frame 34 that extends into the proximal portion of the end portion imparts stiffness to the proximal portion of the end portion such that the proximal portion of the end portion has a greater stiffness than the distal portion of the end portion.

[0592] For some applications, the distal portion has a configuration different from that shown in Figure 6C and as further described in detail below. For example, reference is made to Figure 18 - Figure 24B as described. For some applications, the distal end portion will combine certain features described with reference to Figure 6C with features described below (e.g., reference is made to Figure 13 and reference is made to Figure 18 - Figure 24B ). For example, the internal structure of the distal portion and the proximal extension of the axial shaft receiving tube 126 from the distal portion may be as described with reference to Figure 6A - Figure 6C and / or Figure 13 , and the external shape of the distal portion may be as described in any one of Figure 18 - Figure 24B .

[0593] Now referring to Figure 7 , Figure 7 is a schematic diagram of an exploded view of the motor unit 23 of the ventricular assist device 20 for some applications of the present invention. For some applications, the computer processor 25 of the console 21 ( Figure 1A ) that controls the rotation of the impeller 50 is also configured to control the back-and-forth movement of the axial shaft. Generally, both types of movement are generated using the motor unit 23. The scope of the present invention includes controlling the back-and-forth movement 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 back-and-forth movement of the axial shaft is synchronized with the subject's cardiac cycle.

[0594] Generally, the motor unit 23 includes a motor 74 that is configured to transmit rotational movement to the impeller 50 via a drive cable 130. As further described in detail below, generally, the motor is magnetically coupled to the drive cable. For some applications, the axial motion driver 76 is configured to drive the motor to move in an axially back-and-forth manner, as indicated by the bi-directional arrow 79. Generally, by means of the magnetic coupling of the motor to the drive cable, the motor transmits the back-and-forth movement to the drive cable, and the drive cable in turn transmits this movement to the impeller. As described below, for some applications, the drive cable, the impeller, and / or the axial shaft perform an axially back-and-forth movement in a passive manner, e.g., due to periodic changes in the pressure gradient against which the impeller pumps blood. Generally, for such applications, the motor unit 23 does not include the axial motion driver 76.

[0595] For some applications, the magnetic coupling of the motor to the drive cable is as shown in Figure 7 and as shown in Figure 7As shown, a set of drive magnets 77 is coupled to a motor via a drive magnet housing 78. For some applications, the drive magnet housing includes a ring 81 (e.g., a steel ring), and the drive magnets are adhered to the inner surface of the ring. For some applications, as shown, a spacer 85 is adhered to the inner surface of the ring 81 between two drive magnets. A driven magnet 82 is disposed between the drive magnets such that there is an axial overlap between the drive magnets and the driven magnet, and the driven magnet 82 is coupled to the proximal end of a drive cable 130. For example, the driven magnet can be cylindrical and define a hole therethrough, and the proximal end of the drive cable can be adhered to the inner surface of the driven magnet that defines the hole. For some applications, the driven magnet is cylindrical, and the magnet includes a north pole and a south pole, as shown, the north pole and the south pole being separated from each other along a line 83 that bisects the cylinder along the length of the cylinder. For some applications, the driven magnet is housed within a cylindrical housing 87.

[0596] When the field density is greatest, the magnetic coupling is strongest. Thus, it is desirable to use relatively strong magnets for the drive and driven magnets, have a small air gap between the drive and driven magnets, and attempt to minimize field line leakage. Typically, the drive and driven magnets are relatively strong neodymium magnets. Additionally, typically, the gap between each of the drive and driven magnets is less than 2 mm, e.g., about 1 mm. To reduce field line leakage, typically fewer than 4 magnets (e.g., exactly two magnets as shown) are used as drive magnets, for the following reasons.

[0597] Generally, it is desirable to minimize the diameter of the driven magnet, e.g., for stabilizing the driven magnet. As described above, the driven magnet is cylindrical, and the magnet includes a north pole and a south pole, which are separated from each other along the length of the cylinder along the dividing line 83. In the region of the circumference of the driven magnet closest to the dividing line between the north and south poles of the magnet, the magnetic field lines pass directly from the north pole of the magnet to the south pole, rather than passing through the air gap to the first external magnet, through the external magnet, around the ring 81, and across the second drive magnet back to the south pole of the driven magnet. As an approximation, any field line that can be drawn between the north and south poles and is at least less than the sum of the air gaps between the driven magnet and the drive 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. Assume that this adds up to all the field lines extending around 2 mm on either side of the dividing line on the circumference of the driven magnet between the north and south poles of the driven magnet (i.e., a total of 4 mm in the total circumference of the driven magnet), which will not contribute to the magnetic coupling between the drive magnet and the driven magnet. If instead of just two magnetic poles, the driven magnet has four magnetic poles and correspondingly four drive magnets, then there will be four 2-mm-long wasted circumferential portions on the entire circumference, which will result in a total of 8 mm in the 12-mm circumference of the internal magnet having wasted field lines. Some of this loss will be compensated for by adding two additional drive magnets, which increases the magnetic field strength. However, the additional external magnets will be relatively close to each other, which will result in magnetic field leakage between the drive magnets. Given the above, generally, the motor unit includes fewer than 4 magnets (e.g., as shown, exactly two magnets) as drive magnets, and the driven magnet is divided into fewer than 4 magnetic poles (e.g., as shown, exactly two magnetic poles).

[0598] Note that in the application shown in Figure 7 the drive magnets are disposed outside the driven magnet. However, the scope of the present application includes reversing the configuration of the drive magnet and the driven magnet, with necessary modifications. For example, the proximal end of the drive cable can be coupled to two or more driven magnets that are disposed around the drive magnet such that there is an axial overlap between the driven magnet and the drive magnet. The above discussion regarding the number of magnets that should be used as external magnets and the number of magnetic poles into which the internal magnet should be divided equally applies to such a configuration. That is, for such a configuration, generally, the motor unit includes fewer than 4 magnets (e.g., as shown, exactly two magnets) as driven magnets, and the drive magnet is divided into fewer than four magnetic poles (e.g., as shown, exactly two magnetic poles).

[0599] As described above, generally the purification system 29 ( Figure 1Ashown) for use with a ventricular assist device 20. Generally, the motor unit 23 includes an inlet 86 and an outlet 88 for use with a purification system. For some applications, the purification fluid is pumped continuously or periodically into the ventricular assist device via the inlet 86 and pumped out of the ventricular assist device via the outlet 88. For some applications, the purification fluid is pumped into the ventricular assist device, and the inlet port and the outlet port are placed in fluid communication with each other such that a given volume of the purification fluid circulates within the device for a period of time. Further aspects of the purification system are described below.

[0600] Now refer to Figure 8A and Figure 8B , Figure 8A and Figure 8B are schematic views of a motor unit 23 according to some applications of the present invention. Generally, as Figure 8A and Figure 8B shown, the motor unit 23 is similar to the motor unit shown in Figure 7 , and unless otherwise described, as Figure 8A and 8B shown, the motor unit 23 includes components similar to those of the motor unit shown in Figure 7 For some applications, the motor unit includes a radiator 90 configured to dissipate heat generated by the motor. Optionally or additionally, the motor unit includes vents 93 configured to facilitate the dissipation of heat generated by the motor. For some applications, the motor unit includes dampers 94 and 96 configured to suppress vibrations of the motor unit caused by rotational movement and / or axial back-and-forth movement of components of the ventricular assist device.

[0601] For some applications, the impeller 50 and the axial shaft 92 are configured to move axially back and forth within the frame 34 in response to forces acting on the impeller and do not require the axial shaft to be actively driven to move in an axially back-and-forth manner. Generally, during the cardiac cycle of a subject, the pressure difference between the left ventricle and the aorta varies from approximately zero during ventricular contraction (hereinafter "systole") to a relatively large pressure difference (e.g., 60 mmHg - 100 mmHg) during ventricular relaxation (hereinafter "diastole"). For some applications, since the pressure difference against which the impeller pumps increases during diastole, the impeller is pushed distally relative to the frame 34 during diastole as compared to its position relative to the frame 34 during systole. In turn, since the impeller is connected to the axial shaft, the axial shaft moves forward. During systole, the impeller (and in turn the axial shaft) moves back to its systolic position. In this way, the axial back-and-forth movement of the impeller and the axial shaft is generated passively, i.e., without the need to actively drive the axial shaft and the impeller in order to make them perform this movement.

[0602] Now refer toFigure 9 , Figure 9 is a graph indicating the change in length of the drive cable of a ventricular assist device as the pressure gradient against which the impeller of the ventricular assist device resists changes, as measured in an experiment performed by the inventors of the present application. The impeller and drive cable as described herein are used to pump a glycerol-based solution through a chamber, where the chamber is configured to replicate the left ventricle and aorta, and the solution has properties similar to those of blood (such as density and viscosity). As the volume of fluid disposed within the chamber (into which the impeller is pumping) increases, the pressure gradient against which the impeller pumps changes. At the same time, the movement of the drive cable is imaged, and the change in the length of the drive cable is determined via machine vision analysis of the image. Figure 9 The graph shown in Figure 9 indicates the change in length of the drive cable measured according to the pressure gradient. The y-axis of the graph shown in Figure 9 is such that an elongation of 0 mm represents the length of the drive cable when the impeller is stationary. Note that the graph begins at a pressure gradient value of 65 mmHg, and at this pressure the elongation is negative (at approximately -0.25 mm), i.e., the drive cable is shortened relative to the length of the drive cable before the impeller begins to rotate. This is because the drive cable is configured such that when the impeller first begins to pump, due to the uncoiling of the coils within the drive cable, the drive cable is shortened (relative to the length of the drive cable before the impeller is activated), as described in further detail below. As seen in the portion of the curve shown in

[0603] After the initial shortening of the drive cable due to the above effect, then as the pressure gradient increases, the drive cable becomes incrementally elongated. Figure 9 As indicated by the results shown in

[0604] and as described above, typically, in response to a change in the pressure against which the impeller pumps blood (e.g., the pressure difference between the left ventricle and the aorta), the impeller moves back and forth relative to the frame 34. In turn, the movement of the impeller causes the drive cable 130 to become more or less elongated. Figure 1A ) the computer processor 25 of the console 21 is configured to measure an indication of the pressure applied to the impeller (which indicates the pressure difference between the left ventricle and the aorta) by measuring the tension in the drive cable 130 and / or an indication of the axial movement of the drive cable. For some applications, based on the measured indication, the computer processor detects events in the cardiac cycle of the subject, determines the left ventricular pressure of the subject, and / or determines the cardiac afterload of the subject. For some applications, the computer processor controls the rotation of the impeller and / or the axial back-and-forth movement of the axial shaft in response thereto.

