Modular expandable impeller with expandable cannula blood pump system

Abstract

A modular expandable impeller with expandable cannula blood pump system is described in which one variation may include a cannula having an expandable section extending from a shaft section, wherein the expandable section includes a distal conduit and a proximal conduit in fluid communication with a cannula lumen defined therebetween. The system may further include an impeller system having a distal stabilizer and an impeller coupled to a drive shaft, wherein the distal stabilizer and the impeller are reconfigurable between a low profile delivery configuration when passing through the shaft section and an expanded deployed configuration when positioned within the cannula lumen. The distal stabilizer in its expanded deployed configuration may contact against an inner surface of the cannula lumen while an outer diameter of the impeller is maintained at a distance from the inner surface of the cannula lumen.

Description

MODULAR EXPANDABLE IMPELLER WITH EXPANDABLE CANNULA BLOOD PUMP SYSTEMCROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application claims priority to U.S. Prov. App. 63 / 670,607 filed July 12, 2024, which is incorporated herein by reference in its entirety.FIELD OF THE INVENTION

[0002] The present invention relates to mechanical circulatory support (MCS) devices. More particularly, the present invention relates to MCS blood pumps such as left or right ventricular assist devices which are used to assist and unload cardiac chambers.BACKGROUND OF THE INVENTION

[0003] Heart disease is a major problem which claims many lives per year. After a heart attack, only a small number of patients can be treated successfully and non-invasively using medicines such as pharmaceuticals. However, with sufficient mechanical assistance the native heart may recover including those with cardiogenic shock. Blood pumps are typically used in patients suffering from a failing heart and in patients at risk for deterioration of cardiac function during percutaneous coronary interventions to maintain or augment cardiac output and help keep end organs perfused. Most commonly a left- ventricular assist device is applied to a defective heart in order to unload and rest the failing left ventricle and assist in pumping blood. In some cases, a right-ventricular assist device is used in order to assist right- ventricular functioning.

[0004] Conventional devices typically use fixed impellers to provide adequate blood flow (-5 L / min) at a certain pressure differential across the aortic valve. However, this approach has limitations because in order to provide relatively high flow rates, the impeller diameter needs to be large enough to sustain the high flow rates but also contributes to larger device diameters thereby resulting in relatively large, entry bore sizes for accessing vessels within the patient. Larger bore sizes require surgical interventions which are often inconvenient and add to procedural complications, stress, and risk to an already failing heart. In order to facilitate a minimally invasive approach while still delivering adequate blood flow, an expandable impeller can be used for percutaneous delivery into the patient. Such impeller and blood pump systems have been investigated previously as described in a 2005 paper published in Journal of the American College ofCardiology Vol. 45, No. 11, 2005 “An Expandable Percutaneous Catheter Pump for Left Ventricular Support” Proof of Concept by Thomas Schmitz-Rode, MD et al.

[0005] An expandable cannula and impeller system has been described and several previous attempts have been made over the years to develop expandable blood pumps that can satisfy the challenging size requirements yet provide sufficient flow and safety. However, such percutaneous Vascular Assist Devices (pVAD) fail to offer adequate flow to fully offload the ventricle and are also categorized as a large bore device (requiring an insertion introducer greater than 12 F) which leads to an increase in vascular complications such as bleeding and add to the risk of limb ischemia.

[0006] To achieve a particular flow rate at a given impeller rotation speed typically requires the use of an impeller having a relatively large diameter for resulting in suitable flow and pressure head performance. However, larger diameter impellers may result in an increase in the insertion profile of the device into the patient’s body. If the impeller diameter is reduced, the impeller typically requires operation at relatively large RPMs in order to achieve the desired flow rates and pressure heads. Yet, this may lead to an increased risk of hemolysis and component wear for longer duration use.

[0007] Several collapsable impellers and cannula approaches have been proposed previously to try to address this competing requirement. However, each of the approaches introduces multiple tradeoffs either in performance and efficiency or in size or both because these approaches try to collapse the impeller and a large coated cannula within a small diameter introducer to decrease the entry profile. There is only so much material volume that can packaged within a fixed smaller volume before material limitations set in and therefore, tradeoffs have to be made with respect to blood flow pump performance (e.g. achieving a 6 L / min flow at higher differential pressures) or increasing the entry profile.

[0008] There is a need for improvements to MCS devices which minimize the insertion profile to thus minimize procedure complications associated with vascular access and also maximize the flow of blood created or assisted by the device.SUMMARY OF THE INVENTION

[0009] Modular approaches and systems for constructing a mechanical circulatory support (MCS) device using a cannula having an expandable section and a collapsible impeller system are described. The approaches and systems described utilize devices which readily collapse in tight geometries (e.g., within a small profile instrument such as acannula shaft or introducer described herein), readily expand back to its original shape once deployed within the body, retain impeller blade geometry during operation in a dynamic environment (e.g., beating heart), provide acceptable performance of flow rate versus pressure head generated, provide for low shear stress, and result in a relatively low hemolysis during operation in blood within the patient’s body, provide durability for long (e.g., several days) and continuous use within the patient body, provide excellent surface finish as the impeller is in blood flow environment, and provides ease of manufacture and cost.

[0010] The approaches and systems thereby provide: (1) a modular approach to constructing a blood pump within the patient’s body; (2) provide suitable impeller configurations which may utilize (single monolith structure through the hub center); (3) provide a distal stabilizer integrated with the impeller assembly; and (4) provide for relative positioning of the impeller relative to the cannula lumen to ensure unhindered impeller rotation within the cannula during use.

[0011] In one variation of a circulatory support system, the system may generally comprise a cannula having an expandable section extending from a shaft section, wherein the expandable section includes a distal conduit and a proximal conduit in fluid communication with a cannula lumen defined therebetween. The system may also include an impeller system having a distal stabilizer and an impeller coupled to a drive shaft, wherein the distal stabilizer and the impeller are reconfigurable between a low profile delivery configuration when passing through the shaft section and an expanded deployed configuration when positioned within the cannula lumen. The distal stabilizer in its expanded deployed configuration may contact against an inner surface of the cannula lumen while an outer diameter of the impeller is maintained at a distance from the inner surface of the cannula lumen.

[0012] In another aspect of the system, the expandable section of the cannula may comprise a scaffold structure such that the distal conduit and the proximal conduit define one or more openings therethrough.

[0013] In another aspect of the system, the expandable section may further comprise a covering or coating upon the scaffold structure such that the distal conduit and the proximal conduit remain uncovered or uncoated.

[0014] In another aspect of the system, the expandable section of the cannula may comprise a scaffold structure having at least two sections of varying stiffness.

[0015] In another aspect of the system, the cannula may define a lumen through a length of the shaft section.

[0016] In another aspect of the system, the impeller may comprise a single monolithic helical body.

[0017] In another aspect of the system, the impeller may further comprise a central guidance feature along a central axis.

[0018] In another aspect of the system, a portion of the drive shaft may define a helical receiving slot for receiving the impeller.

[0019] In another aspect of the system, the impeller may define a helical open channel along its central region.

