Catheter pump

A heart pump and a catheter assembly therefor are provided that include a flexible catheter body having a proximal end and a distal end, the catheter body having a plurality of lumens therethrough. The catheter body can be sufficiently flexible to extend from a peripheral access to a patient's heart. The catheter assembly can also include an impeller assembly having an impeller and a housing. The impeller assembly can be coupled with the flexible catheter body such that a tensile force applied to opposite ends of the catheter assembly enhances the security of the connection between the catheter body and the impeller assembly.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This application is directed to heart pumps that can be applied percutaneously.

2. Description of the Related Art

Heart disease is a major health problem that claims many lives per year. After a heart attack, only a small number of patients can be treated with medicines or other non-invasive treatment. However, a significant number of patients can recover from a heart attack or cardiogenic shock if provided with mechanical circulatory support.

In a conventional approach, a blood pump having a fixed cross-section is surgically inserted a heart chamber, such as into the left ventricle of the heart and the aortic arch to assist the pumping function of the heart. Other known applications involve providing for pumping venous blood from the right ventricle to the pulmonary artery for support of the right side of the heart. The object of the surgically inserted pump is to reduce the load on the heart muscle for a period of time, which may be as long as a week, allowing the affected heart muscle to recover and heal. Surgical insertion, however, can cause additional serious stresses in heart failure patients.

Percutaneous insertion of a left ventricular assist device (“LVAD”), a right ventricular assist device (“RVAD”) or in some cases a system for both sides of the heart (sometimes called biVAD) therefore is desired. Conventional fixed cross-section ventricular assist devices designed to provide near full heart flow rate are too large to be advanced percutaneously, e.g., through the femoral artery. There is an urgent need for a pumping device that can be inserted percutaneous and also provide full cardiac rate flows of the left, right, or both the left and right sides of the heart when called for.

SUMMARY OF THE INVENTION

In one embodiment, a heart pump is provided that includes a catheter assembly and an impeller assembly. The catheter assembly comprises a proximal end, a distal end, and an elongate body extending therebetween. The impeller is coupled with the elongate body. The impeller assembly comprises an impeller shaft and an impeller disposed on the impeller shaft. The heart pump also includes a bearing disposed between the proximal end of the impeller shaft and the distal end of the catheter assembly. The heart pump can optionally include a second bearing disposed between the first bearing and the proximal end of the catheter assembly. One or more bearings supporting the impeller shaft can be a hydrodynamic bearing. The heart pump also includes an infusant inflow port disposed distal of the bearing or between the first and second bearing (where provided) and configured to direct infusant toward the impeller shaft.

In another embodiment, a heart pump is provided that is configured to be applied percutaneously. The heart pump includes an impeller assembly and a catheter assembly comprising a proximal end, a distal end, and an elongate body extending therebetween. The impeller assembly includes an impeller shaft and an impeller disposed on the impeller shaft. The heart pump includes at least one bearing that supports the impeller assembly. The impeller bearing is configured to support the impeller assembly in a pressure-velocity range of about 20,000-50,000 psi-ft/min.

In other embodiments, the impeller bearing is configured to support the impeller assembly in a pressure-velocity range of about 35,000-50,000 psi-ft/min. However, even higher pressure-velocity ranges may be called for in certain embodiments, for example at least about 50,000 psi-ft/min in some embodiments, at least about 20,000 psi-ft/min in some embodiments and no less than 50 psi-ft/min in other embodiments.

In another embodiment, a heart pump is configured to be applied percutaneously and includes a catheter assembly, an impeller assembly and a drive shaft. The catheter assembly comprises a proximal end, a distal end, and an elongate body extending therebetween. The elongate body has a drive lumen extending therethrough. The impeller assembly comprises an impeller shaft and an impeller disposed on the impeller shaft. The drive shaft is disposed in the drive lumen and includes a plurality of layers.

In another embodiment, a heart pump is provided that is configured to be applied percutaneously. The heart pump includes a catheter assembly and an impeller assembly. The catheter assembly has a proximal end, a distal portion, and an elongate body extending therebetween. The distal portion has an expandable housing. The impeller assembly includes an impeller shaft and an impeller disposed on the impeller shaft. The impeller shaft is supported in the distal portion of the catheter assembly such that the impeller can be positioned in the expandable housing. At least the impeller comprises a layer disposed on a surface that is exposed to blood when the heart pump is inserted into the patient and operating. The layer is configured to enhance biocompatibility of the pump.

In another embodiment, a heart pump is provided that is configured to be applied percutaneously. The heart pump includes a catheter body and an impeller. The impeller includes a shaft and at least one blade coupled with the impeller. The impeller is rotated about a rotational axis and the blade extends radially outward from the rotational axis. A radially outermost portion has a rounded configuration. The rounded configuration eliminates sharp edges between at least one of a leading edge of the impeller blade, a radial end of the impeller blade, and a trailing edge of the impeller blade. In one embodiment, the rounded configuration provides a continuous curved profile from the leading edge to the trailing edge of the impeller blade.

In another embodiment, a catheter assembly for a heart pump is provided that can include a flexible catheter body having a proximal end and a distal end and defining a plurality of lumens therethrough. The catheter body can be sufficiently flexible to extend from a peripheral access to a patient's heart. The catheter assembly can also include an impeller assembly having an impeller and a housing. The impeller assembly can be coupled with the flexible catheter body such that a tensile force applied to opposite ends of the catheter assembly enhances the security of the connection between the catheter body and the impeller assembly.

A more detailed description of various embodiments of components for heart pumps useful to treat patients experiencing cardiac stress, including acute heart failure, are set forth below.

DETAILED DESCRIPTION

Major components of heart pumps that can be applied percutaneously to a patient are described below in Section I. Section II describes various structures that facilitate the rotatable support of a cantilevered impeller. Section III describes strategies for minimizing a patient's negative reaction to the presence of the systems within the cardiovascular system. Section IV illustrates structures for streamlined catheter assembly connections. Section V illustrates methods for use in connection with specific structures of heart pumps

I. Overview of Heart Pumps

FIG. 1illustrates one embodiment of a heart pump10that includes a catheter assembly100having a proximal end104adapted to connect to a motor14and a distal end108(seeFIG. 1A) adapted to be inserted percutaneously into a patient. The motor14is connected by a signal line18to a control module22that provides power and/or control signals to the motor14. As discussed further below, the heart pump10may have an infusion system26and a patient monitoring system30.

The infusion system26can provide a number of benefits to the heart pump10which are discussed below. In one embodiment, the infusion system26includes a source of infusant34, a fluid conduit38extending from the infusant source34to the proximal end104of the catheter assembly100and a fluid conduit42extending from the proximal end of the catheter assembly100to a waste container46. The flow of infusant to and from the catheter assembly100can be by any means, including a gravity system or one or more pumps. In the illustrated embodiment, the infusant source34includes an elevated container50, which may be saline or another infusant as discussed below. Flow from the elevated container50can be regulated by a pressure cuff54to elevate the pressure of the fluid in the container50to increase flow or by a pinch valve58or by other means.

The patient monitoring system30can be used to monitor the operation of the patient and/or the pump10. For example, the patient monitoring system30can include a user interface60coupled with a source of data64. The data source64can include one or more patient conditions sensors, such as pressure sensors68that are in pressure communication with the patient and/or operating components within the patient. In one embodiment, the pressure sensors68fluidly communicate by a conduit72that extends between the sensors and a proximal portion of the catheter assembly100. The conduit72can include a plurality of separable segments and can include a valve76to enable or disable the pressure communication to the sensors68.

The heart pump10is adapted to provide an acute or other short-term treatment. A short-term treatment can be for less than a day or up to several days or weeks in some cases. With certain configurations the pump10can be used for a month or more.

The catheter assembly100extends between the proximal end104and the distal end108. An impeller assembly116disposed at the distal end108is configured to pump blood to convey blood from one body cavity to another. In one arrangement, the impeller assembly116conveys blood proximally through or along a portion of the catheter assembly100to provide assistance to the left ventricle of the heart. In another embodiment, the impeller assembly116conveys blood distally through or along a portion of the catheter assembly100to provide assistance to the right ventricle of the heart. The heart pump10is useful as a heart assist device for treating patients with acute heart failure or other heart maladies. The heart pump10also can be used in connection with a surgical treatment to support the patient without providing full cardiovascular bypass. A patient could be supported on the device for longer term with proper controls and design.

The catheter assembly100is provided with a low profile configuration for percutaneous insertion. For example, the distal end108of the catheter assembly100can be configured to have about an 11 French (approximately 3.5 mm) size in a first configuration for insertion and an expanded configuration, such as up to about 21 French (approximately 7 mm), once positioned in the body. The larger size facilitates greater flow rates by the impeller assembly116as discussed below.

The catheter assembly100is configured to enable the distal end108to reach a heart chamber after being inserted initially into a peripheral vessel. For example, the catheter assembly100can have a suitable length to reach the left ventricle and sufficient pushability and torquability to traverse the intervening vasculature. The catheter assembly100may include a multilumen catheter body120that is arranged to facilitate delivery and operation of the impeller assembly116. Further details concerning various embodiments of the catheter body120are discussed below in connection withFIGS. 7-7C.

