Catheter pump

A heart pump is provided that comprises an elongate catheter body, an impeller disposed at the distal end of the elongate catheter body, and one or more bearings positioned between the catheter body and the impeller. A fluid supply line for delivering infusant into the catheter is provided. A fluid return line for transporting infusant out of the catheter is also provided. A pump assembly for regulating the infusant flow along the fluid supply line and fluid return line is provided as part of an infusion system.

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 a “bi-VAD”) 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

Various systems, devices and methods are provided relating to a heart pump. In some embodiments, a heart pump is provided comprising a catheter assembly comprising a proximal end, a distal end, and an elongate body extending therebetween. The heart pump further includes an impeller disposed at a distal portion of the heart pump and an infusant flow channel disposed within the catheter assembly for directing infusant through the catheter assembly. At least one debris capturing structure including an edge is positioned along the infusant flow channel.

In some embodiments, a heart pump is provided comprising an elongate catheter body, an impeller disposed at the distal end of the elongate catheter body, and one or more bearings positioned between the catheter body and the impeller, wherein at least one of the bearings comprises a surface facing a portion of the impeller. The heart pump further includes an inflow channel disposed within the elongate catheter body for directing infusant to the surface of the bearings facing the impeller and an outflow channel for directing infusant away from the surface of the bearings. At least one debris capturing structure is positioned along the outflow channel downstream of the one or more bearings.

In some embodiments, a heart pump is provided comprising an elongate catheter body; an impeller disposed at the distal end of the elongate catheter body; one or more bearings positioned between the catheter body and the impeller; a fluid supply line for delivering infusant into the catheter; a fluid return line for transporting infusant out of the catheter; and an infusion system comprising a pump assembly for regulating the infusant flow along the fluid supply line and fluid return line.

In some embodiments, a heart pump is provided comprising an elongate catheter body; an impeller disposed at the distal end of the elongate catheter body; one or more bearings positioned between the catheter body and the impeller; an infusant delivery flow path for delivering infusant into the catheter body; an infusant return flow path for transporting infusant out of the catheter body; and a pump priming structure comprising a shunt and a valve for regulating flow through the shunt, wherein the shunt is connected between the infusant delivery flow path and the infusant return flow path.

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 describes various structures that facilitate the capture of debris within the pump. Section V describes an active pump system for maintaining desired flow or pressure. Section VI describes a valve arrangement to expel air and prime the heart pump. Section VII describes various methods and techniques in connection with 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 pump10, some of which are discussed below in Section V. 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 an 11 French (3.5 mm) size in a first configuration for insertion and an expanded configuration, such as up to about 21 French (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 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 system140is provided for transferring torque generated by the drive system to the impeller assembly116. The torque coupling system140is discussed further in Section II(C), 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 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 thererof 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 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 may include 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, which is incorporated by reference herein for all purposes and in its entirety.

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 a first volume of the lubricant flows proximally along the shaft204and a second volume flows distally along the shaft, the first volume being different from the second volume.

FIGS. 3-8show various structures for providing rotational support of a proximal portion of the shaft204within the distal portion of the catheter assembly100. For example, a bearing assembly220can be disposed at a distal end224of the multilumen catheter body120. In one embodiment, the bearing assembly220includes a housing228and one or more bearings configured to support the proximal portion of the shaft204. The bearing assembly224includes a plurality of bearings232a,232bdisposed within the bearing housing228. 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 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 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 housing232and 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, 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. 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 port264may flow generally proximally within the bearing housing228. An arrow308illustrates that at least a portion of the infusant delivered through the port264may flow generally distally within the bearing housing228.

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 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 possible 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 lumens282, 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. As discussed further below, this continuous lumen provides a space for the rotation of the shaft204of the impeller assembly116and the drive shaft148of the torque coupling system140.

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 various 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 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 may be used in some 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.

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).

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.

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 draft 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) and could be used configured with a combination of coil layers, filars, wire diameter, and coil diameter that cause the material to operate below the fatigue stress of the specific 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 has 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 formed 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 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.

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. 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 port for 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 surfaces490a. 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 be is collected in 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 distal tips212b. The distal tips212bare rounded from suction to pressure side of the blade. The rounding of the distal 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 gradients on the constituents of the fluid being pumped and on the fluid overall. 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. Debris Capturing Structures

During operation of the heart pump10, debris can be generated within the system. The debris can comprise particulate matter that is formed by the interaction of separate components of the heart pump, such as in the catheter assembly. For example, when relative motion is provided between two adjacent components in the catheter assembly, such components can contact or rub against each other, causing material to be shaved from the components, thereby generating debris in the form of particulate matter. It can therefore be desirable to remove unwanted debris from the operating components of the catheter assembly. In some aspects discussed herein, the debris is flushed out of the system. In other embodiments, the debris is captured and can remain trapped within portions of the catheter assembly configured to trap debris.

The debris that is generated by the catheter assembly of the heart pump10can flow out of the catheter assembly and into a patient, which can be disadvantageous or in some cases detrimental. Furthermore, debris that is generated by the catheter assembly of the heart pump10can detrimentally collect at particular areas within the catheter assembly of the heart pump10, thereby causing increased friction, heat and/or blockage within the catheter assembly of the heart pump10, such as in channels designed to provide lubrication or other fluid flow. Although adjacent components of the catheter assembly of the heart pump10that are in relative motion will be configured to minimize particulate generation, some of the components may operate at very high rates. For example, the impeller assembly116and the elongate drive shaft148may be rotated at between about 15,000-45,000 revolutions per minute, or between about 25,000-35,000 revolutions per minute. It may be difficult or impossible to configure the catheter assembly of the heart pump10to completely eliminate generation of particulate at these and other challenging conditions of use. Accordingly, in some embodiments it is important for the catheter assembly to provide a means to isolate and capture the debris to minimize the risk of debris flowing into a patient or interfering with the operation of the pump10, such as by blocking a channel within the heart pump.