[0020] In another aspect of the system, the impeller may be over molded upon a portion of the drive shaft.

[0021] In another aspect of the system, the impeller may comprise one or more helical blades.

[0022] In another aspect of the system, a trailing edge and / or a leading edge of the impeller may be tapered.

[0023] In another aspect of the system, the impeller may further comprise a winglet upon a tip of the impeller.

[0024] In another aspect of the system, the distal stabilizer may comprise one or more distal stabilizer arms supported by a distal hub and a proximal hub positioned along the drive shaft.

[0025] In another aspect of the system, the distal hub may be configured to freely float relative to the drive shaft.

[0026] In another aspect of the system, the system may further comprise a distal bearing assembly coupled to the distal hub such that the distal bearing assembly is not axially constrained on the drive shaft.

[0027] In another aspect of the system, the proximal hub may comprise a rotatable bearing coupled to the drive shaft.

[0028] In another aspect of the system, the proximal hub may be attached to a casing or sheath surrounding the drive shaft and the distal hub may be configured to freely float relative to the drive shaft.

[0029] In another aspect of the system, the proximal hub may be attached to a casing or sheath surrounding the drive shaft and the distal hub may be coupled to a distal bearing assembly positioned along the drive shaft.

[0030] In another aspect of the system, the distal bearing assembly may not be axially constrained along the drive shaft.

[0031] In another aspect of the system, the impeller may be positioned within the distal stabilizer.

[0032] In another aspect of the system, the outer diameter of the impeller may be maintained at a predetermined clearance from an inner surface of the distal stabilizer.

[0033] In another aspect of the system, the impeller may be positioned at a distal position proximal to the distal conduit within the cannula lumen such that the distal stabilizer is also proximal of the distal conduit.

[0034] In another aspect of the system, the shaft section of the cannula may be configured to expand radially when the impeller is passed therethrough.

[0035] Any of these aspects may be combined with one another in any number of combinations and such variations are intended to be within the scope of this description.

[0036] In one variation of a method of deploying a circulatory support system, the method may generally comprise advancing a cannula intravascularly within a patient body to a predetermined position, wherein the cannula includes an expandable section extending from a shaft section such that the expandable section is advanced while in a low profile, delivery configuration; reconfiguring the expandable section to an expanded, deployment configuration, wherein the expandable section includes a distal conduit and a proximal conduit in fluid communication with a cannula lumen defined therebetween; advancing an impeller system through the shaft section and into the expandable section, wherein the impeller system includes a distal stabilizer and an impeller coupled to a drive shaft such that the distal stabilizer and the impeller are advanced through the shaft section while in a low profile, delivery configuration while passing through the shaft section; and expanding the distal stabilizer and the impeller into an expanded, deployment configuration when positioned within the expandable section such that the distal stabilizer contacts against an inner surface of the cannula lumen while an outer diameter of the impeller is maintained at a distance from the inner surface of the cannula lumen.

[0037] In another aspect of the method, advancing the cannula may comprise advancing the cannula within a chamber of a heart of the patient body.

[0038] In another aspect of the method, the expandable section of the cannula may be comprised of a scaffold structure such that the distal conduit and the proximal conduit define one or more openings therethrough.

[0039] In another aspect of the method, the expandable section may further comprise a covering or coating upon the scaffold structure such that the distal conduit and the proximal conduit remain uncovered or uncoated.

[0040] In another aspect of the method, the cannula may define a lumen through a length of the shaft section.

[0041] In another aspect of the method, the impeller may be comprised of a single monolithic helical body.

[0042] In another aspect of the method, a portion of the drive shaft may define a helical receiving slot for receiving the impeller.

[0043] In another aspect of the method, the impeller may define an helical open channel along its central region.

[0044] In another aspect of the method, the impeller may be over molded upon a portion of the drive shaft.

[0045] In another aspect of the method, advancing the impeller system may comprise radially expanding the shaft section as the impeller is advanced through the shaft section.

[0046] In another aspect of the method, the impeller may be comprised of one or more helical blades.

[0047] In another aspect of the method, a trailing edge and / or a leading edge of the impeller may be tapered.

[0048] In another aspect of the method, the impeller may further comprise a winglet upon a tip of the impeller.

[0049] In another aspect of the method, the distal stabilizer may be comprised of one or more distal stabilizer arms supported by a distal hub and a proximal hub positioned along the drive shaft.

[0050] In another aspect of the method, the distal hub may be configured to freely float relative to the drive shaft.

[0051] In another aspect of the method, the distal hub may be coupled to a distal bearing assembly such that the distal bearing assembly is not axially constrained on the drive shaft.

[0052] In another aspect of the method, the proximal hub may comprise a rotatable bearing coupled to the drive shaft.

[0053] In another aspect of the method, the proximal hub may be attached to a casing or sheath surrounding the drive shaft and the distal hub may be configured to freely float relative to the drive shaft.

[0054] In another aspect of the method, the proximal hub may be attached to a casing or sheath surrounding the drive shaft and the distal hub may be coupled to a distal bearing assembly positioned along the drive shaft.

[0055] In another aspect of the method, the distal bearing assembly may not be axially constrained along the drive shaft.

[0056] In another aspect of the method, the impeller may be positioned within the distal stabilizer.

[0057] In another aspect of the method, the outer diameter of the impeller may be maintained at a predetermined clearance from an inner surface of the distal stabilizer.

[0058] In another aspect of the method, advancing the impeller system may comprise positioning the impeller at a distal position proximal to the distal conduit within the cannula lumen such that the distal stabilizer is also proximal of the distal conduit.

[0059] In another aspect of the method, advancing the impeller system may comprise positioning the impeller within the expandable section of the cannula along a portion which is relatively stiffer than a remainder of the expandable section.

[0060] In another aspect of the method, the method may further comprise locking a position of the impeller system relative to the cannula.

[0061] In another aspect of the method, the method may further comprise retracting the impeller system proximally into the shaft section while collapsing the distal stabilizer and the impeller.

[0062] Any of these aspects may be combined with one another in any number of combinations and such variations are intended to be within the scope of this description.BRIEF DESCRIPTION OF THE DRAWINGS

[0063] FIG. 1 shows a side view of one variation of a cannula having an expandable section for accommodating an impeller drive shaft system.

[0064] FIG. 2 shows a side view of one variation of an impeller drive shaft system which may be introduced into a cannula.

[0065] FIGS. 3 A and 3B show side views of another variation of a cannula having an expandable section and an impeller system.

[0066] FIG. 3C shows a side view showing how the impeller system of FIG. 3B may be introduced into the interior of the cannula of FIG. 3A within a patient body.

[0067] FIGS. 4A and 4B show detail side views of a distal stabilizer having a distal retaining hub which is free-floating upon a shaft and a proximal stabilizer retention feature.

[0068] FIGS. 5 A and 5B show detail side and end views of yet another impeller drive shaft system having the impeller positioned within the distal stabilizer.

[0069] FIG. 5C shows a detail side view of yet another impeller drive shaft system having a distal stabilizer with an open distal end.