A drive system is provided to drive an impeller within the impeller assembly116. The drive system includes a motor14and a suitably configured drive controller (not shown). The motor14may be configured to be disposed outside the patient, e.g., adjacent to the proximal end104of the catheter assembly100. In one advantageous embodiment, the drive system employs a magnetic drive arrangement. The motor14is arranged to generate magnetic fields that will be sensed by permanent magnets disposed within the proximal end104of the catheter assembly100. This arrangement facilitates very efficient generation of torque used to drive the impeller assembly116, as discussed below.

Some embodiments described herein could be incorporated into a system in which a motor is miniaturized sufficiently to be inserted into the patient in use, including into the vasculature. Such an embodiment could be operated by disposing control signal lines within the proximal portion of the catheter body120. Also, it may be useful to provide the capability to measure blood pressure at the distal end108using a device disposed at the proximal end104. For example, a pressure sensor at the distal end can communicate with a device outside the patient through a lumen of the catheter body120. Various details of these optional features are described in U.S. Pat. No. 7,070,555, which is incorporate by reference herein in its entirety and for all purposes.

In another embodiment, a mechanical interface can be provided between the motor and the proximal end104of the catheter assembly100. The mechanical interface can be between the motor14and a drive shaft positioned at the proximal end of the catheter assembly100.

A torque coupling system is provided for transferring torque generated by the drive system to the impeller assembly116. The torque coupling system is discussed further in Section II(C)—Torque Coupling System (as discussed below), but in general can include magnetic interface between the motor14and a drive assembly146disposed at the proximal end104of the catheter assembly100. The drive assembly146is coupled with a proximal end of an elongate drive shaft148in one embodiment. The drive shaft148extends between the drive assembly146and the impeller assembly116. A distal portion of the drive shaft148is coupled with the impeller assembly116as discussed below in connection with one embodiment illustrated inFIGS. 4A and 4B.FIG. 11shows one manner of coupling the proximal end of the drive shaft148with the drive assembly146.

As discussed above, the heart pump10may also include an infusion system26.FIG. 1Ashows that the infusion system26can include an infusion inflow assembly150provided adjacent to the proximal end104in one embodiment. The infusion assembly150can be one component of an infusion system that is configured to convey one or more fluids within the catheter assembly100. The fluids can be conveyed distally within the catheter assembly100, e.g., within the catheter body120, to facilitate operation of the impeller assembly116, some aspect of a treatment, or both. In one embodiment, the infusion system is configured to convey a lubricant, which, for example, can be saline, glucose, lactated Ringer's solution, acetated Ringer's solution, Hartmann's solution (a.k.a. compound sodium lactate), and D5W dextrose solution. In another embodiment, the infusion system is configured to convey a medication, or a substance that both acts as lubricant and medication. As sometimes used herein “infusant” is intended to be a broad term that includes any fluid or other matter that provides performance enhancement of a component of the heart pump10or therapeutic benefit, and can be wholly or partly extracted from the system during or after operation of the pump.

In one embodiment, the infusion inflow assembly150includes a catheter body154having a luer or other suitable connector158disposed at a proximal end thereof and an inflow port in fluid communication with one or more lumens within the catheter assembly100. A lumen extending through the catheter body154is adapted to be fluidly coupled with a fluid source connected to the connector158to deliver the fluid into the catheter assembly100and through one or more flow paths as discussed below in connection withFIGS. 4A,4B, and7-7B.

FIGS. 1A and 12show that the catheter assembly100may also include an outlet positioned at a location that is outside the patient when the heart pump10is in use to allow infusant to be removed from the pump and from the patient during or after the treatment. The outlet can be fluidly coupled with an infusant return flow path in the catheter body120through a fluid port144disposed at the proximal end104.

The catheter assembly100can also include a sheath assembly162configured to constrain the impeller assembly116in a low profile configuration in a first state and to permit the impeller assembly116to expand to the enlarged configuration in a second state. The sheath assembly162has a proximal end166, a distal end170, and an elongate body174extending therebetween. In one embodiment, the elongate body174has a lumen extending between the proximal and distal ends166,170, the lumen being configured to be slidably disposed over the catheter body120. The arrangement permits the sheath assembly162to be actuated between an advanced position and a retracted position. The retracted position is one example of a second state enabling the impeller assembly116to expand to an enlarged configuration. The advanced position is one example of a first state that enables the impeller assembly116to be collapsed to the low profile configuration. In some embodiments, a luer102or other suitable connector is in fluid communication with the proximal end166of the sheath assembly162. The luer102can be configured to deliver fluids to the catheter assembly100, such as priming fluid, infusant, or any other suitable fluid.

FIG. 1Aillustrates a retracted position, in which the distal end170of the elongate body174is at a position proximal of the impeller assembly116. In an advanced position, the distal end170of the elongate body174is positioned distal of at least a portion of the impeller assembly116. The sheath assembly162can be configured such that distal advancement of the distal end170over the impeller assembly116actuates the impeller assembly116from an enlarged state to a more compact state (or low profile configuration), e.g., causing a change from the second state to the first state, as discussed above. Although shown inFIGS. 4A & 4Bas a single layer, the elongate body174can include a multilayer construction.

FIGS. 4A & 4Bshow the elongate body174as a single layer structure from the inner surface to the outer surface thereof. In another embodiment, the elongate body174has a multilayer construction. In one arrangement, the elongate body174has a first layer that is exposed to the catheter body120and a second layer exposed that corresponds to an outer surface of the catheter assembly100. A third layer can be disposed between the first and second layers to reinforce the elongate body174, particularly adjacent to the distal end thereof to facilitate collapse of the impeller assembly116. In another construction, a reinforcing structure can be embedded in an otherwise continuous tubular structure forming the elongate body174. For example, in some embodiments, the elongate body174can be reinforced with a metallic coil.

FIG. 2show that an impeller housing202is disposed at the distal end108. The impeller housing202can be considered part of the impeller assembly116in that it houses an impeller and provides clearance between the impeller and the anatomy to prevent any harmful interactions therebetween. The housing202and the impeller are also carefully integrated to maintain an appropriate flow regime, e.g., from distal to proximal or from proximal to distal within the housing.

FIGS. 1A and 2also show that the distal end108of the catheter assembly100includes an atraumatic tip182disposed distal of the impeller assembly116in one embodiment.FIG. 1Ashows that the atraumatic tip182can have an arcuate configuration such that interactions with the vasculature are minimally traumatic. The tip182can also be configured as a positioning member. In particular, the tip182can be flexible and compliant, yet rigid enough to help in positioning the impeller assembly116relative to the anatomy. In one embodiment, the tip182is rigid enough that when it is urged against a heart structure such as the ventricle wall, a tactile feedback is provided to the clinician indicating that the impeller assembly182is properly positioned against the heart structure.

II. Impeller Rotation and Support

The impeller assembly116can take any suitable form, but in various embodiments, includes an impeller200adapted to move a fluid such as blood from an inlet to an outlet of the catheter assembly100. In certain embodiments the impeller200can be cantilevered or otherwise supported for rotation primarily at one end.

FIG. 3shows that the impeller200includes a shaft204, a central body or hub208, and one or more blades212. Particular features of the impeller blades212are discussed further below in Section III(A).

The shaft204and hub208can be joined in any suitable fashion, such as by embedding a distal portion of the shaft within the hub208. The blades212can be spaced out proximal to distal along the axis of the shaft. In some embodiments, the blades212are provided in blade rows.FIG. 9shows that the distal end of the shaft204can extend at least to an axial position corresponding to one of the blade rows. In some embodiments, the shaft204can be solid. In other embodiments, the shaft204has a lumen extending axially through the hub so that a guidewire can be passed through the catheter assembly100. Details of variations with a lumen are discussed further in U.S. application Ser. No. 12/829,359, filed Jul. 1, 2010, titled Blood Pump With Expandable Cannula, the contents of which are incorporated by reference herein in their entirety and for all purposes.

A. Infusant Delivery and Removal System

The operation and duty cycle of the impeller assembly116can be lengthened by providing a hydrodynamic bearing for supporting the shaft204. A hydrodynamic bearing can be supported by a lubricant, such as isotonic saline, which can be delivered in a continuous flow. The lubricant can be delivered through the infusion system to an outside surface of the shaft204. The infusant may be directed onto the shaft from a radially outward location. In some arrangements, the lubricant flow is controlled such that of a total lubricant volume introduced into the proximal end of the cannula, a first portion of the total volume of the lubricant flows proximally along the shaft204. In some embodiments, a second portion of the total volume flows distally along the shaft, the first volume being different from the second volume. The second portion of the total volume can be substantially equal to the total volume introduced into the proximal end of the cannula less the first volume. Thus in one embodiment, infusant can be introduced that flows both in an axial and radial direction, for example, from proximal to distal, and radially outward. A small portion of the total infusant introduced can escape from the impeller assembly but most of the total infusant flows from distal back to a proximal direction.

