Blood pump with improved liner

Abstract

Disclosed herein is a blood pump that may include one or more struts configured to couple to a catheter, the strut(s) defining a housing having a blood inlet and a blood outlet, the blood pump having an inner surface and an outer surface facing opposite the inner surface. The blood pump may include an inner coating disposed on the inner surface at the blood inlet and extending toward the blood outlet, and an outflow tube coupled to the outer surface, the outflow tube overlying the blood outlet and overlying at least a first portion of the inner coating and extending axially beyond the blood outlet. The blood pump may include an impeller disposed within the housing, the impeller including at least one blade. Preferably, the axial length of the inner coating is configured to span no more than 20% of the overall length of the impeller.

Description

[Technical Field]

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS This disclosure claims priority to U.S. Provisional Patent Application No. 63 / 417,029, filed October 18, 2022, the entire contents of which are incorporated herein by reference.

[0002] The present disclosure is directed to blood pumps, and more particularly to blood pumps having liners modified to house specific impellers. [Background technology]

[0003] Conventional blood pumps use an impeller within a housing to move blood through a patient's body. To effectively assist the patient, blood pumps must meet certain performance characteristics. Typically, relatively long impellers are used to meet some of these characteristics, as shorter rotors result in reduced hydraulic output. Summary of the Invention [Problem to be solved by the invention]

[0004] However, as the need for smaller blood pumps increases, ways of increasing hydraulic output with smaller rotors will be required. [Means for solving the problem]

[0005] In various aspects, a blood pump can be provided that may include one or more struts (e.g., made of nitinol) configured to couple to a catheter. The one or more struts can define a housing having a blood inlet and a blood outlet, the one or more struts having an inner surface and an outer surface facing opposite the inner surface. The blood pump can include an inner coating (e.g., made of polyurethane) disposed on the inner surface at the blood inlet and extending toward the blood outlet. The blood pump can include an outflow tube coupled to the outer surface. The outflow tube can overlie the blood outlet and can overlie at least a first portion of the inner coating. The outflow tube can extend axially beyond the blood outlet. The blood pump can include an impeller disposed within the housing, the impeller including at least one blade. In some embodiments, a wrap angle of the at least one blade relative to a central axis can be at least 100 degrees, at least 180 degrees, and / or at least 200 degrees.

[0006] In some embodiments, the leading edge angle of at least one blade relative to the central axis can be equal to the trailing edge angle of at least one blade relative to the central axis. In some embodiments, the leading edge angle and the trailing edge angle are between 55 and 60 degrees. In some embodiments, the axial length of at least one blade is 7.5 mm or less, 7 mm or less, and / or 6.5 mm.

[0007] In some embodiments, the blood pump may include an outer coating disposed on an outer surface of one or more struts and coupled to the outflow tubing. The outer coating may be disposed at the blood inlet and extend without extending beyond the trailing edge of the inner coating. In some embodiments, the blood pump may not have an outer coating disposed on the outer surface of one or more struts.

[0008] In some embodiments, the axial length of the inner coating may be configured to correspond to the length of at least one blade that is 20% or less of the overall length of the impeller.

[0009] In some embodiments, the axial length of the inner coating is configured to correspond to a length of the impeller that is no greater than 20% of the total length of the impeller, no greater than 15% of the total length of the impeller, and / or no greater than 10% of the total length of the impeller.

[0010] In some embodiments, the leading edge of at least one blade may be free of the inner coating and configured to be positioned a particular distance from the trailing edge of the inner coating.

[0011] In various embodiments, a blood pump can be provided. The blood pump can include one or more struts coupled to a catheter, the one or more struts can define a housing having a blood inlet and a blood outlet, the one or more struts having an inner surface and an outer surface opposite the inner surface. The blood pump can include an inner coating disposed on the inner surface at the blood inlet and extending toward the blood outlet. The blood pump can include an outflow tube coupled to the outer surface, the outflow tube can overlie the blood outlet, can overlie at least a first portion of the inner coating, and can extend axially beyond the blood outlet. The blood pump can include an impeller disposed within the housing, the impeller including at least one blade.

