US20160030649A1 - Catheter pump assembly including a stator - Google Patents

Abstract

A catheter pump assembly is provided that includes a proximal a distal portion, a catheter body, an impeller, and a flow modifying structure. The catheter body has a lumen that extends along a longitudinal axis between the proximal and distal portions. The impeller is disposed at the distal portion. The impeller includes a blade with a trailing edge. The flow modifying structure is disposed downstream of the impeller. The flow modifying structure has a plurality of blades having a leading edge substantially parallel to and in close proximity to the trailing edge of the blade of the impeller and an expanse extending downstream from the leading edge. In some embodiments, the expanse has a first region with higher curvature and a second region with lower curvature. The first region is between the leading edge and the second region.

Description

BACKGROUND OF THE INVENTION
• 1. Field of the Invention
• This application is directed to pumps for mechanical circulatory support of a heart. In particular, this application is directed to various implementations of a stator that can be used to enhance flow and/or performance of a catheter pump.
• 2. Description of the Related Art
• Heart disease is a major health problem that has high mortality rate. Physicians increasingly use mechanical circulatory support systems for treating heart failure. The treatment of acute heart failure requires a device that can provide support to the patient quickly. Physicians desire treatment options that can be deployed quickly and minimally-invasively.
• Intra-aortic balloon pumps (IABP) are currently the most common type of circulatory support devices for treating acute heart failure. IABPs are commonly used to treat heart failure, such as to stabilize a patient after cardiogenic shock, during treatment of acute myocardial infarction (MI) or decompensated heart failure, or to support a patient during high risk percutaneous coronary intervention (PCI). Circulatory support systems may be used alone or with pharmacological treatment.
• In a conventional approach, an IABP is positioned in the aorta and actuated in a counterpulsation fashion to provide partial support to the circulatory system. More recently minimally-invasive rotary blood pump have been developed in an attempt to increase the level of potential support (i.e. higher flow). A rotary blood pump is typically inserted into the body and connected to the cardiovascular system, for example, to the left ventricle and the ascending aorta to assist the pumping function of the heart. Other known applications pumping venous blood from the right ventricle to the pulmonary artery for support of the right side of the heart. An aim of acute circulatory support devices is to reduce the load on the heart muscle for a period of time, to stabilize the patient prior to heart transplant or for continuing support.
• There is a need for improved mechanical circulatory support devices for treating acute heart failure. Fixed cross-section ventricular assist devices designed to provide near full heart flow rate are either too large to be advanced percutaneously (e.g., through the femoral artery without a cutdown) or provide insufficient flow.
• There is a need for a pump with improved performance and clinical outcomes. There is a need for a pump that can provide elevated flow rates with reduced risk of hemolysis and thrombosis. There is a need for a pump that can be inserted minimally-invasively and provide sufficient flow rates for various indications while reducing the risk of major adverse events. In one aspect, there is a need for a heart pump that can be placed minimally-invasively, for example, through a 15FR or 12FR incision. In one aspect, there is a need for a heart pump that can provide an average flow rate of 4 Lpm or more during operation, for example, at 62 mmHg of head pressure. While the flow rate of a rotary pump can be increased by rotating the impeller faster, higher rotational speeds are known to increase the risk of hemolysis, which can lead to adverse outcomes and in some cases death. Accordingly, in one aspect, there is a need for a pump that can provide sufficient flow at significantly reduced rotational speeds. These and other problems are overcome by the inventions described herein.
SUMMARY OF THE INVENTION
• There is an urgent need for a pumping device that can be inserted percutaneously and also provide full cardiac rate flows of the left, right, or both the and right sides of the heart when called for.
• In one embodiment, a catheter pump assembly is provided that includes a proximal a distal portion, a catheter body, an impeller, and a flow modifying structure. The catheter body has a lumen that extends along a longitudinal axis between the proximal and distal portions. The impeller is disposed at the distal portion. The impeller includes a blade with a trailing edge. The flow modifying structure is disposed downstream of the impeller. The flow modifying structure has a plurality of blades having a leading edge substantially parallel to and in close proximity to the trailing edge of the blade of the impeller and an expanse extending downstream from the leading edge.
• In some embodiments, the expanse has a first region with higher curvature and a second region with lower curvature. The first region is between the leading edge and the second region.
• In some embodiments, the flow modifying structure is collapsible from a deployed configuration to a collapsed configuration.
• In another embodiment, a catheter pump is provided that has an impeller and a stator. The impeller is disposed at a distal portion of the pump. The stator is disposed downstream of the impeller. The impeller is sized and shaped to be inserted into a vascular system of a patient through a percutaneous access site having a size less than about 21 FR. The catheter pump is configured to pump blood in the vascular system at physiological rates at speeds less than 25K RPM.
• In another embodiment, a catheter pump assembly is provided that includes a proximal portion, a distal portion, a catheter body, and an impeller. The catheter body has a lumen that extends along a longitudinal axis between the proximal and distal portions. The impeller is disposed at the distal portion. The impeller includes a blade with a high angle to the longitudinal axis of the pump. The catheter pump assembly includes a flow modifying structure disposed downstream of the impeller. The flow modifying structure has a plurality of blades. Each of the blades can have a trailing edge that is inclined relative to a transverse plane intersecting the trailing edge. The flow modifying structure is collapsible from a deployed configuration to a collapsed configuration.
• In some embodiment, the trailing edge of the impeller and the leading edge of the flow modifying structure are configured to minimize losses therebetween. For example, the gap between these structures can be maintained small to minimize turbulence at this boundary. Also, the angles of both structures to the longitudinal axis of the impeller and flow directing structure can be approximately the same, e.g., more than 60 degrees and in some cases approximately 90 degrees. The impeller includes a blade with a trailing edge at an angle of more than about 60 degrees to the longitudinal axis of the impeller.
• In one embodiment, an impeller for a pump is disclosed. The impeller can comprise a hub having a proximal end portion and a distal end portion. A blade can be supported by the hub. The blade can have a fixed end coupled to the hub and a free end. Further, the impeller can have a stored configuration when the impeller is at rest, a deployed configuration when the impeller is at rest, and an operational configuration when the impeller rotates. The blade in the deployed and operational configurations can extend away from the hub. The blade in the stored configuration can be compressed against the hub. The blade can include a curved surface having a radius of curvature. The radius of curvature can be larger in the operational configuration than when the impeller is in the deployed configuration. The impeller can be used alone or in combination with a flow modifying device as discussed herein.
• In another embodiment, a percutaneous heart pump is disclosed. The pump can comprise a catheter body and an impeller coupled to a distal end portion of the catheter body. The impeller can comprise a hub. A blade can be supported by the hub and can have a front end portion and a back end portion. The blade can include a ramped surface at the back end portion. A sheath can be disposed about the catheter body and can have a proximal end and a distal end. The distal end of the sheath can be configured to compress the blade from an expanded configuration to a stored configuration when the distal end of the sheath is urged against the ramped surface of the blade. In some variants, a flow modifying device is downstream of the impeller. In such variants, the ramped surface may be positioned on the flow modifying device or may be positioned on both the flow modifying device and the impeller.
• In yet another embodiment, a method for storing an impeller is disclosed. The method can comprise urging a sheath against a ramped surface of a back end of a blade of an impeller. In some variants, a flow modifying structure is provided that may be distal or proximal of the impeller. If the flow modifying structure is proximal of the impeller, the method can comprise urging a sheath against a ramped surface of a back end of a blade of the flow modifying structure. The impeller can have one or more blades. Further, the impeller can have a stored configuration and a deployed configuration. Each blade in the stored configuration can be compressed against a hub of the impeller. Each blade in the deployed configuration can extend away from the hub. The method can further comprise collapsing the blade against the hub to urge the impeller into the stored configuration.
• In another embodiment, a percutaneous heart pump system is disclosed. The system can comprise an impeller disposed at a distal portion of the system. The impeller can be sized and shaped to be inserted through a vascular system of a patient. The impeller can be configured to pump blood through at least a portion of the vascular system at a flow rate of at least about 3.5 liters per minute when the impeller is rotated at a speed less than about 21,000 revolutions per minute. In some cases, the percutaneous heart pump system can also have a flow modifying structure, e.g., a stator.
• In another embodiment, a method of pumping blood through the vascular system of a patient is disclosed. The method can comprise inserting an impeller, with or without a flow modifying structure such as a stator, through a portion of the vascular system of the patient to a heart chamber. The method can further include rotating the impeller at a speed less than about 21,000 revolutions per minute to pump blood through at least a portion of the vascular system at a flow rate of at least about 3.5 liters per minute.
• In yet another embodiment, an impeller configured for use in a catheter pump is provided. The impeller can comprise a hub having a distal portion, a proximal portion, and a diameter. The impeller can also include a blade having a fixed end at the hub and a free end. The blade can have a height defined by a maximum distance between the hub and the free end. A value relating to a ratio of the blade height to the hub diameter can be in a range of about 0.7 to about 1.45.
• In another embodiment, a percutaneous heart pump system is provided. The system can comprise an impeller disposed at a distal portion of the system, the impeller sized and shaped to be inserted into a vascular system of a patient through a percutaneous access site having a size less than about 21 FR. The impeller can be configured to pump blood in the vascular system at a flow rate of at least about 3.5 liters per minute. In some variations, the heart pump system includes a flow modifying structure, such as a stator.
• In another embodiment, a percutaneous heart pump system is disclosed. The system can include an impeller comprising one or more blades in a single row. The impeller can be disposed at a distal portion of the system. The impeller can be sized and shaped to be inserted through a vascular system of a patient. The impeller can be configured to pump blood through at least a portion of the vascular system at a flow rate of at least about 2.0 liters per minute when the impeller is rotated at a speed less than about 21,000 revolutions per minute. In some variations, the heart pump system includes a flow modifying structure, such as a stator.
• In one embodiment, a catheter pump assembly is provided. The catheter pump assembly includes a proximal portion, a distal portion, a catheter body, an impeller, and a flow modifying structure. The catheter body has a lumen that extends along a longitudinal axis between the proximal and distal portions. The impeller is disposed at the distal portion. The impeller includes a blade with a trailing edge. The flow modifying structure is disposed downstream of the impeller. The flow modifying structure has a plurality of blades that have a leading edge in close proximity to the trailing edge of the blade of the impeller. The flow modifying structure has an expanse extending downstream from the leading edge. The expanse has a first region with higher curvature and a second region with a relatively lower curvature. The first region is between the leading edge and the second region. The flow modifying structure is collapsible from a deployed configuration to a collapsed configuration.
• In one embodiment, a catheter pump is provided that includes an impeller disposed at a distal portion of the pump and a stator disposed downstream of the impeller. In one embodiment, the impeller is sized and shaped to be inserted into a vascular system of a patient through a percutaneous access site having a size less than about 21 French (FR). In one embodiment, the impeller is sized and shaped to be inserted into a vascular system of a patient through a percutaneous access site having a size less than about 13 French (FR). In one embodiment, the impeller is sized and shaped to be inserted into a vascular system of a patient through a percutaneous access site having a size less than about 10 French (FR). In one embodiment, the catheter pump is configured to pump blood in the vascular system at physiological rates at speeds less than 25,000 RPM. In one embodiment, the catheter pump is configured to pump blood in the vascular system at physiological rates at speeds less than 20,000 RPM.
• In one embodiment, a catheter pump assembly is provided that includes a proximal portion, a distal portion, and a catheter body. The catheter body has a lumen that extends along a longitudinal axis between the proximal and distal portions. The catheter pump assembly also includes an impeller disposed at the distal portion. The impeller includes a blade with a trailing edge at an angle of more than about 60 degrees to the longitudinal axis of the impeller. The catheter pump assembly also includes a flow modifying structure disposed downstream of the impeller. The flow modifying structure has a plurality of blades that have a trailing edge that is inclined relative to a transverse plane intersecting the trailing edge. The flow modifying structure is collapsible from a deployed configuration to a collapsed configuration.
• In one embodiment, a catheter pump assembly is provided that includes a proximal portion and a distal portion. The catheter pump assembly includes an impeller disposed at the distal portion and configured to pump blood generally in a longitudinal direction. The impeller includes one or more impeller blades. The catheter pump assembly also has a stator assembly disposed downstream of the impeller. The stator assembly includes one or more stator blades.
BRIEF DESCRIPTION OF THE DRAWINGS
• A more complete appreciation of the subject matter of this application and the various advantages thereof can be realized by reference to the following detailed description, in which reference is made to the accompanying drawings in which:
• FIG. 1 illustrates one embodiment of a catheter pump configured for percutaneous application and operation;
• FIG. 2 is a plan view of one embodiment of a catheter adapted to be used with the catheter pump ofFIG. 1;
• FIGS. 3A-3C illustrate the relative position of an impeller blade and an inner surface of an impeller housing in an undeflected configuration;
• FIG. 4 shows the catheter assembly similar to that ofFIG. 2 in position within the anatomy;
• FIGS. 5A-5F are three-dimensional (3D) perspective views of an impeller according to one embodiment;
• FIG. 6 is a 3D perspective view of an impeller according to another embodiment;
• FIG. 7 is a 3D perspective view of an impeller according to yet another embodiment;
• FIG. 8 is a side view of an impeller according to another embodiment;
• FIGS. 9A-9E are side views of impellers according to various embodiments;
• FIG. 10A is a side view of an impeller according to yet another embodiment;
• FIG. 10B is a 3D perspective view of the impeller ofFIG. 10A;
• FIG. 11 is a side view of an impeller according to another embodiment.
• FIG. 12 is a schematic, side cross-sectional view of an impeller having a hub and one or more blades disposed within a housing.
• FIG. 13 is a chart plotting flow rate versus motor speed for the impellers illustrated inFIGS. 10A-10B and9E.
• FIG. 14 is a chart plotting flow rate versus motor speed for the impeller ofFIGS. 10A-10B at a given pressure, as compared to various conventional microaxial, rotary pumps at the same or similar pressure.
• FIG. 14A is an H-Q curve relating to four catheter pumps.
• FIG. 15 is a plan view of a distal portion of a catheter pump assembly.
• FIG. 16 is perspective view of a stator assembly.
• FIG. 17 is a first side view of a stator assembly.
• FIG. 18 is a second side view of a stator assembly.
• FIG. 19 is an end view of a stator assembly.
• FIG. 20A is a side view of an impeller positioned adjacent a flow modifying structure.
• FIG. 20B is an end view of the flow modifying structure shown inFIG. 20A.
• FIG. 20C is an enlarged side view of the impeller and flow modifying structure ofFIG. 20A.
• FIG. 20D is a schematic side view of a distal portion of a catheter pump assembly.
• More detailed descriptions 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 OF THE PREFERRED EMBODIMENT
