Ventricular assist device

Abstract

The present application relates to a ventricular assist device. Apparatus and methods are described herein, including a blood pump (20) configured to be placed within a subject's body, the blood pump comprising an impeller (50) and a frame (34) disposed around the impeller, the impeller comprising proximal and distal bushings (64, 58), the frame comprising proximal and distal bearings (116, 118). An axial shaft (92) passes through the proximal and distal bearings (116, 118) of the frame and the proximal and distal bushings (64, 58) of the impeller (50). The impeller (50) defines a radially constrained configuration in which the impeller (50) is introduced into the subject's body and a non-radially constrained configuration in which the impeller (50) is configured to pump blood within the subject's body. The impeller (50) is changed 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 the application with application date of January 10, 2019, application number 201980007116.9, and invention name “Ventricular Assist Device”.

[0002] CROSS-REFERENCE TO RELATED APPLICATIONS

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

[0004] Sohn’s U.S. provisional patent application 62 / 615,538, entitled “Ventricular assist device,” filed January 10, 2018;

[0005] Sohn’s U.S. provisional patent application 62 / 665,718, entitled “Ventricular assist device,” filed May 2, 2018;

[0006] Tuval’s U.S. provisional patent application 62 / 681,868, entitled “Ventricular assist device,” filed June 7, 2018; and

[0007] Tuval’s U.S. provisional patent application 62 / 727,605, titled “Ventricular assist device,” filed September 6, 2018.

[0008] All of the above-cited applications are incorporated herein by reference.

[0009] Field of the Invention

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

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

[0012] Overview of the implementation plan

[0013] According to some applications of the present invention, a ventricular assist device includes an impeller disposed on an axial shaft with a frame disposed around the impeller. The ventricular assist device typically includes a tube that passes through an aortic valve of a subject such that a proximal end of the tube is disposed in the aorta of the subject and a distal end of the tube is disposed in the left ventricle of the subject. The impeller, axial shaft, and frame are disposed within a distal portion of the tube within the left ventricle of the subject. Typically, the impeller is configured to pump blood from the left ventricle into the aorta by rotation. The tube typically defines one or more blood inlet openings at the distal end of the tube through which blood flows from the left ventricle into the tube during operation of the impeller. For some applications, the proximal portion of the tube defines one or more blood outlet openings through 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. An axial shaft typically passes through the proximal bearing and distal bearing of the frame and the proximal bushing and distal bushing 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 maintained 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 maintained in an axially fixed position relative to the axial shaft. Typically, the impeller defines a radially constrained configuration and a non-radially constrained configuration, in which the impeller is introduced into the body of a subject and in which the impeller is configured to pump blood within the body of the subject. For some applications, the impeller is changed from its radially constrained configuration to its non-radially constrained configuration by sliding the distal bushing on the axial shaft.

[0015] Typically, the axial shaft is not maintained in an axially fixed position relative to the proximal and distal bearings. Furthermore, typically, the ventricular assist device (and / or the blood pump portion thereof) does not include any thrust bearings configured to be disposed within the body of a subject. For some applications, the ventricular assist device includes one or more thrust bearings disposed externally to the body of the subject, and opposition to thrust generated by rotation of the impeller is provided solely by the one or more thrust bearings disposed externally to the body of the subject.

[0016] For some applications, a motor drives the impeller by rotating it to pump blood from the left ventricle to the aorta, and the impeller is configured to move axially relative to the frame in response to changes in the pressure differential between the left ventricle and the aorta. For some applications, a computer processor measures an indication of the axial movement of the impeller. For some applications, the computer processor derives the subject's cardiac cycle, the pressure differential between the left ventricle and the aorta, and / or the subject's left ventricular pressure based on the measured indication of the axial movement of the impeller. For some applications, the computer processor varies the rotation rate of the impeller based at least in part on the sensor signal. For example, the computer processor may determine the subject's left ventricular pressure based at least in part on the sensor signal, and may vary the rotation rate of the impeller based at least in part on the determined left ventricular pressure. For some applications, the computer processor decreases the rotation rate of the impeller in response to determining that the subject's left ventricular pressure has decreased. For some applications, the impeller is coupled to a magnet such that axial movement of the impeller causes axial movement of the magnet, and the computer processor measures the indication of the axial movement of the impeller by measuring magnetic flux generated by the magnet.

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

[0018] For some applications, a drive cable includes a first portion and a second portion, the first portion being configured to be at least partially disposed within an aortic arch of a subject, the second portion being configured to be at least partially disposed within a descending aorta of the subject, and the first portion having a greater flexibility than the second portion. For example, the first portion of the drive cable can include a first number of wires arranged in a coiled configuration, and the second portion of the drive cable can include a second number of wires arranged in a coiled configuration, with the first number being less than the second number. For example, the first portion of the drive cable can include between 4 and 8 wires arranged in a coiled configuration, and the second portion of the drive cable can include between 8 and 12 wires arranged in a coiled configuration.

[0019] For some applications, the impeller includes at least one helical elongated element (and typically three helical elongated elements), and a spring disposed within the helical elongated element and along an axis around which the helical elongated element is wound. Typically, a film 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, the frame is disposed about the impeller. For some applications, the ventricular assist device includes a stator comprising a plurality of curved protrusions coupled to a proximal end of the frame. Typically, the curvature of the curved protrusions is opposite to a direction of rotation of the impeller. For some applications, the curvature of the curved protrusions is such that the curved protrusions gradually become more closely parallel to a longitudinal axis of the frame from a distal end of the curved protrusion to a proximal end of the curved protrusion. Typically, the curved protrusions comprise a plurality of curved struts integral with the frame, and a flexible material (e.g., silicone) extending from the curved struts. For some applications, the flexible material is shaped to define a lumen therethrough.

[0021] As described above, the impeller is typically disposed within a tube extending from the subject's left ventricle to the subject's aorta (sometimes referred to herein as the "blood pump tube"). For some applications, at least one blood pressure measuring tube (which defines 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 measuring tube is in direct fluid communication with the subject's blood flow outside the blood pump tube. The pressure sensor measures the blood pressure within the blood pressure measuring tube. For some applications, the blood pressure measuring tube is configured to pass from the proximal end of the blood pump tube along the outer surface of the blood pump tube to the opening at the distal end of the blood pressure measuring tube. Typically, the blood pressure measuring tube is a left ventricular blood pressure measuring tube that is 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 subject's left ventricle near the impeller, and the pressure sensor is configured to measure the subject's left ventricular pressure by measuring the blood pressure within the left ventricular blood pressure measuring tube.

[0022] Typically, 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 includes a radially expandable atraumatic distal tip portion that is configured to be disposed distally within the left ventricle of a subject relative to the one or more blood inlet openings. The distal tip portion is typically configured to be inserted into the left ventricle in a radially constrained configuration and is configured to assume a non-radially constrained configuration within the left ventricle of the subject, wherein at least the radially expandable portion of the distal tip portion radially expands relative to the radially constrained configuration of the distal tip portion. Typically, 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 ventricular septum, chordae tendineae, papillary muscles, and / or the apex of the left ventricle. Furthermore, typically, in its non-radially constrained configuration, the radially expandable portion of the distal tip portion separates the one or more blood inlet openings from the internal structures of the left ventricle in three dimensions. For some applications, in its non-radially constrained configuration, the radially expandable portion of the distal 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, the distal region of the distal tip portion is configured to be at least semi-rigid and shaped to converge radially along a longitudinal direction toward a distal end of the distal tip portion. Typically, the ventricular assist device is configured to be inserted into the body of the subject via a puncture in the body of the subject. 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] In general, in the specification and claims of this application, the term "proximal" and related terms, when used with reference to a device or a portion thereof, should be interpreted to mean the end of the device or portion of the device that, when inserted into the body of a subject, is generally closer to the point through which the device is inserted into the body of the subject. The term "distal" and related terms, when used with reference to a device or a portion thereof, should be interpreted to mean the end of the device or portion of the device that, when inserted into the body of a subject, is generally further away from the point through which the device is inserted into the body of the subject.

[0025] The scope of the present invention includes the use of the apparatus and methods described herein in anatomical locations other than the left ventricle and aorta.Thus, a 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 invention, a device is further provided, 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 about the impeller, the frame including 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 maintained 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 retained 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 a body of a 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 sleeve on the axial shaft.

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

[0036] at least one helical elongate element extending from said proximal hub to said distal hub;

[0037] a spring disposed within the helical elongated element and along the axis about which the helical elongated element is wound;

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

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

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

[0041] The delivery catheter is configured to maintain 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 hub to slide proximally on the axial shaft such that the impeller assumes its non-radially constrained configuration, and

[0043] To retract the impeller from the subject's body, the delivery catheter is configured to cause the impeller to assume its radially constrained configuration 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 sleeve to slide distally on the axial shaft.

[0044] According to some applications of the present invention, a device is further provided, comprising:

[0045] A ventricular assist device, comprising:

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

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

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

[0049] The impeller is configured to move axially back and forth relative to the frame in response to cyclical changes in a pressure differential between the left ventricle and the aorta.

[0050] In some applications:

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

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

[0053] The ventricular assist device further includes an axial shaft configured to pass through the proximal and distal bearings defined by the frame and the proximal and distal bushings 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 retained in an axially fixed position relative to the axial shaft and is not retained in an axially fixed position relative to the proximal bearing and the distal bearing.

[0055] In some applications, the ventricular assist device does not include any thrust bearings configured to be positioned within the body of a subject.

[0056] In some applications, the ventricular assist device also includes one or more thrust bearings configured to be positioned external to 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 positioned external to the subject's body.

[0057] In some applications,

[0058] The motor is configured to drive the impeller by rotating the impeller in a given rotational direction to pump blood from the subject's left ventricle to the subject's aorta; and

[0059] The ventricular assist device further comprises:

[0060] an axial shaft on which the impeller is disposed; and

[0061] a drive cable configured to extend from outside the subject's body to the axial axis, 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 arranged in a coiled configuration such that in response to rotation of the drive cable in the given rotational direction, the plurality of wires arranged in the coiled configuration at least partially unwind, causing the portion of the drive cable to axially shorten.

[0062] In some applications, the device further comprises:

[0063] a sensor configured to detect an indication of axial movement of the impeller and to generate a sensor signal in response thereto; and

[0064] A computer processor is configured to receive the sensor signal and to generate an output in response thereto.

[0065] 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 vary a rotation rate of the impeller based at least in part on the sensor signal.

[0066] In some applications, a computer processor is configured to:

[0067] determining a left ventricular pressure of the subject based at least in part on the sensor signal, and

[0068] The rotational rate of the impeller is varied based at least in part on the determined left ventricular pressure.

[0069] In some applications, the computer processor is configured to reduce the rotational rate of the impeller in response to determining that left ventricular pressure of the subject has decreased.

[0070] In some applications, the device further comprises:

[0071] a magnet, the impeller being coupled to the magnet such that axial movement of the impeller causes axial movement of the magnet;

[0072] a sensor configured to detect magnetic flux generated by the magnet and to generate a sensor signal in response thereto; and

[0073] A computer processor is configured to receive the sensor signal and to generate an output in response thereto.

[0074] 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 vary a rotation rate of the impeller based at least in part on the sensor signal.

[0075] In some applications, a computer processor is configured to:

[0076] determining a left ventricular pressure of the subject based at least in part on the sensor signal, and

[0077] The rotational rate of the impeller is varied based at least in part on the determined left ventricular pressure.

[0078] In some applications, the computer processor is configured to reduce the rotational rate of the impeller in response to determining that left ventricular pressure of the subject has decreased.

[0079] In some applications:

[0080] The impeller includes a proximal bushing and a distal bushing;

[0081] The frame includes a proximal bearing and a distal bearing;

[0082] 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;

[0083] The impeller is coupled to the axial shaft such that the impeller causes axial back-and-forth movement of the axial shaft relative to the proximal and distal bearings of the frame.

[0084] In some applications, the axial shaft is configured to clean interfaces between the axial shaft and the proximal and distal bearings of the frame by performing the axial reciprocating axial movement relative to the proximal and distal bearings of the frame. In some applications, the axial shaft is configured to reduce heat buildup at interfaces between the axial shaft and the proximal and distal bearings of the frame by performing the axial reciprocating axial movement relative to the proximal and distal bearings of the frame, relative to a situation where the axial shaft does not perform the axial reciprocating axial movement relative to the proximal and distal bearings of the frame.

[0085] According to some applications of the present invention, a device is further provided, comprising:

[0086] A blood pump, comprising:

[0087] an impeller comprising a proximal hub and a distal hub and configured to pump blood through a body of a subject;

[0088] a frame configured to be disposed about the impeller, the frame including a proximal bearing and a distal bearing;

[0089] an axial shaft configured to pass through the proximal and distal bearings of the frame and the proximal and distal bushings of the impeller, the axial shaft:

[0090] at least one of the proximal bushing and the distal bushing coupled to the impeller such that the at least one bushing is retained in an axially fixed position relative to the axial shaft, and

[0091] is not held in an axially fixed position relative to the proximal bearing and the distal bearing.

[0092] In some applications, the blood pump does not include any thrust bearings configured to be positioned within the body of the subject. In some applications, the blood pump further includes one or more thrust bearings configured to be positioned outside the body of the subject, and wherein opposition to thrust generated by rotation of the impeller is provided solely by the one or more thrust bearings positioned outside the body of the subject.

[0093] In some applications, the device also includes:

[0094] a sensor configured to detect an indication of axial movement of the impeller and to generate a sensor signal in response thereto; and

[0095] A computer processor is configured to receive the sensor signal and to generate an output in response thereto.

[0096] 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 vary a rotation rate of the impeller based at least in part on the sensor signal.

[0097] In some applications, a computer processor is configured to:

[0098] determining a left ventricular pressure of the subject based at least in part on the sensor signal, and

[0099] The rotational rate of the impeller is varied based at least in part on the determined left ventricular pressure.

[0100] In some applications, the computer processor is configured to reduce the rotational rate of the impeller in response to determining that left ventricular pressure of the subject has decreased.

[0101] In some applications, the device further comprises:

[0102] a magnet, the impeller being coupled to the magnet such that axial movement of the impeller causes axial movement of the magnet;

[0103] a sensor configured to detect magnetic flux generated by the magnet and to generate a sensor signal in response thereto; and

[0104] A computer processor is configured to receive the sensor signal and to generate an output in response thereto.

[0105] 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 vary a rotation rate of the impeller based at least in part on the sensor signal.

[0106] In some applications, a computer processor is configured to:

[0107] determining a left ventricular pressure of the subject based at least in part on the sensor signal, and

[0108] The rotational rate of the impeller is varied based at least in part on the determined left ventricular pressure.

[0109] In some applications, the computer processor is configured to reduce the rotational rate of the impeller in response to determining that left ventricular pressure of the subject has decreased.

[0110] 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 cyclical changes in the pressure differential between the first location and the second location. In some applications, the impeller is configured to pump blood from the 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 cyclical changes in the pressure differential between the left ventricle and the aorta. In some applications, the impeller is configured to pump blood from the subject's right ventricle to the subject's pulmonary artery, and the impeller is configured to move axially back and forth relative to the frame in response to cyclical changes in the pressure differential between the right ventricle and the pulmonary artery. In some applications, the impeller is configured to pump blood from the subject's right atrium to the subject's right ventricle, and the impeller is configured to move axially back and forth relative to the frame in response to cyclical changes in the pressure differential between the right atrium and the right ventricle. In some applications, the impeller is configured to pump blood from the vena cava of the subject to the right ventricle of the subject, and the impeller is configured to move axially back and forth relative to the frame in response to cyclical changes in the pressure differential between the vena cava and the right ventricle. In some applications, the impeller is configured to pump blood from the right atrium of the subject to the pulmonary artery of the subject, and the impeller is configured to move axially back and forth relative to the frame in response to cyclical changes in the pressure differential between the right atrium and the pulmonary artery. In some applications, the impeller is configured to pump blood from the vena cava of the subject to the pulmonary artery of the subject, and the impeller is configured to move axially back and forth relative to the frame in response to cyclical changes in the pressure differential between the vena cava and the pulmonary artery.

[0111] In some applications, the device further comprises:

[0112] a motor configured to drive the impeller by rotating the impeller in a given rotational direction to pump blood through the subject's body; and

[0113] a drive cable configured to extend from outside the subject's body to the axial axis, 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 arranged in a coiled configuration such that in response to rotation of the drive cable in the given rotational direction, the plurality of wires arranged in the coiled configuration at least partially unwind, causing the portion of the drive cable to axially shorten.

[0114] In some applications, the impeller is coupled to the axial shaft such that the impeller causes the axial shaft to perform axial reciprocating motion relative to the proximal and distal bearings of the frame. In some applications, the axial shaft is configured to clean interfaces between the axial shaft and the proximal and distal bearings of the frame by performing the axial reciprocating motion relative to the proximal and distal bearings of the frame. In some applications, the axial shaft is configured to reduce heat buildup at interfaces between the axial shaft and the proximal and distal bearings of the frame by performing the axial reciprocating motion relative to the proximal and distal bearings of the frame relative to a situation where the axial shaft does not perform the axial reciprocating motion relative to the proximal and distal bearings of the frame.

[0115] According to some applications of the present invention, a device is further provided, comprising:

[0116] A blood pump, comprising:

[0117] an impeller configured to be placed within the body of a subject and configured to pump blood through the body of the subject;

[0118] a frame configured to be disposed around the impeller,

[0119] The blood pump does not include any thrust bearings configured to be positioned within the body of a subject.

[0120] In some applications, the blood pump further includes one or more thrust bearings configured to be disposed externally to 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 externally to the subject's body.

[0121] In some applications, the device further comprises:

[0122] a sensor configured to detect an indication of axial movement of the impeller and to generate a sensor signal in response thereto; and

[0123] A computer processor is configured to receive the sensor signal and to generate an output in response thereto.

[0124] 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 vary a rotation rate of the impeller based at least in part on the sensor signal.

[0125] In some applications, a computer processor is configured to:

[0126] determining a left ventricular pressure of the subject based at least in part on the sensor signal, and

[0127] The rotational rate of the impeller is varied based at least in part on the determined left ventricular pressure.

[0128] In some applications, the computer processor is configured to reduce the rotational rate of the impeller in response to determining that left ventricular pressure of the subject has decreased.

[0129] In some applications, the device further comprises:

[0130] a magnet, the impeller being coupled to the magnet such that axial movement of the impeller causes axial movement of the magnet;

[0131] a sensor configured to detect magnetic flux generated by the magnet and to generate a sensor signal in response thereto; and

[0132] A computer processor is configured to receive the sensor signal and to generate an output in response thereto.

[0133] 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 vary a rotation rate of the impeller based at least in part on the sensor signal.

[0134] In some applications, a computer processor is configured to:

[0135] determining a left ventricular pressure of the subject based at least in part on the sensor signal, and

[0136] The rotational rate of the impeller is varied based at least in part on the determined left ventricular pressure.

[0137] In some applications, the computer processor is configured to reduce the rotational rate of the impeller in response to determining that left ventricular pressure of the subject has decreased.

[0138] 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 cyclical changes in the pressure differential between the first location and the second location. In some applications, the impeller is configured to pump blood from the 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 cyclical changes in the pressure differential between the left ventricle and the aorta. In some applications, the impeller is configured to pump blood from the subject's right ventricle to the subject's pulmonary artery, and the impeller is configured to move axially back and forth relative to the frame in response to cyclical changes in the pressure differential between the right ventricle and the pulmonary artery. In some applications, the impeller is configured to pump blood from the subject's right atrium to the subject's right ventricle, and the impeller is configured to move axially back and forth relative to the frame in response to cyclical changes in the pressure differential between the right atrium and the right ventricle. In some applications, the impeller is configured to pump blood from the vena cava of the subject to the right ventricle of the subject, and the impeller is configured to move axially back and forth relative to the frame in response to cyclical changes in the pressure differential between the vena cava and the right ventricle. In some applications, the impeller is configured to pump blood from the right atrium of the subject to the pulmonary artery of the subject, and the impeller is configured to move axially back and forth relative to the frame in response to cyclical changes in the pressure differential between the right atrium and the pulmonary artery. In some applications, the impeller is configured to pump blood from the vena cava of the subject to the pulmonary artery of the subject, and the impeller is configured to move axially back and forth relative to the frame in response to cyclical changes in the pressure differential between the vena cava and the pulmonary artery.

[0139] In some applications, the device further comprises:

[0140] a motor configured to drive the impeller by rotating the impeller in a given rotational direction to pump blood through the subject's body;

[0141] an axial shaft to which the impeller is coupled; and

[0142] a drive cable configured to extend from outside the subject's body to the axial axis, 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 arranged in a coiled configuration such that in response to rotation of the drive cable in the given rotational direction, the plurality of wires arranged in the coiled configuration at least partially unwind, causing the portion of the drive cable to axially shorten.

[0143] In some applications:

[0144] The impeller includes a proximal bushing and a distal bushing;

[0145] The frame includes a proximal bearing and a distal bearing;

[0146] The apparatus further comprises an axial shaft, the axial shaft:

[0147] passing through the proximal and distal bearings defined by the frame and the proximal and distal bushings of the impeller,

[0148] at least one of the proximal bushing and the distal bushing coupled to the impeller such that the at least one bushing is retained in an axially fixed position relative to the axial shaft,

[0149] The impeller is not held in an axially fixed position relative to the proximal and distal bearings such that the impeller causes axial back-and-forth movement of the axial shaft relative to the proximal and distal bearings of the frame.