[0012] In various embodiments, a blood pump may be provided. The blood pump may include a pump housing coupled to a catheter configured for insertion into a blood vessel. The pump housing may include an inner layer disposed on an inner surface of a stretchable mesh layer defining a blood inlet and a blood outlet. The inner layer may have a first end at the blood inlet and a second end axially offset a first predetermined distance (D1) from the first end. The blood pump may include an impeller disposed within the pump housing, the impeller including at least one blade. The impeller may have a first end and a second end, the first end of the impeller may be axially offset a second predetermined distance (D2) from the first end of the inner layer. The second end of the impeller may be axially offset a third predetermined distance (D3) from the first end of the inner layer. D3 may be greater than D2, such that either D2≧D1, or D1−D2≦20% of the axial length of the impeller.

[0013] In various aspects, a system can be provided that includes a blood pump as disclosed herein and a controller operably coupled to the blood pump.

[0014] In various aspects, a kit can be provided that includes a blood pump as disclosed herein and a controller configured to be operably coupled to the blood pump. [Brief explanation of the drawings]

[0015] The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate several embodiments of the present invention and, together with the general description of the invention given above and the detailed description of the embodiments given below, serve to explain the principles of the invention. [Figure 1] FIG. 2 is an explanatory diagram showing a part of a blood pump. [Figure 2] FIG. 2 is an explanatory diagram showing a part of a blood pump. [Figure 3A] FIG. [Figure 3B] FIG. 2 is an end view of the impeller. [Figure 4A]1 is a graph illustrating flow rates at different pressure heads for an embodiment of a blood pump and a reference blood pump. [Figure 4B] 1 is a graph illustrating hydraulic efficiency at different flow rates for an embodiment of a blood pump and a reference blood pump. [Figure 5] FIG. 1 is a schematic diagram of the use of a blood pump. [Figure 6A] 1A-1C are schematic cross-sectional views showing different arrangements and combinations of inner coatings, struts, outer coatings, and outflow layers. [Figure 6B] 1A-1C are schematic cross-sectional views showing different arrangements and combinations of inner coatings, struts, outer coatings, and outflow layers. [Figure 6C] 1A-1C are schematic cross-sectional views showing different arrangements and combinations of inner coatings, struts, outer coatings, and outflow layers. [Figure 6D] 1A-1C are schematic cross-sectional views showing different arrangements and combinations of inner coatings, struts, outer coatings, and outflow layers. [Figure 6E] 1A-1C are schematic cross-sectional views showing different arrangements and combinations of inner coatings, struts, outer coatings, and outflow layers.

[0016] It should be understood that the accompanying drawings are not necessarily drawn to scale and show somewhat simplified representations of various features illustrating the underlying principles of the present invention. The specific design features of the sequences of operations disclosed herein, including, for example, the specific dimensions, orientations, locations, and shapes of the various elements shown, are determined in part by the specific intended application and use environment. Certain features of the illustrated embodiments may be enlarged or distorted relative to other features to facilitate their visibility and understanding. In particular, for example, minor features may be bolded for clarity or illustrative purposes. DETAILED DESCRIPTION OF THE INVENTION

[0017] The following description and drawings merely illustrate the principles of the present invention. Accordingly, it will be understood that those skilled in the art can devise various configurations that embody the principles of the present invention and fall within the scope of the present invention, even if not explicitly described or shown herein. Furthermore, it should be recognized that all examples mentioned herein are expressly intended solely for illustrative purposes, primarily to enable the reader to understand the principles of the present invention and the concepts contributed by the inventor(s) to further advance the art, and are not intended to be limited to such specifically mentioned examples and conditions. Furthermore, the term "or" used herein is non-exclusive unless otherwise indicated (e.g., "otherwise" or "or alternatively"). Furthermore, the various embodiments described herein are not necessarily mutually exclusive, as multiple embodiments may be combined with one or more other embodiments to form new embodiments.

[0018] Many of the innovative teachings of the present application will be described with particular reference to presently preferred exemplary embodiments. However, it should be understood that this class of embodiments is merely a small sample of the many advantageous uses of the innovative teachings herein. In general, statements made in the specification of the present application do not necessarily limit the various claimed inventions. Moreover, some statements may apply to some inventive features but not to others. Those skilled in the art, once informed of the teachings herein, will understand that the present invention is applicable to a variety of other technical fields or embodiments.