[0605] For some applications, generally similar techniques are applied to a right ventricular assist device that is configured to pump blood from the right ventricle to the pulmonary artery, and a computer processor is configured to determine the pressure difference between the right ventricle and the pulmonary artery with necessary modifications in a generally similar manner. For some applications, generally similar techniques are applied to a cardiac assist device that is configured to pump blood from a first location to a second location (such as 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), and a computer processor is configured to determine the pressure difference between the first location and the second location with necessary modifications in a generally similar manner.

[0606] Referring again to Figure 7 , for some applications, the ventricular assist device 20 includes a sensor 84. For example, the sensor can include a Hall sensor disposed within the motor unit 23, as shown in Figure 7 . For some applications, the Hall sensor measures a change in the magnetic field generated by one of the magnets in order to measure the axial movement of the drive cable 130 and thereby determine the pressure against which the impeller pumps. For example, the internal driven magnet 82 can be axially longer than the external drive magnet 77. Since the internal magnet is longer than the external magnet, the magnetic field lines emanating from the internal magnet do not reach the external magnet, and the magnetic flux generated by these magnetic field lines (as measured by the Hall sensor) varies as the drive cable axially moves and thereby the internal magnet axially moves. During operation, the motor 74 rotates, thereby generating an AC signal in the Hall sensor that typically has a frequency between 200 Hz and 800 Hz. Generally, when the 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 that typically has a frequency of 0.5 Hz - 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 should be noted that generally, the axial movement of the magnet is substantially less than the axial movement of the impeller because the entire movement range of the impeller is not transmitted along the length of the drive cable. However, typically, the axial back-and-forth movement of the impeller produces a measurable back-and-forth movement of the magnet.

[0607] For some applications, the measured values of the Hall sensor are initially calibrated such that the change in magnetic flux per unit change in pressure against which the impeller pumps (i.e., per unit change in the pressure difference between the left ventricle and the aorta) is known. It is known that in most subjects, during systole, the left ventricular pressure is equal to the aortic pressure. Thus, for some applications, the aortic pressure of the subject is measured, and then the left ventricular pressure of the subject at a given time is calculated by a computer processor based on: (a) the measured aortic pressure, and (b) the difference between the magnetic flux measured by the 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 pressure in the aorta).

[0608] Now refer to Figure 10A 、 Figure 10B and Figure 10C ,which Figure 10A 、 Figure 10B and Figure 10C are schematic views of the drive cable 130 of the ventricular assist device 20 for some applications in accordance with the present invention. Generally, as described above, the rotational movement of the impeller (which is transmitted via the axial shaft) and the axial back-and-forth movement of the axial shaft as described above are transmitted to the axial shaft via the drive cable. Generally, the drive cable extends from a 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 that are arranged in a tightly coiled configuration to impart sufficient strength and flexibility to the drive cable such that a portion of the cable can be held within the aortic arch (corresponding to the portion of the arrow 145 in Figure 10A ) while the cable rotates and moves in an axial back-and-forth manner. 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 back-and-forth movement. The first outer tube is configured to effectively act as a bearing along the length of the drive cable. Generally, the first outer tube is made of a polymer (such as polyetheretherketone) that is configured to be highly resistant to fatigue even under the frictional forces generated by the relative movement between the drive cable and the first outer tube. However, since such polymers are typically relatively rigid, only a thin layer of the polymer is typically used in the first outer tube. For some applications, the first outer tube is disposed within a second outer tube 142 that is made of a material (such as nylon and / or polyether block amide) that is more flexible than the material of the first outer tube, and the thickness of the second outer tube is greater than the thickness of the first outer tube.

[0609] Typically, during insertion of the impeller and cage into the left ventricle, the impeller 50 and the frame 34 are held in a radially constrained configuration by the delivery catheter 143. As described above, to enable the impeller and frame to assume a non-radially constrained configuration, the delivery catheter is retracted. For some applications, as Figure 10A shown in, during operation of the left ventricular device, the delivery catheter remains in the subject's aorta, and the outer tube 142 is disposed within the delivery catheter. To retract the left ventricular device from the subject's body, the delivery catheter is advanced over the impeller and frame such that the impeller and frame assume their radially constrained configuration. The catheter is then withdrawn from the subject's body.

[0610] Reference Figure 10C , typically, the axial shaft and the cable define a continuous lumen 132 therethrough. For some applications, the left ventricular device is guided into the aorta and into the left ventricle by placing the axial shaft and the cable on the guidewire 10 (described above) such that the guidewire is disposed within the lumen 132. For some applications, by using the lumen of the axial shaft and the cable in this manner, no additional guidewire guide is required for use during insertion of the left ventricular assist device 20. For some applications, the axial shaft and the cable each 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), such as an outer diameter of 0.6 mm - 1.2 mm or 0.8 mm - 1 mm. For some applications, the diameter of the lumen 132 defined by the shaft and the 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), such as 0.3 mm - 0.7 mm, or 0.4 mm - 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), such as a total length of 1 m - 1.4 m, or 1.1 m - 1.3 m. As described above, for some applications, the guidewire additionally passes through the lumen 122 of the distal end portion 120. Typically, the diameter of the lumen 122 is substantially similar to the diameter of the lumen 132.

[0611] Reference Figure 10B, for some applications, the drive cable 130 consists of multiple coiled wires 134. Generally, since the impeller must pump against a pressure gradient during diastole, the impeller is pushed distally relative to the frame 34 as compared to its position relative to the frame during systole, as described above. When the rotation of the impeller begins, if the direction of rotation of the impeller is such that the rotation of the drive cable in that direction causes the coiled wires of the drive cable to at least partially tighten, this will also cause the impeller to advance relative to the frame due to the tightening of the coiled wires (i.e., becoming wound such that the radius of the coil decreases) and thus axial elongation. For some applications, at least a portion of the drive cable is configured such that (a) in response to the impeller pumping blood from the left ventricle to the aorta by rotating in a predetermined direction of rotation, (b) the rotation of the drive cable in that direction causes the coiled wires of the drive cable to at least partially unwind along a portion of the drive cable, such that that portion of the drive cable axially shortens. By constructing the drive cable in the above manner, in addition to accommodating the distal movement of the impeller within the frame due to pressure changes caused by the subject's cardiac cycle (as described above), the length of the frame 34 does not need to accommodate the distal movement of the impeller caused by axial elongation of the drive cable. For some applications, the degree to which the drive cable can unwind and thus axially shorten is limited by an outer tube in which the drive cable is disposed, thereby preventing the drive cable from radially expanding. Thus, for some applications, the drive cable axially shortens a relatively small amount. For some applications, since the outer tube limits the degree to which the drive cable can unwind and thus limits the degree of axial shortening, the drive cable does not shorten. However, even in such applications, since the windings of the coil are constructed as described above, the drive cable is generally configured not to elongate.

[0612] Optionally or additionally, the impeller is inserted into the frame 34 such that the drive cable is already in a preloaded state (i.e., such that the impeller applies a tension on the drive cable that causes the drive cable to be axially elongated relative to its rest state). Due to the preloading of the drive cable, when the rotation of the impeller begins, this does not cause the drive cable to axially elongate because the drive cable is already in an axially elongated state relative to its rest state. For some such applications, the impeller is still configured to undergo axial back-and-forth movement due to pressure changes caused by the subject's cardiac cycle (as described above).

[0613] For some applications, debris is generated by the frictional force between the drive cable and the outer tube 140. Optionally or additionally, a fluid (e.g., a cleansing fluid) is disposed between the drive cable and the outer tube. Generally, due to the windings of the coiled drive cable, the drive cable acts as an impeller and axially pumps debris and / or fluid relative to the outer tube 140. For some applications, the direction of the windings of the drive cable is such that the drive cable is configured to pump debris and / or fluid toward the proximal end of the ventricular assist device by rotating in a predetermined rotational direction and not pump debris and / or fluid toward the distal end of the ventricular assist device toward the patient's left ventricle.