[0150] In some applications, the axial shaft is configured to clean interfaces between the axial shaft and the proximal and distal bearings of the frame by performing the axial back-and-forth movement relative to the proximal and distal bearings of the frame. In some applications, the axial shaft is configured to reduce heat buildup at interfaces between the axial shaft and the proximal and distal bearings of the frame by performing the axial back-and-forth movement relative to the proximal and distal bearings of the frame, relative to a situation where the axial shaft is not performing the axial back-and-forth movement relative to the proximal and distal bearings of the frame.

[0151] According to some applications of the present invention, the following inventive concepts are also provided:

[0152] Inventive concept 1. A device, comprising:

[0153] An impeller, comprising:

[0154] at least one helical elongated element;

[0155] a spring disposed within the helical elongated element and along the axis about which the helical elongated element is wound;

[0156] a film of material supported between the helical elongate element and the spring; and

[0157] At least one flexible elongate element extends from the spring to the helical elongate element and is configured to hold the helical elongate element within a given distance from the spring, the at least one flexible elongate element being selected from the group consisting of: a string and a wire.

[0158] Inventive Concept 2. The apparatus of Inventive Concept 1, wherein the impeller is configured such that in the non-radially constrained configuration of the impeller, the outer diameter of the impeller at a location where the outer diameter is at its maximum is less than 8 mm.

[0159] Inventive Concept 3. The device of Inventive Concept 1, wherein the at least one helical elongate element comprises a plurality of helical elongate elements, and wherein the at least one flexible elongate element extends from a spring to each of the helical elongate elements.

[0160] Inventive Concept 4. The device of any one of Inventive Concepts 1-3, wherein the impeller is configured to pump blood through the body of the subject.

[0161] Inventive Concept 5. The device of Inventive Concept 4, wherein the impeller is configured to be placed in a blood vessel of the subject.

[0162] Inventive Concept 6. The apparatus of Inventive Concept 4, wherein the impeller is configured to be placed in a cardiac chamber of the subject.

[0163] Inventive Concept 7. The apparatus of Inventive Concept 4, wherein the impeller is configured to pump blood from the subject's left ventricle to the subject's aorta.

[0164] Inventive Concept 8. The apparatus of Inventive Concept 4, wherein the impeller is configured to pump blood from the right ventricle of the subject to the pulmonary artery of the subject.

[0165] Inventive concept 9. A method comprising:

[0166] An impeller is placed into the subject's body, comprising:

[0167] at least one helical elongated element;

[0168] a spring disposed within the helical elongated element and along the axis about which the helical elongated element is wound;

[0169] a membrane of material supported between the helical elongate member and the spring; and

[0170] at least one flexible elongate member extending from the spring to the helical elongate member, selected from the group consisting of: a string and a wire; and

[0171] Blood is pumped through the subject's body by rotating the impeller, with the flexible elongate member holding the helical elongate member within a given distance from the spring during rotation of the impeller.

[0172] Inventive concept 10. A device comprising:

[0173] A blood pump comprising:

[0174] an impeller configured to be placed within a cardiac chamber of a subject;

[0175] a frame configured to be disposed around the impeller; and

[0176] a motor configured to drive the impeller by rotating the impeller to pump blood from a cardiac chamber of the subject to a blood vessel,

[0177] The impeller is configured to move axially relative to the frame in response to cyclical changes in a pressure differential between the heart chamber and the blood vessel.

[0178] Inventive concept 11. A method, comprising:

[0179] placing an impeller of a blood pump within a heart chamber of the subject, with a frame disposed around the impeller; and

[0180] The impeller is driven by rotating the impeller to pump blood from the heart chambers to the blood vessels of the subject,

[0181] Positioning of the impeller within the cardiac chamber permits axial movement of the impeller relative to the frame in response to cyclical changes in the pressure differential between the cardiac chamber and the blood vessels.

[0182] Inventive concept 12. A device comprising:

[0183] A blood pump comprising:

[0184] an impeller configured to be placed within a first blood vessel of a subject;

[0185] a frame configured to be disposed around the impeller; and

[0186] a motor configured to drive the impeller by rotating the impeller to pump blood from the first blood vessel to the second blood vessel of the subject,

[0187] The impeller is configured to move axially relative to the frame in response to cyclical changes in a pressure differential between the first blood vessel and the second blood vessel.

[0188] Inventive concept 13. A method comprising:

[0189] placing an impeller of a blood pump within a first blood vessel of the subject, with a frame disposed around the impeller; and

[0190] driving an impeller by rotating the impeller to pump blood from a first blood vessel to a second blood vessel of the subject,

[0191] Positioning the impeller within the first blood vessel permits axial movement of the impeller relative to the frame in response to cyclic changes in a pressure differential between the heart chamber and the blood vessel.

[0192] Inventive concept 14. A device comprising:

[0193] A blood pump comprising:

[0194] an impeller configured to be placed within the body of a subject and configured to rotate to pump blood through the body of the subject;

[0195] a frame configured to be disposed around the impeller; and

[0196] One or more thrust bearings configured to be disposed externally of the subject's body, wherein opposition to thrust generated by rotation of the impeller is provided solely by the one or more thrust bearings disposed externally of the subject's body.

[0197] Inventive concept 15. A method comprising:

[0198] placing an impeller of a blood pump within a body of a subject, with a frame disposed around the impeller; and

[0199] The impeller is driven by rotating it to pump blood through the subject's body, with opposition to thrust generated by the rotation of the impeller provided solely by one or more thrust bearings disposed externally to the subject's body.

[0200] Inventive concept 16. A device comprising:

[0201] blood pump tubing;

[0202] a blood pump configured to be disposed within the blood pump tube and configured to pump blood through the blood pump tube;

[0203] at least one blood pressure measurement tube defining an opening at a distal end thereof and configured to extend to at least an exterior surface of the blood pump tubing such that the opening at the distal end of the blood pressure measurement tube is in direct fluid communication with a blood flow of the subject external to the blood pump tubing; and

[0204] At least one pressure sensor is configured to measure blood flow pressure of the subject outside the blood pump tubing by measuring blood pressure within the blood pressure measurement tubing.

[0205] Inventive Concept 17. The apparatus according to Inventive Concept 16, wherein the blood pump comprises an impeller configured to pump blood through the blood pump tube by rotating.

[0206] Inventive Concept 18. The apparatus according to Inventive Concept 16, wherein the blood pressure measurement tube is configured to pass from a proximal end of the blood pump tube along an outer surface of the blood pump tube to an opening at a distal end of the blood pressure measurement tube.

[0207] Inventive Concept 19. The device according to Inventive Concept 16 further includes at least one computer processor, which is configured to receive an indication of the blood pressure measured in the blood pressure measurement tube and is configured to control the pumping of blood through the blood pump in response to the blood pressure measured in the blood pump tube.

[0208] Inventive concept 20. An apparatus according to any one of inventive concepts 16-19, wherein the at least one blood pressure measuring tube includes at least one left ventricular blood pressure measuring tube, which is configured to extend to the outer surface of the blood pump tube at a position near the blood pump along the tube configured to be within the left ventricle of the subject, and wherein the pressure sensor is configured to measure the left ventricular pressure of the subject by measuring the blood pressure within the left ventricular blood pressure measuring tube.

[0209] Inventive concept 21. An apparatus according to inventive concept 20, wherein at least one blood pressure measuring tube includes two or more left ventricular blood pressure measuring tubes, which are configured to extend to the outer surface of the blood pump tube at a position close to the blood pump along the blood pump tube configured to be within the left ventricle of the subject, and wherein at least one pressure sensor is configured to measure the left ventricular pressure of the subject by measuring the blood pressure within at least one of the left ventricular blood pressure measuring tubes.

[0210] Inventive concept 22. The device according to inventive concept 21,

[0211] wherein at least one pressure sensor is configured to measure blood pressure within each of the two or more left ventricular blood pressure measurement tubes,

[0212] The device also includes at least one computer processor configured to:

[0213] receiving an indication of a blood pressure measured within each of two or more left ventricular blood pressure measurement tubes,

[0214] In response thereto, it is determined that the opening of one of the two or more left ventricular blood pressure measuring tubes is blocked, and

[0215] In response thereto, the subject's left ventricular pressure is determined based on the blood pressure measured within a different one of the two or more left ventricular blood pressure measurement tubes.

[0216] Inventive concept 23. An apparatus according to inventive concept 20, wherein the at least one blood pressure measuring tube further comprises at least one aortic blood pressure measuring tube, the aortic blood pressure measuring tube being configured to extend to the outer surface of the blood pump tube at a position along the blood pump tube configured to be within the subject's aorta, and wherein the pressure sensor is configured to measure the subject's aortic pressure by measuring the blood pressure within the aortic blood pressure measuring tube.

[0217] Inventive concept 24. An apparatus according to inventive concept 23, wherein at least one aortic blood pressure measuring tube includes two or more aortic blood pressure measuring tubes, the aortic blood pressure measuring tubes being configured to extend to the outer surface of the blood pump tube at a position along the blood pump tube configured to be within the subject's aorta, and wherein at least one pressure sensor is configured to measure the subject's aortic pressure by measuring the blood pressure within the at least one aortic blood pressure measuring tube.

[0218] Inventive concept 25. An apparatus according to any one of inventive concepts 16-19, wherein the at least one blood pressure measuring tube includes at least one aortic blood pressure measuring tube, which is configured to extend to the outer surface of the blood pump tube at a position along the blood pump tube configured to be within the subject's aorta, and wherein the pressure sensor is configured to measure the subject's aortic pressure by measuring the blood pressure within the aortic blood pressure measuring tube.

[0219] Inventive concept 26. A device according to inventive concept 25, wherein at least one aortic blood pressure measurement tube includes two or more aortic blood pressure measurement tubes, which are configured to extend to the outer surface of the blood pump tube at a position along the blood pump tube configured to be within the subject's aorta, and wherein at least one pressure sensor is configured to measure the subject's aortic pressure by measuring the blood pressure within the at least one aortic blood pressure measurement tube.

[0220] Inventive concept 27. The device according to inventive concept 26,

[0221] wherein at least one pressure sensor is configured to measure blood pressure in each of the two or more aortic blood pressure measurement tubes,

[0222] The device also includes at least one computer processor configured to:

[0223] receiving an indication of a blood pressure measured within each of two or more aortic blood pressure measurement tubes,

[0224] In response thereto, it is determined that the opening of one of the two or more aortic blood pressure measurement tubes is blocked, and

[0225] In response thereto, the subject's aortic pressure is determined based on the blood pressure measured within a different one of the two or more aortic blood pressure measurement tubes.

[0226] Inventive Concept 28. The device according to any one of Inventive Concepts 16-19, wherein the blood pressure measurement tube is configured to extend from outside the subject's body to an opening at the distal end, and wherein the at least one pressure sensor is configured to be disposed outside the subject's body.

[0227] Inventive Concept 29. The apparatus of Inventive Concept 28, wherein the blood pump comprises an impeller disposed on an axial shaft, the impeller configured to pump blood from the left ventricle to the aorta by rotation, wherein the apparatus further comprises:

[0228] a motor disposed external to the subject's body and configured to rotate the impeller;

[0229] 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

[0230] an outer tube configured to extend from outside the subject's body into the blood pump tube,

[0231] The drive cable and the blood pressure measurement tube are configured to be arranged inside the outer tube.

[0232] Inventive concept 30. The device according to inventive concept 29,

[0233] wherein the at least one blood pressure measurement tube includes at least one left ventricular blood pressure measurement tube configured to extend to an outer surface of the blood pump tube at a location along the blood pump tube configured to be within the left ventricle of the subject, near 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;

[0234] The apparatus further includes 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 an outer surface of an 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;

[0235] The at least one pressure sensor is further configured to measure the subject's aortic pressure by measuring blood pressure within the aortic blood pressure measurement tube.

[0236] Inventive concept 31. The device according to inventive concept 29,

[0237] wherein the at least one blood pressure measurement tube includes at least one left ventricular blood pressure measurement tube configured to extend to an outer surface of the blood pump tube at a location along the blood pump tube configured to be within the left ventricle of the subject, near 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;

[0238] The apparatus further includes 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 tubing 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;

[0239] The at least one pressure sensor is further configured to measure the aortic pressure of the subject by measuring the blood pressure in the aortic blood pressure measuring tube.

[0240] Inventive concept 32. An apparatus according to inventive concept 29, wherein the outer tube defines a groove in a portion of the outer surface of the outer tube configured to be disposed within the blood pump tube, and wherein, during insertion of the ventricular assist device into the body of a subject, the portion of the blood pressure measuring 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 measuring tube does not protrude from the outer surface of the outer tube.

[0241] Inventive Concept 33. The device according to Inventive Concept 28, wherein the diameter of the blood pressure measuring tube at least in a distal portion of the blood pressure measuring tube is less than 0.5 mm.

[0242] Inventive Concept 34. The device according to Inventive Concept 33, wherein the diameter of the blood pressure measuring tube at least in the distal portion of the blood pressure measuring tube is greater than 0.2 mm.

[0243] Inventive concept 35. A method comprising:

[0244] Placed into the subject's body:

[0245] Blood pump tubing,

[0246] a blood pump disposed within the blood pump tube, and

[0247] at least one blood pressure measurement tube defining an opening at a distal end thereof and extending to at least an outer surface of the blood pump tubing such that the opening at the distal end of the blood pressure measurement tube is in direct fluid communication with a blood flow of the subject external to the blood pump tubing;

[0248] pumping blood through the blood pump tubing using a blood pump; and

[0249] The blood pressure of the subject outside the blood pump tube is measured by measuring the blood pressure inside the blood pressure measuring tube.

[0250] Inventive concept 36. A device comprising:

[0251] A blood pump comprising:

[0252] Tube;

[0253] an impeller configured to be disposed within the tube and configured to rotate to pump blood through the tube;

[0254] a frame disposed around the impeller; and

[0255] a stator configured to reduce rotation of the blood flow generated by the rotation of the impeller

[0256] The stator comprises:

[0257] a plurality of struts integral with the frame and curved; and

[0258] A flexible material is coupled to the curved struts such that a plurality of curved protrusions are formed.

[0259] Inventive Concept 37. The apparatus according to Inventive Concept 36, wherein a curvature of the curved protrusion is opposite to a rotation direction of the impeller.

[0260] Inventive Concept 38. The device according to Inventive Concept 36, wherein the curvature of the curved protrusion is such that the curved protrusion gradually becomes closer to being parallel to the longitudinal axis of the frame from the distal end of the curved protrusion to the proximal end of the curved protrusion.

[0261] Inventive concept 39. The device of inventive concept 36, wherein the flexible material is shaped to define a lumen therethrough.

[0262] Inventive concept 40. A method comprising:

[0263] A blood pump is placed into the subject's body, the blood pump comprising:

[0264] Tube,

[0265] an impeller configured to be disposed within the tube,

[0266] a frame disposed around the impeller, and

[0267] a stator comprising a plurality of pillars integral with the frame and curved, and a flexible material coupled to the curved pillars so as to form a plurality of curved protrusions; and

[0268] The impeller is used to pump blood through the tube, and the stator reduces the rotational flow component from the blood flow generated by the rotation of the impeller.

[0269] Inventive concept 41. A device comprising:

[0270] A ventricular assist device, which includes:

[0271] Axial shaft;

[0272] an impeller disposed on an axial shaft and configured to be placed in a left ventricle of a subject;

[0273] a motor configured to be disposed externally to the subject's body and configured to drive the impeller by rotating the impeller to pump blood from the left ventricle to the subject's aorta;

[0274] a drive cable configured to extend from outside 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 at least partially disposed within the aortic arch of the subject and a second portion configured to be at least partially disposed within the descending aorta of the subject,

[0275] The first portion of the drive cable includes a first number of wires arranged in a coiled configuration, and the second portion of the drive cable includes a second number of wires arranged in a coiled configuration, the first number being lower than the second number.

[0276] Inventive Concept 42. The device according to Inventive Concept 41, wherein the length of the first portion of the drive cable is between 20 cm and 40 cm.

[0277] Inventive Concept 43. The device according to Inventive Concept 41, wherein the length of the second portion of the drive cable is between 60 cm and 100 cm.

[0278] Inventive Concept 44. The device of Inventive Concept 41, wherein the first portion of the drive cables comprises between 4 and 8 wires arranged in a coiled configuration, and the second portion of the drive cables comprises between 8 and 12 wires arranged in a coiled configuration.

[0279] Inventive concept 45. A device comprising:

[0280] A blood pump comprising:

[0281] Axial shaft;

[0282] an impeller disposed on the axial shaft;

[0283] a motor configured to be disposed externally to the subject's body and configured to drive the impeller by rotating the impeller to pump blood through the subject's body;

[0284] a drive cable configured to extend from outside 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 at least partially disposed within a curved portion of the subject's vasculature and a second portion configured to be at least partially disposed within a straight portion of the subject's vasculature,

[0285] The first portion of the drive cable includes a first number of wires arranged in a coiled configuration, and the second portion of the drive cable includes a second number of wires arranged in a coiled configuration, the first number being lower than the second number.

[0286] Inventive concept 46. A device comprising:

[0287] A blood pump comprising:

[0288] Axial shaft;

[0289] an impeller disposed on the axial shaft;

[0290] a motor configured to be disposed outside the body of the subject and configured to drive the impeller by rotating the impeller in a given rotational direction to pump blood from a distal end of the impeller to a proximal end of the impeller;

[0291] 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 rotating,

[0292] At least a portion of the drive cable includes a plurality of wires arranged in a coiled configuration such that in response to rotation of the drive cable in a given rotational direction, the plurality of wires arranged in the coiled configuration at least partially unwinds, causing the portion of the drive cable to axially shorten.

[0293] Inventive Concept 47. The device 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 perform axial back-and-forth motion in response to periodic changes in a pressure differential between the first location and the second location.

[0294] Inventive concept 48. A method comprising:

[0295] A blood pump is placed into the subject's body, the blood pump comprising:

[0296] Axial shaft,

[0297] an impeller disposed on the axial shaft, and

[0298] a drive cable extending from outside the subject's body to the axial shaft; and

[0299] The impeller is driven to pump blood from a distal end of the impeller to a proximal end of the impeller by imparting rotational motion to the impeller via a drive cable, at least a portion of the drive cable comprising a plurality of wires arranged in a coiled configuration, such that in response to rotation of the drive cable in a given rotational direction, the plurality of wires arranged in the coiled configuration at least partially unwind, causing the portion of the drive cable to axially shorten.

[0300] Inventive concept 49. A device comprising:

[0301] A blood pump comprising:

[0302] Axial shaft;

[0303] an impeller disposed on the axial shaft;

[0304] a motor configured to be disposed outside the body of the subject and configured to drive the impeller to pump blood in a proximal direction by rotating the impeller in a given rotational direction;

[0305] a drive cable configured to extend from a proximal end of the drive cable disposed outside the body of the subject to a distal end of the drive cable, the drive cable coupled to the axial shaft, the drive cable configured to transmit rotational motion from the motor to the impeller by rotation;

[0306] an outer tube disposed around the drive cable; and

[0307] a fluid disposed between the outer tube and the drive cable,

[0308] At least a portion of the drive cable includes a plurality of wires arranged in a coiled configuration such that, in response to rotation of the drive cable in a given rotational direction, the plurality of wires is configured to pump fluid toward a proximal end of the drive cable.

[0309] Inventive concept 50. A method comprising:

[0310] A blood pump is placed into the subject's body, the blood pump comprising:

[0311] Axial shaft,

[0312] an impeller, which is arranged on an axial shaft,

[0313] a drive cable extending from outside the subject's body to the axial shaft,

[0314] an outer tube disposed around the drive cable, and

[0315] a fluid disposed between the drive cable and the outer tube; and

[0316] The impeller is driven to pump blood from a distal end of the impeller to a proximal end of the impeller by imparting rotational motion to the impeller via a drive cable, at least a portion of the drive cable comprising a plurality of wires arranged in a coiled configuration such that in response to rotation of the drive cable in a given rotational direction, the plurality of wires are configured to pump fluid toward the proximal end of the drive cable.

[0317] Inventive concept 51. A device comprising:

[0318] A blood pump comprising:

[0319] impeller;

[0320] a motor configured to drive the impeller to pump blood by rotating the impeller, the impeller being configured to move axially in response to a change in a pressure differential against which the impeller pumps blood;

[0321] a magnet, the impeller being coupled to the magnet such that axial movement of the impeller causes axial movement of the magnet;

[0322] a sensor configured to detect magnetic flux generated by the magnet and to generate a sensor signal in response thereto; and

[0323] A computer processor is configured to receive the sensor signal and to generate an output in response thereto.

[0324] Inventive concept 52. The apparatus of inventive concept 51, wherein the computer processor is configured to generate an output indicative of a cardiac cycle of the subject in response to receiving the sensor signal.

[0325] Inventive concept 53. The apparatus of inventive concept 51, wherein the computer processor is configured to determine the left ventricular pressure of the subject based at least in part on the sensor signal.

[0326] Inventive Concept 54. The apparatus of any of Inventive Concepts 51-53, wherein the computer processor is configured to vary the rotational rate of the impeller based at least in part on the sensor signal.

[0327] Inventive concept 55. The device according to inventive concept 54, wherein the computer processor is configured to:

[0328] determining a left ventricular pressure of the subject based at least in part on the sensor signal, and

[0329] The rotational rate of the impeller is varied based at least in part on the determined left ventricular pressure.