[0019] Blood pumps often include an impeller near the end of a catheter so that the impeller can enter the patient's body and move blood from one location to another. Blood pumps typically have some form of exterior surrounding the impeller to affect the blood flow generated by the impeller.

[0020] 1, one embodiment of a blood pump can be provided. Blood pump 1 includes a housing 10 coupled to a catheter 20. Typically, the distal end of the catheter will be coupled to the proximal end of the housing, although other configurations are possible.

[0021] The housing includes a series of struts 11, which house an impeller 14 having at least one blade 15. Rotation of the impeller about a central axis causes blood to flow, for example, from a blood inlet 12 to a blood outlet 13. The housing includes an inner coating layer 18 and an outer coating layer 19 around the struts. The inner coating can define an inner surface. The inner surface can be a smooth surface. As used herein, the term "smooth surface" refers to a surface that is free of protrusions, cavities, depressions, vents, or other such irregularities that extend from (or into) the surface for more than a specified distance. This distance is preferably 0.5 mm or less, more preferably 0.25 mm or less, and even more preferably 0.1 mm or less.

[0022] The coating may extend a fixed distance 40 from the blood inlet toward the blood outlet. An outflow tube 30 may be bonded to the outer coating layer. The outflow tube may overlie the blood outlet. The impeller may be offset a predetermined distance 41 from the blood inlet. The impeller may be positioned such that a leading edge 16 of the impeller is covered by the coating layer. A trailing edge 17 of the impeller may also be covered by the coating or may extend beyond the trailing edge of the coating. However, if the impeller extends beyond the coating, at least a portion 51 of the total length 50 of the impeller is covered by the coating layer. In some embodiments, the portion 51 is at least 60% of the length of the impeller (i.e., the axial length of the portion 51 ≥ 60% × the length of the impeller 50). In some embodiments, the portion 51 is 50-60% of the length of the impeller (i.e., 50% × the length of the impeller 50 ≤ the axial length of the portion 51 ≤ 60% × the length of the impeller 50).

[0023] In some embodiments, a mesh 60 may be included. The mesh 60 may define openings smaller than the openings defined by the struts forming the housing. In some embodiments, the mesh may be directly bonded to the struts forming the housing. In some embodiments, the mesh may be directly bonded to one or more struts 61 upstream (in the direction of blood flow) from the struts forming the housing. In some embodiments, the mesh may not be directly bonded to any struts. The mesh may be located upstream from the impeller. In some embodiments, the mesh may be located within a volume of space defined by the struts. In some embodiments, the mesh may be located outside the struts.

[0024] Referring to FIG. 2, in some embodiments, the blood pump 100 may include one or more struts 111. In some embodiments, the struts may form an expandable mesh layer. The strut(s) may be any suitable material, such as Nitinol. In some embodiments, the strut(s) may be configured to couple to a catheter 120. In some embodiments, the housing may be coupled to a catheter configured for insertion into a blood vessel.

[0025] The one or more struts may define a housing 110 having a blood inlet 112 and a blood outlet 113. Blood is configured to enter through the blood inlet, pass through or circulate around the impeller, and exit through the blood outlet. The one or more struts may have an inner surface and an outer surface opposite the inner surface. The inner surface is configured to face toward the central axis 160, and the outer surface is configured to face away from the central axis.

[0026] The blood pump may include an inner coating 118. The inner coating may be a single layer of coating disposed on the inner surface of the struts.

[0027] The inner coating may be any suitable coating material, such as polyurethane. The inner coating may be disposed on the interior surface at the blood inlet and extend axially partially toward the blood outlet a fixed axial distance 140 that is less than the axial length of the housing. That is, the inner coating may not extend the entire axial distance between the blood inlet and the blood outlet.