FIGS. 3 to 8show various structures for providing rotational support of a proximal portion of the shaft204within the distal portion of the catheter assembly100. For example, as shown inFIG. 3, a bearing assembly220can be disposed at a distal end224of the multilumen catheter body120. In one embodiment, the bearing assembly224includes a housing228(as shown inFIG. 4B) and one or more bearings configured to support the proximal portion of the shaft204. The bearing assembly224, as illustrated in more detail inFIG. 4B, includes a plurality of bearings232a,232bdisposed within the bearing housing228. As illustrated inFIGS. 16 and 18and discussed further herein, the bearing housing228can include a single bearing232a. Various materials that can be used for the bearing are discussed below.

FIG. 6shows that the bearing housing228has a lumen234extending therethrough with a proximal enlarged portion236aand a distal enlarged portion236b. The housing228comprises a shoulder defining a narrow portion240of the lumen234disposed between the enlarged portions236a,236b. The first and second bearings232a,232bcan be disposed within the enlarged portions236a,236bof the bearing housing228.

In one arrangement, the proximal end of the shaft204(e.g., as shown inFIG. 4A) is received in and extends proximally of the second bearing232b. In some embodiments, as inFIG. 18, there can be one bearing (e.g., only bearing232a), while in other embodiments both bearings232aand232bcan be used. In some embodiments, the bearing(s), e.g., bearings232aand/or232b, can be friction fit or interference fit onto the impeller shaft204. Accordingly, the shaft204can be supported for rotation by the bearings232a,232bas well as in the narrow portion240of the housing228. In embodiments where the bearing(s)232a,232bare friction or interference fit onto the shaft, the bearing(s)232a,232bcan be configured to rotate with the shaft204relative to the bearing housing228. Further, the bearing(s)232a,232bcan have a relatively large clearance with the bearing housing228. The clearance between the shaft204and the bearing housing228, at regions that are not coupled with the bearing, can be in the range of about 0.0005 to about 0.001 inch. In certain embodiments, the clearance can be within a larger range, such as at least about 0.0005 inches, about 0.001 inches or up to about 0.005 inches. In embodiments with multiple bearing(s)232a,232b, the clearance can be different for the bearings232a,232b, such as providing a larger clearance at the proximal bearing232a.

In other embodiments, such as inFIG. 5, the bearing(s)232a,232bmay not be friction or interference fit onto the shaft204. In these embodiments, the bearing(s)232a,232bmay be disposed within the bearing housing228, for example by an interference or press fit. The shaft204may then rotate with respect to the bearing(s)232a,232b, and there can be a clearance between the shaft204and the bearing(s)232a,232b. The clearance between the shaft204and the bearings232a,232bcan be in the range of about 0.0005 to about 0.001 inch. In certain embodiments, the clearance can be within a larger range, such as at least about 0.0005 inches, about 0.001 inches or up to about 0.005 inches. The clearance can be different for the bearings232a,232b, such as providing a larger clearance at the proximal bearing232a. In certain embodiments, the bearing housing228may provide a thrust surface for bearing axial loads. In other embodiments, there may be other bearings located either distally or proximally of the bearing housing228that are configured to bear axial loads. In other embodiments, the fit between the bearings232a,232band the shaft204can be tight, which can also assist in bearing axial loads in some aspects.

At least the proximal portion of the shaft204can be made of a material that will not corrode or otherwise be made to be inert when immersed in the lubricant or other infusant. The material may be one that will not corrode in isotonic saline. Suitable materials may include a wide variety of metals, including alloys, and at least saline-resistant stainless steel and nickel-based alloys. Also, the shaft204could be made as a composite to include advantageous properties of a plurality of materials. In some cases the shaft204could be formed as a polymer. The class of polymers selected would include those that can form a shaft204of a certain stiffness suitable in this application. For example, polycarbonate or PEEK could be used. In certain configurations, the polycarbonate, PEEK, or other suitable polymer can provide enhanced performance by being combined with a second material or structure. A glass or carbon filled polycarbonate or other stiff polymer could also be used.

As discussed above, a hydrodynamic bearing between the shaft204and the bearings232a,232bmay be utilized in various embodiments. In one such arrangement, a continuously replenished fluid film is provided at least between the inner wall of the bearing housing and an adjacent moving structure, such as the impeller shaft or an outer surface of a bearing. For example, the bearing housing228can be configured to permit a lubricant to be delivered therethrough into the lumen234. The bearing housing232can include a plurality of channels260disposed therein extending proximally from a plurality of ports264located at the narrow portion240of the housing228. Each port264can communicate with one of the channels260to provide fluid communication into the lumen234.

As shown inFIG. 5, the channels260can be formed in the wall of the housing228. In one embodiment, the channels260are formed as open depressions, e.g., as flutes, extending along the housing228. In this embodiment, the channels260can be enclosed by a separate structure, such as a separate outer sleeve, that is disposed around the housing228.FIG. 4Bshows that a proximal portion268of the impeller housing202can be sized to tightly fit over the outer surface of the bearing housing228, enclosing the radially outward portion of the channels260. In this arrangement, at least a portion of a flow path is formed between an outer surface of the bearing housing228and a separate outer sleeve.

Fluid communication between the port264in the bearing housing228and the infusion inflow assembly150can be by any suitable combination of lumens within the catheter assembly100. For example, in one embodiment, each of the channels260has a proximal port272that communications with an annular space274formed in the catheter assembly100. The annular space274can be formed between a plurality of separate overlaid structures in the catheter assembly100.FIGS. 4A and 4Bshow that the annular space274is formed between an outer surface278of the multilumen catheter body120and an inner surface of the proximal length268of the housing202.

Fluid communication is provided in the catheter assembly100between the space274and the infusion inflow assembly150. For example, one or a plurality of lumens282formed in the multi-lumen catheter body120can be dispersed circumferentially about the catheter body120at a peripheral circumferential region284, as illustrated inFIGS. 7-7C. The peripheral position of the lumens282enables a central area of the catheter body120to be dedicated to a central lumen286. By providing a plurality of smaller lumens282located at the periphery, a relatively large flow rate can be delivered through a relatively small circumferential band (when considered in cross-section) of the catheter body120. Each of the lumen282has a distal port290that communicates with the space274.

A proximal portion of the lumens282can take any suitable form. For example, the lumens282can communicate at their proximal end with a flow diverting structure (not shown) that is in fluid communication with the infusion inflow assembly150. As described herein, in some embodiments the lumen282can be disposed circumferentially about the central lumen286. The catheter assembly100can include a flow diverting structure or connector, e.g., disposed about the proximal end of the catheter body120that is configured to divert the infusant into the lumens282for distally directed flow therein. In other embodiments, the catheter assembly120can include a flow diverting structure disposed adjacent the distal end thereof that is configured to divert the infusant into the lumens282from the central lumen286for proximally directed flow in the lumens282.

FIG. 5includes arrows that illustrate the flow of infusant into the bearing assembly220. In one arrangement, the inflow of infusant is indicated by an arrow300which is shown pointing distally within one of the channels260of the bearing housing228. The infusant flow enters the bearing housing through the ports264. Although flow is shown in one channel260, corresponding flow may be provided in each of a plurality of channels260disposed around the central lumen234. An arrow304illustrates that at least a portion of the infusant delivered through the port264flows generally proximally within the bearing housing228in various embodiments. An arrow308illustrates that at least a portion of the infusant delivered through the port264flows generally distally within the bearing housing228in some embodiments.

FIG. 5illustrates the arrows304,308as proximally and distally directed, respectively. However, the high speed rotation of the impeller shaft204within the housing228will create a thin film of lubricant spacing the impeller shaft204from the surfaces of the bearings232a,232b. This thin film will extend all the way around the shaft204and thus each portion of the flow will have a spiral or helical flow direction.

The bearings232a,232bcan have different configurations to enhance the performance of the pump10. For example, the proximal bearing232acan be longer along the longitudinal axis of the bearing housing228than the distal bearing232b. A longer proximal bearing232ais believed to better control runout of the shaft204. Better runout control on the shaft204is believed to enhance the control of the position of the blades212relative to the housing202. Less runout reduces excessive variation in the gap between the blades212and the housing202, providing biocompatibility benefits such as reduced hemolysis.

In some embodiments, such as those inFIG. 5where the bearings232a,232bare not friction fit or interference fit onto the shaft204, the distal bearing232bhas a smaller inner diameter than the proximal bearing232a. If the shaft204has a constant diameter, the smaller inner diameter should provide greater control of angular deflection of the shaft. Controlling angular deflection can enhance relative position control of the blades212and housing202, providing blood handling benefits such as reduced hemolysis. A smaller clearance could also be provided by enlarging the diameter of the shaft204at the axial position of the distal bearing. In some embodiments, the larger inner diameter of the bearing232benables a larger volume of lubricant to flow proximally and a lesser volume to flow distally in the lumen234.