• This application is directed to apparatuses for inducing motion of a fluid relative to the apparatus. In particular, the disclosed embodiments generally relate to various configurations for an impeller disposed at a distal portion of a percutaneous catheter pump. For example,FIGS. 1-4 show aspects of anexemplary catheter pump10 that can provide high performance flow rates. Theexemplary pump10 includes a motor driven by acontroller22. Thecontroller22 directs the operation of themotor14 and aninfusion system26 that supplies a flow of infusate in thepump10. Acatheter system80 that can be coupled with themotor14 houses an impeller within a distal portion thereof. In various embodiments, the impeller is rotated remotely by themotor14 when thepump10 is operating. For example, themotor14 can be disposed outside the patient. In some embodiments, themotor14 is separate from thecontroller22, e.g., to be placed closer to the patient. In other embodiments, themotor14 is part of thecontroller22. In still other embodiments, the motor is miniaturized to be insertable into the patient. Such embodiments allow the drive shaft to be much shorter, e.g., shorter than the distance from the aortic valve to the aortic arch (about 5 cm or less). Some examples of miniaturized motors catheter pumps and related components and methods are discussed in U.S. Pat. No. 5,964,694; U.S. Pat. No. 6,007,478; U.S. Pat. No. 6,178,922; and U.S. Pat. No. 6,176,848, all of which are hereby incorporated by reference herein in their entirety for all purposes.
• FIG. 4 illustrates one use of theexemplary catheter pump10. A distal portion of thepump10, which can include animpeller assembly92, is placed in the left ventricle (LV) of the heart to pump blood from the LV into the aorta. Thepump10 can be used in this way to treat patients with a wide range of conditions, including cardiogenic shock, myocardial infarction, and other cardiac conditions, and also to support a patient during a procedure such as percutaneous coronary intervention. One convenient manner of placement of the distal portion of thepump10 in the heart is by percutaneous access and delivery using the Seldinger technique or other methods familiar to cardiologists. These approaches enable thepump10 to be used in emergency medicine, a catheter lab and in other non-surgical settings. Modifications can also enable thepump10 to support the right side of the heart. Example modifications that could be used for right side support include providing delivery features and/or shaping a distal portion that is to be placed through at least one heart valve from the venous side, such as is discussed in U.S. Pat. No. 6,544,216; U.S. Pat. No. 7,070,555; and US 2012-0203056A1, all of which are hereby incorporated by reference herein in their entirety for all purposes.
• FIG. 2 shows features that facilitate small blood vessel percutaneous delivery and high performance, including up to and in some cases exceeding normal cardiac output in all phases of the cardiac cycle. In particular, thecatheter system80 includes acatheter body84 and asheath assembly88. Theimpeller assembly92 is coupled with the distal end of thecatheter body84. Theexemplary impeller assembly92 is expandable and collapsible. In the collapsed state, the distal end of thecatheter system80 can be advanced to the heart, for example, through an artery. In the expanded state, theimpeller assembly92 is able to pump blood at high flow rates.FIGS. 2-4 illustrate the expanded state. The collapsed state can be provided by advancing adistal end94 of anelongate body96 distally over theimpeller assembly92 to cause theimpeller assembly92 to collapse. This provides an outer profile throughout thecatheter assembly80 that is of small diameter, for example, to a catheter size of about 12.5 FR in various arrangements. Although various expandable impellers are disclosed herein (e.g., impellers having a stored configuration and a deployed configuration), it should be appreciated that the principles described below may also be applicable to impellers that may not be expandable or collapsible. For example, the impeller parameters described herein may also be applicable to fixed diameter impellers in some arrangements.
• In some embodiments, theimpeller assembly92 includes a self-expanding material that facilitates expansion. Thecatheter body84 on the other hand preferably is a polymeric body that has high flexibility. When theimpeller assembly92 is collapsed, as discussed above, high forces are applied to theimpeller assembly92. These forces are concentrated at a connection zone, where theimpeller assembly92 and thecatheter body84 are coupled together. These high forces, if not carefully managed can result in damage to thecatheter assembly80 and in some cases render the impeller within theimpeller assembly92 inoperable. Robust mechanical interface, are provided to assure high performance.
• The mechanical components rotatably supporting the impeller within theimpeller assembly92 permit high rotational speeds while controlling heat and particle generation that can come with high speeds. Theinfusion system26 delivers a cooling and lubricating solution to the distal portion of thecatheter system80 for these purposes. However, the space for delivery of this fluid is extremely limited. Some of the space is also used for return of the infusate. Providing secure connection and reliable routing of infusate into and out of thecatheter assembly80 is critical and challenging in view of the small profile of thecatheter body84.
• When activated, thepump10 can effectively increase the flow of blood out of the heart and through the patient's vascular system. In various embodiments disclosed herein, thepump10 can be configured to produce a maximum flow rate (e.g. low mm Hg) of greater than 4 Lpm, greater than 4.5 Lpm, greater than 5 Lpm, greater than 5.5 Lpm, greater than 6 Lpm, greater than 6.5 Lpm, greater than 7 Lpm, greater than 7.5 Lpm, greater than 8 Lpm, greater than 9 Lpm, or greater than 10 Lpm. In various embodiments, the pump can be configured to produce an average flow rate at about 62 mmHg during operation of greater than 2 Lpm, greater than 2.5 Lpm, greater than 3 Lpm, greater than 3.5 Lpm, greater than 4 Lpm, greater than 4.5 Lpm, greater than 5 Lpm, greater than 5.5 Lpm, or greater than 6 Lpm. In various embodiments, the pump can be configured to produce an average flow rate of at least about 4.25 Lpm at 62 mmHg. In various embodiments, the pump can be configured to produce an average flow rate of at least about 4 Lpm at 62 mmHg. In various embodiments, the pump can be configured to produce an average flow rate of at least about 4.5 Lpm at 62 mmHg. Flow modifying structures, such as fins or blades, which can be implemented in a stator, can be provided higher peak flow rate output by thepump10 as discussed below.
• Various aspects of the pump and associated components are similar to those disclosed in U.S. Pat. Nos. 7,393,181, 8,376,707, 7,841,976 7,022,100, and 7,998,054 and U.S. Pub. Nos. 2011/0004046, 2012/0178986, 2012/0172655, 2012/0178985, and 2012/0004495, the entire contents of which are incorporated herein for all purposes by reference. In addition, this application incorporates by reference in its entirety and for all purposes the subject matter disclosed in each of the following concurrently filed applications: application Ser. No. 13/802,556, which corresponds to attorney docket no. THOR.072A, entitled “DISTAL BEARING SUPPORT,” filed on Mar. 13, 2013; Application No. 61/780,656, which corresponds to attorney docket no. THOR.084PR2, entitled “FLUID HANDLING SYSTEM,” filed on Mar. 13, 2013; application Ser. No. 13/801,833, which corresponds to attorney docket no. THOR.089A, entitled “SHEATH SYSTEM FOR CATHETER PUMP,” filed on Mar. 13, 2013; application Ser. No. 13/801,528, which corresponds to attorney docket no. THOR.092A, entitled “CATHETER PUMP,” filed on Mar. 13, 2013; and application Ser. No. 13/802,468, which corresponds to attorney docket no. THOR.093A, entitled “MOTOR ASSEMBLY FOR CATHETER PUMP,” filed on Mar. 13, 2013.
Blade & Impeller Configurations
• With reference toFIGS. 3A-3C, an operative device of the pump can include animpeller300 having one ormore blades303. The one ormore blades303 can extend from animpeller hub301. It can be desirable to increase the flow rate of the heart pump while ensuring that theimpeller300 can be effectively deployed within a subject. For example, an impeller can include one ormore blades303 that are configured to be inserted into a subject in a stored, or compressed, configuration. When theimpeller300 is positioned in the desired location, e.g., a chamber of a subject's heart as shown inFIG. 4, the blade(s)303 of theimpeller300 can self-expand into a deployed or expanded configuration, in which the blade(s)303 extends radially from ahub301.
• As shown inFIGS. 3A-3B, theimpeller300 can be positioned within a cannula orhousing202. A free end of theblades303 can be separated from the wall W of thehousing202 by a tip gap G. Thehousing202 can also have a stored, or compressed configuration, and a deployed or expanded configuration. Thehousing202 andimpeller300 may deploy from the stored configurations from within a sheath or sleeve (not shown) into the expanded configuration. In such implementations, the sheath or sleeve can keep the blade(s)303 and thehousing202 compressed until the blade(s)303 andhousing202 are urged from within a storage cavity of the sheath or sleeve. Once the blade(s)303 are released from the storage cavity of the sheath, the blade(s)303 can self-expand to a deployed configuration using strain energy stored in theblades303 due to deformation of the blade(s)303 within the sheath or sleeve. Theexpandable housing202 may also self-deploy using stored strain energy after being urged from the sheath.
• In the stored configuration, theimpeller300 andhousing202 have a diameter that is preferably small enough to be inserted percutaneously into a patient's vascular system. Thus, it can be advantageous to fold theimpeller300 andhousing202 into a small enough stored configuration such that thehousing202 andimpeller300 can fit within the patient's veins or arteries. In some embodiments, therefore, theimpeller300 can have a diameter in the stored configuration corresponding to a catheter size between about 8 FR and about 21 FR. In one implementation, theimpeller300 can have a diameter in the stored state corresponding to a catheter size of about 9 FR. In other embodiments, theimpeller300 can have a diameter in the stored configuration between about 12 FR and about 21 FR. For example, in one embodiment, theimpeller300 can have a diameter in the stored configuration corresponding to a catheter size of about 12 FR or about 12.5 FR.
• When theimpeller300 is positioned within a chamber of the heart, however, it can be advantageous to expand theimpeller300 to have a diameter as large as possible in the expanded or deployed configuration. In general, increased diameter of theimpeller300 can advantageously increase flow rate through the pump. In some implementations, theimpeller300 can have a diameter corresponding to a catheter size greater than about 12 FR in the deployed configuration. In other embodiments, theimpeller300 can have a diameter corresponding to a catheter size greater than about 21 FR in the deployed or expanded configuration.
• In various embodiments, it can be important to increase the flow rate of the heart pump while ensuring that the operation of the pump does not harm the subject. For example, increased flow rate of the heart pump can advantageously yield better outcomes for a patient by improving the circulation of blood within the patient. Furthermore, the pump should avoid damaging the subject. For example, if the pump induces excessive shear stresses on the blood and fluid flowing through the pump (e.g., flowing through the cannula), then the impeller can cause damage to blood cells, e.g., hemolysis. If the impeller damages a large number of blood cells, then hemolysis can lead to negative outcomes for the subject, or even death. As will be explained below, various blade parameters can affect the pump's flow rate as well as conditions within the subject's body. Also, flow modifying structures such as stationary fins or blades, e.g., as part of a stator, can enhance the performance and/or efficiency of thepump10. In some arrangements, a stator may change the direction of flow, e.g., from a substantial portion circumferential to primarily axial direction. In some arrangements, the stator may modify the flow, e.g., to realign a complex flow field into a more uniform, laminar flow. This is sometimes referred to as smoothing out the flow or reducing turbulence. In this case, the stator may also serve to convert the kinetic energy of the complex flow field in the region of the trailing edges of the impeller into pressure before it is directed back into the circulatory system. This has been found to improve hydraulic efficiency because the complex, rotational flow field energy would normally be dissipated in the pump. In some arrangements, the stator may realign and redirect the flow. These embodiments enable thepump10 to create a greater pressure head (i.e. pressure differential) at the same rotational speed and backpressure. In turn, the clinician can advantageously adjust the pump to improve patient outcomes. The clinician can obtain a higher pressure head (H) at the same flow rate. Alternatively, the clinician may be able to obtain a higher flow rate (Q) with the same head pressure. The clinician may also be able to achieve improves to both H and Q. The pump may also be maintained the same head pressure and flow rate at a lower rotational speed. Lowering the rotational speed can reduce hemolysis risk. Thus, pump10 demonstrates significant performance improvements compared to a pump without these structures. These improvements to performance translate into improvements in clinical outcomes and expand the range of clinical applications of the pump.
Overview of Various Embodiments
• Various embodiments of an impeller for use in a heart pump are disclosed herein and the various impellers can be combined with a stator for enhanced performance as described further herein. Before discussing the combination of impellers and stators, various aspects of impeller embodiments will be discussed. In particular,FIGS. 5A-11 illustrate different configurations for an impeller300-300J. Each of the disclosed impellers300-300J can be defined by several different characteristics or parameters that can advantageously improve flow rate while achieving healthy outcomes in a patient. Further, various properties or characteristics of the disclosed impellers may assist in storing and/or deploying the impeller into and/or out from an outer sleeve. Each figure may only illustrate a few of the characteristics of the impeller for ease of illustration. However, it should be appreciated that each illustrated impeller may be associated with all of the characteristics or properties disclosed herein. For example, some figures may illustrate only a few angles or other geometric or structural properties of the impeller, but it should be appreciated that all the impellers disclosed herein may be associated with the disclosed characteristics or properties (see, e.g., the example values given in Tables 1 and 2).
• In order to improve patient outcomes, it can be advantageous to provide a heart pump capable of pumping blood at high flow rates while minimizing damage to the blood or the patient's anatomy. For example, it can be desirable to increase flow rate while reducing the motor speed, as higher motor speeds are known to increase the hemolysis risk. Furthermore, for percutaneous insertion heart pump systems, it can be advantageous to make the diameter of the impeller arid the cannula as small as possible for insertion into the patient's vasculature. Accordingly, the various impeller embodiments disclosed herein can provide high flow rate while maintaining a diameter small enough for insertion into the patient's vasculature and while reducing the risk that the patient's anatomy and blood are damaged during operation of the pump.
• For the impellers300-300J illustrated inFIGS. 5A-11, for example, theblades303 may be formed to have a curved profile with a radius of curvature, R. The radius of curvature R may be sized such that, when the impeller is in the stored or compressed configuration, theblades303 conform closely to thehub301. Indeed, in various arrangements, theblades303 in the stored configuration can have a radius R_Ssized such that theblades303 lie against thehub301 in a low profile so that the insertion diameter of the catheter pump is small enough to be safely inserted through the patient's vasculature. In some embodiments, the radius of curvature R and/or the height h of theblade303 are selected such that neighboring blades in a particular blade row do not overlap when the impeller is in the stored configuration. By reducing or eliminating blade overlap in the stored configuration, the insertion diameter of the catheter pump can be reduced. In other arrangements, however, neighboring blades may overlap in the stored configuration.
• Furthermore, when the impeller is urged out of an external sleeve, the impeller can self-expand into a deployed configuration, in which the impeller is deployed from the sleeve and expanded into a deployed diameter larger than a stored diameter. In various embodiments, the self-expansion of the impeller can be induced by strain energy stored in theblades303, such as strain or potential energy stored near the root of theblades303. When the sleeve is urged away from the impeller, theblades303 can be free to expand into the deployed configuration. It should be appreciated that when theblades303 are in the deployed configuration, the blade(s)303 can be in a relaxed state, such that there are no or minimal external forces (such as torque- or flow-induced loads) and internal forces (such as strain energy stored in the blades) applied to the impeller or blades. A radius of curvature R_Dof theblades303 in the deployed configuration may be selected to improve flow characteristics of the pump while reducing the risk of hemolysis or other damage to the patient. For example, in some embodiments, the impeller can be molded to formblades303 having the desired deployed radius of curvature R_D, such that in a relaxed (e.g., deployed) state, theblades303 have a radius of curvature R_Dthat may be selected during manufacturing (e.g., molding). In some arrangements, the radius of curvature R_Dof the blades in the deployed configuration may be about the same as the radius of curvature R_Sof the blades in the stored configuration. In other arrangements, however, the radius of curvature of theblades303 in the stored and deployed configurations may be different.