A heart pump10is provided having a catheter assembly with one or more debris capturing structures that are advantageously designed to isolate and capture debris within the heart pump10. The debris capturing structures can be in the form of spaces or recesses that are formed within the catheter assembly of the heart pump10to capture and collect debris generated within the heart pump. In certain embodiments, one or more debris capturing structures in the form of plenums (for example, debris capturing structures519aand519b, illustrated inFIG. 13) are formed within the heart pump at select positions along an infusant flow path to minimize passage of debris into static-dynamic interfaces. In some embodiments, the debris capturing structures can also be in the form of one or more walls or baffles positioned in the pump to capture debris generated within the heart pump. The one or more debris capturing structures can be strategically positioned along the length of the pump catheter assembly, such as at points downstream or upstream of key operational components disposed within an infusant fluid path, to capture debris generated within the pump before the debris flows into such components. In some embodiments, the debris capturing structures can be positioned at locations of the pump that may be outside of a patient, such as near the proximal end of the catheter assembly of the pump. The one or more debris capturing structures are advantageously used to capture debris of all sizes, from debris particles to larger debris, to reduce the risk of blockage by the debris in the pump.

FIGS. 13 and 14illustrate cross-sectional side views of a pump catheter assembly including one or more debris capturing structures.FIG. 13illustrates a cross-sectional view of a proximal end104of the catheter assembly of the pump10including a drive housing450with bearings474aand474b, fly wheels478aand478b, and debris capturing structures519aand519bin the form of recesses.FIG. 14illustrates a cross-sectional view of a distal portion of the catheter assembly of the pump including bearing housing228with enlarged portions236aand236band debris capturing structures529aand529b. As illustrated inFIG. 14, the debris capturing structures529aand529bcan take the form of recesses and can optionally be of different sizes. The debris capturing structures529a,529bofFIG. 14can be positioned near the distal end of the catheter assembly, e.g., near bearings232a,232b. As the shaft rotates, debris can be propelled radially outward and can be captured in the debris capturing structures529a,529b. In some embodiments, the debris capturing structures529a,529bcan be spaced longitudinally along the bearing housing228and/or circumferentially about the longitudinal axis thereof. While the debris capturing structures529a,529bare shown inFIG. 14as being positioned near the bearings232a,232b, in other embodiments, the debris capturing structures529a,529bcan be positioned longitudinally along the catheter assembly at any other suitable locations for capturing debris.

FIG. 13illustrates a proximal end104of the catheter assembly of the pump including a drive housing450having internal bearings474aand474b. The proximal end104of the catheter assembly of the pump10includes a cavity for housing a rotor support shaft458for rotation therein. The support shaft458has a proximal end and a distal end, with the distal end having a recess462formed therein to receive a proximal end of a drive shaft148. A plurality of channels560extend throughout a length of the drive housing450to provide one or more fluid flow paths for delivering infusant fluids through the pump body, such as saline. Along the one or more fluid flow paths are a series of debris capturing structures519aand519bin the form of recesses that are designed to capture debris generated in the catheter assembly of the heart pump10. As the support shaft458and/or the drive shaft148rotate, the centripetal forces can cause debris (e.g., unwanted particles) to flow radially outward and into the debris capturing structures519a,519b, thereby separating the debris from the infusant.

The debris capturing structures519aand519bcomprise plenums, spaces or recesses within the catheter assembly that are configured to capture debris505generated in the heart pump. Debris505can be generated in the heart pump10due to contact between pump components. For example, debris can be generated at the interface between static and dynamic components at a bearing member and within the bearing housing, or as the catheter body is bent to accommodate the tortuous anatomy, friction between the drive shaft or drive cable and inner surface of the conduit (e.g., flush sheath) can cause debris particles to flake from the individual components. Debris505that is generated in the heart pump can then flow through the pump catheter assembly via the infusant (e.g., saline). The debris capturing structures519aand519bcan be used to capture and isolate the debris505generated in the system before the debris flows into a patient or clogs pump components.

The debris505can be separated from a liquid medium through centripetal forces generated from rotating components in the pump system such as the support shaft458or the drive shaft148. For example, rotation of the drive shaft148can create centripetal forces in the fluid that can spin/move the debris505away from the drive shaft148, where the debris can be isolated from the liquid medium and gathered at these debris capturing structures. Advantageously, according to the present application, the debris505can be collected in one or more debris capturing structures519aand519bstrategically placed in locations along the catheter assembly. For instance, the debris capturing structures519a,519bcan be placed near (e.g., downstream of) various mechanical interfaces, such as bearings and other locations where there is relative motion between parts. As a result, the debris generated by such interfaces can be sequestered before it can come into contact with other moving or small interface components of the system. As described herein, in some embodiments the debris capturing structures519a,519bcan be placed near (e.g., upstream of) particular components that benefit from an infusant flow that is substantially debris-free or has a controlled low-level amount of debris, where debris might possibly cause detrimental blockage. For example, in some embodiments, a continuous or persistent flow of infusant can be used to keep blood out of some distal components. A blockage of small passages feeding this infusant distally could result in blood being permitted to enter such distal components.