The continuous introduction of lubricant maintains a constant, predictable and durable rotational bearing state between stationary component, e.g., the bearing housing282, and a moving component, e.g., the shaft204, a component of the bearings232a,232b, or both the shaft204and a component of the bearings232a,232b. Also, continuous lubricant inflow provides a means for removing heat generated by the relative motion between the shaft204and the bearings. Also, the infusant can create fluid pressure within the catheter assembly100that can push debris generated within or by the pump10out of the bearing housing220. Enhancing the volume of infusant that flows along the path indicated by the arrow304enhances the likelihood that debris generated by or present in the pump will be removed from the proximal end rather than to be trapped inside the distal portion of the catheter assembly100.

Another technique for controlling infusant flow in the lumen234is to locate the port264between the bearings232a,232band closer to one of the bearing. For example, the ports264can be located adjacent to the proximal bearing232ain one embodiment. This provides a shorter path of egress out of the narrow portion240of the bearing housing228in the proximal direction.

Other strategies for controlling the flow of infusant within the bearing housing228include modifying a surface within one or more of the bearings232a,232b.FIG. 8shows a surface modification233provided in a bearing232ato enhance proximally directed flow. The surface modification233comprises a plurality of axially oriented grooves235in one embodiment. In another embodiment, the surface modification233includes one or more spiral grooves. The spiral grooves can be formed with a groove entrance that is substantially parallel with a flow direction of infusant between the bearings232a,232bsuch that a reduction of velocity of the flow is minimized. In one embodiment, each spiral groove includes at least about 3 turns disposed on the inner surface of the bearing between the proximal and distal ends of the bearing. In another embodiment, each spiral groove has adjacent turns that are spaced apart by a minimum pitch of 0.125 inches (3.2 mm). In another embodiment, each spiral groove has an axial density of about 32 turns per inch (about 1.3 turns per mm). The grooves are formed in the surface237of the bearing232aupon which the impeller shaft204is supported. The grooves235locally enlarge the clearance between the shaft204and the surface237so that a greater volume of infusant can flow distal-to-proximal across the bearing232a. The surface modification233reduces back-pressure limiting the distal-to-proximal flow across the bearing232a.

In other embodiments, it may be desirable to enhance distally directed flow. For example, the infusant may be provided with a fluid intended to be delivered to the patient. In such embodiments, the surface modification233can be provided on the distal bearing232b. In certain embodiments, both proximal and distal bearings232a,232bare provided with flow enhancing modifications to enhance heat transfer or purging of the bearing assembly220. In such embodiments, one of the bearings may have a greater degree of flow enhancement provided on the bearing surface.

The arrangement of the bearing assembly220can be a factor in selecting an appropriate infusant. Saline is one type of infusant, but other sufficiently biocompatible infusants could be used. Other embodiments are configured such that little or no infusant flows out of the pump into the patient. For such embodiments, other infusant fluids can be used, such as glucose.

FIG. 7illustrates further features of the catheter body120. The catheter body120comprises an inner most portion320that defines the central lumen286. The inner most portion320is disposed within, e.g., circumferentially surrounded by, the peripheral circumferential region284. A continuous outer circumferential region324can be provided around the peripheral circumferential region284to fully enclose the lumen(s)282, discussed above.

FIGS. 4A and 4Billustrate that a distal end of the inner most portion320is configured to be received and secured within a proximal portion of the lumen234within the bearing housing228.FIG. 4Billustrates that a region of overlap can be provided between a distal portion of the inner most portion320and a proximal portion of the bearing housing228. This construction provides a continuous lumen defined in part by the central lumen286of the catheter body120and in part by the lumen234of the bearing housing. Another arrangement is discussed below in connection withFIG. 16-18in which the bearing housing228and the catheter body120are joined by a coupler that enhances the sealing between infusant inflow through the lumens282and the channels260and the infusant outflow through the central lumen286. As discussed further below, this continuous lumen, also referred to as a drive lumen, can be configured to receive at least a portion of the drive shaft148and/or the shaft204and provides a space for the rotation of the shaft204of the impeller assembly116and the drive shaft148of the torque coupling system.

The physical connection between the bearing housing228and the catheter body120can be achieved in any suitable manner.FIG. 3illustrates that in one arrangement, a slideable connection is provided. In this arrangement, a rod332is provided between the bearing housing228and the catheter body120. The rod332can have any suitable configuration, but in some embodiments, the rod332has a proximal end configured to be received in a recess or lumen formed in the catheter body120and a distal end340configured to couple with the bearing housing228.FIG. 3shows that the distal end340of the rod332can be configured to engage with a feature of the bearing housing228so that a limited range of sliding is permitted.

In one embodiment, the bearing housing228has an elongate channel342configured to receive a middle portion of the rod332and an enlarged depression344located at the distal end of the channel342. The depression344has a width W that is sufficient to receive a wide distal end of the rod332. The depression344can be configured to have an axial length along the housing228that can define a range of motion of the bearing housing228relative to the catheter body120.

In one arrangement, the bearing housing228is positioned relative to the catheter body120and the rod332such that the distal portion of the rod332is located at the distal end of the depression344. Thereafter, the catheter assembly100can be manipulated such that the bearing housing228moves distally relative to the catheter body120and the rod332such that the distal portion of the rod332is located at the proximal end of the depression344. In the distal position, the impeller assembly116is located more distally than in the proximal position. As discussed further below, this enables a variety of techniques for unfurling the impeller blades212within the housing202.

Any suitable bearing can be used in the catheter assembly100. The provision of an infusant for hydrodynamic support enables a wide range of bearing materials to be used. If saline or other more corrosive infusant is used, the bearing must be carefully configured to not degrade within the expected duty cycle of the pump10. Some polymeric materials are advantageously not degraded by isotonic saline, and are acceptable materials from this perspective. Under the fluid-dynamic conditions, a hydrodynamic bearing that is supported by a biocompatible infusant such as isotonic saline is used in various embodiments. It is believed that certain polymer bearings in combination with isotonic saline can support such conditions as 35,000-50,000 psi-ft/min for an appropriate duty cycle. Other aspects that can guide the choice of bearing configurations include minimizing thermal expansion, given the heat that could be generated in the heart pump10, and minimizing moisture absorption. In some embodiments, a substantially non-swellable material (e.g., a material that absorbs little or no water) can be used for the bearing(s). Advantageously, the use of a non-swellable material can prevent distortion of the bearing, e.g., due to continued exposure to an aqueous environment. Examples of non-swellable materials include some high molecular weight polymers (e.g., having a molecular weight greater than 10,000 Daltons).

Any suitable polymeric material may be used for the bearings232a,232b. The polymeric material can include a homopolymer, a copolymer, or a mixture of polymers. The polymeric material can include thermoplastic or thermoset polymers. Examples of polymers that can be used for bearings232a,232binclude, but are not limited to, one or more of a polyketone, a polyether, a polyacetal, a polyamide-imide, a polyacetal, polyether ether ketone (PEEK), polytetrafluoroethylene (PTFE), and polyphenylene sulfide (PPS). In some embodiments, at least one bearing is a PEEK bearing.

The polymeric material can also include (e.g., can be mixed, combined, and/or filled with) one or more additives such as a reinforcer and a lubricant. Specific additives include, but are not limited to, graphite, carbon fiber, glass fiber, and PTFE. Those of ordinary skill in the art may appreciate that the additives may be polymeric or non-polymeric. In some embodiments, the polymeric material used for bearings232aand/or232bcan include PEEK, carbon fiber, PTFE, and graphite. In other embodiments, the polymeric material can include PPS and glass fiber. In yet other embodiments, the polymeric material can include a polyamide-imide polymer, carbon fiber, and graphite. The polymeric material can include any suitable amount of additive(s). For example, the polymeric material can include a total amount of additive(s) in the range of from about 1 wt % to about 50 wt %, based on the total weight of the polymeric material. In other embodiments, the polymeric material used for bearings232a,232bmay not include any additives.

The polymeric material chosen for bearings232a,232bcan have particular characteristics that advantageously affect the performance of the bearings. For example, in order to minimize thermal expansion caused by the heat generated in the heart pump10, a preferred material would be subject to a minimum of dimensional change, and can have a coefficient of thermal expansion in the range of from about 1.2×10−5° F.−1to about 25.2×10−5° F.−1. In other embodiments, the polymer used for bearings232a,232bhas a coefficient of friction in the range of from about 0.15 to about 0.3. In another example, in order to minimize or prevent water absorption, the selected polymeric material can have a water adsorption in the range of from about 0.01% to about 0.4% over a 24 hour period. In yet another example, the polymeric material can be suitable for high pressure and velocity performance, and can have a limiting pressure-velocity (PV) in the range of from about 20,000 psi-ft/min to about 50,000 psi-ft/min.

Of course, other bearing configurations and/or materials would be suitable under other conditions, e.g., with less corrosive infusants or if a hydrostatic or non-hydraulic bearing is used.