• When the heart pump is activated to rotate the impeller, the impeller andblades303 may be in an operational configuration. In the operational configuration, the impeller may rotate to drive blood through thehousing202. The rotation of the impeller and/or the flow of blood past the impeller can cause theblades303 to deform such that an operational radius of curvature R_omay be induced when the impeller is in the operational configuration. For example, when the impeller rotates, theblades303 may slightly elongate such that the free ends of theblades303 extend further radially from thehub301 relative to when theblades303 are in the deployed configuration. As theblades303 deform radially outward in the operational configuration, the operational radius of curvature R_omay therefore be larger than the deployed radius of curvature R_D. For example, in some embodiments, in the operational configuration, theblades303 may substantially flatten such that there is little curvature of the blades during operation of the pump. Indeed, in the operational configuration, theblades303 may extend to an operational height h_othat is larger than the height h of theblades303 when in the deployed configuration (see h as illustrated in the impellers300-300J ofFIG. 5A-11, which are in a deployed or relaxed configuration). In some embodiments, because theblades303 may be manufactured to be relaxed when in the deployed configuration, the radius of curvature R_Dand the height h of theblades303 in the deployed configuration can be selected such that, in the operational configuration, theblades303 extend radially outward from thehub301 as far as possible without risking an overly small tip gap G (seeFIG. 3C). Flow rate can be improved by enabling theblades303 to extend radially outward to a greater extent in the operational configuration than in the deployed configuration.
• It should be appreciated that the various parameters described herein may be selected to increase flow rate, even while reducing the rotational speed of the impeller. For example, even at relatively low impeller rotational rates of 21,000 revolutions per minute (RPM) or less (e.g., rates in a range of about 18,000 RPM to about 20,000 RPM, or more particularly, in a range of about 18,500 RPM to about 19,500 RPM in some arrangements), theblades 303 can be designed to yield relatively high flow rates in a range of about 4 liters/minute (LPM) to about 5 liters/minute. Conventional percutaneous rotary blood pumps have been found to deliver less than ideal flow rates even at rotational speeds in excess of 40,000 RPM. It should be appreciated that higher impeller rotational rates may be undesirable in some aspects, because the high rate of rotation, e.g., higher RPMs, lead to higher shear rates that generally increase hemolysis and lead to undesirable patient outcomes. By reducing the impeller rotational rate while maintaining or increasing flow rate, the pump in accordance with aspects of the invention can reduce the risk of hemolysis while significantly improving patient outcomes over conventional designs.
• Furthermore, to enable percutaneous insertion of the operative device of the pump into the patient's vascular system, the impellers300-300J disclosed herein inFIGS. 5A-11 may also include a ramped surface at a rearward or proximal end of the blade. As explained herein (see, e.g.,FIG. 12), when the external sleeve is urged against the housing202 (e.g., cannula), the external sleeve can press against thehousing202 and the ramped surface of the impeller to collapse the impeller and blades into the stored configuration. For example, the ramped surface can be used to store the blades and impeller after assembly of the pump for packaging purposes and/or after performing a heart pumping procedure for withdrawal of the pump from the anatomy.
• The impellers disclosed herein may be formed of any suitable material and by any suitable process. For example, in preferred embodiments, the impeller is formed from a flexible material, e.g., an elastic material such as a polymer. Any suitable polymer can be used. In some embodiments, for example, Hapflex™ 598, Hapflex™ 798, or Steralloy™ or Thoralon™ may be used in various portions of the impeller body. In some arrangements, the impeller body can be molded to form a unitary body.
Various Impeller Designs
• Turning toFIGS. 5A-5F, one embodiment of theimpeller300 is presented. It should be appreciated thatFIGS. 5A-5F illustrate thesame impeller300, only showing different views and impeller parameters for ease of illustration. One ormore blades303 can extend from thehub301, such that a fixed end of theblades303 is integrally formed with or coupled to thehub301. Theblades303 can also have a free end located at the tip of theblades303. As used herein, therefore, it should be appreciated that theblades303 can have a fixed end coupled to the hub301 (e.g., at a blade root) and a free end at a tip of theblade303. In the illustrated embodiments, thehub301 andblades303 form a single unitary, or monolithic, body. However, it should be appreciated that in other embodiments, thehub301 andblades303 may be formed from separate components or materials. In various implementations, theimpeller300 can include one or more blade rows extending along thehub301.
• FIGS. 5A-5F illustrate theimpeller300 having one blade row and twoblades303. Thehub301 can have a first diameter D₁at a distal end portion of the impeller300 (e.g., near a leading edge of the blade(s)303) and a second diameter D₂at a proximal end portion of the impeller300 (e.g., near a trailing edge of the blade(s)303). As used herein and as shown inFIG. 5A, for example, a distal end portion of theimpeller300 may be disposed nearer the distal end of the catheter pump, while a proximal end portion of theimpeller300 may be disposed nearer the motor and the insertion site. As explained below, in some implementations, D₁can be less than D₂. Thehub301 can also have a length L, and theblades303 can have a height h, which can be the distance between the hub and the free end of the blades. Further, eachblade303 can have a blade length L_b, which may or may not be the same as the hub length L. As shown inFIG. 5A, the height h may be measured from thehub301 to the free end of a middle portion of theblades303 when the impeller is in a deployed or relaxed configuration. The height h may vary along the length of theblades303, e.g., increasing proximally from a forward or distal end of theblades303 to a maximum in a middle portion of the blades and decreasing from the middle portion to a rearward or proximal portion of the blades. Furthermore, as explained above, when theimpeller300 rotates and is in an operational configuration, the operational height h_omay be larger than the blade height h in the deployed or relaxed configuration, which is illustrated inFIGS. 5A-5F.
• Furthermore, eachblade303 can include asuction side305 and apressure side307. In general, fluid can flow from thesuction side305 of theblade303 toward thepressure side307 of theblade303, e.g., from the distal end portion of theimpeller300 to the proximal end portion of theimpeller300. Thepressure side307 can be include a curved, concave surface having a predetermined radius of curvature R, as best seen inFIG. 5C, and as explained above. For example, inFIGS. 5A-5F, the illustrated radius of curvature R corresponds to a relaxed or deployed radius of curvature R_D. As explained above, when theimpeller300 rotates, the impeller may be in an operational configuration having an operational radius of curvature R_othat may be larger than the deployed radius of curvature R_D. Indeed, in some embodiments, theblades303 may substantially flatten and elongate radially such that there is little curvature. Theelongated blades303 in the operational configuration may enable for increased flow rate through the pump.
• Moreover, eachblade303 can have a thickness designed to improve impeller performance. As shown inFIG. 5B, the leading edge or distal end portion of theblade303 can have a first thickness t_1aat the fixed end of theblade303, where theblade303 joins thehub301, and a second thickness t_1bat the free end of theblade303. Similarly, inFIG. 5C, the trailing edge of theblade303 can also have a first thickness t_2aat the fixed end of theblade303 and a second thickness t_2bat the free end of theblade303. Example parameters for various blades inFIGS. 5A-11 will be disclosed in the description below and in Tables 1 and 2.
• Eachblade303 can wrap around thehub301 by a desired wrapping angle. The wrapping angle can be measured along the circumference of thehub301. As shown in the illustrated embodiments, eachblade303 can separately track a helical pattern along the surface of thehub301 as theblade303 wraps around thehub301 along the length L of the hub. Table 2 and the disclosure below illustrate example wrapping angles forblades303 in various embodiments. The blades can wrap around the hub any suitable number of turns or fractions thereof. Further, afirst fillet311 can be formed at the fixed end of each blade on thesuction side305, and asecond fillet313 can be formed at the fixed end of eachblade303 on thepressure side307. As shown eachfillet311,313 can follow the fixed end of eachblade303 as it wraps around thehub301. As explained below, thefirst fillet311 can be sized and shaped to provide support to theblade303 as theimpeller300 rotates. Thesecond fillet313 can be sized and shaped to assist in folding or compressing theblade303 into the stored configuration.
• In addition, eachblade303 can form various blade angles α, β, and γ. As shown inFIGS. 5D-F, the blade angles α (referred to herein as an “attack angle α” or a “distal blade angle α”), β (referred to herein as a “middle blade angle β”), and γ (referred to herein as a “proximal blade angle γ”) measure the angles between a blade centerline at various portions of the blade and a plane that is perpendicular to thehub301. For example, the attack angle α can measure the angle between a plane formed perpendicular to the blade near the distal portion of the blade (e.g., distally along the impeller hub inFIG. 5D) and a plane formed perpendicular to thehub301. The attack angle α can range between about 30 degrees and about 60 degrees. In some implementations, α can range between about 40 degrees and about 55 degrees. In the implementation ofFIG. 5D, for example, α can be in a range of about 48 degrees and about 52 degrees, e.g., about 50 degrees. The middle blade angle β can measure the angle between a plane perpendicular to the blade in a middle portion of the blade and a plane perpendicular to thehub301. In some implementations, β can range from about 30 degrees to about 45 degrees. In the implementations ofFIGS. 5A-5F and6, for example, β can be in a range of about 35 degrees and about 42 degrees, e.g., about 40 degrees. The proximal blade angle γ can correspond to the angle between a plane perpendicular to the blade in a proximal portion of the blade (e.g., proximal with respect to the hub301) and a plane perpendicular to thehub301. In some embodiments, γ can range between about 25 degrees and about 55 degrees. In the illustrated embodiment ofFIG. 5F, γ can be in a range of about 30 degrees and about 40 degrees, or about 35 degrees, for example. In some embodiments, the attack angle α can be larger than the middle blade angle β. Further, in some embodiments, the middle blade angle can be larger than the proximal blade angle γ. In some embodiments, the attack angle α can be larger than both the middle blade angle β and the proximal blade angle γ. The blade angles α, β, and γ can be further designed using computational techniques to maintain desired flow characteristics, such as flow rate, pressure head, and rotational speed. For example, the disclosed blade angles can, in various impellers disclosed herein, enable flow rates in a range of about 4 liters/minute to about 5.5 liters minute, when the impeller rotates at a speed below about 20,000 RPMs (e.g., in a range of about 19,000 RPMs to about 21,000 RPMs in some arrangements). By maintaining a high flow rate at relatively low rotational speeds, the disclosed impellers can achieve desirable patient outcomes le reducing the risk of hemolysis and increasing pump reliability.
• Further, the trailing edge of eachblade303 can include aramp315 forming a ramp angle θ with the plane perpendicular to thehub301, as best illustrated inFIG. 5C. Theramp315 can be shaped such that when the sheath andhousing202 are urged against theramp315, or when theblades303 andhousing202 are pulled proximally relative to and into the sheath, the axial force applied by the sheath can be transferred downward by theramp315 to assist in folding theblade303 against thehub301. The ramp angle θ can be configured to assist in folding theblade303 against thehub301. Further, the cross-sectional curvature and/or axial form of the blades can also be configured to reduce the force needed to collapse the impeller when used in conjunction with the ramp angle θ. For example, the angle that the blades twist around the hub may be configured to direct axial forces applied by the sheath to fold the blades against thehub301. The radius of curvature R of theblades303 can also be selected to enable theblades303 to conform closely to thehub301, as explained above.
• Turning toFIGS. 6-11, other embodiments of theimpeller300 are illustrated. Reference numerals inFIGS. 6-11 generally represent components similar to those ofFIGS. 5A-5F. In addition, it should be appreciated that the parameters and angles described above with reference toFIGS. 5A-5F are also present in the impellers disclosed inFIGS. 6-11, even where such parameters or angles are not specifically referenced for ease of illustration. For example,FIG. 6 illustrates animpeller300A having twoblades303 in one blade row. On the other hand,FIG. 7 illustrates animpeller300B having threeblades303 in a single blade row.FIG. 8 illustrates another example of an impeller300C having twoblades303 in one blade row.FIGS. 9A-9C illustrate threeimpellers300F-300H, respectively, each having two blades in one row.FIG. 9D illustrates an impeller300I having three blades in one row. By contrast,FIG. 9E shows animpeller300J having four blades total, with two blade rows, each blade row having two blades.FIGS. 10A-10B illustrate yet anotherimpeller300D having threeblades303 in a single row, whileFIG. 11 shows animpeller300E having twoblades303 in a single row. Tables 1 and 2 include various properties for theimpellers300 shown in the embodiments ofFIGS. 5A-5C and6-11. The impellers300-300J disclosed herein may have different values for the various parameters and characteristics disclosed herein, and some of the impellers may have improved performance relative to other of the disclosed impellers.
• Theimpellers300 illustrated in the disclosed embodiments may have other features. For example, for impellers with multiple blade rows, the blade(s) in one row may be angularly clocked relative to the blade(s) in another row. It should be appreciated that the blades may be configured in any suitable shape or may be wrapped around the impeller hub in any manner suitable for operation in a catheter pump system.
Impeller Parameters
• As explained above, various impeller parameters can be important in increasing flow rate while ensuring that the pump operates safely within the subject. Further, various properties and parameters of the disclosed impellers300-300J ofFIGS. 5A-11 may enable the impellers to more easily collapse into the stored configuration. Similarly, with regard toFIGS. 15-19, features of stators enhancing these and other aspects are discussed below.
Hub Diameter and Length
• One impeller parameter is the size of the hub, e.g., the diameter and/or the length of the hub. As illustrated inFIGS. 5A-11, the hub can be tapered in various embodiments, such that the distal end portion of the hub has a first diameter, D₁, and the proximal end portion of the hub has a second diameter, D₂. The first and second diameters, D₁and D₂can determine the spacing between the wall W of thehousing202 and thehub301. Since thehousing202 effectively hounds the area through which blood can flow, the spacing between thehub301 and the housing wall W may determine the maximum flow rate through the pump. For example, if thehub301 has a relatively small diameter, then the flow area between the inner wall W of thehousing202 and thehub301 may be larger than in embodiments with a larger hub diameter. Because the flow area is larger, depending on other impeller parameters, the flow rate through the pump may advantageously be increased.
• One of skill in the art will appreciate from the disclosure herein that the impeller parameters may be varied in accordance with the invention. For a known pressure, blade height, h, and impeller angular velocity, ratios of D₁to D₂can be determined to provide the desired flow rate, Q. The hub diameter can vary. In some embodiments, D₁can range between about 0.06 inches and about 0.11 inches. D₂can range between about 0.1 inches and about 0.15 inches. For example, in the impeller shown inFIGS. 5A-5F, D₁can be about 0.081 inches, and D₂can be about 0.125 inches. In the implementation ofFIGS. 10A and 10B, D₁can be in a range of about 0.08 inches and about 0.09 inches (e.g., about 0.0836 inches in some arrangements), and D₂can be in a range of about 0.12 inches and about 0.13 inches (e.g., about 0.125 inches in some arrangements).
• Moreover, the length, L_b, of each blade can be designed in various embodiments to achieve a desired flow rate and pressure head. In general, longer blades can have higher flow rates and pressure heads. Without being limited by theory, it is believed that longer blades can support more blade material and surface area to propel the blood through the cannula. Thus, both the length of the blades and the first and second diameters D₁and D₂can be varied to achieve optimal flow rates. For example, D₁can be made relatively small while L_bcan be made relatively long to increase flow rate.
Blade Height