[0614] Now refer to Figure 11A and Figure 11B , the Figure 11A and Figure 11B are schematic views of an interface component 154 for some applications of the present invention, which forms a junction between corresponding portions of the drive cable 130 of the ventricular assist device 20. For some applications, the drive cable includes a first portion and a second portion. Also referring again to Figure 10A , generally, the first portion is configured to be disposed in the aortic arch of the subject (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), and the second portion is generally configured to extend until the motor unit 23, outside the subject's body. Generally, at positions where the drive cable 130 undergoes significant bending, such as at the aortic arch, it is desirable for the drive cable to be relatively flexible. However, a drive cable with greater flexibility generally also stretches axially more than a drive cable with less flexibility. Thus, for some applications, there is a trade-off between desiring the drive cable to be flexible enough to conform to the curvature of the aortic arch but, on the other hand, not desiring the drive cable to undergo significant axial stretching (which could result in loss of control over the axial position of the impeller). For some applications, the corresponding portions of the drive cable have corresponding degrees of flexibility. For example, the first portion of the drive cable configured to be disposed in the aortic arch may have a first flexibility, while the second portion of the drive cable configured to be disposed in the descending aorta may have a second flexibility, with the first flexibility being greater than the second flexibility.

[0615] For some applications, the coils of the wire 134 in the first portion include fewer wires than in the second portion, and the first portion is configured to have greater flexibility than the second portion. For example, as Figure 11A - Figure 11BAs shown, the first part may include more than 4 wires and less than 8 wires (e.g., 4 - 8 wires, or 5 - 7 wires, e.g., 6 wires), and the second part may include more than 8 wires and less than 12 wires (e.g., 8 - 12 wires, or 9 - 11 wires, e.g., 10 wires). For some applications, the length of the first part 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 cm - 40 cm, or 25 cm - 35 cm. For some applications, the length of the second part 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), e.g., 60 cm - 100 cm, or 70 cm - 90 cm.

[0616] For some applications, the two parts of the drive cable are coupled to each other via interface component 154. Generally, the wires of the two parts are welded to the interface component. For some applications, groove 157 is cut into the interface component. The groove is configured such that the stress generated by the wires at the junction is distributed over the radius of the groove rather than concentrated at the point where the wires are welded to the interface component. For some such applications, the interface component further includes protrusion 158 which holds the wires in place during welding of the wires to the interface component.

[0617] Now referring to Figure 11C 、 Figure 11D and Figure 11E , Figure 11C 、 Figure 11D and Figure 11E are schematic views of the junction 156 between the drive cable and the axial shaft 92 for some applications of the ventricular assist device according to the present invention. For some applications, techniques substantially similar to those described with reference to Figure 11A - Figure 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 junction 156) includes a groove 157 and / or a protrusion 158 which are substantially as described above and are shown in Figure 11C .

[0618] Referring to Figure 11D , for some applications, when the coiled wire approaches the junction 156, the coiled wire is at least partially straightened (i.e., the pitch of the wire increases) such that the angle formed by the wire with the junction is not as sharp as the angle that would be formed if the wire were not straightened. By making the angle less sharp, the stress at the point where the wire is welded to the interface component is reduced. Referring to Figure 11E, for some applications, when the wire approaches the junction 156, in addition to being straightened, the wire is flattened and pushed radially inward. For some applications, the wire is flat enough that each wire in the coil contacts an adjacent wire to form a cylinder, as shown. For example, the shape of the wire can change from having a circular cross-section with a radius of approximately 0.2 mm to having 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 the wire on a mandrel, and squeezing the overtube and the wire radially inward. Subsequently, the overtube and the flattened wire are welded to the axial shaft 92 at the junction.

[0619] For some applications, techniques similar to those described with reference Figure 11D and Figure 11E are used to couple two portions of the drive cable to each other. For some applications, when the coiled wire approaches the interface member 154, the coiled wire is at least partially straightened (i.e., the pitch of the wire increases) such that the angle formed by the wire with the junction is not as sharp as the angle that would be formed if the wire were not straightened. By making the angle less sharp, the stress at the point where the wire is welded to the interface member is reduced. For some applications, when the wire approaches the interface member 154, in addition to being straightened, the wire is flattened and pushed radially inward. For some applications, the wire is flat enough that each wire in the coil contacts an adjacent wire to form a cylinder. For example, the shape of the wire can change from having a circular cross-section with a radius of approximately 0.2 mm to having 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 (not shown, but similar to overtube 159) around the wire, placing the overtube and the wire on a mandrel, and squeezing the overtube and the wire radially inward. Subsequently, the overtube and the flattened wire are welded to the interface member 154.

[0620] For some applications, a swaging technique is used to couple two portions of the drive cable to each other. For some such applications, the end portions of the inner tube and the outer tube are placed inside and outside, respectively, of the ends of the two portions of the drive cable that will form the junction between the portions. The inner tube is then placed on a rigid mandrel, and the inner tube, the outer tube, and the ends of the drive cable are forged together by applying pressure around the outside of the outer tube. Once the ends of the portions of the drive cable and the inner tube and the outer tube have been forged together, this forms the junction between the portions of the drive cable. For some applications, a similar swaging technique is performed to couple the drive cable to the axial shaft at the junction 156.

[0621] Now refer toFigure 12 , Figure 12 is a schematic view of a drive cable 130 of a ventricular assist device 20 for some applications in accordance with the present invention, the drive cable 130 including a friction reduction element 170 disposed around at least a portion of the drive cable. For some applications, the friction reduction element 170 is used to reduce friction between the drive cable 130 (which rotates during operation of the ventricular assist device) and an outer tube 142 (which remains stationary during rotation of the drive cable). In the example shown, the friction reduction element 170 is a ball bearing. However, the scope of the present invention includes using other friction reduction elements to reduce friction between the drive cable and the outer tube. For example, other rolling element bearings such as cylindrical rollers, spherical rollers, gear bearings, tapered rollers, needle rollers, and / or toroidal roller bearings can be used. For some applications, the friction reduction element is used as an alternative to including a first outer tube 140 in addition to the second outer tube 142. In Figure 12 the example shown, the friction reduction element is disposed between the drive cable and the second outer tube, and the ventricular assist device does not include a first outer tube and a second outer tube.

[0622] Generally, the ventricular assist device passes through the aortic arch of the subject and / or other generally curved portions of the vasculature of the subject. In the absence of a friction reduction element, the drive cable 130 and the tube 142 would typically contact each other, particularly at the curved portions of the vasculature. As described above, the drive cable 130 generally undergoes rotational movement relative to the tube 142 and, for some applications, also undergoes back-and-forth axial movement relative to the tube 142. Thus, in the absence of a friction reduction element (or the first outer tube 140 as described above), a significant amount of friction would be generated at the locations where the drive cable and the outer tube 142 contact each other. Therefore, for some applications, a friction reduction element is disposed between the drive cable 130 and the outer tube 142 to reduce the friction generated at the locations where the drive cable 130 and the outer tube 142 contact each other. For some applications, the friction reduction element is disposed between the drive cable 130 and the outer tube 142 generally along the entire length of the drive cable 130 and the outer tube 142. Alternatively, during operation of the ventricular assist device, the friction reduction element is disposed between the drive cable 130 and the outer tube 142 at locations where the drive cable 130 and the outer tube 142 are configured to be generally curved (e.g., at locations where the drive cable 130 and the outer tube 142 are disposed within the aortic arch).

[0623] Now refer to Figure 13 , Figure 13Schematic diagram of a procedure for purifying the drive cable 130 of a ventricular assist device 20 according to some applications of the present invention. For some applications, near the proximal bearing 116, the axial shaft 92 and the cable 130 are surrounded by a first outer tube 140 and a second outer tube 142, as described above. Generally, during rotation of the drive cable, both the first outer tube and the second outer tube remain stationary. For some applications, a purifying fluid (e.g., a fluid containing glucose or dextrose) is pumped between the first outer tube and the second outer tube, and there is an opening 146 near the proximal bearing within the first outer tube. As described above, generally, the purification system 29 ( Figure 1A as shown) controls the flow of the purifying fluid via the inlet 86 and the outlet 88 ( Figure 7 , Figure 8A and Figure 8B as shown). For some applications, the purifying fluid flows between the drive cable 130 and the first outer tube 140, as indicated by the purifying fluid flow arrow 148 in Figure 13 . In this way, the junction between the drive cable 130 (which rotates) and the outer tube 140 (which remains stationary during rotation of the drive cable) is purified. For some applications, some of the purifying fluid additionally flows to the junction between the axial shaft and the proximal bearing 116, thereby purifying this junction, as indicated by the purifying fluid flow arrow 149 in Figure 13 .

[0624] For some applications, the purifying fluid is pumped through the 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, in this way, some of the purifying fluid flows to the junction between the axial shaft and the distal bearing 118, thereby purifying this junction, as indicated by the purifying fluid flow arrow 150 in Figure 13 .

[0625] For some applications, a hemostatic valve 152 is provided at the distal end of the lumen 122 of the distal end portion 120, as described above. Optionally or additionally, a plug (not shown) is provided at the distal end of the lumen 122 of the end portion 120. Generally, the hemostatic valve and / or the plug prevent blood from flowing into the lumen 122 and / or the lumen 132. Further generally, by preventing the purifying fluid from flowing out of the distal end of the lumen 122, the plug causes the purifying fluid to flow to the junction between the axial shaft 92 and the distal bearing 118, as indicated by the purifying fluid flow arrow 150 in Figure 13 .