The debris capturing structures519aand519bcan comprise plenums, spaces, or recesses having sidewalls for capturing the debris505. In some embodiments, the debris capturing structures519aand519bcomprise a plurality of recesses having one or more walls that form edges. For example, the debris capturing structures519aand519bcan comprise recesses having square edges or rectangular edges. The debris capturing structures519aand519bcan assume various shapes. For example, while the debris capturing structures519aand519bcan be rectangular with edges, in other embodiments, the debris capturing structures519aand519bcan assume shapes other than square or rectangular (e.g., a portion of an upper wall of the debris capturing structures can be rounded). For example, the debris capturing structures can be semi-annular and need not have edges. Advantageously, the sidewalls and edges of the debris capturing structures519aand519bhelp to capture and trap debris505that is generated in the pump.

In addition to assuming various shapes, the debris capturing structures can assume various sizes. For example, as shown inFIG. 13, debris capturing structure519ais larger than the debris capturing structure519b. In some embodiments, the debris capturing structures can be strategically sized based on their position in the pump. For example, in portions of the pump where more debris is expected to be generated, a relatively large debris capturing structure can be provided downstream to collect the debris. In some embodiments, debris capturing structures capable of trapping larger amounts of debris can help to lengthen the duty cycle of a heart pump because the cumulative effect of debris collecting in sensitive areas would be lessened or deferred.

In some embodiments, the debris capturing structures519aand519bcan be square or rectangular, as shown inFIG. 13. The debris capturing structures519aand519bcan have a width W (e.g., as defined by a dimension extending along the longitudinal/rotational axis of the pump) and a depth D (e.g., as defined by a dimension extending radially away from the longitudinal/rotational axis of the pump). In some embodiments, the debris capturing structures519aand519bcan be formed on different sides of the support shaft458and/or drive shaft148, and can be measured by width and diameter. For example, in some embodiments, the debris capturing structures519aand519bcan have a width of between about 0.01 inches and 0.3 inches, and a diameter of between about 0.1 inches and 0.7 inches. In the illustrated embodiment inFIG. 13, debris capturing structure519ahas a width of about 0.135 inches and a diameter of about 0.4 inches, while debris capturing structure519bhas a width of about 0.05 inches and a diameter of about 0.375 inches. One skilled in the art will appreciate that the dimensions are not limited to the ranges above. For example, the diameter of the debris capturing structures could be less than 0.2 inches, so long as it is greater than the length of the normal flow path. One skilled in the art will appreciate, however, that the debris capturing structures need not be limited to the particular shapes and dimensions described herein, as other configurations are also possible. For example, the debris capturing structures can also be comprised of one or more triangular recesses where debris can be trapped in a corner of the triangle. In other embodiments, the debris capturing structures can be semi-annular or shaped like a half-donut. Or, the debris capturing structures can be combination of shapes (e.g., having sidewalls that are representative of a rectangular and a triangular top component).

In an alternate embodiment (shown inFIG. 15A), the debris capturing structures519aand519bcan include one or more baffles or walls that extend into a plenum or space to capture debris generated in the pump. The baffles can provide one or more corners or edges where debris can be trapped. In some embodiments, the baffles can form a strategic path that helps to trap debris. For example, a first baffle can be placed against a sidewall of the pump, while a second baffle can be placed adjacent and at an angle to the first baffle, thereby forming a semi-enclosed space for trapping debris.

In some embodiments, to assist in maintaining the debris in the debris capturing structures519aand519b, the debris capturing structures can include one or more veins or pin-sized voids (shown inFIG. 15B) within the sidewalls and/or baffles. Debris that is directed toward the debris capturing structures519aand519bby centripetal force can then be caught or trapped in the smaller veins or voids in the debris capturing structures.

The debris capturing structures can be strategically placed in positions along the length of the pump. In some embodiments, the debris capturing structures are placed at a downstream location of an infusant flow path. The debris capturing structures can be placed downstream of particular components (e.g., downstream from one or more bearings) where debris is likely to be generated, as well as upstream of particular components that benefit from an infusant flow that is substantially debris-free or has a controlled low-level amount of debris, where debris might possibly cause detrimental blockage. For example, in some embodiments, the debris capturing structures can be placed adjacent bearings or flywheels that may make contact with other components of the pump, thereby generating debris. In other embodiments, a flow meter may be provided at the proximal end104of the catheter assembly of the pump. Some flow meters operate with components (e.g., structures defining narrow orifices) disposed in the flow stream, which could become blocked by debris. Thus, maintaining a low level of debris or a substantially debris-free flow via the debris capturing structures may extend the life of or enhance the reliability of such flow meters. Acoustic and optical flow meters may be entirely outside the flow stream and may be much less sensitive to failure due to interacting with particulate, and thus benefit less from debris capturing structures.

In some embodiments, one or more sensors can be incorporated in the pump to detect debris blockage in the infusant flow path. The sensors can be used to assess the pressure and/or flow of infusant at certain locations of the infusant flow path to determine whether flow paths are blocked by debris. The sensors can work in conjunction with the debris capturing structures such that debris can be both detected and isolated within the pump.