[0028] The blood pump may include an outflow tube 130 coupled to the outer surface. The outflow tube may externally overlie the blood outlet and overlie at least a first portion of the inner coating. In Figure 2, the outflow tube is shown over a fixed axial distance 140 that defines the axial length of the inner coating, but in other embodiments, the outflow tube does not extend axially to the blood inlet. The outflow tube may extend axially beyond the blood outlet.

[0029] The outflow tube is preferably collapsible. The outflow tube may be made of any suitable biocompatible material, such as a suitable polymer, such as polyurethane, polyamide, nylon, or silicone. In some embodiments, the outflow tube may be polytetrafluoroethylene (PTFE).

[0030] The blood pump may include an impeller 114 disposed within the housing. The impeller may include at least one blade 115. In some embodiments, the impeller preferably includes two blades. In some embodiments, the impeller more preferably includes at least two blades.

[0031] In some embodiments, the leading edge of the impeller and / or at least one blade is offset from the blood inlet by a predetermined distance 141.

[0032] In some embodiments, at least one blade has an axial length 150 of 7.5 mm or less. In some embodiments, the axial length is 7 mm or less. In some embodiments, the axial length is 6.5 mm or less. In some embodiments, the length is at least 3 mm. In some embodiments, the length is at least 4 mm. In some embodiments, the length is at least 3 mm. In some embodiments, the length is at least 5 mm. In some embodiments, the length is at least 3 mm. In some embodiments, the length is at least 6 mm.

[0033] In some embodiments, the axial length of the inner coating (e.g., fixed axial distance 140) may be configured to span a portion of the impeller having an axial length 151 that is 50% or less of the total axial length 152 of the impeller. In some embodiments, the axial length of the inner coating (e.g., fixed axial distance 140) may be configured to span a portion of the impeller having an axial length 151 that is 30% or less of the total axial length 152 of the impeller. In some embodiments, the axial length of the inner coating (e.g., fixed axial distance 140) may be configured to cover a portion of the impeller having an axial length 151 that is 20% or less of the total axial length 152 of the impeller. In some embodiments, the axial length of the portion may be 15% or less of the total axial length of the impeller. In some embodiments, the axial length of the portion may be 10% or less of the total axial length of the impeller.

[0034] In some embodiments, the axial length of the inner coating (e.g., fixed axial distance 140) may be configured to span a portion of at least one blade having an axial length 151 that is 50% or less of the total axial length 152 of the at least one blade. In some embodiments, the axial length of the inner coating (e.g., fixed axial distance 140) may be configured to span a portion of at least one blade having an axial length 151 that is 30% or less of the total axial length 152 of the at least one blade. In some embodiments, the axial length of the portion may be 15% or less of the total axial length 150 of the at least one blade. In some embodiments, the axial length of the portion may be 10% or less of the total axial length 150 of the at least one blade.

[0035] In some embodiments, the inner coating does not cover at least a portion of at least one blade. In some embodiments, the leading edge 116 of at least one blade is not covered by the inner coating. In some embodiments, the inner coating does not cover at least a portion of the impeller. In some embodiments, there is an axial gap (not shown) or axial separation between the trailing edge 143 of the inner coating and the leading edge of at least one blade.

[0036] In some embodiments, the leading edge of the at least one blade may be a fixed distance from the trailing edge of the inner coating. In some embodiments, the trailing edge of the inner coating is axially between the leading edge of the at least one blade and the trailing edge of the at least one blade. In some embodiments, the trailing edge of the inner coating is axially between the leading edge of the inner coating and the leading edge of the at least one blade.

[0037] In some embodiments, the inner coating may have a first end at the blood inlet and a second end axially offset from the first end by a first predetermined distance (D1) (e.g., fixed axial distance 140). In some embodiments, the impeller may have a first end and a second end, and the first end of the impeller may be axially offset from the first end of the inner layer by a second predetermined distance (D2) (e.g., predetermined distance 141). The second end of the impeller may be axially offset from the first end of the inner layer by a third predetermined distance (D3) (e.g., predetermined distance 141 plus the total axial length 152 of the impeller). In various embodiments, D3 may be greater than D2, and either D2≧D1 or D1−D2≦20% of the axial length of the impeller.