[0330] Inventive concept 56. The apparatus of inventive concept 55, wherein the computer processor is configured to reduce the rotational rate of the impeller in response to determining that the left ventricular pressure of the subject has decreased.

[0331] Inventive concept 57. A device comprising:

[0332] A blood pump comprising:

[0333] impeller;

[0334] a motor configured to drive the impeller to pump blood by rotating the impeller, the impeller being configured to move axially in response to a change in a pressure differential against which the impeller pumps blood;

[0335] a sensor configured to detect an indication of axial movement of the impeller and configured to generate a sensor signal in response thereto; and

[0336] A computer processor is configured to receive the sensor signal and to generate an output in response thereto.

[0337] Inventive concept 58. A method comprising:

[0338] placing a blood pump into a body of a subject, the blood pump comprising an impeller;

[0339] driving the impeller to pump blood by rotating the impeller, the impeller being configured to move axially in response to changes in a pressure differential against which the impeller pumps blood;

[0340] detecting an indication of axial movement of the impeller and generating a sensor signal in response thereto; and

[0341] A sensor signal is received and an output is generated in response thereto.

[0342] Inventive concept 59. A device comprising:

[0343] A blood pump comprising:

[0344] impeller;

[0345] frame,

[0346] The impeller and the frame are configured to be inserted into a body of a subject such that the frame is disposed around the impeller within the body of the subject; and

[0347] A computer processor is configured to drive the motor unit to simultaneously (a) drive the impeller by driving the impeller to rotate to pump blood through the subject's body, and (b) drive the impeller to move axially in a back-and-forth motion within the frame.

[0348] Inventive concept 60. A method comprising:

[0349] placing a blood pump comprising an impeller and a frame into a body of a subject such that the frame is disposed around the impeller; and

[0350] at the same time:

[0351] driving an impeller to pump blood through the subject's body by driving the impeller to rotate;

[0352] as well as

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

[0354] Inventive concept 61. A device comprising:

[0355] A blood pump comprising:

[0356] Axial shaft;

[0357] an impeller disposed on an axial shaft and configured to be placed in a left ventricle of a subject;

[0358] a motor configured to be disposed externally to 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 being configured to remain stationary during rotation of the drive cable; and

[0361] A plurality of ball bearings are configured to be disposed between the drive cable and the tube 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 bearing is 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 an aortic arch of the subject.

[0363] Inventive concept 63. A device 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 externally to the subject's body;

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

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

[0370] A driven magnet is coupled to the drive cable and disposed between the drive magnets such that there is an axial overlap between the drive magnet 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 being 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] A blood pump is placed into the subject's body, the blood pump comprising:

[0373] Axial shaft,

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

[0375] a drive cable extending from outside the subject's body to the axial shaft; and

[0376] The impeller is driven to rotate by:

[0377] using a motor to rotate exactly two drive magnets disposed in a drive magnet housing coupled to the motor,

[0378] The drive magnet is configured to thereby drive a driven magnet in rotation, which is coupled to the drive cable and disposed between the drive magnets such that there is an axial overlap between the drive magnet and the driven magnet, the driven magnet defining a single north pole and a single south pole separated along the axial length of the driven magnet.

[0379] Inventive Concept 65. A device comprising:

[0380] A blood pump comprising:

[0381] Axial shaft;

[0382] an impeller disposed on the axial shaft and configured to be placed within a body of a subject;

[0383] a motor configured to be disposed externally to the subject's body;

[0384] a drive cable configured to extend from outside the subject's body to the axial axis;

[0385] exactly two driven magnets disposed in a driven magnet housing coupled to the drive cable; and

[0386] a drive magnet coupled to the motor and disposed between the driven magnets such that there is an axial overlap between the driven magnets and the drive magnets, the drive magnet defining a single north pole and a single south pole separated along an axial length of the drive magnet, the motor being configured to rotate the driven magnets by rotating the drive magnets so as to rotate the drive cable to impart rotational motion to the impeller.

[0387] Inventive concept 66. A method comprising:

[0388] A blood pump is placed into the subject's body, the blood pump comprising:

[0389] Axial shaft,

[0390] an impeller disposed on the axial shaft, and

[0391] A drive cable extends from the exterior of the subject's body to the axial shaft and drives the impeller to rotate by:

[0392] 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,

[0393] The driving magnet is configured to thereby drive a driven magnet in rotation, the driven magnet comprising exactly two driven magnets disposed in a driven magnet housing coupled to the drive cable and disposed around the driving magnet.

[0394] Inventive concept 67. A device comprising:

[0395] A blood pump comprising:

[0396] Axial shaft;

[0397] an impeller disposed on the axial shaft and configured to be placed within a body of a subject;

[0398] a motor configured to be disposed outside the body of the subject and configured to drive the impeller to pump blood by rotating the impeller in a given rotational direction;

[0399] a drive cable configured to extend from outside the body of the subject to the axial shaft, the drive cable configured to impart rotational motion from the motor to the impeller by rotation, and the drive cable comprising a plurality of wires arranged in a coiled configuration and coupled to the axial shaft,

[0400] The axial shaft defines a groove at an interface between the drive cable and the axial shaft, the groove being configured such that stress generated by the wire at the interface is distributed over a radius of the groove.

[0401] Inventive concept 68. A device comprising:

[0402] A blood pump comprising:

[0403] Axial shaft;

[0404] an impeller disposed on the axial shaft and configured to be placed within a body of a subject;

[0405] a motor configured to be disposed outside the body of the subject and configured to drive the impeller to pump blood by rotating the impeller in a given rotational direction;

[0406] a drive cable configured to extend from outside the subject's body to the axial shaft, the drive cable configured to impart rotational motion from the motor to the impeller by rotation, and the drive cable comprising a plurality of wires arranged in a coiled configuration and coupled to the axial shaft,

[0407] The coiled wire is shaped such that as the coiled wire approaches the interface between the drive cable and the axial shaft, the pitch of the wire increases, reducing stress at the location where the wire of the drive cable is coupled to the axial shaft relative to if the pitch of the wire had not increased.

[0408] Inventive Concept 69. A device comprising:

[0409] A blood pump comprising:

[0410] Axial shaft;

[0411] an impeller disposed on the axial shaft and configured to be placed within a body of a subject;

[0412] a motor configured to be disposed outside the body of the subject and configured to drive the impeller to pump blood by rotating the impeller in a given rotational direction;

[0413] 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 rotating,

[0414] the drive cable comprising 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 the coiled configuration, the first number being less than the second number; and

[0415] an interface component via which the first and second portions of the drive cable are coupled to each other,

[0416] The interface member defines a groove at an interface between at least one of the drive cable portions and the interface member, the groove being configured such that stress generated by the wire at the interface is distributed over a radius of the groove.

[0417] Inventive Concept 70. A device comprising:

[0418] A blood pump comprising:

[0419] Axial shaft;

[0420] an impeller disposed on the axial shaft and configured to be placed within a body of a subject;

[0421] a motor configured to be disposed outside the body of the subject and configured to drive the impeller to pump blood by rotating the impeller in a given rotational direction;

[0422] 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 rotating,

[0423] the drive cable comprising 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 the coiled configuration, the first number being less than the second number; and

[0424] an interface component via which the first and second portions of the drive cable are coupled to each other,

[0425] The coiled wire of at least one of the portions of the drive cable is shaped such that as the coiled wire approaches the interface component, the pitch of the wire increases such that stress at the location where the wire couples to the interface component is reduced relative to if the pitch of the wire had not increased.

[0426] Inventive concept 71. A device comprising:

[0427] A ventricular assist device, which includes:

[0428] a tube configured to pass through an aortic valve of a subject such that a proximal portion of the tube is disposed within the aorta of the subject and a distal portion of the tube is disposed within 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;

[0429] 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

[0430] A radially expandable atraumatic distal tip portion is configured to be disposed distally within the left ventricle of a subject relative to one or more blood inlet openings, the distal tip portion being configured to be inserted into the left ventricle in a radially constrained configuration and to assume a non-radially constrained configuration within the left ventricle of the subject, wherein at least the radially expandable portion of the distal tip portion is radially expanded relative to the radially constrained configuration of the distal tip portion.

[0431] Inventive concept 72. The device according to inventive concept 71, wherein the distal tip portion comprises a braided shape memory alloy at least partially covered with a blood impermeable material.

[0432] Inventive concept 73. The device according to inventive concept 71, wherein the distal tip portion is configured such that in a 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 the ventricular septum within the left ventricle.

[0433] Inventive concept 74. The device of inventive concept 71, wherein the distal tip portion is configured such that in a 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 the chordae tendineae within the left ventricle.

[0434] Inventive concept 75. The device of inventive concept 71, wherein the distal tip portion is configured such that in a 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 a papillary muscle within the left ventricle.

[0435] Inventive concept 76. The device of inventive concept 71, wherein the distal tip portion is configured such that in a 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 the apex of the left ventricle.

[0436] Inventive concept 77. A device according to inventive concept 71, wherein the distal tip portion is configured such that in a non-radially constrained configuration of the distal tip portion, the radially expandable portion of the distal tip portion three-dimensionally separates the one or more blood inlet openings from the internal structure of the left ventricle.

[0437] Inventive Concept 78. The device of Inventive Concept 71, wherein the distal tip portion is configured such that in a 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.

[0438] Inventive concept 79. The apparatus according to any one of inventive concepts 71-78, wherein:

[0439] 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 a longitudinal direction toward a distal end of the distal tip portion;

[0440] The ventricular assist device is configured to be inserted into the body of the subject via a puncture in the body of the subject, and

[0441] 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.

[0442] Inventive concept 80. The device according to any of inventive concepts 71-78, wherein the distal tip portion is configured such that in a non-radially constrained configuration of the distal tip portion, a distal end of the distal tip portion is enclosed within the radially expandable portion of the distal tip portion.

[0443] Inventive Concept 81. The device 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 tendineae of the left ventricle by the distal end of the distal tip portion being enclosed within the radially expandable portion of the distal tip.

[0444] Inventive concept 82. The device 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 enclosing the distal end of the distal tip portion within the radially expandable portion of the distal tip portion.

[0445] Inventive Concept 83. The device 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 eversion of the distal end of the distal tip portion.

[0446] Inventive concept 84. A device 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 retracting the distal end of the distal tip portion proximally so that the distal end is disposed within the radially expandable portion of the distal tip portion.

[0447] Inventive Concept 85. A device comprising:

[0448] A ventricular assist device configured to be inserted into a subject's body via a puncture, the ventricular assist device comprising:

[0449] a tube configured to pass through an aortic valve of a subject such that a proximal portion of the tube is disposed within the aorta of the subject and a distal portion of the tube is disposed within 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;

[0450] 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

[0451] a distal tip portion configured to:

[0452] having 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 being configured to act as a dilator by enlarging the puncture during insertion of the ventricular assist device into the body of a subject, and

[0453] The distal tip region has a non-radially constrained configuration, the distal tip region being configured to assume the non-radially constrained configuration within the left ventricle of the subject, wherein the radially expandable portion of the distal tip portion is configured to be atraumatic and to separate the one or more blood inlet openings from the internal structure of the left ventricle of the subject.

[0454] Inventive concept 86. A method comprising:

[0455] Operate the blood pump, which includes:

[0456] Axial shaft,

[0457] an impeller disposed on an axial shaft and positioned in a left ventricle of the subject;

[0458] a motor disposed external to the subject's body and configured to drive the impeller to rotate,

[0459] a drive cable extending from outside the subject's body through the subject's aortic arch to the axial shaft and configured to impart rotational motion from the motor to the impeller by rotation, and

[0460] a tube within which the drive cable is disposed, the tube being configured to remain stationary during rotation of the drive cable; and

[0461] While the blood pump is operating, fluid is pumped into the space between the drive cable and the tube such that the fluid fills the space between the drive cable and the tube but the fluid is not released into the subject's bloodstream.

[0462] Inventive concept 87. A method comprising:

[0463] Operate the blood pump, which includes:

[0464] Axial shaft,

[0465] an impeller disposed on an axial shaft and positioned in a left ventricle of a subject,

[0466] a motor disposed external to the subject's body and configured to drive the impeller to rotate,

[0467] a drive cable extending from outside the subject's body through the subject's aortic arch to the axial shaft and configured to impart rotational motion from the motor to the impeller by rotation, and

[0468] a tube within which the drive cable is disposed, the tube being configured to remain stationary during rotation of the drive cable;

[0469] prior to operating the blood pump, pumping fluid into the space between the drive cable and the tube such that the fluid fills the space between the drive cable and the tube but does not release the fluid into the subject's bloodstream; and

[0470] During operation of the blood pump, fluid is retained in the space between the drive cable and the tubing.

[0471] Inventive Concept 88. A device comprising:

[0472] A left ventricular assist device configured to assist left ventricular function of a subject, the left ventricular assist device comprising:

[0473] a tube configured to pass through an aortic valve of the subject such that a proximal portion of the tube is at least partially disposed within the ascending aorta of the subject and a distal portion of the tube is at least partially disposed within the left ventricle of the subject;

[0474] a frame disposed within the distal portion of the tube, the frame being configured to maintain the distal portion of the tube in an open state,

[0475] The frame is not disposed within the proximal portion of the tube, and the proximal portion of the tube is thus configured to collapse inwardly in response to a pressure external to the proximal portion of the tube exceeding a pressure within the proximal portion of the tube;

[0476] a pump disposed within the frame and configured to pump blood from the subject's left ventricle to the subject's aorta through the tube such that the proximal portion of the tube remains in an open state when a blood pressure generated by the blood pump within the proximal portion of the tube exceeds the subject's aortic pressure outside the proximal portion of the tube; and

[0477] A plurality of elongated commissure elements are disposed within the proximal portion of the tube such that when the proximal portion of the tube collapses inwardly, corresponding portions of the circumference of the tube form cusps that contact one another.

[0478] Inventive concept 89. The device according to inventive concept 88 further includes a computer processor configured to control the pumping of blood by the blood pump through the tube so that the blood pressure generated by the blood pump in the tube exceeds the subject's systolic aortic pressure and is less than the subject's diastolic aortic pressure.

[0479] Inventive Concept 90. The apparatus of Inventive Concept 88, further comprising a pressure sensor configured to measure the subject's aortic blood pressure, and wherein the computer processor is configured to receive an indication of the measured aortic blood pressure and is configured to control the pumping of blood by the blood pump through the tube in response to the measured aortic blood pressure.

[0480] Inventive concept 91. The apparatus according to inventive concept 88 further comprising a pressure sensor configured to measure the left ventricular blood pressure of the subject, and wherein the computer processor is configured to receive an indication of the measured left ventricular blood pressure and is configured to control the pumping of blood by the blood pump through the tube in response to the measured left ventricular blood pressure.

[0481] Inventive Concept 92. An apparatus for use with a delivery device, the apparatus comprising:

[0482] impeller;

[0483] a frame, which is arranged around the impeller,

[0484] the impeller and frame are configured to be inserted into a blood vessel of a subject via a 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

[0485] A coupling element includes a first portion disposed on the impeller and a second portion disposed on the frame and configured to engage with the first portion, the coupling element being configured to facilitate radial contraction of the impeller by retaining an end of the impeller so that the impeller can be axially extended without radially contracting the frame.

[0486] Inventive Concept 93. A device comprising:

[0487] Blood pump tubing:

[0488] an impeller configured to be disposed within the blood pump tube and configured to pump blood from the first location to the second location by pumping the blood through the blood pump tube;

[0489] a motor disposed external to the subject's body and configured to rotate the impeller;

[0490] a drive cable extending from outside the subject's body to the axial shaft and configured to impart rotational motion from the motor to the impeller by rotation;

[0491] an outer tube disposed about the drive cable, the outer tube configured to extend from outside the subject's body into the blood pump tube, the outer tube defining a first opening and a second opening on a portion of the outer tube disposed within the blood pump tube; and

[0492] 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;

[0493] at least one pressure sensor configured to measure pressure within the stagnation pressure measurement port and pressure within the static pressure measurement port; and

[0494] A computer processor is configured to determine a flow rate through the blood pump tubing based at least in part on a pressure measured within the stagnation pressure measurement port and a pressure measured within the static pressure measurement port.

[0495] Inventive concept 94. A method comprising:

[0496] A blood pump is inserted into the subject's body, the blood pump comprising:

[0497] an impeller comprising a proximal bushing and a distal bushing,

[0498] a frame disposed around the impeller, the frame including a proximal bearing and a distal bearing, and

[0499] an axial shaft passing 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 remains in an axially fixed position relative to the axial shaft, and the distal bushing of the impeller being not coupled to the axial shaft such that the distal bushing does not remain in an axially fixed position relative to the axial shaft,

[0500] The impeller is maintained in a radially constrained configuration by the delivery catheter while the impeller is inserted into the body of the subject;

[0501] allowing the distal hub to slide on the axial shaft by releasing the impeller from the catheter while the impeller is disposed within the body of the subject, thereby causing the impeller to change from its radially constrained configuration to a non-radially constrained configuration; and

[0502] Blood is pumped through the subject's body using the impeller while the impeller is disposed in its non-radially constrained configuration.

[0503] Inventive concept 95. A method comprising:

[0504] placing an impeller of a ventricular assist device within the left ventricle of the subject, with a frame disposed around the impeller; and

[0505] The impeller is driven by rotating the impeller to pump blood from the left ventricle of the subject to the aorta,

[0506] Positioning of the impeller within the left ventricle permits axial movement of the impeller relative to the frame in response to cyclic changes in the pressure differential between the left ventricle and the aorta.

[0507] Inventive concept 96. A method comprising:

[0508] A blood pump is placed in the subject's body, the blood pump comprising:

[0509] an impeller having a frame disposed about the impeller, the impeller including a proximal bushing and a distal bushing, and the frame including a proximal bearing and a distal bearing, and

[0510] an axial shaft passing through the proximal and distal bearings of the frame and the proximal and distal bushings of the impeller, the axial shaft coupled to at least one of the proximal and distal bushings of the impeller such that the at least one bushing is retained in an axially fixed position relative to the axial shaft and is not retained in an axially fixed position relative to the proximal and distal bearings;

[0511] as well as

[0512] An impeller is used to pump the blood through the subject's body.

[0513] Inventive concept 97. A method comprising:

[0514] placing an impeller of a blood pump within a subject's body, with a frame disposed around the impeller; and

[0515] The impeller is driven to pump blood through the subject's body without using any thrust bearings disposed within the subject's body to provide opposition to thrust generated by rotation of the impeller.