In some cases, a flow of infusant out of the pump may be maintained free of debris via the debris capturing structures so as to prevent a user from falsely believing that a problem exists within the pump. For example, in embodiments wherein the pump does not include a flow meter, it is still beneficial to provide the debris capturing structures to capture debris from the infusant to prevent dirty infusant outflow into a patient, which could falsely indicate that a problem exists in the pump.

As shown inFIG. 13, in some embodiments, one or more debris capturing structures519aand519bin the form of plenums are positioned adjacent to one or more channels560that serve as flow paths within the catheter assembly of the pump. The debris capturing structures519aand519bcan be positioned along the channel flow paths themselves, thereby collecting debris505that is carried within infusant moving in the flow paths.

While conventional pumps were unlikely to have debris capturing structures519aand519balong the flow paths, especially those with rectangular edges and sidewalls, which are believed to impede continuous flow path, it is observed that even with the debris capturing structures, a continuous flow path can be maintained while providing the added advantage of debris capture. For example, as shown inFIG. 13, debris capturing structure519ais in the form of a rectangular plenum having a sidewall521that is positioned along the infusant (e.g., saline) flow path. In some embodiments, the debris capturing structure519acan be sized and shaped such that when infusant flows through the channel560, the infusant can be directed in a radially outward direction upon entering the structure519a. Debris505in the infusant will make contact with the sidewall521of the debris capturing structure519a, and will remain in the debris capturing structure. The infusant can then flow in a radially inward direction toward a fluid outlet541adjacent the debris capturing structure sidewall521. The flow of the infusant through the debris capturing structure519ais still continuous, but with the added benefit of having debris captured in the debris capturing structure519a.

As shown inFIG. 13, the debris capturing structures519aand519bare placed along the flow path created by the flow channel560. More specifically, one or more debris capturing structures can be placed adjacent any of the bearings474aand474b, fly wheels478aand478b, or inner walls of the drive housing450. WhileFIG. 13illustrates a proximal end104of the catheter assembly of the pump10having two debris capturing structures within the drive housing450, it is possible to have a single debris capturing structure or more than two debris capturing structures (e.g., three, four, five or more) in this section of the catheter assembly of the pump10.

As shown inFIG. 13, the debris capturing structures519aand519bcan be formed on all sides of the catheter assembly of the pump10, and can be formed on any side of the support shaft458and/or drive shaft148. By having multiple debris capturing structures519aand519band/or debris capturing structures on all sides of the catheter assembly of the pump, this advantageously helps capture and more evenly distribute the collected debris, thereby reducing the risk of debris overfill in the individual debris capturing structures themselves.

FIG. 14illustrates a distal portion of the catheter assembly of the pump10including a bearing housing228having enlarged portions236aand236band a lumen234extending therethrough. First and second bearings232a,232bcan be disposed within the enlarged portions236aand236bof the bearing housing228. The distal portion of the catheter assembly of the pump10further includes debris capturing structures529aand529bin the form of rectangular recesses positioned along a length of the catheter assembly.

Like the debris capturing structures inFIG. 13, the debris capturing structures529aand529bofFIG. 14are positioned along an infusant flow path. While the debris capturing structures519a,519bare illustrated inFIG. 13as being positioned near the proximal end of the catheter assembly, the debris capturing structures529a,529bcan be positioned near the distal portion of the catheter assembly and can be spaced apart circumferentially. Upon rotation of the drive shaft148and/or the impeller shaft204in the lumen234, debris will be forced radially away from the drive shaft148by centripetal force and will gather in the debris capturing structures at a particular location (e.g., adjacent bearings) within the pump. The gathered debris are, for example, collected in one of the debris capturing structures529aand529b, thereby preventing the debris from obstructing portions of the pump and/or being released into a patient.

WhileFIG. 14illustrates that the debris capturing structures529aand529bare of similar size, the debris capturing structures need not be of the same size to be effective. Moreover, the debris capturing structures529aand529bcan be staggered along the length of the catheter assembly. Such a staggering arrangement can advantageously provide an additional opportunity to capture debris along different sections of the catheter assembly of the pump10with ease.

FIG. 15Aillustrates a cross-sectional side view of a pump catheter assembly including one or more debris capturing structures with baffles. The debris capturing structures539aand539bare similar to those shown inFIG. 13, but also include one or more baffles545positioned therein. The one or more baffles545can assist in partitioning the debris capturing structures539aand539binto multiple spaces with additional edges, to further enhance capture of debris. In some embodiments, the baffles545can include apertures or veins that serve as openings for receiving debris.

FIG. 15Billustrates a baffle545as shown inFIG. 15Awith a plurality of pin holes or apertures570for assisting in collecting debris. The apertures570assist in the capture of debris. When debris particles contact the baffle545, a portion of the debris can enter into the apertures570, further helping to trap the debris in the debris capturing structures.

In general, providing multiple cavities within the debris capturing structures539a,539bwill result in a gradient of particle collection. The location of a cavity (e.g., relative to other cavities in the debris capturing structure) can be configured to increase or decrease the amount of debris that is captured in that particular cavity. For example, the fluid entering the upstream side of the debris capturing structures539awill have a first greatest concentration of debris and the conditions of the fluid flow in the cavity defined between the upstream side of the plenum539and a first baffle545may cause some of the particulate to migrate to the periphery in that space. In this arrangement the particulate is captured at the periphery as illustrated inFIG. 15A. As a result, a lesser concentration of particulate will be in the fluid flowing across the baffle545into the space defined downstream of the baffle. Due to the lesser concentration of particulate in the fluid flowing into the space defined downstream of the baffle545, a smaller amount of particulate will collect in the space defined downstream of the baffle. If more than one baffle545is provided, each successive space downstream of each successive baffle will collect less and less particulate. As a result, one option is to configure at least one of the successive baffles and spaces disposed immediately downstream of the successive baffles with a lesser particulate collecting capacity. A lesser particulate collecting capacity can be provided by reducing the depth D of successive downstream spaces, reducing the radial dimension or height H of the baffles, or both.

