Ventricular assist device

Abstract

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

Description

[0001] This application is a divisional application of application number 201980007116.9, filed on January 10, 2019, having the title "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-cited applications are incorporated herein by reference.

[0009] Field of the Embodiments of the Invention

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

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

[0012] SUMMARY OF THE EMBODIMENTS

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

[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 shaft generally passes through the proximal and distal bearings of the frame and the proximal and distal bushings of the impeller. For some applications, (a) the proximal bushing of the impeller is coupled to the axial shaft such that the proximal bushing is held in an axially fixed position relative to the axial shaft, and (b) the distal bushing of the impeller is not coupled to the axial shaft such that the distal bushing is not held in an axially fixed position relative to the axial shaft. Generally, the impeller defines a radially constrained configuration in which the impeller is introduced into the subject's body and a non-radially constrained configuration in which the impeller is configured to pump blood within the subject's body. For some applications, the impeller is changed from its radially constrained configuration to its non-radially constrained configuration by the distal bushing sliding on the axial shaft.

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

[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 difference between the left ventricle and the aorta. For some applications, the computer processor measures an indication of the axial motion of the impeller. For some applications, the computer processor derives a cardiac cycle of the subject, a pressure difference between the left ventricle and the aorta, and / or a left ventricular pressure of the subject based on the measured indication of the axial motion of the impeller. For some applications, the computer processor changes a rate of rotation of the impeller based at least in part on the sensor signal. For example, the computer processor can determine a left ventricular pressure of the subject based at least in part on the sensor signal, and can change the rate of rotation of the impeller based at least in part on the determined left ventricular pressure. For some applications, the computer processor decreases the rate of rotation of the impeller in response to determining that the left ventricular pressure of the subject has decreased. For some applications, the impeller is coupled to a magnet such that axial motion of the impeller causes the magnet to move axially, and the computer processor measures the indication of the axial motion of the impeller by measuring a magnetic flux generated by the magnet.

[0017] Generally, a drive cable extends from outside the subject’s body to the axial shaft, and is configured to transmit rotational motion from the motor to the impeller by rotation such that the impeller pumps blood from the left ventricle to the aorta by rotation in a given direction. For some applications, 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 being rotated in a given rotational direction, the plurality of wires disposed in the coiled configuration at least partially uncoil such that the 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 such that debris is generally generated. Alternatively or additionally, a fluid (e.g., a purifying 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 plurality of wires disposed in the coiled configuration are configured to pump the debris and / or the fluid toward a proximal end of the drive cable.

[0018] For some applications, the drive cable includes a first portion configured to be at least partially disposed within an aortic arch of the subject, and a second portion configured to be at least partially disposed within a descending aorta of the subject, and the first portion is more flexible than the second portion. For example, the first portion of the drive cable can include a first number of wires disposed in a coiled configuration, and the second portion of the drive cable can include a second number of wires disposed 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 disposed in a coiled configuration, and the second portion of the drive cable can include between 8 and 12 wires disposed in a coiled configuration.

[0019] For some applications, the impeller includes at least one helical elongated element (and typically three helical elongated elements), and a spring disposed inside the helical elongated element and around an axis about which the helical elongated element is wound. Typically, a membrane of material (e.g., silicone) is supported between the helical elongated element and the spring. For some applications, at least one elongated element (e.g., a string or wire) extends from the spring to the helical elongated element and is configured to hold the helical elongated element within a given distance from the spring.

[0020] As described above, for some applications, a frame is disposed around the impeller. For some applications, the ventricular assist device includes a stator including a plurality of curved protrusions coupled to the proximal end of the frame. Typically, the curvature of the curved protrusions is opposite the direction of rotation of the impeller. For some applications, the curvature of the curved protrusions is such that from the distal end of the curved protrusions to the proximal end of the curved protrusions, the curved protrusions gradually become more 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 bound an internal lumen therethrough.

[0021] As described above, typically the impeller is disposed within a tube (sometimes referred to herein as a "blood pump tube") extending from the left ventricle of the subject to the aorta of the subject. For some applications, at least one blood pressure measurement tube (the blood pressure measurement tube bounding an opening at its distal end) 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 outside 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 the 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 configured to extend to the outer surface of the blood pump tube at a location along the blood pump tube configured to be within the left ventricle of the subject proximal to the impeller, 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] Generally, the 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, the ventricular assist device comprises a radially expandable atraumatic distal tip portion configured to be disposed within the subject's left ventricle distally relative to the one or more blood inlet openings. The distal tip portion is generally configured to be inserted into the left ventricle in a radially constrained configuration and is configured to assume a non-radially constrained configuration within the subject's left ventricle, wherein at least a radially expandable portion of the distal tip portion is radially expanded relative to the radially constrained configuration of the distal tip portion. Generally, in its non-radially constrained configuration, the radially expandable portion of the distal tip portion separates the one or more blood inlet openings from internal structures of the left ventricle such as the interventricular septum, chordae tendinae, papillary muscles, and / or the apex of the left ventricle. Further, generally, in its non-radially constrained configuration, the radially expandable portion of the distal tip portion separates the one or more blood inlet openings from 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 tip 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 tip portion, a distal region of the distal tip portion is configured to be at least semi-rigid and is shaped to radially converge along the longitudinal direction towards a distal end of the distal tip portion. Generally, the ventricular assist device is configured to be inserted into the 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 tip 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 portion thereof, are to be interpreted to mean the end or portion of the device that is generally 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 portion thereof, are to be interpreted to mean the end or portion of the device that is generally further away 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 application includes the use of the devices and methods described herein in anatomical locations other than the left ventricle and the aorta. Thus, the ventricular assist device and / or portions thereof are sometimes referred to herein (in the specification and claims) as a blood pump.

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

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

[0028] An 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 and distal bearings of the frame and the proximal and distal bushings of the impeller,

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

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

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

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

[0035] In some applications, the impeller comprises:

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

[0037] A spring disposed within the helical elongated element and wound around an axis thereof along the helical elongated element;

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

[0039] at least one flexible elongated element extending from the spring to the helical elongated element and configured to hold the helical elongated element within a given distance from the spring, the at least one flexible elongated element selected from the group consisting of: a string and a wire.

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

[0041] The delivery catheter is configured to hold the impeller in its radially constrained configuration during introduction of the impeller into the body of a subject,

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

[0043] To retract the impeller from the body of a subject, the delivery catheter is configured to, by moving 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 on the axial shaft distally, causes the impeller to assume its radially constrained configuration.

[0044] According to some applications of 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 a left ventricle of a subject;

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

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

[0049] The impeller is configured to undergo axial axial back-and-forth motion relative to the frame in response to cyclic changes in pressure difference between the left ventricle and the aorta.

[0050] In some applications:

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

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

[0053] The ventricular assist device further comprises 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 is coupled to the impeller such that the at least one bushing is held in an axially fixed position relative to the axial shaft, 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 bearing configured to be disposed within the subject’s body.

[0057] In some applications, the ventricular assist device further comprises one or more thrust bearings configured to be disposed outside the subject’s body, and wherein opposition to thrust generated by rotation of the impeller is provided solely by the one or more thrust bearings disposed outside the subject’s body.

[0058] In some applications,

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

[0060] the ventricular assist device further comprises:

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

[0062] a drive cable configured to extend from outside the subject’s body to the axial shaft, the drive cable being configured to transmit rotational motion from the motor to the impeller by rotation, at least a portion of the drive cable comprising a plurality of wires disposed in a coiled configuration such that, in response to the drive cable being rotated in the given direction of rotation, the plurality of wires disposed in the coiled configuration at least partially uncoil such that the portion of the drive cable axially shortens.

[0063] In some applications, the apparatus further comprises:

[0064] a sensor configured to detect an indication of axial motion 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 a cardiac cycle of the subject in response to receiving the sensor signal. In some applications, the computer processor is configured to determine a left ventricular pressure of the subject based at least in part on the sensor signal. In some applications, the computer processor is configured to change a rotational rate of the impeller based at least in part on the sensor signal.

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

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

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

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

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

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

[0073] a sensor configured to detect a 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 a cardiac cycle of the subject in response to receiving the sensor signal. In some applications, the computer processor is configured to determine a left ventricular pressure of the subject based at least in part on the sensor signal. In some applications, the computer processor is configured to change a rotational rate of the impeller based at least in part on the sensor signal.

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

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

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

[0079] In some applications, the computer processor is configured to decrease the rate of rotation of the impeller in response to determining that 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 and distal bearings of the frame and the proximal and distal bushings 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 and distal bearings of the frame.

[0085] In some applications, the axial shaft is configured to clean an interface between the axial shaft and the proximal and distal bearings of the frame by moving axially back and forth relative to the proximal and distal bearings of the frame. In some applications, the axial shaft is configured to reduce heat buildup at an interface between the axial shaft and the proximal and distal bearings of the frame by moving axially back and forth relative to the proximal and distal bearings of the frame relative to a situation in which the axial shaft does not move axially back and forth relative to the proximal and distal bearings of the frame.

[0086] According to some applications of the invention, there is also provided a device, the device comprising:

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

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

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

[0090] An axial shaft, the axial shaft being configured to pass through the proximal and distal bearings of the frame and the proximal and distal bushings of the impeller, the axial shaft:

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

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

[0094] In some applications, the apparatus further comprises:

[0095] a sensor configured to detect an indication of axial motion 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 cardiac cycle of the subject in response to receiving the sensor signal. In some applications, the computer processor is configured to determine a left ventricular pressure of the subject based at least in part on the sensor signal. In some applications, the computer processor is configured to change a rate of rotation of the impeller based at least in part on the sensor signal.

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

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

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

[0101] In some applications, the computer processor is configured to decrease the rate of rotation of the impeller in response to determining that the left ventricular pressure of the subject has decreased.

[0102] In some applications, the apparatus further comprises:

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

[0104] a sensor configured to detect a 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 cardiac cycle of a subject in response to receiving the sensor signal. In some applications, the computer processor is configured to determine a left ventricular pressure of a subject based at least in part on the sensor signal. In some applications, the computer processor is configured to change a rotational rate of the impeller based at least in part on the sensor signal.

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

[0108] determine a left ventricular pressure of a subject based at least in part on the sensor signal, and

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

[0110] In some applications, the computer processor is configured to decrease the rotational rate of the impeller in response to determining that a left ventricular pressure of a subject 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 periodic changes in a pressure difference between the first location and the second location. In some applications, the impeller is configured to pump blood from a subject's left ventricle to the subject's aorta, and the impeller is configured to move axially back and forth relative to the frame in response to periodic changes in a pressure difference between the left ventricle and the aorta. In some applications, the impeller is configured to pump blood from a subject's right ventricle to the subject's pulmonary artery, and the impeller is configured to move axially back and forth relative to the frame in response to periodic changes in a pressure difference between the right ventricle and the pulmonary artery. In some applications, the impeller is configured to pump blood from a subject's right atrium to the subject's right ventricle, and the impeller is configured to move axially back and forth relative to the frame in response to periodic changes in a pressure difference between the right atrium and the right ventricle. In some applications, the impeller is configured to pump blood from a subject's vena cava to the subject's right ventricle, and the impeller is configured to move axially back and forth relative to the frame in response to periodic changes in a pressure difference between the vena cava and the right ventricle. In some applications, the impeller is configured to pump blood from a subject's right atrium to the subject's pulmonary artery, and the impeller is configured to move axially back and forth relative to the frame in response to periodic changes in a pressure difference between the right atrium and the pulmonary artery. In some applications, the impeller is configured to pump blood from a subject's vena cava to the subject's pulmonary artery, and the impeller is configured to move axially back and forth relative to the frame in response to periodic changes in a pressure difference between the vena cava and the pulmonary artery.

[0112] In some applications, the apparatus 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 motion from the motor to the impeller by rotation, at least a portion of the drive cable comprising a plurality of wires disposed in a coiled configuration such that, in response to the drive cable being rotated in the given rotational direction, the plurality of wires disposed in the coiled configuration at least partially uncoil such that the portion of the drive cable axially shortens.

[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 an interface between the axial shaft and the proximal bearing and the distal bearing of the frame by moving 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 reduce heat buildup at an interface between the axial shaft and the proximal bearing and the distal bearing of the frame by moving axially back and forth relative to the proximal bearing and the distal bearing of the frame relative to what would occur if the axial shaft did not move axially back and forth relative to the proximal bearing and the distal bearing of the frame.

[0116] According to some applications of the invention, there is also provided a device, the device comprising:

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

[0118] an impeller, the impeller configured to be placed within a body of a subject and configured to pump blood through the body of the subject;

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

[0120] the blood pump does not comprise any thrust bearing configured to be disposed within the body of the subject.

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

[0122] In some applications, the device further comprises:

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

[0124] a computer processor, the 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 a cardiac cycle of the subject in response to receiving the sensor signal. In some applications, the computer processor is configured to determine a left ventricular pressure of the subject based at least in part on the sensor signal. In some applications, the computer processor is configured to change a rotational rate of the impeller based at least in part on the sensor signal.

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

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

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

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

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

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

[0132] a sensor configured to detect a 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 a cardiac cycle of the subject in response to receiving the sensor signal. In some applications, the computer processor is configured to determine a left ventricular pressure of the subject based at least in part on the sensor signal. In some applications, the computer processor is configured to change a rotational rate of the impeller based at least in part on the sensor signal.

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

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

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

[0138] In some applications, the computer processor is configured to decrease the rate of rotation of the impeller in response to a determination that 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 periodic changes in a pressure difference between the first location and the second location. In some applications, the impeller is configured to pump blood from a left ventricle of the subject to an aorta of the subject, and the impeller is configured to move axially back and forth relative to the frame in response to periodic changes in a pressure difference between the left ventricle and the aorta. In some applications, the impeller is configured to pump blood from a right ventricle of the subject to a pulmonary artery of the subject, and the impeller is configured to move axially back and forth relative to the frame in response to periodic changes in a pressure difference between the right ventricle and the pulmonary artery. In some applications, the impeller is configured to pump blood from a right atrium of the subject to the right ventricle of the subject, and the impeller is configured to move axially back and forth relative to the frame in response to periodic changes in a pressure difference between the right atrium and the right ventricle. In some applications, the impeller is configured to pump blood from a vena cava of the subject to the right ventricle of the subject, and the impeller is configured to move axially back and forth relative to the frame in response to periodic changes in a 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 periodic changes in a 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 periodic changes in a 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 causing the impeller to rotate in a given direction of rotation;

[0142] an axial shaft, the impeller being coupled to the axial shaft; and

[0143] a drive cable configured to extend from outside a 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 comprising a plurality of wires disposed in a coiled configuration such that, in response to the drive cable being rotated in the given rotational direction, the plurality of wires disposed in the coiled configuration at least partially uncoil such that the portion of the drive cable axially shortens.

[0144] In some applications:

[0145] the impeller comprises a proximal bushing and a distal bushing;

[0146] the frame comprises a proximal bearing and a distal bearing;

[0147] the device further comprises an axial shaft, the axial shaft:

[0148] passes through the proximal and distal bearings defined by the frame and the proximal and distal bushings of the impeller,

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

[0150] is not held in an axially fixed position relative to the proximal and distal bearings,

[0151] such that the impeller causes the axial shaft to axially shuttle relative to the proximal and distal bearings of the frame.

[0152] In some applications, the axial shaft is configured to clean an interface between the axial shaft and the proximal and distal bearings of the frame by the axial shuttling relative to the proximal and distal bearings of the frame. In some applications, the axial shaft is configured to reduce heat buildup at an interface between the axial shaft and the proximal and distal bearings of the frame relative to a situation in which the axial shaft does not axially shuttle relative to the proximal and distal bearings of the frame by the axial shuttling.

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

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

[0155] an impeller, the impeller comprising:

[0156] at least one helical elongated element;

[0157] a spring disposed within the helical elongated element and along an axis around which the helical elongated element is wound;

[0158] a film of material supported between the helical elongated element and the spring; and

[0159] at least one flexible elongated element extending from the spring to the helical elongated element and configured to maintain the helical elongated element within a given distance from the spring, the at least one flexible elongated element selected from the group consisting of a string and a wire.

[0160] Concept 2. The apparatus of Concept 1, wherein the impeller is configured such that, in a non-radially constrained configuration of the impeller, an outer diameter of the impeller at a location where the outer diameter is at its maximum value is less than 8 mm.

[0161] Concept 3. The apparatus of Concept 1, wherein the at least one helical elongated element comprises a plurality of helical elongated elements, and wherein the at least one flexible elongated element extends from the spring to each of the helical elongated elements.

[0162] Concept 4. The apparatus of any one of Concepts 1-3, wherein the impeller is configured to pump blood through a body of a subject.

[0163] Concept 5. The apparatus of Concept 4, wherein the impeller is configured to be placed in a blood vessel of the subject.

[0164] Concept 6. The apparatus of Concept 4, wherein the impeller is configured to be placed in a heart chamber of the subject.

[0165] Concept 7. The apparatus of Concept 4, wherein the impeller is configured to pump blood from a left ventricle of the subject to an aorta of the subject.

[0166] Concept 8. The apparatus of Concept 4, wherein the impeller is configured to pump blood from a right ventricle of the subject to a pulmonary artery of the subject.

[0167] Concept 9. A method comprising:

[0168] placing an impeller into a body of a subject, the impeller comprising:

[0169] at least one helical elongated element;

[0170] a spring disposed within the helical elongated element and along an axis around which the helical elongated element is wound;

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

[0172] at least one flexible elongated element extending from the spring to the helical elongated element, selected from the group consisting of a string and a wire; and

[0173] pumping blood through the subject's body by rotating the impeller, during rotation of the impeller, the flexible elongated element maintaining the helical elongated element within a given distance from the spring.