[0516] The present invention will be more fully understood from the following detailed description of embodiments of the invention taken in conjunction with the accompanying drawings, in which: BRIEF DESCRIPTION OF THE DRAWINGS

[0517] Figure 1A and Figure 1B is a schematic diagram of a ventricular assist device according to some applications of the present invention, the distal end of the ventricular assist device being positioned in the left ventricle of a subject;

[0518] Figure 2A 、 Figure 2B and Figure 2C is a schematic diagram of a pump portion of a ventricular assist device according to some applications of the present invention;

[0519] Figure 3A 、 Figure 3B and Figure 3C is a schematic diagram of an impeller of a ventricular assist device according to some applications of the present invention;

[0520] Figure 4 is a schematic diagram of an impeller disposed within a frame of a ventricular assist device according to some applications of the present invention;

[0521] Figure 5A and Figure 5B is a schematic diagram of an impeller and frame of a ventricular assist device in its non-radially constrained and radially constrained states, respectively, according to some applications of the present invention;

[0522] Figure 5C is a schematic diagram of a typical bearing assembly used in a prior art axial impeller-based blood pump;

[0523] Figure 6A and Figure 6B is a schematic diagram of a ventricular assist device at various stages of a motion cycle of an impeller of the ventricular assist device relative to a frame of the ventricular assist device according to some applications of the present invention;

[0524] Figure 6C is a schematic diagram of an axial shaft receiving tube and distal tip portion of a ventricular assist device according to some applications of the present invention;

[0525] Figure 7is a schematic diagram of a motor unit of a ventricular assist device according to some applications of the present invention;

[0526] Figure 8A and Figure 8B is a schematic diagram of a motor unit of a ventricular assist device according to some applications of the present invention;

[0527] Figure 9 is a graph indicating changes in the length of a drive cable of a ventricular assist device when the pressure gradient resisted by an impeller of a blood pump changes, as measured in experiments performed by the inventors of the present application;

[0528] Figure 10A 、 Figure 10B and Figure 10C is a schematic diagram of a drive cable for a ventricular assist device according to some applications of the present invention;

[0529] Figure 11A and Figure 11B is a schematic diagram of an interface component forming an interface between respective portions of a drive cable of a ventricular assist device according to some applications of the present invention;

[0530] Figure 11C 、 Figure 11D and Figure 11E is a schematic diagram of an interface between a drive cable and an axial shaft of a ventricular assist device according to some applications of the present invention;

[0531] Figure 12 is a schematic diagram of a drive cable of a ventricular assist device according to some applications of the present invention, the drive cable including a friction reducing element disposed about at least a portion of the drive cable;

[0532] Figure 13 is a schematic diagram of a procedure for decontaminating a drive cable and / or radial bearing of a ventricular assist device according to some applications of the present invention;

[0533] Figure 14A and Figure 14B is a schematic diagram of a frame of a ventricular assist device according to some applications of the present invention, with a stator coupled to a proximal portion of the frame;

[0534] Figure 15A is a schematic diagram of a flat profile of a frame of a ventricular assist device according to some applications of the present invention;

[0535] Figure 15B is a schematic diagram showing an enlarged view of the proximal end of a frame of a ventricular assist device according to some applications of the present invention;

[0536] Figure 15Cis a schematic diagram of a frame of a ventricular assist device according to some applications of the present invention, with material defining curved protrusions coupled to the frame;

[0537] Figure 16A 、 Figure 16B 、 Figure 16C and Figure 16D is a schematic diagram of a ventricular assist device including one or more blood pressure measurement tubes according to some applications of the present invention;

[0538] Figure 17A 、 Figure 17B and Figure 17C is a schematic diagram of a ventricular assist device including a pitot tube configured to measure blood flow through a tube of the device according to some applications of the present invention;

[0539] Figure 18 is a schematic diagram of a ventricular assist device according to some applications of the present invention, wherein the distal portion of the device is a radially expandable atraumatic distal distal portion;

[0540] Figure 19A and Figure 19B is a schematic diagram of a ventricular assist device according to some applications of the present invention, wherein the distal portion of the device is a radially expandable atraumatic distal distal portion;

[0541] Figure 20A and Figure 20B is a schematic diagram of a ventricular assist device according to some applications of the present invention, wherein the distal portion of the device is a radially expandable atraumatic distal distal portion;

[0542] Figure 21A 、 Figure 21B 、 Figure 21C and Figure 21D is a schematic diagram of a distal tip portion of a ventricular assist device according to some applications of the present invention;

[0543] Figure 22A and Figure 22B is a schematic diagram of a distal tip portion of a ventricular assist device in an axially reinforced configuration and a non-axially reinforced configuration, respectively, according to some applications of the present invention;

[0544] Figure 23A and Figure 23B is a schematic diagram of a distal tip portion of a ventricular assist device in a radially constrained configuration and a non-radially constrained configuration, respectively, according to some applications of the present invention;

[0545] Figure 24A and Figure 24B is a schematic diagram of a distal tip portion of a ventricular assist device in a radially constrained configuration and a non-radially constrained configuration, respectively, according to some applications of the present invention;

[0546] Figure 25A is a schematic diagram of a first portion and a second portion of a coupling element according to some applications of the present invention, the coupling element being configured to facilitate radial contraction of an impeller (e.g., during crimp);

[0547] Figure 25B and Figure 25C is a schematic diagram of various stages of collapse of an impeller according to some applications of the present invention;

[0548] Figure 26 is a schematic diagram of a blocker configured to prevent distal advancement of an impeller of a ventricular assist device during withdrawal of the ventricular assist device from a subject's body according to some applications of the present invention;

[0549] Figure 27A and Figure 27B is a schematic diagram of a ventricular assist device according to some applications of the present invention, the device including a valve to prevent backflow of blood, such as in the event of a malfunction of an impeller of the ventricular assist device; and

[0550] Figure 28A 、 Figure 28B and Figure 28C is a schematic diagram of a ventricular assist device according to some applications of the present invention, the device including a safety bladder to prevent backflow of blood, such as in the event of a ventricular assist device impeller failure. DETAILED DESCRIPTION

[0551] Now refer to Figure 1A and Figure 1B , Figure 1A and Figure 1B is a schematic diagram of a ventricular assist device 20 according to some applications of the present invention, the distal end of the ventricular assist device 20 being disposed in the left ventricle 22 of a subject; the ventricular assist device includes a tube 24 that passes through the subject's aortic valve 26 so that the proximal end 28 of the tube is disposed in the subject's aorta 30 and the distal end 32 of the tube is disposed within the left ventricle 22. Tube 24 (sometimes referred to herein as a "blood pump tube") is typically an elongated tube with an axial length that is typically significantly greater than its diameter. The scope of the present invention includes use of the apparatus and methods described herein in anatomical locations other than the left ventricle and aorta. Accordingly, the ventricular assist device and / or portions thereof are sometimes referred to herein (in the specification and claims) as a blood pump.

[0552] like Figure 1B As shown in Figure 1BThe steps of deploying a ventricular assist device in the left ventricle are shown, typically with the distal end of the ventricular assist device being guided to the left ventricle over a guidewire 10. During insertion of the distal end of the device into the left ventricle, a delivery catheter 143 is positioned over the distal end of the device. Once the distal end of the device is positioned in the left ventricle, the delivery catheter is typically retracted into the aorta and the guidewire withdrawn from the subject's body. 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, a ventricular assist device is inserted into the body of a subject to provide acute treatment to the subject. For some applications, to withdraw the left ventricular device from the subject's body at the conclusion of treatment, the delivery catheter is advanced over the distal end of the device, causing 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, causing the self-expandable component of the distal end of the device to assume a radially constrained configuration.

[0553] Also refer to Figure 2A 、 Figure 2B and Figure 2C , Figure 2A 、 Figure 2B and Figure 2C is a schematic diagram of a blood pump portion 27 of a ventricular assist device 20 according to some applications of the present invention; generally, an impeller 50 is disposed within 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 defines one or more blood inlet openings 108 at the distal end of the tube through which blood flows from the left ventricle into the tube during operation of the impeller. For some applications, a proximal portion of the tube defines one or more blood outlet openings 109 through which blood flows from the tube into the ascending aorta during operation of the impeller.

[0554] For some applications, the console 21 (which typically includes a computer processor 25 ( Figure 1A For example, a computer processor may control the motor 74 ( Figure 7 ), the motor 74 is provided in the motor unit 23, and the motor 74 is driven via a drive cable 130 (also Figure 7) drives the impeller to rotate. For some applications, the computer processor is configured to detect physiological parameters of the subject (such as left ventricular pressure, cardiac afterload, etc.) and is configured to control the rotation of the impeller in response thereto, as described in further detail below. Generally, the operations performed by the computer processor described herein convert the physical state of the memory to have different magnetic polarity, charge, etc., depending on the technology of the memory used, which is the real physical item that communicates with the computer processor. The computer processor 25 is typically a hardware device programmed with computer program instructions to produce a special-purpose computer. For example, when programmed to perform the techniques described herein, the computer processor 25 typically acts as a special-purpose ventricular assist computer processor.

[0555] For some applications, purge system 29 drives fluid (eg, glucose solution) through portions of ventricular assist device 20, for example, to cool portions of the device and / or to clean debris from portions of the device. Purge system 29 is described in further detail below.

[0556] Typically, along a 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 shaped so 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 maintain 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.

[0557] For some applications (not shown), during operation of the ventricular assist device, the distal portion of the tube is at least partially disposed within the native aortic valve and the frame is configured to maintain the aortic valve open by assuming its generally circular, elliptical, or polygonal cross-sectional shape. For some applications, the tube 24 is sized so as to prevent the shape memory alloy of the frame 34 from fully assuming the dimensions to which the shape memory alloy was shaped. In this way, the frame is "pre-tensioned" such that even if the aortic valve applies radial compressive forces to the tube and frame, the frame does not become radially compressed because the frame is already held in a partially radially constrained state by the tube. For some applications, the frame includes a plurality of rigid struts 111 that are 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 disposed) maintains a generally straight longitudinal axis even when subjected to anatomical forces within the left ventricle and / or the aortic valve. Typically, the rigid struts are configured such that the length of the rigid struts does not change even if the frame 34 is changed from a radially constrained configuration (in which the frame is typically positioned during introduction of the frame into the body of a subject) to a non-radially constrained configuration (in which the frame is typically positioned during operation of the ventricular assist device).

[0558] For some applications, along the proximal portion 106 of the tube 24, no frame is disposed within the tube, and thus the tube is not supported in the open position by the frame 34. The tube 24 is typically made of a collapsible material that is impermeable to blood. For example, the tube 24 may include polyurethane, polyester, and / or silicone. Typically, the proximal portion of the tube is configured to be positioned 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, from the left ventricle of the subject, and into the ascending aorta of the subject, such as Figure 1B As described above, the tube typically defines one or more blood inlet openings 108 at the distal end of the tube, and during operation of the impeller, blood flows from the left ventricle into the tube via the inlet openings. For some applications, the proximal portion of the tube defines one or more blood outlet openings 109, and during operation of the impeller, blood flows from the tube into the ascending aorta via the outlet openings. Typically, the tube defines a plurality of blood outlet openings 109, for example, between two and eight blood outlet openings (for example, between two and four blood outlet openings). During operation of the impeller, the blood flow pressure through the tube typically maintains the proximal portion of the tube in an open state. For some applications, in the event of, for example, a malfunction of the impeller, the proximal portion of the tube is configured to collapse inwardly in response to a pressure outside the proximal portion of the tube exceeding the pressure inside the proximal portion of the tube. In this way, the proximal portion of the tube acts as a safety valve, thereby preventing blood from flowing back into the left ventricle from the aorta.

[0559] For some applications, the computer processor 25 ( Figure 1A ) is configured to control the pumping of the blood pump (e.g., by controlling the rotation of the impeller) such that the blood pressure generated by the pump within tube 24 exceeds the subject's aortic systolic pressure during systole, but is less than the subject's aortic diastolic pressure during diastole. During systole, the proximal portion 106 of 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 tube 24 closes because the aortic pressure applied to the tube from outside the tube exceeds the blood pressure within the tube. In this manner, the impeller pumps blood from the left ventricle to the aorta in a pulsatile manner (i.e., by pumping blood from the left ventricle to the aorta only during diastole). For some applications, the computer processor is configured to measure the subject's aortic pressure, left ventricular pressure, and / or flow through tube 24, for example, using the techniques described below with reference to Figure 9 、 Figures 16A-16D and / or Figures 17A-17C The technology described herein. For some such applications, the computer processor controls the rotation of the impeller in the manner described above based on measured aortic pressure, left ventricular pressure, and / or flow. Alternatively, the computer processor controls the rotation of the impeller in a manner different from that described above based on measured aortic pressure, left ventricular pressure, and / or flow. For example, the computer processor can be configured to vary the rotation rate of the impeller based on 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.

[0560] Typically, pumping blood through the impeller increases aortic pressure and reduces left ventricular pressure. Once the flow through tube 24 reaches a critical value (above this critical value, the aortic pressure is higher than the left ventricular pressure, even during ventricular systole (hereinafter referred to as "systole")), the aortic valve remains closed around the outside of tube 24 throughout the cardiac cycle, and the flow from the ventricle to the aorta only occurs via the tube. Typically, above this point where the aortic pressure is disengaged from the ventricular pressure, the left ventricle no longer performs net external work (net external work) (defined as volume change multiplied by pressure change) because it does not move any volume. In this mode, the oxygen consumption of the left ventricle depends on the circulatory pressure generated by the aortic valve that resists closure, the wall tension, wall thickness, and baseline metabolic demand (including calcium circulation) caused by the size of the left ventricle. Below this critical point of impeller activity, the aortic valve is typically at least partially open during systole, and left ventricular outflow will occur simultaneously between the outside of the tube and the aortic valve (by means of left ventricular contraction) and through the tube (by means of impeller rotation and pumping). For a given impeller revolutions per minute, the larger the cross-sectional area of the cannula, the greater the flow rate through the cannula will generally be. At the same time, the larger the cross-sectional area of the cannula, the more space the cannula takes up within the left ventricular outflow tract, the smaller the remaining outflow area, and therefore, the higher the outflow resistance the left ventricle must overcome when pumping around the outside of the cannula.

[0561] Thus, in general, there is a trade-off between the efficiency with which the impeller assists the left ventricle (which advantageously increases with tube diameter) and the residual outflow resistance around the exterior of tube 24 (which disadvantageously increases with tube diameter). The higher the flow rate through the tube provided by the impeller (for a given tube diameter), the less impact the reduced cross-sectional outflow area may have on the effective outflow resistance because the remaining cross-sectional area may be appropriate for the remaining small stroke volume that the ventricle must eject, i.e., the reduced residual outflow tract area may not create undue resistance to outflow. However, conversely, once a fixed tube diameter is selected, the effective resistance to outflow increases as the flow rate through the tube decreases because a larger proportion of the left ventricular stroke volume now needs to pass through the residual outflow tract area around the tube. Therefore, for some applications, the left ventricular outflow resistance is configured to automatically adjust to compensate for changes in the blood flow through the tube generated by the impeller. For example, the tube may be made of a compliant material whose compliance allows a reduction in flow through the tube and a subsequent decrease in expansion pressure, resulting in a reduction in the cannula diameter, thereby increasing the outflow area available to the left ventricle. Typically, the material properties of the compliant material are defined such that (a) maximum tube expansion is achieved at or near the point in time (regardless of the time in the cardiac cycle) when the intraluminal pressure generated by the pumping flow exceeds the aortic pressure and thus remains above the left ventricular pressure throughout the cardiac cycle, and (b) complete collapse of the tube is achieved when the flow through the tube generated by the impeller becomes zero.

[0562] Now refer to Figure 2B , for some applications, a plurality of elongated commissural elements 107 extend along at least some of a proximal portion 106 of tube 24. As described above, for some applications, computer processor 25 is configured to drive impeller 50 to pump blood from the left ventricle to the aorta in a pulsatile manner. For some applications, the commissural elements are configured to facilitate opening and closing of the proximal portion of the tube in a manner similar to the opening and closing of natural valve leaflets, wherein corresponding portions of the circumference of the tube form cusps that contact each other when the tube is closed. For some applications, the ventricular assist device includes three elongated commissural elements, and the proximal portion of tube 24 is configured to close in a manner similar to the closure of a tri-leaflet valve. ( Figure 2B (Such an embodiment is depicted, but one of the commissure elements is hidden from view.) For some applications (not shown), the ventricular assist device includes two elongated commissure elements, and the proximal portion of tube 24 is configured to close in a manner similar to the closure of a bi-leaflet valve. For some applications, the proximal portion of tube 24 is positioned so as to pass through the subject's aortic valve, and the commissure elements are rotationally aligned with the commissures of the native valve. In this manner, the artificial cusps of the proximal portion of the tube are aligned with the native aortic valve leaflets.

[0563] refer to Figure 2A-2C For some applications, the frame 34 is shaped such that the frame defines a proximal conical portion 36, a central cylindrical portion 38, and a distal conical portion 40. Typically, the proximal conical portion is such that the narrow end of the cone is proximal relative to the wide end of the cone. Additionally, typically, the distal conical portion is such that the narrow end of the cone is distal relative to the wide end of the cone. For some applications, the tube 24 extends to the end of the cylindrical portion 38 such that the distal end of the tube defines a single axially facing blood inlet opening 108, as shown. Figure 2A and Figure 2B Optionally, the tube 24 extends to the end of the distal conical portion 40 and defines one or more lateral blood inlet openings, such as Figure 2C For such applications, the tube typically defines two to four lateral blood inlet openings.

[0564] Typically, the tube 24 includes a conical proximal portion 42 and a cylindrical central portion 44. Typically, the proximal conical portion is such that the narrow end of the cone is proximal relative to the wide end of the cone. As described above, for some applications, the tube extends to the end of the distal conical portion 40 of the frame 34. For such applications, the tube typically defines a distal conical portion 46 in which the narrow end of the cone is distal relative to the wide end of the cone, as described above. Figure 2C. For some applications (not shown), the diameter of the tube 24 varies along the length of the central portion of the tube, so that the central portion of the tube has a frustoconical shape. For example, the central portion of the tube can widen from its proximal end to its distal end, or can narrow from its proximal end to its distal end. For some applications, at its proximal end, the central portion of the tube has a diameter between 5 mm and 7 mm, and at its distal end, the central portion of the tube has a diameter between 8 mm and 12 mm.

[0565] Now refer to Figure 3A-3C , Figure 3A-3C is a schematic diagram of an impeller 50 according to some applications of the present invention. Typically, the impeller includes at least one outer helical elongate element 52 wound around a central axial spring 54 such that the helix defined by the helical elongate element is coaxial with the central axial spring. Typically, the impeller includes two or more helical elongate elements (e.g., three helical elongate elements, such as Figure 3A-3C For some applications, the helical elongate element and the central axial spring are made of a shape memory material, for example, a shape memory alloy such as Nitinol. Typically, each of the helical elongate element and the central axial spring supports a membrane 56 of a material (e.g., a polymer such as polyurethane and / or silicone) therebetween. For illustrative purposes, Figure 3A The impeller is shown without material. Figure 3B and Figure 3C A view of an impeller is shown respectively, wherein the material is supported between the helical elongated element and the spring.

[0566] Each helical elongate element defines a respective impeller blade together with a membrane extending from the helical elongate element to the spring, wherein the helical elongate element defines the outer edge of the blade and the axial spring defines the axis of the impeller. Typically, the membrane of material extends along and covers the spring. For some applications, suture 53 (e.g., polyester suture, in Figure 3B and Figure 3C 22890 to Schwammenthal, which is incorporated herein by reference. Typically, the suture is configured to promote bonding between a membrane of material (typically a polymer, such as polyurethane or silicone) and a spring (typically a shape memory alloy, such as nitinol). For some applications, a suture (e.g., a polyester suture, not shown) is wrapped around spring 54. Typically, the suture is configured to promote bonding between a membrane of material (typically a polymer, such as polyurethane or silicone) and a spring (typically a shape memory alloy, such as nitinol).

[0567] Typically, the proximal ends of the spring 54 and the helical elongate element 52 extend from the impeller's proximal bushing (i.e., sleeve bearing) 64, such that the proximal ends of the spring 54 and the helical elongate element 52 are disposed at similar radial distances from each other along the impeller's longitudinal axis. Similarly, typically, the distal ends of the spring 54 and the helical elongate element 52 extend from the impeller's distal bushing 58, such that the distal ends of the spring 54 and the helical elongate element 52 are disposed at similar radial distances from each other along the impeller's longitudinal axis. Typically, the spring 54 and the impeller's proximal and distal bushings 64, 58 define an internal cavity 62 therethrough.

[0568] Now refer to Figure 4 , Figure 4 is a schematic diagram of an impeller 50 disposed within a frame 34 of a ventricular assist device 20 in accordance with some applications of the present invention. As shown, a gap G generally exists between the outer edge of the impeller 50 and the inner surface of the frame 34, even when the impeller's span is at its maximum. For some applications, it is desirable that the gap between the outer edge of the impeller's blades and the inner surface of the frame 34 be relatively small so that the impeller effectively pumps blood from the subject's left ventricle into the subject's aorta. However, it is also desirable to maintain a gap between the outer edge of the impeller's blades and the inner surface of the frame 34, for example, to reduce the risk of hemolysis.

[0569] For some applications, the gap G between the outer edge of the impeller and the inner surface of the frame 34 is greater than 0.05 mm (e.g., greater than 0.1 mm) and / or less than 1 mm (e.g., less than 0.4 mm) at the location where the span of the impeller is at its maximum, for example, 0.05 mm to 1 mm, or 0.1 mm to 0.4 mm. For some applications, the outer diameter of the impeller at the location where the outer diameter of the impeller is at its maximum is greater than 6 mm (e.g., greater than 6.5 mm) and / or less than 8 mm (e.g., less than 7 mm), for example, 6 mm to 8 mm, or 6.5 mm to 7 mm. For some applications, the inner diameter of the frame 34 is greater than 6.5 mm (e.g., greater than 7 mm) and / or less than 8.5 mm (e.g., less than 7.5 mm), for example, 6.5 mm to 8.5 mm, or 7 mm to 7.5 mm.

[0570] Typically, the axial shaft 92 passes through the axis of the impeller 50 through the impeller's internal cavity 62. Typically, the impeller's proximal bushing 64 is coupled to the shaft such that the proximal bushing's axial position relative to the shaft is fixed and the impeller's distal bushing 58 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 internal 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 relatively small gaps (e.g., such as those described above) between the outer edges of the impeller's blades and the inner surface of the frame 34 are maintained during rotation of the impeller.

[0571] Reference again Figure 3A-3C For some applications, the impeller includes a plurality of elongated elements 67 extending radially from the central axial spring 54 to the outer helical elongated elements 52. The elongated elements are generally flexible but substantially inextensible along the axis defined by the elongated elements. Additionally, typically, each elongated element is configured not to exert a force on the helical elongated element unless a force acts on the impeller that causes the helical elongated element to move radially outward such that (in the absence of the elongated elements) the spacing between the helical elongated element and the central axial spring would be greater than the length of the elongated element. For example, the elongated elements may include a string (such as polyester and / or another polymer or natural material containing fibers) and / or a wire (such as nitinol wire and / or a wire made from a different alloy or metal).

[0572] For some applications, the elongated element 67 holds the spiral elongated element (which defines the outer edges of the impeller blades) within a given distance relative to the central axial spring. In this way, the elongated element is configured to prevent the outer edges of the impeller from being pushed radially outward due to forces exerted on the impeller during rotation of the impeller. The elongated element is thereby configured to maintain a gap between the outer edges of the impeller blades and the inner surface of the frame 34 during rotation of the impeller. Typically, more than one (e.g., more than two) and / or fewer than eight (e.g., fewer than four) elongated elements 67 are used in the impeller, with each elongated element typically being doubled (i.e., extending radially from the central axial spring 54 to the outer spiral elongated element 52, and then from the spiral elongated element back to the central axial spring). For some applications, multiple elongated elements are formed from a single piece of string or wire, with each of the multiple elongated elements extending from the spring to a corresponding spiral elongated element and back to the spring, as described in further detail below.