Another bearing configuration eliminates one of the bearings, for example, the distal bearing232b, as illustrated inFIGS. 16 and 18. The bearing232acan be friction fit, interference fit, or press fit onto the shaft204, such that the bearing232ais configured to rotate with the shaft204relative to the bearing housing220(e.g., there can be little or no clearance between the bearing232aand the shaft204). Support for the shaft204can be provided by the bearing232aand the bearing housing220. In some embodiments, there can be a clearance between the shaft204and the bearing housing228of between about 0.0005 inches and about 0.001 inches. In certain embodiments, the clearance can be within a larger range, such as at least about 0.0005 inches, about 0.001 inches or up to about 0.005 inches. For example, the lumen234extending through the housing228can be substantially constant distal of the bearing232a, e.g., sized to have proper clearance to the shaft204along that length. In this embodiment, the distal enlarged portion236bis eliminated. This configuration is simpler to manufacture and may be less costly. In this embodiment, the bearing232acan be configured as a thrust bearing to bear axial loads. For example, the bearing232acan advantageously minimize the distal and/or proximal movement of the impeller200(e.g., impeller shaft204), drive assembly146, drive shaft148, and/or elongate body408relative to the impeller housing202. Additionally, the bearing232acan be configured as a fluid journal bearing, wherein the infusant creates a hydrodynamic layer that can transfer heat during operation and reduce friction between the inner surface or wall of the bearing housing228and the outer surface of the bearing232a. In some embodiments, there can be a large clearance between the thrust bearing232aand the bearing housing228. The proximal portion of the bearing housing228can also advantageously be configured as a fluid journal bearing, wherein the infusant creates a hydrodynamic layer that can transfer heat during operation and reduce friction between the inner surface or wall of the bearing housing228and the outer surface of the impeller shaft204.

C. Torque Coupling Systems

A torque coupling system is provided to rotate the impeller200at a high rate to move blood from inside a heart camber to a location within a patient's vasculature in amounts sufficient to sustain the patient or provide treatment to the patient. The torque coupling system couples the impeller200with the motor14, which may be disposed outside the patient. It is expected that the impeller200and the drive shaft148are to be rotated at 25,000-30,000 revolutions per minute for a period of seven to ten days. To provide reliable performance under these conditions, isotonic saline or other lubricant is provided between the drive shaft148and stationary components therearound.

FIGS. 11 and 4Billustrate proximal and distal portions400,404of the drive shaft148. The proximal portion400is coupled with the drive assembly146such that rotation of the drive assembly146rotates the drive shaft148. The distal portion404of drive shaft148is coupled with the impeller shaft204such that rotation of the drive shaft148causes rotation of the impeller shaft204. The drive shaft148also includes an elongate body408that extends between the proximal and distal portions400,404. The elongate portion408comprises a lumen412extending therethrough.

The size of the elongate body408may be as small as possible to minimize the cross-sectional profile of the catheter assembly100. The cross-sectional profile of the catheter assembly100corresponds to the crossing profile of the catheter assembly, which limits where the system can be inserted into the vasculature. The lumen412is sized to permit a guidewire to be advanced therethrough in some embodiments. The use of a guidewire is optional, but may simplify insertion.

In one embodiment, the elongate body408comprises a multi-layer construction. In some embodiments, each layer can include at least one coil wire or a plurality of coil wires all wound in a same orientation. For example, a two-layer, counter-wound wire construction is particularly advantageous. A first layer (e.g., an inner layer) of the elongate body408is provided by a coiled wire of nickel-molybdenum-chromium alloy, such as 35NLT or MP35N. In other embodiments, the wire material can be MP35N LT. In one embodiment, the wire has a 0.008 inch diameter and the coil has a 5 filar right-hand wound construction. The outer diameter of the first layer may be about 0.071 inch. A second layer (e.g., an outer layer) of the elongate body408can include the same material as the first layer, disposed on the outside of the first layer. The first and second layers can be wound in the same direction, or in opposite directions. For example, in some embodiments the first layer (e.g., an inner layer) can be left-hand wound and the second layer (e.g., an outer layer) can be right-hand wound, or vice versa. In other embodiments, both the first and second layers can be left-hand wound. In yet other embodiments, both the first and second layers can be right-hand wound. The wound coil wire construction can advantageously facilitate proximal and/or distal flow of infusant along the outer layer of the elongate body408. For example, the outer layer can be constructed such that the infusant travels along the coil and/or in the direction of the winding. Those skilled in the art may appreciate that, depending on the direction of rotation of the elongate body408, the infusant flow can advantageously be directed either proximally or distally. The second layer may be a 5 filar left-hand wound construction. In one embodiment, each layer is formed using a 0.008 inch diameter wire, in the above-noted coiled configuration. In other embodiments, the elongate body408can include three or more coil wire layers, wherein the layers are wound in alternating directions. In some embodiments, the outer diameter of the second layer can be between about 0.072 inch and about 0.074 inch, while in other embodiments the diameter can be much larger or smaller. In some aspects, for example, the outer diameter of the second layer can be about 0.073 inch. The inner diameter of the elongate body408can be at least about 0.039 inch in some implementations. In some embodiments, one or more ends of the elongate body408can be welded and square cut, for example, with a 0.1 inch maximum weld length on each end. The length of the elongate body408can vary, but in some embodiments, the length can be between about 47 inches and 48 inches, for example, about 47.5 inches.

Other materials and other constructions are possible. The elongate body408can be made of other non-ferrous metals or other corrosion resistant material or constructions with appropriate modulus. Other materials that could meet the corrosion requirements include stainless steel (e.g., 302, 304, or 316). In certain embodiments, the elongate body408can have a structure that enables other materials to be used. For example varying at least one of coil layers, filars, wire diameter, and coil diameter may enable an otherwise less robust material to operate below the fatigue stress of that material.

In another embodiment, a four layer construction is provided. The four layers comprise three wire-wound layers, e.g., similar to the arrangement described above, but included a third wound layer on the outer surface of the second layer. A low friction layer can be disposed on the outside surface of the elongate body408. One material that could be used as a low-friction layer is PTFE, known commercially as Teflon®. The low-friction layer should be configured to have sufficient wear resistance, such as by selection of the appropriate PTFE material, e.g. polyphenylene sulphone-filled PTFE, and/or by insuring appropriate infusant flow is maintained during the entire duration of use of the device in order to prevent undesirable local elevated temperature of the PTFE material.

The drive shaft148operates within the multilumen catheter body120. Because the drive shaft148is rotated at a very high rate when in use within the multilumen catheter body120, the configuration of the surface forming the central lumen286is important. In various embodiments, this inner surface may have high lubricity and high wear resistance. One material that can be used for the inner surface of the catheter body120is high density polyethylene (HDPE), which provides sufficient lubricity and wear resistance. In one embodiment, the entire multilumen catheter body120is foamed of HDPE. PTFE provides good lubricity and could be used if made sufficiently wear resistant. One way to increase the wear resistance of PTFE is to impregnate it with polyphenylene sulphone (PPSO2), another is to gamma irradiate the material. One way to increase the lubricity of Polyimide materials is to impregnate it with Graphite, another is to impregnate it with Graphite and PTFE.

FIG. 4Bshows a clearance412between the elongate body408of the drive shaft148and the inner surface of the multilumen catheter body120. The clearance412may be at least about 0.005 inch. Along a diameter between opposite sides of the inner surface of the central lumen286and outer surface of the elongate body408includes about 0.010 inch of space or diametric clearance. A larger minimum clearance may be desirable if the crossing profile can be enlarged or if other structures of the catheter assembly100can be made thinner or eliminated to allow more room between the elongate body408and the central lumen286.

FIGS. 11 and 12show further details of the drive assembly146, which is disposed at the proximal end104of the catheter assembly100. The drive assembly146includes a drive housing450having a recess or cavity454disposed therein. The cavity454is configured for mounting a rotor support shaft458for rotation therein. The support shaft458has a proximal end and a distal end and a plurality of components mounted thereon. The distal end of the support shaft458has a recess462formed therein to receive a proximal end of the drive shaft148. The support shaft458may also have a lumen466disposed therein for slideably receiving a guidewire.

A rotor470is mounted on an outer surface of the support shaft458between sleeve bearings474a,474b, as shown inFIG. 12. The rotor470can take any suitable form, but in one embodiment includes an elongate magnet476disposed between proximal and distal flywheels478a,478b.

The proximal end of the support shaft458has a tapered port480for receiving the guidewire. The proximal end can be configured for engaging the motor14in some embodiments. In other embodiments, a magnetic field is induced by the motor14in a manner that creates torque and rotation of the shaft458.

An infusant outflow path482is provided within the drive assembly146. The outflow path482is provided between an outer surface of the support shaft458and an inner surface486of the distal bearing. The flow path482continues from the distal bearing474bradially outwardly along thrust surface490b. The flow path continues proximally between the outer surface of the rotor470and the inner surface defining the cavity454. The flow path482continues radially inwardly along the thrust surface490atoward the support shaft458. The flow path482continues proximally between the support shaft458and the proximal bearing474a. Proximal of the bearing474a, the flow of infusant exits the catheter assembly100through an outflow port144through which it can be directed to the waste container46or discarded. The flow path is shown in more detail inFIGS. 1,12,12A, and12B.

III. Enhancement of Biocompatibility

The heart pump10includes various features that enhance the biocompatibility of the pump. For example, the impeller200and the housing202are carefully configured to interact with the blood in a way that minimizes hemolysis. Also, the blood contacting surfaces and components of the heart pump10can be enhanced to minimize adverse effects within the patient.