[0070] FIG. 5D shows a detail side view of yet another impeller drive shaft system having both a proximal bearing assembly and a distal bearing assembly.

[0071] FIGS. 6A and 6B show exploded assembly and assembly side views, respectively, of an impeller which may secured within a helical receiving slot of a flexible drive shaft.

[0072] FIGS. 7A to 7C show exploded assembly and assembly side views, respectively, of another impeller variation which uses an open channel with helical guides along the impeller for securement within a helical receiving slot of a flexible drive shaft.

[0073] FIGS. 8 A and 8B show side and partially transparent side views of another impeller variation which may be over molded upon the shaft.

[0074] FIGS. 9A and 9B show side views of additional impeller variations having altered trailing and / or leading edges defined along the impeller blades.

[0075] FIG. 10 shows an end view of yet another impeller variation in which the blade curvature may be altered.

[0076] FIGS. 11A and 1 IB show side views of yet another variation of a cannula device having a shaft section which is selectively expandable to accommodate the advancement and / or retraction of a collapsible impeller assembly.

[0077] FIGS. 12A to 12D show side views of various locations for impeller placement within the interior of the cannula.

[0078] FIG. 13 shows a side view of one particular location for impeller placement with the cannula.DETAILED DESCRIPTION OF THE INVENTION

[0079] In order to achieve a relatively high impeller diameter profile yet maintain a relatively small device insertion profile, a modular approach to assembling a blood flow pump within the patient’ s body may be utilized. By decoupling a cannula and an impellerdrive shaft completely, the blood flow pump may be assembled in place, e.g., within a vessel lumen of the patient’s body, by the clinician.

[0080] BLOOD PUMP SYSTEM

[0081] One variation of an expandable catheter cannula 10 which may be used with the decoupled blood flow pump assembly is shown in the side view of FIG. 1 in which the cannula 10 may include a distal expandable section 12 which can be collapsed into a small bore introducer (e.g., 12 F or less, or 10 F or less) for intravascular delivery. The distal expandable section 12 may be attached to a proximal shaft section 14 which may be nonexpandable or expandable in diameter. The expandable section 12 of the cannula 10 may include a distal conduit entry 18 extending between the distal edge of the expandable section 12 and a distal tip 22 of the cannula 10 to provide an inflow conduit for blood into and through a lumen 16 defined through the cannula 10. A proximal conduit outlet 20 may extend between the proximal edge of the expandable section 12 and the shaft section 14 such that blood entering the distal conduit entry 18, as denoted by the direction of inflow 24, may flow through the lumen 16 and out through the proximal conduit outlet 20, as denoted by the direction of outflow 26. The expandable section 12 may be constructed to be reversibly expandable for intravascular delivery into and from the vasculature when collapsed. The expandable section 12 may include a scaffolding construction, e.g., a stentlike configuration, or other structural configuration to support the deployment of the expandable section 12 when in its expanded shape.

[0082] While the expandable section 12 may be coated or covered to form a fluid- tight wall along its length, it may also be uncoated or uncovered that allows for a blood entry pathway and a proximal uncoated blood exit pathway. When the expandable section 12 is coated or covered, the distal inflow conduit 18 and proximal outflow conduit 20 may remain uncoated or uncovered to allow for the unhindered flow of blood between their structure members. Such a cannula 10 can thus be independently inserted into a standard vascular access introducer sheath and directed over the wire using standard interventional techniques.

[0083] In one example, the expandable section 12 of cannula 10 may be positioned in the left ventricle across the aortic valve such that the distal inflow conduit 18 of the cannula 10 may be placed in the desired chamber (such as the left ventricle in the case of the blood pump being used as a left ventricular assist device). The proximal outflow conduit 20 of the cannula 10 may be positioned in the outflow chamber or in proximity to the outflow chamber of the heart (such the aortic arch in case of the left ventricular assistdevice). In this example, the aortic valve may be located along the outer surface of the expandable section 12 of the cannula 10 separating the inflow and the outflow sections.

[0084] With such a cannula 10, one variation of an impeller system 30, which may be separate from the cannula 10 but used in conjunction, is shown in the side view of FIG. 2. The impeller system 30 may include an impeller 38 having one or more blades which may be flexible and / or collapsible into a smaller profile for delivery purposes. A distal stabilizer 36 assembly may be positioned upon the distal end of the assembly distal to the impeller 38 or the stabilizer 36 may envelope the impeller 38 (as further described below). In either case, the distal stabilizer 36 may be expandible from a low profile, collapsed delivery configuration to an expanded configuration for engaging with, abutting, or otherwise contacting against an inner surface of the expandable section 12 of the cannula 10 for stabilizing a position of the impeller 38 within the expandable section 12 during use when rotated.

[0085] The impeller 38 may be connected via a proximal hub 42 to a flexible drive shaft 34 (e.g., solid rod, cable, multi- stranded solid cable, multi- stranded hollow cable, etc.) that is capable of transmitting torque from the drive motor assembly 44 to the impeller 38 such that the impeller 38 may rotate about its longitudinal axis when rotated by the drive shaft 34. The drive shaft 34 may be further connected or welded to a rotating portion of a distal hub 40 such as a bearing (e.g., journal, needle, roller bearing, or other bearing structures). The drive shaft 34 may also be used to transmit cooling and / or lubrication fluid which can flow out of holes or slots on the rotating journal at the distal hub 40 to aid in both cooling and lubrication. The drive shaft 34 may be housed within a casing or sheath 32 which may be connected to the drive motor assembly 44. The casing or sheath 32 may be fabricated from a polymeric tube which can be supported, for example, with a braid, coil or a laser cut tube reinforcement. The casing or sheath 32 may also allow for lubricating and / or cooling fluid circulation.

[0086] FIGS. 3 A and 3B show side views of another variation of the cannula 50 and impeller system 70, respectively, where the impeller system 70 may be introduced within the interior of the cannula 50. The cannula 50 may include the expandable section 52 extending from a shaft 54 having a relatively smaller diameter than the expandable section 52 when reconfigured from its low profile delivery configuration into its expanded deployment configuration, as shown. The expandable section 52 may include a reconfigurable scaffold, e.g., such as a stent- like structure, which may be at least partially covered or coated along a majority of its length. The uncovered distal portion may formthe distal inflow conduit 58 between the distal tip 62 and the distal end of the expandable section 52 and the uncovered proximal portion may form the proximal outflow conduit 60 between the proximal end of the expandable section 52 and the beginning of the shaft 54 or just distal to the shaft attachment, as shown.

[0087] The impeller system 70 is shown in this variation with the impeller 78 attached along the flexible drive shaft 74 which may further extend distally through the distal stabilizer 76. The drive shaft 74 may be coupled to a rotatable distal hub 80 positioned distal to the distal stabilizer 76 and to a proximal hub 82 positioned proximal to the distal stabilizer 76 to provide a distance between the distal end of the impeller 78 and the proximal end of the distal stabilizer 76. The drive shaft 74 may be further seen extending through the casing or sheath 72.