[0573] For some applications, the impeller is manufactured in the following manner. The proximal bushing 64, the distal bushing 58, and the helical elongate element 52 are cut from a tube of a shape memory material, such as nitinol. The cutting of the tube and the shaping of the shape memory material are typically performed such that the helical elongate element is defined by the shape memory material, for example, using techniques generally similar to those described in US 2016 / 0022890 to Schwammenthal. Typically, the spring 54 is inserted into the cut and shaped tube such that the spring extends along the length of the tube from at least the proximal bushing to the distal bushing. For some applications, the spring is inserted into the cut and shaped tube while the spring is in an axially compressed state, and the spring is configured to be maintained in position 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 (which it is typically disposed in during operation of the impeller), there is substantially no gap between a winding of the spring and a winding adjacent to the winding.

[0574] For some applications, at this stage, the elongated element 67 as described above is placed so as to extend between the spring and one or more spiral elongated elements (e.g., in the following manner). A mandrel (e.g., a polyetheretherketone (PEEK) and / or polytetrafluoroethylene (PTFE) mandrel) is inserted through the lumen defined by the spring and bushing. The string or wire is then passed through so that it (a) goes from the mandrel to the first spiral elongated element, (b) goes from the first spiral elongated element back to the mandrel, (c) passes around the mandrel and to the second spiral elongated element, (d) goes from the second spiral elongated element back to the mandrel, and so on. Once the string or wire has passed from the mandrel to each spiral elongated element and back again, the ends of the string or wire are coupled to each other, for example by tying them to each other. For some applications, a suture 53 (e.g., a polyester suture) is wrapped around the spiral elongated element to facilitate bonding between the membrane of material (typically a polymer, such as polyurethane or silicone) and the spiral elongated element (typically a shape memory alloy, such as nitinol) in subsequent stages of impeller manufacture. For some applications, suture (e.g., polyester suture, not shown) is wrapped around spring 54. Typically, the suture is configured to facilitate bonding between the membrane material (typically a polymer such as polyurethane or silicone) and the spring (typically a shape memory alloy such as Nitinol) during subsequent stages of impeller fabrication.

[0575] Usually, at this stage, Figure 3AAs shown in FIG, the structure 59 has been assembled. The structure comprises a cut and shaped tube defining the proximal and distal bushings and the helical elongate element, the spring and optionally the elongate element and the suture. The structure is immersed in the material defining the membrane 56. For some applications, the assembled structure is immersed in the material with the mandrel disposed through the lumen defined by the spring and bushing, although it is noted that the mandrel is not disposed in the lumen. Figure 3A Typically, the material from which the membrane is made is silicone (and / or a similar polymer), and the assembled structure is immersed in this material while it is in an uncured liquid state. Subsequently, the material is cured so that it solidifies, for example, by allowing it to dry. Once the material has dried, the mandrel is typically removed from the inner cavity defined by the bushing and spring.

[0576] The result of the process described above is typically a continuous film of material that extends between each helical elongated element to the spring and also along the length of the spring to define a tube within which the spring is embedded. The portions of the film extending from each helical elongated element to the spring define the impeller blades. For applications where the impeller includes elongated element 67, the elongated element is typically embedded in these portions of the film.

[0577] Typically, the impeller 50 is inserted into the left ventricle transcatheterally while the impeller 50 is in a radially constrained configuration. In the radially constrained configuration, both the helical elongated element 52 and the central axial spring 54 become axially elongated and radially constrained. Typically, a membrane 56 of material (e.g., silicone) changes shape to conform to the shape changes of the helical elongated element and the axial support spring, both of which support the membrane of material. Typically, using a spring to support the inner edge of the membrane allows the membrane to change shape without becoming broken or collapsed because the spring provides a large surface area to which the inner edge of the membrane is bound. For some applications, using a spring to support the inner edge of the membrane reduces the diameter to which the impeller can be radially constrained relative to if, for example, a rigid shaft were used to support the inner edge of the membrane because the diameter of the spring itself can be reduced by axially stretching the spring.

[0578] As described above, for some applications, proximal bushing 64 of impeller 50 is coupled to axial shaft 92 such that the axial position of the proximal bushing relative to the shaft is fixed, and distal bushing 58 of the impeller is slidable relative to the shaft. For some applications, when the impeller is radially constrained for insertion into a ventricle or for extraction from a subject's body, the impeller is axially extended by sliding the distal bushing distally along the axial axis.

[0579] like Figure 3A-3C, after being released into the body of the subject, the impeller assumes its non-radially constrained configuration (in which the impeller is typically disposed during operation of the impeller). Typically, when the impeller 50 is in the non-radially constrained configuration (e.g., within a ventricle of the subject), the pitch of each helical elongate element 52 is greater than 1 mm (e.g., greater than 6 mm), and / or less than 20 mm (e.g., less than 10 mm). Typically, other factors being equal, the greater the pitch of the helical elongate elements (and therefore the impeller blades), the greater the blood flow generated by the impeller. Thus, as described, when the impeller 50 is in the non-radially constrained configuration, the pitch of the helical elongate elements 52 is typically greater than 1 mm (e.g., greater than 6 mm). On the other hand, it is typically desired that the impeller obstruct the backflow of blood into the left ventricle of the subject. Other factors being equal, it is typically the case that the smaller the pitch of the helical elongate elements (and therefore the impeller blades), the greater the obstruction provided by the impeller. Thus, as described, when the impeller 50 is in the non-radially constrained configuration, the pitch of the helical elongate element 52 is typically less than 20 mm (eg, less than 10 mm).

[0580] For some applications, at least when the impeller is in a non-radially constrained configuration, the pitch of the helical elongate element (and therefore the impeller blades) varies along the length of the helical elongate element. Typically, for such applications, the pitch increases from the distal end of the impeller (i.e., the end that is inserted further into the subject's body and positioned upstream relative to the direction of antegrade blood flow) to the proximal end of the impeller (i.e., the end that is positioned downstream relative to the direction of antegrade blood flow) such that the pitch increases in the direction of blood flow. Typically, blood flow velocity increases along the impeller, in the direction of blood flow. Therefore, the pitch increases in the direction of blood flow to further accelerate the blood.

[0581] Note that for illustrative purposes, in some of the figures, the impeller 50 is shown without the Figure 3A-3C All features of the impeller shown and described. For example, some of the figures show an impeller that does not include stitching 53 and / or elongated element 67. The scope of this application includes the use of any device and method described herein with reference to Figure 3A-3C Impeller of any character as shown and described.

[0582] Now refer to Figure 5A and Figure 5B , Figure 5A and Figure 5B2 is a schematic diagram of an impeller 50 and frame 34 of a ventricular assist device 20 in their non-radially constrained and radially constrained states, respectively, according to some applications of the present invention. The impeller and frame are typically positioned in the radially constrained state during insertion of the impeller and frame into the body of a subject via a catheter, and are positioned in the non-radially constrained state during operation of the impeller within the left ventricle of the subject. As described above, the tube 24 typically extends from at least a distal portion of the frame and extends proximally therefrom. However, for illustrative purposes, the frame and impeller are positioned in the radially constrained state. Figure 5A-5B FIG2 is shown without tube 24. Figure 5B As indicated in , the frame and impeller are typically held in a radially constrained configuration by a transfer duct 143 .

[0583] Also refer to Figure 5C , Figure 5C A typical bearing assembly used in a prior art axial impeller based blood pump is shown. Figure 5C It is for the purpose of serving as a reference point for some applications of the invention described herein. Figure 5C As shown in FIG, the bearing assembly generally includes a radial bearing (indicated by ellipse 200) and a thrust bearing (indicated by circle 202). The radial bearing is configured to reduce radial motion of the impeller by maintaining the axis of the impeller at a given radial position. In response to the impeller pumping blood in a first direction, the force acting on the impeller generally urges the impeller to move in a direction opposite to the first direction. The purpose of the thrust bearing is to oppose this motion of the impeller and maintain the axial position of the impeller. Figure 5C In the example shown in FIG, in response to the impeller pumping blood in the direction of arrow 204, the impeller is pushed in the direction of arrow 206, and the thrust bearing opposes this motion. Typically, the bearings experience significant heating and wear due to the frictional forces exerted on the bearings. Thrust bearings are typically subject to significant heating and wear due to the fact that the frictional forces exerted on thrust bearings are typically distributed across opposing surfaces that have a smaller contact area between the surfaces than is the case with radial bearings.

[0584] As described above, typically, axial shaft 92 passes through the axis of impeller 50 through the inner cavity 62 of the impeller. Typically, the proximal bushing 64 of the impeller is coupled to the shaft via 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 proximal radial bearings 116 and distal radial bearings 118 defined by 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 frame 34 such that during rotation of the impeller, even relatively small gaps (e.g., gaps such as those described above) between the outer edges of the impeller's blades and the inner surface of frame 34 are maintained, as described above. For some applications, axial shaft 92 is made of stainless steel and proximal bearings 116 and / or distal bearings 118 are made of hardened steel. Typically, 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 in the distal direction along the axial axis, causing the impeller to become axially extended, as described above. More generally, the impeller changes from its radially constrained configuration to its non-radially constrained configuration, and vice versa, by sliding the distal bushing on the axial axis.

[0585] Typically, the impeller itself is not directly disposed within any radial bearings or thrust bearings. Rather, bearings 116 and 118 act as radial bearings about the axial axis. For some applications, there are no thrust bearings in contact with any surface to potentially generate thrust during rotation of the impeller because the impeller is configured to move axially within frame 34 while the impeller rotates, as described in further detail below. Typically, pump portion 27 (and ventricular assist device 20 more generally) does not include any thrust bearings that are configured to be disposed within the body of the subject and that are configured to oppose the thrust generated by the rotation of the impeller. For some applications, one or more thrust bearings are disposed externally to the body of the subject (e.g., in a Figure 1A 、 Figure 7 and Figure 8A-8B 23 shown in FIG), and the force opposing the thrust generated by the rotation of the impeller is provided solely by one or more thrust bearings disposed externally to the subject's body. For some applications, mechanical and / or magnetic elements are configured to maintain the impeller within a given axial position range. For example, a magnet (e.g., magnet 82, hereinafter referred to as magnet 82) disposed at the proximal end of the drive cable (e.g., externally to the subject's body) may be provided. Figure 7 Description) can be configured to impart axial motion to the impeller and to maintain the impeller within a given axial position range.

[0586] For some optional applications of the present invention, 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 contact the subject's blood. For example, the thrust bearing may be disposed within an outer tube in which a drive shaft for the impeller is disposed. Alternatively or additionally, the thrust bearing may be disposed externally to the subject's body. For some such applications, because the thrust bearing is disposed externally 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 distally of the impeller and in contact with the subject's blood such that the thrust bearing is cooled by the subject's blood.

[0587] Now refer to Figure 6A and Figure 6B , Figure 6A and Figure 6B is a schematic diagram of a ventricular assist device 20 at various stages of a motion cycle of an impeller 50 of the ventricular assist device relative to a frame 34 of the ventricular assist device, according to some applications of the present invention. For some applications, while the impeller pumps blood through tube 24 by rotating, an axial shaft 92 (to which the impeller is fixed) is driven to move the impeller axially back and forth within frame 34 by moving the axial shaft in an axial back and forth motion, as described below with reference to Figure 7 Alternatively or additionally, the impeller and the axial shaft are configured to move axially back and forth within the frame 34 in response to forces acting on the impeller, and the axial shaft does not need to be actively driven to move in an axial back and forth motion, as described below, for example with reference to Figure 9 described in further detail.

[0588] For some applications, by moving the axial shaft in a back-and-forth motion, the portion of the axial shaft that contacts the proximal bearing 116 and the distal bearing 118 is continuously varied. For some such applications, other factors remaining constant, in this manner, the frictional forces exerted on the axial shaft by the bearings are distributed over a larger area of the axial shaft than if the axial shaft were not moved relative to the bearings, thereby reducing wear on the axial shaft. Alternatively or additionally, by moving the axial shaft in a back-and-forth motion relative to the bearings, the axial shaft clears any debris, such as blood residue, from the interface between the axial shaft and the bearings.

[0589] For some applications, when frame 34 and impeller 50 are in their non-radially constrained configuration (e.g., when the frame and impeller are deployed within the left ventricle), the length of the frame exceeds the length of the impeller by at least 2 mm (e.g., at least 4 mm, or at least 8 mm). Typically, proximal bearing 116 and distal bearing 118 are each 2 mm to 4 mm in length. Furthermore, typically, the impeller and axial shaft are configured to move axially within the frame in a back-and-forth motion along at least the length of each of the proximal and distal bearings, or at least along 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.

[0590] Reference again Figure 6A and Figure 6B , and also refer to Figure 6C , Figure 6C is a schematic diagram of an axial shaft receiving tube 126 and distal tip portion 120 of a ventricular assist device 20 according to some applications of the present invention. For some applications, the distal tip portion of the ventricular assist device is configured to be soft, such that the distal tip portion is configured not to injure tissue of a subject even if the distal tip portion comes into contact with tissue (e.g., tissue of the left ventricle). For example, the distal tip portion can be made of silicone. For some applications, the distal tip portion defines a lumen 122 therethrough. For some such applications, during insertion of the ventricular assist device into the left ventricle, for example, according to known techniques, a guide wire 10 ( Figure 1B ) is first inserted into the left ventricle. The distal end portion of the ventricular assist device is then guided to the left ventricle by advancing the distal end portion over a guide wire, wherein the guide wire is disposed within lumen 122. For some applications, a hemostasis valve 152 is disposed at the distal end of lumen 122 of distal end portion 120 such that the distal end portion becomes sealed after the guide wire is retracted from lumen 122. Typically, during insertion of the ventricular assist device into a ventricle of the subject, a delivery catheter 143 is placed over impeller 50 and frame 34 and holds the impeller and frame in their radially constrained configuration. For some applications, the distal end portion 120 extends distally from the delivery catheter during insertion of the delivery catheter into the ventricle of the subject. For some applications, at a proximal end of the distal end portion, the distal end portion has a flared portion 124 that acts as a barrier and prevents advancement of the delivery catheter beyond the flared portion.

[0591] For some applications, the axial shaft receiving tube 126 extends proximally from the distal end portion 120. As described above, typically during operation of the impeller 50, the axial shaft moves back and forth axially. The shaft receiving tube 126 defines an inner cavity 127, which is configured to receive the axial shaft when the axial shaft extends beyond the distal bearing 118. For some applications, the shaft receiving tube defines a stopper 128 at its distal end, which is configured to prevent the axial shaft from advancing beyond the stopper. For some applications, the stopper comprises a rigid component that is inserted (e.g., embedded) into the distal end of the shaft receiving tube. Optionally, the stopper is included in a shoulder between the inner cavity 127 of the axial shaft receiving tube and the inner cavity 122 of the terminal portion 120. Typically, since the inner cavity 122 of the terminal portion 120 is narrower than the inner cavity 127, such a shoulder is present. (This is because lumen 127 is generally configured to receive an axial shaft, while lumen 122 is configured to receive a guidewire 10, and the axial shaft is generally wider than the guidewire 10 because the axial shaft itself is configured to receive the guidewire 10 within its interior lumen 132.) Figure 10B and Figure 10C Typically, during normal operation of the impeller, even when the drive cable 130 (shown in Figure 7 50 and frame 34 during retraction of the ventricular assist device 20 from the subject's ventricle. In some circumstances, there is a risk of the drive cable breaking during advancement of the delivery catheter over the frame and impeller. In the absence of stopper 128, the axial shaft could extend into the distal portion in such an event. Stopper 128 prevents this from occurring, even in the event of a drive cable breaking.

[0592] Typically, during operation of the ventricular assist device, and throughout its reciprocating axial motion cycle, the impeller is positioned relatively close to the distal tip portion. For example, the distance from the impeller to the distal tip portion may be within 50 percent of the distal end of tube 24, such as within 30 percent of the distal end (or 20 percent of the distal end) throughout its reciprocating axial motion cycle.

[0593] For some applications (not shown), a portion of frame 34 extends into the proximal portion of distal tip portion 120. This portion of the frame is configured to cause the proximal portion of the tip to radially expand when deployed within the left ventricle of a subject by shaping this 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 frame 34 extending 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 greater stiffness than the distal portion of the tip portion.

[0594] For some applications, the end portion has Figure 6C The configuration shown in FIG is different from the configuration shown in FIG, as described in further detail below, for example, with reference to FIG. Figure 18-24B For some applications, the distal tip portion will be referred to as Figure 6C Certain features described are similar to those described below (e.g., reference Figure 13 And reference Figure 18-24B For example, the internal structure of the end portion and the proximal extension of the axial shaft receiving tube 126 from the end portion can be as described in reference Figures 6A-6C and / or Figure 13 As described, and the external shape of the end portion can be as described in reference Figure 18-24B Any of the ones described.

[0595] Now refer to Figure 7 , Figure 7 is a schematic diagram of an exploded view of a motor unit 23 of a ventricular assist device 20 according to some applications of the present invention. For some applications, a console 21 ( Figure 1A ) is also configured to control the back-and-forth motion of the axial shaft. Typically, both types of motion are generated using motor unit 23. The scope of the present invention includes controlling the back-and-forth motion at any frequency. For some applications, an indication of the subject's cardiac cycle is detected (e.g., by detecting the subject's ECG), and the back-and-forth motion of the axial shaft is synchronized with the subject's cardiac cycle.

[0596] Typically, the motor unit 23 includes a motor 74 that is configured to transmit rotational motion to the impeller 50 via a drive cable 130. As described in further detail below, typically, the motor is magnetically coupled to the drive cable. For some applications, an axial motion driver 76 is configured to drive the motor to move in an axial back-and-forth motion, as indicated by the bidirectional arrow 79. Typically, by means of a magnetic coupling of the motor to the drive cable, the motor transmits the back-and-forth motion to the drive cable, which in turn transmits the motion to the impeller. As described below, for some applications, the drive cable, impeller and / or axial shaft are subjected to axial back-and-forth motion in a passive manner, for example, due to periodic changes in the pressure gradient against which the impeller pumps blood. Typically, for such applications, the motor unit 23 does not include the axial motion driver 76.

[0597] For some applications, the magnetic connection from the motor to the drive cable is Figure 7 As shown in Figure 7As shown in , a set of drive magnets 77 are coupled to the motor via a drive magnet housing 78. For some applications, the drive magnet housing includes a ring 81 (e.g., a steel ring) and the drive magnets are adhered to the inner surface of the ring. For some applications, as shown, a spacer 85 is adhered to the inner surface of the ring 81 between the two drive magnets. The driven magnet 82 is disposed between the drive magnets so that there is an axial overlap between the drive magnet 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 through it, and the proximal end of the drive cable can be adhered to the inner surface of the driven magnet that defines the hole. For some applications, the driven magnet is cylindrical and the magnet includes a north pole and a south pole, as shown, 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.

[0598] The magnetic coupling is strongest when the field density is greatest. Therefore, it is desirable to use relatively strong magnets for the drive magnet and the driven magnet, with a small air gap between the drive magnet and the driven magnet, and to try to minimize field line leakage. Typically, the drive magnet and the driven magnet are relatively strong neodymium magnets. Furthermore, typically, the gap between each of the drive magnet and the driven magnet is less than 2 mm, for example, about 1 mm. In order to reduce field line leakage, fewer than four magnets (for example, exactly two magnets as shown) are typically used as the drive magnet for the following reasons.

[0599] Typically, it is desirable to minimize the diameter of the driven magnet, for example, to stabilize the driven magnet. As described above, the driven magnet is cylindrical and includes a north pole and a south pole that are separated from each other along the length of the cylinder along the dividing line 83. In the region of the circumference of the driven magnet closest to the dividing line between the north and south poles of the magnet, the magnetic field lines pass directly from the north pole of the magnet to the south pole, rather than crossing the air gap to the first external magnet, passing through the external magnet, around the ring 81, and across the second driving magnet back to the south pole of the driven magnet. As an approximation, any field line that can be drawn between the north and south poles and has a length at least less than the sum of the air gaps between the driven magnet and the driving magnet will pass from the north pole of the driven magnet to the south pole of the driven magnet, rather than taking an alternative route. Assume that this adds up to all field lines extending around 2 mm of the circumference of the driven magnet on either side of the dividing 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) that do not contribute to the magnetic coupling between the driving magnet and the driven magnet. If, instead of having exactly two poles, the driven magnet had four poles and, correspondingly, four drive magnets, there would be four times as much wasted circumferential portion of 2 mm length over the entire circumference, which would result in a total of 8 mm of wasted field lines out of the 12 mm circumference of the inner magnet. Some of this loss would be compensated by adding two additional drive magnets, which increases the magnetic field strength. However, the additional external magnets would be relatively close to each other, which would result in magnetic field leakage between the drive magnets. In view of the above, typically, the motor unit includes fewer than 4 magnets (e.g., exactly two magnets as shown) as drive magnets, and the driven magnet is divided into fewer than 4 poles (e.g., exactly two poles as shown).

[0600] Note that in Figure 7 In the application shown in , the driving magnet is arranged outside the driven magnet. However, the scope of the present application includes the construction of reversing the driving magnet and the driven magnet, mutatis mutandis. For example, the proximal end of the drive cable can be connected to two or more driven magnets, which are arranged around the driving magnet so that there is an axial overlap between the driven magnet and the driving magnet. The above discussion on the number of magnets that should be used as external magnets and the number of poles that the internal magnet should be divided into applies equally to such a construction. That is, for such a construction, typically, the motor unit includes less than 4 magnets (for example, exactly two magnets as shown) as driven magnets, and the driving magnet is divided into less than four poles (for example, exactly two poles as shown).