• Another impeller parameter is the height h of the blades of the impeller in the deployed, or relaxed, configuration. The height h of the blades can be varied to achieve a stable flow field and to reduce turbulence, while ensuring adequate flow rate. For example, in some embodiments, the blade can be formed to have a height h large enough to induce adequate flow through the cannula. However, because the blades are preferably flexible so that they can fold against the hub in the stored configuration, rotation of the impeller may also cause the blades to flex radially outward due to centrifugal forces. As explained above with respect toFIGS. 3A-3C, the tip gap G between the wall W of thehousing202 and the free ends of the blades can be quite small. If theblades303 flex outwardly by a substantial amount when theimpeller300 rotates, then the distal ends of the,blades303 may impact the housing wall W, which can damage blood cells passing by. Thus, the height h may also be formed to be sufficiently small such that, upon rotation of theimpeller300, deformation of theblades300 still maintains adequate tip gap G.
• On the other hand, as explained above, the height h of theblades303 in the deployed configuration can be selected such that when the impeller rotates, the tip or free end of theblades303 can extend or elongate to an operational height h_o, which extends further radially than when in the deployed configuration, in order to increase flow rate. Thus, as explained herein, the height h and the radius of curvature R_Dof theblades303 in the deployed configuration can be selected to both increase flow rate while reducing the risk of hemolysis caused by inadequate tip gap G.
• In various implementations, the height of the blades near the middle of the impeller hub can range between about 0.06 inches and about 0.15 inches, for example, in a range of about 0.09 inches to about 0.11 inches. Of course, the height of the blades can be designed in conjunction with the design of the hub diameters and length, and with the radius of curvature R. As an example, for the impeller inFIGS. 5A-5C, the height h of the blade near the middle of the impeller hub can be in a range of about 0.09 inches and about 0.1 inches (e.g., about 0.0995 inches in some arrangements). In the impeller ofFIGS. 10A-10B, the height h of the blade can be in a range of about 0.1 inches and about 0.11 inches (e.g., about 0.107 inches in some arrangements). Other example blade heights may be seen in Table 1.
Number of Blades
• As mentioned above,impellers300 can have any suitable number ofblades303. In general, in impellers withmore blades303, the flow rate of blood flowing through the cannula orhousing202 can be advantageously increased while reducing the required angular velocity of the drive shaft. Thus, absent other constraints, it can be advantageous to use as many blades as possible to maximize flow rate. However, because the impellers disclosed herein can be configured to fold against thehub301 in the stored configuration for insertion into a patient's vasculature, using toomany blades303 can increase the overall volume of the impeller in the stored configuration. If the thickness of theimpeller300 in the stored configuration exceeds the diameter of the sheath or sleeve (or the diameter of the patient's artery or vein), then theimpeller300 may not collapse into the sheath for storing.
• Moreover, increasing the number ofblades303 accordingly increases the number of shear regions at the free end of theblades303. As theimpeller300 rotates, the free ends of theblades303 induce shear stresses on the blood passing by theblades303. In particular, the tip or free edge of theblades303 can induce significant shear stresses. By increasing the overall number ofblades303, the number of regions with high shear stresses are accordingly increased, which can disadvantageously cause an increased risk of hemolysis in some situations. Thus, the number of blades can be selected such that there is adequate flow through the pump, while ensuring that theimpeller300 can still be stored within the sheath and that theblades303 do not induce excessive shear stresses. In various arrangements, for example, an impeller having three blades (such as the impellers shown inFIGS. 7,9D, and10A-10B) can achieve an appropriate balance between increased flow rate and reduced risk of hemolysis.
Radius of Curvature
• Yet another design parameter for the impeller is the radius of curvature, R, of theblades303 on thepressure side307 of the blades, as explained in detail above. As shown inFIGS. 5A-11, the illustrated impellers300-300J are in the deployed configuration, such that the illustrated R corresponds to the deployed radius of curvature R_D. The radius of curvature R can be designed to minimize turbulence, while increasing flow rate. Turbulence can disadvantageously dissipate energy as the impeller rotates, which can reduce the flow rate. In general, higher curvature on thepressure side307 of theblades303 can increase turbulence. Moreover, the radius of curvature R can be designed to conform to thehub301 such that, when the impeller is compressed by the sheath or sleeve, thecurved pressure side307 of theblade303 conforms to the curvature of thehub301 when theblades303 are folded against the hub. Thus, the radius of curvature R of the blades can be designed to both reduce turbulent flow and to assist in folding the blades against the hub to ensure that theimpeller300 fits within the sheath in the stored configuration.
• In addition, as explained above, when the impeller rotates and is in the operational configuration, the free end of theblades303 may extend radially outward such that the radius of curvature in the operational configuration, R_o, may be higher than the radius of curvature in the operational configuration, R_D, which is illustrated as R inFIGS. 5A-11. Indeed, the straightening and elongation of theblades303 in the operational configuration may advantageously increase flow rate through the pump system.
• The radius of curvature can range between about 0.06 inches and about 0.155 inches in various embodiments. In some embodiments, the radius of curvature can range between about 0.09 inches and about 0.14 inches. For example, in the implementation ofFIGS. 5A-5C, the cross-sectional radius of curvature R at the leading edge of the blades can be in a range of about 0.11 inches and about 0.13 inches (e.g., about 0.12 inches in some arrangements). By comparison, the radius of curvature R of the leading edge of the blades in theimpeller300 shown inFIGS. 10A-10B (in the deployed configuration) can be in a range of about 0.13 inches to about 0.14 inches (e.g., about 0.133 inches in some arrangements). Other curvatures may be suitable in various embodiments. Table 2 illustrates example values for the radius of curvature R of various embodiments disclosed herein, when the impellers are in the deployed configuration.
Blade Thickness
• In addition, the thickness of theblades303 can be controlled in various implementations. In general, the thickness of the blades can range between about 0.005 inches and about 0.070 inches in some embodiments, for example in a range of about 0.01 inches to about 0.03 inches. It should be appreciated that the thickness can be any suitable thickness. The thickness of theblade303 can affect how theblade303 collapses against thehub301 when compressed into the stored configuration and how the blade deforms when rotating in an operational configuration. For example, thin blades can deform more easily than thicker blades. Deformable blades can be advantageous when they elongate or deform by a suitable amount to increase flow rate, as explained above. However, as explained above, if theblade303 deforms outward by an excessive amount, then the free end of the blade can disadvantageously contact the inner wall of thehousing202 when theimpeller300 rotates. On the other hand, it can be easier to fold thin blades against thehub301 because a smaller force can sufficiently compress theblades303. Thus, it can be important in some arrangements to design a blade sufficiently stiff such that theblade303 does not outwardly deform into the cannula orhousing202, while still ensuring that theblade303 is sufficiently flexible such that it can be easily compressed into the stored configuration and such that it deforms enough to achieve desired flow rates.
• In some embodiments, the thickness of each blade can vary along the height h of the blade. For example, the blades can be thinner at the root of theblade303, e.g., near thehub301, and thicker at the free end of theblade303, e.g., near the wall W of thecannula housing202. As best seen inFIGS. 5B-5C, for example, the leading edge of the blade can have a first thickness t_1aat the fixed end of theblade303 and a second thickness t_1bat the free end of theblade303. Moreover, the trailing edge of theblade303 can have a first thickness t_2aat the fixed end of theblade303 and a second thickness t_2bat the free end of theblade303. Because theblades303 are relatively thin near thehub301, theblades303 can be easily folded into the stored configuration due to their increased flexibility near thehub301. Because theblades303 are relatively thick at the free end (e.g., near the cannula wall W), theblades303 may deform a suitable amount when the impeller rotates, reducing the risk that theblades303 will contact or impact the wall W. which can accordingly reduce the risk of hemolysis, while deforming enough to achieve desirable flow rates. Moreover, in some embodiments, the thickness may vary continuously, such that there are no steps or discontinuities in the thickness of the blade. For example, even though the free end of the blades may be thicker in some embodiments, the thickness can continuously increase along the height of the blade.
• As an example, the first thickness t_1aof the leading edge of the blade inFIGS. 5A-5C can be in a range of about 0.016 inches to about 0.023 inches near the hub (e.g., about 0.02 inches at the hub in some arrangements), while the second thickness t_1bcan be in a range of about 0.022 inches to about 0.028 inches at the free end (e.g., about 0.025 inches at the free end in some arrangements). Further, at the trailing edge of the blade ofFIGS. 5A-5C, the first thickness t_2acan be in a range of about 0.016 inches to about 0.023 inches near the hub (e.g., about 0.02 inches at the hub in some arrangements), and the second thickness t_2bcan be in a range of about 0.03 inches to about 0.04 inches at the free end (e.g., about 0.035 inches at the free end in some arrangements). As another example, for the blade ofFIGS. 10A-10B, the first thickness t_1aof the leading edge can be in a range of about 0.022 inches to about 0.028 inches at the hub (e.g., about 0.025 inches near the hub in some arrangements), and the second thickness t_1bcan be in a range of about 0.022 inches to about 0.028 inches at the free end (e.g., about 0.025 inches at the free end in some arrangements). At the trailing edge of the blade ofFIGS. 10A-10B, the first thickness t_2acan be in a range of about 0.016 inches to about 0.023 inches at the hub (e.g., about 0.02 inches in some arrangements), and the second thickness t_2bcan be in a range of about 0.016 inches to about 0.023 inches at the free end (e.g., about 0.02 inches in some arrangements).
Fillets at Root of Blades
• As explained above, afirst fillet311 can extend along thesuction side305 of eachblade303 at the proximal end of the blade303 (e.g., at the root of the blade), and asecond fillet313 can extend along thepressure side307 of each blade at the proximal end of theblade303. In general thefirst fillet311 can have a larger radius than thesecond fillet313. Thelarger fillet311 can be configured to apply a restoring force when theimpeller300 rotates in the operational configuration. As theimpeller300 rotates, theblades303 may tend to deform in the distal direction in some situations (e.g., toward the distal portion of the hub301). By forming thefillet311 at thesuction side305 of the blade, the curvature of the fillet can advantageously apply a restoring force to reduce the amount of deformation and to support the blade.
• By contrast, thesecond fillet313 formed on thepressure side307 of theblade303 can have a smaller radius than thefirst fillet311. Thesecond fillet313 can be configured to enhance the folding of the blade against the impeller when theblades303 are urged into the stored configuration.
• The radius r of each fillet can be any suitable value. For example, the radius r₁of thefirst fillet311 can range between about 0.006 inches and about 0.035 inches. The radius r₂of thesecond fillet313 can range between about 0.001 inches and about 0.010 inches. Other fillet radiuses may be suitable. For the implementation ofFIGS. 5A-5C, for example, the radius r₁of thefirst fillet311 can be about 0.015 inches, and the radius r₂of thesecond fillet313 can be about 0.005 inches. By contrast, for the impeller shown inFIGS. 10A-10B, thefirst fillet311 can have a radius r₁of about 0.025 inches, and thesecond fillet313 can have a radius r₂of about 0.005 inches.
Wrapping Angle
• In some implementations, the wrapping angle of each blade can be designed to improve pump performance and to enhance folding of the impeller into the stored configuration. In general, the blades can wrap around the hub at any suitable angle. It has been found that wrapping angles of between about 150 degrees and about 220 degrees can be suitable for folding the blades into the stored configuration. Further, wrapping angles of between about 180 degrees and about 200 degrees can be particularly suitable for folding the blades into the stored configuration.
Ramping Surface
• Furthermore, as explained above, the trailing edge or the proximal end of each blade can include a ramp or chamfer formed at an angle θ with a plane perpendicular to thehub301, as illustrated above in, e.g.,FIG. 5C.FIG. 12 is a schematic, side cross-sectional view of animpeller1200 having ahub1201 and one ormore blades1203 disposed within ahousing1202, similar to thehousing202 described above. As shown inFIG. 12, theimpeller1200 is in the expanded or deployed configuration. For example, theimpeller1200 may be in the deployed configuration before packaging and shipping to a customer. Alternatively, theimpeller1200 may be in the deployed configuration after pumping blood in a patient and before withdrawal of the pump from the vasculature. As explained above, it can be desirable to compress theimpeller1200 into the stored configuration for inserting or withdrawing the operative device of the pump from the patient. To assist in compressing theimpeller1200 into the stored configuration, the blade(s)1203 can include aramp1215 forming a ramp angle θ with a plane perpendicular to thehub1201.
• An outer sheath orsleeve1275 can be provided around an elongate body that extends between an operative device of the pump and the motor in the system. Thesleeve1275 can be used to deploy theimpeller1200 from the stored configuration to the deployed configuration and to compress theimpeller1200 from the deployed configuration back into the stored configuration. When compressing and storing theimpeller1200 and thehousing1202, for example, a user, such as a clinician, can advance thesleeve1275 in the +x-direction, as shown inFIG. 12. When urged in the +x-direction, thesleeve1275 can bear against acontact portion1235 of thehousing1202. Thecontact portion1235 of thehousing1202 can in turn bear against theramp1215. Advantageously, the ramp angle θ can be angled distally such that when the sheath orsleeve1275 is urged over theimpeller1200 andhousing1202, thecontact portion1235 can contact the angled or ramped edge of the blades to compress the blades against the hub. The ramp angle θ can be any suitable angle. For example, in some embodiments, the ramp angle θ can be between about 30 degrees and about 50 degrees. In the implementation ofFIGS. 5A-5C and12, for example, the chamfer or ramp angle θ of theramp1215 can be in a range of about 40 degrees to 50 degrees (e.g., about 45 degrees in some arrangements). In the embodiment ofFIGS. 10A-10B, the ramp angle θ of the trailing edge can be in a range of about 35 degrees to 45 degrees (e.g., about 40 degrees in some arrangements). Still other ramp angles θ may be suitable to assist in storing the impeller. In some embodiment, theramp1215 can comprise a solid, relatively stiff portion against which thehousing202 and sheath may be advanced.
Blade Height-to-Hub Diameter Ratio
• In some embodiments, a ratio σ of blade height (h) to hub diameter (D) can be defined. As explained above, thehub301 can have a first diameter D₁at a distal end portion of the impeller300 (e.g., near a leading edge of the blade(s)303) and a second diameter D₂at a proximal end portion of the impeller300 (e.g., near a trailing edge of the blade(s)303). As used herein, the ratio σ may be defined relative to a diameter D, which, in some embodiments, may correspond to the first diameter D₁or the second diameter D₂, or to an average of D₁and D₂. The blade height h may be identified relative to the deployed configuration in some embodiments. As shown inFIGS. 5A-11, the height h may be defined by a maximum distance between thehub301 and the free end of the blade(s)303.
• The ratio σ may be relatively large compared to conventional impellers. For example, as explained herein, it can be advantageous to provide for animpeller300 having a low profile suitable, for example, for percutaneous insertion into the patient's vascular system. One way to provide alow profile impeller300 is to reduce the volume of impeller material that is compressed within the outer sheath, e.g., the sheath within which theimpeller300 is stored during percutaneous delivery and insertion. Impellers having relatively large blade height-to-hub diameter ratios σ may allow for such compact insertion, while maintaining high flow rates. For example, larger blade heights h can allow for the use of smaller hub diameters D, and the larger blade heights h are also capable of inducing high flow rates that are advantageous for catheter pump systems. For example, in some embodiments, the blade height-to-hub diameter ratio σ can be at least about 0.95, at least about 1, at least about 1.1, and/or at least about 1.2, in various arrangements. In some embodiments, for example, the ratio σ can be in a range of about 0.7 to about 1.45 in various embodiments. In particular, the ratio σ can be in a range of about 0.7 to about 1.1 in some embodiments (such as the embodiment ofFIGS. 10A-10B, for example). In addition, in some arrangements, the ratio σ can be in a range of about 0.75 to about 1. in some embodiments, the ratio σ can be in a range of about 0.9 to about 1.1.
Example Impeller Parameters
• It should be appreciated that the values for the disclosed impeller parameters are illustrative only. Skilled artisans will appreciate that the blade parameters can vary according to the particular design situation. However, in particular embodiments, the blade parameters can include parameter values similar to those disclosed in Tables 1-2 below. Note that length dimensions are in inches and angles are in degrees.