[0088] When in use, the cannula 50 may be advanced, e.g., intravascularly, within the patient’s body to the location of interest, e.g., through the aortic valve, with the expandable section 52 in a low profile delivery configuration. When suitably positioned within the patient body, the expandable section 52 may be reconfigured to expand, as shown. The impeller system 70 may be introduced into the proximal end of the shaft 54 and through the shaft 54 until the distal stabilizer 76 and impeller 78 are advanced into the lumen 56 of the expandable section 52 of the cannula 50, as shown in the assembly side view of FIG. 3C, to form the blood pump assembly 90. The distal stabilizer 76 may be expanded into its deployed configuration for contacting against or abutting the interior surfaces of the cannula lumen 56 to provide for stabilization of the impeller 78 during its rotation within the cannula lumen 56. The impeller 78 may be expanded to form a diameter which is less than the diameter of the distal stabilizer 76 and / or less than (or equal to) the diameter of the cannula lumen 56 to prevent interference during impeller rotation within the lumen 56 during use.

[0089] Once the impeller system 70 has been deployed within the cannula lumen 56, the impeller 78 may be actuated to rotate such that blood flow from the vessel or chamber is drawn into the distal inflow conduit 58, through the cannula lumen 56, and out the proximal outflow conduit 60 to facilitate the blood flow.

[0090] The expanded impeller 78 may be positioned within the expandable section 52 of the cannula 10 at a predetermined location upon insertion of the impeller system 70 into the cannula lumen 56. For safety purposes, the impeller system 70 may be retracted smoothly when pulled proximally back into the non-expanded shaft section 54 of the cannula 10 prior to or during proximal withdrawal of the blood pump assembly 90 out ofthe patient body. This may be achieved without any significant manipulation or intervention from the user to facilitate ease of use of the system. Accordingly, the proximal end of the expandable cannula 50 may be designed to incorporate a threaded or cam keying feature with a corresponding threaded or cam structure on the impeller system 70 such that once threaded together the impeller 78 may be positioned automatically at its desired location within the cannula lumen 56 and may also be positively locked in place. Furthermore, the threaded mechanism may allow for rotation of the drive shaft 74 with respect to the cannula 50 and hence facilitate the smooth unfurling and expanding of the impeller 78 during or after insertion and curling or folding of the impeller 78 back into the cannula shaft 54 prior to or during assembly withdrawal of the assembly 90 from the patient body.

[0091] The motor 44 may locked either electronically or mechanically to ensure the smooth withdrawal of the casing or sheath 72 by preventing any relative rotational motion between the drive shaft 74 and the casing or sheath 72. Additionally and / or alternatively, the impeller 78 may be powered to have a slow rotation during the pullback of the impeller system 70 relative to the cannula 50 to aid in folding and collapse of the impeller 78 into and through the casing or sheath 72.

[0092] Another aspect of the interlocking feature that allow for a threading in and a small retraction of the drive shaft 74 is that any thrust surfaces of the drive shaft assembly may be separated from a fixed distal end of the casing or sheath 72 prior to locking after insertion of the casing or sheath 72 into the shaft section 54 of the cannula 50. This may facilitate ensuring that the thrust bearing surfaces on the distal end are not in contact at the beginning of any impeller rotation and that the thrust bearing surfaces can come into intermittent contact during operation under worst-case conditions. This may help to ensure less heat generation and wear and may allow for longer operation times of the system.

[0093] When the impeller 78 has been expanded within the expandable section 52 and during particularly during rotation, the outer diameter of the impeller 78 may be prevented from impinging on the interior surfaces of the cannula lumen 56 by providing adequate clearance between the two. However, because larger clearances can result in performance deterioration due to fluid leakage across from the high-pressure side to the low-pressure side through the clearance, there may be a limit on the clearance. Another option may include incorporating a distal stabilizer 76 distal to the impeller 78 that can make contact with or is in close proximity to the interior surfaces the cannula lumen 56 and may move in unison with the expandable section 52. This may ensure that any gyroscopicforces resulting from impeller rotation are minimized or nullified entirely and may further minimize any potential for relative motion between the impeller 78 and expandable section 52.

[0094] DISTAL STABILIZER

[0095] Turning now to the distal stabilizer, the distal stabilizer structure can be configured to be an expanding structure such as a self-expanding stent-like scaffold structure. In one variation, the distal stabilizer may be fabricated from a shape memory alloy, e.g., Nitinol, which may be configured with open cell structures that may allow for fluid flow through the cells between the interconnecting struts. FIG. 4A shows a detail side view of one variation in which the distal stabilizer is configured with one or more distal stabilizer arms 100 (e.g., three arms 100) which are uniformly spaced apart from one another circumferentially and which may extend linearly from corresponding distal arms 102 which may curve or angle away from a distal retaining hub 106 and which may further curve or angle towards a proximal stabilizer retention hub 108 via corresponding proximal arms 104.

[0096] The distal retaining hub 106 may be configured as a circularly shaped member or collar to which each of the distal arms 102 are attached and the distal retaining hub 106 may be further configured to function as a floating end such that the hub 106 has an inner diameter which is larger than the outer diameter of the drive shaft 74. This may allow for the hub 106 to remain unattached to the drive shaft 74 which may accordingly rotate about its longitudinal axis freely while unhindered by the hub 106 and which further facilitates the easy collapse of the distal stabilizer during insertion and / or withdrawal by enabling the hub 106 to slide distally and / or proximally along the drive shaft 74 as the one or more distal stabilizer arms 100 are collapsed or compressed towards the drive shaft 74. The proximal stabilizer retention hub 108 may be attached to each of the proximal arms 104 and may further abut the shoulder 110 formed along the drive shaft 74 which may further prevent the proximal migration of the distal stabilizer as the drive shaft 74 rotates.

[0097] The proximal hub 108 may be retained upon the drive shaft 74 by first hub member 112 (to which the proximal arms 104 may be directly attached) and a second hub member 114 between which a bearing housing 116 may be positioned, as shown in the detail side view of FIG. 4B. Unlike the freely floating distal hub 106, the proximal hub 108 may be retained on the drive shaft but the bearing housing 116 may incorporate one or more bearings such as needles, balls, etc. which are retained within the bearing housing116 while remaining in intermittent contact against an outer surface of the drive shaft 74 particularly during drive shaft rotation.

[0098] Furthermore, each of the one or more distal stabilizer arms 100 may be optionally coated (e.g., ePTFE, silicone, etc.) to facilitate the insertion and / or retraction the interior surfaces of the cannula and to minimize damage to the cannula surfaces resulting from the relative motion between the distal stabilizer and the cannula 50 during insertion, withdrawal, and during operation.

[0099] With any of the impeller designs described herein, the distal stabilizer and impeller may be combined or integrated in yet another variation of the distal stabilizer. As the clearance between the outer diameter of the impeller and the inner diameter of the cannula lumen may influence the ability of the impeller to generate head pressure, the larger clearance may lower the peak head pressure that can be developed while the smaller clearance may raise the peak head pressure that can be developed. However, for a flexible and expandable impeller system, the smaller this clearance the higher the chance that the impeller may impinge upon the inner surface of the cannula lumen which may result in a safety concern. Hence, a clearance ranging between, e.g., 0.25 mm to 3.0 mm, may provide an optimal tradeoff between peak pressure head and safety.