Debris can be permitted to remain in or can be removed from the debris capturing structures519aand519b. In some embodiments, the pump walls are provided with ports to the debris capturing structures such that debris can be directly removed from the debris capturing structures (such as via a suction or vacuum). The debris can be removed from the debris capturing structures519aand519beither when the pump is turned on or off. In other embodiments, rather than being removed from the pump, the debris can remain in the debris capturing structures for the duration of the pump use. When the pump use is completed and the catheter assembly of the pump is disposed, any trapped debris can be disposed with the catheter assembly of the pump.

In use, infusant can flow distally through the catheter assembly. At least a portion of the infusant (shown by arrows) can return proximally through the catheter assembly, for example as illustrated inFIG. 13. As described further herein, the distal flow rate and the proximal flow rate can be the same or different. In some embodiments, the distal flow rate can be greater than the proximal flow rate. A relatively greater distal flow rate can create an area of positive pressure, thus encouraging at least some infusant to exit the catheter assembly at the distal end thereof (e.g., at or near the impeller). Advantageously, this distally-directed outflow of infusant can minimize or prevent blood from entering one or more components of the catheter assembly. In addition, the distal cavity through which the infusant exits can be sized to reduce or prevent debris from exiting the catheter assembly. Rather, the debris can be contained within the catheter assembly, e.g., within one or more debris capturing structures described herein.

On its return path, once the infusant reaches the distal debris capturing structure519b, some of the debris flowing with the infusant can be forced radially outward by centripetal forces induced by the rotating drive shaft148and/or support shaft458into the debris capturing structure519b, as illustrated inFIG. 13. The infusant can then flow proximally between the bearing474band the support shaft458in a direction parallel to the longitudinal axis of the catheter. Upon reaching the fly wheel478b, the infusant can flow radially outward between the fly wheel478band the bearing474b. The infusant can then continue flowing proximally down the channels560until reaching the bearing474a. After reaching the bearing474a, the infusant can flow radially inward between the bearing474aand the fly wheel478a, and can then flow longitudinally between the support shaft458and the bearing474atoward the debris capturing structure519a.

Those skilled in the art may appreciate that some embodiments may not include a debris capturing structure. As discussed herein, the debris can be removed from the catheter assembly by suction, vacuum, and/or infusant return flow. This configuration may be particularly advantageous for embodiments including one or more disposable components. In these embodiments, debris collection and removal may not be as important, since the disposable component can be replaced before so much debris has accumulated that the operation of the heart pump10has been compromised. But for other applications where longer duty cycle is advantageous, debris capturing structures may serve a greater role.

V. Active Pump System for Maintaining Desired Flow or Pressure

The infusant in the infusion system of the heart pump system can serve various functions and provide multiple benefits. Within the pump, infusant can circulate (e.g., via lumens, channels, or spaces260,274,282,412) thereby helping to cool and lubricate portions of the pump. The circulating infusant can also help insure that any debris generated in the pump is flushed from the pump or moved to a debris capturing structure, the waste container46, or a filter, as well as assist in pressurizing hydrostatic bearings at relatively high pressures. Furthermore, providing a small amount of infusant flow from the pump and into a patient is one technique for preventing blood from entering areas of the pump that could become damaged due to contact with the blood.

It is thus desirable to maintain a circulating infusant flow into and out of the pump, while also preventing inflow of blood into certain areas of the pump. However, it is difficult to perform these multiple functions using the infusant due to the difficulty in maintaining particular flow and/or pressures of the infusant to perform these functions. For example, while a relatively high flow of infusant can be beneficial for performing functions such as flushing components or pressurizing bearings, controlling relatively high flow to prevent excess infusant from entering the patient may be difficult. It would be desirable to control infusant flow to prevent the back flow of blood into bearings and other areas of the pump. As discussed above, one technique is to cause a controlled amount of infusant flow into the patient to prevent the back flow of blood into the bearings and other areas of the pump.

With reference toFIG. 16, in order to maintain a desirable flow of infusant into the patient, while still maintain a circulating infusant flow into and out of the heart pump, an infusion system is provided that controls the flow of infusant into the heart pump through the fluid supply line612and the flow of infusant through the fluid return line614and out of the heart pump. In some embodiments, the flow in rate through the supply line612is greater than the flow out rate through the return line614, the difference corresponding to flow into a patient, which can minimize or prevent blood from entering sensitive areas of the pump. For example, infusant flows out of the device assembly proximal of the impeller assembly and distal to the catheter body at a region distal to bearing232B ofFIG. 4B, e.g., as shown by arrow643inFIG. 4B. The pump system can include one or more flow pumps that regulate the infusion inflow and outflow to provide an amount of infusant into the patient that is large enough to block blood from entering the device but small enough to not be detrimental to a patient.