The impeller200may be configured to minimize blood hemolysis when in use, while at the same time providing sufficient flow generating performance.FIG. 9illustrates some configurations in which the work performed by the impeller blades212, as defined by the flow-pressure performance, is maximized. InFIG. 9, the proximal and distal impeller blades have tips212athat can have a generally flat configuration. For example, the flat aspect of the distal tips212acan be disposed at the outermost end thereof. In another embodiment, the tips212acan have an arcuate shape about the hub208. More particularly, the arcuate shape can be a helical shape as shown inFIG. 9.

The flat end portion of the tips212aprovides a surface that is generally parallel to the inner wall of the impeller housing202. In testing, the flat tips212ahave exhibited optimal hydrodynamic performance.

The number of blades212on the impeller200can vary. For example, the impeller200can have one, two, three, four, five, six, or more total blades212. As illustrated inFIG. 2A, the impeller200can have four total blades212. In another example, the impeller200can have two total blades212. The axial orientation of the blade(s)212can vary. In some embodiments, the blades212can be arranged axially along the impeller hub208in one, two, three, or more rows. As illustrated inFIG. 9A, for example, the impeller200can include two blade rows, each row including two blades. A multiple row arrangement may be advantageous in that the maximum amount of time blood components contact the blade is less than is the case with a comparable single row blade configuration. A two row configuration can result in less contact time compared to a single row configuration. In one example, a blade in a single row configuration has an axial length L1. In the two row configuration, the axial distance from the leading edge of the forward blade to the trailing edge of the rearward blade can also be a length L1. A gap between the two blades in the two row configuration can have an axial length of G1. When flowing through the gap, the blood is not in contact with the blades. This short segment or gap of no blood contact with the blades breaks-up the contact time, which provides better handling of delicate structures of the blood. In other embodiments, the impeller200can have two blades total, the blades being arranged in a single row (e.g., wherein all of the blades are at generally the same axial position along the impeller hub208). Advantageously, an impeller200with fewer blade rows can be manufactured more easily than an impeller with a larger number of blades and/or a larger number of rows. In addition, an impeller200with fewer blade rows can be deployed and/or retrieved more easily than an impeller with additional blade rows. Note that while, in general,FIGS. 9,9A,9B-1, and9B-2are representative of certain embodiments of blades and impellers, the disclosed blades may have further features not shown to scale. For example, in some embodiments the blades wrap around the shaft such that the leading edge of each blade is off-set by a substantial amount from the trailing edge of the same blade. For example, the leading and trailing edges can be offset by at least about 10 degrees, in some embodiments up to 40 degrees. In other embodiments, the leading and trailing edges are off-set by up to 90 degrees or more. In some embodiments, a first blade had a leading edge at a first circumferential position and a trailing edge at a second circumferential position, and a second blade has a leading edge at a circumferential position between the circumferential position of the leading edge and trailing edge of the first blade.

The circumferential orientation of the blade(s)212from one row relative to another can also vary. As illustrated inFIG. 9B-1, the blades in the first blade row (e.g., blade213a-1) can be circumferentially staggered, offset, or clocked, from the blades in the second blade row (e.g., blade213a-2). In some embodiments, the blades can be fully clocked (e.g., no circumferential overlap between blades). In other embodiments, the blades can be partially clocked (e.g., some circumferential overlap between blades). In yet other embodiments, the blades in the first blade row (e.g., blade214a-1) can be aligned with the blades in the second blade row (e.g., blade214a-2), for example as illustrated inFIG. 9B-2. The clocked blades can have many advantages, such as increased flow rate, reduced friction, and/or increased ease of deployment/retrieval.

FIG. 10illustrates another embodiment of an impeller blade212′ that includes modified tips212b. The distal tips212bare rounded on suction to pressure side of the blade. The rounding of the tips212bcan result from eliminating one or more edges between the suction side surface and the pressure side surface. For example as show inFIG. 9, some embodiments provide a plurality of sharp edges between the leading edge, trailing edge, and end surface of the blades. By eliminating one or more of these sharp edges a rounded profile is provided.

Without being bound to any particular theory, it is believed that this rounding reduces fluid stress and fluid stress gradient (change in pressure and/or in strain rate per unit length of the fluid flow path) on the constituents of the fluid being pumped. The reduction of such stresses and gradient can provide a more biocompatible interaction of the pump10with blood when used as a blood pump. For example, red blood cells can be damaged by being subject to high stresses or to high stress gradients. By reducing exposure of red blood cells to these conditions, hemolysis can be reduced. These benefits can be sustained even where the blades212′ are otherwise arranged to provide equivalent flow performance to the blades212, such as by providing comparable radial width of the blades212,212′, rotation speeds, and gaps between the tip212band the inner surface of the housing202.

The configuration of the blades212′ provides the further advantage of reducing sensitivity to the gap between the tip212band the inner wall of the housing202. Where sharp edge configurations are provided, variations in the gap between the tip and the housing wall can greatly affect the flow performance of the pump10. However, by rounding the edges as in the blades212′, the variation of flow performance is much less due to changing tip gap. Because the housing202is flexible and the distal portion of the catheter assembly100is disposed in a highly dynamic environment during use this arrangement reduces perturbations in the flow characteristics within the housing202, providing an even more robust design.

A further advantage of the rounded tip design is that the lessened sensitivity to tip gap provides a better configuration for manufacturing. This arrangement permits wider manufacturing tolerances for one or both of the impeller200and the impeller housing202.

FIG. 10Aillustrates further variations of the rounded tip design that combine one or more rounded edges with a flat area212cat or adjacent the tip of the blade212″. Rounded edges extend from one end of the flat area toward the leading edge of the blade212″ and from another end of the flat area212ctoward the trailing edge of the blade212″. In variations ofFIG. 10A, the flat area212C can be combined with a single rounded edge that extends only toward the leading edge or only toward the trailing edge. One advantage of the combination of the flat area212cwith one or more rounded edges is that this combination maximizes hydrodynamic performance that would occur with a “square edged” tip while providing the benefit of a more gradual change in fluid pressure and fluid stresses resulting in better hemolytic performance that would occur with a rounded tip shape.

FIG. 9Aillustrates another embodiment of an impeller blade213athat includes modified tips213b. The tips213bare rounded on the leading edge and trailing edge of the blade. By eliminating sharp edges a rounded profile is provided in the axial direction. Rounding in this fashion provides the same general benefits as the “cross-blade” tip rounding in212b,212c. Without being bound to any particular theory, it is believed that this rounding reduces fluid stress and fluid stress gradients on the constituents of the fluid being pumped. The reduction of such stresses and gradient can provide a more biocompatible interaction of the pump10with blood when used as a blood pump. For example, red blood cells can be damaged by being subject to high stresses or to high stress gradients. By reducing exposure of red blood cells to these conditions, hemolysis can be reduced.

B. Coatings To Enhance Biocompatibility

In some embodiments, the impeller200can include an outer coating layer (not shown). In some embodiments, the outer coating layer can include one or more polymers. The one or more polymers can include a homopolymer, a copolymer, and/or a mixture of polymers. The one or more polymers can be linear, branched, or crosslinked. The one or more polymers can be thermoset or thermoplastic. In some embodiments, the one or more polymers are elastomeric. In some embodiments, the outer coating layer can be hydrophilic. Examples of suitable polymers include, but are not limited to, silicones (e.g., a siloxane), silanes (e.g., an alkyltriacetoxysilane), polyurethanes, acrylics, and fluoropolymers. One example is a siloxane polymer that has been substituted with one or more alkyl, alkoxy, and/or poly(alkyl amine) groups. Polymers suitable for the outer coating layer can be commercially available and/or synthesized according to methods known to those skilled in the art. Examples of commercially available polymers include the Dow Corning MDX line of silicone polymers (e.g., MDX4-4159, MDX4-4210). In some embodiments, the outer coating layer can also include a therapeutic agent, e.g., a drug that limits the ability of thrombus to adhere to the impeller200. One example of a suitable therapeutic agent is heparin. In some embodiments, the impeller200can include two or more coating layers.

In some embodiments, a substantial portion of the entire exposed surface of the impeller200is coated with an outer coating layer. In other embodiments, only a portion of the exposed surface of the impeller200is coated with an outer coating layer. For example, in some embodiments, one or more impeller blades212, or portions thereof, are coated with an outer coating layer.

In some embodiments, the impeller housing202can include an outer coating layer (not shown). Suitable materials for the outer coating layer of the impeller housing202include, but are not limited to, those described herein with respect to the outer coating layer of the impeller200. In some embodiments, the impeller housing202can include two or more coating layers.

In some embodiments, a substantial portion of the entire exposed surface of the impeller housing202is coated with an outer coating layer. In other embodiments, only a portion of the exposed surface of the impeller housing202is coated with an outer coating layer. In embodiments where the impeller housing202includes a plurality of openings, for example as shown inFIG. 4A, the outer coating layer can coat the impeller housing202but not the openings. In other embodiments, the outer coating layer can coat the impeller housing202and one or more openings, resulting in a substantially closed impeller housing202.