[0100] Another variation of a distal stabilizer 120 is shown in the side view of FIG. 5A and end view of FIG. 5B where the impeller 78 may be incorporated within the body of the distal stabilizer itself. The distal stabilizer 120 may be formed as a reconfigurable structure which may expand from a low profile delivery configuration into its deployed, expanded configuration where one or more distal stabilizer arms 122 may be aligned longitudinally while positioned circumferentially in a uniform manner about the longitudinal axis of the stabilizer. The one or more distal stabilizer arms 122 may be supported by proximal arms 124 and corresponding distal arms 126 which may extend the stabilizer arms 122 radially while aligned or parallel to one another. While three stabilizer arms 122 are shown in this variation, fewer than three or more than three stabilizer arms may be utilized. The stabilizer arms 122 may be interconnected to one another by struts, cross members, or shape cells (e.g., diamond shaped) akin to a stent like structure.

[0101] The distal arms 126 may be coupled to a distal stabilizer hub 128 which is freely floating distally of the drive shaft 74 and uncoupled to the drive shaft 74 or the distal stabilizer hub 128 may be positioned freely about and uncoupled to the drive shaft 74 to allow for the distal and proximal movement of the distal stabilizer hub 128 relative to the drive shaft 74 during reconfiguration between the collapsed low profile shape and thedeployed, expanded shape. The proximal stabilizer hub 130 may be coupled to the casing or sheath 72 to allow for the rotation of the impeller 78 relative to the distal stabilizer arms 122 while remaining secured. The incorporation of the distal stabilizer with the impeller 78 within may allow for intimate or close contact or close proximity between the distal stabilizer arms 122 with the inner surface of the cannula lumen and this close contact or close proximity may allow for the distal stabilizer arms 122 to provide some structural support or rigidity to the portion of the cannula lumen where they are contacting one another. This may also allow for the two to move in unison with the cannula as the cannula is advanced and / or deflected within the patient body. This further ensures that the impeller 78 may rotate close to the center of the cannula lumen when deployed to ensure a uniform clearance 132 between the impeller 78 and the cannula wall and minimizing pressure leakage and / or the chance of impingement of the impeller 78 and cannula lumen.

[0102] Additionally and / or alternatively, the stiffness of the expandable portion of the cannula may be reduced in regions of the cannula where the distal stabilizer is not located to further inhibit impingement of the impeller 78 against the interior cannula walls. Hence, the expandable portion may result in a scaffold structure having at least two sections of varying stiffness where a first section may be relative stiffer than a second section of the expandable portion. The distal stabilizer and / or impeller 78 may be positioned within such a scaffold structure along the section having the relatively greater stiffness. Alternatively, the distal stabilizer and / or impeller 78 may be positioned within the scaffold structure along the section having the relatively lesser stiffness. This may minimize any transfer of bending forces from the distal stabilizer and / or impeller impinging upon the walls of the cannula to the remainder of the expandable portion of the cannula. This can be achieved by either changing the laser cut pattern of the expandable portion, altering the thickness of the stent struts, the width of the struts, or a combination of all in the desired regions.

[0103] FIG. 5C shows a side view of another variation where the distal stabilizer arms 122 may be supported by the proximal arms 124 but may omit the distal arms 126 such that the distal portion may have an open distal end 134.

[0104] The distal stabilizing structure may be configured such that it exerts a radial outward force on the inner walls of the cannula expandable portion 52 in its expanded state. The structure may further provide rigidity to the expandable portion 52 to ensure a more stable structure for rotation of the impeller 78. Furthermore, the distal stabilizing structure may be connected to the casing or sheath 72 in close proximity to the impeller 78to render a configuration for supporting the impeller 78 in a centered position within the cannula lumen 56. The distal stabilizing structure may remain unconnected to the rotating drive shaft 74 eliminating the need for a bearing surface. The distal stabilizing structure can also facilitate the collapse of the impeller 78 during withdrawal into the shaft section 54 of the cannula either with or without rotation of the impeller 78 during collapse and withdrawal into the cannula. In other variations, the distal stabilizing arms may also be positioned proximal to the impeller 78 as well.

[0105] FIG. 5D shows a side view of yet another variation where the distal hub 128 of the stabilizer may be coupled to a distal bearing assembly 136 and a proximal bearing assembly 138 incorporated distally of the proximal hub 130. The distal bearing assembly 136 is not constrained on the drive shaft 74 and is free to move axially along the drive shaft 74 for facilitating the reconfiguration of the impeller and distal stabilizer system. While the drive shaft 74 may slide axially relative to the distal bearing assembly 136 and the drive shaft 74 may freely rotate relative to distal bearing assembly 136, the distal bearing assembly 136 may incorporate a bearing assembly (as described herein) which provides for intermittent contact between the drive shaft 74 and the distal bearing assembly 136. This contact may maintain the relative transverse positioning of the distal bearing assembly 136 and drive shaft 74 (and hence the impeller 78) relative to one another while leaving the axial and rotational movement unhindered. Hence, this configuration may provide further support to the impeller 78 and thus reduce vibration of the system and enhance overall system stability. Greater stability may further help in reducing the clearance 132 between the outer diameter of the impeller 78 and the inner diameter of the expandable section of the canula thereby improving performance.

[0106] IMPELLER

[0107] Turning now to the impeller, the impeller and hub assembly may facilitate their assembly and manufacturing while enhancing the safety profile of the impeller by eliminating stress concentration points and further facilitating ease of collapse into a low profile, delivery configuration. FIGS. 6A and 6B show a variation in the detail exploded side view of FIG. 6A and assembly side view of FIG. 6B. In this variation, the flexible drive shaft 140 may be configured to have a hub 142 which is designed to have a helical receiving slot 144 defined along the drive shaft 140 and which terminates at a proximal stop 146. The impeller 148 may be designed to have a central guidance feature that runs through its central axis and creates the helical path of the impeller blades, for example, a formed helical channel or groove 150, which corresponds to the helical receiving slot 144defined along the drive shaft 140. The formed helical channel or groove 150 may be introduced into the helical receiving slot 144 and the impeller 148 may be advanced until it reaches the proximal stop 146. The impeller 148 may be retained within the helical receiving slot 144 optionally with or without the use of adhesives. Additionally and / or alternatively, mechanical features such as detents, clips, or other fasteners may be used to optionally secure the impeller 148 within the slot 144.

[0108] Alternatively, the helical shape of the impeller 148 alone, with no explicit central guidance feature 150 may serve the purpose of guiding the insertion of the impeller helical receiving slot 144 and enabling its retention within the receiving slot 144. The assembly may then be attached, for example, to the bearing assembly 108 connected to the drive shaft. Such a construction may allow for improved balance of the impeller 148 and hence better rotor dynamics and performance. This approach may also secure the impeller 148 upon the drive shaft 140 without the use of any adhesives.