In some embodiments, the infusion system comprises components for controlling input flow of infusant into the heart pump and/or output flow of infusant out of the heart pump. In some embodiments, a pump can be provided (e.g, along an infusant supply line) to control the flow of infusant into the pump system. Likewise, a pump can be provided (e.g., along an infusant return line) to control the flow of infusant out of the pump system. The flow pumps can include, but are not limited to, syringe pumps, roller pumps, and peristaltic pumps. In some embodiments, a pressure-regulating device (such as a pressure cuff or bag) can also be provided to help adjust the pressure in the system to control infusant input and/or output flow. In other embodiments, the pump system can include a combination of flow pumps or pressure-regulating devices to control the infusant flow into and out of the heart pump, and thus the amount of fluid that enters into a patient.

FIG. 16illustrates a novel heart pump system for controlling infusant input flow and infusant output flow. The infusion system600includes an infusant supply610, fluid supply line612, fluid return line614, pump assembly620, optional pressure transducers624aand/or624b, optional air detectors635aand/or635b, optional blood detector644, waste system650, and optional flow meters651aand/or651b. The fluid supply line612runs from the infusant supply610to the pump assembly620, while the fluid return line614runs from the pump assembly620to the waste system650.

The pump assembly620advantageously regulates the infusant input flow through the fluid supply line612and infusant output flow through the fluid return line614. The pump assembly620can comprise a single pump or multiple pumps (e.g., two, three or more) to control the infusant inflow and/or outflow. In some embodiments, the flow pump assembly620can include a first pump that maintains a high flow of infusant into the heart pump catheter (e.g., to pressurize the bearings) and a second pump that maintains a high flow of infusant out of the heart pump catheter (e.g., for waste disposal) such that the flow of infusant entering into a patient is desirable. In some embodiments, the flow rate of infusant into the heart pump catheter can be generally the same as the flow rate of infusant out of the heart pump catheter. Those skilled in the art may appreciate that not all of the infusant that flows into the heart pump catheter will flow back out of the heart pump catheter (e.g., because some of the infusant may be released into a patient). Advantageously, in some embodiments, the flow rate of infusant out of the heart pump can be less than the flow rate of infusant into the heart pump, to account for this drop in pressure. In yet other embodiments, the flow rate of infusant out of the heart pump can be greater than the flow rate of infusant into the heart pump. In one embodiment, the flow pump assembly620can include a single pump with two or more wheels of differing diameters, wherein each wheel is configured to provide a different flow rate. In another embodiment, the flow pump assembly620can include a single pump with two or more tubes of different inner diameters, wherein each tube is configured to provide a different flow rate.

The flow pumps in the pump assembly620can help to control either the infusant flow and/or pressure of the system. In some embodiments, the pump assembly620can be configured to maintain infusant flow values throughout the system. The pump assembly620can be programmed to maintain particular flow rates, such that in some embodiments, the pump assembly620will require little if any adjustments during operation. In some embodiments, the flow pumps in the pump assembly620can help maintain a steady-state flow of infusant in particular areas of the pump.

In other embodiments, the pump assembly620can be configured to maintain particular pressure values within the system. The pump assembly620can cooperate with pressure transducers, such as624aand624binFIG. 16, to maintain desired pressure values throughout the system. Should the pressure be higher or lower than desired, the pump assembly620can reduce or increase the infusant flow rate to achieve a desired pressure value. For example, a pressure transducer can be provided upstream and adjacent a hydrostatic bearing to ensure that the pressure at the bearing is relatively high; should the pressure be too low, the pump assembly620can increase the infusant flow rate and pressure at the bearing.

In some embodiments, the pump assembly620can be configured to maintain target pressures, which are required for specific components. For example, it may be advantageous in some instances for hydrostatic bearings to maintain a minimal target pressure in order to meet design goals. The minimal target pressure can vary depending on the clearance within the bearings, and can be achieved with the assistance of the pump assembly620. In some embodiments, a shunt path around the bearings (not shown) can optionally be provided in order to increase infusant flow rate to downstream components for lubrication and/or cooling of the downstream components, such as the drive shaft. With the pump assembly620and shunt path elements, it is possible to regulate a proper amount of infusant pressure and flow to various components in the pump system.

In some embodiments, the pump assembly620can be configured to regulate a heart pump's inlet pressure to achieve a target flow. The pump assembly620can also be configured to regulate a heart pump's outlet pressure to achieve a target return flow rate. The difference between the inlet flow of infusant into the heart pump and the outlet flow of infusant out of the heart pump is the amount of infusant that enters into a patient. Thus, using the pump assembly620advantageously allows control over the amount of infusant that enters into a patient.

In some embodiments, the pump assembly620can regulate both infusant flow values and system pressures. For example, the pump assembly620can be configured to operate at a constant speed under normal conditions, but can be sped up if inadequate pressure is detected in particular parts of the system (e.g., near bearings).

As shown inFIG. 16, the novel infusion system600includes optional pressure transducers624aand624bpositioned one or more of the fluid supply line612and fluid return line614. The pressure transducers should maintain a sterile system and provide reasonable pressure accuracy. Possible transducers include disposable IBP transducers or other physiological transducers.

The infusion system600also optionally includes one or more air detectors, e.g., air detectors635aand635b, on either or both of the fluid supply line612and fluid return line614. The air detectors635aand635bcan advantageously help to detect air entering the system for preventing air embolism in the patient, and also help to ensure that the pumping of infusant is not disrupted. In some embodiments, the air detectors635aand635bcan be clipped onto in the infusant inflow and outflow tubing. In some embodiments, the air detectors can include ultrasonic air detectors.