The outer coating layer can be applied to the impeller200and/or impeller housing202by methods known to those skilled in the art, such as dip, spray, or flow coating. The outer coating layer can impart one or more advantageous properties to the impeller200and/or impeller housing202. For example, in some embodiments, an impeller200that includes an outer coating layer can exhibit reduced thrombosis, reduced hemolysis, increased lubricity, and/or reduced friction as compared to an otherwise similar impeller that lacks an outer coating layer. Although not bound by theory, it is believed that application of an outer coating layer to the impeller200can reduce surface friction, which can improve hemolysis performance by reducing drag forces between the blood and the impeller blades. It is also believed that the outer coating layer can assist in the process of deployment and/or retraction by reducing the coefficient of friction between the collapsed or partially collapsed sliding components.

IV. Streamlined Catheter Assembly Connections

FIG. 13shows another embodiment of a catheter assembly500that includes an elongate catheter body524and a proximal portion540of an impeller housing that provides for enhanced securement of the connection therebetween. The elongate body524comprises a central lumen528in which a drive shaft operates and a plurality of peripheral lumens532through which infusant can be delivered, as discussed above. The impeller housing can be similar to the impeller housing202and the elongate body524can be similar to the catheter body120in many respects, which will not be repeated here.

FIG. 13shows that adjacent the distal end of the catheter assembly, there is a length over which a distal portion of the elongate body524and the proximal portion540of the impeller housing, also referred to as a hypotube, are joined. The distal portion of the elongate body524can have an outer diameter that is smaller than the inner diameter of the proximal portion540of the impeller housing, allowing the elongate body524to extend within the proximal portion540of the impeller housing. An outside surface of the elongate body524contacts an inner surface of the proximal portion540. The proximal portion540of the impeller housing can have a generally cylindrical shape, and can generally be non-expandable.

Because the drive shaft148rotates at a very high rate within the lumen528when in use, the configuration of the surface forming the lumen528is important. In some embodiments, this surface has high lubricity and high wear resistance. High density polyethylene (HDPE) can be used to form the lumen528.

At the length where the elongate body524and proximal portion504are joined, the bond between the two is very important because if the bond breaks when removing the catheter assembly500from the patient's heart, the proximal portion540of the impeller housing could be dislodged and left in the patient. The highly lubricious nature of the elongate body524can make securement of these components more difficult. The distal portion of the elongate body520and the proximal portion540can be connected using an adhesive bond such as glue. However, it may be desirable to replace or supplement such a bond with a mechanical structural engagement.

In one embodiment, the adhesive bond can be supplemented by or replaced with a mechanical engagement between the elongate body524and proximal portion540of the impeller housing. One example of such a mechanical engagement is to use one or more barbs550. As shown inFIG. 13-15, the barb(s)550can be formed at the interface between the proximal portion540of the impeller housing520and the distal portion of the elongate body524. The barbs550can be formed on the proximal portion540, for example, such that they are angled inward toward the lumen528. The shape of the barbs550can vary. For example, in some embodiments the barb can be in the shape of a generally rectangular flange. As illustrated inFIGS. 13-14, the proximal portion540of the impeller housing can include at least one row of barbs, and in one embodiment, two axial rows of barbs550. The barbs550are much closer to the proximal end of the proximal portion540than the distal end thereof. Each axial row can include one or more barbs. In some embodiments, each axial row can include two or three barbs. The barbs can be distributed about the circumference of the hypotube (e.g., the proximal portion540of the impeller housing) evenly. For example, on a hypotube having one row with three barbs, the three barbs can be about 120 degrees apart from each other. On a hypotube having two barbs in one row, the two barbs can be about 180 degrees apart from each other.

The angle at which the barbs550are formed allows the elongate body524to slide or be advanced in one direction (e.g., distally) relative to and into the proximal portion540, but prevents it from sliding or advancing in an opposite direction (e.g., proximally) relative to the proximal portion540. Thus, if a tensile force is exerted upon an end of the catheter assembly500, e.g., when attempting to remove it from a patient, the elongate body524will not become separated from the proximal portion540. More particularly, as the elongate body524is pulled in the opposite direction, the barbs550in the proximal portion540of the impeller housing engage with the outer surface of the elongate body524. As a force is applied to the elongate body524in the opposite direction of insertion, the engagement between the elongate body524and proximal portion504becomes more secure as the barbs550engage with the outer surface of the elongate body524.

In various embodiments, the barbs550are arranged to extend in a direction opposite of a direction of expected application of force. The barbs550may comprise cantilevered structures that have a free end disposed away from a connected end. As inFIGS. 13-15, the connected or fixed end can comprise an integral zone of the proximal portion540of the impeller housing. The free end extends distally, which is a direction opposite of a direction of force that is expected. As discussed above, a tensile force applied to the proximal end of the catheter body120, e.g., a tensile force, may be expected upon removal of the catheter assembly100. In other embodiments, a torsional force may be expected, for example to rotate the catheter body during advancement. For such applications, the barbs550can be oriented opposite of the direction of anticipated force. If a clockwise rotation of the catheter body120is anticipated, the barbs550can extend in a counter-clockwise direction. If a counter-clockwise rotation of the catheter body120is anticipated, the barbs550can extend in a clockwise direction. The free end can extend generally circumferentially in a direction opposite of the rotational motion of the catheter body120. The fixed end and free end in the torque transmitting barbs can be at substantially the same axial position.

AlthoughFIG. 13shows the barbs550at an angle to the outer surface of the proximal portion540, these structures could be parallel to that surface prior to assembly such that the elongate body524can be more easily inserted during assembly. Thereafter a tool can be used to bend the barbs550inwardly to dig into the outer surface of the elongate body524.

FIG. 14illustrates another embodiment in which one or more notches554are formed in the outside surface of the elongate body524. The notches554are positioned to correspond to the locations of the barbs550of the proximal portion540. The notches554allow a more secure engagement between the elongate body524and the proximal portion540. In addition, the notches provide a tactile confirmation of proper assembly in that the barbs550may initially be deformed from a pre-set angled orientation (as shown inFIG. 13) when riding over the distal portion of the elongate body524. Once the barbs550are positioned over the notches554they will spring into the pre-set angled orientation.

Advantageously, a distal portion of each barb550abuts a proximal edge of each notch554such that the proximal portion540is prevented from moving distally relative to the notches554. In particular, the barbs550dig into the notches554as a tension force is applied in opposite directions on opposite sides of the junction between the elongate body524and the impeller housing502.

FIGS. 13 and 14illustrate the barbs550spaced circumferentially on the proximal portion540of the impeller housing by about 180°. InFIG. 15, the barbs550are spaced about 120° apart from each other. In further embodiments, the inward angle of the barbs550, spacing of the barbs550circumferentially on the proximal portion540, number of barbs550and notches512can all be varied to optimize the engagement between the elongate body524and proximal portion540.

In another embodiment, a plurality of barbs550is provided on the proximal portion540of the impeller housing where each barb is formed in opposite axial directions to prevent sliding of the lumen528in either direction.

In other embodiments, a detent arrangement can be used in place of the barbs550. Still in other implementations, the barbs could be formed or placed on the distal portion of the elongate body524and the notches could be formed on the proximal portion540of the impeller housing.

FIGS. 16 and 18illustrate other embodiment of a catheter assembly600that is similar to catheter assembly100except as described differently below. In particular, the catheter assembly600provides a different manner for connecting a catheter body620and the bearing housing228. In the catheter assembly600, a distal end624of the catheter body620is spaced proximally from the proximal end228aof the bearing housing228and a coupler628is disposed between the catheter body620and the bearing housing228.

FIG. 17illustrates one embodiment of the coupler628, which has a distal end632adapted to be inserted into the bearing housing228and a proximal end636adapted to be inserted into the distal end624the catheter body620. The distal end632can have an outer diameter that is approximately equal to an inner diameter at the proximal end of the bearing housing228.FIG. 6shows that the bearing housing228can include a proximal recess640that has an enlarged diameter compared to the diameter of the enlarged portion236a.FIG. 6also shows that a shoulder648is provided between the recess640and the enlarged portion236a. The shoulder abuts a distal face644of the distal end632when the coupler628is inserted into the recess640.

The proximal end636of the coupler628may have a diameter that is less than the diameter of the distal portion632such that a shoulder648is disposed between the distal and proximal portions632,636. When assembled, a distal face of the catheter body620is advanced over the proximal portion636until the distal face of abuts the shoulder648.

Advantageously, the coupler628can be used to couple the catheter body620with the bearing housing228. A seal and some mechanical securement of the catheter body622to the coupler628and/or of the coupler628to the bearing housing228can be provided by disposing an adhesive between these components. For example an adhesive can be disposed between the outer surface of the distal portion632and the inner surface of the recess640in the bearing housing and between the outer annular surface of the proximal portion636and an inner surface of the catheter body620. The coupler628advantageously allows the bearing232ato be inserted into the bearing housing first in the enlarged portion236aprior to the securement of the coupler628within the recess640, facilitating convenient assembly. In some embodiments, a seal can be provided in place of an adhesive where securement of the catheter body and the impeller housing in the impeller assembly is provided by other means. For example, the bearing housing can be secured in the proximal portion of the impeller housing by a combination of a tight fit and a strong adhesive. The proximal portion of the impeller housing can be secured to the catheter body by a combination of adhesive and mechanical structures, such as barbs as discussed below in connection withFIGS. 13-15.