[0109] FIGS. 7 A and 7B show yet another variation in the detail exploded side view and in the assembly side view of FIG. 7C. In this variation, the impeller 162 may be formed to have an helical open channel 164 along its central region with helical guides 146 defined along the length of the open channel 144 for engagement with an helical receiving slot 144 defined along the length of the drive shaft 140. The drive shaft 140 may include a closed distal end 160 which presents a smooth atraumatic tip as the helical guides 166 may slide over and upon the drive shaft 140 for engagement with the helical receiving slot 144. The impeller 162 may be rotatingly advanced upon the drive shaft 140 until it abuts the proximal stop 146. The blades of the impeller 162 may be formed upon a hollow polymeric structure which may form the open channel 164 or the channel may be attached to the drive shaft 140 through other processes, such as dip coating. Alternatively, the blades of the impeller 162 may be formed separately and then attached directly to the drive shaft 140.

[0110] In either of the design variations above, the blades of the impeller are formed as a single monolithic helical body retained by its passage through the helical groove of the central hub. Accordingly, there are no fixed junctions between the flexible impeller blade and the rigid hub structure, thereby eliminating a key stress concentration source in alternative approaches that seek to fixedly attach the flexible material of the impeller blades to the more rigid central shaft. With the blades of the impeller formed as a single structure that passes through the center of the hub, any tensile loads created by the rotation of the impeller exclusively produce tension that is carried completely by theimpeller as these tension forces do not work to separate the impeller from the hub. Furthermore, the shear forces produced by the rotation during operation of the impeller in the fluid medium are born by the full width of the impeller material at the interface to the hub. Additionally, the connection of the blades through the hub allows the hub diameter to be maximized thereby maximizing the rigidity of the hub to bending loads.

[0111] In yet other variations, the expandable impeller may be fabricated through other processes. For example, the blades of the impeller may be molded separately and then assembled using the guidance feature on the blade by threading into the slot defined along the hub until it comes to a stop at the distal end or by inserting the blades through the slot on the hub and pulling the blades through until the guidance feature on the blades or the geometry of the impeller helix itself locks the impeller into position with the corresponding grove of the hub. Such a construction allows for balancing of the impeller and hence improved rotor dynamics and performance. Additionally, these impeller construction approaches capture the impeller on the shaft without the need for any adhesives and therefore cannot be released into the patient body due to adhesive failure, thereby providing an improved safety profile.

[0112] In yet another variation, an impeller 178 may be over molded directly upon the shaft extension 172 of the drive shaft 170, as shown in the detail side view of FIG. 8A and corresponding side view of FIG. 8B where the impeller 178 is partially transparent to illustrate the securement details within. The shaft extension 172, which may be metallic or rigid plastic, may be configured to define one or more receiving slots 174 such as channels which are defined along the surface of the shaft extension 172. One or more locking features 180 such as shoulders, detents, radially extending projections, etc. may also be defined along the length of the surface of the shaft extension 172. As the impeller 178 is placed over the shaft extension 172 within the impeller channel 176, the impeller channel 176 may be molded such that material from the impeller 178 flows into the one or more receiving slots 174 along the shaft extension 172 and portions of the impeller channel 176 may also be formed around the one or more locking features 180 such that the impeller 178 becomes locked in place along the drive shaft 170.

[0113] The impeller itself is generally configured to be flexible, tough, and tear resistant and may be fabricated from a single material or may be fabricated as a composite structure. In one example, the impeller may be fabricated from a single polymeric structure of a tough, tear-resistant material which is also conducive to high volume manufacturing processes such as molding. Examples of such materials may include thermoplasticelastomers (TPEs), thermoplastic urethanes (TPUs), polyurethane, etc. The impeller shafts may also be fabricated of a metallic or alloy material such as a stainless steel, nickeltitanium alloy, etc. In other examples, the impeller may be fabricated of a reinforcing frame or scaffold having a polymer coating covering the frame or scaffold.

[0114] While the different variations of the impellers illustrate impellers having one or two helical blades, the impellers may be fabricated to have a single blade or more than two blades and the number of blades are not limited. Furthermore, while the blades are shown with helically shaped blades, other blade variations may be used such as flat- bladed disc shapes, pitched blades, propeller blades, etc. The variations having a helical screw type blade may be used to effectuate collapse, expansion, and ease of manufacture and assembly while meeting the performance requirements; however, any number of blade configurations may also be used with any of the variations described herein and in any number of combinations.

[0115] Aside from the impeller blade type, the blades of the impeller may also be varied. For instance, FIG. 9A shows one variation in the side view of an impeller 190 having a trailing edge 192 which is not square to the longitudinal axis of the impeller but is configured to taper in order to facilitate collapse. The trailing edge of the blade may be tapered between the angles of, e.g., 0 and 45 degrees, in which the taper may be produced by a curve. The inclusion of such a tapered feature may facilitate the collapse and withdrawal of the impeller 190 into the cannula for removal.

[0116] Another variation is shown in the side view of the impeller 194 of FIG. 9B which shows a leading edge 196 which is instead tapered. The tapered leading ledge 196 may also range similarly as the trailing edge 192 and may reduce the deformation and risk of fluttering of the blade tip thereby improving the efficiency of the impeller 194 to generate head and flow.

[0117] In yet another variation, the impeller 194 may also be configured to have the tapered leading edge 196 and the tapered trailing edge 192 both on the same impeller 194 if so desired.

[0118] The radius of the blade curvature 202 may also have an impact on impeller performance for fluid flow versus pressure head generated. During operation at high speeds, the ability of the impeller 200 to generate and maintain pressure head levels may depend in part on the ability of the blades 206 to retain their shape. A radius of blade curvature 202 ranging between, e.g., 5 to 40 degrees, may provide a good balance andtradeoff between performance and collapse and / or expansion and shape retention, as illustrated in the end view of impeller 200 in FIG. 10.

[0119] Additionally, the blades 206 may be designed to be relatively thicker at the root 208 in the vicinity of the hub than at their tips, further minimizing blade deflection under load and improving performance. The thickness of the blades also has an impact on blade deformation and collapse. Generally, higher thickness leads to more difficulty in collapse. A ratio of root thickness to tip thickness may range between, e.g., 1.0 to 2.0, and may balance structural rigidity and collapsibility.

[0120] In yet another variation, winglets 204 may be configured on the ends of the blades 206 and may help prevent pressure loss past the blade tip and thereby prevent loss of pumping efficiency. A winglet thickness-to-height ratio may range between, e.g., 0.5:1 to 1.5:1, or between, e.g., 0.75:1 to 1:1. Such winglet thickness-to-height ratios may provide for a flexible blade design application, e.g., for both manufacturability and function. Additionally, the ratio of the thickness of the winglet 204 to the thickness of the blade 206 at the root 208 of the winglet 204 may range between, e.g., 0.25: 1 to 1.5:1, or between, e.g., 0.5:1, to provide for a flexible blade design application for both manufacturability and function.