[0174] Inventive Concept 10. An apparatus comprising:

[0175] a 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 being configured to axially move relative to the frame in response to periodic changes in a pressure difference between the heart chamber and the blood vessel.

[0180] Inventive Concept 11. A method comprising:

[0181] placing an impeller of a blood pump within a heart chamber of a subject, the impeller being disposed around a frame; 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 placing of the impeller within the heart chamber allowing the impeller to axially move relative to the frame in response to periodic changes in a pressure difference between the heart chamber and the blood vessel.

[0184] Inventive Concept 12. An apparatus comprising:

[0185] a 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 move axially relative to the frame in response to periodic changes in a pressure difference between the first blood vessel and the second blood vessel.

[0190] Inventive Concept 13. A method comprising:

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

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

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

[0194] Inventive Concept 14. An apparatus comprising:

[0195] a blood pump comprising:

[0196] an impeller configured to be placed within a body of a subject and configured to rotate so as 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 of the body of the subject, wherein opposition to thrust forces generated by rotation of the impeller is provided solely by the one or more thrust bearings disposed outside of the body of the subject.

[0199] Inventive Concept 15. A method comprising:

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

[0201] driving the impeller to pump blood through the body of the subject by rotating the impeller, opposition to thrust forces generated by rotation of the impeller being provided solely by one or more thrust bearings disposed outside of the body of the subject.

[0202] Inventive Concept 16. An 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 bounds an opening at a distal end thereof and that is configured to extend to 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 subject's blood flow outside of the blood pump tube; and

[0206] at least one pressure sensor configured to measure the subject's blood flow pressure outside of the blood pump tube by measuring a blood pressure within the blood pressure measurement tube.

[0207] Inventive Concept 17. The apparatus of Inventive Concept 16, wherein the blood pump comprises an impeller configured to pump blood through the blood pump tube by rotation.

[0208] Inventive Concept 18. The apparatus of Inventive Concept 16, wherein the blood pressure measurement tube is configured to pass along an outer surface of the blood pump tube from a 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 apparatus of 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 blood pumping by the blood pump in response to the blood pressure measured within the blood pump tube.

[0210] Inventive Concept 20. The apparatus of any of Inventive Concepts 16-19, wherein the at least one blood pressure measurement tube comprises at least one left ventricular blood pressure measurement tube configured to extend to an outer surface of the blood pump tube at a location along the tube configured to be within the subject's left ventricle proximate to the blood pump, and wherein the pressure sensor is configured to measure the subject's left ventricular pressure by measuring a blood pressure within the left ventricular blood pressure measurement tube.

[0211] Inventive Concept 21. The apparatus of Inventive Concept 20, wherein the at least one blood pressure measurement tube comprises two or more left ventricular 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 subject's left ventricle proximate to the blood pump, and wherein the at least one pressure sensor is configured to measure the subject's left ventricular pressure by measuring a blood pressure within at least one of the left ventricular blood pressure measurement tubes.

[0212] Inventive Concept 22. The apparatus of Inventive Concept 21,

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

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

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

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

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

[0218] Inventive Concept 23. The apparatus of Inventive Concept 20, wherein the at least one blood pressure measurement tube further comprises at least one aortic blood pressure measurement tube 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 subject’s aorta, and wherein the pressure sensor is configured to measure the aortic pressure of the subject by measuring blood pressure within the aortic blood pressure measurement tube.

[0219] Inventive Concept 24. The apparatus of Inventive Concept 23, wherein the 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 subject’s aorta, and wherein the at least one pressure sensor is configured to measure the aortic pressure of the subject by measuring blood pressure within the at least one aortic blood pressure measurement tube.

[0220] Inventive Concept 25. The apparatus of any of Inventive Concepts 16-19, wherein the 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 subject’s aorta, and wherein the pressure sensor is configured to measure the aortic pressure of the subject by measuring blood pressure within the aortic blood pressure measurement tube.

[0221] Inventive Concept 26. The apparatus of Inventive Concept 25, wherein the 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 subject’s aorta, and wherein the at least one pressure sensor is configured to measure the aortic pressure of the subject by measuring blood pressure within the at least one aortic blood pressure measurement tube.

[0222] Inventive Concept 27. The apparatus of Inventive Concept 26,

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

[0224] The apparatus further comprises at least one computer processor configured to:

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

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

[0227] determine, in response thereto, 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 apparatus 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 the opening at the 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 apparatus according to Inventive Concept 28, wherein the blood pump comprises an impeller disposed on an axial shaft, the impeller being configured to pump blood from the left ventricle to the aorta by rotation, wherein the apparatus further comprises:

[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 to within 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 apparatus according to Inventive Concept 29,

[0235] wherein the at least one blood pressure measurement tube comprises at least one left ventricular blood pressure measurement tube configured to extend to an outer surface of the blood pump tube at a location along the blood pump tube that is proximal to the blood pump and configured to be disposed within the outer tube, and wherein the at least one pressure sensor is configured to measure left ventricular pressure of the subject by measuring blood pressure within the left ventricular blood pressure measurement tube;

[0236] the apparatus further comprises an aortic blood pressure measurement tube that bounds an opening at a distal end thereof 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] 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.

[0238] Inventive Concept 31. The apparatus of Inventive Concept 29,

[0239] wherein the at least one blood pressure measurement tube comprises at least one left ventricular 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 left ventricle of the subject proximate to the blood pump, 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 apparatus further comprises an aortic blood pressure measurement tube defining an opening at a distal end thereof and configured to extend from outside the subject’s body to a portion of an outer surface of the 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 apparatus of Inventive Concept 29, wherein the outer tube defines a groove in the 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 the portion of the blood pressure measurement tube does not protrude from the outer surface of the outer tube.

[0243] Inventive Concept 33. The apparatus of Inventive Concept 28, wherein a 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 apparatus of Inventive Concept 33, wherein a 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 comprising:

[0246] inserting into a body of a subject:

[0247] a blood pump tube,

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

[0249] at least one blood pressure measurement tube, the blood pressure measurement tube defining an opening at a distal end thereof and extending 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 subject's blood flow outside the blood pump tube;

[0250] pumping blood through the blood pump tube using the blood pump; and

[0251] measuring the blood flow pressure of the subject outside 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, the blood pump comprising:

[0254] a tube;

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

[0256] a frame disposed about the impeller; and

[0257] a stator configured to reduce a 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 of Inventive Concept 36, wherein a curvature of the curved protrusions is opposite a direction of rotation of the impeller.

[0261] Inventive Concept 38. The apparatus of Inventive Concept 36, a curvature of the curved protrusions is such that from a distal end of the curved protrusions to a proximal end of the curved protrusions, the curved protrusions gradually become closer to parallel to a longitudinal axis of the frame.

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

[0263] Inventive Concept 40. A method, comprising:

[0264] placing a blood pump into a body of a subject, the blood pump comprising:

[0265] a tube,

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

[0267] a frame disposed about the impeller, and

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

[0269] The stator reduces a rotational flow component of the blood flow generated by the rotation of the impeller.

[0270] Inventive Concept 41. An apparatus comprising:

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

[0272] An axial shaft;

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

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

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

[0276] The first portion of the drive cable comprises a first number of wires disposed in a coiled configuration, and the second portion of the drive cable comprises 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 a 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 a 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 comprises between 4 and 8 wires disposed in a coiled configuration, and the second portion of the drive cable comprises between 8 and 12 wires disposed in a coiled configuration.

[0280] Inventive Concept 45. An apparatus comprising:

[0281] A blood pump comprising:

[0282] An axial shaft;

[0283] an impeller disposed on the axial shaft;

[0284] a motor configured to be disposed outside the subject's body and configured to drive the impeller to pump blood through the subject's body by rotating the impeller;

[0285] 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, the drive cable comprising a first portion configured to be disposed at least partially within a curved portion of the subject's vasculature, and a second portion configured to be disposed at least partially within a straight portion of the subject's vasculature,

[0286] the first portion of the drive cable comprises a first number of wires disposed in a coiled configuration, and the second portion of the drive cable comprises 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 comprising:

[0288] a blood pump comprising:

[0289] an axial shaft;

[0290] an impeller disposed on the axial shaft;

[0291] a motor configured to be disposed outside the subject's body and 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 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,

[0293] at least a portion of the drive cable comprises a plurality of wires disposed in a coiled configuration, such that in response to the drive cable being rotated in the given rotational direction, the plurality of wires disposed in the coiled configuration at least partially untwist, such that the portion of the drive cable axially shortens.

[0294] Inventive Concept 47. The apparatus of Inventive Concept 46, wherein the impeller is configured to pump blood from a first location to a second location, and wherein the impeller is configured to axially shuttle back and forth in response to periodic changes in a pressure difference between the first location and the second location.

[0295] Inventive Concept 48. A method comprising:

[0296] placing a blood pump into a subject's body, the blood pump comprising:

[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 a distal end of the impeller to a proximal end of the impeller by imparting rotational motion to the impeller via the drive cable, at least a portion of the drive cable comprising a plurality of wires disposed in a coiled configuration such that, in response to the drive cable being rotated in a given rotational direction, the plurality of wires disposed in the coiled configuration at least partially uncoil such that the portion of the drive cable axially shortens.

[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 causing the impeller to rotate 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 coupled to the axial shaft, the drive cable configured to impart rotational motion from the motor to the impeller by rotating;

[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 comprising a plurality of wires disposed in a coiled configuration such that, in response to the drive cable being rotated in a given rotational direction, the plurality of 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] the impeller is driven by imparting rotational motion to the impeller via the drive cable, at least a portion of the drive cable comprising a plurality of wires disposed in a coiled configuration such that, in response to the drive cable being rotated in a given rotational direction, the plurality of wires are configured to pump fluid toward a 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 by rotating the impeller to pump blood, the impeller configured to undergo axial motion in response to changes in a pressure differential against which the impeller pumps blood;

[0322] a magnet to which the impeller is coupled such that axial motion of the impeller causes axial motion of the magnet;

[0323] a sensor configured to detect a 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 of Inventive Concept 51, wherein the computer processor is configured to generate the output indicative of a cardiac cycle of the subject in response to receiving the sensor signal.

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

[0327] Inventive Concept 54. The apparatus of any one of Inventive Concepts 51-53, wherein the computer processor is configured to change a rotational rate of the impeller based at least in part on the sensor signal.

[0328] Inventive Concept 55. The apparatus of Inventive Concept 54, wherein the computer processor is configured to:

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

[0330] varying a rotational rate of the impeller based at least in part on the determined left ventricular pressure.

[0331] Inventive Concept 56. The apparatus of Inventive Concept 55, wherein the computer processor is configured to decrease the rotational rate of the impeller in response to determining that the left ventricular pressure of the subject has decreased.

[0332] Inventive Concept 57. An apparatus comprising:

[0333] a blood pump comprising:

[0334] an impeller;

[0335] a motor configured to drive the impeller to pump blood by rotating the impeller, the impeller configured to move axially in response to changes in a pressure differential 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 comprising:

[0339] placing a blood pump into a body of a subject, the blood pump comprising an impeller;

[0340] driving the impeller to pump blood by rotating the impeller, the impeller configured to move axially in response to changes in a pressure differential 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. An apparatus comprising:

[0344] a blood pump comprising:

[0345] an impeller;

[0346] a frame,

[0347] the impeller and the frame configured to be inserted into a body of a subject such that, within the body of the subject, the frame is disposed around the impeller; and

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

[0349] Inventive Concept 60. A method comprising:

[0350] placing a blood pump comprising 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 pump blood through the subject's body by driving the impeller to rotate; and

[0353] driving the impeller to move axially within the frame in a back-and-forth motion.

[0354] Inventive Concept 61. An apparatus comprising:

[0355] a blood pump comprising:

[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 configured to transmit rotational motion from the motor to the impeller by rotation;

[0360] a tube within which the drive cable is configured to be disposed during rotation of the drive cable, the tube 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 so as to reduce friction between the drive cable and the tube during movement of the drive cable relative to the tube.

[0362] Inventive Concept 62. The apparatus of 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 comprising:

[0365] axial shaft;

[0366] an impeller disposed on the axial shaft and configured to be placed within a body of a subject;

[0367] a motor configured to be disposed outside the body of the subject;

[0368] a drive cable configured to extend from outside the body of the subject to the axial shaft;

[0369] exactly two drive magnets disposed in 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 an axial length of the driven magnet, the motor configured to rotate the driven magnet by rotating the drive magnet housing so as to rotate the drive cable to impart rotational motion to the impeller.

[0371] Inventive Concept 64. A method comprising:

[0372] placing a blood pump into a body of a subject, 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 body of the subject to the axial shaft; and driving rotation of the impeller by:

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

[0377] the drive magnets configured to thereby drive rotation of 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 an 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 body of a subject;

[0382] a motor configured to be disposed outside of the subject’s body;

[0383] a drive cable configured to extend from outside of the subject’s body to the 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 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 an axial length of the drive magnet, the motor configured to rotate the driven magnets by rotating the drive magnet in order to rotate the drive cable to impart rotational motion to the 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 of 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 an axial length of the drive magnet,

[0392] the drive magnet configured to thereby drive the driven magnets to rotate, the driven magnets comprising exactly two driven magnets disposed in a driven magnet housing, the 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 of the subject’s body and configured to drive the impeller to pump blood by rotating the impeller in a given direction of rotation;

[0398] a drive cable configured to extend from outside the subject's body to the axial shaft, the drive cable being configured to transmit rotational motion from the motor to the impeller by rotation, and the drive cable comprising a plurality of wires disposed in a coiled configuration and coupled to the axial shaft,

[0399] the axial shaft defining a groove at an interface between the drive cable and the axial shaft, the groove being configured such that stress generated by the wires at the interface is distributed over a radius of the groove.

[0400] Inventive Concept 68. An apparatus comprising:

[0401] a blood pump comprising:

[0402] an axial shaft;

[0403] an impeller disposed on the axial shaft and configured to be placed within the 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 the subject's body to the axial shaft, the drive cable being configured to transmit rotational motion from the motor to the impeller by rotation, and the drive cable comprising a plurality of wires disposed in a coiled configuration and coupled to the axial shaft,

[0406] the coiled wires are shaped such that a pitch of the wires increases as the coiled wires approach an interface between the drive cable and the axial shaft, such that stress at a location at which the wires of the drive cable are coupled to the axial shaft is reduced relative to if the pitch of the wires did not increase.

[0407] Inventive Concept 69. An apparatus comprising:

[0408] a blood pump comprising:

[0409] an axial shaft;

[0410] an impeller disposed on the axial shaft and configured to be placed within the 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 the subject's body to the axial shaft, the drive cable being configured to transmit rotational motion from the motor to the impeller by rotation,

[0413] The drive cable comprises a first portion and a second portion, the first portion of the drive cable comprising a first number of wires arranged in a coiled configuration, and the second portion of the drive cable comprising a second number of wires arranged in a coiled configuration, the first number being lower than the second number; and

[0414] an interface component via which the first and second portions of the drive cable are coupled to each other,

[0415] the interface component defines a groove at an interface between at least one of the drive cable portions and the interface component, the groove being configured such that a stress generated by the wires at the interface is distributed over a radius of the groove.

[0416] Inventive Concept 70. An apparatus, comprising:

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

[0418] an axial shaft;

[0419] an impeller arranged on the axial shaft and configured to be placed inside a body of a subject;

[0420] a motor configured to be arranged outside the body of the subject and configured to drive the impeller to pump blood by rotating the impeller in a given direction of rotation;

[0421] a drive cable 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,

[0422] the drive cable comprises a first portion and a second portion, the first portion of the drive cable comprising a first number of wires arranged in a coiled configuration, and the second portion of the drive cable comprising a second number of wires arranged in a coiled configuration, the first number being lower than the second number; and

[0423] an interface component via which the first and second portions of the drive cable are coupled to each other,

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

[0425] Inventive Concept 71. An apparatus, comprising:

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

[0427] a tube configured to be passed through the aortic valve of the subject such that a proximal portion of the tube is disposed within the aorta of the subject and a distal portion of the tube is disposed within the left ventricle of the subject, the tube 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 the one or more blood inlet openings and out of the tube into the aorta through the one or more blood outlet openings; and

[0429] a radially expandable atraumatic distal tip portion configured to be disposed within the left ventricle of the subject distally relative to the one or more blood inlet openings, the distal tip portion 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 tip portion expands radially relative to the radially constrained configuration of the distal tip portion.

[0430] Inventive Concept 72. The apparatus of Inventive Concept 71, wherein the distal tip portion comprises a braided shape memory alloy at least partially covered with a blood- impermeable material.

[0431] Inventive Concept 73. The apparatus of Inventive Concept 71, wherein the distal tip portion is configured such that, in the non-radially constrained configuration of the distal tip portion, the radially expandable portion of the distal tip portion separates the one or more blood inlet openings from an interventricular septum within the left ventricle.

[0432] Inventive Concept 74. The apparatus of Inventive Concept 71, wherein the distal tip portion is configured such that, in the non-radially constrained configuration of the distal tip portion, the radially expandable portion of the distal tip portion separates the one or more blood inlet openings from chordae tendinae within the left ventricle.

[0433] Inventive Concept 75. The apparatus of Inventive Concept 71, wherein the distal tip portion is configured such that, in the non-radially constrained configuration of the distal tip portion, the radially expandable portion of the distal tip portion separates the one or more blood inlet openings from papillary muscles within the left ventricle.

[0434] Inventive Concept 76. The apparatus of Inventive Concept 71, wherein the distal tip portion is configured such that, in the non-radially constrained configuration of the distal tip portion, the radially expandable portion of the distal tip portion separates the one or more blood inlet openings from an apex of the left ventricle.