[0601] As described above, the purification system 29 ( Figure 1A86 and outlet 88 for use with the purge system. For some applications, purge fluid is continuously or periodically pumped into the ventricular assist device via inlet 86 and pumped out of the ventricular assist device via outlet 88. For some applications, purge fluid is pumped into the ventricular assist device, and the inlet port and outlet port are placed in fluid communication with each other so that a given volume of purge fluid circulates within the device for a period of time. Additional aspects of the purge system are described below.

[0602] Now refer to Figure 8A and Figure 8B , Figure 8A and Figure 8B is a schematic diagram of a motor unit 23 according to some applications of the present invention. Figure 8A and Figure 8B The motor unit 23 shown in FIG. Figure 7 The motor unit shown in FIG, and unless otherwise described, as Figure 8A and 8B The motor unit 23 shown in FIG. 1 includes Figure 7 Components similar to motor unit 23 shown in . 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 vibration dampers 94 and 96 configured to dampen vibrations of the motor unit caused by rotational movement and / or axial reciprocating movement of components of the ventricular assist device.

[0603] For some applications, impeller 50 and axial shaft 92 are configured to move axially back and forth within frame 34 in response to forces acting on the impeller, without requiring the axial shaft to be actively driven to move in the axial back and forth motion. Typically, during a subject's cardiac cycle, the pressure differential between the left ventricle and the aorta varies from approximately zero during ventricular contraction (hereinafter "systole") to a relatively large pressure differential (e.g., 60 mmHg-100 mmHg) during ventricular relaxation (hereinafter "diastole"). For some applications, due to the increased pressure differential against which the impeller pumps during diastole, the impeller is urged distally relative to frame 34 during diastole, relative to its position relative to frame 34 during systole. Conversely, because the impeller is connected to the axial shaft, the axial shaft moves forward. During systole, the impeller (and, in turn, the axial shaft) returns to its contracted position. In this manner, the axial back and forth motion of the impeller and axial shaft is generated passively, i.e., the axial shaft and impeller do not need to be actively driven to cause them to undergo such motion.

[0604] Now refer to Figure 9 , Figure 9 is a graph indicating the change in length of a drive cable of a ventricular assist device as the pressure gradient resisted by an impeller of the ventricular assist device changes, as measured in experiments performed by the inventors of the present application. An impeller and drive cable as described herein are used to pump a glycerol-based solution through a chamber, wherein the chamber is configured to replicate the left ventricle and aorta, and the solution has properties similar to those of blood (such as density and viscosity). As the volume of fluid disposed within the chamber (into which the impeller is pumping) increases, the pressure gradient resisted by the impeller changes. Simultaneously, the movement of the drive cable is imaged, and the change in length of the drive cable is determined via machine vision analysis of the image. Figure 9 The graph shown in indicates the change in length of the drive cable as a function of pressure gradient measurement. Figure 9 The y-axis of the graph shown in is such that an elongation of 0 mm represents the length of the drive cable when the impeller is stationary. Note that the graph starts at a pressure gradient value of 65 mmHg and that the elongation at this pressure is negative (at approximately -0.25 mm), i.e., the drive cable is shortened relative to the length of the drive cable before the impeller begins to rotate. This is because the drive cable is configured so that when the impeller first begins pumping, the drive cable is shortened (relative to the length of the drive cable before the impeller is activated) due to the unwinding of the coils within the drive cable, as described in further detail below. As shown in Figure 9 As can be seen in the portion of the curve shown in , after an initial shortening of the drive cable due to the effects described above, it is then the case that the drive cable becomes increasingly elongated as the pressure gradient increases.

[0605] As Figure 9 As indicated by the results shown in FIG and as described above, it is generally the case that, in response to changes in the pressure against which the impeller pumps blood (e.g., the pressure differential between the left ventricle and the aorta), the impeller moves back and forth relative to the frame 34. In turn, the movement of the impeller causes the drive cable 130 to become more or less extended.

[0606] For some applications, during operation of the ventricular assist device, console 21 ( Figure 1A ) is configured to measure an indication of the pressure exerted on the impeller (indicative of a pressure differential between the left ventricle and the aorta) by measuring tension in drive cable 130 and / or an indication of 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 rotation of the impeller and / or axial back-and-forth movement of the axial shaft in response thereto.

[0607] 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, mutatis mutandis, the pressure differential between the right ventricle and the pulmonary artery in a substantially similar manner. For some applications, substantially similar techniques are applied to a cardiac 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, mutatis mutandis, the pressure differential between the first location and the second location in a substantially similar manner.

[0608] Reference again Figure 7 For some applications, ventricular assist device 20 includes sensor 84. For example, the sensor may include a Hall effect sensor disposed within motor unit 23, such as 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 movement of the drive cable 130 and thereby determine the pressure against which the impeller pumps. For example, the inner driven magnet 82 may be axially longer than the outer drive magnet 77. Because the inner magnet is longer than the outer magnet, the magnetic field lines emanating from the inner magnet do not reach the outer magnet, and the magnetic flux generated by these magnetic field lines (as measured by the Hall sensor) varies with the axial movement of the drive cable and thereby the axial movement of the inner magnet. During operation, the motor 74 rotates, thereby generating an AC signal in the Hall sensor, which typically has a frequency between 200 Hz and 800 Hz. Typically, when the tension in the drive cable changes due to the subject's cardiac cycle, this generates 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, a computer processor measures the low frequency envelope and derives the subject's cardiac cycle from the measured envelope. It should be noted that, typically, the axial motion of the magnet is substantially less than the axial motion of the impeller because the full range of motion of the impeller is not transmitted along the length of the drive cable. However, it is generally the case that the axial back-and-forth motion of the impeller produces measurable back-and-forth motion of the magnet.

[0609] For some applications, the Hall sensor measurements are initially calibrated so that the change in magnetic flux per unit change in pressure (i.e., per unit change in the pressure differential between the left ventricle and the aorta) resisted by the impeller pumping is known. It is known that in most subjects, during systole, the left ventricular pressure is equal to the aortic pressure. 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).

[0610] Now refer to Figure 10A 、 Figure 10B and Figure 10C ,Should Figure 10A 、 Figure 10B and Figure 10C FIG2 is a schematic diagram of a drive cable 130 for a ventricular assist device 20 according to some applications of the present invention. Generally, as described above, the rotational motion of the impeller (which motion is transmitted via the axial shaft) and the axial back-and-forth motion of the axial shaft described above are transmitted to the axial shaft via the drive cable. Generally, the drive cable extends from the motor unit 23 (which is typically disposed outside the subject's body) to the proximal end of the axial shaft 92 (e.g., Figure 10C , which shows the connection between the distal end of the drive cable and the proximal end of the axial shaft. For some applications, the drive cable includes a plurality of wires 134 arranged in a tightly coiled configuration to impart sufficient strength and flexibility to the drive cable so that a portion of the cable can remain within the aortic arch (corresponding to the Figure 10A 145 in the figure), while the cable rotates and moves in an axial back-and-forth motion. The drive cable is typically disposed within a first outer tube 140, which is configured to remain stationary while the drive cable rotates and / or moves axially back-and-forth. 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) that is configured to be very fatigue-resistant even under the friction generated by the relative motion between the drive cable and the first outer tube. However, because such polymers are typically relatively rigid, only a thin layer of polymer is typically used in the first outer tube. For some applications, the first outer tube is disposed within a second outer tube 142, which is made of a material that is more flexible 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 the thickness of the first outer tube.

[0611] Typically, during insertion of the impeller and cage into the left ventricle, the impeller 50 and frame 34 are maintained in a radially constrained configuration by the delivery catheter 143. As described above, to position the impeller and frame in a non-radially constrained configuration, the delivery catheter is retracted. For some applications, such as Figure 10A As shown in FIG, 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.

[0612] refer to Figure 10C , typically, the axial shaft and cable define a continuous lumen 132 therethrough. For some applications, the left ventricular device is guided to the aorta and to the left ventricle by placing the axial shaft and cable over 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 greater than 0.6 mm (e.g., greater than 0.8 mm) and / or less than 1.2 mm (e.g., less than 1 mm), such as an outer diameter of 0.6 mm-1.2 mm or 0.8 mm-1 mm. For some applications, the diameter of the lumen 132 defined by the shaft and cable is greater than 0.3 mm (e.g., greater than 0.4 mm) and / or less than 0.7 mm (e.g., less than 0.6 mm), such as 0.3 mm-0.7 mm, or 0.4 mm-0.6 mm. For some applications, the drive cable 130 has a total length greater than 1 m (e.g., greater than 1.1 m) and / or less than 1.4 m (e.g., less than 1.3 m), such as a total length of 1 m to 1.4 m, or 1.1 m to 1.3 m. As described above, for some applications, the guide wire is additionally passed through the lumen 122 of the distal tip portion 120. Typically, the diameter of the lumen 122 is substantially similar to the diameter of the lumen 132.

[0613] refer to Figure 10BFor some applications, drive cable 130 is comprised of a plurality of coiled wires 134. Generally, because the impeller must pump against a pressure gradient during diastole, the impeller is urged distally relative to frame 34 relative to its position relative to the frame during systole, as described above. When 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 tighten, this will also cause the impeller to be advanced relative to the frame due to the coiled wires tightening (i.e., becoming entangled such that the radius of the coils decreases) and thereby lengthening axially. For some applications, at least a portion of the drive cable is configured such that (a) in response to the impeller pumping blood from the left ventricle to the aorta by rotating in a predetermined rotational direction, (b) rotation of the drive cable in that direction causes the coiled wires of the drive cable to at least partially unwind along a portion of the drive cable, causing the portion of the drive cable to shorten axially. By constructing the drive cable in the manner described above, in addition to accommodating distal movement of the impeller within the frame due to pressure changes caused by the subject's cardiac cycle (as described above), the length of the frame 34 does not need to accommodate distal movement of the impeller caused by axial extension of the drive cable. For some applications, the extent to which the drive cable can untwist and, thereby, shorten axially is limited by the outer tube in which the drive cable is disposed, thereby preventing the drive cable from expanding radially. Therefore, for some applications, the drive cable shortens axially by a relatively small amount. For some applications, the drive cable does not shorten because the outer tube limits the extent to which the drive cable can untwist and, thereby, shorten axially. Even in such applications, however, because the winding portion of the coil is constructed as described above, the drive cable is typically configured not to extend.

[0614] Alternatively or additionally, the impeller is inserted into frame 34 such that the drive cable is already in a preloaded state (i.e., such that the impeller exerts tension on the drive cable that causes the drive cable to be axially extended relative to its resting state). Due to the preload of the drive cable, when rotation of the impeller begins, this does not cause the drive cable to axially extend because the drive cable is already in an axially extended state relative to its resting state. For some such applications, the impeller is still configured to undergo axial reciprocating motion (as described above) due to pressure changes caused by the subject's cardiac cycle.

[0615] For some applications, debris is generated by friction between the drive cable and the outer tube 140. Optionally or additionally, a fluid (e.g., a purge fluid) is disposed between the drive cable and the outer tube. Typically, due to the coiled winding portion of the drive cable, the drive cable acts as an impeller and pumps debris and / or fluid axially relative to the outer tube 140. For some applications, the orientation of the winding portion of the drive cable is such that the drive cable is configured to pump debris and / or fluid toward the proximal end of the ventricular assist device by rotating in a predetermined rotational direction and not pump debris and / or fluid toward the distal end of the ventricular assist device toward the patient's left ventricle.

[0616] Now refer to Figure 11A and Figure 11B ,Should Figure 11A and Figure 11B is a schematic diagram of an interface component 154 according to some applications of the present invention, which forms an interface between corresponding portions of a drive cable 130 of a ventricular assist device 20. For some applications, the drive cable includes a first portion and a second portion. Figure 10A Typically, the first portion is configured to be positioned in the subject's aortic arch (i.e., the portion of the aorta corresponding to arrow 145 ), and the second portion is configured to be positioned along the descending aorta (the portion of the aorta corresponding to arrow 147 ), and the second portion is typically configured to extend until the motor unit 23 is outside the subject's body. Typically, at locations where the drive cable 130 experiences significant bending, such as the aortic arch, it is desirable for the drive cable to be relatively flexible. However, a drive cable with greater flexibility is also generally more axially stretchable than a drive cable with less flexibility. Thus, for some applications, there is a trade-off between desiring a drive cable that is sufficiently flexible to conform to the curvature of the aortic arch but, on the other hand, desiring the drive cable to undergo significant axial stretching (which could result in a loss of control over the axial position of the impeller). For some applications, corresponding portions of the drive cable have corresponding degrees of flexibility. For example, a first portion of the drive cable configured to be positioned in the aortic arch may have a first degree of flexibility, while a second portion of the drive cable configured to be positioned in the descending aorta may have a second degree of flexibility, the first degree of flexibility being greater than the second degree of flexibility.

[0617] For some applications, the first portion is configured to be more flexible than the second portion by virtue of the coil of wire 134 in the first portion including less wire than in the second portion. Figures 11A-11BAs shown in , the first portion can include more than 4 wires and less than 8 wires (e.g., 4-8 wires, or 5-7 wires, for example, 6 wires), and the second portion can include more than 8 wires and less than 12 wires (e.g., 8-12 wires, or 9-11 wires, for example, 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), for example, 20 cm-40 cm, or 25 cm-35 cm. For some applications, the length of the second portion of the drive cable is greater than 60 cm (e.g., greater than 70 cm) and less than 100 cm (e.g., less than 90 cm), for example, 60 cm-100 cm, or 70 cm-90 cm.

[0618] For some applications, the two parts of the drive cable are connected to each other via an interface component 154. Typically, the wires of the two parts 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 wire at the junction is distributed over the radius of the groove, rather than being concentrated at the point where the wire is welded to the interface component. For some such applications, the interface component further includes a protrusion 158 that holds the wire in place during welding of the wire to the interface component.

[0619] Now refer to Figure 11C 、 Figure 11D and Figure 11E , Figure 11C 、 Figure 11D and Figure 11E is a schematic diagram of an interface 156 between a drive cable and an axial shaft 92 of a ventricular assist device according to some applications of the present invention. 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 Figure 11C Shown in.

[0620] refer to Figure 11D For some applications, as the coiled wire approaches junction 156, the coiled wire is at least partially straightened (i.e., the pitch of the wire is increased) so that the angle formed by the wire with the junction is less sharp than 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. Figure 11E, for some applications, when the wire approaches the junction 156, in addition to being straightened, the wire is flattened and pushed radially inward. For some applications, the wire is flat enough so that each wire in the coil contacts the adjacent wire to form a cylinder, as shown. For example, the shape of the wire can be changed from a circular cross-section with a radius of approximately 0.2mm to an elliptical cross-section with a minor axis of 0.12mm. For some applications, the flattening is performed along a length between 1mm and 3mm. For some applications, the wire is flattened by placing an overtube 159 around the wire, placing the overtube and wire on a mandrel, and squeezing the overtube and wire radially inward. Subsequently, the overtube and flattened wire are welded to the axial shaft 92 at the junction.

[0621] For some applications, use and reference Figure 11D and Figure 11E A substantially similar technique is described for coupling the two portions of a drive cable to one another. For some applications, as the coiled wire approaches interface member 154, the coiled wire is at least partially straightened (i.e., the pitch of the wire increases) so that the angle formed by the wire with the junction is less acute than it would be if the wire were not straightened. By making the angle less acute, the stress at the point where the wire is welded to the interface member is reduced. For some applications, as the wire approaches interface member 154, in addition to being straightened, the wire is flattened and pushed radially inward. For some applications, the wire is sufficiently flattened so that each wire in the coil contacts the adjacent wires to form a cylinder. For example, the shape of the wire can be changed from a circular cross-section with a radius of approximately 0.2 mm to an elliptical cross-section with a minor axis of 0.12 mm. For some applications, the flattening is performed along a length between 1 mm and 3 mm. For some applications, the wire is flattened by placing an outer sleeve (not shown, but similar to outer sleeve 159) around the wire, placing the outer sleeve and wire on a mandrel, and squeezing the outer sleeve and wire radially inward. The outer sleeve and flat wire are then welded to the interface component 154.

[0622] 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.

[0623] Now refer to Figure 12 , Figure 12 is a schematic diagram of a drive cable 130 of a ventricular assist device 20 according to some applications of the present invention, 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 invention 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 such as cylindrical rollers, spherical rollers, gear bearings, tapered rollers, needle rollers, and / or toroidal roller bearings may be used. For some applications, the friction reducing element is used as an alternative to including the first outer tube 140 in addition to the second outer tube 142. Figure 12 In the example shown in , the friction reducing element is disposed between the drive cable and the second outer tube, and the ventricular assist device does not include the first outer tube and the second outer tube.

[0624] Typically, the ventricular assist device is passed through the aortic arch of the subject and / or other generally curved portions of the subject's vasculature. In the absence of a friction reducing element, the drive cable 130 and tube 142 would typically contact each other, particularly at curved portions of the vasculature. As described above, the drive cable 130 typically performs rotational motion relative to the tube 142, and for some applications, also performs back-and-forth axial motion relative to the tube 142. Therefore, in the absence of a friction reducing element (or first outer tube 140, as described above), considerable friction would be generated at the location where the drive cable and outer tube 142 contact each other. Therefore, for some applications, a friction reducing element is disposed between the drive cable 130 and outer tube 142 to reduce the friction generated at the location where the drive cable 130 and outer tube 142 contact each other. For some applications, the friction reducing element is disposed between the drive cable 130 and outer tube 142 substantially along the entire length of the drive cable 130 and outer tube 142. Optionally, during operation of the ventricular assist device, a friction reducing element is disposed between the drive cable 130 and the outer tube 142 at a location where the drive cable 130 and the outer tube 142 are configured to be substantially curved (e.g., where the drive cable 130 and the outer tube 142 are disposed within the aortic arch).

[0625] Now refer to Figure 13 , Figure 13is a schematic diagram of a procedure for purging a drive cable 130 of a ventricular assist device 20 according to some applications of the present invention. For some applications, proximate 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, during rotation of the drive cable, both the first outer tube and the second outer tube remain stationary. For some applications, a purge fluid (e.g., a fluid containing glucose or dextrose) is pumped between the first outer tube and the second outer tube, and an opening 146 is present within the first outer tube near the proximal bearing. As described above, typically, the purge system 29 ( Figure 1A ) controls the purge fluid through inlet 86 and outlet 88 ( Figure 7 、 Figure 8A and Figure 8B For some applications, the purge fluid flows between the drive cable 130 and the first outer tube 140, as shown by Figure 13 14. In this manner, the interface between the drive cable 130 (which rotates) and the outer tube 140 (which remains stationary during rotation of the drive cable) is purged. For some applications, some purge fluid additionally flows to the interface between the axial shaft and the proximal bearing 116, thereby purging that interface, as indicated by the purge fluid flow arrows 148 in FIG. Figure 13 As indicated by the purge fluid flow arrow 149 in FIG.

[0626] For some applications, the purge fluid is pumped through the lumen 132 defined 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 manner, some of the purge fluid flows to the interface between the axial shaft and the distal bearing 118, thereby purging the interface, as described by Figure 13 As indicated by the purge fluid flow arrow 150 in FIG.

[0627] For some applications, a hemostasis valve 152 is provided at the distal end of the lumen 122 of the distal tip portion 120, as described above. Alternatively or additionally, a plug (not shown) is provided at the distal end of the lumen 122 of the tip portion 120. Typically, the hemostasis valve and / or plug prevents blood from flowing into the lumen 122 and / or lumen 132. Further typically, by preventing the purge fluid from flowing out of the distal end of the lumen 122, the plug causes the purge fluid to flow toward the interface between the axial shaft 92 and the distal bearing 118, as indicated by the lumen 118. Figure 13 As indicated by the purge fluid flow arrow 150 in FIG.

[0628] For some applications, alternative techniques to those described above are used for introducing fluid (e.g., fluid containing glucose) to the ventricular assist device. Figure 13In the application shown in , the fluid is allowed to flow distally after passing through opening 146, as indicated by arrow 149, and as described above. However, for some applications, the flow of fluid in the distal direction is blocked (i.e., the flow of fluid indicated by arrow 149 does not exist). For some such applications, the fluid is initially released into the space between the drive cable 130 (which rotates) and the outer tube 140 (which remains stationary during rotation of the drive cable) so that the fluid fills the space between the drive cable and the outer tube 140 at a location near the opening 146. For example, as shown, the fluid can be pumped into the space via the gap between the first outer tube 140 and the second outer tube 142. The fluid is then typically maintained in place between the drive cable and the outer tube 140 at a location near the opening 146 throughout the operation of the ventricular assist device. The fluid is configured to remove air from the space between the drive cable and the outer tube, and / or to reduce friction between the drive cable 130 (which rotates) and the outer tube 140 (which remains stationary during rotation of the drive cable).

[0629] For some applications, a substantially similar technique is performed, but during operation of the ventricular assist device, fluid is pumped between the drive cable 130 (which rotates) and the outer tube 140 (which remains stationary during rotation of the drive cable). For example, as shown, fluid can be pumped into the space via the gap between the first outer tube 140 and the second outer tube 142. For some applications, 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 the fluid in the distal direction is blocked, as described above. The pumping of fluid is configured to remove air from the space between the drive cable and the outer tube to reduce friction between the drive cable 130 (which rotates) and the outer tube 140 (which remains stationary during rotation of the drive cable), and / or is configured to remove debris generated by the ventricular assist device from the interface between the drive cable and the outer tube.