[0626] For some applications, the alternative techniques described above are used to direct a fluid (e.g., a fluid containing glucose) to the ventricular assist device. In Figure 13In the application shown, the fluid is allowed to flow distally after passing through the opening 146, as indicated by arrow 149 and as described above. However, for some applications, the flow of the fluid in the distal direction is blocked (i.e., there is no flow of the fluid as indicated by arrow 149). For some such applications, the fluid is initially released into the space between the drive cable 130 (which rotates) and the outer tube 140 (which remains stationary during rotation of the drive cable) such that the fluid fills the space between the drive cable and the outer tube 140 at a location near the opening 146. For example, as shown, the fluid can be pumped into the space via the gap between the first outer tube 140 and the second outer tube 142. Then, typically during the entire operation of the ventricular assist device, the fluid remains in place between the drive cable and the outer tube 140 at a location near the opening 146. The fluid is configured to remove air from the space between the drive cable and the outer tube, and / or is configured to reduce the friction between the drive cable 130 (which rotates) and the outer tube 140 (which remains stationary during rotation of the drive cable).

[0627] For some applications, a substantially similar technique is performed, but during operation of the ventricular assist device, the fluid is pumped between the drive cable 130 (which rotates) and the outer tube 140 (which remains stationary during rotation of the drive cable). For example, as shown, the fluid can be pumped into the space via the gap between the first outer tube 140 and the second outer tube 142. For some applications, during operation of the ventricular assist device, the fluid is continuously pumped between the drive cable and the outer tube, or during operation of the ventricular assist device, the fluid is periodically pumped between the drive cable and the outer tube. Note that even for such applications, the fluid is pumped between the drive cable and the outer tube, but does not flow into the bloodstream of the subject because the flow of the fluid in the distal direction is blocked, as described above. The pumping of the fluid is configured to remove air from the space between the drive cable and the outer tube to reduce the friction between the drive cable 130 (which rotates) and the outer tube 140 (which remains stationary during rotation of the drive cable), and / or is configured to remove debris generated by the ventricular assist device from the interface between the drive cable and the outer tube.

[0628] Now refer to Figure 14A and Figure 14B , Figure 14A and Figure 14BFIG. 0 is a schematic illustration of a frame 34 of a ventricular assist device 20 for 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 further detail below. Generally, the stator includes a plurality of curved protrusions 66 (e.g., more than 2 and / or less than 8 curved protrusions 66), which extend from the frame 34 when the device 20 is in a non-radially constrained configuration and are made of a flexible material (e.g., a polymer such as polyurethane and / or silicone). Generally, the curvature of the curved protrusions is such that it is opposite to the direction of rotation of the impeller, as described in further detail below. For some applications, by using curved protrusions (e.g., curved such that it is opposite to the direction of rotation of the impeller of the ventricular assist device, as described in further detail below), the stator 182 is configured to reduce the rotational flow component from the blood flow before the blood exits from the proximal end of the frame of the ventricular assist device.

[0629] As described above, generally, the device 20 is inserted into the ventricle of a subject via a catheter while the frame 34 is in a radially constrained state. When released from the catheter, the frame automatically assumes its unconstrained shape due to self-expansion of the frame 34. Generally, during insertion of the frame into the left ventricle, the curved protrusions of the stator are in a folded state and do not significantly increase the minimum diameter to which the frame can be radially constrained relative to the case where the tube does not include curved protrusions. When the frame 34 expands, since the curved protrusions are coupled to the frame 34, the curved protrusions are configured to automatically assume their curved configuration.

[0630] For some applications, the curved protrusions 66 are made of a flexible material (e.g., a polymer such as polyurethane and / or silicone). The curved protrusions are generally coupled to curved struts 186 of the frame 34, and the curvature of the curved struts thus defines the curvature of the curved protrusions. Generally, the flexible material is coupled to the frame 34 such that the flexible material defines a lumen 188 ( Figure 14B ) therethrough, which lumen 188 is aligned with the longitudinal axis of the frame. The axial axis 92 of the ventricular assist device generally enters the proximal end of the frame via the lumen 188.

[0631] For some applications, to facilitate attachment of the flexible material to the frame, to shape the flexible material into a desired shape, and / or to facilitate the formation of the lumen 188, a plurality of elongate elements 190 (e.g., strings and / or wires, which are typically made of a material similar to that of elongate element 67) are tied to the proximal end of the frame. For some applications, the curved struts 186 define a loop 192 or other coupling element at their distal ends, to which the elongate elements 190 are tied. The flexible material is typically attached to the frame such that the curved membranes of the material are supported by the curved struts and the elongate elements, each membrane defining a corresponding curved protrusion. For some applications, the strings and / or wires tied to the proximal end of the frame are tied together to define a circle 191, which defines one of the ends of the lumen 188. For example, during the formation of the stator, a mandrel can be placed through the proximal bearing 116, and the elongate elements can be tied to the loop 192 and caused to encircle the mandrel in order to define Figure 14B the pattern of elongate elements shown. Then the proximal end of the frame with the elongate elements and the mandrel is immersed in a material (which is typically a polymer such as silicone) while the material is in an uncured liquid state. Subsequently, the material is cured such that it solidifies, e.g., by allowing it to dry. Once the material has dried, the mandrel is typically removed. For some applications, the other end of the lumen 188 is defined by the proximal bearing 116 disposed at the proximal end of the frame 34. Typically, the flexible material extends from the circle 191 defined by the strings and / or wires to the proximal bearing 116 in order to define the lumen 188. For some applications, suture lines 189 are tied around the curved struts 186 in order to facilitate the attachment between the material and the struts, e.g., as described above with reference to the suture lines 53 of the impeller 50.

[0632] Now referring to Figure 15A , Figure 15A is a schematic view of the flat 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 loops 192 disposed towards the ends of each strut. Also referring to Figure 15B , Figure 15B is a schematic view showing an enlarged view of the proximal end of the frame 34 according to some applications of the present invention. Once the flexible material is attached to the curved struts, the ends 194 of the curved struts 186 typically define the orientation of the leading edges of the corresponding vanes (i.e., curved protrusions) of the stator. Also referring to Figure 15C , Figure 15C is a schematic view of the frame 34 according to some applications of the present invention, which shows the frame with the material defining the curved protrusions 66 attached to the frame. It can be observed that the orientation of the leading edges of the curved protrusions is defined by the orientation of the corresponding ends of the curved struts.

[0633] As Figure 15BAs shown in, the end 194 of the curved strut 186 is shaped to define an angle α relative to the axial component of the blood flow through the frame, which axial component is indicated by arrow 196 and is parallel to the longitudinal axis of the frame and towards the proximal end of the frame. As Figure 15C indicated, relative to the general direction of the blood flow, the leading edge of the corresponding curved projection typically also defines an angle approximately equal to angle α. (For some applications, when the strut 186 is radially expanded, the angle of the leading edge of the curved projection becomes slightly less than α.) For some applications, angle α is greater than 45 degrees (e.g., greater than 60 degrees), and / or less than 85 degrees (e.g., less than 80 degrees), e.g., 45 degrees - 85 degrees, or 60 degrees - 80 degrees.

[0634] The direction of rotation of the impeller is indicated by Figure 15C the arrow 198 in. As can be observed in Figure 15C the curvature of the curved projection is typically such that it is opposite to the direction of rotation of the impeller (which direction of rotation is the direction of the rotational flow component within the blood flow, as imparted to the blood flow by the impeller). From the distal end to the proximal end of the curved projection, the curved projection is curved to become gradually closer to parallel to the longitudinal axis of the frame. The curvature of the curved projection is such that it reduces the rotational flow component from the blood flow before the blood exits from the proximal end of the frame of the ventricular assist device.

[0635] Now referring to Figure 16A , Figure 16B , Figure 16C and Figure 16D , Figure 16A , Figure 16B , Figure 16C and Figure 16D are schematic views 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, generally, the ventricular assist device includes a tube 24 that passes through the aortic valve of the subject such that the proximal end of the tube is disposed within the aorta of the subject and the distal end of the tube is disposed within the left ventricle of the subject. Generally, a blood pump that typically includes an impeller 50 is disposed within the tube 24, within the left ventricle of the subject, and is configured to pump blood from the left ventricle into the aorta of the subject through the tube 24. For some applications, the blood pressure measurement tube 210 is configured to extend at least to the outer surface 212 of the tube 24 such that the 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. The pressure sensor 216 (in Figure 1AIn the schematic illustration), the blood pressure in the blood pressure measurement tube is measured. Generally, by measuring the blood pressure in the blood pressure measurement tube, the pressure sensor thereby measures the blood pressure of the subject outside the tube 24. Generally, the blood pressure measurement tube 210 extends from outside the subject's body to an opening 214 at the distal end of the tube, and the pressure sensor 216 is disposed toward the proximal end of the tube, for example, outside the subject's body. For some applications, the computer processor 25( Figure 1A ) receives an indication of the measured blood pressure and controls the pumping of blood through the impeller in response to the measured blood pressure.

[0636] Reference Figure 16A and Figure 16B , for some applications, one or more blood pressure measurement tubes include one or more left ventricular blood pressure measurement tubes 220 that are configured to extend to the outer surface of the blood pump tube 24 at a position along the tube that is configured to be within the left ventricle of the subject, near the blood pump (e.g., near the impeller 50). For such applications, the pressure sensor is configured to measure the left ventricular pressure of the subject by measuring the blood pressure 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 Figure 16A and Figure 16B shown. For some applications, based on the blood pressure measured in each left ventricular blood pressure measurement tube, the computer processor 25 determines whether the opening of one of the two or more left ventricular blood pressure measurement tubes is blocked. This can occur, for example, due to the opening contacting the wall of the interventricular septum and / or portions within different ventricles. Generally, in response to determining that the opening of one of the two or more left ventricular blood pressure measurement tubes is blocked, the computer processor determines the left ventricular pressure of the subject based on the blood pressure measured in a different one of the two or more left ventricular blood pressure measurement tubes.