• TABLE 1
  Figure	No. of	D1	D2	h	t1a	t1b	t2a	t2b
  Number	Blades	(in.)	(in.)	(in.)	(in.)	(in.)	(in.)	(in.)

  5A-5F	2	0.081	0.125	0.0995	0.02	0.025	0.02	0.035
  6	2	0.081	0.125	0.1	0.02	0.02	0.015	0.02
  7	3	0.0844	0.125	0.1025	0.015	0.015	0.02	0.02
  8	2	0.097	0.12	0.107	0.015	0.02	0.015	0.02
  10A-	3	0.0836	0.125	0.107	0.025	0.025	0.02	0.02
  10B
  11	2	0.0798	0.125	0.109	0.03	0.025	0.015	0.02

• TABLE 2
  		Wrap
  Figure	β	Angle	θ	r1	r2	R
  Number	(deg)	(deg)	(deg)	(in.)	(in.)	(in.)

  5A-5F	40	210	45	0.015	0.005	0.12
  6	40	210	45	0.015	0.005	0.07
  7	40	270	46	0.015	0.005	0.133
  8	40	200	40	0.015	0.005	0.12
  10A-	40	220	40	0.025	0.005	0.133
  10B
  11	30	210	35	0.015	0.005	0.09

• One will appreciate from the description herein that the configuration of the blades may be modified depending on the application. For example, the angle of attack of the blades may be modified to provide for mixed flow, axial flow, or a combination thereof. The exemplary blades of the illustrated figures are dimensioned and configured to improve axial flow and reduce hemolysis risk. The exemplary blades are shaped and dimensioned to achieve the desired pressure head and flow rate. In addition, the single blade row design is thought to reduce the turbulent flow between blade rows with other designs and thus may reduce hemolysis.
Flow Modifying Structures
• The impeller designs discussed herein are fully capable of providing flows to meet patient needs, as discussed below. However, pump performance can be even further improved by incorporating flow modifying structures downstream of the e.g., a stator or other structure providing flow directing or modifying structure (e.g. blades) in the flow stream. The flow modifying structures advantageously align a rotational, complex flow field generated by the high speed rotation of any of the impellers described herein into a more uniform and laminar flow, in some cases a substantially laminar flow field. This alignment of the flow converts rotational kinetic energy near the blades into pressure. Absent the flow modifying structures, some of the energy in the complex field would be dissipated and lost. This alignment of the flow reduces losses due to the otherwise disorganized nature of the flow exiting an impeller.
• FIGS. 15-19 show details of acatheter assembly400 and one embodiment of aflow modifying structure402 disposed in a distal portion of theassembly400 downstream from the impeller. The flow modifying structure can be a stator or stator assembly. Theflow modifying structure402 can include ablade body404 having one or a plurality of, e.g., three,blades408 extending outwardly from acentral body412. In the exemplary embodiment,flow modifying structure402 is a stator having a plurality ofblades408 configured to align or straighten flow from the impeller in an axial direction.FIG. 19 shows thatcentral body412 is hollow, enabling it to be mounted on a structure of thecatheter assembly400. Theblade body404 is at a downstream location of thecatheter assembly400 relative to theimpeller300. In a percutaneous left ventricle application, theblade body404 is disposed proximal of theimpeller300. In a percutaneous right ventricle application, theblade body404 is located distal of theimpeller300. In a transapical approach to aid the left ventricle, which might be provided through ports in the chest wall or via thoracotomy or mini-thoracotomy, thestator blade body404 is disposed distal of theimpeller300. It should be appreciated that theflow directing structure402 described herein may be implemented with any of the impellers300-300J disclosed herein to improve pump performance.
• Theflow modifying structure402 can be formed as a unitary body withcollapsible blades408. Theexemplary blades408 are collapsible and resiliently expandable, e.g., by releasing stored strain energy. In some embodiments, at least theblades408 are actuatable to an expanded state and do not require storing and releasing stored strain energy. For example, theblades408 can be inflatable or actuated by some mechanical means such as a pull wire to be enlarged from a low profile delivery state to an operational state.
• Theblades408 are configured to act on the fluid flow generated by theimpeller300 to provide a more clinically useful flow field (e.g., laminar) downstream of theflow modifying structure402. Theblades408 can improve efficiency by changing the flow field from the impeller into a more clinically useful flow field as it is output from thecatheter pump10. Theblades408 transform complex, mostly radial flow vectors generated by theimpeller300 into more uniform axial flow vectors. In some cases, theblades408 are configured to reduce other inefficiencies of the flow generated by theimpeller300, e.g., minimize turbulent flow, flow eddies, etc. Removing radial and/or circumferential flow vectors of the flow can be achieved with blades that are oriented in an opposite direction to the orientation of the blades of theimpeller300, for example, clockwise versus counterclockwise oriented blade surface. For example, the wrapping direction of theblades303 of theimpeller300D ofFIG. 10A is the opposite of that of theblades408 inFIG. 18.
• While theblades408 act on the flow generated by theimpeller300, the fluids also act on theflow modifying structure402. For example, theblade body404 experiences a torque generated by the interaction of theblades408 with the blood as it flows past theassembly402. A mechanical interface is provided between thecentral body412 and a distal portion of thecatheter assembly400. For example, thecentral body412 of theflow modifying structure402 can be mounted on a housing that also supports rotation of theimpeller300. Preferably the interface is self-tightening, as discussed in U.S. patent application Ser. No. 13/801,833, filed Mar. 13, 2013, entitled “SHEATH SYSTEM FOR CATHETER PUMP,” which is incorporated by reference herein in its entirety.
• An important feature of thecatheter assembly400 is defining a small gap G between theflow modifying structure402 and theimpeller300. The gap G is provided to accommodate relative motion between theimpeller300 and theflow modifying structure402. Theflow modifying structure402 can be held in a constant rotational position, while theimpeller300 rotates at a high rate. The gap G helps to reduce friction between and wear of theimpeller300 and thecentral body412 of theflow modifying structure402. The gap G should not be too large, however, to provide appropriate flow between the blades of theimpeller300 and thestator blades408. A large gap could provide a high pressure drop (i.e. hydraulic efficiency loss), which is disadvantageous. As discussed more below, theblades408 modify the flow characteristics of blood between theimpeller300 and an outlet of thecannula202.
• FIGS. 15-19 illustrate more features of theflow modifying structure402. Theblades408 preferably extend along a distal length of theblade body404. Theblades408 can extend from aleading edge420 to a trailingedge424 between ablade root428 and adistal edge432. Theleading edge420 can be any suitable shape to minimize inefficient transfer flow from theimpeller300. For example, theblade408 can have aconcave expanse436 disposed between the leading and trailingedges420,424.
• InFIG. 17 theconcave expanse436 is formed to follow a curve profile of thedistal edge432 of theblade408. Theconcave expanse436 has a complex curved shape including a distal portion that has relatively high curvature and a proximal portion that has less curvature. The relative curvatures can be seen in comparing the leading edge portion in ofblade408A and the curvature of the trailing edge portion of theblade408B inFIG. 17. In this embodiment, theblades408A,408B are identical but are mounted at spaced apart locations, e.g., 120 degrees from each other. Though the structure is not easily rendered in a two dimensional format, the portion A at theleading edge420 has a higher curvature than the portion B disposed between theleading edge420 and the trailingedges424.
• A gradual reduction in the degree of curvature is preferred to act on the blood directed proximally from theimpeller300. The flow generated by theimpeller300 can be characterized as a complex flow field. A gradual change in the angle of theblades408 will efficiently transform the complex flow field into a more unified, ordered field, e.g., generally axially directed and more laminar. Theblades408 reduce the rotational inertia of the flow that tends to carry the flow circumferentially and radially outwardly to direct the flow proximally, while minimizing turbulence and other inefficient flow regimes. A tangent to the curvature of thedistal edge432 is indicative of the direction in which theblade408 will tend to direct the flow interacting with theblade408. In the region A, a tangent to the curve of the distal edge432 (or theexpanse436 or440) can be disposed at an angle α to a line parallel to the longitudinal axis of thecentral body412. The angle α is shown onFIG. 18. The angle α is selected to allow the blood flowing off of the impeller to enter the space defined between theexpanse436 and theexpanse440 on adjacent blades (seeFIG. 17). The angle α can be less than about 60 degrees in one embodiment, and less than about 50 degrees in another embodiment, in some embodiments less than about 45 degrees. The angle α can be between about 30 degrees and about 70 degrees, and in some cases between about 40 and about 60 degrees.
• In the region B, a tangent to the curve of the distal edge432 (or theexpanse436 or440) is at a relatively low angle to a preferred flow direction. In one embodiment, it is preferred that the flow within the channel defined between theexpanse436 and theexpanse440 of adjacent blades approach a direction that is more axial than the flow in the area of theimpeller300 and more axial than downstream of theimpeller300 where thestator assembly402 not present. In some cases, the flow in the channel defined between theexpanse436 and theexpanse440 of adjacent blades approaches a direction generally parallel to the longitudinal axis of thecatheter assembly400. The angle of the structures of the blades in the region B, e.g., the tangent to the curvature at thedistal edge432, is between about 20 and about 50 degree, and in some cases between about 30 and about 40 degrees and in some cases between 35 and about 45 degrees.
• In some embodiments, the angle of trailing edge features relative to the desired direction of flow is a feature that can be advantageously controlled. For example, the angle β can be provided between theblade root428 in the region C and an axis parallel to the longitudinal axis of thecentral body412 of thestator assembly402. The angle β is between about zero and about 30 degrees, and in some cases is between about 5 and 20 degrees, and in other cases is no more than about 20 degrees, and can be less than about 10 degrees.
• FIG. 18 shows that the angles α and β define a flow channel between theexpanse436 of theblade408A and theexpanse440 of theblade408B. Theexpanse436 can include one side of theblade408A and the expanse can include one side of theblade408B. A leading edge portion of the channel defined in this manner has relatively high curvature along the sidewalls. A trailing edge portion of the channel defined in this manner has relatively low curvature along the sidewalls. The change in curvature helps shape the average flow direction of the flow of blood coming from theimpeller300 and exiting the channels in thestator assembly402.
• As discussed herein, the catheter pumps herein are configured for low profile delivery but theimpeller300 is expandable to provide for superior flow performance. Theblades408 of theflow modifying structure402 closely match the profile of the blades of theimpeller312. For example, in the deployed state, the blades of theimpeller312 extend a distance from a blade root by a distance that is about the same distance as is measured from theblade root428 to the bladedistal end432. Because theblades408 are to be delivered through the same profile as the impeller, theblades408 are also to be collapsible in some embodiments.
• Various features may be provided to facilitate deployment and collapse of theflow modifying structure402.Fillets411,413 similar to those hereinbefore described in connection with theimpeller300 can be provided to facilitate stability of thestator blades408 in operation of the pump and the collapse of the stator blades. Thefillets411,413 preferably have a first portion disposed on thecentral body412 and a second portion disposed at the junction of theblade root428 with theconcave expanse436 and theconvex expanse440. In one strategy for collapsing the stator, the blades are configured to fold distally and/or into the direction of curvature of thedistal edge432. In other words, theexpanse436 is moved toward thecentral body412 upon advancement of a distal end of thesheath assembly88 discussed above. More particularly, relative axial motion of the distal end of thesheath assembly88 over the trailingedge424 of theblades408 causes bending around thefillet411 disposed between theexpanse436 and thecentral body412. The bending is initially at the trailingedge424 and progresses toward theleading edge420 until theexpanse436 of each blade is folded down onto a corresponding portion on of thecentral body412 between theexpanse436 and theexpanse440 of an adjacent blade.
• In comparison, the trailing edge of theimpeller312 is relatively steep. As discussed above, this can provide efficient transfer of flow from the spinningimpeller312 to the stationaryflow modifying structure402. In embodiments where theimpeller312 is collapsed by a sheath, the collapse of theimpeller312 can be aided by the action of the collapsingcannula525 on the impeller.
• Another feature that facilitates collapse is the configuration of the trailingedge424. The trailingedge424 is disposed at an angle θ relative to an axis parallel to the longitudinal axis of thecentral body412 of thestator assembly402. The angle θ may be any of those discussed above in connection with the ramped surface of theimpellers300. The angle θ can be in a range of about zero to about 70 degrees. In some embodiments, the angle θ can be in a range of about 20 to about 60 degrees, in other embodiments, the angle θ can be between about 30 and 55 degrees. In other embodiments, the angle θ can be less than about 60 degrees.