One difference between the catheter assembly600and certain variations of the catheter assembly100is that the coupler628fixes the axial position of the bearing housing228and the catheter body620. In the catheter assembly600, there is no relative axial movement between the catheter body620and the bearing housing228. This arrangement reduces the complexity of the design, providing fewer moving parts, and making it even more reliable. In contrast the catheter assembly100permits the bearing housing228to slide proximally over the outer surface278between distal and proximal positions to facilitate advancement and retraction of the impeller200relative to the housing202. In the proximal position, the annular space274is much shorter axially than in the distal position (which is illustrated inFIG. 4B).

The coupler628also includes a lumen652extending from the proximal end of the proximal portion636to the distal face644. The lumen652is adapted to receive a proximal portion of the impeller shaft204and to permit infusant to flow between the outer surface of the shaft204and the inner surface of the coupler628defining the lumen652.

Returning toFIG. 16, the catheter body620has a multilumen configuration similar to that of the catheter body120, with small peripheral lumens extending proximally and distally and being disposed in a circumferential band around a central lumen. In the catheter body620, the lumens extend to the distal end of the body620. In particular, the lumens extend through a proximal portion664, a tapered portion668, and a reduced diameter portion672of the catheter body620. In one arrangement, the central lumen660has a constant diameter through the portion664,668,672and the outer surface of the catheter body620has varying perimeters (e.g., diameters). The varying perimeter can be pre-formed or induced during assembly of the catheter body620to the proximal portion268of the housing202.

FIG. 16also shows the coupling of the proximal portion268of the housing202with the catheter body620. The perimeter of the outer surface of the distal portion672may be equal to or less than the inner perimeter or diameter of the proximal portion268. Accordingly, the distal portion672can be inserted into the proximal portion268up to the distal end of the tapered portion668. Securement between the proximal portion268and the distal portion672can be by any suitable technique, such as adhesive, mechanical interlocking as discussed above in connection withFIGS. 13-15or a combination of these connections.

FIG. 18illustrates infusant flow through the catheter assembly600. Arrow680illustrates distal flow of infusant through one of the peripheral lumens, past a portion of the outer surface of the coupler628and into the channels260of the bearing housing228. Advantageously, the coupler628can assist with directing the distal flow of infusant from the catheter body to the bearing housing228. As shown, the arrow680indicates an infusant flow out of the distal end624of the catheter body620along an outside surface of the coupler628and into the channels260that extend distally from the proximal end228aof the bearing housing228. As discussed above, the infusant inflow is directed through a plurality of ports264onto the impeller shaft204. Arrow684illustrates that a portion of the infusant flows distally between the shaft204and a bearing mounted in the bearing housing228and out of the catheter assembly600through a clearance688. The clearance688can be a space between a distal face of the bearing housing228or a bearing disposed therein and a proximal face of a portion of the impeller body or hub208. Arrow692illustrates that a portion of the infusant flows proximally along the shaft204in the bearing housing228. The proximal flow can be directed between the bearing232aand the bearing housing228and thereafter between the coupler628and the shaft204. Thus, the coupler628can advantageously direct the infusant proximally from the bearing232ato the shaft204along an inner surface of the coupler628. The proximally directed infusant then flows into a small annular space between the drive shaft148and an inner surface of the catheter body620defining the central lumen of the catheter body620.

In addition to providing a secure connection, the coupler628, and/or the housing228enhances the isolation of distally flowing infusant from proximally flowing infusant. In particular, in addition to having adhesive disposed in the interface between the outside surface of the coupler628and the inner surfaces of at least one of the bearing housing228and the catheter body620, the coupler628is elongated such that for flow along the path illustrated by arrow680to short-circuit into the proximally directed flow692, the infusant would have to penetrate the length of the coupler628defined between the proximal end of the coupler and the shoulder648. Similarly for proximal flowing infusant along the arrow692to be mixed with the distal flow of arrow680, infusant would have to traverse a substantial potion of (at least a majority of) the length of the coupler between the distal end of the coupler and the shoulder648.

Thus, the coupler628greatly simplifies constructing the catheter assembly600and improve the isolation of the inflow and outflow channels for the infusant.

Various methods and techniques are discussed above in connection with specific structures of heart pumps. The following elaborates on some aspects of these techniques and methods. The following discussion is to be read in light of and freely combined with the foregoing discussion.

Deployment, Removal, and Positioning Force Transfer

As discussed above, in various embodiments the heart pump10is inserted in a less invasive manner, e.g., using techniques that can be employed in a catheter lab. Various general techniques pertinent to the heart pump10are described in U.S. patent application Ser. No. 12/829,359, filed on Jul. 1, 2010, and entitled Blood Pump With Expandable Cannula, which is incorporated by reference herein in its entirety and for all purposes.

Because the catheter assembly100is to be delivered through a small access site (e.g., about 11 French or less) and delivered to a remote site in the patient, the method of delivering, removing, and positioning the catheter assembly may be critical. For example, the very secure connection between the catheter body524and the proximal portion540of the impeller housing enables the clinician to move (e.g., remove) the impeller housing by acting on the proximal end of the catheter assembly. A force (e.g., pulling) applied to the proximal end of the catheter assembly is transmitted by way of the barbs550(or other mechanical interface) at a location adjacent to the distal end of the catheter body524. Thus a clinician can through this method directly transfer the force to the impeller housing by acting on the catheter assembly at the proximal end remote from the impeller housing. This can minimize the chance of the impeller housing becoming disconnected from the catheter body524, e.g., upon applying a pulling force to retract the impeller assembly with an expanded cannula housing back within a sheath or in pulling the catheter body in retracting the entire device outside of the body.

In some embodiments, a clinician can deploy and remove the impeller housing through the patient's vascular system by applying a longitudinal force parallel to the axis of the catheter body524. For example, to remove the catheter body524and the impeller housing from the patient's body, in some embodiments the clinician can simply apply a force in the proximal direction of the heart pump, e.g., a tensile force, to urge the impeller housing and pump system out of the patient's body. Because the central lumen528can have high lubricity, there may be a tendency for the catheter body524to slip and become separated from the proximal portion540of the impeller housing upon application of a tensile (e.g., proximally directed) force. The implementation of the coupler, the barbs and notches, and other features are designed to prevent and minimize the probability of the catheter body to separate from the distal impeller assembly.

A mechanical interface, such as the barbs550, can be angled inwardly, as described above, such that an applied tensile force causes the barbs550to engage with the outer surface of the catheter body524as shown inFIG. 13. In other embodiments, e.g., as shown inFIG. 14, the distal end of the catheter body524can include one or more notches554configured to engage the barbs550upon application of a tensile force to the proximal end of the catheter body524. When the clinician applies a tensile force to the proximal end of the catheter body524in order to remove the impeller housing (and the remainder of the heart pump system) from the patient's body, the barbs550can mechanically engage with the proximal portion540of the impeller housing to prevent the impeller housing from becoming separated from the catheter body524. Thus, the use of a mechanical interface between the catheter body and the impeller housing can be used in methods for deploying and removing the heart pump from the patient's vascular system.

As discussed above, the barbs550can also be configured for transmitting a torsional force. This can be useful in rotating the catheter within the patient, such as when the clinician desires to position the impeller housing at a certain angle within the vascular system or heart. To position the impeller housing at a particular rotation angle, the clinician can simply apply a torsional force to the proximal end of the catheter body524. The applied torsional force can be transmitted along the catheter body524and to a mechanical interface such as the barbs550shown inFIGS. 13 and 14. As mentioned above with respect toFIGS. 13 and 14, the barbs550(or other mechanical interface) can be angularly oriented in a direction opposite that of the expected applied torsional force. For example, if a clinician is expected to rotate the proximal end of the catheter body in a clockwise direction in order to position the impeller housing at a desired angle, the barbs550may extend in a counter-clockwise orientation. When the clinician applies the clockwise torsional force to position the impeller housing within the patient's vascular system, the applied torsional force can be transmitted in a clockwise direction along the catheter body524and to the barbs550. If the barbs550are oriented in a counter-clockwise direction, then the barbs550can effectively engage the outer surface of the catheter body524(or the notches554) to transmit the clockwise torque to the proximal portion540of the impeller housing, which in turn transmits the torsional force to rotate the impeller housing by the desired angle. Of course, a skilled artisan would recognize that the barbs could be oriented in a clockwise direction as well or any other suitable orientation to resist an applied torsional and/or tensile load.

It will be apparent to those skilled in the art that various modifications and variations can be made in the present embodiments without departing from the scope or spirit of the advantages of the present application. Thus, it is intended that the present application cover the modifications and variations of these embodiments and their equivalents.