[0637] For some applications, one or more blood pressure measurement tubes include one or more aortic blood pressure measurement tubes 222 that are configured to extend to the outer surface of the tube at a position along the tube that is configured to be within the aorta of the subject, as Figure 16C shown. For such applications, the pressure sensor is configured to determine the aortic pressure of the subject by measuring the blood pressure 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 Figure 16CAs shown. For some applications, based on the blood pressure measured within each aortic blood pressure measurement tube, computer processor 25 determines whether the opening of one of the two or more aortic blood pressure measurement tubes is blocked. This can occur, for example, due to the opening coming into contact with the wall of the aorta. Typically, in response to determining that the opening of one of the two or more aortic blood pressure measurement tubes is blocked, the computer processor determines the aortic pressure of the subject based on the blood pressure measured within a different one of the two or more aortic blood pressure measurement tubes.

[0638] For some applications, the ventricular assist device includes both a left ventricular blood pressure measurement tube and an aortic blood pressure measurement tube, both of which extend to the outer surface of tube 24, for example, as Figure 16C shown.

[0639] Still referring to Figure 16C , as described above, for some applications, drive cable 130 extends from a motor external to the subject's body to axial shaft 92 on which impeller 50 is disposed. Typically, the drive cable is disposed within outer tube 142. For some applications, the drive cable is disposed within first outer tube 140 and second outer tube 142, as described above. For some applications, one or more blood pressure measurement tubes are disposed within outer tube 142 surrounding the drive cable. For some applications, as shown, portions of one or more blood pressure measurement tubes are defined by the wall of outer tube 142. For some applications, within outer tube 142, the blood pressure measurement tubes have an elliptical cross-section (as shown). Typically, this increases the cross-sectional area of the tubes relative to the case where the tubes have a circular cross-section. Typically, within the distal portion of each of the blood pressure measurement tubes (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., 0.2 mm - 0.5 mm).

[0640] As Figure 16A shown, for some applications, at least one aortic blood pressure measurement tube 222 is used to measure aortic blood pressure, and the aortic blood pressure measurement tube 222 defines opening 219 at the distal end of outer tube 142. The aortic blood pressure measurement tube is configured to extend from outside the subject's body to the outer surface of outer tube 142 within the subject's aorta such that the opening at the distal end of the aortic blood pressure measurement tube is in direct fluid communication with the subject's aortic blood flow. Note that for such applications, the aortic blood pressure measurement tube does not extend to the outer surface of tube 24. Blood pressure sensor 216 is configured to measure the subject's aortic blood pressure by measuring the blood pressure within the aortic blood pressure measurement tube. For some applications, opening 219 in outer tube 142 is disposed within tube 24, as Figure 16DAs shown. The aortic pressure is measured via the opening 219 because the pressure in the tube 24 at a location downstream of the impeller is typically equal to the aortic pressure.

[0641] As Figure 16A and Figure 16B shown, for some applications, the outer tube 142 defines a groove 215 in a portion of the outer surface of the outer tube configured to be disposed within the tube 24. Typically, during insertion of the ventricular assist device into a subject's body, a portion of the blood pressure measurement tube 210 that extends from within the tube 24 to at least the outer surface of the tube 24 is configured to be disposed within the groove such that this portion of the blood pressure measurement tube does not protrude from the outer surface of the outer tube.

[0642] Now refer to Figure 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, and thereafter the blood pressure measurement tube can be built into the outer surface of the tube 24. For some applications, one or more tubes extend along the outer surface of the tube 24 in the manner Figure 16D shown, but these tubes extend all the way to the distal end of the tube 24 up to the distal portion 120 of the ventricular assist device. The tubes are used to inflate the inflatable portion of the distal portion, as described in further detail below with reference to Figure 21C

[0643] Although the ventricular assist device described with reference to Figure 16A - Figure 16D has been described as including a blood pump configured to be disposed within the left ventricle of a subject, for some applications, the blood pressure measurement tube 210 and the techniques described herein for use with the blood pressure measurement tube 210 are used with ventricular assist devices that include a blood pump elsewhere (e.g., within the aorta of a subject). For some applications, substantially similar techniques are used with right ventricular assist devices. For example, the device 20 can 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 measurement tube is used to measure the pressure in the right ventricle and / or the pulmonary artery. For some applications, a device substantially similar to the device 20 is used as a heart assist device by pumping blood 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 in the antegrade direction. For some such applications, the blood pressure measurement tube is used to measure the pressure in the right ventricle, vena cava, right atrium, and / or pulmonary artery.

[0644] ​In general, the scope of the present invention includes applying any of the devices and methods described herein to a right ventricular assist device, with necessary modifications. Right ventricular assist devices typically have a construction generally similar to that described herein and are used to pump blood from the right ventricle to the pulmonary artery, where tube 24 passes through the pulmonary artery semilunar valve. For some applications, the components of device 20 may be adapted to different types of blood pumps. For example, aspects of the present invention may be applicable to pumps for pumping blood from the vena cava and / or the right atrium into the right ventricle, from the vena cava and / or the right atrium into the pulmonary artery and / or from the renal vein into the vena cava. Such aspects may include features of pump section 27, impeller 50, drive cable 130, devices and methods for measuring blood pressure, devices and methods for measuring flow rate, and the like.

[0645] For some applications, wires extending (and typically extending from outside the subject's body) into the outer surface of blood pump tube 24 are used to perform techniques generally similar to those described with reference to blood pressure measurement tube 210, such that at least the end of the wire is 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 electrical parameters using a portion of the wire in electrical communication with the subject's blood flow outside tube 24.

[0646] Now referring to Figure 17A 、 Figure 17B and Figure 17C , Figure 17A 、 Figure 17B and Figure 17C are schematic views of outer tube 142 of ventricular assist device 20 according to some applications of the present invention, the outer tube including a pitot tube 225 configured to measure the blood flow through tube 24 of the device. Figure 17A - Figure 17C The portion of outer tube 142 shown in Figure 17A is generally disposed within tube 24. For some applications, a flow obstruction 226 (which is typically funnel-shaped) is configured to create a stagnation region near the stagnation pressure measurement port 227. For some applications, as shown in Figure 17BAs shown, the stagnation pressure measurement port is disposed close enough within the funnel-shaped flow obstruction 226 such that the flow obstruction itself serves to remove the vortical component of the flow before the blood reaches the stagnation pressure measurement port. For some applications, the stagnation pressure measurement port includes a short tube 233 that extends from the outer tube 142 within the funnel-shaped flow obstruction 226 such that the opening of the short tube 233 faces the direction of the axial blood flow through the tube 24. The outer tube 142 further defines an opening 219, which is generally as described above, and which serves as the static pressure measurement port 229. The pressures within the stagnation pressure measurement port 227 and within the static pressure measurement port 229 are measured using pressure sensors, e.g., pressure sensors disposed external to the body of the subject as described above with reference to Figure 16A - Figure 16D The pressure sensors described are disposed outside the body of the subject.

[0647] In some applications, the flow rate through the tube 24 is calculated based on the pressure measurements. For example, the flow rate through the tube 24 can be calculated using the following equation:

[0648]

[0649] where:

[0650] Q is the flow rate through the tube 24,

[0651] C is a calibration constant that is determined empirically and takes into account factors such as the impeller speed and the geometry of the pressure measurement ports 227 and 229,

[0652] A is the cross-sectional area of the tube 24 (excluding the area occupied by the outer tube 142),

[0653] ΔP is the difference between the stagnation pressure (measured via the pressure measurement port 227) and the static pressure (measured via the pressure measurement port 229)

[0654] p is the fluid density of the blood.

[0655] Now referring to Figure 18 , [[ID=Schematic diagram of a ventricular assist device 20 according to some applications of the present invention, the distal end portion 120 of the device being a radially expandable atraumatic distal end portion. As described above, a ventricular assist device typically includes a tube 24 that passes through the aortic valve of a subject such that the proximal portion of the tube is disposed within the aorta of the subject and the 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 within the distal portion of the tube and one or more blood outlet openings 109 within the proximal portion of the tube. A blood pump of the ventricular assist device configured to be disposed within the tube 24 pumps blood from the left ventricle into the tube 24 through one or more blood inlet openings and pumps the blood out of the tube 24 into the aorta through one or more blood outlet openings. Typically, the radially expandable atraumatic distal end portion 120 is disposed distally within the left ventricle of the subject relative to one or more blood inlet openings. The distal end portion is configured to be inserted into the left ventricle in a radially constrained configuration. Typically, during insertion of the distal end portion into the left ventricle, at least a portion of the distal end portion is disposed within a delivery catheter 143 (such as shown in ​ ), and the delivery catheter holds the distal end portion in a radially constrained configuration. The distal end portion is configured to assume a non-radially constrained configuration within the left ventricle of the subject, wherein at least a portion 232 of the distal end portion radially expands relative to the radially constrained configuration of the distal end.

[0656] For some applications, the radially expandable atraumatic distal end portion 120 includes a frame 234 made of a shape memory material such as nitinol, the frame being shaped such that it radially expands when released from the delivery catheter. Typically, the frame is covered with a biocompatible blood-impermeable material 236 such as polyurethane, polyester, and / or silicone, which is typically configured to form a continuous surface covering the frame. For some applications, the distal end portion further includes an atraumatic distal tip 238, which may have a shape similar to that of the distal end portion 120, as described above with reference to ​ and / or below with reference to Figure 21B .