[0038] 3A, the impeller is configured to rotate about a central axis 160. In some embodiments, the impeller blade(s) may have a leading edge angle 155 and a trailing edge angle 156 relative to the central axis. The leading edge angle and trailing edge angle are the angles formed by a line perpendicular to the axis at the outer edge of the blade and a line parallel to the surface of the blade at the leading or trailing edge, respectively.

[0039] In some embodiments, the leading edge angle of at least one blade relative to the central axis may be equal to the trailing edge angle of at least one blade relative to the central axis.

[0040] In some embodiments, the leading edge angle of at least one blade relative to the central axis may be different from the trailing edge angle of at least one blade relative to the central axis. In some embodiments, the leading edge angle and / or the trailing edge angle may be between 45 and 60 degrees. In some embodiments, the leading edge angle and / or the trailing edge angle may be between 55 and 60 degrees. In some embodiments, the leading edge angle and / or the trailing edge angle may be between 50 and 55 degrees. In some embodiments, the leading edge angle and / or the trailing edge angle may be between 45 and 50 degrees. The smaller the angle, the higher the blade pitch.

[0041] Referring to FIG. 3B, the impeller can be seen looking downward from the leading edge to the trailing edge of the impeller. A first blade 301 is shown with its leading edge 302 and trailing edge 303. The trailing edge is shown in dashed lines because it is located aft of the leading edge portion of the second blade 304. The wrap angle 305 of the first blade is shown. The wrap angle is the angle of the blade that indicates the amount the blade "wraps" helically around the central axis. Thus, a straight blade positioned parallel to the central axis has a wrap angle of 0°, while a blade that makes one full helical revolution has a wrap angle of 360°. The wrap angle is generally considered to be the angle between (1) an imaginary line from the central axis that passes through the leading edge of the first blade at the point where the leading edge attaches to the central hub 306, and (2) an imaginary line from the central axis that passes through the trailing edge at the point where the trailing edge attaches to the central hub. In some embodiments, the wrap angle of at least one blade relative to the central axis may be at least 100 degrees. In some embodiments, the wrap angle of at least one blade relative to the central axis may be at least 180 degrees. In some embodiments, the wrap angle of at least one blade relative to the central axis may be at least 200 degrees.

[0042] Referring to FIG. 6A, in some embodiments, the blood pump may have an inner coating 18 disposed on the inner surface of the struts 11 and an outflow tube 30 disposed on the outer surface of the struts.

[0043] In some embodiments, the blood pump may include an outer coating, as seen in FIG. 1 . The configurations of the outer coating, inner coating, struts, and outflow tube may vary. In some embodiments, the outer coating may be coupled to the outflow tube in various ways. Referring to FIG. 6B , in some embodiments, the outer coating 19 may be disposed on the outer surface of one or more struts between the strut group and the outflow tube. The outflow tube may be disposed around the outer coating. Referring to FIG. 6C , in some embodiments, the outflow tube and the outer coating are both disposed on the outer surface of the strut group. In some embodiments, the inner surface of the first portion 97 of the outer coating may contact the outer surface of the outflow tube, such as a portion of the outflow tube disposed on the outer surface of the strut group. As will be appreciated, this may be reversed, with a portion of the inner surface of the outflow tube contacting the outer surface of the outer coating. Referring to FIG. 6D , in some embodiments, the end of the outflow tube may be sandwiched between the inner surface of the first portion 97 of the outer coating and the outer surface of the second portion 96. Referring to FIG. 6E , in some embodiments, the trailing edge of the outer coating may abut the leading edge of the outflow tube.

[0044] In some embodiments, the outer coating may be disposed at the blood inlet such that it does not extend axially beyond the trailing edge of the inner coating. In some embodiments, at least a portion of the outer coating may be between one or more struts and the outflow tube. In some embodiments, the blood pump may not have an outer coating disposed on the outer surface of one or more struts.

[0045] 6A, adjacent (axially and circumferentially) strut groups define inter-strut spaces 98 (e.g., the space between the distally facing surface of a first strut and the proximally facing surface of an adjacent strut). Within each such space, the volume of the space may be filled with material forming the inner coating, material forming the outflow tube, and / or material forming the outer coating.