• A trailing edgecylindrical portion454 is disposed between the trailing edges of thefillets411,413 and the proximal end of the central body of thestator assembly402. Thecylindrical portion454 spaces the trailingedges424 and thefillets411,413 from the boundary between thecentral body412 and more proximal portions of thecatheter assembly400. This allows blood to transition from three separate flows in the region of the blades to a single unified flow field between the proximal most portion of the trailingedge424 and the transition from thecylindrical body412 to another more proximal structure. By separating these transitions axially the flow is maintained more organized, e.g., is less likely to become more turbulent due to complex circumferential, radial, and axial boundaries.
• FIG. 20A is a side view of animpeller300D positioned adjacent a flow modifying structure502 (which can be a stator), in accordance with another embodiment. Theimpeller300D may be the same impeller as that illustrated inFIGS. 10A-10B, or it can be a different impeller. Theimpeller300D can include the features described above with reference toFIGS. 5A-12. For example, theimpeller300D can include a plurality ofblades303, with eachblade303 having apressure face307 and an opposingsuction face305. In the embodiment ofFIG. 20A, theimpeller300D does not include theramp315 described above, but in other embodiments, theramp315 may be included.
• Furthermore, as explained above with respect toFIGS. 15-19, theflow modifying structure502 can be disposed downstream of theimpeller300D. For example, as shown inFIG. 20A, theflow modifying structure502 can be disposed proximal theimpeller300D and can be separated from theimpeller300D by a small gap. Theflow modifying structure502 can include acentral body512 and a plurality ofblades508 extending outwardly from the central body. Theflow modifying structure502 may remain rotationally fixed relative to theimpeller300D as theimpeller300D rotates. As with the above-described embodiments, theflow modifying structure502 can be expandable from a collapsed configuration to a deployed configuration. InFIG. 20A, theflow modifying structure502 is illustrated in the deployed configuration. Theflow modifying structure502 can expand from the collapsed configuration to the deployed configuration when a sheath (not shown) is urged proximally relative to theflow modifying structure502. Strain energy stored in the collapsed or compressedflow modifying structure502 can be released when the constraint of the sheath is removed, and theblades508 can self-expand to the deployed configuration shown inFIG. 20A. Theflow modifying structure502 can be recollapsed by urging the sheath distally over theflow modifying structure502. For example, theflow modifying structure502 can include a trailing edge524 (seeFIG. 20C) that is angled sufficiently shallow such that forces from advancement of the sheath bear against the angled trailing edge524 to collapse theflow modifying structure502. [0126]FIG. 20B is an end view of theflow modifying structure502 shown inFIG. 20A. As with the embodiments described above with respect toFIGS. 15-19, theflow modifying structure502 can includeblades508 that extend radially outward from thecentral body412 and that are shaped to have a desired curvature. However, unlike the embodiments shown inFIGS. 15-19, theflow modifying structure502 ofFIG. 20B includes fourblades508, rather than the threeblades408 shown inFIG. 19. As explained below, it can be desirable to have the same number ofblades508 as outlets. For example, in catheter pumps having four outlets, it can be desirable to have fourblades508. In addition, thecentral body512 can include acentral lumen509 formed there-through along a longitudinal axis of theflow modifying structure502. As explained with respect toFIG. 15, a mechanical interface can be provided between thecentral body512 and a distal portion of the catheter assembly. For example, the distal portion of the catheter assembly can pass through thecentral lumen509.
• FIG. 20C is an enlarged side view of the impeller3001) andflow modifying structure502 ofFIG. 20A.FIG. 20D is a schematic side view of a distal portion of acatheter pump assembly500 that includes theimpeller300D andflow modifying structure502. Theimpeller3001 andflow modifying structure502 can be disposed within animpeller housing525 having one or morefluid outlets530. Theimpeller housing525, theimpeller300D, and theflow modifying structure502 can be inserted into a patient in a collapsed condition and expanded into a deployed configuration when theimpeller housing525 is positioned at a desired location, e.g., in a chamber of the heart. Theimpeller300D can rotate to pump blood generally in a longitudinal direction D, e.g. proximally through thecatheter pump assembly500.
• As explained herein, it can be advantageous to increase the flow rate of blood through the pump to improve the performance of thepump assembly500, while reducing the rotational speed of theimpeller300D to reduce the risk of hemolysis and improve patient outcomes. Accordingly, it can be desirable to improve the efficiency of thecatheter pump assembly500 so that lower rotational speeds can be used to achieve increased flow rates. As shown inFIG. 20D, in some arrangements, the flow of blood past the impeller can include a substantialcircumferential flow component537 that rotates with theimpeller300D. Thus, a portion of the kinetic energy transferred from theimpeller300D to the fluid (e.g., blood) induces thecircumferential flow component537 in a circumferential direction transverse to the longitudinal direction D. The circumferential flow will also have a radial components (e.g., outward toward the inner surface of the cannula525). It can be advantageous to recover this kinetic energy by converting or redirecting thecircumferential flow component537 towards the desired flow direction, e.g., along the longitudinal direction D.
• In addition to increasing the efficiency of the catheter pump, straightening or redirecting thecircumferential component537 can improve the stability of the catheter pump assembly501) by reducing vibrations caused by rotational or circumferential blood flow. Further, redirecting thecircumferential component537 can also advantageously reduce the residence time that the blood remains near theimpeller300D,impeller housing525, andflow modifying structure502. By reducing the residence time of the blood near these components, the risk of hemolysis can be further reduced because shear stresses are applied to the blood over a shorter time period.
• To assist in straightening the flow, e.g., straightening thecircumferential component537, theimpeller blades303 and theblades508 of theflow modifying structure502 can be shaped to gradually redirect the blood flow in the longitudinal direction D. For example, as shown inFIGS. 20C-20D, and as explained above, theblades508 of theflow modifying structure502 can have aleading edge520 and a trailing edge524. Acurved expanse536,540 can be defined on adjacent blades. Thecurved expanse536,540 can extend from theleading edge520 to the trailing edge524 of therespective blade508. As shown inFIG. 20C, theimpeller blades303 can define a surface normal N perpendicular to thepressure face307 near a trailingedge521 of theimpeller blade303. Theblades508 of theflow modifying structure502 can define a surface tangent T that is tangential to or parallel to the respectivecurved expanse536,540. If the curvature of theexpanse536,540 changes from distal to proximal, the surface tangent T can be tangential to or parallel to the distal portion of theexpanse536,540. To initially guide the blood flow into theflow modifying structure502, the surface normal N can be substantially aligned with the surface tangent T when eachimpeller blade300D is circumferentially proximate acorresponding blade508 of theflow modifying structure502. For example, at least once per revolution of theimpeller300D, the surface normal N of one of theblades303 can be substantially aligned with the surface tangent T of one of theblades508. This location or zone of alignment of the normal N and the tangent T is preferably located at or just prior to where thepressure face307 of theimpeller blade303 passes a correspondingstationary stator blade508. Thus, the trailingedge521 of theimpeller blade303 can direct the blood flow in a direction generally aligned with or parallel to the respectivecurved expanse536,540 as theimpeller300D rotates towards theblade508.
• As withFIGS. 15-19, a portion A at or near theleading edge520 can have a higher curvature than a portion B disposed between theleading edge520 and the trailing edge524. The curvature of theblades508 can gradually change between theleading edge520 and the trailing edges524 such that the flow is gradually straightened without introducing additional turbulence or undesirable flow fields. As illustrated inFIG. 20C, for example, thecircumferential flow component537 can be gradually straightened such that, near thecurved expanse536,540, the flow field is angled more towards the longitudinal direction D than the circumferential direction.
• Furthermore, as shown inFIG. 20D, theflow modifying structure502 can include the same number ofblades508 as there areoutlets530 in theimpeller housing525. For example, inFIG. 20D, there are fourblades508 and fouroutlets530. In some arrangements,adjacent blades508 of theflow modifying structure502 can define aflow channel534. Theflow channel534 can be angled towards a correspondingoutlet530 to direct the blood flow through theoutlet530. It can be advantageous in various embodiments to match the number ofblades508 andoutlets530 such that there is asingle flow channel534 for eachoutlet530. Such an arrangement organizes the flow fields and reduces turbulence near theoutlets530 by channeling the fluid towards aspecific outlet530.
• Theflow modifying structure502 can thereby convert thecircumferential flow component537 to a straightened,longitudinal component539 oriented along the longitudinal direction D. For example, bench tests and fluid flow simulations (e.g., using finite element analysis) of the disclosed flowcatheter pump assembly500 indicate that between about 40% and about 90% of the circumferential flow components can be converted into longitudinal flow components along D. A suitable bench test set-up may be one that provides a controlled flow in a closed loop. A suitable set-up allows for control and/or measurement of flow rate and pressure drop generated by the pump, for a selected speed (RPM). This bench test set-up has been used to show that a stator according to embodiments discussed herein can be used to reduce the rotational speed form 21K RPM to 18K RPM for comparable other flow parameters pressure drop and flow rate). As discussed in greater detail below, such improvements in pump operation have significant benefits to patients. By converting thecircumferential component537 into thelongitudinal component539, the kinetic energy imparted by theimpeller300D on the fluid is utilized in a more efficient manner, e.g., by generating increased flow rates in the longitudinal direction D for a given rotational speed. As explained herein, increasing the longitudinal flow rate without increasing impeller rotational speed can improve patient outcomes.
Improving Patient Outcomes
• As explained herein, it can be desirable to pump blood at relatively high to rates in order to provide adequate cardiac assistance to the patient and to improve patient outcomes. It should be appreciated that, typically, higher impeller rotational speeds may increase flow rates because the impeller is driven at a higher speed. However, one potential disadvantage of high impeller speeds is that blood passing across or over the rotating components (e.g., the impeller and/or impeller shaft or hub) may be damaged by the shearing forces imparted by the relatively rotating components. Accordingly, it is generally desirable to increase flow rates for given rotational impeller speeds.
• The various features disclosed herein can enable a skilled artisan to provide an impeller capable of increasing or maintaining flow rates at lower rotational impeller speeds. These improvements are not realized by mere increases in rotational speed or optimization of the impeller design. Rather, the improvements lead to a significant shift in the performance factor of the impeller, which reflect structural advantages of the disclosed impellers.
• FIG. 13 is a chart plotting flow rate versus motor speed for the impellers illustrated inFIGS. 10A-10B and9E. Note that, in the illustrated chart ofFIG. 13, however, that the impeller speed is the same as the motor speed, e.g., no clutch is used between the motor and impeller shaft. Thus, the plotted values inFIG. 13 represent flow rates at various impeller rotational speeds. The flow rates were measured by running the impellers on a closed mock loop on the bench with a blood analog. The back pressure (e.g., head pressure or change in pressure across the pump) was at about 62 mmHg for theimpellers300D,300J ofFIGS. 10A-10B and9E, respectively. The results on the bench top minor those achieved in animal investigations.
• As shown inFIG. 13, theimpeller300D provides for higher flow rates at lower speeds than theimpeller300J of, e.g.,FIG. 9E. For example, theimpeller300J ofFIG. 9E may be capable of pumping blood at flow rates in a range of about 4.5 liters per minute (LPM) to about 5.5 LPM when the impeller is operating at speeds in a range of about 25,000 revolutions per minute (RPMs) to about 28,000 RPMs. For example, the impeller ofFIG. 9E may be capable of pumping blood at a flow rate of about 5.5 LPM when the impeller is operating at speeds in a range of about 26,000 RPMs to about 28,000 RPMs.
• InFIG. 13, the flow rate of theimpeller300J can be plotted along a line X, in which flow rate increases with impeller rotational speed, which is the same as motor speed inFIG. 13. With prior designs, increased flow rate can only be achieved by increasing the rotational speed to move along the line X. Prior, it was expected that optimization of the impeller design can only realize minor improvements to the flow versus RPM curve. At best, the impeller could be configured to achieve minor improvements at the extremes or with a slight change in the curve X, such that the line or curve X might have a slightly higher slope.
• For example, with theimpeller300J ofFIG. 9E, the impeller speed at data point X1 is about 21,000 RPM, which yields a flow rate of about 1.9 LPM. With theimpeller300J ofFIG. 9E, flow rate can indeed be increased to above about 5 LPM, e.g., about 5.4 LPM, at data point X2, but the impeller rotational speed required to achieve such improvements in flow rate also increases to about 27,000 RPM. Thus, even though theimpeller300J ofFIG. 9E can achieve relatively high flow rates, the high flow rates come at the expense of a higher impeller speed, which, as explained above, can cause hemolysis and undesirable patient outcomes.