[0657] The radially expandable atraumatic distal end portion 120 is typically configured such that in the non-radially constrained configuration of the distal end portion, the radially expandable portion 232 of the distal end portion separates one or more blood inlet openings 108 from the internal structures of the left ventricle in three dimensions. In this way, the radially expandable portion 232 of the distal end portion separates one or more blood inlet openings 108 from the interventricular septum, chordae tendineae, papillary muscles, and / or the apex of the left ventricle. For some applications, the radially expandable portion 232 of the distal end portion is shaped such that it directs blood flow from the left ventricle into one or more blood inlet openings, as shown by Figure 18as indicated by arrow 240 therein.

[0658] Now refer to Figures 19A - 19B which Figures 19A - 19B is a schematic illustration of a ventricular assist device 20 for some applications in accordance with the present invention, wherein the ventricular assist device distal end portion 120 of the device is a radially expandable atraumatic distal end portion. Also refer to Figures 20A - 20B which Figures 20A - 20B is a schematic illustration of a ventricular assist device 20 for some alternative applications in accordance with the present invention, wherein the ventricular assist device distal end portion 120 of the device is a radially expandable atraumatic distal end portion. Figure 19A and Figure 20A show the distal end portion in its radially constrained configuration, while the distal end portion is at least partially disposed within the delivery catheter 143, and Figure 19B and Figure 20B show the distal end portion in its non-radially constrained configuration. Generally, as the distal end portion 120 shown in Figures 19A - 19B and Figures 20A - 20B has a function generally similar to that described for the distal end portion 120 shown in Figure 18 above.

[0659] As described above, generally, during insertion of the distal end into the left ventricle, at least a portion of the distal end portion 120 is disposed within the delivery catheter 143, and the delivery catheter holds the distal end portion in a radially constrained configuration, as shown in Figure 19A and Figure 20AAs shown. For some applications, the distal end portion is configured such that when the delivery catheter holds the distal end portion in a radially constrained configuration, the distal region 244 of the distal end portion projects from the distal end of the delivery catheter. Generally, at least in the radially constrained configuration of the distal end portion, the distal region is at least semi-rigid and shaped to radially converge in the longitudinal direction toward the distal end 246 of the distal end portion. Generally, the delivery catheter is inserted into the vasculature of a subject via a puncture. For some applications, the radially converging semi-rigid distal region of the distal end portion is configured to act as a dilator by enlarging the puncture during insertion of the delivery catheter through the puncture. In this way, the delivery catheter and components of the ventricular assist device disposed within the delivery catheter can be inserted through the puncture without the need to pre-enlarge the puncture and without the need for a separate introducer device to facilitate insertion of the delivery catheter through the puncture. For some applications, the distal region is configured to allow percutaneous insertion of the catheter into a punctured blood vessel by placing a first guide wire through the distal region of the distal end portion. Subsequently, by tracking the path and shape of a second guide wire having less stiffness than the first guide wire, the distal region is used to guide the catheter along an arcuate anatomy (such as the aortic arch). For some such applications, the delivery catheter 143 itself acts as an introducer. Generally, 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.

[0660] For some applications, the distal end portion 120 is configured such that in the non-radially constrained configuration of the distal end portion, the distal end 246 of the distal end portion is encapsulated within the radially expandable portion 232 of the distal end 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 end portion can include a spring 249 and / or an elastic material configured to retract the distal end of the distal end portion, as shown in the transition from Figures 19A to 19B As shown. For some applications, the distal end flips such that the distal end becomes encapsulated within the radially expandable portion of the distal end portion. For example, the transition from Figures 20A to 20B shows the distal end 246 of the distal end portion 120 flipping, as indicated by the arrow 264. For some applications, by the distal end becoming encapsulated within the radially expandable portion, the distal end is prevented from becoming entangled within the chordae tendineae and / or from causing damage to the internal structures of the left ventricle.

[0661] Reference Figure 19B, for some applications, the distal end portion includes a plurality of longitudinal struts 248 that are shaped to bend radially outward. Typically, the struts are made of a shape memory material such as nitinol. For some applications, the struts are covered with a biocompatible blood-impermeable material 250 such as polyurethane, polyester, and / or silicone, which is generally configured to form a continuous surface covering the struts. Refer to Figure 20B , for some applications, the distal end portion includes a braided shape memory material 260. For some applications, the braided shape memory material is at least partially covered with a biocompatible blood-impermeable material 262 such as polyurethane, polyester, and / or silicone, which is generally configured to form a continuous surface covering the braided shape memory material. Alternatively, the braided shape memory material is not covered.

[0662] Now refer to Figure 21A , Figure 21B , Figure 21C and Figure 21D , Figure 21A , Figure 21B , Figure 21C and Figure 21D are schematic views of the distal end portion 120 of a ventricular assist device 20 according to some applications of the present invention, and the distal end portion is configured to be atraumatic. As Figure 21A shown, for some applications, the distal end portion includes a J-shaped end 270 at its distal end. As Figure 21B shown, for some applications, the distal end portion includes a spherical end 272 at its distal end. As Figure 21A and Figure 21B shown, for some applications, at a position near the J-shaped end or the spherical end, the distal end portion is externally shaped to define a frustum 274. Generally, the proximal end 276 of the frustum serves as a stopper to prevent the delivery catheter 143 from advancing past the proximal end in a manner substantially similar to that described for the flared portion 124 with reference to Figure 6C .

[0663] For some applications, the end portion has a straightened configuration, wherein the end portion is shaped to define a frustum that extends from the proximal end of the frustum to the distal end of the distal end portion. For example, a guide wire (such as guide wire 10) inserted through the lumen 122 defined by the end portion ( Figures 6A - 6C shown) can hold the end portion in its straightened configuration. For some such applications, the end portion has an unconstrained configuration (the end portion is configured to assume this configuration within the ventricle (e.g., due to the removal of the guide wire from within the end portion)), wherein the distal portion of the frustum is shaped as a J-shaped end, as Figure 21A shown.

[0664] As Figure 21C shown, for some applications, the outer surface of the distal end portion includes an expandable portion 278 (e.g., a balloon), which is configured to be inflated when the distal end portion is placed within the left ventricle of a subject. For some such applications, the inflation lumen for inflating the expandable portion is configured to pass through the outer tube 142, and then pass along the outer surface of the tube 24, and reach the expandable portion of the distal end portion. For example, the inflation lumen may be constructed in a manner substantially similar to the blood pressure measurement tube 210 as Figure 16D shown, but may continue to extend along the outer surface of the tube 24 until the distal end of the tube, and then continue to the expandable portion of the distal end portion. For some applications, the distal end of the distal end portion includes a domed portion 280. As described above, generally, the distal end portion includes a hemostatic valve 152 at its distal end.

[0665] As Figure 21D shown, for some applications, the outer surface of the distal end 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 end portion is disposed within the left ventricle of a subject.

[0666] As Figure 21C and Figure 21D shown, the atraumatic distal end portion 120 is generally configured such that in the inflated or radially expanded configuration of the distal end portion, the inflated portion or the radially expanded portion of the distal end portion separates one or more blood inlet openings 108 from the internal structures of the left ventricle in three dimensions. In this way, the inflated portion or the radially expanded portion of the distal end portion separates one or more blood inlet openings 108 from the interventricular septum, chordae tendineae, papillary muscles, and / or the apex of the left ventricle. For some applications, the inflated portion or the radially expanded portion of the distal end portion is shaped such that blood flow is directed from the left ventricle into one or more blood inlet openings, as described above with reference to the distal end portion 120 as Figure 18 shown.

[0667] Now refer to Figure 22A and Figure 22B , Figure 22A and Figure 22BSchematic views of the distal end portion 120 of the ventricular assist device 20 in an axially reinforced configuration and a non-axially reinforced configuration, respectively, according to some applications of the present invention. As described above, for some applications, the distal end portion is configured such that when the delivery catheter holds the distal end portion in a radially constrained configuration, the distal region 244 of the distal end portion projects from the distal end of the delivery catheter. Generally, at least in the axially reinforced configuration of the distal end portion, the distal region is at least semi-rigid and shaped to radially converge in the longitudinal direction toward the distal end 246 of the distal end portion. Generally, the delivery catheter is inserted into the vasculature of the subject via a puncture. Additionally, generally, the distal end portion defines a lumen 122 through which the guide wire 10 is inserted, as described above. For some applications, the radially converging semi-rigid distal region of the distal end portion is configured to act as a dilator by enlarging the puncture during insertion of the delivery catheter via the puncture. In this way, the delivery catheter and the components of the ventricular assist device disposed within the delivery catheter can be inserted into the puncture without the need to pre-enlarge the puncture and without the need for a separate introducer device to facilitate insertion of the delivery catheter through the puncture. For some applications, the distal region is configured to allow percutaneous insertion of a catheter into a punctured blood vessel by placing a first guide wire through the distal region of the distal end portion. Subsequently, the distal region is used to guide the catheter along an arcuate anatomy (e.g., the aortic arch) by tracking the path and shape of a second guide wire having less stiffness than the first guide wire. For some such applications, the delivery catheter 143 itself serves as the introducer. Generally, 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.