The infusion system600optionally includes a blood detector644positioned along the fluid return line614. The blood detector644can be used to determine whether blood has entered into components (e.g., bearing) of the blood pump, which could cause malfunctioning of the heart pump. If blood is detected by the blood detector644, the clinician may advantageously be notified to take the pump10out of service or replace the catheter assembly100. In some embodiments, blood detection can be performed by colormetric means. In some embodiments, the blood detector644can be a BLD-06 blood detector, manufactured by Introtek.

The infusion system600further includes optional flow meters651aand651bdesigned to measure the infusant flow in the fluid supply line and/or the infusant flow in the fluid return line. The flow meters651aand651bcan be in the form of drop counter sensors which can measure flow by counting drops per unit time in drip chambers. The flow meters651aand651bcan help the flow pump assembly620to adjust flow and pressure depending on the values read in the flow meters.

FIG. 16Aillustrates another embodiment of the infusion system600a. In this embodiment, the pump assembly620can include an inflow pump621aand an outflow pump621b. The inflow pump621acan be connected to the fluid supply line612and the outflow pump621bcan be connected to the fluid return line614. Advantageously, the inflow pump621aand the outflow pump621bcan be configured to operate separately and/or independently from one another. For example, the inflow pump621aand the outflow pump621bcan be configured to operate at different flow rates.

As illustrated inFIG. 16A, the air detector635a, in communication with the fluid supply line612, can be positioned within the same fluid channel as, e.g., downstream of, the inflow pump621a. Advantageously, the optional air detector635acan detect any air or bubbles that may have been introduced upstream thereof, such as where bubbles are introduced into the infusant by an upstream component, such as the inflow pump621a. The infusion system600aillustrated inFIG. 16Aadditionally includes an air detector635cthat is also in communication with the fluid supply line612and that is positioned between the pressure transducer642aand the catheter. Advantageously, this second air detector635cin communication with the fluid supply line612provides redundancy to further reduce the risk of air embolism.

The infusion system600aillustrated inFIG. 16Amay not include the blood detector644or the air detector635bon the fluid return line614. Otherwise, the infusion system illustrated inFIG. 16Acan include many, if not all, of the components and advantages of the infusion system600illustrated inFIG. 16.

Advantageously, each of the components inFIGS. 16 and 16Ahelp to control system pressure and/or fluid flow to provide a desirable infusant flow in and out of the pump system, as well as into the patient.

In addition, the novel heart pump system can include components (e.g., detectors and sensors) that serve as diagnostic tools to assess the performance of the heart pump. In some embodiments, sensors can be placed along both a fluid supply line and/or a fluid return line to detect variations in pressure and/or flow of infusant. The changes that are detected can be used to assess the performance of the heart pump (e.g., infusion system) and determine whether problems exist in the heart pump (e.g., whether there is blockage by debris or leakage). For example, if a sudden pressure drop is detected (e.g., at the fluid return line) in the heart pump, this can be an indication that a leak exists in the pump system. Or, if a sudden pressure increase is detected (e.g., at the fluid supply line) in the heart pump, this can be an indication that the infusant flow path is clogged by debris. Assessments can likewise be made with increased and decreased flow rates. In some embodiments, the assessments can be made in real-time, or with minimal delay. Advantageously, the diagnostic tools can cooperate with the pump assembly620discussed above to regulate the infusant flow and pressures based on the diagnostic assessments. For example, a decrease in flow rate at the supply or return line may indicate a blockage or a leakage in the system. In some embodiments, the detected pressure and flow measurements may be used in combination to determine the performance of the pump system. Detection via sensors of unexpected changes in pressure or flow of infusant into the patient can generally help to diagnose problems in the pump system.

VI. Valve Arrangement to Prime Heart Pump

Before or during the flow of infusant into the heart pump, it is beneficial to “prime” the heart pump by removing or expelling air from the device. Removing air from the heart pump can help to reduce the amount of air bubbles in the system, which can be detrimental to maintaining proper blood and/or infusant flow. The priming of the heart pump can occur before the heart pump is placed in a patient.

To remove air from the heart pump, infusant can be introduced into the heart pump to physically displace air. The infusant is used to physically direct and force air out of an aperture (e.g., located at the distal tip at the base of the impeller hub). For example, in conventional heart pumps, infusant can flow down an infusant delivery flow path to physically direct air to exit an aperture. The infusant can either exit the aperture or can continue to flow down an infusant return flow path. In conventional pumps, the infusant return flow path is not being utilized as a path to infuse fluid to direct air towards the distal aperture, and air can detrimentally remain within the heart pump, including along the infusant return flow path. On the contrary, in the present system, a purge pump is used to drive infusant from a reservoir into a circuit, flow/flushing through components and moving parts of the blood pump, pushing/expelling air, debris into a waste container while lubricating the moving parts (e.g., drive shaft) and preventing blood from entering the circuit simultaneously. The removal of the air from the heart pump can occur prior to introducing the pump into a patient.

To enhance the expulsion of air from the heart pump, a novel pump system can be provided that utilizes both the infusant delivery flow path and the infusant return flow path to expel air from the system. The pump system includes a novel valve arrangement that is provided between the infusant delivery flow path and the infusant return flow path to temporarily route the infusant input flow path to the return flow path. By routing the infusant delivery flow path to the return flow path, this creates a short between the delivery flow path and return flow path. Infusant can then flow down both the delivery flow path and the “return” flow path such that the infusant can force and displace the air (e.g., in the flow paths) to exit an aperture or clearance in the heart pump10, such as at or in the impeller hub208(seeFIG. 3). The aperture or clearance can be located at the distal tip at the base of the impeller hub208. By providing an infusant flow path down both the delivery flow path and return flow path, air can be displaced and expelled out of the one or more apertures. The air is thus removed via both the delivery flow path and what would ordinarily be the “return” flow path to rapidly and effectively expel air from the system.