[0121] Impellers may also be designed to have a constant pitch or a variable pitch. The degree of pitch variation along the length of the impeller may influence the performance characteristics of the impeller as well as its manufacturability (e.g., moldability). A constant pitch impeller, where no pitch variability exists along the length of the impeller, may be the easiest to manufacture from a molding perspective. The pitch and length of the impeller may influence its flow vs pressure head characteristics. For flexible impellers, a pitch may range between, e.g., 7 mm to 23 mm, with a length ranging between, e.g., 4 mm to 14 mm, to optimize performance while balancing other requirements of an expandable impeller.

[0122] An impeller incorporating any one or more of the parameter variations, e.g., tapered leading edge and / or tapered trailing edge, varied radius of blade curvature, various ratios of root to tip thicknesses, various winglet thickness-to-height ratios, constant pitch or a variable pitch, etc. may all be incorporated in any number of combinations and values within a single impeller design and are all intended to be within the scope of this description. Moreover, such a single impeller design may be incorporated into any of the variations of the impeller systems described and / or any of the variations of the cannulasystems described in any number of combinations and are all intended to be within the scope of this description.

[0123] BLOOD PUMP ASSEMBLY

[0124] Turning now to positioning of the impeller system within the cannula, both the cannula and impeller system may be configured to maintain a relatively low delivery profile to maintain a relatively small insertion profile at the arterial entry point in order to minimize vascular closure-related complications. Because vessels such as arteries are generally compliant and may be temporarily stretched within limits without impacting their entry bores, the devices here may be configured to incorporate a selectively radially expandable introducer in one variation without impacting the entry profile.

[0125] A selectively expandable construction can be incorporated into the shaft section 224 of the cannula 220 and into an introducer 226 within which the cannula 220 may be advanced into the patient body. The shaft section 224 as well as the introducer 226 may be fabricated by, e.g., laser cutting a tube such as a shape memory alloy tube, having the desired inner diameter. The radially expandable sections may be patterned to allow for their radial expansion up to a desired maximum inner diameter. These patterns may be configured to enable a sufficient radial, elastic strength which may collapse back to the initial diameters once the higher profile section of the inserted device passes through.These radially expandable sections may also be coated with a flexible polymer such as thin silicone film, polyurethane film, etc. that may allow for the expansion and collapse with the laser cut frame. Various coating processes such as polymer reflow, spray coating, dip coating, etc., may be used as well. Alternatively, the expandable sections may be fabricated by the use of braiding and lamination such as the use of dip coating or spray coating a flexible polymer. With such a construction, only the portion around the larger device outer diameter may temporarily bulge out up to the desired maximum diameter while the remaining portions of the introducer may retain its initial inner diameter.

[0126] One variation is shown in the side views of FIGS. 11A and 1 IB which illustrate the impeller system 70 advanced and / or retracted from within the cannula 220. The introducer 226 and a section of the shaft section 224 may be constructed to accommodate a temporary radial expansion so that as the collapsed impeller 78 is introduced into the introducer lumen 228, contact between the collapsed impeller 78 and the inner walls of the cannula shaft section 224 may force the shaft section 224 and introducer 226 to expand radially along an expandable section 230 along the cannula shaft section 224 and introducer 226 from an initial diameter of, e.g., 9 F, to an expandeddiameter of, e.g., 11 F to 12 F, during advancement or retraction 232. As the impeller 78 passes through, the walls of the lumen may revert to their original diameters, for instance, as the impeller 78 is advanced distally into the expandable section 222 which may have a low profile delivery diameter of, e.g., 9 F, to expanded inner diameter of, e.g., 21 F.

[0127] The use of a selectively expandable section may allow for the use of impellers 78 having a larger size which may improve pump efficiency and may further allow for pump operation at lower speed relative to a smaller impeller thus further reducing hemolysis and bleeding.

[0128] With the advancement and introduction of, e.g., the impeller 78 integrated within the distal stabilizer 120 (as shown in FIGS. 5 A and 5B or 5C or 5D), into and through the interior of the expandable section 52 of cannula 50, the impeller 78 may be positioned at any number of locations within the cannula lumen 56. FIGS. 12A to 12D show various relative positioning of the impeller 78 within the cannula lumen 56. Each of the locations may offer certain tradeoffs with respect to performance, safety and ease of use.

[0129] FIG. 12A shows one variation in which the impeller 78 may be located within a distal position 240 where the impeller 78 is positioned just proximal to the distal inflow conduit 58 within the cannula lumen 56 such that the arms of the distal stabilizer 120 are also just proximal of the distal inflow conduit 58. Once desirably positioned, the relative position of the impeller system and cannula may be secured to prevent any further movement during a pumping procedure. With the completion of the pumping procedure, the two may be detached to allow for the removal of the impeller system from the cannula or the removal of both the impeller system and cannula from the patient body.

[0130] FIG. 12B shows another variation in which the impeller 78 may be located within a mid position 242 where the impeller 78 is positioned approximately midway between the distal inflow conduit 58 and the proximal outflow conduit 60 within the cannula lumen 56. Once desirably positioned, the relative position of the impeller system and cannula may be secured to prevent any further movement during a pumping procedure. With the completion of the pumping procedure, the two may be detached to allow for the removal of the impeller system from the cannula or the removal of both the impeller system and cannula from the patient body.

[0131] FIG. 12C shows another variation in which the impeller 78 may be located within a proximal position 244 where the impeller 78 is positioned within the cannula lumen 56 just distal to the proximal outflow conduit 60. Once desirably positioned, therelative position of the impeller system and cannula may be secured to prevent any further movement during a pumping procedure. With the completion of the pumping procedure, the two may be detached to allow for the removal of the impeller system from the cannula or the removal of both the impeller system and cannula from the patient body.

[0132] FIG. 12D shows another variation in which the impeller 78 may be located within a terminal proximal position 246 where the impeller 78 is positioned at the proximal outflow conduit 60 or directly within the proximal outflow conduit 60. Once desirably positioned, the relative position of the impeller system and cannula may be secured to prevent any further movement during a pumping procedure. With the completion of the pumping procedure, the two may be detached to allow for the removal of the impeller system from the cannula or the removal of both the impeller system and cannula from the patient body.

[0133] FIG. 13 shows one position of the impeller 78 located within a distal position 240 where the impeller 78 is positioned just proximal to the distal inflow conduit 58 within the cannula lumen 56 such that the arms of the distal stabilizer 120 are also just proximal of the distal inflow conduit 58, similar to the position shown in FIG. 12A. This distal position 240 may provide for minimal relative motion between the cannula 50 and the rotating impeller 78 while allowing for enhanced rigidity of the cannula lumen 56 in the region of the distal stabilizer 120 thus increasing the uniformity of the clearance between the fixed cannula elements and the rotating impeller 78 during use.

[0134] The applications of the devices and methods discussed above are not limited to the fields of blood pumps but may include any number of further applications in other fields. Modification of the above-described assemblies and methods for carrying out the invention, combinations between different variations as practicable, and variations of aspects of the invention that are obvious to those of skill in the art are intended to be within the scope of the claims.