• By contrast, theimpeller300D ofFIGS. 10A-10B achieves significant and unexpected performance improvements. The exemplary impeller has been found to achieve dramatically higher flow rates at all rotational speeds. For example, theimpeller300D ofFIGS. 10A-10B can achieve flow rates above 4.25 LPM, indeed even above about 5 LPM, while maintaining a low impeller speed of less than about 21,000 RPM (which, by contrast, induced a flow rate of only about 1.9 LPM in theimpeller300J ofFIG. 9E). Thus, the design of theimpeller300D ofFIGS. 10A-10B can advantageously achieve structural advantages relative to theimpeller300J. Indeed, the curve labeled Y inFIG. 13 illustrates the dramatic shift of the flow rate curve to the left inFIG. 13, which indicates significantly increased flow rates at lower impeller speeds relative to prior impeller designs. The exemplary impeller has also been found to have a dramatically improved head pressure versus flow rate (HQ) performance versus conventional designs.
• Theexemplary impeller300D ofFIGS. 10A-10B has been found to be capable of pumping blood at flow rates in a range of about 4.5 LPM to about 5.5 LPM when the impeller is operating at speeds in a range of about 19,000 RPM to about 21,000 RPM, e.g., when the impeller is operating at speeds less than about 21,000 RPMs. For instance, theimpeller300D ofFIGS. 10A-10B may be capable of pumping blood at a flow rate of about 5.5 LPM when the impeller is operating at speeds in a range of about 20,000 RPMs to about 21,000 RPMs. Further, theimpeller300D ofFIGS. 10A-10B may be capable of pumping blood at a flow rate of about 5 LPM when the impeller is rotating at speeds in a range of about 19,000 RPMs to about 21,000 RPMs. In some arrangements, when the impeller is operating at a speed of about 19,500 RPMs, the flow rate may be in a range of about 4.5 LPM to about 5.1 LPM.
• Further, theimpeller300D ofFIGS. 10A-10B is capable of pumping blood at a flow rate of at least about 3.5 LPM, and/or at least about 4.25 LPM, when the impeller is operating at speeds less than about 21,000 RPMs. For example, theimpeller300D is capable of pumping blood at a flow rate of at least 4.25 LPM when the impeller is operating at speeds in a range of about 18,500 RPM to about 22,000 RPM, for example in a range of about 18,500 RPM to about 21,000 RPM. For example, theimpeller300D is capable of pumping blood at a flow rate in a range of about 4.25 LPM to about 5.5 LPM when the impeller is operating at speeds in a range of about 18,500 RPM to about 21,000 RPM. The flow rates achieved at these impeller speeds may be achieved at a back pressure or head pressure of at least 60 mmHg, e.g., at about 62 mmHg in some embodiments. Further theimpeller300D capable of achieving the performance ofFIG. 13 may also be sized and shaped to be inserted into a vascular system of a patient through a percutaneous access site having a catheter size less than about 21 FR.
• Theimpeller300D ofFIGS. 10A-10B may therefore provide a dramatic and unexpected jump in flow rates relative to theimpeller300J ofFIG. 9E. The shift in performance allows theimpeller300D to achieve a maximum flow rate far exceeding conventional and/or previous designs and at a rotational speed a mere fraction of that for which conventional pumps are designs. Thus,FIG. 13 illustrates that theimpeller300D ofFIGS. 10A-10B yields improved patient outcomes and reduced hemolysis relative to theimpeller300J ofFIG. 9E.
• FIG. 14 is a chart plotting flow rate versus motor speed (e.g., impeller speed) for an impeller similar to or the same as theimpeller300D ofFIGS. 10A-10B, as compared to various conventional microaxial, rotary pumps. In particular, Curve A inFIG. 14 plots flow rate versus motor speed (again, the same as impeller speed inFIG. 14) for the impeller associated with Curve A, according to test data taken using a blood analog at about 62 mmHG back pressure.
• Curve B plots approximate flow rate versus motor speed for the heart pump disclosed in the article of J. Stolinski, C. Rosenbaum, Willem Flameng, and Bart Meyns, “The heart-pump interaction: effects of a microaxial blood pump,”International Journal of Artificial Organs, vol: 25 issue: 11 pages: 1082-8, 2002, which is incorporated by reference herein in its entirety and for all purposes. The test data from Curve B was obtained under test conditions having a back pressure of about 60 mmHg.
• Curve C plots approximate flow rate versus motor speed for the heart pump disclosed in the article of David M. Weber, Daniel H. Raess, Jose P. S. Henriques, and Thorsten Siess, “Principles of Impella Cardiac Support,”Supplement to Cardiac Interventions Today, August/September 2009, which is incorporated by reference herein in its entirety and for all purposes. The test data from Curve C was obtained under test conditions having a back pressure of about 60 mmHg.
• Data point D plots approximate flow rate versus motor speed for the heart pump disclosed in Federal and Drug Administration 510(k) Summary for Predicate Device IMPELLA 2.5 (K112892), prepared on Sep. 5, 2012, which is incorporated by reference herein in its entirety and for all purposes. In particular, for data point D, the disclosed pump was capable of mean flow rates of up to 3.3 LPM at pump speeds of 46,000 RPM at a 60 mmHg differential pressure.
• As shown inFIG. 14, the disclosed impeller associated with Curve A can achieve higher flow rate at all impeller speeds relative to the pumps of Curves B, C, and D. The data reflected inFIG. 14 was not all collected by precisely the same methodology in a head-to-head fashion, as noted above. However, the data are shown on a single chart for the convenience of the reader and are still compelling. For example, as discussed above, the back-pressure conditions under which the Curve A data was collected (for impellers disclosed herein) was higher than that collected for the other devices. Were this test condition the same, the results would be all the more impressive. indeed, data points A1 and A2 of Curve A, for example, provide higher flow rates at significantly lower impeller rotation rates than any of the data points along Curves B-C or at point D (e.g., data points B1, B2, B3, C1, C2). In addition, as shown inFIG. 14, the impeller of Curve A can achieve flow rates of about 7 LPM at impeller speeds of only about 25,000 RPM, as shown by Curve A. By contrast, curves B-C and data point D do not even indicate that the conventional axial pumps can achieve 7 LPM flow rates at any impeller speed. Thus, the impeller associated with Curve A ofFIG. 14 can achieve higher flow rates at lower rotational speeds than conventional catheter pumps, such as microaxial, rotary pumps, (e.g., Curves B-C and data point D ofFIG. 14). In addition, the disclosed impellers can also be configured to achieve higher maximum flow rates than conventional pumps.
• In addition, the data of Curves B-C and data point D ofFIG. 14 represent another constraint on the design of conventional rotary pumps. For example, the pump plotted on Curve B has a diameter corresponding to a catheter size of about 21 FR. Flow rates may be increased for the pump of Curve B by increasing the diameter of the pump. However, further increases in pump diameter for the device of Curve B may disadvantageously increase the pump diameter requiring more invasive techniques to position the pump. Thus, increasing flow rate by increasing pump diameter may not be a feasible or desirable alternative for catheter pumps, and/or it may not be desirable for acute heart failure where fast implantation is critically important.
• By contrast, as shown in Curve A ofFIG. 14, the impeller (e.g., which can be the same as or similar to theimpeller300D disclosed herein) advantageously has an insertion diameter corresponding to a catheter size of less than about 13 FR, e.g., about 12.5 FR in some embodiments, which can enable minimally-invasive insertion techniques, even at higher flow rates and lower impeller rotation rates. Thus, the disclosed impeller of Curve A can provide higher flow rates at lower impeller speeds than conventional microaxial, rotary pumps, and can maintain lower insertion diameters for minimally invasive techniques.
• Indeed, the impeller of Curve A may be configured to be inserted into vascular system of a patient through a percutaneous access site having a size less than 21 FR. The impeller of Curve A (e.g., which may be similar to or the same asimpeller300D) may include one or more blades in a single row. In some embodiments, the impeller can be configured to pump blood through at least a portion of the vascular system at a flow rate of at least about 2.0 liters per minute when the impeller is rotated at a speed less than about 21,00 revolutions per minute. In some embodiments, the blades are expandable.
• FIG. 14A shows a performance curve for several catheter pumps to illustrate the capability of a catheter pump that includes thecatheter assembly400. Catheter pump performance can be characterized by the relationship between the pump's pressure differential H and flow rate Q at a given rotor speed S. This relationship can be represented by a map or graph, as shown inFIG. 14A. InFIG. 14A, the pressure differential H is represented by the Y axis and the flow rate Q by the X axis. For a given pump speed, the relationship between the pressure differential H and the flow rate Q is represented by an H-Q curve on the graph. As a result, a map of the continuous flow pump includes a family of H-Q curves, each curve representing a relationship between the pressure differential H and the flow rate Q for every different pump speed S.
• The family of H-Q curves inFIG. 14A represents the H-Q characteristics of thepump10 with thecatheter assembly400 and several other pumps. The native H-Q characteristics, including the shape, steepness (slope) and location of individual H-Q curves, is generally unique to the particular hydraulic design of pump and varies from one pump to another. As used herein, “H-Q” is an abbreviation for “pressure-flow.” The phrases “H-Q curve” and “pressure-flow curve” have the same meaning and are used interchangeably. The phrases “H-Q characteristics” and “pressure-flow characteristics” have the same meaning and are used interchangeably.
• FIG. 14A is a map of an axial flow pump generated by test data as would be understood by one of skill in the art. The term “map” refers to mapping of relationships between pressure differential H, flow rate Q and rotor speed S.
• InFIG. 14A, the actual or expected performance of each of four distinct pumps is illustrated. A first pump is illustrated by a consistent dashed line, and labeled “Conventional Pump C”. This line represents the pump performance of an Impella® 2.5 pump based on published data in “Principles of Impella Cardiac Support”, referenced above. A second pump, labeled “Convention Pump D” is illustrated by a triangle at a single point. This data is included in a 510(k) submission to the United Stated FDA for Impella® 2.5 Plus, discussed above. A third pump (“A-1”) is illustrated by a series of solid lines, and corresponds to a pump having an expandable impeller similar to those discussed herein. A pump including flow modifying structures similar to theflow direction structures402 was fabricated and tested. The pump test showed about a 15 percent improvement over the performance of a similar pump without the flow modifying structure. It is anticipated that further embodiments will yield a 10-15% increase in head pressure compared to a comparable design without the flow modifying structures. The expected performance of the fourth pump including the catheter assembly400 (“A-2”) is illustrated in line with repeating dash and two dots.
• As can be seen, for the first three curves where data was collected or retrieved from the literature by the assignee of this application, the pump A-1 has far superior performance overall. The family of curves for the pump A-1 demonstrates higher maximum flow rates than either Convention Pump C or D. Comparable or larger flow rates are achieved with impeller speeds that are significantly less than that of the other pumps for which data was collected or available. For example, for Conventional Pump D the motor speed required to obtain the flow rate as charted was 45,000 RPM whereas the pump A-1 achieved comparable flows at only 19,000 RPM. As discussed herein, these lower impeller speeds for pump A-1 are expected to provide much superior patient outcomes at least because hemolysis and other potentially deleterious blood interactions at the impeller will be dramatically reduced.
• The pump A-2 is expected to provide even higher flow performance than that of pump A-1. The chart illustrates the expected. H-Q performance at 22,000 RPM for a pump including thecatheter assembly400. The improved performance relates to a transformation of the flow field coming off of theimpeller300 into a more laminar state from a more complex flow field. The transformation converts kinetic energy associated with a rotational component of the flow into additional pressure, enhancing the performance. This line suggests a number of possible improvements that could be implemented in the operation or configuration of the pump A-2. For example, if the impeller diameter is the same in the pump A-2 as in the pump A-1, the pump A-2 could operate at a lower RPM while providing the same output (flow rate) as that of the pump A-1. Or, if the pump A-2 is operated at the same speed as the pump A-1, the output could be higher with the pump A-2 for comparable amount of hemolysis.
• A third advantage in view of the performance of the pump A-2 is that a smaller device could be made that would achieve the same output as the pump A-1 at the same impeller speed. For example, the device could be reduced in size to enable it to be placed in smaller blood vessels or through smaller sheaths such as the femoral artery or smaller vessels in the arterial system. A significant advantage of reducing the size of thepump10 is that there will be less blockage of flow in the femoral (or similar sized) artery to downstream tissue fed by the vasculature. Blockage can lead to ischemia of the tissue. Avoiding ischemia makes thepump10 more biocompatible generally and may enable the pump to be used for longer durations or with more patients.
• Although the inventions herein have been described with reference to particular embodiments, it is to be understood that these embodiments are merely illustrative of the principles and applications of the present inventions. It is therefore to be understood that numerous modifications can be made to the illustrative embodiments and that other arrangements can be devised without departing from the spirit and scope of the present inventions as defined by the appended claims. Thus, it is intended that the present application cover the modifications and variations of these embodiments and their equivalents.