The process of expelling air will be performed prior to insertion of the catheter assembly100of the heart pump10into the patient if the air is expelled through a portion that would be disposed within the patient in use to avoid air embolism. The heart pump can be held vertically (e.g., with the distal tip of the impeller208upward) so that air bubbles can float out the appropriate apertures prior to inserting the heart pump into the patient. Such vertical priming can prove especially advantageous to remove air to prime the device, as the air can be both pushed out by infusant and can float out of the heart pump. In other embodiments, air expulsion can also take place during operation of the heart pump.

FIGS. 17A and 17Billustrate another embodiment of an infusion system700for a heart pump that has a novel valve arrangement in which an infusant delivery flow path712and an infusant return flow path714are connected via a shunt727by having an optional shunt valve730. An optional additional outflow valve740can be positioned along the infusant return flow path714.FIG. 17Aillustrates a conventional flow route with the optional shunt valve730closed and inoperable.FIG. 17Billustrates a novel flow route with both the shunt valve730open and operable and the additional outflow valve740closed, in which air can be directed down both the infusant delivery flow path712and the infusant return flow path714for expulsion out of a catheter body (not shown). The infusion system700advantageously allows air to be expelled from the heart pump prior to introducing the pump into a patient.

FIG. 17Aillustrates a conventional flow route with the optional shunt valve730closed and the shunt727inoperable, such that a short is not created between the infusant delivery flow path712and the infusant return flow path714. As shown by the arrows in FIG.17A, infusant can flow into the infusant delivery flow path712, through a pump catheter body, and out of the infusant return flow path714. While in this configuration, some air may be removed from the pump catheter body, air that is not removed from the pump catheter body can be trapped (such as along the infusant return flow path714) rather than expelled.

FIG. 17Billustrates an improved flow route with the optional shunt valve730open and the shunt727operable, such that a short is created between the infusant delivery flow path712and the infusant return flow path714. In addition, optional valve740can also be closed, thereby blocking the conventional pathway of the infusant return flow path714. As shown by the arrows inFIG. 17B, this valve arrangement allows infusant to flow down the infusant delivery flow path712, as well as down the shunt727and down the infusant return flow path714. The infusant can flow down both the delivery flow path712and the return flow path714to physically displace air towards an aperture at a distal end of the heart pump, whereby the air can be expelled from an aperture (e.g., at the distal tip of an impeller). The shunt727thus provides multiple pathways via which the infusant can flow to displace the air and expel it from the catheter.

In some embodiments, the infusant flow down the infusant delivery flow path712and the infusant return flow path714can differ due to the differences in the flow paths and any restrictions (e.g., walls or baffles) therein. Accordingly, in some embodiments, the shunt727includes a component to modulate the flow (e.g., down the infusant return flow path714) to accommodate any differences in the infusant flow that may affect air expulsion. For example, the shunt727can include a mechanical wall that can be raised or lowered to different heights to increase or decrease the amount of infusant flow that is delivered through the shunt pathway.

In alternative embodiments, to expel air from the pump, infusant can be introduced into both an inflow port (e.g., connected to the delivery flow path712) and an outflow port (e.g., connected to the return flow path714). In some embodiments, the flow of infusant into the inflow port and the outflow port can be simultaneous, sequential, or both. By introducing infusant into both an inflow port and an outflow port, the infusant can displace air along two separate pathways, thereby helping to make the priming process more efficient. The use of the shunt to create a short between the delivery flow path712and the return flow path714is optional in this embodiment.

In alternative embodiments, the above valve arrangement with shunt727, shunt valve730and outflow valve740can also be accompanied by a first pump provided to regulate in-flow of the infusant and a second pump provided to regulate out-flow of the infusant. Advantageously, when the shunt727is operable and the outflow valve740is closed, the second pump can also be turned off, thereby helping to redirect infusant and air down the infusant return flow path714. Even if the outflow valve740is not yet closed, the second pump can still be turned off in order to help redirect infusant and air down the infusant return flow path714.

The novel valve arrangement with shunt can be provided anywhere between the infusant delivery flow path and the infusant return flow path. For example, with respect toFIG. 16, the valve arrangement with shunt can be provided downstream of the pump assembly620to connect the fluid supply line612to the fluid return line614. The novel valve arrangement advantageously helps to provide a faster and more effective means to “prime” and expel air from the pump device prior to or during use.

Other alternative embodiments may not include a shunt727. In at least some of these embodiments, trapped air can exit the heart pump both at a distal end (e.g., adjacent the impeller assembly) and at a proximal end (e.g., by way of the proximal flow of infusant traveling along the return flow path714).

In some embodiments, the flow rates of infusant during the priming process can be different than the flow rates of infusant during operation. In some embodiments, the flow rates of infusant can be higher during the priming process due to the desire to displace and expel columns of air from out of the heart pump. Once air has been removed from the heart pump, the flow rates of the infusant can be reduced. In some embodiments, during the priming process, it may be desirable to operate the impeller at a very low speed to assist in expulsion of air bubbles from the system.

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 pump10, which can be combined with the methods and techniques discussed above, are 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.

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.