[0630] Now refer to Figure 14A and Figure 14B , Figure 14A and Figure 14Bis a schematic diagram of a frame 34 of a ventricular assist device 20 according to some applications of the present invention, with a stator 182 coupled to a proximal portion of the frame. For some applications, the stator is integrally formed with the frame 34, as described in 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 the curvature is opposite to the direction of rotation of the impeller, as described in further detail below. For some applications, by using the curved protrusions (e.g., curved so as to be 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 a rotational flow component from the blood flow before the blood flows out of the proximal end of the frame of the ventricular assist device.

[0631] As described above, the device 20 is typically inserted into a ventricle of a subject via a catheter while the frame 34 is in a radially constrained state. Upon release from the catheter, the frame 34 automatically assumes its unconstrained shape due to self-expansion. Typically, during insertion of the frame into the left ventricle, the flexure projections of the stator are in a collapsed state and do not significantly increase the minimum diameter to which the frame can be radially constrained relative to if the tube did not include the flexure projections. When the frame 34 expands, the flexure projections are configured to automatically assume their curved configuration due to the coupling of the flexure projections to the frame 34.

[0632] For some applications, the curved protrusion 66 is made of a flexible material (e.g., a polymer such as polyurethane and / or silicone). The curved protrusion is typically coupled to the curved strut 186 of the frame 34, the curvature of the curved strut thereby defining the curvature of the curved protrusion. Typically, the flexible material is coupled to the frame 34 such that the flexible material defines an inner cavity 188 ( Figure 14B ), the lumen 188 is aligned with the longitudinal axis of the frame. The axial shaft 92 of the ventricular assist device typically enters the proximal end of the frame through the lumen 188.

[0633] For some applications, to facilitate coupling the flexible material to the frame, to form the flexible material into a desired shape, and / or to facilitate formation of lumen 188, a plurality of elongated elements 190 (e.g., strings and / or wires, which are typically made of a material similar to elongated elements 67) are tied to the proximal end of the frame. For some applications, the curved struts 186 define a ring 192 or other coupling element at their distal ends to which the elongated elements 190 are tied. The flexible material is typically coupled to the frame such that a curved membrane of material is supported by the curved struts and the elongated 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 that defines one of the ends of lumen 188. For example, during formation of the stator, a mandrel can be placed through proximal bearing 116 and the elongated elements can be tied to the ring 192 and caused to surround the mandrel so as to define Figure 14B . The proximal end of the frame having the elongated elements and the mandrel is then immersed in a material (which is typically a polymer, such as silicone) while the material is in an uncured liquid state. The material is then cured so that it solidifies, for example, by allowing it to dry. Once the material has dried, the mandrel is typically removed. For some applications, the other end of the lumen 188 is defined by a proximal bearing 116 disposed at the proximal end of the frame 34. Typically, a flexible material extends from a circle 191 defined by a string and / or wire to the proximal bearing 116 to define the lumen 188. For some applications, sutures 189 are tied around the curved struts 186 to facilitate connection between the material and the struts, for example, as described above with reference to the sutures 53 of the impeller 50.

[0634] Now refer to Figure 15A , Figure 15A is a schematic diagram of a flat profile of a frame 34 of a ventricular assist device 20 according to some applications of the present invention. As shown, the frame includes curved struts 186 at its proximal end with loops 192 disposed toward the end of each strut. Figure 15B , Figure 15B is a schematic diagram showing an enlarged view of the proximal end of the frame 34 according to some applications of the present invention. Once the flexible material is coupled to the curved struts, the distal ends 194 of the curved struts 186 generally define the orientation of the leading edges of the corresponding vanes (i.e., curved protrusions) of the stator. Also refer to Figure 15C , Figure 15C is a schematic diagram of a frame 34 according to some applications of the present invention, showing the frame with the material defining curved protrusions 66 coupled to the frame. It can be observed that the orientation of the leading edge of the curved protrusion is defined by the orientation of the corresponding distal end of the curved strut.

[0635] like Figure 15BAs shown in FIG, the distal ends 194 of the curved struts 186 are shaped to define an angle α relative to the axial component of blood flow through the frame, which is indicated by arrow 196 and is parallel to the longitudinal axis of the frame and toward the proximal end of the frame. Figure 15C As indicated in FIG, the leading edge of the corresponding curved protrusion also generally defines an angle approximately equal to angle α relative to the general direction of blood flow. (For some applications, the angle of the leading edge of the curved protrusion becomes slightly less than α as struts 186 radially expand.) 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, between 45 degrees and 85 degrees, or between 60 degrees and 80 degrees.

[0636] The direction of rotation of the impeller is determined by Figure 15C As indicated by arrow 198 in Figure 15C As can be observed in FIG, the curvature of the curved protrusion is generally such that it is opposite to the direction of rotation of the impeller (which is the direction of rotation of the rotational flow component within the blood flow, as imparted by the impeller to the blood flow). From the distal end of the curved protrusion to its proximal end, the curved protrusion curves to become increasingly parallel to the longitudinal axis of the frame. The curvature of the curved protrusion is such that the rotational flow component from the blood flow is reduced before the blood flows out of the proximal end of the frame of the ventricular assist device.

[0637] Now refer to Figure 16A 、 Figure 16B 、 Figure 16C and Figure 16D , Figure 16A 、 Figure 16B 、 Figure 16C and Figure 16D 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 a proximal end of the tube is disposed within the subject's aorta and a distal end of the tube is disposed within the subject's left ventricle. Typically, a blood pump, typically including an impeller 50, is disposed within tube 24, within the subject's left ventricle, and is configured to pump blood from the left ventricle into the subject's aorta through tube 24. For some applications, the blood pressure measuring tube 210 is configured to extend at least to an 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 of the tube 24. A pressure sensor 216 (at Figure 1A24 ). Typically, by measuring the blood pressure within the blood pressure measurement tube, the pressure sensor thereby measures the blood pressure of the subject outside of the tube 24. Typically, the blood pressure measurement tube 210 extends from outside the subject's body to an opening 214 at the distal end of the tube, and the pressure sensor 216 is disposed toward the proximal end of the tube, e.g., outside the subject's body. For some applications, the computer processor 25 ( Figure 1A ) receives an indication of the measured blood pressure and controls the pumping of blood through the impeller in response to the measured blood pressure.

[0638] refer 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 that are configured to extend to the outer surface of blood pump tube 24 at a location along the tube that is configured to be within the left ventricle of the subject near the blood pump (e.g., near impeller 50). For such applications, the pressure sensor is configured to measure the subject's left ventricular pressure by measuring the blood pressure within the left ventricular blood pressure measurement tubes. For some applications, the ventricular assist device includes two or more such left ventricular blood pressure measurement tubes, e.g., Figure 16A and Figure 16B For some applications, based on the blood pressure measured within each of the two or more 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 blocked. This may occur, for example, due to the opening contacting the wall of the interventricular septum and / or a portion of 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 blocked, the computer processor determines the subject's left ventricular pressure based on the blood pressure measured within a different one of the two or more left ventricular blood pressure measurement tubes.

[0639] 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 within the subject's aorta, such as Figure 16C For this application, the pressure sensor is configured to determine the aortic pressure of the subject by measuring the blood pressure in the aortic blood pressure measuring tube. For some applications, the ventricular assist device includes two or more such aortic blood pressure measuring tubes, for example, Figure 16CFor some applications, computer processor 25 determines whether the opening of one of the two or more aortic blood pressure measurement tubes is blocked based on the blood pressure measured within each aortic blood pressure measurement tube. This may occur, for example, due to the opening contacting the wall of the aorta. Typically, in response to determining that the opening of one of the two or more aortic blood pressure measurement tubes is blocked, the computer processor determines the subject's aortic pressure based on the blood pressure measured within a different one of the two or more aortic blood pressure measurement tubes.

[0640] For some applications, the ventricular assist device includes both left ventricular blood pressure measuring tubing and aortic blood pressure measuring tubing, both of which extend to the outer surface of tube 24, e.g., as Figure 16C As shown in .

[0641] Still refer to Figure 16C As described above, for some applications, a 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 the first outer tube 140 and the second outer tube 142, as described above. For some applications, one or more blood pressure measurement tubes are disposed within the outer tube 142, surrounding the drive cable. For some applications, as shown, portions of the one or more blood pressure measurement tubes are defined by the wall of the outer tube 142. For some applications, within the outer tube 142, the blood pressure measurement tubes have an elliptical cross-section (as shown). Typically, this increases the cross-sectional area of the tubes relative to if the tubes had a circular cross-section. Typically, within the distal portion of each of the blood pressure measurement tubes (which extends to the opening 214), the tube has a circular cross-section. For some applications, the diameter of the distal portion of the tube is greater than 0.2 mm and / or less than 0.5 mm (e.g., 0.2 mm-0.5 mm).

[0642] like Figure 16A As shown in , for some applications, aortic blood pressure is measured using at least one aortic blood pressure measuring tube 222 that defines an opening 219 in the outer tube 142 at its distal end. 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 disposed within the tube 24, as Figure 16DAortic pressure is measured via opening 219 because the pressure within tube 24 at a location downstream of the impeller is generally equal to the aortic pressure.

[0643] like Figure 16A and Figure 16B , for some applications, outer tube 142 defines a groove 215 in a portion of the outer surface of the outer tube that is configured to be disposed within tube 24. Typically, during insertion of the ventricular assist device into the body of a subject, the portion of blood pressure measuring tube 210 that extends from within tube 24 to at least the outer surface of tube 24 is configured to be disposed within the groove such that the portion of the blood pressure measuring tube does not protrude from the outer surface of the outer tube.

[0644] Now refer to Figure 16D For some applications, the distal portion of the blood pressure measurement tube 210 is disposed on the exterior of the tube 24. For example, as shown, the blood pressure measurement tube 210 can extend from the outer tube 142 to the proximal end of the tube 24, and thereafter the blood pressure measurement tube can be built into the exterior surface of the tube 24. For some applications, one or more tubes may be provided. Figure 16D The tubes extend along the outer surface of the tube 24 in the manner shown in FIG, but these tubes extend all the way to the distal end of the tube 24 to the terminal portion 120 of the ventricular assist device. The tubes are used to expand the expandable portion of the terminal portion, as described below with reference to FIG. Figure 21C described in further detail.

[0645] Although the reference Figures 16A-16D The ventricular assist device described has been described as including a blood pump configured to be positioned within the left ventricle of a subject, but for some applications, blood pressure measuring tube 210 and the techniques described herein for use with blood pressure measuring tube 210 are used with a ventricular assist device that includes a blood pump located elsewhere, such as within the subject's aorta. For some applications, substantially similar techniques are used with a right ventricular assist device. 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 measuring tube is used to measure pressure in the right ventricle and / or the pulmonary artery. For some applications, a device substantially similar to device 20 is used as a cardiac assist device by being used to pump blood in an antegrade direction from the right atrium to the right ventricle, from the vena cava to the right ventricle, from the right atrium to the pulmonary artery, and / or from the vena cava to the pulmonary artery. For some such applications, the blood pressure measuring tube is used to measure pressure in the right ventricle, vena cava, right atrium, and / or the pulmonary artery.

[0646] In general, the scope of the present invention includes applying any of the apparatus and methods described herein to a right ventricular assist device, mutatis mutandis. A right ventricular assist device typically has a construction substantially similar to that described herein and is used to pump blood from the right ventricle to the pulmonary artery, with tube 24 passing through the pulmonary artery semilunar valve. For some applications, components of apparatus 20 may be applicable to different types of blood pumps. For example, aspects of the present invention may be applicable to pumps for pumping blood from the vena cava and / or 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 may include features of the pump portion 27, impeller 50, drive cable 130, apparatus and methods for measuring blood pressure, apparatus and methods for measuring flow, and the like.

[0647] For some applications, techniques substantially similar to those described with reference to blood pressure measurement tube 210 are performed using an electrical wire extending from within blood pump tubing 24 (and typically from outside the subject's body) to the outer surface of tubing 24, such that at least the distal end of the wire is in electrical communication with the subject's blood flow outside tubing 24. The subject's blood pressure outside tubing 24 (e.g., the subject's ventricular blood pressure and / or the subject's aortic blood pressure) is measured by detecting an electrical parameter using the portion of the wire in electrical communication with the subject's blood flow outside tubing 24.

[0648] Now refer to Figure 17A 、 Figure 17B and Figure 17C , Figure 17A 、 Figure 17B and Figure 17C is a schematic diagram of outer tube 142 of ventricular assist device 20 including a Pitot tube 225 configured to measure blood flow through tube 24 of the device, according to some applications of the present invention. Figures 17A-17C The portion of the outer tube 142 shown in FIG is typically disposed within the tube 24. For some applications, a flow obstruction 226 (which is typically funnel-shaped) is configured to create a stagnation region adjacent to the stagnation pressure measurement port 227. For some applications, such as Figure 17A As shown in FIG, flow straighteners 228 are added to the outer surface of the tube 142 to remove any swirling component of the flow (which does not contribute to the axial flow rate). Figure 17B, the stagnation pressure measurement port 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 measurement port. For some applications, the stagnation pressure measurement port includes a short tube 233 that extends from the outer tube 142 within the funnel-shaped flow obstruction 226 such that the opening of the short tube 233 faces the direction of axial blood flow through the tube 24. The outer tube 142 further defines an opening 219, which is generally as described above, and which serves as a static pressure measurement port 229. The pressure within the stagnation pressure measurement port 227 and within the static pressure measurement port 229 is measured using a pressure sensor, for example, as described above with reference to Figures 16A-16D A pressure sensor is described that is disposed externally to the subject's body.

[0649] In some applications, the flow rate through tube 24 is calculated based on the pressure measurement. For example, the flow rate through tube 24 can be calculated using the following equation:

[0650]

[0651] in:

[0652] Q is the flow rate through tube 24,

[0653] C is a calibration constant that is determined empirically and takes into account factors such as impeller speed and the geometry of pressure measurement ports 227 and 229,

[0654] A is the cross-sectional area of tube 24 (excluding the area occupied by outer tube 142),

[0655] ΔP is the difference between the stagnation pressure (measured via pressure measurement port 227) and the static pressure (measured via pressure measurement port 229)

[0656] p is the fluid density of blood.

[0657] Now refer to Figure 18 , Figure 18is a schematic diagram of a ventricular assist device 20 according to some applications of the present invention, the distal end portion 120 of the device being a radially expandable atraumatic distal end portion. As described above, the ventricular assist device generally includes a tube 24 that passes through the aortic valve of a subject such that a proximal portion of the tube is disposed within the subject's aorta and a distal portion of the tube is disposed within the subject's left ventricle. 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 tube 24 pumps blood from the left ventricle into tube 24 through the one or more blood inlet openings and pumps blood out of tube 24 into the aorta through the one or more blood outlet openings. Generally, the radially expandable atraumatic distal end portion 120 is disposed within the subject's left ventricle distally relative to the one or more blood inlet openings. The distal end portion is configured to be inserted into the left ventricle in a radially constrained configuration. Typically, during insertion of the distal tip portion into the left ventricle, at least a portion of the distal tip portion is disposed within the delivery catheter 143 (e.g., Figure 1B ), and the delivery catheter maintains the distal tip portion in a radially constrained configuration. The distal tip portion is configured to assume a non-radially constrained configuration within the left ventricle of the subject, wherein at least a portion 232 of the distal tip portion is radially expanded relative to the radially constrained configuration of the distal tip.

[0658] 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 shaped so that the frame expands radially when released from a delivery catheter. Typically, the frame is covered with a biocompatible, blood-impermeable material 236, such as polyurethane, polyester, and / or silicone, which is typically configured to form a continuous surface covering the frame. For some applications, the distal tip portion further includes an atraumatic distal tip 238, which can have a similar shape to the distal tip portion 120, as described above with reference to Figure 6C and / or references below Figure 21B described.

[0659] 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 three-dimensionally separates the one or more blood inlet openings 108 from the internal structures of the left ventricle. In this manner, the radially expandable portion 232 of the distal tip portion separates the one or more blood inlet openings 108 from the interventricular septum, chordae tendineae, 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 so as to direct blood flow from the left ventricle into the one or more blood inlet openings, such as by Figure 18As indicated by arrow 240 in FIG.

[0660] Now refer to Figures 19A-19B ,Should Figures 19A-19B is a schematic diagram of a ventricular assist device 20 according to some applications of the present invention, wherein the ventricular assist device distal tip portion 120 is a radially expandable atraumatic distal tip portion. Figure 20A-Figure 20B ,Should Figure 20A-Figure 20B is a schematic diagram of a ventricular assist device 20 according to some alternative applications of the present invention, wherein the ventricular assist device distal tip portion 120 is a radially expandable atraumatic distal tip portion. Figure 19A and Figure 20A The distal tip portion is shown in its radially constrained configuration while at least partially disposed within the delivery catheter 143, and Figure 19B and Figure 20B The distal tip portion is shown in its non-radially constrained configuration. Figures 19A-19B and Figure 20A-Figure 20B The distal end portion 120 shown in FIG has the same Figure 18 The distal tip portion 120 shown in FIG. 1 may function substantially similarly to that described herein.

[0661] As described above, typically, during insertion of the distal tip into the left ventricle, at least a portion of the distal tip portion 120 is disposed within the delivery catheter 143, and the delivery catheter maintains the distal tip portion in a radially constrained configuration, such as Figure 19A and Figure 20A. For some applications, the distal tip portion is configured such 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 the 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 is shaped to converge radially in a longitudinal direction toward the distal end 246 of the distal tip portion. Typically, the delivery catheter is inserted into the vasculature of the subject via a perforation. 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 perforation during insertion of the delivery catheter through the perforation. In this manner, the delivery catheter and components of the ventricular assist device disposed therein can be inserted into the perforation without the need for pre-enlarging the perforation and without the need for a separate introducer device for facilitating insertion of the delivery catheter through the perforation. For some applications, the distal region is configured to allow percutaneous insertion of the catheter into the punctured blood vessel by placing a first guidewire through the distal region of the distal tip portion. Subsequently, by tracking the route and shape of a second guide wire that is less rigid than the first guide wire, the distal region is used to guide the catheter along an arched anatomical structure (e.g., the aortic arch). 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 perforation via a short introducer device.

[0662] For some applications, the distal tip portion 120 is configured such 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 such that the distal end is enclosed within the radially expandable portion. For example, the distal tip portion may include a spring 249 and / or an elastic material configured to retract the distal end of the distal tip portion, such as from FIG. 19A to FIG. 19B For some applications, the distal end portion is flipped so that the distal end portion becomes enclosed within the radially expandable portion of the distal tip portion. For example, from FIG. 20A to FIG. 20B The transition shows the distal end 246 of the distal tip portion 120 everting, 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 the chordae tendineae and / or from causing damage to the internal structures of the left ventricle.

[0663] refer to Figure 19BFor some applications, the distal tip portion includes a plurality of longitudinal struts 248 that are shaped to bend radially outward. Typically, the struts are made of a shape memory material, such as Nitinol. For some applications, the struts are covered with a biocompatible, blood-impermeable material 250, such as polyurethane, polyester, and / or silicone, which is generally configured to form a continuous surface covering the struts. Figure 20B For some applications, the distal tip portion includes a braided shape-memory material 260. For some applications, the braided shape-memory material is at least partially covered with a biocompatible, blood-impermeable material 262, such as polyurethane, polyester, and / or silicone, which is generally configured to form a continuous surface covering the braided shape-memory material. Alternatively, the braided shape-memory material is uncovered.

[0664] Now refer to Figure 21A 、 Figure 21B 、 Figure 21C and Figure 21D , Figure 21A 、 Figure 21B 、 Figure 21C and Figure 21D FIG. 1 is a schematic diagram of a distal tip portion 120 of a ventricular assist device 20 configured to be atraumatic, according to some applications of the present invention. Figure 21A As shown in FIG, for some applications, the distal tip portion includes a J-shaped tip 270 at its distal end. Figure 21B As shown in FIG, for some applications, the distal tip portion includes a spherical tip 272 at its distal end. Figure 21A and Figure 21B As shown in FIG, for some applications, near the J-shaped end or the ball end, the distal end portion is externally shaped to define a frustum 274. Typically, the proximal end 276 of the frustum acts as a stopper for contact with the reference Figure 6C Delivery catheter 143 is prevented from advancing past the proximal end in a manner generally similar to that described for flared portion 124 .

[0665] For some applications, the tip portion has a straightened configuration, wherein the tip portion is shaped to define a frustum extending from the proximal end of the frustum to the distal tip of the distal tip portion. Figures 6A-6C For some such applications, the tip portion has an unconstrained configuration (the configuration the tip portion is configured to assume within the ventricle (e.g., resulting from the guide wire being removed from within the tip portion)) wherein the distal portion of the frustum is shaped as a J-shaped tip, such as Figure 21A As shown in .

[0666] like Figure 21C As shown in FIG, for some applications, the outer surface of the distal tip portion includes an expandable portion 278 (e.g., a balloon) that is configured to be expanded when the distal tip portion is placed within the left ventricle of a subject. For some such applications, an inflation lumen for inflating the expandable portion is configured to pass through outer tube 142 and then along the outer surface of tube 24 and to the expandable portion of the distal tip portion. For example, the inflation lumen can be configured to be similar to that of FIG. Figure 16D The blood pressure measurement tube 210 shown in FIG is constructed in a generally similar manner, but may continue along the outer surface of the tube 24 to the distal end of the tube and then continue to the expandable portion of the distal tip portion. For some applications, the distal end of the distal tip portion includes a domed portion 280. As described above, the distal tip portion typically includes a hemostasis valve 152 at its distal end.