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

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

[0437] Inventive Concept 79. The apparatus according to any one of Inventive Concepts 71-78, wherein:

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

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

[0440] in the radially constrained configuration of the distal tip portion, the distal region of the distal tip portion is configured to be at least semi-rigid and shaped to radially converge along the longitudinal direction towards the distal end of the distal tip portion;

[0441] Inventive Concept 80. The apparatus according to any one of Inventive Concepts 71-78, wherein the distal tip portion is configured such that, in the non-radially constrained configuration of the distal tip portion, the distal end of the distal tip portion is enclosed within the radially expandable portion of the distal tip portion.

[0442] Inventive Concept 81. The apparatus according to Inventive Concept 80, wherein the distal tip portion is configured to prevent the distal end of the distal tip portion from becoming entangled with chordae tendinae of the left ventricle by the distal end of the distal tip portion being enclosed within the radially expandable portion of the distal tip.

[0443] Inventive Concept 82. The apparatus according to Inventive Concept 80, wherein the distal tip portion is configured to prevent the distal end of the distal tip portion from causing damage to internal structures of the left ventricle by the distal end of the distal tip portion being enclosed within the radially expandable portion of the distal tip portion.

[0444] Inventive Concept 83. The apparatus according to Inventive Concept 80, wherein the distal end of the distal tip portion is configured to be enclosed within the radially expandable portion of the distal tip portion by the distal end of the distal tip portion being flipped over.

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

[0446] Inventive Concept 85. An apparatus comprising:

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

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

[0450] A distal tip portion configured to:

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

[0452] have a non-radially constrained configuration in which the radially expandable portion of the distal tip portion is configured to be atraumatic and configured to separate the one or more blood inlet openings from internal structures of the left ventricle of the subject, the distal tip portion configured to assume the non-radially constrained configuration within the left ventricle of the subject.

[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 within the left ventricle of the subject;

[0457] a motor disposed outside of the body of the subject and configured to drive the impeller to rotate,

[0458] a drive cable that extends from outside the subject’s body to the axial shaft via the subject’s aortic arch and is configured to transmit rotational motion from the motor to the 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] pumping fluid into the space between the drive cable and the tube while operating the blood pump, such that the fluid fills the space between the drive cable and the tube but does not release fluid into the subject’s bloodstream.

[0461] Inventive Concept 87. A method comprising:

[0462] operating a blood pump, the blood pump comprising:

[0463] an axial shaft,

[0464] an impeller disposed on the axial shaft and disposed in the subject’s left ventricle,

[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 to the axial shaft via the subject’s aortic arch 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] pumping fluid into the space between the drive cable and the tube before operating the blood pump, such that the fluid fills the space between the drive cable and the tube but does not release fluid into the subject’s bloodstream; and

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

[0470] Inventive Concept 88. An apparatus comprising:

[0471] a left heart assist device configured to assist the subject’s left ventricle in functioning, the left heart assist device comprising:

[0472] a tube configured to pass through the subject’s aortic valve such that a proximal portion of the tube is disposed at least partially within the subject’s ascending aorta and a distal portion of the tube is disposed at least partially 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 proximal portion of the tube is thus configured to collapse inward in response to pressure outside the proximal portion of the tube exceeding pressure within the proximal portion of the tube;

[0475] a pump disposed within the frame and configured to pump blood through the tube from the left ventricle of the subject to the aorta of the subject, such that the proximal portion of the tube remains in an open state when 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 elongate commissure elements disposed within the proximal portion of the tube, such that respective portions of the circumference of the tube form cusps that contact one another when the proximal portion of the tube collapses inward.

[0477] Concept 89. The apparatus of Concept 88, further comprising a computer processor configured to control blood pumping by the blood pump through the tube such that 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] Concept 90. The apparatus of Concept 88, further comprising a pressure sensor configured to measure 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 blood pumping by the blood pump through the tube in response to the measured aortic blood pressure.

[0479] Concept 91. The apparatus of Concept 88, further comprising a pressure sensor configured to measure 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 blood pumping by the blood pump through the tube in response to the measured left ventricular blood pressure.

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

[0481] a impeller;

[0482] a frame disposed about 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 disposed in their radially constrained configuration, and are configured to assume a non-radially constrained configuration by being released from the delivery device; and

[0484] a coupling element comprising 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 configured to facilitate radial contraction of the impeller by holding an end of the impeller such that the impeller can be axially elongated without radially contracting the frame.

[0485] Inventive Concept 93. An 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 of a body of a subject and configured to drive the impeller to rotate;

[0489] a drive cable extending from outside of the body of the subject to the 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 of the body of the subject to within 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 function as a stagnation pressure tap and the second opening is configured to function as a static pressure tap;

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

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

[0494] Inventive Concept 94. A method comprising:

[0495] inserting a blood pump into a body of a subject, the blood pump comprising:

[0496] an impeller comprising a proximal bushing and a distal bushing,

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

[0498] an axial shaft that passes through the proximal and distal bearings of the frame and the proximal and distal bushings of the impeller, the proximal bushing of the impeller being coupled to the axial shaft such that the proximal bushing is held in an axially fixed position relative to the axial shaft, and the distal bushing of the impeller not being coupled to the axial shaft such that the distal bushing is not held in an axially fixed position relative to the axial shaft,

[0499] while the impeller is inserted into the subject's body, the impeller is held in a radially constrained configuration by the delivery catheter;

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

[0501] pumping blood through the subject's body using the impeller 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 a left ventricle of a subject, the impeller being disposed about a frame; and

[0504] driving the impeller to pump blood from the left ventricle of the subject to an aorta by rotating the impeller,

[0505] the placement of the impeller within the left ventricle allowing the impeller to move axially relative to the frame in response to cyclic changes in a pressure difference between the left ventricle and the aorta.

[0506] Inventive Concept 96. A method comprising:

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

[0508] an impeller having a frame disposed about the impeller, the impeller comprising a proximal bushing and a distal bushing, and the frame comprising a proximal bearing and a distal bearing, and

[0509] an axial shaft that passes through the proximal and distal bearings of the frame and the proximal and distal bushings of the impeller, the axial shaft being coupled to at least one of the proximal and distal bushings of the impeller such that the at least one bushing is held in an axially fixed position relative to the axial shaft and is not held in an axially fixed position relative to the proximal and distal bearings; and

[0510] pumping blood through the subject's body using the impeller.

[0511] Inventive Concept 97. A method comprising:

[0512] placing an impeller of a blood pump within the body of a subject, the impeller being surrounded by a frame; and

[0513] driving the impeller to pump blood through the body of the subject without using any thrust bearing disposed within the body of the subject to provide opposition to the thrust generated by the rotation of the impeller.

[0514] The present application will be more fully understood from the following detailed description of embodiments of the application, taken in conjunction with the accompanying drawings, in which: BRIEF DESCRIPTION OF DRAWINGS

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

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

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

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

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

[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 according to some applications of the present application, at various stages of the movement cycle of the impeller of the ventricular assist device relative to the frame of the ventricular assist device;

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

[0523] Figure 7is a schematic view of a motor unit of a ventricular assist device according to some applications of the present application;

[0524] Figure 8A and Figure 8B is a schematic view of a motor unit of a ventricular assist device according to some applications of the present application;

[0525] Figure 9 is a graph indicating the variation in length of the drive cable of a ventricular assist device when the pressure gradient against which the impeller of the blood pump resists varies, as measured in experiments performed by the inventors of the present application;

[0526] Figure 10A , Figure 10B and Figure 10C is a schematic view of a drive cable of a ventricular assist device according to some applications of the present application;

[0527] Figure 11A and Figure 11B is a schematic view of an interface component according to some applications of the present application, which forms an interface between respective portions of the drive cable of a ventricular assist device;

[0528] Figure 11C , Figure 11D and Figure 11E is a schematic view of an interface between the drive cable and the axial shaft of a ventricular assist device according to some applications of the present application;

[0529] Figure 12 is a schematic view of a drive cable of a ventricular assist device according to some applications of the present application, which comprises a friction-reducing element arranged around at least a portion of the drive cable;

[0530] Figure 13 is a schematic view of a procedure for purifying the drive cable and / or the radial bearing of a ventricular assist device according to some applications of the present application;

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

[0532] Figure 15A is a schematic view of the flat profile of a frame of a ventricular assist device according to some applications of the present application;

[0533] Figure 15B is a schematic view showing a magnified view of the proximal end of a frame of a ventricular assist device according to some applications of the present application;

[0534] Figure 15Cis a schematic view of a frame of a ventricular assist device according to some applications of the present application, to which a material defining a curved protrusion is coupled;

[0535] Figure 16A , Figure 16B , Figure 16C and Figure 16D are schematic views of a ventricular assist device according to some applications of the present application comprising one or more blood pressure measurement tubes;

[0536] Figure 17A , Figure 17B and Figure 17C are schematic views of a ventricular assist device according to some applications of the present application comprising a pitot tube configured to measure blood flow through a tube of the device;

[0537] Figure 18 is a schematic view of a ventricular assist device according to some applications of the present application, the distal end portion of the device being a radially expandable atraumatic distal end portion;

[0538] Figure 19A and Figure 19B are schematic views of a ventricular assist device according to some applications of the present application, the distal end portion of the device being a radially expandable atraumatic distal end portion;

[0539] Figure 20A and Figure 20B are schematic views of a ventricular assist device according to some applications of the present application, the distal end portion of the device being a radially expandable atraumatic distal end portion;

[0540] Figure 21A , Figure 21B , Figure 21C and Figure 21D are schematic views of a distal end portion of a ventricular assist device according to some applications of the present application;

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

[0542] Figure 23A and Figure 23B are schematic views of a distal end portion of a ventricular assist device according to some applications of the present application, respectively in a radially constrained configuration and in a non-radially constrained configuration;

[0543] Figure 24A and Figure 24B are schematic views of a distal end portion of a ventricular assist device according to some applications of the present application, respectively in a radially constrained configuration and in a non-radially constrained configuration;

[0544] Figure 25A is a schematic view of first and second portions 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 extraction 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 malfunction of an 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 sac to prevent backflow of blood, e.g., in the event of a malfunction of an impeller of the ventricular assist device. DETAILED DESCRIPTION

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

[0550] As shown in Figure 1B , Figure 1BSteps of deployment of a ventricular assist device in the left ventricle are shown, typically the distal end of the ventricular assist device is guided to the left ventricle on a guidewire 10. During insertion of the distal end of the device into the left ventricle, a delivery catheter 143 is disposed over the distal end of the device. Once the distal end of the device is disposed in the left ventricle, the delivery catheter is typically retracted to the aorta, and the guidewire is withdrawn from the subject's body. The retraction of the delivery catheter typically 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. Typically, the ventricular assist device is inserted into the subject's body in order to provide acute treatment to the subject. For some applications, in order to withdraw the left ventricular device from the subject's body at the end of the treatment, the delivery catheter is advanced over the distal end of the device, which causes the self-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 with reference to Figure 2A , Figure 2B and Figure 2C , Figure 2A , Figure 2B and Figure 2C are schematic illustrations of a blood pump portion 27 of a ventricular assist device 20 in accordance with some applications of the present application; typically, an impeller 50 is disposed within a distal portion 102 of a tube 24, and is configured to pump blood from the left ventricle into the aorta by rotation. The tube typically bounds one or more blood inlet openings 108 at a distal end of the tube, via which blood flows from the left ventricle into the tube during operation of the impeller. For some applications, a proximal portion of the tube bounds one or more blood outlet openings 109, via which blood flows from the tube into the ascending aorta during operation of the impeller.

[0552] For some applications, a console 21 (which typically includes a computer processor 25 (shown in Figure 1A ) drives rotation of the impeller. For example, the computer processor can control a motor 74 (shown in Figure 7 ) disposed within a motor unit 23, and the motor 74 via a drive cable 130 (also shown in Figure 7The 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 functions as a special purpose ventricular assist computer processor.

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

[0554] Typically, along the distal portion 102 of the tube 24, a frame 34 is disposed within the tube. The frame is typically made of a shape memory alloy, such as Nitinol. For some applications, the shape memory alloy of the frame is set such that the frame (and thereby the tube) assumes a generally circular, elliptical, or polygonal cross-sectional shape in the absence of any force applied to the tube. By assuming its generally circular, elliptical, or polygonal cross-sectional shape, the frame is configured to hold the distal portion of the tube in an open state. Typically, during operation of the ventricular assist device, the distal portion of the tube is configured to be placed within the body of a 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 cannula is at least partially positioned within the native aortic valve, and the frame is configured to maintain aortic valve opening by exhibiting its generally circular, elliptical, or polygonal cross-sectional shape. For some applications, the cannula 24 is sized to prevent the shape memory alloy of the frame 34 from fully conforming to the dimensions shaped by the shape memory alloy. In this way, the frame is "pre-tensioned" so that even if the aortic valve applies radial compressive forces to the cannula and frame, the frame does not become radially compressed because the frame is held in a partially radially constrained state by the cannula. For some applications, the frame includes a plurality of rigid struts 111 arranged 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 arranged) maintains a generally straight longitudinal axis, even when subjected to anatomical forces within the left ventricle and / or the aortic valve. Typically, the rigid strut is configured such that the length of the rigid strut does not change even if the frame 34 is changed from a radially constrained configuration (in which the frame is typically set during the introduction of the frame into the subject's body) to a non-radially constrained configuration (in which the frame is typically set during the operation of the ventricular assist device).

[0556] For some applications, no frame is provided within the proximal portion 106 of tube 24, and therefore the tube is not supported by frame 34 in the open position. Tube 24 is typically made of a collapsible material that is impermeable to blood. For example, tube 24 may include polyurethane, polyester, and / or silicone. Typically, the proximal portion of the tube is configured such that it is at least partially disposed within the ascending aorta of the subject. For some applications, the proximal portion of the tube passes through the aortic valve of the subject, entering the ascending aorta from the left ventricle of the subject, such as... Figure 1B As shown in the diagram. As described above, the tube typically defines one or more blood inlet openings 108 at its distal end, through which blood flows from the left ventricle into the tube during impeller operation. 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 impeller operation. Typically, the tube defines multiple blood outlet openings 109, for example, between two and eight blood outlet openings (e.g., between two and four blood outlet openings). During impeller operation, the blood flow pressure through the tube typically keeps the proximal portion of the tube open. For some applications, in the event of, for example, impeller failure, the proximal portion of the tube is configured to collapse inward in response to external pressure exceeding internal pressure. In this way, the proximal portion of the tube acts as a safety valve, thereby preventing retrograde blood flow from the aorta into the left ventricle.

[0557] For some applications, the computer processor 25 of the console 21 (shown in FIG. 1) Figure 1A is configured to control pumping of the blood pump (e.g., by controlling rotation of the impeller) such that blood pressure generated by the pump within the tube 24 exceeds the subject's aortic systolic pressure during systole, but is lower than the subject's aortic diastolic pressure 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 subject's aortic pressure, left ventricular pressure, and / or flow through the tube 24, e.g., using techniques described below with reference to Figure 9 , Figures 16A-16D and / or Figures 17A-17C For some such applications, based on the measured aortic pressure, left ventricular pressure, and / or flow, the computer processor controls rotation of the impeller in the manner described above. Alternatively, based on the measured aortic pressure, left ventricular pressure, and / or flow, the computer processor controls rotation of the impeller in a manner different from the manner described above. For example, the computer processor can be configured to vary the rate of rotation of the impeller based on the measured aortic pressure, left ventricular pressure, and / or flow, but in a manner such that the impeller pumps blood from the left ventricle to the aorta in a non-pulsatile, continuous manner.

[0558] Generally, pumping blood through the impeller increases aortic pressure and decreases left ventricular pressure. Once the flow through tube 24 reaches a critical value above which aortic pressure is higher than left ventricular pressure even during ventricular systole (hereinafter "systole"), the aortic valve remains closed around the exterior of tube 24 throughout the cardiac cycle, and flow from the ventricle to the aorta occurs only via the tube. Generally, above this point at which aortic pressure decouples from ventricular pressure, the left ventricle no longer performs net external work (defined as volume change times pressure change) because it does not move any volume. In this mode, the left ventricle's oxygen consumption depends on the circulating pressure generated by the closed aortic valve resisting, the wall tension resulting from the size of the left ventricle, the wall thickness, and the baseline metabolic demand (including calcium circulation). Below this critical point of impeller activity, the aortic valve generally opens at least partially during systole, and left ventricular outflow will occur both between the exterior of the tube and the aortic valve (by virtue of left ventricular contraction) and through the tube (by virtue of impeller rotation and pumping). For a given number of impeller revolutions per minute, the larger the cross-sectional area of the sleeve, the greater the flow 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 around the exterior of the tube as it pumps.

[0559] Thus, generally, there is a trade-off between the efficiency of the impeller in assisting the left ventricle (which advantageously increases with tube diameter) and the remaining outflow resistance around the exterior of tube 24 (which disadvantageously increases with tube diameter). The higher the flow through the tube provided by the impeller (for a given tube diameter), the less the impact of the reduced cross-sectional outflow area on the effective outflow resistance can be, because the remaining cross-sectional area can be suitable for the remaining small stroke volume that the ventricle must eject, i.e., the reduced remaining outflow tract area can not cause undue resistance to outflow. Conversely, however, once a fixed tube diameter is chosen, the effective resistance to outflow increases as the flow through the tube decreases, because a greater proportion of the left ventricular stroke volume now needs to pass through the remaining outflow tract area around the tube. Thus, for some applications, the left ventricular outflow resistance is configured to automatically adjust in order to compensate for changes in blood flow through the tube generated by the impeller. For example, the tube can be made of a compliant material whose compliance causes a reduction in flow through the tube and a subsequent drop in distending pressure to result in a reduction in the sleeve diameter, thereby increasing the outflow area available to the left ventricle. Generally, the material properties of the compliant material are defined such that (a) the maximum tube distension is reached just at (or close to) the instant at which the lumen pressure of the tube generated by the pumping flow exceeds aortic pressure (independent of the instant in the cardiac cycle), and thus remains above left ventricular pressure throughout the cardiac cycle, and (b) complete collapse of the tube is reached when the flow through the tube generated by the impeller becomes zero.