[0668] For some applications, the distal end portion is made of a flexible material (such as silicone), with a spring 290 disposed around the lumen 122. During insertion of the ventricular assist device into the body of the subject, a rigid or semi-rigid reinforcing element 292 (e.g., a rigid or semi-rigid tube) is placed within the distal region 244 of the distal end portion to reinforce the distal region. This configuration is shown in Figure 22A Subsequently, the reinforcing element is retracted such that the distal region of the distal end portion becomes atraumatic (e.g., elastic and flexible), as shown in Figure 22B

[0669] Now refer to Figure 23A and Figure 23B , Figure 23A and Figure 23B ​Schematic views of the distal end portion 120 of a ventricular assist device 20 in a radially constrained configuration and a non-radially constrained configuration, respectively, for some applications of the present invention. For some applications, the distal region 144 of the distal end portion is shaped as a cone, in which there are slits 294 (e.g., two slits). During insertion of the ventricular assist device into a subject's body, the distal region maintains its conical shape through a delivery catheter 143. This configuration is shown in Figure 23A . Subsequently, when the delivery catheter is retracted, the distal region is configured to form a two-dimensional circular or elliptical shape by splitting into two semi-circular 296 or semi-elliptical shapes around the slits, as shown in Figure 23B . In the configuration shown in Figure 23B , the distal end portion is generally configured to be atraumatic and is configured to separate one or more blood inlet openings 108 from the internal structure of the left ventricle in two dimensions. In this way, the distal end portion separates one or more blood inlet openings 108 from the interventricular septum, chordae tendineae, papillary muscles, and / or the apex of the left ventricle.

[0670] Now refer to Figure 24A and Figure 24B , Figure 24A and Figure 24B are schematic views of the distal end portion 120 of a ventricular assist device 20 in a radially constrained configuration and a non-radially constrained configuration, respectively, for some applications of the present invention. For some applications, the distal region 244 of the distal end portion is shaped as a cone, in which there are slits 294 (e.g., four slits). During insertion of the ventricular assist device into a subject's body, the distal region maintains its conical shape through a delivery catheter 143. This configuration is shown in Figure 24A . Subsequently, 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 . (Note that the fourth arm is hidden from view in Figure 24B .) In the configuration shown in Figure 24B , the distal end portion is generally configured to be atraumatic and is configured to separate one or more blood inlet openings 108 from the internal structure of the left ventricle in three dimensions. In this way, the distal end portion separates one or more blood inlet openings 108 from the interventricular septum, chordae tendineae, papillary muscles, and / or the apex of the left ventricle.

[0671] For some applications, the distal end portion 120 has a pointed distal region 244, and the diameter of the distal end portion at the proximal end of the distal region is 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 one-quarter) of the total length of the distal end portion. Additionally, typically, the pointed distal region is more flexible than the proximal region of the distal end portion. Typically, the distal region is configured to be straightened into a generally conical shape when a sufficiently rigid guide wire is inserted therein. For some applications, the distal region is configured to curl into a J-shape (e.g., as shown in Figure 21A ).

[0672] Typically, the distal region of the distal end portion serves as a dilator for the delivery catheter 143 to allow percutaneous insertion of the catheter into a punctured blood vessel by placing a first guide wire through the distal region of the distal end portion. Subsequently, the distal end portion is used to guide the catheter along an arcuate anatomy (e.g., the aortic arch) by tracking the path and shape of a second guide wire that is less stiff than the first guide wire. For some applications, as described above, the distal region of the distal end portion is configured to curl when the second guide wire is withdrawn.

[0673] For some applications, the features of the distal end portion 120 described with reference to Figures 18 - 24B and the techniques for practicing it are combined with the features of the end portion 120 described with reference to Figures 6A - 6C and / or Figure 13 above.

[0674] Now referring to Figure 25A , Figure 25A is a schematic illustration of a first portion 160A and a second portion 160B of a coupling element according to some applications of the present invention, the coupling element being configured to facilitate radial contraction (e.g., during collapse) of an impeller (e.g., the impeller 50 described above) independently of other components of a ventricular assist device. The first portion 160A and the second portion 160B are configured to become engaged with each other. The first portion is disposed on the impeller, and the second portion is disposed on the frame 34, e.g., on the distal bearing 118 of the frame 34. Note that, for illustrative purposes, only certain portions of the impeller are shown in Figure 25A .

[0675] Also referring to Figure 25B and Figure 25C , Figure 25B and Figure 25CSchematic diagrams of the various stages of collapse of an impeller for some applications in accordance with the present invention. For some applications, prior to collapsing an outer portion of a ventricular assist device (e.g., the frame 34 of the left ventricular assist device 20 as shown), the impeller is radially contracted by bringing portions 160A and 160B into engagement with each other and axially elongating the impeller. Subsequently, the outer portion of the left ventricular assist device is radially contracted. For some applications, collapsing the impeller in this manner reduces the likelihood that the impeller becomes damaged during the collapse of the outer portion of the left ventricular assist device. Subsequently, when the impeller and the frame are disposed within the left ventricle of a subject, a first portion and a second portion of the coupling element separate from each other such that the impeller is able to move relative to the frame 34.

[0676] For Figures 25A - 25C Optionally or additionally, as described above, for the collapse technique shown, the impeller is configured to be coupled to an axial shaft by only one of the ends of the impeller (e.g., the proximal end of the impeller) and the other end (e.g., the distal end) is slidable relative to the axial shaft to become collapsed. The impeller becomes collapsed by sliding the other end of the impeller along the shaft such that the impeller becomes axially elongated.

[0677] Now refer to Figure 26 , Figure 26 Schematic diagram of a blocker 300 for some applications in accordance with the present invention, the blocker 300 being configured to prevent distal advancement of the impeller 50 of the ventricular assist device 20 during withdrawal of the ventricular assist device from the body of a subject. As described above, typically, in order to withdraw the ventricular assist device from the body of a subject, the delivery catheter 143 is advanced distally over the frame 34 and the impeller 50 so as to cause the frame and the impeller to assume their radially constrained configuration. In some cases, there is a risk that the drive cable 130 may break when the impeller is pushed distally by the delivery catheter. For some applications, in the case where the drive cable breaks, subsequent distal advancement of the proximal end of the impeller causes the blocker 300 to engage the shoulder 302, thereby preventing further advancement of the proximal end of the impeller. It should be noted that the blocker is configured such that during normal operation of the ventricular assist device (and throughout the axial back-and-forth movement cycle described above), the blocker does not engage the shoulder 302.

[0678] For some applications (not shown), a plurality of electrodes are disposed on the distal portion of the left ventricular assist device. The computer processor 25 ( Figure 1A)A current is applied between the most distal electrode and the most proximal electrode, with the most distal electrode typically configured to be positioned near the apex of the heart and the most proximal electrode typically configured to be positioned above the aortic valve. The conductance of the current between each pair of electrodes is then measured by a computer processor. For some applications, the application of the current and the conductance measurement are performed using a technique that is generally similar to the technique described in the article by Cassidy et al., titled “The Conductance Volume Catheter Technique for Measurement of Left Ventricular Volume in Young Piglets” (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, the computer processor controls the rotational speed of the impeller in response to the derived pressure-volume loop.

[0679] Regarding the reference Figures 1A - 26 all aspects of the ventricular assist device 20 described, note that although Figure 1A and Figure 1BThe ventricular assist device 20 in the left ventricle of a subject is shown, but for some applications, the device 20 is placed in the right ventricle of the subject such that the device passes through the pulmonary valve of the subject, and the techniques described herein are applied with necessary modifications. For some applications, the components of the device 20 can be adapted for different types of blood pumps. For example, aspects of the present invention can be adapted for pumps for pumping blood from the vena cava and / or the right atrium into the right ventricle, from the vena cava and / or the right atrium into the pulmonary artery, and / or from the renal vein into the vena cava. Such aspects can include features of the impeller 50, the pump portion 27, the drive cable 130, devices and methods for measuring blood pressure, etc. Optionally or additionally, the device 20 and / or a portion thereof (e.g., the impeller 50, even in the absence of the tube 24) is placed within a different part of the subject's body to assist in pumping blood from that part. For example, the device 20 and / or a portion thereof (e.g., the impeller 50, even in the absence of the tube 24) can be placed in a blood vessel and can be used to pump blood through the blood vessel. For some applications, with necessary modifications, the device 20 and / or a portion thereof (e.g., the impeller 50, even in the absence of the tube 24) is configured to be placed in the subclavian vein or the jugular vein at the junction of the vein and the lymphatic duct and is used to increase the flow of lymphatic fluid from the lymphatic vessel into the vein. Since the scope of the present invention includes the use of the devices and methods described herein in anatomical locations other than the left ventricle and the aorta, the ventricular assist device and / or a portion thereof is sometimes referred to herein (in the specification and claims) as a blood pump.

[0680] Now referring to Figure 27A and 27B which Figure 27A and 27B are schematic views of a ventricular assist device 308 according to some applications of the present invention, the device including a valve 70 to prevent backflow of blood, for example, in the event of a failure of the impeller 50 of the ventricular assist device. Different from the ventricular assist device 20 described above with reference to Figures 1A - 26 , the ventricular assist device 308 includes an impeller (e.g., as described in Tuval's WO 18 / 078615, which is incorporated herein by reference) disposed within the aorta and not within the left ventricle. For some applications, the impeller is constructed 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) that passes through the aortic valve, and a frame 310 supports the tube in an open configuration. Figure 27A shows the ventricular assist device constructed when the impeller of the ventricular assist device is operating normally such that there is a blood flow from the left ventricle 22 via the tube 312 (which passes through the aortic valve 26) to the aorta 30, which blood flow is indicated by the arrow 72.