[0667] like Figure 21D As shown 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 radially expandable frame as shown) that is configured to self-expand when the distal tip portion is positioned within the left ventricle of the subject.

[0668] like Figure 21C and Figure 21D , 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 three-dimensionally separates the one or more blood inlet openings 108 from the internal structures of the left ventricle. 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 so as to direct blood flow from the left ventricle into the one or more blood inlet openings, as described above with reference to Figure 18 The distal tip portion 120 shown in FIG.

[0669] Now refer to Figure 22A and Figure 22B , Figure 22A and Figure 22Bis a schematic diagram of the distal tip portion 120 of the ventricular assist device 20 in an axially reinforced configuration and a non-axially reinforced configuration, respectively, according to some applications of the present invention. As described above, for some applications, the distal tip portion is configured such 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 the distal end of the delivery catheter. Typically, at least in the axially reinforced configuration of the distal tip portion, the distal region is at least semi-rigid and is shaped to converge radially in a longitudinal direction toward the distal end 246 of the distal tip portion. Typically, the delivery catheter is inserted into the vasculature of the subject via a perforation. Additionally, typically, the distal tip portion defines a lumen 122 through which the guidewire 10 is inserted, as described above. For some applications, the radially converging semi-rigid distal region of the distal tip portion is configured to act as a dilator by enlarging the perforation during insertion of the delivery catheter via the perforation. In this way, the delivery catheter and components of the ventricular assist device disposed within the delivery catheter can be inserted into the perforation without the need for pre-enlarging the perforation and without the need for a separate introducer device for facilitating insertion of the delivery catheter through the perforation. For some applications, the distal region is configured to allow percutaneous insertion of the catheter into the punctured blood vessel by placing a first guide wire through the distal region of the distal end portion. Subsequently, the distal region is used to guide the catheter along an arched anatomical structure (e.g., the aortic arch) by tracing the route and shape of a second guide wire that is less rigid 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 perforation via a short introducer device.

[0670] For some applications, the distal tip portion is made of a flexible material, such as silicone, with a spring 290 disposed about lumen 122. During insertion of the ventricular assist device into the body of a subject, a rigid or semi-rigid reinforcement element 292 (e.g., a rigid or semi-rigid tube) is placed within distal region 244 of the distal tip portion to reinforce the distal region. Figure 22A Subsequently, the reinforcing element is retracted so that the distal region of the distal tip portion becomes atraumatic (eg, resilient and flexible), as shown in FIG. Figure 22B As shown in .

[0671] Now refer to Figure 23A and Figure 23B , Figure 23A and Figure 23B2 is a schematic diagram of the distal tip portion 120 of the ventricular assist device 20 in a radially constrained configuration and a non-radially constrained configuration, respectively, according to some applications of the present invention. For some applications, the distal region 144 of the distal tip portion is shaped as a cone with slits 294 (e.g., two slits) therein. During insertion of the ventricular assist device into the body of a subject, the distal region is maintained in its conical shape by a delivery catheter 143. This configuration is Figure 23A Subsequently, when the delivery catheter is retracted, the distal region is configured to form a two-dimensional circular or elliptical shape by splitting into two semicircular 296 or semi-elliptical shapes around the slit, as shown in FIG. Figure 23B As shown in Figure 23B , the distal tip portion is generally configured to be atraumatic and 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 ventricular septum, chordae tendineae, papillary muscles, and / or the apex of the left ventricle.

[0672] Now refer to Figure 24A and Figure 24B , Figure 24A and Figure 24B 1 is a schematic diagram of the distal tip portion 120 of the ventricular assist device 20 in a radially constrained configuration and a non-radially constrained configuration, respectively, according to some applications of the present invention. For some applications, the distal region 244 of the distal tip portion is shaped as a cone with slits 294 (e.g., four slits) therein. During insertion of the ventricular assist device into the body of a subject, the distal region is maintained in its conical shape by the delivery catheter 143. This configuration is Figure 24A Subsequently, when the delivery catheter is retracted, the distal region is configured to form a three-dimensional basket shape by splitting into four arms 298 around the slit, as shown in FIG. Figure 24B (Note that the fourth arm is Figure 24B Hidden from view in . ) Figure 24B , the distal tip portion is generally configured to be atraumatic and to three-dimensionally separate the one or more blood inlet openings 108 from the internal structures of the left ventricle. In this manner, the distal tip portion separates the one or more blood inlet openings 108 from the ventricular septum, chordae tendineae, papillary muscles, and / or the apex of the left ventricle.

[0673] For some applications, the distal tip portion 120 has a pointed distal region 244, the diameter of the distal tip portion at the proximal end of the distal region being approximately equal to the diameter of the delivery catheter 143. Typically, the pointed distal region 244 has a length that is less than half the total length of the distal tip portion (e.g., less than one-quarter the total length of the distal tip portion). Additionally, typically, the pointed distal region is more flexible than the 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 guidewire is inserted therein. For some applications, the distal region is configured to curl into a J-shape (e.g., as in the embodiment of the present invention) in the absence of any external force acting on the distal region. Figure 21A shown in ).

[0674] Typically, the distal region of the distal tip portion acts as a dilator for the delivery catheter 143 to allow the catheter to be percutaneously inserted 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 arched anatomical structure (e.g., the aortic arch) by tracing the course and shape of a second guide wire that is less rigid 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.

[0675] For some applications, refer to Figure 18-24B The features of the distal tip portion 120 described and the techniques for practicing the same are similar to those described above with reference to Figures 6A-6C and / or Figure 13 The described features of the described end portion 120 and the techniques for practicing the same are combined.

[0676] Now refer to Figure 25A , Figure 25A is a schematic diagram of a first portion 160A and a second portion 160B of a coupling element configured to facilitate radial contraction (e.g., during collapse) of an impeller (e.g., impeller 50 described above) independent of other components of a ventricular assist device in accordance with some applications of the present invention. The first portion 160A and the second portion 160B are configured to become engaged with each other. The first portion is disposed on the impeller and the second portion is disposed on the frame 34, such as on the distal bearing 118 of the frame 34. Note that for illustrative purposes, the Figure 25A Only certain parts of the impeller are shown.

[0677] Also refer to Figure 25B and Figure 25C , Figure 25B and Figure 25Cis a schematic diagram of various stages of collapsing an impeller according to some applications of the present invention. For some applications, prior to collapsing an outer portion of a ventricular assist device (e.g., the frame 34 of the left ventricular assist device 20 as shown), the impeller is radially contracted by engaging portions 160A and 160B with each other and axially extending the impeller so as to radially contract the impeller. Subsequently, the outer portion of the left ventricular assist device is radially contracted. For some applications, collapsing the impeller in this manner reduces the likelihood that the impeller will become damaged during the collapse of the outer portion of the left ventricular assist device. Subsequently, when the impeller and frame are positioned in the left ventricle of the subject, the first portion and the second portion of the coupling element are separated from each other such that the impeller can move relative to the frame 34.

[0678] for Figures 25A-25C Alternatively or additionally to the collapse technique shown in , as described above, the impeller is configured to become 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 becomes collapsed by the other end of the impeller sliding along the shaft such that the impeller becomes axially elongated.

[0679] Now refer to Figure 26 , Figure 26 is a schematic diagram of a blocker 300 configured to prevent distal advancement of the impeller 50 of the ventricular assist device 20 during withdrawal of the ventricular assist device from the body of a subject, according to some applications of the present invention. As described above, typically, to withdraw the ventricular assist device from the body of the subject, the delivery catheter 143 is advanced distally over the frame 34 and impeller 50 so as to cause the frame and impeller to assume their radially constrained configuration. In some cases, there is a risk that the drive cable 130 may break when the impeller is pushed distally by the delivery catheter. For some applications, in the event of a drive cable breakage, then distal advancement of the proximal end of the impeller causes the blocker 300 to engage with the shoulder 302, thereby preventing further advancement of the proximal end of the impeller. It should be noted that the blocker is configured such that the blocker does not engage with the shoulder 302 during normal operation of the ventricular assist device (and throughout the axial reciprocating motion cycle described above).

[0680] For some applications (not shown), multiple electrodes are provided on the distal portion of the left ventricular assist device. Computer processor 25 ( Figure 1A) applies an electric current between a distal-most electrode and a proximal-most electrode, the distal-most electrode being typically configured to be positioned near the apex of the heart and the proximal-most electrode being typically configured to be positioned above the aortic valve. The conductance of the electric current between each pair of electrodes is then measured by a computer processor. For some applications, the application of the electric current and the conductance measurement are performed using techniques substantially similar to those described in the article by Cassidy et al., entitled “The Conductance Volume Catheter Technique for Measurement of Left Ventricular Volume in Young Piglets” (Pediatric Research, Vol. 31, No. 1, 1992, pp. 85-90). For some applications, the computer processor is configured to derive a real-time left-ventricular pressure-volume loop of the subject based on the conductance measurement. For some applications, the computer processor controls the rotational rate of the impeller in response to the derived pressure-volume loop.

[0681] About Reference Figure 1A-Figure 26 All aspects of the ventricular assist device 20 described, noting that although Figure 1A and Figure 1BA ventricular assist device 20 is shown in the left ventricle of a subject, but for some applications, the device 20 is placed in the right ventricle of the subject such that the device passes through the subject's pulmonary valve, and the techniques described herein are applied mutatis mutandis. For some applications, components of the device 20 may be applicable to different types of blood pumps. For example, aspects of the present invention may be applicable to pumps used to pump blood from the vena cava and / or right atrium into the right ventricle, from the vena cava and / or right atrium into the pulmonary artery, and / or from the renal vein into the vena cava. Such aspects may include features of the impeller 50, pump portion 27, features of the drive cable 130, devices and methods for measuring blood pressure, and the like. Alternatively or additionally, the device 20 and / or a portion thereof (e.g., the impeller 50, even in the absence of tube 24) may be placed in a different part of the subject's body to assist in pumping blood from that part. For example, the device 20 and / or a portion thereof (e.g., the impeller 50, even in the absence of tube 24) may be placed in a blood vessel and may be used to pump blood through the vessel. For some applications, device 20 and / or portions thereof (e.g., impeller 50, even in the absence of tube 24) are configured, mutatis mutandis, to be placed within the subclavian vein or jugular vein at the junction of the vein and the lymphatic duct and used to increase the flow of lymphatic fluid from the lymphatic vessels to the vein. Because the scope of the present invention includes use of the apparatus and methods described herein in anatomical locations other than the left ventricle and the aorta, a ventricular assist device and / or portions thereof will sometimes be referred to herein (in the specification and claims) as a blood pump.

[0682] Now refer to Figure 27A and 27B ,Should Figure 27A and 27B is a schematic diagram of a ventricular assist device 308 according to some applications of the present invention, the device including a valve 70 to prevent backflow of blood, for example, in the event of a malfunction of the impeller 50 of the ventricular assist device. Figure 1A-Figure 26 Unlike the ventricular assist device 20 described above, the ventricular assist device 308 includes an impeller disposed within the aorta and not in the left ventricle (e.g., as described in WO 18 / 078615 to Tuval, which is incorporated herein by reference). For some applications, the impeller is constructed in a manner generally similar to the impeller 50 described above. The impeller is disposed at the proximal end of a tube 312 (e.g., a polyester tube) that passes through the aortic valve, and the frame 310 supports the tube in an open configuration. Figure 27A The ventricular assist device is shown configured when its impellers are operating normally so that there is blood flow, indicated by arrow 72 , from the left ventricle 22 to the aorta 30 via tube 312 (which passes through the aortic valve 26 ).

[0683] For some applications, tube 312 includes valve 70 located at a region of the tube that is configured to be positioned distally relative to impeller 50 and proximal to the aortic valve, such as Figure 27B For example, if the impeller 50 fails so that there is a backflow of blood through the tube 312 (as indicated by Figure 27B In the event of a reverse blood flow (indicated by blood flow arrows 73 in FIG. 1 ), the leaflets of valve 70 are configured to close so that there is substantially no reverse blood flow from the aorta to the left ventricle. For some applications (not shown), tube 312 includes valve 70 at the proximal end of the tube, which is configured to be positioned in the aorta.

[0684] Now refer to Figure 28A 、 Figure 28B and Figure 28C , Figure 28A 、 Figure 28B and Figure 28C is a schematic diagram of a ventricular assist device 308 according to some applications of the present invention, the device including a safety bag 80 to prevent backflow of blood, for example, in the event of a malfunction of the impeller of the ventricular assist device. Figure 1A-Figure 26 Unlike the ventricular assist device 20 described above, the ventricular assist device 308 includes an impeller disposed within the aorta and not in the left ventricle (e.g., as described in WO 18 / 078615 to Tuval, which is incorporated herein by reference). For some applications, the impeller is constructed in a manner generally similar to the impeller 50 described above. The impeller is disposed at the proximal end of a tube 312 (e.g., a polyester tube) that passes through the aortic valve, and a frame 310 that supports the tube in an open configuration. Figure 28A The ventricular assist device is shown configured when the impeller of the ventricular assist device is operating normally, so that there is blood flow from the left ventricle 22 to the aorta 30 via the tube 312 (which passes through the aortic valve 26), which is indicated by arrow 72. For some applications, the ventricular assist device 308 includes a balloon 80 located at a region of the tube, which is configured to be positioned distally relative to the impeller 50 and near the aortic valve, as shown. Figure 28B For example, if the impeller 50 fails so that there is a backflow of blood through the tube 312 (as indicated by Figure 28B In the event of an obstruction (indicated by blood flow arrows 73 in FIG), the computer processor 25 is configured to inflate the balloon so that the tube 312 becomes obstructed and there is substantially no retrograde blood flow from the aorta to the left ventricle.

[0685] For some applications, ventricular assist device 308 includes a balloon 80 at the distal end of tube 312, which is configured to be positioned in the left ventricle, such as Figure 28C For example, if the impeller 50 fails so that there is a backflow of blood through the tube 312 (as indicated by Figure 28CIn the event of an obstruction (indicated by blood flow arrows 73 in FIG), the computer processor 25 is configured to inflate the balloon so that the tube 312 becomes obstructed and there is substantially no retrograde blood flow from the aorta to the left ventricle.

[0686] The scope of the present invention includes combining any of the apparatus and methods described herein with any of the apparatus and methods described in one or more of the following applications, all of which are incorporated herein by reference:

[0687] Tuval’s international patent application PCT / IL2017 / 051273, filed on November 21, 2017 (published as WO 18 / 096531), entitled “Blood pumps,” which claims priority to Tuval’s U.S. provisional patent application 62 / 425,814, filed on November 23, 2016;

[0688] Tuval’s International Application No. PCT / IL2017 / 051158, filed October 23, 2017 (published as WO 18 / 078615), entitled “Ventricular assist device,” which claims priority to Tuval’s U.S. Patent No. 62 / 412,631, filed October 25, 2016, and Tuval’s U.S. Patent No. 62 / 543,540, filed August 10, 2017;

[0689] Tuval’s International Patent Application No. PCT / IL2017 / 051092, filed September 28, 2017 (published as WO 18-061002), entitled “Blood vessel tube,” which claims priority to Tuval’s U.S. Provisional Patent Application No. 62 / 401,403, filed September 29, 2016;

[0690] US 2018 / 0169313 to Schwammenthal, which is the U.S. national phase application of Schwammenthal’s International Patent Application No. PCT / IL2016 / 050525, filed May 18, 2016 (published as WO 16 / 185473), entitled “Blood pump,” which claims priority to Schwammenthal’s U.S. Provisional Patent Application No. 62 / 162,881, filed May 18, 2015, entitled “Blood pump”;

[0691] US 2017 / 0100527 to Schwammenthal, which is the U.S. national phase of Schwammenthal’s International Patent Application No. PCT / IL2015 / 050532, filed May 19, 2015, and entitled “Blood pump,” published as WO 15 / 177793, which claims priority to Schwammenthal’s U.S. Provisional Patent Application No. 62 / 000,192, filed May 19, 2014, and entitled “Blood pump”;

[0692] Schwammenthal’s U.S. Patent No. 10,039,874, which is the U.S. national phase of Schwammenthal’s International Patent Application No. PCT / IL2014 / 050289, filed on March 13, 2014, and entitled “Renal pump,” published as WO 14 / 141284, which claims priority to: (a) Schwammenthal’s U.S. Provisional Patent Application No. 61 / 779,803, filed on March 13, 2013, and entitled “Renal pump,” and (b) Schwammenthal’s U.S. Provisional Patent Application No. 61 / 914,475, filed on December 11, 2013, and entitled “Renal pump”;

[0693] Tuval’s U.S. Patent No. 9,764,113, entitled “Curved catheter,” issued September 19, 2017, which claims priority to Tuval’s U.S. Provisional Patent Application No. 61 / 914,470, filed December 11, 2013, entitled “Curved catheter,” and

[0694] Tuval’s U.S. Patent No. 9,597,205 is the U.S. national phase of Tuval’s International Patent Application No. PCT / IL2013 / 050495, filed on June 6, 2013, and entitled “Prosthetic renal valve,” published as WO 13 / 183060, which claims priority to Tuval’s U.S. Provisional Patent Application No. 61 / 656,244, filed on June 6, 2012, and entitled “Prosthetic renal valve.”

[0695] Those skilled in the art will recognize that the present invention is not limited to what has been particularly shown and described hereinabove. Rather, the scope of the present invention includes combinations and subcombinations of the various features described hereinabove, as well as variations and modifications of the present invention that are not in the prior art and that would occur to those skilled in the art upon reading the foregoing description.

Claims

1. A device, comprising: A ventricular assist device, comprising: an impeller configured to be placed within a left ventricle of a subject, the impeller comprising a proximal hub and a distal hub; a frame configured to be disposed about the impeller, the frame including a proximal bearing and a distal bearing; an axial shaft configured to pass through the proximal and distal bearings of the frame and the proximal and distal bushings of the impeller; a motor configured to drive the impeller to pump blood from the left ventricle of the subject to the aorta by rotating the impeller, wherein the impeller is configured to perform axial back-and-forth motion relative to the frame in response to cyclic changes in a pressure differential between the left ventricle and the aorta, and wherein the impeller is coupled to the axial shaft such that the impeller causes the axial back-and-forth motion of the axial shaft relative to the proximal and distal bearings of the frame; and a distal tip element disposed at a distal end of the ventricular assist device, the distal tip element defining: an axial shaft receiving tube configured to receive at least a portion of the axial shaft during forward movement of the axial shaft; and A distal tip portion is disposed distally of the axial shaft receiving tube, the distal tip portion being configured not to injure tissue of a subject even if the distal tip portion contacts the tissue.

2. The apparatus of claim 1 , further comprising an axial motion drive configured to actively drive the impeller and the axial shaft in axial back-and-forth motion during operation of the impeller.

3. The device according to claim 1, wherein The impeller and the axial shaft are configured to passively move back and forth axially during operation of the impeller due to changes in the pressure differential against which the impeller pumps.

4. The apparatus according to claim 1, further comprising: a sensor configured to detect an indication of axial movement of the impeller and configured to generate a sensor signal in response thereto; as well as A computer processor is configured to receive the sensor signal and to generate an output in response thereto.

5. The apparatus according to claim 1, further comprising: a magnet, the impeller being coupled to the magnet such that axial movement of the impeller causes axial movement of the magnet; a sensor configured to detect magnetic flux generated by the magnet and to generate a sensor signal in response thereto; as well as A computer processor is configured to receive the sensor signal and to generate an output in response thereto.

6. The apparatus according to claim 1, wherein The distal tip portion defines a lumen extending therethrough.

7. The apparatus according to claim 6, wherein The apparatus is configured for use with a guidewire, wherein the ventricular assist device is configured to be inserted over the guidewire, and wherein the lumen is configured to receive the guidewire.

8. The apparatus according to claim 7, wherein The distal tip portion includes a hemostatic valve at a distal end of the lumen such that the distal tip portion becomes sealed after the guidewire is retracted from the lumen.

9. The apparatus according to claim 8, wherein The hemostatic valve is configured to prevent blood from flowing into the lumen.

10. The apparatus according to claim 1, wherein The axial shaft is configured to clean interfaces between the axial shaft and the proximal and distal bearings by moving axially back and forth relative to the proximal and distal bearings.

11. The apparatus according to claim 1, wherein The axial shaft is configured to reduce heat buildup at interfaces between the axial shaft and the proximal and distal bearings by axially moving back and forth relative to the proximal and distal bearings, relative to if the axial shaft does not move back and forth axially relative to the proximal and distal bearings.

12. The apparatus according to claim 1, wherein The ventricular assist device is configured to pump blood from the left ventricle of the subject via a tube to the subject's aorta.

13. The apparatus according to claim 12, wherein The distance from the impeller to the distal tip portion is within 50 percent of the distalmost portion of the tube throughout the entire back-and-forth axial motion cycle of the impeller.

14. The apparatus according to claim 12, wherein The impeller is configured to pump blood from the left ventricle of the subject into at least one blood inlet opening defined by the tube and configured to be placed within the left ventricle of the subject, and wherein the distal tip portion is configured to separate the at least one blood inlet opening from structures of the left ventricle of the subject.

15. The apparatus according to claim 14, wherein The atraumatic distal tip portion is configured to separate the at least one blood inlet opening from structures of the subject's left ventricle, including the ventricular septum, chordae tendineae, papillary muscles, and the apex of the subject's left ventricle.

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