[0560] Referring now to Figure 2B For some applications, a plurality of elongated coaptation 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 coaptation 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, with respective portions of the circumference of the tube forming cusps that contact one another when the tube is closed. For some applications, the ventricular assist device includes three elongated coaptation 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 An embodiment is depicted, however one of the coaptation elements is hidden from view. For some applications (not shown), the ventricular assist device includes two elongated coaptation 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 placed so as to pass through the subject's aortic valve, and the coaptation elements are rotationally aligned with the commissures of the native valve. In this manner, the artificial cusps of the proximal portion of the tube are aligned with the native aortic valve leaflets.

[0561] Referring to Figures 2A-2C For some applications, the frame 34 is shaped so that the frame defines a proximal conical portion 36, a central cylindrical portion 38, and a distal conical portion 40. Typically, the proximal conical portion is such that the narrow end of the cone is proximal with respect to the wide end of the cone. Additionally, typically, the distal conical portion is such that the narrow end of the cone is distal with respect to the wide end of the cone. For some applications, the tube 24 extends to the end of the cylindrical portion 38, so that the distal end of the tube defines a single axially-facing blood inlet opening 108, as shown in Figure 2A and Figure 2B For some applications, 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 typically defines two to four lateral blood inlet openings.

[0562] Typically, the tube 24 includes a conical proximal portion 42 and a central cylindrical portion 44. Typically, the proximal conical portion is such that the narrow end of the cone is proximal with respect 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 typically defines a distal conical portion 46, where the narrow end of the cone is distal with respect to the wide end of the cone, as shown in Figure 2CThe diameter of the tube 24 varies along the length of the central portion of the tube for some applications (not shown) 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, the central portion of the tube has a diameter between 5 mm and 7 mm at its proximal end, and a diameter between 8 mm and 12 mm at its distal end.

[0563] Reference is now made to Figures 3A-3C , Figures 3A-3C is a schematic illustration of an impeller 50 according to some applications of the present application. Typically, the impeller includes at least one outer helical elongated element 52 wrapped around a central axial spring 54 such that a helix defined by the helical elongated element is coaxial with the central axial spring. Typically, the impeller includes two or more helical elongated elements (e.g., three helical elongated elements, as shown in Figures 3A-3C For some applications, the helical elongated elements and the central axial spring are made of a shape memory material, e.g., a shape memory alloy such as Nitinol. Typically, each of the helical elongated elements and the central axial spring is supported by a film 56 of material (e.g., a polymer such as polyurethane and / or silicone) therebetween. For illustrative purposes, the impeller is shown without the material in Figure 3A . Figure 3B and Figure 3C respectively show views of the impeller with the material supported between the helical elongated elements and the spring.

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

[0565] Generally, the proximal ends of the springs 54 and the helical elongated elements 52 extend from a proximal bushing (i.e., sleeve bearing) 64 of the impeller, such that the proximal ends of the springs 54 and the helical elongated elements 52 are disposed at similar radial distances from the longitudinal axis of the impeller. Similarly, generally, the distal ends of the springs 54 and the helical elongated elements 52 extend from a distal bushing 58 of the impeller, such that the distal ends of the springs 54 and the helical elongated elements 52 are disposed at similar radial distances from the longitudinal axis of the impeller. Generally, the springs 54, as well as the proximal and distal bushings 64, 58 of the impeller, define an internal lumen 62 therethrough.

[0566] Reference is now made to Figure 4 , Figure 4 is a schematic view of an impeller 50 disposed within a frame 34 of a ventricular assist device 20, in accordance with some applications of the present application. As shown, generally, there is a gap G between the outer edges of the impeller 50 and the inner surface of the frame 34, even at locations where the span of the impeller is at its maximum. For some applications, it is desirable that the gap between the outer edges 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 edges of the blades of the impeller and the inner surface of the frame 34, for example, so as to reduce the risk of hemolysis.

[0567] For some applications, the gap G between the outer edges 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), for example, 0.05 mm-1 mm, or 0.1 mm-0.4 mm, at locations where the span of the impeller is at its maximum. For some applications, the outer diameter of the impeller is greater than 6 mm (e.g., greater than 6.5 mm), and / or less than 8 mm (e.g., less than 7 mm), for example, 6 mm-8 mm, or 6.5 mm-7 mm, at locations where the outer diameter of the impeller is at its maximum. 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), for example, 6.5 mm-8.5 mm, or 7 mm-7.5 mm.

[0568] Generally, the axial shaft 92 passes through the axis of the impeller 50 through the inner cavity 62 of the impeller. Generally, a 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 a distal bushing 58 of the impeller is slidable relative to the shaft. The axial shaft itself is radially stabilized via proximal and distal radial bearings 116, 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 even a relatively small gap (e.g., a gap as described above) between the outer edges of the blades of the impeller and the inner surface of the frame 34 is maintained during rotation of the impeller.

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

[0570] For some applications, the elongate elements 67 hold the helical elongate element (which defines the outer edge of the impeller blades) within a given distance relative to the central axial spring. In this way, the elongate elements are configured to prevent the outer edge of the impeller from being pushed radially outward due to forces exerted on the impeller during rotation of the impeller. The elongate elements are thereby configured to maintain a gap between the outer edge of the blades of the impeller and the inner surface of the frame 34 during rotation of the impeller. Generally, 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, each of which is generally doubled (i.e., extending radially from the central axial spring 54 to the outer helical elongate element 52 and then back to the central axial spring from the helical elongate element). For some applications, the plurality of elongate elements are formed from a single piece of string or single wire, each of the plurality of elongate elements extending from the spring to a respective 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 elongated element 52 are cut from a tube of a shape memory material such as Nitinol. The cutting of the tube and the shape setting of the shape memory material is typically performed such that the helical elongated element is defined by the shape memory material, e.g., using techniques generally similar to those described in US 2016 / 0022890 to Schwammenthal. Typically, the spring 54 is inserted into the cut and shape set tube such that the spring extends along the length of the tube from at least the proximal bushing to the distal bushing. For some applications, the spring is inserted into the cut and shape set tube while the spring is in an axially compressed state, and the spring is configured to be held in place relative to the tube by exerting a radial force on the proximal and distal bushings. Alternatively or additionally, portions of the spring are welded to the proximal and distal bushings. For some applications, the spring is cut from a tube of a shape memory material such as Nitinol. For some such applications, the spring is configured such that when the spring is disposed in a non-radially constrained configuration (the spring is typically disposed in this configuration during operation of the impeller), there is substantially no gap between a convolution of the spring and a convolution adjacent to that convolution.

[0572] For some applications, at this stage, the elongated element 67 as described above is placed such that it extends between the spring and one or more helical elongated elements (e.g., in the following manner). A mandrel (e.g., a polyether ether ketone (PEEK) and / or a polytetrafluoroethylene (PTFE) mandrel) is inserted through the lumen defined by the spring and the bushings. A string or thread is then threaded such that it (a) goes from the mandrel to the first helical elongated element, (b) goes from the first helical elongated element back to the mandrel, (c) goes around the mandrel and to the second helical elongated element, (d) goes from the second helical elongated element back to the mandrel, and so on. Once the string or thread has been threaded from the mandrel to each of the helical elongated elements and back again, the ends of the string or thread are coupled to one another, e.g., by tying them to one another. For some applications, a suture 53 (e.g., a polyester suture) is wrapped around the helical elongated elements in order to facilitate bonding between a membrane of a material (typically a polymer such as polyurethane or silicone) and the helical elongated elements (typically a shape memory alloy such as Nitinol) in a subsequent stage of impeller manufacturing. For some applications, a suture (e.g., a polyester suture, not shown) is wrapped around the spring 54. Typically, the suture is configured to facilitate bonding between a membrane of a material (typically a polymer such as polyurethane or silicone) and the spring (typically a shape memory alloy such as Nitinol) in a subsequent stage of impeller manufacturing.

[0573] Typically, at this stage, as Figure 3AAs shown in FIG. 59, the structure 59 has been assembled. The structure includes a cut and shaped tube that bounds proximal and distal bushings and helical long elements, springs, and optionally long elements and sutures. The structure is immersed in a material that bounds a membrane 56. For some applications, the assembled structure is immersed in the material with a mandrel disposed through the inner lumen bounded by the springs and bushings, although note that the mandrel is not shown in Figure 3A As shown in FIG. 59, the structure 59 has been assembled. The structure includes a cut and shaped tube that bounds proximal and distal bushings and helical long elements, springs, and optionally long elements and sutures. The structure is immersed in a material that bounds a membrane 56. For some applications, the assembled structure is immersed in the material with a mandrel disposed through the inner lumen bounded by the springs and bushings, although note that the mandrel is not shown in

[0574] The result of the process described above is generally that there is a continuous membrane of material that extends between each helical long element to the spring and also along the length of the spring so as to bound a tube with the spring embedded within the tube. The portions of the membrane that extend from each helical long element to the spring bound impeller blades. For applications in which the impeller includes long elements 67, the long elements are generally embedded in these portions of the membrane.

[0575] Generally, the impeller 50 is inserted into the left ventricle transcatheterally with the impeller 50 in a radially constrained configuration. In the radially constrained configuration, the helical long elements 52 and the central axial spring 54 both become axially elongated and are radially constrained. Generally, the membrane 56 of material (e.g., silicone) changes shape to conform to the shape change of the helical long elements and the axial support spring, both of which support the membrane of material. Generally, the use of a spring to support the inner edge of the membrane allows the membrane to change shape without becoming torn or collapsed because the spring provides a large surface area to which the inner edge of the membrane is bonded. For some applications, the use of 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, the proximal bushing 64 of the impeller 50 is coupled to the axial shaft 92 such that the axial position of the proximal bushing relative to the shaft is fixed and the distal bushing 58 of the impeller is slidable relative to the shaft. For some applications, when the impeller is radially constrained for the purpose of inserting the impeller into a ventricle or for the purpose of withdrawing the impeller from a subject’s body, the impeller is axially elongated by the distal bushing sliding axially distally along the axial shaft.

[0577] As described above, for some applications, the proximal bushing 64 of the impeller 50 is coupled to the axial shaft 92 such that the axial position of the proximal bushing relative to the shaft is fixed and the distal bushing 58 of the impeller is slidable relative to the shaft. For some applications, when the impeller is radially constrained for the purpose of inserting the impeller into a ventricle or for the purpose of withdrawing the impeller from a subject’s body, the impeller is axially elongated by the distal bushing sliding axially distally along the axial shaft. Figures 3A-3CAs shown in FIG. 1, after being released into the body of a subject, the impeller assumes its non-radially constrained configuration (in which the impeller is normally disposed during operation of the impeller). Typically, when the impeller 50 is in the non-radially constrained configuration (e.g., within a chamber of a subject), the pitch of each helical elongated 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 else being equal, the greater the pitch of the helical elongated elements (and thus the impeller blades), the greater the blood flow generated by the impeller. Thus, as described, when the impeller 50 is in the non-radially constrained configuration, the pitch of the helical elongated elements 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 regurgitation of blood into the left ventricle of a subject. Generally, all else being equal, the smaller the pitch of the helical elongated elements (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 elongated elements 52 is typically less than 20 mm (e.g., less than 10 mm).

[0578] For some applications, the pitch of the helical elongated elements (and thus the impeller blades) varies along the length of the helical elongated elements, at least when the impeller is in the non-radially constrained configuration. 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 a subject and 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, blood flow velocity increases along the impeller, in the direction of blood flow. Thus, the pitch is increased in the direction of blood flow in order to further accelerate blood.

[0579] Note that, for illustrative purposes, 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 FIGS. 1-3. For example, some of the figures show impellers that do not include sutures 53 and / or elongated elements 67. The scope of the present application includes the use of impellers having any of the features shown and described with reference to FIGS. 1-3 in combination with any of the devices and methods described herein. Figures 3A-3C Figures 3A-3C

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

[0581] Reference is also made to Figure 5C , Figure 5C shows a typical bearing assembly used in prior art axial impeller based blood pumps. Shown is Figure 5C for purposes of serving as a reference point for some applications of the present invention described herein. As shown in Figure 5C , 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 radial motion of the impeller by maintaining the impeller's axis at a given radial position. In response to the impeller pumping blood in a first direction, the forces acting on the impeller typically push the impeller to move in a direction opposite to the first direction. The purpose of the thrust bearing is to counteract this motion of the impeller and maintain the axial position of the impeller. In the example shown in Figure 5C , in response to the impeller pumping blood in the direction of the arrow 204, the impeller is pushed in the direction of the arrow 206, and the thrust bearing counteracts this motion. Typically, the bearings experience a significant amount of heating and wear due to the frictional forces exerted on them. The thrust bearing typically experiences a significant amount of heating and wear due to the fact that the frictional forces exerted on the thrust bearing are typically spread over opposing surfaces that have a smaller contact area between these surfaces compared to the case of the radial bearing.

[0582] As described above, the generally axial shaft 92 passes through the axis of the impeller 50 through the inner cavity 62 of the impeller. Generally, the proximal bushing 64 of the impeller is coupled to the shaft via the coupling element 65 such that the proximal bushing is fixed in 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 the proximal radial bearing 116 and the 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 even a relatively small gap (e.g., the gap as described above) between the outer edges of the blades of the impeller and the inner surface of the frame 34 is maintained during rotation of the impeller, 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 frame are collapsed (i.e., radially constrained) for the purpose of inserting the impeller and frame into the body of a subject, the distal bushing 58 of the impeller is configured to slide along the axial shaft in the distal direction such that the impeller becomes axially elongated, as described above. More generally, by the distal bushing sliding on 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 bearing or thrust bearing. Rather, the bearings 116 and 118 act as radial bearings with respect to the axial shaft. For some applications, there are no thrust bearings in contact with any surface to potentially generate thrust during rotation of the impeller, as the impeller is configured to move axially within the frame 34 while the impeller is rotating, as described in further detail below. Generally, the pump portion 27 (and more generally the ventricular assist device 20) does not include any thrust bearing configured to be disposed within the body of a subject and configured to counteract the thrust generated by rotation of the impeller. For some applications, one or more thrust bearings are disposed outside of the body of the subject (e.g., within the motor unit 23 shown in FIGS. 1-3), and the force to counteract the thrust generated by rotation of the impeller is provided solely by the one or more thrust bearings disposed outside of the body of the subject. For some applications, mechanical elements and / or magnetic elements are configured to hold the impeller within a given range of axial positions. For example, a magnet disposed at the proximal end of the drive cable (e.g., magnet 82, described below with reference to FIG. 4) can be configured to transmit axial motion to the impeller and configured to hold the impeller within a given range of axial positions. Figure 1A 、 Figure 7 and Figures 8A-8B For some applications, the impeller is configured to be axially constrained within the frame 34. For example, the impeller can be configured to be axially constrained within the frame 34 when the impeller is in its radially constrained configuration. For some applications, the impeller is configured to be axially constrained within the frame 34 when the impeller is in its non-radially constrained configuration. For some applications, the impeller is configured to be axially constrained within the frame 34 when the impeller is in both its radially constrained configuration and its non-radially constrained configuration. For some applications, the impeller is configured to be axially constrained within the frame 34 when the impeller is in any of its configurations. For some applications, the impeller is configured to be axially constrained within the frame 34 when the impeller is in any of its configurations and when the impeller is in any of its configurations. Figure 7

[0584] ​For some alternative applications of the application, the ventricular assist device includes an impeller that is not configured to move in an axial back-and-forth motion. For some such applications (not shown), a thrust bearing is used to maintain the axial position of the impeller, and the thrust bearing is disposed within a portion of the ventricular assist device proximal to the impeller such that the thrust bearing does not come into contact with the subject's blood. For example, the thrust bearing can be disposed within an outer tube in which a drive shaft of the impeller is disposed. Alternatively or additionally, the thrust bearing can be disposed external to the subject's body. For some such applications, because 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 the two opposing surfaces of the thrust bearing is typically greater than 20 square millimeters. For some applications (not shown), the thrust bearing is disposed distal to the impeller and in contact with the subject's blood such that the thrust bearing is cooled by the subject's blood.

[0585] Reference is now made to Figure 6A and Figure 6B , Figure 6A and Figure 6B are schematic illustrations of the ventricular assist device 20 at various stages of the motion cycle of the impeller 50 of the ventricular assist device relative to the frame 34 of the ventricular assist device, in accordance with some applications of the present application. For some applications, while the impeller is pumping blood through the tube 24 by rotating, the axial shaft 92 to which the impeller is fixed is driven to move the impeller back and forth axially within the frame 34 by moving the axial shaft in an axial back-and-forth motion, as described in further detail below, for example, with reference to Figure 7 Alternatively or additionally, the impeller and the axial shaft are configured to move back and forth axially 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 axial back-and-forth motion, as described in further detail below, for example, with reference to Figure 9 .