[0681] For some applications, the tube 312 includes a valve 70 located in a region of the tube, the valve 70 being configured to be disposed distally relative to the impeller 50 and near the aortic valve, as Figure 27B shown. For example, in the case where the impeller 50 fails such that there is a backflow of blood through the tube 312 (as indicated by the Figure 27B blood flow arrow 73 in

[0682] ), the leaflets of the valve 70 are configured to close such that there is substantially no reverse blood flow from the aorta to the left ventricle. For some applications (not shown), the tube 312 includes a valve 70 at the proximal end of the tube, the valve 70 being configured to be disposed in the aorta. Figure 28A 、 Figure 28B and Figure 28C , Figure 28A 、 Figure 28B and Figure 28C are schematic views of a ventricular assist device 308 according to some applications of the present invention, the device including a safety bladder 80 to prevent backflow of blood, for example, in the case where the impeller of the ventricular assist device fails. Different from the ventricular assist device 20 described above with reference to Figures 1A - 26 , the ventricular assist device 308 includes an impeller disposed within the aorta and not in the left ventricle (e.g., as described in Tuval's WO18 / 078615, which is incorporated herein by reference). For some applications, the impeller is constructed in a manner substantially 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 passes through the aortic valve, and the frame 310 supports the tube in an open configuration. Figure 28A shows the ventricular assist device constructed when the impeller of the ventricular assist device is operating normally such that there is a blood flow from the left ventricle 22 through the tube 312 (which passes through the aortic valve 26) to the aorta 30, the blood flow being indicated by the arrow 72. For some applications, the ventricular assist device 308 includes a bladder 80 located in a region of the tube, the bladder 80 being configured to be disposed distally relative to the impeller 50 and near the aortic valve, as Figure 28B shown. For example, in the case where the impeller 50 fails such that there is a backflow of blood through the tube 312 (as indicated by the Figure 28B blood flow arrow 73 in

[0683] ), the computer processor 25 is configured to inflate the bladder such that the tube 312 becomes blocked and there is substantially no reverse blood flow from the aorta to the left ventricle. Figure 28C For some applications, the ventricular assist device 308 includes a bladder 80 located at the distal end of the tube 312, the bladder 80 being configured to be disposed in the left ventricle, as Figure 28CIn the case where the blood flow arrow 73 (indicated in) is present, the computer processor 25 is configured to inflate the sac such that the tube 312 becomes blocked and there is substantially no reverse blood flow from the aorta to the left ventricle.

[0684] 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:

[0685] International Patent Application PCT / IL2017 / 051273, entitled "Blood pumps", filed by Tuval on November 21, 2017 (published as WO 18 / 096531), which claims priority from U.S. Provisional Patent Application 62 / 425,814, filed by Tuval on November 23, 2016;

[0686] International Application No. PCT / IL2017 / 051158, entitled "Ventricular assist device", filed by Tuval on October 23, 2017 (published as WO 18 / 078615), which claims priority from U.S. 62 / 412,631, filed by Tuval on October 25, 2016, and U.S. 62 / 543,540, filed by Tuval on August 10, 2017;

[0687] International Patent Application PCT / IL2017 / 051092, entitled "Blood vessel tube", filed by Tuval on September 28, 2017 (published as WO 18-061002), which claims priority from U.S. Provisional Patent Application 62 / 401,403, filed by Tuval on September 29, 2016;

[0688] Schwammenthal's US 2018 / 0169313, which is the U.S. national stage of International Patent Application PCT / IL2016 / 050525, entitled "Blood pump", filed by Schwammenthal on May 18, 2016 (published as WO 16 / 185473), which claims priority from U.S. Provisional Patent Application 62 / 162,881, entitled "Blood pump", filed by Schwammenthal on May 18, 2015;

[0689] US 2017 / 0100527 of Schwammenthal, which is the U.S. national stage of the international patent application PCT / IL2015 / 050532 (published as WO 15 / 177793) titled "Blood pump" filed by Schwammenthal on May 19, 2015, and this application claims the priority of the U.S. provisional patent application 62 / 000,192 titled "Blood pump" filed by Schwammenthal on May 19, 2014;

[0690] U.S. Patent US 10,039,874 of Schwammenthal, which is the U.S. national stage of the international patent application PCT / IL2014 / 050289 (published as WO 14 / 141284) titled "Renal pump" filed by Schwammenthal on March 13, 2014, and this patent claims the priority of the following patent applications: (a) the U.S. provisional patent application 61 / 779,803 titled "Renal pump" filed by Schwammenthal on March 13, 2013, and (b) the U.S. provisional patent application 61 / 914,475 titled "Renal pump" filed by Schwammenthal on December 11, 2013;

[0691] U.S. Patent 9,764,113 of Tuval titled "Curved catheter" authorized on September 19, 2017, which claims the priority of the U.S. provisional patent application 61 / 914,470 titled "Curved catheter" filed by Tuval on December 11, 2013, and

[0692] U.S. Patent 9,597,205 of Tuval, which is the U.S. national stage of the international patent application PCT / IL2013 / 050495 (published as WO 13 / 183060) titled "Prosthetic renal valve" filed by Tuval on June 6, 2013, and this patent application claims the priority of the U.S. provisional patent application 61 / 656,244 titled "Prosthetic renal valve" filed by Tuval on June 6, 2012.

[0693] Those skilled in the art should recognize that the present invention is not limited to what has been particularly shown and described above. Rather, the scope of protection of the present invention includes combinations and sub - combinations of the various features described above, as well as variations and modifications of the present invention that are not in the prior art and can be conceived by those skilled in the art upon reading the foregoing description.

Claims

1. An apparatus, the apparatus comprising: a ventricular assist device (20), the ventricular assist device (20) comprising: an impeller (50), the impeller (50) being configured to be placed within the left ventricle of a subject, the impeller (50) comprising a proximal bushing and a distal bushing (64, 58); a frame (34), the frame (34) being configured to be disposed around the impeller (50), the frame (34) comprising a proximal bearing and a distal bearing (116, 118); an axial shaft (92), the axial shaft (92) being configured to pass through the proximal bearing and the distal bearing (116, 118) defined by the frame (34) and the proximal bushing and the distal bushing (64, 58) of the impeller (50), the axial shaft (92) being coupled to at least one of the proximal bushing and the distal bushing (64, 58) of the impeller (50) such that the at least one bushing is maintained in an axially fixed position relative to the axial shaft (92); and a motor (74), the motor (74) being configured to drive the impeller (50) by rotating the impeller (50) to pump blood from the left ventricle to the aorta of the subject, wherein the axial shaft (92) is not maintained in an axially fixed position relative to the proximal bearing and the distal bearing (116, 118) such that the entire impeller (50) is configured to move axially back and forth relative to the frame (34) in response to periodic changes in the pressure differential between the left ventricle and the aorta.

2. The apparatus according to claim 1, wherein the ventricular assist device (20) does not include any thrust bearings configured to be disposed within the body of the subject.

3. The apparatus according to claim 1, wherein the ventricular assist device further comprises one or more thrust bearings, the one or more thrust bearings being configured to be disposed outside the body of the subject, and wherein counteraction of the thrust generated by the rotation of the impeller (50) is provided only by the one or more thrust bearings disposed outside the body of the subject.

4. The apparatus according to claim 1, wherein the motor (74) is configured to drive the impeller (50) by rotating the impeller (50) in a given direction of rotation to pump blood from the left ventricle of the subject to the aorta of the subject; and the ventricular assist device further comprises: a drive cable, the drive cable being configured to extend from outside the body of the subject to the axial shaft (92), the drive cable being configured to transmit rotational motion from the motor (74) to the impeller (50) by rotation, at least a portion of the drive cable comprising multiple wires disposed in a coiled configuration such that in response to the drive cable rotating in the given direction of rotation, the multiple wires disposed in the coiled configuration at least partially unwind such that the portion of the drive cable axially shortens.

5. The apparatus according to any one of claims 1 - 4, further comprising: A sensor configured to detect an indication of axial movement of the impeller (50) and configured 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.

6. The apparatus according to any one of claims 1 - 4, further comprising: A magnet, the impeller (50) being coupled to the magnet such that axial movement of the impeller (50) causes axial movement of the magnet; A sensor configured to detect magnetic flux generated by the magnet and configured 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.

7. The apparatus according to claim 5 or claim 6, wherein the computer processor is configured to generate an output indicative of the cardiac cycle of a subject in response to receiving the sensor signal.

8. The apparatus according to claim 5 or claim 6, wherein the computer processor is configured to determine the left ventricular pressure of a subject at least in part based on the sensor signal.

9. The apparatus according to claim 5 or claim 6, wherein the computer processor is configured to change the rotational speed of the impeller (50) at least in part based on the sensor signal.

10. The apparatus according to claim 9, wherein the computer processor is configured to: Determine the left ventricular pressure of a subject at least in part based on the sensor signal, and Change the rotational speed of the impeller (50) at least in part based on the determined left ventricular pressure.

11. The apparatus according to claim 10, wherein the computer processor is configured to reduce the rotational speed of the impeller (50) in response to determining that the left ventricular pressure of the subject has decreased.

12. The apparatus according to claim 1, wherein: The impeller (50) is coupled to the axial shaft (92) such that the impeller (50) causes the axial shaft (92) to move axially back and forth relative to the proximal bearing and the distal bearing (116, 118) of the frame (34).

13. The apparatus according to claim 12, wherein the axial shaft (92) is configured to clean the junction between the axial shaft (92) and the proximal bearing and the distal bearing (116, 118) of the frame (34) by moving axially back and forth relative to the proximal bearing and the distal bearing (116, 118) of the frame (34).

14. The device according to claim 13, wherein the axial shaft (92) is configured to reduce heat accumulation at the junction between the axial shaft (92) and the proximal and distal bearings (116, 118) of the frame (34) by making the axial back-and-forth movement relative to the proximal and distal bearings (116, 118) of the frame (34), as compared to the case where the axial shaft (92) does not make the axial back-and-forth movement relative to the proximal and distal bearings (116, 118) of the frame (34).

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