Claims

CLAIMSWhat is claimed is:

1. A circulatory support system, comprising: a cannula having an expandable section extending from a shaft section, wherein the expandable section includes a distal conduit and a proximal conduit in fluid communication with a cannula lumen defined therebetween; an impeller system having a distal stabilizer and an impeller coupled to a drive shaft, wherein the distal stabilizer and the impeller are reconfigurable between a low profile delivery configuration when passing through the shaft section and an expanded deployed configuration when positioned within the cannula lumen, wherein the distal stabilizer in its expanded deployed configuration contacts against an inner surface of the cannula lumen while an outer diameter of the impeller is maintained at a distance from the inner surface of the cannula lumen.

2. The system of claim 1 wherein the expandable section of the cannula is comprised of a scaffold structure such that the distal conduit and the proximal conduit define one or more openings therethrough.

3. The system of claim 2 wherein the expandable section further comprises a covering or coating upon the scaffold structure such that the distal conduit and the proximal conduit remain uncovered or uncoated.

4. The system of claim 1 wherein the expandable section of the cannula comprises a scaffold structure having at least two sections of varying stiffness.

5. The system of claim 1 wherein the cannula defines a lumen through a length of the shaft section.

6. The system of claim 1 wherein the impeller is comprised of a single monolithic helical body.

7. The system of claim 1 wherein the impeller further comprises a central guidance feature along a central axis.

8. The system of claim 1 wherein a portion of the drive shaft defines a helical receiving slot for receiving the impeller.

9. The system of claim 1 wherein the impeller defines a helical open channel along its central region.

10. The system of claim 1 wherein the impeller is over molded upon a portion of the drive shaft.

11. The system of claim 1 wherein the impeller is comprised of one or more helical blades.

12. The system of claim 1 wherein a trailing edge and / or a leading edge of the impeller is tapered.

13. The system of claim 1 wherein the impeller further comprises a winglet upon a tip of the impeller.

14. The system of claim 1 wherein the distal stabilizer is comprised of one or more distal stabilizer arms supported by a distal hub and a proximal hub positioned along the drive shaft.

15. The system of claim 14 wherein the distal hub is configured to freely float relative to the drive shaft.

16. The system of claim 14 further comprising a distal bearing assembly coupled to the distal hub such that the distal bearing assembly is not axially constrained on the drive shaft.

17. The system of claim 14 wherein the proximal hub comprises a rotatable bearing coupled to the drive shaft.

18. The system of claim 14 wherein the proximal hub is attached to a casing or sheath surrounding the drive shaft and the distal hub is configured to freely float relative to the drive shaft.

19. The system of claim 14 wherein the proximal hub is attached to a casing or sheath surrounding the drive shaft and the distal hub is coupled to a distal bearing assembly positioned along the drive shaft.

20. The system of claim 19 wherein the distal bearing assembly is not axially constrained along the drive shaft.

21. The system of claim 1 wherein the impeller is positioned within the distal stabilizer.

22. The system of claim 21 wherein the outer diameter of the impeller is maintained at a predetermined clearance from an inner surface of the distal stabilizer.

23. The system of claim 1 wherein the impeller is positioned at a distal position proximal to the distal conduit within the cannula lumen such that the distal stabilizer is also proximal of the distal conduit.

24. The system of claim 1 wherein the shaft section of the cannula is configured to expand radially when the impeller is passed therethrough.

25. A method of deploying a circulatory support system, comprising: advancing a cannula intravascularly within a patient body to a predetermined position, wherein the cannula includes an expandable section extending from a shaft section such that the expandable section is advanced while in a low profile, delivery configuration; reconfiguring the expandable section to an expanded, deployment configuration, wherein the expandable section includes a distal conduit and a proximal conduit in fluid communication with a cannula lumen defined therebetween; advancing an impeller system through the shaft section and into the expandable section, wherein the impeller system includes a distal stabilizer and an impeller coupled toa drive shaft such that the distal stabilizer and the impeller are advanced through the shaft section while in a low profile, delivery configuration while passing through the shaft section; and expanding the distal stabilizer and the impeller into an expanded, deployment configuration when positioned within the expandable section such that the distal stabilizer contacts against an inner surface of the cannula lumen while an outer diameter of the impeller is maintained at a distance from the inner surface of the cannula lumen.

26. The method of claim 25 wherein advancing the cannula comprises advancing the cannula within a chamber of a heart of the patient body.

27. The method of claim 25 wherein the expandable section of the cannula is comprised of a scaffold structure such that the distal conduit and the proximal conduit define one or more openings therethrough.

28. The method of claim 27 wherein the expandable section further comprises a covering or coating upon the scaffold structure such that the distal conduit and the proximal conduit remain uncovered or uncoated.

29. The method of claim 25 wherein the cannula defines a lumen through a length of the shaft section.

30. The method of claim 25 wherein the impeller is comprised of a single monolithic helical body.

31. The method of claim 25 wherein a portion of the drive shaft defines a helical receiving slot for receiving the impeller.

32. The method of claim 25 wherein the impeller defines an helical open channel along its central region.

33. The method of claim 25 wherein the impeller is over molded upon a portion of the drive shaft.

34. The method of claim 25 wherein advancing the impeller system comprises radially expanding the shaft section as the impeller is advanced through the shaft section.

35. The method of claim 25 wherein the impeller is comprised of one or more helical blades.

36. The method of claim 25 wherein a trailing edge and / or a leading edge of the impeller is tapered.

37. The method of claim 25 wherein the impeller further comprises a winglet upon a tip of the impeller.

38. The method of claim 25 wherein the distal stabilizer is comprised of one or more distal stabilizer arms supported by a distal hub and a proximal hub positioned along the drive shaft.

39. The method of claim 25 wherein the distal hub is configured to freely float relative to the drive shaft.

40. The method of claim 25 wherein the distal hub is coupled to a distal bearing assembly such that the distal bearing assembly is not axially constrained on the drive shaft.

41. The method of claim 25 wherein the proximal hub comprises a rotatable bearing coupled to the drive shaft.

42. The method of claim 25 wherein the proximal hub is attached to a casing or sheath surrounding the drive shaft and the distal hub is configured to freely float relative to the drive shaft.

43. The method of claim 25 wherein the proximal hub is attached to a casing or sheath surrounding the drive shaft and the distal hub is coupled to a distal bearing assembly positioned along the drive shaft.

44. The method of claim 43 wherein the distal bearing assembly is not axially constrained along the drive shaft.

45. The method of claim 25 wherein the impeller is positioned within the distal stabilizer.

46. The method of claim 45 wherein the outer diameter of the impeller is maintained at a predetermined clearance from an inner surface of the distal stabilizer.

47. The method of claim 25 wherein advancing the impeller system comprises positioning the impeller at a distal position proximal to the distal conduit within the cannula lumen such that the distal stabilizer is also proximal of the distal conduit.

48. The method of claim 25 wherein advancing the impeller system comprises positioning the impeller within the expandable section of the cannula along a portion which is relatively stiffer than a remainder of the expandable section.

49. The method of claim 25 further comprising locking a position of the impeller system relative to the cannula.

50. The method of claim 25 further comprising retracting the impeller system proximally into the shaft section while collapsing the distal stabilizer and the impeller.

Images