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

[0587] For some applications, the length of the frame 34 exceeds the length of the impeller 50 by at least 2 mm (e.g., at least 4 mm, or at least 8 mm) when the frame 34 and the impeller 50 are in their non-radially constrained configuration (e.g., when the frame and impeller are deployed inside the left ventricle). Typically, the proximal bearing 116 and the distal bearing 118 are each 2-4 mm in length. Further, typically, the impeller and the axial shaft are configured to move axially within the frame in a back-and-forth manner along at least the length of each of the proximal bearing and the distal bearing, 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 further referring to Figure 6C , Figure 6C is a schematic view of an axial shaft receiving tube 126 and a distal tip portion 120 of a ventricular assist device 20 according to some applications of the present application. For some applications, the distal tip portion of the ventricular assist device is configured to be soft, such that the distal tip portion is configured not to harm the subject’s tissue, even if the distal tip portion comes into contact with the tissue (e.g., the tissue of the left ventricle). For example, the distal tip portion can be made of silicone. For some applications, the distal tip portion bounds an inner lumen 122 therethrough. For some such applications, during insertion of the ventricular assist device into the left ventricle, a guide wire 10 (shown in Figure 1B ) is first inserted into the left ventricle, e.g., according to known techniques. The ventricular assist device is then guided to the left ventricle by advancing the distal tip portion over the guide wire, with the guide wire disposed within the inner lumen 122. For some applications, a hemostatic valve 152 is disposed at the distal end of the inner lumen 122 of the distal tip portion 120, such that the distal tip portion becomes sealed after the guide wire is retracted from the inner lumen 122. Typically, during insertion of the ventricular assist device into the subject’s ventricle, a delivery catheter 143 is placed over the impeller 50 and the frame 34 and holds the impeller and frame in their radially constrained configuration. For some applications, the distal tip portion 120 extends distally from the delivery catheter during insertion of the delivery catheter into the subject’s ventricle. For some applications, at a proximal end of the distal tip portion, the distal tip portion has a flared portion 124 that acts as a barrier and prevents the delivery catheter from advancing beyond the flared portion.

[0589] For some applications, the axial shaft receives tube 126 extends proximally from the distal tip portion 120. As described above, generally during operation of the impeller 50, the axial shaft undergoes axial back-and-forth motion. The axial shaft receiving tube 126 defines an inner lumen 127 configured to receive the axial shaft when the axial shaft extends beyond the distal bearing 118. For some applications, the axial shaft receiving tube defines a stopper 128 at its distal end configured to prevent the axial shaft from advancing beyond the stopper. For some applications, the stopper comprises a rigid member inserted (e.g., embedded) into the distal end of the axial shaft receiving tube. Alternatively, the stopper comprises a shoulder between the inner lumen 127 of the axial shaft receiving tube and the inner lumen 122 of the tip portion 120. Generally, such a shoulder exists because the inner lumen 122 of the tip portion 120 is narrower than the inner lumen 127 (because the inner lumen 127 is generally configured to accommodate the axial shaft, while the inner lumen 122 is configured to accommodate the guide wire 10, and the axial shaft is generally wider than the guide wire 10 because the axial shaft itself is configured to accommodate the guide wire 10 within an inner lumen 132 of the axial shaft (as shown in Figure 10B and Figure 10C ). Generally, during normal operation of the impeller, the axial shaft does not extend to the stopper 128 even when the drive cable 130 (shown in Figure 7 ) is maximally elongated. However, the stopper 128 is configured to prevent the axial shaft from extending into the tip portion during retraction of the ventricular assist device 20 from the subject's ventricle when the delivery catheter is advanced over the impeller 50 and the frame 34. In some cases, during advancement of the delivery catheter over the frame and the impeller, the drive cable is at risk of breaking. Without the stopper 128, the axial shaft can extend into the tip portion in such cases. The stopper 128 prevents this from happening even in the event of a broken drive cable.

[0590] Generally, during operation of the ventricular assist device, and throughout the back-and-forth axial motion of the impeller, the impeller is disposed relatively close to the distal tip portion. For example, throughout the back-and-forth axial motion of the impeller, the impeller can be within 50% of the most distal portion of the tube 24, e.g., within 30% of the most distal portion (or within 20% of the most distal portion) of the most distal portion.

[0591] For some applications (not shown), a portion of the frame 34 extends into a proximal portion of the distal tip portion 120. The portion of the frame is configured to cause the proximal portion of the tip to radially expand when deployed within the subject's left ventricle by configuring the portion of the frame into a radially expanded configuration. For some applications, the entire tip portion is made of a material having a uniform stiffness, but the portion of the frame 34 that extends into the proximal portion of the tip portion imparts stiffness to the proximal portion of the tip portion such that the proximal portion of the tip portion has a greater stiffness than the distal portion of the tip portion. For some applications, the tip portion has a different configuration than that shown in

[0592] FIG. 1, as described in further detail below, e.g., with reference to Figure 6C For some applications, the distal tip portion will incorporate certain features described with reference to Figures 18-24B For some applications, the distal tip portion will incorporate certain features described with reference to Figure 6C For some applications, the distal tip portion will incorporate certain features described with reference to Figure 13 For some applications, the distal tip portion will incorporate certain features described with reference to Figures 18-24B For some applications, the distal tip portion will incorporate certain features described with reference to Figures 6A-6C For some applications, the internal structure of the tip portion and the axial shaft’s extension from the proximal extension of the tip portion can be as described with reference to Figure 13 For some applications, the internal structure of the tip portion and the axial shaft’s extension from the proximal extension of the tip portion can be as described with reference to Figures 18-24B For some applications, the external shape of the tip portion can be as described with reference to any one of For some applications, the external shape of the tip portion can be as described with reference to any one of

[0593] For some applications, the external shape of the tip portion can be as described with reference to any one of Figure 7 For some applications, the external shape of the tip portion can be as described with reference to any one of Figure 7 For some applications, the external shape of the tip portion can be as described with reference to any one of Figure 1A For some applications, the external shape of the tip portion can be as described with reference to any one of For some applications, the external shape of the tip portion can be as described with reference to any one of

[0594] For some applications, the external shape of the tip portion can be as described with reference to any one of For some applications, the external shape of the tip portion can be as described with reference to any one of

[0595] For some applications, the external shape of the tip portion can be as described with reference to any one of Figure 7 For some applications, the external shape of the tip portion can be as described with reference to any one of Figure 7 For some applications, the external shape of the tip portion can be as described with reference to any one of​​​​​​​​​​​​​​​​As shown in FIG. 6, a set of drive magnets 77 are 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 axial overlap between the drive magnets and the driven magnet, and the driven magnet 82 is coupled to the proximal end of the 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 magnets include north and south poles, as shown, the north and south poles are separated from each other along the length of the cylinder along a line 83 that bisects the cylinder. For some applications, the driven magnet is housed within a cylindrical housing 87.

[0596] Magnetic coupling is strongest when the field density is greatest. Thus, it is desirable to use relatively strong magnets for the drive magnets and the driven magnet, to have a small air gap between the drive magnets and the driven magnet, and to try to minimize field line leakage. Typically, the drive magnets and the driven magnet are relatively strong neodymium magnets. Further, typically, the gap between each of the drive magnets and the driven magnet is less than 2 mm, for example, 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 stabilization of the driven magnet. As described above, the driven magnet is cylindrical, and the magnet includes a north pole and a south pole that are separated from one another along a split line 83 along the length of the cylinder. In the region of the circumference of the driven magnet that is closest to the split line between the north and south poles of the magnet, the 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 outer magnet, through the outer 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 that is at least less than the sum of the air gap between the driven and drive magnets will pass from the north pole of the driven magnet to the south pole of the driven magnet, rather than taking the alternative route. Assuming that this adds up to all of the field lines that extend around 2 mm of the circumference of the driven magnet on either side of the split line between the north and south poles of the driven magnet (i.e., a total of 4 mm of the total circumference of the driven magnet), it does not contribute to the magnetic coupling between the drive and driven magnets. If instead of exactly two magnetic poles, the driven magnet has four magnetic poles, and correspondingly four drive magnets, then there will be four times 2 mm of wasted circumference around the entire circumference, which will result in a total of 8 mm of the 12 mm of circumference of the inner magnets having wasted field lines. Some of this loss will be compensated for by the addition of two additional drive magnets, which increases the magnetic field strength. However, the additional outer magnets will be relatively close to one another, which will result in magnetic field leakage between the drive magnets. In view of the above, generally, the motor unit includes fewer than 4 magnets (e.g., exactly two magnets as shown) as drive magnets, and the driven magnet is split into fewer than 4 magnetic poles (e.g., exactly two magnetic poles as shown).

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

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

[0600] Reference is now made to Figure 8A and Figure 8B , Figure 8A and Figure 8B are schematic illustrations of motor units 23 according to some applications of the present application. Generally, the motor units 23 shown in Figure 8A and Figure 8B are similar to the motor unit shown in Figure 7 and, unless otherwise described, the motor units 23 shown in Figure 8A and 8B include similar components to the motor unit 23 shown in Figure 7 For some applications, the motor unit includes a heat sink 90 configured to dissipate heat generated by the motor. Alternatively or additionally, the motor unit includes vents 93 configured to facilitate dissipation of heat generated by the motor. For some applications, the motor unit includes dampers 94 and 96 configured to dampen vibrations of the motor unit caused by rotational and / or axial back-and-forth motion of components of the ventricular assist device.

[0601] For some applications, the impeller 50 and the axial shaft 92 are configured to move back and forth axially 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 axial back-and-forth manner. Generally, during a cardiac cycle of a subject, the pressure difference between the left ventricle and the aorta varies from approximately zero during ventricular contraction (hereinafter "contraction") to a relatively large pressure difference (e.g., 60 mmHg-100 mmHg) during ventricular relaxation (hereinafter "relaxation"). For some applications, due to the increase in the pressure difference against which the impeller pumps during relaxation, the impeller is pushed distally relative to the frame 34 during relaxation relative to its position during contraction. In turn, because the impeller is connected to the axial shaft, the axial shaft moves forward. During contraction, the impeller (and in turn the axial shaft) moves back to their contraction positions. In this manner, the axial back-and-forth motion of the impeller and the axial shaft is generated in a passive manner, i.e., without the need to actively drive the axial shaft and the impeller in order to cause them to move in this manner.

[0602] Reference is now made to Figure 9 , Figure 9 This is a graph indicating the change in the length of the drive cable of the ventricular assist device as the impeller resists a change in pressure gradient, as measured in experiments performed by the inventors of this application. The impeller and drive cable, as described herein, are used to pump a glycerol-based solution through a chamber configured to replicate the left ventricle and aorta, and the solution has properties similar to blood (such as density and viscosity). The change in pressure gradient resisted by the impeller pumping is due to the increase in the volume of fluid contained within the chamber (in which the impeller is pumping). Simultaneously, the movement of the drive cable is imaged, and changes in the length of the drive cable are determined via machine vision analysis of the images. Figure 9 The graph shown indicates the variation in the length of the drive cable as measured by the pressure gradient. Figure 9 The y-axis of the graph shown is as follows: 0 mm elongation represents the length of the drive cable when the impeller is stationary. Note that the graph begins at a pressure gradient of 65 mmHg, and at this pressure, the elongation is negative (at approximately -0.25 mm), meaning the drive cable is shortened relative to its length before the impeller begins to rotate. This is because the drive cable is configured such that when the impeller first begins pumping, the drive cable is shortened (relative to its length before the impeller is activated) due to the unwinding of the coils within the drive cable, as described in further detail below. Figure 9 As seen in the portion of the curve shown, after the initial shortening of the drive cable caused by the aforementioned effects, the drive cable then gradually elongates as the pressure gradient increases.

[0603] As by Figure 9 As indicated by the results shown and as described above, typically, in response to changes in pressure resisted by the impeller pumping 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 stretch more or less.

[0604] For some applications, during the operation of the ventricular assist device, console 21 ( Figure 1A The computer processor 25 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 subject's cardiac cycle, determines the subject's left ventricular pressure, and / or determines the subject's cardiac afterload. For some applications, the computer processor controls the rotation of the impeller and / or the axial reciprocating motion of the axial shaft in response.

[0605] For some applications, substantially similar techniques are applied to a right ventricular assist device configured to pump blood from the right ventricle to the pulmonary artery, and the computer processor is configured to determine the pressure difference between the right ventricle and the pulmonary artery with the necessary modifications in substantially similar fashion. For some applications, substantially similar techniques are applied to a heart assist device 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 the computer processor is configured to determine the pressure difference between the first location and the second location with the necessary modifications in substantially similar fashion.

[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 changes in the magnetic field generated by one of the magnets in order to measure the axial motion of the drive cable 130, and in turn determine the pressure against which the impeller is pumping. For example, the inner driven magnet 82 can be axially longer than the outer drive magnet 77. Since the inner magnet is longer than the outer magnet, the magnetic field lines emanating from the inner magnet do not pass to the outer magnet, and the magnetic flux generated by these field lines (as measured by the Hall sensor) changes with axial movement of the drive cable, and in turn axial movement of the inner magnet. During operation, the motor 74 rotates, producing an AC signal in the Hall sensor that typically has a frequency between 200 Hz and 800 Hz. Typically, when the tension in the drive cable changes due to the cardiac cycle of the subject, this produces a low frequency envelope in the signal measured by the Hall sensor, which typically has a frequency of 0.5 Hz - 2 Hz. For some applications, the computer processor measures the low frequency envelope and derives the cardiac cycle of the subject from the measured envelope. It should be noted that typically the axial motion of the magnets is substantially less than the axial motion of the impeller, since the entire range of motion of the impeller is not transmitted along the length of the drive cable. However, it is typically the case that the back and forth axial motion of the impeller produces a measurable back and forth motion of the magnets.

[0607] For some applications, the Hall sensor measurements are initially calibrated such that the change in magnetic flux per unit pressure change (i.e., per unit change in the pressure difference between the left ventricle and the aorta) resisted by the impeller pump is known. It is known that, in most subjects, the left ventricular pressure equals the aortic pressure during systole. Therefore, for some applications, the subject's aortic pressure is measured, and then the subject's left ventricular pressure at a given time is calculated by a computer processor based on: (a) the measured aortic pressure, and (b) the difference between the magnetic flux measured by the 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 for reference Figure 10A , Figure 10B and Figure 10C ,Should Figure 10A , Figure 10B and Figure 10C This is a schematic diagram of the drive cable 130 of a ventricular assist device 20 according to some applications of the present invention. Typically, as described above, the rotational motion of the impeller (transmitted via an axial shaft) and the axial reciprocating motion of the axial shaft, as described above, are transmitted to the axial shaft via the drive cable. Typically, the drive cable extends from the motor unit 23 (which is usually disposed outside the subject's body) to the proximal end of the axial shaft 92 (e.g., Figure 10C As shown in the diagram, it illustrates the connection between the distal end of the drive cable and the proximal end of the axial shaft. For some applications, the drive cable comprises multiple wires 134 arranged in a tightly coiled configuration to provide sufficient strength and flexibility for a portion of the cable to remain within the aortic arch (corresponding to...). Figure 10A (See arrow 145 in the diagram), while the cable rotates and moves in an axial reciprocating motion. The drive cable is typically housed within a first outer tube 140, which is configured to remain stationary while the drive cable rotates and / or reciprocates axially. The first outer tube is configured to effectively act as a bearing along the length of the drive cable. Typically, the first outer tube is made of a polymer (such as polyetheretherketone) configured to be highly fatigue-resistant even under frictional forces generated by the relative motion 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 usually used in the first outer tube. For some applications, the first outer tube is housed within a second outer tube 142, which is made of a material with greater flexibility than the material of the first outer tube (e.g., nylon and / or polyether block amide), and the thickness of the second outer tube is greater than that of the first outer tube.

[0609] Generally, during insertion of the impeller and cage into the left ventricle, the impeller 50 and frame 34 are held in a radially constrained configuration by the delivery catheter 143. As described above, to cause the impeller and frame to assume the non-radially constrained configuration, the delivery catheter is retracted. For some applications, such as Figure 10A As shown in FIG. 1 1, 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, causing the impeller and frame to assume their radially constrained configuration. The catheter is then withdrawn from the subject's body.

[0610] Referring to FIG. 1 1, Figure 10C Generally, the axial shaft and cable define a continuous lumen 132 therethrough. For some applications, the left ventricular device is guided to the aorta and to the left ventricle by placing the axial shaft and cable over 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 cable in this manner, it is not necessary to provide an additional guidewire guide for use during insertion of the left ventricular assist device 20. For some applications, the axial shaft and cable each have an outer diameter that is 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 lumen 132 defined by the shaft and cable has a diameter that 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 that is greater than 1 m (e.g., greater than 1.1 m) and / or less than 1.4 m (e.g., less than 1.3 m), 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 tip portion 120. Generally, the lumen 122 has a diameter that is approximately similar to the diameter of the lumen 132.

[0611] Referring to FIG. 1 1, Figure 10BFor some applications, the drive cable 130 is composed of a plurality of coiled wires 134. Typically, the impeller is pushed distally relative to the frame 34 with respect to its position during systole, as described above, due to the fact that the impeller must pump against a pressure gradient during diastole relative to its position during systole. When the rotation of the impeller begins, if the direction of rotation of the impeller is such that rotation of the drive cable in that direction causes the coiled wires of the drive cable to at least partially untwist, this will also cause the impeller to be advanced relative to the frame, due to the fact that the coiled wires untwist (i.e., become wrapped such that the radius of the coils decreases) and thereby axially lengthen. 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) rotation of the drive cable in that direction causes the coiled wires of the drive cable to at least partially untwist along the portion of the drive cable, such that the portion of the drive cable axially shortens. By configuring the drive cable in the manner described above, the length of the frame 34 need not accommodate distal movement of the impeller within the frame due to axial lengthening of the drive cable, in addition to accommodating distal movement of the impeller within the frame due to pressure changes resulting from the subject's cardiac cycle, as described above. For some applications, the extent to which the drive cable can untwist, and thereby axially shorten, is limited by an outer tube in which the drive cable is disposed, thereby preventing the drive cable from expanding radially. Thus, for some applications, the drive cable axially shortens by a relatively small amount. For some applications, the drive cable does not shorten, due to the fact that the outer tube limits the extent to which the drive cable can untwist, and thereby limits the extent to which it can axially shorten. However, even in such applications, the drive cable is typically configured not to lengthen, due to the fact that the windings of the coils are configured as described above.