Claims (34)

1. A catheter pump assembly, comprising:

a proximal portion;

a distal portion;

a catheter body having a lumen extending along a longitudinal axis between the proximal and distal portions;

an impeller disposed at the distal portion, the impeller including a blade with a trailing edge; and

a flow modifying structure disposed downstream of the impeller, the flow modifying structure having a plurality of blades having a leading edge in close proximity to the trailing edge of the blade of the impeller and an expanse extending downstream from the leading edge, the expanse having a first region with higher curvature and a second region with lower curvature, the first region being between the leading edge and the second region;

wherein the flow modifying structure is collapsible from a deployed configuration to a collapsed configuration.

2. The catheter pump assembly ofclaim 1, wherein the flow modifying structure is collapsible to a smaller diameter for percutaneous insertion.

3. The catheter pump assembly ofclaim 1, wherein the flow modifying structure is collapsible to a smaller diameter for insertion into a femoral artery.

4. The catheter pump assembly ofclaim 1, further comprising a bearing assembly disposed proximal of the impeller, the flow modifying structure being disposed on a distal projection of the bearing assembly.

5. The catheter pump assembly ofclaim 4, wherein a mechanical interface is provided between the bearing assembly projection and the flow modifying structure comprising a distal facing radial shoulder adjacent to a proximal facing end of the stator.

6. The catheter pump assembly ofclaim 4, wherein a mechanical interface provided between the bearing assembly projection and the flow modifying structure comprising mating feature disposed on the outer surface of the projection and on an inner surface of a lumen extending through a central body of the flow modifying structure.

7. The catheter pump assembly ofclaim 6, wherein the mating features comprise helical grooves and projections.

8. The catheter pump assembly ofclaim 7, wherein the grooves and projections are configured to urge the flow modifying structure toward a more secure configuration upon application of torque by fluid flow generated by the impeller.

9. The catheter pump ofclaim 1, wherein the flow modifying structure comprises a stator.

10. The catheter pump ofclaim 1, wherein the distal portion comprises an impeller housing having a first number of outlets, the impeller disposed in the impeller housing.

11. The catheter pump ofclaim 10, wherein the flow modifying structure has a second number of blades, and wherein the first number and the second number are the same.

12. The catheter pump ofclaim 11, wherein the first number and the second number are equal to four.

13. The catheter pump ofclaim 10, wherein adjacent blades of the flow modifying structure define a flow channel therebetween, the flow channel angled towards a corresponding outlet of the impeller housing to direct the fluid flow through the corresponding outlet.

14. The catheter pump ofclaim 1, wherein the impeller includes a plurality of impeller blades, each impeller blade including a trailing edge and a pressure face,

wherein a surface normal to the pressure face near the trailing edge of each impeller blade is substantially aligned with a surface tangent to the expanse near the leading edge of each blade of the flow modifying structure when each impeller blade is circumferentially proximate a corresponding blade of the flow modifying structure.

15. The catheter pump ofclaim 14, wherein at least once per revolution of the impeller, the surface normal to the pressure face near the trailing edge of each impeller blade is substantially aligned with the surface tangent to the expanse near the leading edge of each blade of the flow modifying structure.

16. (canceled)

17. (canceled)

18. (canceled)

19. (canceled)

20. (canceled)

21. (canceled)

22. (canceled)

23. A catheter pump assembly, comprising:

a proximal portion and a distal portion;

an impeller disposed at the distal portion and configured to pump blood generally in a longitudinal direction, the impeller including one or more impeller blades; and

a stator assembly disposed downstream of the impeller and including one or more stator blades.

24. The catheter pump assembly ofclaim 23, wherein the distal portion comprises an impeller housing having a first number of outlets, the impeller disposed in the impeller housing.

25. The catheter pump assembly ofclaim 24, wherein the stator assembly has a second number of stator blades, and wherein the first number and the second number are the same.

26. The catheter pump assembly ofclaim 25, wherein the first number and the second number are equal to four.

27. The catheter pump assembly ofclaim 23, wherein the stator blades are curved to redirect at least a portion of a circumferential flow component towards the longitudinal direction.

28. The catheter pump assembly ofclaim 23, wherein the impeller includes a plurality of impeller blades, each impeller blade including a trailing edge and a pressure face,

wherein each stator blade of the stator assembly includes a leading edge and a curved expanse extending downstream from the leading edge, and

wherein a surface normal to the pressure face near the trailing edge of each impeller blade is substantially aligned with a surface tangent to the curved expanse near the leading edge of each stator blade when each impeller blade is circumferentially proximate a corresponding stator blade.

29. The catheter pump assembly ofclaim 28, wherein at least once per revolution of the impeller, the surface normal to the pressure face near the trailing edge of each impeller blade is substantially aligned with the surface tangent to the curved expanse near the leading edge of each stator blade.

30. The catheter pump assembly ofclaim 25, wherein adjacent stator blades define a flow channel there between, the flow channel angled towards a corresponding outlet of the impeller housing to direct the fluid flow through the corresponding outlet.

31. The catheter pump assembly ofclaim 23, wherein the stator blades have a first region with higher curvature and a second region with lower curvature, the first region being between leading edges of the stator blades and the second region.

32. The catheter pump assembly ofclaim 23, wherein the stator assembly is expandable from a collapsed configuration to a deployed configuration.

33. The catheter pump assembly ofclaim 32, wherein the stator assembly is adapted to self-expand from the collapsed configuration to the deployed by the release of stored strain energy.

34. The catheter pump assembly ofclaim 23, wherein the stator assembly is disposed proximal the impeller.

Images