[0612] Alternatively 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 exerts a tension on the drive cable that causes the drive cable to be axially lengthened relative to its resting 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 lengthen, because the drive cable is already in an axially lengthened state relative to its resting state. For some such applications, the impeller is still configured to axially move back and forth due to pressure changes resulting from the subject's cardiac cycle, as described above.

[0613] For some applications, debris is generated by the frictional forces between the drive cable and the outer tube 140. Alternatively or additionally, a fluid (e.g., a purging fluid) is disposed between the drive cable and the outer tube. Typically, due to the windings of the coiled drive cable, the drive cable acts as an impeller and pumps debris and / or fluid axially relative to the outer tube 140 due to the windings of the coiled drive cable. 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 direction of rotation, and not to pump debris and / or fluid toward the distal end of the ventricular assist device toward the left ventricle of the patient.

[0614] Reference is now made to Figure 11A and Figure 11B , which Figure 11A and Figure 11B are schematic illustrations of interface components 154 according to some applications of the present application, which interface between respective 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. Reference is also made again to Figure 10A , typically, 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 typically configured to extend up to the motor unit 23, outside the subject’s body. Typically, at locations where the drive cable 130 undergoes significant bending, such as at the aortic arch, it is desirable that the drive cable be relatively flexible. However, drive cables having greater flexibility are also typically more axially stretchable than drive cables having lesser flexibility. Thus, for some applications, there is a tradeoff between desiring the drive cable to be flexible enough to conform to the curvature of the aortic arch, but on the other hand, not desiring the drive cable to undergo significant axial stretching, which can result in loss of control over the axial position of the impeller. For some applications, the respective portions of the drive cable have respective degrees of flexibility. For example, the first portion of the drive cable, which is configured to be disposed in the aortic arch, can have a first flexibility, while the second portion of the drive cable, which is configured to be disposed in the descending aorta, can have a second flexibility, the first flexibility being greater than the second flexibility.

[0615] For some applications, the coils of wire 134 in the first portion include fewer wires than in the second portion, the first portion being configured to have greater flexibility than the second portion. For example, as Figures 11A-11BAs shown in FIG. 1 1, the first portion can 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 portion can include more than 8 wires and less than 12 wires (e.g., 8-12 wires, or 9-1 1 wires, e.g., 10 wires). For some applications, the length of the first portion of the drive cable is greater than 20 cm (e.g., greater than 25 cm) and less than 40 cm (e.g., less than 35 cm), e.g., 20-40 cm, or 25-35 cm. For some applications, the length of the second portion of the drive cable is greater than 60 cm (e.g., greater than 70 cm) and less than 100 cm (e.g., less than 90 cm), e.g., 60-100 cm, or 70-90 cm.

[0616] For some applications, the two portions of the drive cable are coupled to one another via an interface component 154. Typically, the wires of the two portions are welded to the interface component. For some applications, a groove 157 is cut into the interface component. The groove is configured so that the stress generated by the wires at the interface is distributed over the radius of the groove, rather than being concentrated at the point where the wires are welded to the interface component. For some such applications, the interface component additionally includes a protrusion 158 that holds the wires in place during welding of the wires to the interface component.

[0617] Reference is now made to Figure 11C , Figure 11D and Figure 11E , Figure 11C , Figure 11D and Figure 11E are schematic illustrations of an interface 156 between a drive cable of a ventricular assist device and an axial shaft 92, in accordance with some applications of the present application. For some applications, the drive cable is coupled to the axial shaft using techniques generally similar to those described with reference to Figures 11A-11B For some applications, the proximal end of the axial shaft (which defines the interface 156) includes a groove 157 and / or a protrusion 158, which are generally as described above, and are illustrated in Figure 11C

[0618] With reference to Figure 11D For some applications, as the coiled wire approaches the interface 156, the coiled wire is at least partially straightened (i.e., the pitch of the wire is increased), so that the angle that the wire makes with the interface is not as sharp as it would be 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. Reference is made to Figure 11E ​For some applications, in addition to being straightened, the wire is flattened and pushed radially inward as the wire approaches the interface 156. For some applications, the wire is flattened enough that each wire in the coil is in contact with an adjacent wire so as to form a cylinder, as shown. For example, the shape of the wire can change from a circular cross-section with a radius of about 0.2 mm to an elliptical cross-section with a minor axis of 0.12 mm. For some applications, the flattening is performed along a length of between 1 mm and 3 mm. For some applications, the wire is flattened by placing an overtube 159 around the wire, placing the overtube and wire on a mandrel, and radially inwardly extruding the overtube and wire. Subsequently, the overtube and flattened wire are welded to the axial shaft 92 at the interface.

[0619] For some applications, techniques generally similar to those described with reference to Figure 11D and Figure 11E are used to couple the two portions of the drive cable to one another. For some applications, as the coiled wire approaches the interface component 154, the coiled wire is at least partially straightened (i.e., the pitch of the wire is increased) so that the angle that the wire makes with the interface is not as sharp as it would be 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. For some applications, in addition to being straightened, the wire is flattened and pushed radially inward as the wire approaches the interface component 154. For some applications, the wire is flattened enough that each wire in the coil is in contact with an adjacent wire so as to form a cylinder. For example, the shape of the wire can change from a circular cross-section with a radius of about 0.2 mm to an elliptical cross-section with a minor axis of 0.12 mm. For some applications, the flattening is performed along a length of between 1 mm and 3 mm. For some applications, the wire is flattened by placing an overtube (not shown, but similar to the overtube 159) around the wire, placing the overtube and wire on a mandrel, and radially inwardly extruding the overtube and wire. Subsequently, the overtube and flattened wire are welded to the interface component 154.

[0620] For some applications, a swaging technique is used to couple the two portions of the drive cable to one another. For some such applications, the ends of the inner and outer tubes are placed inside and outside, respectively, of the ends of the two portions of the drive cable that will form the interface between the portions. The inner tube is then placed on a rigid mandrel and the inner and outer tubes and the ends of the drive cable are swaged together by applying pressure around the outside of the outer tube. Once the ends of the portions of the drive cable and the inner and outer tubes have been swaged together, this forms the interface 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 interface 156.

[0621] Reference is now made to Figure 12 , Figure 12 is a schematic view of a drive cable 130 of a ventricular assist device 20 according to some applications of the present application, the drive cable 130 including a friction reducing element 170 disposed about at least a portion of the drive cable. For some applications, the friction reducing element 170 is used to reduce friction between the drive cable 130 (which rotates during operation of the ventricular assist device) and the outer tube 142 (which remains stationary during rotation of the drive cable). In the example shown, the friction reducing element 170 is a ball bearing. However, the scope of the present application includes the use of other friction reducing elements to reduce friction between the drive cable and the outer tube. For example, other rolling element bearings can be used, such as cylindrical rollers, spherical rollers, gear bearings, tapered rollers, needle rollers, and / or toroidal roller bearings. For some applications, the friction reducing element is used as an alternative to including a first outer tube 140 in addition to the second outer tube 142. In the example shown in Figure 12 , the friction reducing 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] In general, the ventricular assist device passes through the aortic arch of the subject and / or other generally curved portions of the vasculature of the subject. Without the friction reducing element, the drive cable 130 and the tube 142 would generally contact each other, particularly at curved portions of the vasculature. As described above, the drive cable 130 generally undergoes rotational motion relative to the tube 142, and for some applications, also undergoes back-and-forth axial motion relative to the tube 142. Thus, without the friction reducing element (or the first outer tube 140, as described above), a substantial amount of friction would be generated at locations where the drive cable and the outer tube 142 contact each other. Thus, for some applications, the friction reducing element is disposed between the drive cable 130 and the outer tube 142 in order to reduce the friction generated at locations where the drive cable 130 and the outer tube 142 contact each other. For some applications, the friction reducing element is disposed between the drive cable 130 and the outer tube 142 substantially along the entire length of the drive cable 130 and the outer tube 142. Alternatively, the friction reducing 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 during operation of the ventricular assist device, e.g., at locations where the drive cable 130 and the outer tube 142 are disposed within the aortic arch.

[0623] Reference is now made to Figure 13 , Figure 13is a schematic illustration of a procedure for purifying the drive cable 130 of a ventricular assist device 20 in accordance with some applications of the present application. For some applications, proximal to 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. Typically, both the first outer tube and the second outer tube remain stationary during rotation of the drive cable. 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 in the first outer tube proximal to the proximal bearing. As described above, typically, the purifying system 29 (shown in Figure 1A ) controls the flow of the purifying fluid via the inlet 86 and the outlet 88 (shown in Figure 7 , Figure 8A and Figure 8B ). 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 arrows 148 in Figure 13 . In this way, the interface 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 interface between the axial shaft and the proximal bearing 116, purifying that interface, as indicated by the purifying fluid flow arrows 149 in Figure 13 .

[0624] For some applications, the purifying fluid is pumped through the inner lumen 132 bounded by the drive cable 130 and the axial shaft 92, so 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 interface between the axial shaft and the distal bearing 118, purifying that interface, as indicated by the purifying fluid flow arrows 150 in Figure 13 .

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

[0626] For some applications, the above-described alternative techniques are used for introducing a fluid (e.g., a fluid containing glucose) to a ventricular assist device. In Figure 13For some applications, a substantially similar technique is performed, but fluid is pumped between the drive cable 130 (which rotates) and the outer tube 140 (which remains stationary during rotation of the drive cable) during operation of the ventricular assist device. For example, as shown, fluid can be pumped into the space via a gap between the first outer tube 140 and the second outer tube 142. For some applications, fluid is continuously pumped between the drive cable and the outer tube during operation of the ventricular assist device, or fluid is periodically pumped between the drive cable and the outer tube during operation of the ventricular assist device. Note that even for such applications, fluid is pumped between the drive cable and the outer tube, but does not flow into the subject’s bloodstream because flow of fluid in the distal direction is blocked, as described above. Pumping of the fluid is configured to remove air from the space between the drive cable and the outer tube, to reduce friction between the drive cable 130 (which rotates) and the outer tube 140 (which remains stationary during rotation of the drive cable), and / or to remove debris generated by the ventricular assist device from the interface between the drive cable and the outer tube.

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

[0628] Reference is now made to Figure 14A and Figure 14B , Figure 14A and Figure 14Bis a schematic view of a frame 34 of a ventricular assist device 20 according to some applications of the present application, a stator 182 being 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. Typically, the stator includes a plurality of curved protrusions 66 (e.g., more than 2 and / or less than 8 curved protrusions 66) that 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). Typically, 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 virtue of using curved protrusions (e.g., curved such that they are 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 prior to the blood flowing out of the proximal end of the frame of the ventricular assist device.

[0629] As described above, typically, the device 20 is inserted into the ventricle of the subject via a catheter, while the frame 34 is in a radially constrained state. Upon release from the catheter, the frame automatically assumes its non-constrained shape due to self-expansion of the frame 34. Typically, 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 contain curved protrusions. Upon expansion of the frame 34, the curved protrusions are configured to automatically assume their curved configuration due to the curved protrusions being coupled to the frame 34.

[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 typically coupled to curved struts 186 of the frame 34, the curvature of the curved struts thereby defining the curvature of the curved protrusions. Typically, the flexible material is coupled to the frame 34 such that the flexible material bounds a lumen 188 therethrough (see FIG. 6B) that is aligned with the longitudinal axis of the frame. Figure 14B The axial shaft 92 of the ventricular assist device typically enters the proximal end of the frame via the lumen 188.

[0631] For some applications, to facilitate coupling of the flexible material to the frame, to shape the flexible material into a desired shape, and / or to facilitate formation of the lumen 188, a plurality of elongate elements 190 (e.g., strings and / or wires, which are typically made of a similar material as the elongate elements 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 coupled 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 respective 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 formation of the stator, a mandrel can be placed through the proximal bearing 116, and the elongate elements can be tied to the loops 192 and caused to loop around the mandrel so as to define the pattern of elongate elements shown in FIG. 18. The proximal end of the frame with the elongate elements and the mandrel is then dipped into 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 letting it 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 so as to define the lumen 188. For some applications, sutures 189 are tied around the curved struts 186 so as to facilitate coupling between the material and the struts, e.g., as described above with reference to the sutures 53 of the impeller 50. Figure 14B The pattern of elongate elements shown in FIG. 18. The proximal end of the frame with the elongate elements and the mandrel is then dipped into 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 letting it 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 so as to define the lumen 188. For some applications, sutures 189 are tied around the curved struts 186 so as to facilitate coupling between the material and the struts, e.g., as described above with reference to the sutures 53 of the impeller 50.

[0632] Reference is now made to Figure 15A , Figure 15A is a schematic illustration of a flat profile of a frame 34 of a ventricular assist device 20 according to some applications of the present application. As shown, the frame includes curved struts 186 at their proximal ends, with a loop 192 disposed towards the end of each strut. Reference is also made to Figure 15B , Figure 15B is a schematic illustration showing a magnified view of the proximal end of the frame 34 according to some applications of the present application. Once the flexible material is coupled to the curved struts, the end 194 of the curved strut 186 typically defines the orientation of the leading edge of the corresponding blade (i.e., curved protrusion) of the stator. Reference is also made to Figure 15C , Figure 15C is a schematic illustration of a frame 34 according to some applications of the present application, showing the frame with the material defining the curved protrusions 66 coupled to the frame. It can be observed that the orientation of the leading edge of the curved protrusions is defined by the orientation of the corresponding end of the curved struts.

[0633] As Figure 15BAs shown, 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, indicated by arrow 196, and parallel to the longitudinal axis of the frame, and toward the proximal end of the frame. Figure 15C As indicated in the diagram, the leading edge of the corresponding curved protrusion, relative to the approximate direction of blood flow, is typically defined at 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 protrusion 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), for example, 45 degrees–85 degrees, or 60 degrees–80 degrees.

[0634] The impeller rotates in the direction of... Figure 15C Arrow 198 indicates this. (As shown in...) Figure 15C As can be observed, the curvature of the curved protrusion typically results in a direction opposite to the rotation of the impeller (which is the direction of rotation of the swirling component of the blood flow, as imparted by the impeller to the blood flow). From its distal end to its proximal end, the curved protrusion bends to become increasingly parallel to the longitudinal axis of the frame. The curvature of the curved protrusion reduces the swirling component of the blood flow before it flows out from the proximal end of the frame of the ventricular assist device.

[0635] Now for reference Figure 16A , Figure 16B , Figure 16C and Figure 16D , Figure 16A , Figure 16B , Figure 16C and Figure 16D This is a schematic diagram of a ventricular assist device 20 according to some applications of the present invention, the ventricular assist device including one or more blood pressure measuring tubes 210. As described above, typically, the ventricular assist device includes a tube 24 that passes through the aortic valve of a subject, such that the proximal end of the tube is disposed within the subject's aorta, and the distal end of the tube is disposed within the subject's left ventricle. Typically, a blood pump, typically including an impeller 50, is disposed within the tube 24, within the subject's left ventricle, and is configured to pump blood from the left ventricle into the subject's aorta through the tube 24. For some applications, the blood pressure measuring tubes 210 are configured to extend at least to the outer surface 212 of the tube 24, such that an opening 214 at the distal end of the blood pressure measuring tube is in direct fluid communication with the patient's blood flow outside the tube 24. Pressure sensor 216 (in Figure 1AThe pressure sensor measures blood pressure within the blood pressure measurement tube (see, e.g., FIG. 2). Typically, by measuring blood pressure within the blood pressure measurement tube, the pressure sensor thereby measures blood pressure of the subject outside of the tube 24. Typically, the blood pressure measurement tube 210 extends from outside of the subject’s body to the opening 214 at the distal end of the tube, and the pressure sensor 216 is disposed toward the proximal end of the tube, e.g., outside of the subject’s body. For some applications, the computer processor 25 Figure 1A receives an indication of the measured blood pressure and controls pumping of blood through the impeller in response to the measured blood pressure.

[0636] Referring to Figure 16A and Figure 16B For some applications, the one or more blood pressure measurement tubes include one or more left ventricular blood pressure measurement tubes 220 configured to extend to an outer surface of the blood pump tube 24 at a location along the tube configured to be within the subject’s left ventricle proximate to the blood pump, e.g., proximate to the impeller 50. For such applications, the pressure sensor is configured to measure left ventricular pressure of the subject by measuring blood pressure within 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, e.g., as illustrated in Figure 16A and Figure 16B For some applications, based on blood pressure measured within each of the left ventricular blood pressure measurement tubes, the computer processor 25 determines whether the opening of one of the two or more left ventricular blood pressure measurement tubes is occluded. This can occur, e.g., due to contact of the opening with a wall of the interventricular septum and / or a portion within a different ventricle. Typically, in response to determining that the opening of one of the two or more left ventricular blood pressure measurement tubes is occluded, the computer processor determines left ventricular pressure of the subject based on blood pressure measured within a different one of the two or more left ventricular blood pressure measurement tubes.

[0637] For some applications, the one or more blood pressure measurement tubes include one or more aortic blood pressure measurement tubes 222 configured to extend to an outer surface of the tube at a location along the tube configured to be within the subject’s aorta, as illustrated in Figure 16C For such applications, the pressure sensor is configured to determine aortic pressure of the subject by measuring blood pressure within the aortic blood pressure measurement tube. For some applications, the ventricular assist device includes two or more such aortic blood pressure measurement tubes, e.g., as illustrated in Figure 16CAs shown in the diagram. For some applications, based on the blood pressure measured in each aortic blood pressure measuring tube, the computer processor 25 determines whether the opening of one of the two or more aortic blood pressure measuring tubes is blocked. This can happen, 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 measuring tubes is blocked, the computer processor determines the subject's aortic pressure based on the blood pressure measured in a different aortic blood pressure measuring tube among the two or more aortic blood pressure measuring tubes.

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

[0639] Still referencing Figure 16C As described above, for some applications, the drive cable 130 extends from a motor outside the subject's body to an axial shaft 92 on which the impeller 50 is disposed. Typically, the drive cable is disposed within an outer tube 142. For some applications, the drive cable is disposed within a first outer tube 140 and a second outer tube 142, as described above. For some applications, one or more blood pressure measuring tubes are disposed within the outer tube 142, surrounding the drive cable. For some applications, as shown, portions of one or more blood pressure measuring tubes are defined by the wall of the outer tube 142. For some applications, within the outer tube 142, the blood pressure measuring tubes have an elliptical cross-section (as shown). Typically, this increases the cross-sectional area of ​​the tube compared to if the tube had a circular cross-section. Typically, the tube has a circular cross-section in the distal portion (which extends to the opening 214) of each of the blood pressure measuring tubes. 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] like Figure 16A As shown, for some applications, at least one aortic blood pressure measuring tube 222 is used to measure aortic blood pressure, the aortic blood pressure measuring tube 222 defining an opening 219 at the distal end of the outer tube 142. The aortic blood pressure measuring tube is configured to extend from the outside of the subject's body to the outer surface of the outer tube 142 within the subject's aorta, such that the opening at the distal end of the aortic blood pressure measuring tube is in direct fluid communication with the subject's aortic blood flow. Note that for such applications, the aortic blood pressure measuring tube does not extend to the outer surface of the tube 24. The blood pressure sensor 216 is configured to measure the subject's aortic blood pressure by measuring the blood pressure within the aortic blood pressure measuring tube. For some applications, the opening 219 in the outer tube 142 is located within the tube 24, such as... Figure 16DAortic pressure is measured via opening 219, as the pressure within tube 24 at a location downstream of the impeller is generally equal to the aortic pressure.

[0641] As Figure 16A and Figure 16B For some applications, outer tube 142 defines a recess 215 in a portion of the outer surface of the outer tube that is configured to be disposed within tube 24, as shown in FIGS. 1 1 A and 1 1 B. Generally, during insertion of the ventricular assist device into the body of a subject, the portion of blood pressure measurement tube 210 that extends from within tube 24 to at least the outer surface of tube 24 is configured to be disposed within the recess, such that the portion of the blood pressure measurement tube does not protrude from the outer surface of the outer tube.

[0642] Referring now to Figure 16D For some applications, a distal portion of blood pressure measurement tube 210 is disposed on the exterior of tube 24. For example, as shown, blood pressure measurement tube 210 can extend from outer tube 142 to the proximal end of tube 24, and thereafter the blood pressure measurement tube can be built into the outer surface of tube 24. For some applications, one or more tubes extend along the outer surface of tube 24 in the manner shown in FIGS. 1 1 A and 1 1 B, but these tubes extend all the way to the distal end of tube 24, to the terminal portion 120 of the ventricular assist device. The tubes are used to inflate the inflatable portion of the terminal portion, as described in further detail below with reference to Figure 16D Figure 21C For some applications, a distal portion of blood pressure measurement tube 210 is disposed on the exterior of tube 24. For example, as shown, blood pressure measurement tube 210 can extend from outer tube 142 to the proximal end of tube 24, and thereafter the blood pressure measurement tube can be built into the outer surface of tube 24. For some applications, one or more tubes extend along the outer surface of tube 24 in the manner shown in FIGS. 1 1 A and 1 1 B, but these tubes extend all the way to the distal end of tube 24, to the terminal portion 120 of the ventricular assist device. The tubes are used to inflate the inflatable portion of the terminal portion, as described in further detail below with reference to

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

[0644] ​Generally, the scope of the present application includes applying any of the devices and methods described herein to a right ventricular assist device, with necessary modifications. A right ventricular assist device generally has a configuration that is substantially similar to the configurations described herein, and is used to pump blood from the right ventricle to the pulmonary artery, with tube 24 passing through the pulmonary semilunar valve. For some applications, components of device 20 can be adapted for use with different types of blood pumps. For example, aspects of the present application can be applicable to pumps used to pump blood from the vena cava and / or right atrium into the right ventricle, from the vena cava and / or right atrium into the pulmonary artery, and / or from the renal vein into the vena cava. Such aspects can include features of pump portion 27, impeller 50, drive cable 130, devices and methods for measuring blood pressure, devices and methods for measuring flow, etc.

[0645] For some applications, techniques substantially similar to those described with reference to blood pressure measurement tube 210 are performed using a wire that extends from within blood pump tube 24 (and generally from outside of the subject's body) to the outer surface of tube 24, such that at least the distal end of the wire is in electrical communication with the subject's blood flow outside of tube 24. Subject blood pressure outside of tube 24 (e.g., subject ventricular blood pressure and / or subject aortic blood pressure) is measured by detecting an electrical parameter using the portion of the wire that is in electrical communication with the subject's blood flow outside of tube 24.

[0646] Reference is now made to Figure 17A , Figure 17B and Figure 17C , Figure 17A , Figure 17B and Figure 17C are schematic views of an outer tube 142 of a ventricular assist device 20 according to some applications of the present application, the outer tube including a pitot tube 225 configured to measure blood flow through tube 24 of the device. Figures 17A-17C The portion of outer tube 142 shown in FIG. 6 is generally disposed within tube 24. For some applications, a flow obstruction 226 (which is generally funnel-shaped) is configured to create a stagnation region near a stagnation pressure measurement port 227. For some applications, as shown in FIG. 7, a flow straightener 228 is added to the outer surface of tube 142 in order to remove any swirling component of the flow that does not contribute to the axial flow rate. Alternatively, as shown in FIG. 8, a flow straightener 229 is added to the outer surface of tube 142 in order to remove any swirling component of the flow that does not contribute to the axial flow rate. Figure 17A Figure 17B ​As shown in FIG. 2, the stagnation pressure tap is positioned sufficiently close within the funnel-shaped flow obstruction 226 so that the flow obstruction itself acts to remove the vortex component of the flow before the blood reaches the stagnation pressure tap. For some applications, the stagnation pressure tap includes a short tube 233 that extends from the outer tube 142 within the funnel-shaped flow obstruction 226 so that the opening of the short tube 233 faces the direction of the axial blood flow through the tube 24. The outer tube 142 additionally defines an opening 219 that is generally as described above and that is used as a static pressure tap 229. The pressure within the stagnation pressure tap 227 and within the static pressure tap 229 is measured using pressure sensors, for example, as described above with reference to FIG. 1. Figures 16A-16D a pressure sensor disposed outside of the subject's body.

[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 impeller speed and the geometry of the pressure taps 227 and 229,

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

[0653] △P is the difference between the stagnation pressure (measured via the pressure tap 227) and the static pressure (measured via the pressure tap 229)

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

[0655] Reference is now made to Figure 18 , Figure 18is a schematic view of a ventricular assist device 20 according to some applications of the present application, the distal tip portion 120 of the device is a radially expandable atraumatic distal tip portion. As described above, the ventricular assist device generally includes a tube 24 that is passed through the aortic valve of a subject such that a proximal portion of the tube is disposed within the aorta of the subject and a distal portion of the tube is disposed within the left ventricle of the subject. The tube 24 defines one or more blood inlet openings 108 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 the one or more blood inlet openings and pumps blood out of the tube 24 into the aorta through the one or more blood outlet openings. Generally, the radially expandable atraumatic distal tip portion 120 is disposed within the left ventricle of the subject distal relative to the one or more blood inlet openings. The distal tip portion is configured to be inserted into the left ventricle in a radially constrained configuration. Generally, at least a portion of the distal tip portion is disposed within a delivery catheter 143 (e.g., shown in Figure 1B ) and the delivery catheter holds the distal tip portion in the radially constrained configuration during insertion of the distal tip portion into the left ventricle. The distal tip portion is configured to assume a non-radially constrained configuration within the left ventricle of the subject in which at least a portion 232 of the distal tip portion is radially expanded relative to the radially constrained configuration of the distal tip.

[0656] For some applications, the radially expandable atraumatic distal tip portion 120 includes a frame 234 made of a shape memory material, such as nitinol, that is set such that the frame radially expands upon release from the delivery catheter. Generally, the frame is covered with a biocompatible blood impermeable material 236, such as polyurethane, polyester, and / or silicone, that is generally configured to form a continuous surface covering the frame. For some applications, the distal tip portion additionally includes an atraumatic distal tip 238 that can have a similar shape as the distal tip portion 120 as described above with reference to Figure 6C and / or below with reference to FIG. 21B .

[0657] The radially expandable atraumatic distal tip portion 120 is generally configured such that in the non-radially constrained configuration of the distal tip portion, the radially expandable portion 232 of the distal tip portion separates the one or more blood inlet openings 108 from internal structures of the left ventricle in three dimensions. In this manner, the radially expandable portion 232 of the distal tip portion separates the one or more blood inlet openings 108 from the interventricular septum, chordae tendinae, papillary muscles, and / or the apex of the left ventricle. For some applications, the radially expandable portion 232 of the distal tip portion is shaped such that it directs blood flow from the left ventricle into the one or more blood inlet openings as illustrated by the arrows in FIG. 18As indicated by arrow 240 in the image.

[0658] Now for reference FIGS. 19A-19B ,Should FIGS. 19A-19B This is a schematic diagram of a ventricular assist device 20 according to some applications of the present invention, wherein the distal end portion 120 of the ventricular assist device is a radially expandable, non-invasive distal end portion. Also refer to... FIGS. 20A-20B ,Should FIGS. 20A-20B This is a schematic diagram of a ventricular assist device 20 according to some alternative applications of the present invention, wherein the distal end portion 120 of the ventricular assist device is a radially expandable, non-invasive distal end portion. FIG. 19A and FIG. 20A The distal end portion is shown in its radially constrained configuration, and this distal end portion is at least partially disposed within the delivery conduit 143, and FIG. 19B and FIG. 20B The distal end portion in its non-radial constrained configuration is shown. Generally, as... FIGS. 19A-19B and FIGS. 20A-20B The distal end portion 120 shown in the figure has the same characteristics as described above. FIG. 18 The function described in the distal end portion 120 shown in the figure is substantially similar to that of the function described in the figure.

[0659] As described above, typically, during insertion of the distal end into the left ventricle, at least a portion of the distal distal portion 120 is disposed within the delivery catheter 143, and the delivery catheter holds the distal distal portion within a radially constrained configuration, such as... FIG. 19A and FIG. 20AThe distal tip portion is configured so that, when the delivery catheter holds the distal tip portion in a radially constrained configuration, a distal region 244 of the distal tip portion protrudes from a distal end of the delivery catheter. Typically, at least in the radially constrained configuration of the distal tip portion, the distal region is at least semi-rigid and shaped to radially converge in a longitudinal direction toward a distal end 246 of the distal tip portion. Typically, 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 tip 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 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 the catheter into a punctured blood vessel by placing a first guide wire through the distal region of the distal tip portion. Subsequently, the distal region is used to guide the catheter along an arcuate anatomical structure (e.g., the aortic arch) by tracing the course and shape of a second guide wire that is less stiff than the first guide wire. For some such applications, the delivery catheter 143 itself acts as an introducer. Typically, the delivery catheter has an inner diameter of less than 9 mm. For example, the delivery catheter can be an 8 French catheter. For some applications, the delivery catheter is inserted through the puncture via a short introducer device.

[0660] For some applications, the distal tip portion 120 is configured so that, in the non-radially constrained configuration of the distal tip portion, the distal end 246 of the distal tip portion is enclosed within the radially expandable portion 232 of the distal tip portion. For some applications, the distal end is retracted proximally so that the distal end is enclosed within the radially expandable portion. For example, the distal tip portion can include a spring 249 and / or an elastic material configured to retract the distal end of the distal tip portion, as shown in the transition from FIGS. 19A-19B For some applications, the distal end is flipped so that the distal end becomes enclosed within the radially expandable portion of the distal tip portion. For example, the transition from FIGS. 20A-20B is shown with the distal end 246 of the distal tip portion 120 flipped over, as indicated by arrow 264. For some applications, by the distal end becoming enclosed within the radially expandable portion, the distal end is prevented from becoming entangled within chordae tendinae and / or from causing damage to the internal structures of the left ventricle.

[0661] Reference is made to FIG. 19BFor some applications, the distal tip portion comprises a plurality of longitudinal struts 248 shaped to flex 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, typically configured to form a continuous surface covering the struts. Reference is made to FIG. 20B For some applications, the distal tip portion comprises 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, typically configured to form a continuous surface covering the braided shape memory material. Alternatively, the braided shape memory material is not covered.

[0662] Reference is now made to FIG. 21A , FIG. 21B , FIG. 21C and FIG. 21D , FIG. 21A , FIG. 21B , FIG. 21A and FIG. 21B are schematic illustrations of a distal tip portion 120 of a ventricular assist device 20 according to some applications of the present application, the distal tip portion being configured to be atraumatic. As shown in FIG. 6C , for some applications, the distal tip portion comprises a J-shaped tip 270 at its distal end. As shown in FIGS. 6A-6C , for some applications, the distal tip portion comprises a spherical tip 272 at its distal end. As shown in FIG. 21A and FIG. 21C , for some applications, the distal tip portion is shaped externally to define a frustum 274 in a location proximal to the J-shaped tip or the spherical tip. Typically, the proximal end 276 of the frustum serves as a stopper for preventing the advancement of the delivery catheter 143 past the proximal end in a manner generally similar to that described with reference to FIG. 16D to the flared portion 124.

[0663] For some applications, the tip portion has a straightened configuration in which the tip portion is shaped to define a frustum extending from a proximal end of the frustum to a distal end of the distal tip portion. For example, a guide wire, such as guide wire 10, inserted through the lumen 122 defined by the tip portion (shown in FIG. 21D ) can hold the tip portion in its straightened configuration. For some such applications, the tip portion has a non-constrained configuration (the tip portion is configured to assume this configuration within the ventricle (e.g., as a result of the guide wire being removed from within the tip portion)) in which a distal portion of the frustum is shaped as a J-shaped tip, as shown in FIG. 21C .

[0664] As FIG. 21D illustrated in FIG. 18 , for some applications, the outer surface of the distal tip portion includes an inflatable portion 278 (e.g., a balloon) that is configured to be inflated when the distal tip portion is placed within the left ventricle of a subject. For some such applications, an inflation lumen for inflating the inflatable portion is configured to pass through the outer tube 142, and then along the outer surface of the tube 24, and to the inflatable portion of the distal tip portion. For example, the inflation lumen can be configured in a manner generally similar to the blood pressure measurement tube 210 as illustrated in

[0665] As FIG. 22A illustrated in , for some applications, the outer surface of the distal tip portion includes a radially expandable portion 282 (e.g., a radially expandable mesh and / or a radially expandable frame as illustrated) that is configured to self-expand when the distal tip portion is disposed within the left ventricle of a subject.

[0666] FIG. 22B As FIG. 22A illustrated in FIG. 22B and , the atraumatic distal tip portion 120 is generally configured such that, in the inflated or radially expanded configuration of the distal tip portion, the inflated or radially expanded portion of the distal tip portion separates the one or more blood inlet openings 108 from the internal structures of the left ventricle in three dimensions. In this manner, the inflated or radially expanded portion of the distal tip portion separates the 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 or radially expanded portion of the distal tip portion is shaped such that it directs blood flow from the left ventricle into the one or more blood inlet openings, as described above with reference to the distal tip portion 120 as illustrated in

[0667] FIG. 22A Now referring to FIG. 22B , FIG. 23A and FIG. 23Bare schematic illustrations of a distal tip portion 120 of a ventricular assist device 20 in an axially strengthened configuration and a non-axially strengthened configuration, respectively, in accordance with some applications of the present application. As described above, for some applications, the distal tip portion is configured such that, when a delivery catheter holds the distal tip portion in a radially constrained configuration, a distal region 244 of the distal tip portion protrudes from a distal end of the delivery catheter. Typically, at least in the axially strengthened configuration of the distal tip portion, the distal region is at least semi-rigid and shaped to radially converge in a longitudinal direction toward a distal end 246 of the distal tip portion. Typically, the delivery catheter is inserted into the subject's vasculature via a puncture. Also, typically, the distal tip portion bounds a lumen 122 through which a guide wire 10 is inserted, as described above. For some applications, the radially converging semi-rigid distal region of the distal tip portion is configured to act as a dilator by enlarging the puncture during insertion of the delivery catheter via the puncture. In this manner, the delivery catheter and 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 the catheter into a punctured blood vessel by placing a first guide wire through the distal region of the distal tip portion. Subsequently, the distal region is used to guide the catheter along an arcuate anatomical structure (e.g., the aortic arch) by tracing the course and shape of a second guide wire that is less stiff than the first guide wire. For some such applications, the delivery catheter 143 itself acts as an introducer. Typically, the delivery catheter has an inner diameter of less than 9 mm. For example, the delivery catheter can be an 8 French catheter. For some applications, the delivery catheter is inserted through the puncture via a short introducer device.

[0668] For some applications, the distal tip 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 subject's body, a rigid or semi-rigid strengthening element 292 (e.g., a rigid or semi-rigid tube) is placed within the distal region 244 of the distal tip portion in order to strengthen the distal region. This configuration is shown in FIG. 23A . Subsequently, the strengthening element is retracted so that the distal region of the distal tip portion becomes atraumatic (e.g., resilient and flexible), as shown in FIG. 23B .

[0669] Reference is now made to FIG. 23A and FIG. 23B , FIG. 23B and FIG. 24Aare schematic illustrations of distal tip portions 120 of a ventricular assist device 20 in a radially constrained configuration and a non-radially constrained configuration, respectively, in accordance with some applications of the present application. For some applications, a distal region 144 of the distal tip portion is shaped as a cone with a slit 294 (e.g., two slits) in the cone. During insertion of the ventricular assist device into the body of a subject, the distal region maintains its conical shape by a delivery catheter 143. This configuration is shown in FIG. 24B . 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 half-circles 296 or half-ellipses around the slit, as shown in FIG. 24A . In the configuration shown in FIG. 24B , the distal tip portion is generally configured to be atraumatic and configured to separate the one or more blood inlet openings 108 from the internal structures of the left ventricle in two dimensions. In this manner, the distal tip portion separates the one or more blood inlet openings 108 from the interventricular septum, chordae tendineae, papillary muscles, and / or the apex of the left ventricle.

[0670] Reference is now made to FIG. 24A and FIG. 24B , FIG. 24B and FIG. 24B are schematic illustrations of distal tip portions 120 of a ventricular assist device 20 in a radially constrained configuration and a non-radially constrained configuration, respectively, in accordance with some applications of the present application. For some applications, a distal region 244 of the distal tip portion is shaped as a cone with a slit 294 (e.g., four slits) in the cone. During insertion of the ventricular assist device into the body of a subject, the distal region maintains its conical shape by a delivery catheter 143. This configuration is shown in FIG. 21A . 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 slit, as shown in FIGS. 18-24B . (Note that the fourth arm is hidden from view in FIGS. 6A-6C . ) In the configuration shown in FIG. 13 , the distal tip portion is generally configured to be atraumatic and configured to separate the one or more blood inlet openings 108 from the internal structures of the left ventricle in three dimensions. In this manner, the distal tip portion separates the 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 tip portion 120 has a pointed distal region 244, a diameter of the distal tip portion at a proximal end of the distal region being about equal to a diameter of the delivery catheter 143. Typically, the pointed distal region 244 has a length that is less than half (e.g., less than a quarter) of a total length of the distal tip portion. Additionally, typically, the pointed distal region has a flexibility that is greater than a flexibility of a proximal region of the distal tip 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 FIG. 3B) without any external force acting on the distal region. FIG. 25A

[0672] Typically, the distal region of the distal tip portion acts 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 tip portion. Subsequently, the distal tip portion is used to guide the catheter along an arcuate anatomical structure (e.g., the aortic arch) by tracing a 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 tip portion is configured to curl when the second guide wire is withdrawn.

[0673] For some applications, features of the distal tip portion 120 described with reference to FIG. 25A and techniques for practicing the same are combined with features of the tip portion 120 described with reference to FIG. 25A and / or FIG. 25B and techniques for practicing the same.

[0674] Reference is now made to FIG. 25C , FIG. 25B 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 application, the coupling element being configured to facilitate radial contraction (e.g., during crimping) of an impeller (e.g., the impeller 50 described above) independent of other components of the ventricular assist device. The first portion 160A and the second portion 160B are configured to become engaged with one another. 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 FIG. 25C

[0675] Reference is also made to FIGS. 25A-25C and FIG. 26 , FIG. 26 and FIG. 1A ​​is a schematic illustration of various stages of collapse of an impeller according to some applications of the present application. For some applications, prior to collapsing the outer portion of the ventricular assist device (e.g., the frame 34 of the left ventricular assist device 20, as shown), the impeller is collapsed by engaging the portions 160A and 160B with each other and axially elongating the impeller so as to radially contract the impeller. Subsequently, the outer portion of the left ventricular assist device is radially collapsed. For some applications, collapsing the impeller in this manner reduces the likelihood of the impeller becoming damaged during collapse of the outer portion of the left ventricular assist device. Subsequently, when the impeller and frame are disposed in the left ventricle of the subject, the first and second portions of the coupling element are separated from each other so that the impeller is movable relative to the frame 34.

[0676] For some applications, FIGS. 1A-26 The collapsing technique illustrated in FIG. 16A can alternatively or additionally be used in conjunction with the collapsing technique described above in which the impeller is configured to be collapsed by virtue of only one of the ends of the impeller (e.g., the proximal end of the impeller) being coupled to the axial shaft and the other end (e.g., the distal end) being slidable relative to the axial shaft. The impeller is collapsed by sliding the impeller along the shaft through the other end of the impeller so that the impeller becomes axially elongated.

[0677] Reference is now made to FIG. 1A , FIG. 1B is a schematic illustration of a blocker 300 according to some applications of the present application, the blocker 300 being configured to prevent distal advancement of the impeller 50 of the ventricular assist device 20 during extraction of the ventricular assist device from the body of the subject. As described above, typically, in order to extract the ventricular assist device from the body of the 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 can break when the impeller is pushed distally by the delivery catheter. For some applications, in the event that the drive cable breaks, then 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 so that it does not engage the shoulder 302 during regular operation of the ventricular assist device (and throughout the entire axial back-and-forth motion cycle described above).

[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 (FIG. 1) is configured to monitor the electrical activity of the heart of the subject and to determine the timing of the contractions of the left ventricle of the heart of the subject based on the electrical activity of the heart of the subject. FIG. 27A) between the most distal electrode, which is typically configured to be disposed proximate the apex of the heart, and the most proximal electrode, which is typically configured to be disposed above the aortic valve. Electrical conductance of the electrical current between each pair of electrodes is then measured by the computer processor. For some applications, the application of electrical current and the measurement of electrical conductance is performed using a technique generally similar to that described in Cassidy et al., “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 for the subject based on the electrical conductance measurements. For some applications, the computer processor controls the rotational rate of the impeller in response to the derived pressure-volume loop.

[0679] With respect to references FIG. 27A All aspects of the ventricular assist device 20 described, note that although FIGS. 1A-26 and FIG. 27AA ventricular assist device 20 in a left ventricle of a subject is shown, but for some applications the device 20 is placed within a right ventricle of a subject, such that the device passes through a pulmonary valve of the subject, and the techniques described herein are applied with the necessary modifications. For some applications, components of the device 20 can be adapted for use with different types of blood pumps. For example, aspects of the present invention can be applicable to pumps for pumping blood from a vena cava and / or right atrium into a right ventricle, from a vena cava and / or right atrium into a pulmonary artery, and / or from a renal vein into a vena cava. Such aspects can include features of the impeller 50, the pump portion 27, features of the drive cable 130, devices and methods for measuring blood pressure, etc. Alternatively or additionally, the device 20 and / or a portion thereof (e.g., the impeller 50, even without the tube 24) is placed within a different part of a subject’s body in order to assist in pumping blood from that part. For example, the device 20 and / or a portion thereof (e.g., the impeller 50, even without the tube 24) can be placed in a blood vessel and can be used to pump blood through the blood vessel. For some applications, the device 20 and / or a portion thereof (e.g., the impeller 50, even without the tube 24) is configured to be placed within a subclavian vein or jugular vein at a junction of a vein with a lymphatic duct and used to increase flow of lymph fluid from the lymphatic duct to the vein, with the necessary modifications. Since the scope of the present invention includes use of the devices and methods described herein in anatomical locations other than the left ventricle and aorta, the ventricular assist device and / or a portion thereof is sometimes referred to herein (in the specification and claims) as a blood pump.

[0680] Reference is now made to FIG. 27B and 27B , which FIG. 27B and 27B are schematic illustrations of a ventricular assist device 308 according to some applications of the present invention, which device includes a valve 70 to prevent backflow of blood, for example, in the event of a malfunction of the impeller 50 of the ventricular assist device. Unlike the ventricular assist device 20 described above with reference to FIG. 28A , 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 WO 18 / 078615, which is incorporated by reference herein). For some applications, the impeller is constructed in a manner generally similar to the impeller 50 described above. The impeller is disposed at a 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. FIG. 28B A ventricular assist device is shown configured when the impeller of the ventricular assist device is functioning normally, such that there is blood flow from the left ventricle 22 via the tube 312 (which passes through the aortic valve 26) to the aorta 30, which is indicated by the arrow 72.

[0681] For some applications, the tube 312 includes a valve 70 located at a region of the tube, the valve 70 configured to be disposed distal relative to the impeller 50 and proximal relative to the aortic valve, as shown in FIG. 28C . For example, in the event of a failure of the impeller 50 such that there is backflow of blood via the tube 312 (as indicated by the blood flow arrow 73 in FIG. 28A ), 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 a proximal end of the tube, the valve 70 configured to be disposed in the aorta.

[0682] Reference is now made to FIG. 28B , FIG. 28C and FIGS. 1A-26 , FIG. 28A , FIG. 28B and FIG. 28B are schematic illustrations of a ventricular assist device 308 according to some applications of the present application, the device including a safety balloon 80 to prevent backflow of blood, for example, in the event of a failure of the impeller of the ventricular assist device. Unlike the ventricular assist device 20 described above with reference to FIG. 28C , 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 WO 18 / 078615, which is incorporated by reference herein). For some applications, the impeller is constructed in a substantially similar manner to the impeller 50 described above. The impeller is disposed at a proximal end of a tube 312 (e.g., a polyester tube), the tube 312 passing through the aortic valve, and a frame 310 supports the tube in an open configuration. FIG. 28C is shown a ventricular assist device configured when the impeller of the ventricular assist device is functioning normally such that there is blood flow from the left ventricle 22 via the tube 312 (which passes through the aortic valve 26) to the aorta 30, the blood flow indicated by arrow 72. For some applications, the ventricular assist device 308 includes a balloon 80 located at a region of the tube, the balloon 80 configured to be disposed distal relative to the impeller 50 and proximal relative to the aortic valve, as shown in ​ . For example, in the event of a failure of the impeller 50 such that there is backflow of blood via the tube 312 (as indicated by the blood flow arrow 73 in ​ ), the computer processor 25 is configured to inflate the balloon such that the tube 312 becomes occluded and there is substantially no reverse blood flow from the aorta to the left ventricle.

[0683] For some applications, the ventricular assist device 308 includes a balloon 80 located at a distal end of the tube 312, the balloon 80 configured to be disposed in the left ventricle, as shown in ​ . For example, in the event of a failure of the impeller 50 such that there is backflow of blood via the tube 312 (as indicated by the blood flow arrow 73 in ​In the case that the blood flow arrow 73 indicates reverse blood flow (from the left ventricle to the aorta), the computer processor 25 is configured to deflate the balloon such that the tube 312 becomes unobstructed and reverse blood flow from the aorta to the left ventricle is substantially present.

[0684] The scope of the present application 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 to Tuval, filed November 21, 2017, entitled "Blood pumps" (published as WO 18 / 096531), which claims priority to US provisional patent application 62 / 425,814 to Tuval, filed November 23, 2016;

[0686] International application PCT / IL2017 / 051158 to Tuval, filed October 23, 2017, entitled "Ventricular assist device" (published as WO 18 / 078615), which claims priority to US 62 / 412,631 to Tuval, filed October 25, 2016, and US 62 / 543,540 to Tuval, filed August 10, 2017;

[0687] International patent application PCT / IL2017 / 051092 to Tuval, filed September 28, 2017, entitled "Blood vessel tube" (published as WO 18-061002), which claims priority to US provisional patent application 62 / 401,403 to Tuval, filed September 29, 2016;

[0688] US 2018 / 0169313 to Schwammenthal, which is the US national stage of international patent application PCT / IL2016 / 050525 to Schwammenthal, filed May 18, 2016, entitled "Blood pump" (published as WO 16 / 185473), which claims priority to US provisional patent application 62 / 162,881 to Schwammenthal, filed May 18, 2015, entitled "Blood pump";

[0689] US 2017 / 0100527 to Schwammenthal, which is the U.S. National Stage of International Patent Application PCT / IL2015 / 050532 to Schwammenthal, entitled "Blood pump", published as WO 15 / 177793, filed May 19, 2015, which claims priority from U.S. Provisional Patent Application 62 / 000,192 to Schwammenthal, entitled "Blood pump", filed May 19, 2014;

[0690] U.S. Patent 10,039,874 to Schwammenthal, which is the U.S. National Stage of International Patent Application PCT / IL2014 / 050289 to Schwammenthal, entitled "Renal pump", published as WO 14 / 141284, filed March 13, 2014, which claims priority from: (a) U.S. Provisional Patent Application 61 / 779,803 to Schwammenthal, entitled "Renal pump", filed March 13, 2013, and (b) U.S. Provisional Patent Application 61 / 914,475 to Schwammenthal, entitled "Renal pump", filed December 11, 2013;

[0691] U.S. Patent 9,764,113 to Tuval, entitled "Curved catheter", issued September 19, 2017, which claims priority from U.S. Provisional Patent Application 61 / 914,470 to Tuval, entitled "Curved catheter", filed December 11, 2013, and

[0692] U.S. Patent 9,597,205 to Tuval, which is the U.S. National Stage of International Patent Application PCT / IL2013 / 050495 to Tuval, entitled "Prosthetic renal valve", published as WO 13 / 183060, filed June 6, 2013, which claims priority from U.S. Provisional Patent Application 61 / 656,244 to Tuval, entitled "Prosthetic renal valve", filed June 6, 2012.

[0693] Those skilled in the art will realize that the present application is not limited to the examples herein specifically set forth and that the scope of the present application includes combinations and sub-combinations of the various features described herein above as well as variations and modifications thereof which will occur to those skilled in the art upon reading the foregoing description.

Claims

1. A medical device, the device comprising: a blood pump (27), the blood pump (27) comprising: - an impeller (50) comprising a proximal bushing (64) and a distal bushing (58), and configured to pump blood through a body of a subject; - a frame (34) configured to be disposed around the impeller (50), the frame comprising a proximal bearing (116) disposed proximally relative to the impeller (50) and a distal bearing (118) disposed distally relative to the impeller (50); - an axial shaft (92) configured to pass through the proximal bearing (116) and the distal bearing (118) of the frame (34) and the proximal bushing (64) and the distal bushing (58) of the impeller (50), the axial shaft (92): -- being coupled to at least one of the proximal bushing (64) and the distal bushing (58) of the impeller (50) such that the at least one bushing is held in an axially fixed position relative to the axial shaft (92), and -- not being held in an axially fixed position relative to the proximal bearing (116) and the distal bearing (118); and - a sensor (84) configured to detect an indication of axial motion of the impeller (50), and configured to generate a sensor signal in response thereto; and a computer processor (25) configured to receive the sensor signal and configured to generate an output in response thereto.

2. The device of claim 1, wherein the blood pump (27) does not comprise any thrust bearing configured to be disposed within the body of the subject.

3. The device of claim 1, wherein the blood pump (27) further comprises one or more thrust bearings configured to be disposed outside of the body of the subject, and wherein opposition to thrust generated by rotation of the impeller (50) is provided solely by the one or more thrust bearings disposed outside of the body of the subject.

4. The device of any of claims 1-3, further comprising: a magnet (82), the impeller (50) being coupled to the magnet (82) such that axial motion of the impeller (50) causes axial motion of the magnet (82); wherein the sensor (84) is configured to detect a magnetic flux generated by the magnet (82), and configured to generate the sensor signal in response thereto.

5. The device of claim 1, wherein the computer processor (25) is configured to generate an output indicative of a cardiac cycle of the subject in response to receiving the sensor signal.

6. The device of claim 1, wherein the computer processor (25) is configured to determine a left ventricular pressure of the subject based at least in part on the sensor signal.

7. The apparatus of claim 1, wherein the computer processor (25) is configured to change a rate of rotation of the impeller (50) based at least in part on the sensor signal.

8. The apparatus of claim 4, wherein the computer processor (25) is configured to generate an output indicative of a cardiac cycle of a subject in response to receiving the sensor signal.

9. The apparatus of claim 4, wherein the computer processor (25) is configured to determine a left ventricular pressure of a subject based at least in part on the sensor signal.

10. The apparatus of claim 4, wherein the computer processor (25) is configured to change a rate of rotation of the impeller (50) based at least in part on the sensor signal.

11. The apparatus of claim 7 or 10, wherein the computer processor (25) is configured to: determine a left ventricular pressure of a subject based at least in part on the sensor signal, and change a rate of rotation of the impeller (50) based at least in part on the determined left ventricular pressure.

12. The apparatus of any one of claims 1-3, wherein the impeller (50) is configured to pump blood from a first location within a body of a subject to a second location within the body of the subject, and wherein the impeller (50) is configured to move axially back and forth relative to the frame (34) in response to periodic changes in a pressure differential between the first location and the second location.

13. The apparatus of claim 12, wherein the impeller (50) is configured to pump blood from a left ventricle of a subject to a main artery of the subject, and wherein the impeller (50) is configured to move axially back and forth relative to the frame (34) in response to periodic changes in a pressure differential between the left ventricle and the main artery.

14. The apparatus of claim 12, further comprising: a motor (74) configured to drive the impeller (50) to pump blood through the body of the subject by causing the impeller (50) to rotate in a given direction of rotation; and a drive cable (130) configured to extend from outside the body of the subject to the axial shaft (92), the drive cable (130) being configured to transmit rotational motion from the motor (74) to the impeller (50) by rotation, at least a portion of the drive cable (130) comprising a plurality of wires (134) disposed in a coiled configuration such that, in response to the drive cable (130) being rotated in the given direction of rotation, the plurality of wires (134) disposed in the coiled configuration are at least partially uncoiled such that the portion of the drive cable (130) is axially shortened.

15. The apparatus of claim 12, 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 (116) and the distal bearing (118). ​ 16. The apparatus of claim 15, wherein the axial shaft (92) is configured to clean an interface between the axial shaft (92) and the proximal bearing (116) and the distal bearing (118) by the axial back-and-forth movement relative to the proximal bearing (116) and the distal bearing (118).

17. The apparatus of claim 15, wherein the axial shaft (92) is configured to reduce heat buildup at an interface between the axial shaft (92) and the proximal bearing (116) and the distal bearing (118) by the axial back-and-forth movement relative to the proximal bearing and the distal bearing relative to a situation if the axial shaft (92) does not move the axial back-and-forth movement relative to the proximal bearing (116) and the distal bearing (118).

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