[0046] The outer coating may be any suitable coating material, such as polyurethane or polytetrafluoroethylene (PTFE).

[0047] It is well known that shortening the length of the rotor blades reduces hydraulic output. Referring to Figures 4A and 4B, a comparison is shown between a commercially available blood pump with a relatively long impeller and inner coating and an embodiment of the blood pump of the present invention with a shorter impeller and inner coating, both operating at the same RPM. As can be seen, while hydraulic efficiency is reduced, the disclosed blood pump has remarkably similar flow rates to the commercial pump at higher pressures.

[0048] Referring to FIG. 5, in some embodiments, a system can be provided. The blood pump 100 can be inserted into the patient 400 at an insertion point 420 until the blood pump reaches a desired location. In FIG. 5, the device is shown inserted with the blood inlet 112 located in the left ventricle 412 of the patient's heart 410. Blood flows from the left ventricle through the blood inlet, through the housing 110, and out the outflow tube 130 into the aorta. A controller 450 can be used to control the blood pump. The blood pump can be operably coupled to the controller, for example, via the catheter 120. The blood pump can be detachably coupled to the controller.

[0049] In some embodiments, a kit can be provided that can include a blood pump as disclosed herein and a controller configured to be operably coupled to the blood pump.

[0050] Several embodiments of the present disclosure are described in detail with reference to the drawings, in which like reference numerals identify similar or identical elements. It should be understood that the disclosed embodiments are merely examples of the present disclosure, which can be embodied in various forms. To avoid obscuring the present disclosure in unnecessary detail, well-known functions or structures are not detailed. Therefore, the specific structural and functional details disclosed herein should not be construed as limiting the present invention, but should be construed merely as a basis for the claims and as a representative basis for teaching those skilled in the art how to utilize substantially any appropriately detailed structure in various ways.

[0051] Those skilled in the art will recognize, or be able to ascertain using no more than routine experimentation, many equivalents to the specific embodiments of the invention described herein which equivalents are intended to be encompassed by the following claims.

[0052] Various modifications may be made to the systems, methods, devices, mechanisms, techniques, and portions thereof described herein with respect to the various figures, and such modifications are intended to be within the scope of the present invention. For example, while a particular order of steps or arrangement of functional elements is presented in various embodiments described herein, various other orders / arrangements of steps or functional elements may be used within the scope of various embodiments. Furthermore, while modifications to embodiments may be discussed individually, various embodiments may employ multiple modifications simultaneously or sequentially, or may employ combinations of modifications, etc.

[0053] While various embodiments incorporating the teachings of the present invention have been shown and described in detail herein, those skilled in the art will readily devise many other modified embodiments which also incorporate these teachings. Thus, while the foregoing is directed to various embodiments of the present invention, other and further embodiments of the present invention may be devised without departing from the basic scope thereof. Thus, the appropriate scope of the present invention is to be determined according to the following claims. [Explanation of symbols]

[0054] 1,100 blood pumps 10,110 cabinets 11,111 pillar group 12,112 Blood inlet 13,113 Blood outlet 14,114 impellers 15,115 blades 16,116 leading edge 17,143 trailing edge 18,118 Inner coating 19 Outer Coating 20,120 catheters 30,130 Outflow pipe 40,41 distance 50,152 Impeller overall length 51 Impeller part 60 mesh 61, 111 pillars 96 Second part of outer coating 97 First part of outer coating 98 Space 151 Axial length 152 Total axial length 155 Leading edge angle 156 Trailing edge angle 160 center axis 301,304 Blades 302 leading edge 303 Trailing edge 305 Wrapping angle 306 central hub 400 patients 410 Heart 412 Left ventricle 420 insertion point 450 Controller

Claims

1. one or more struts configured to couple to a catheter, the one or more struts defining a housing having a blood inlet and a blood outlet, the one or more struts having an inner surface and an outer surface facing opposite the inner surface; an inner surface coating disposed on the inner surface at the blood inlet and extending partially axially toward the blood outlet, the inner surface coating defining a smooth inner surface; an outflow tube coupled to the outer surface, the outflow tube overlying the blood outlet and overlying at least a first portion of the inner coating and extending axially beyond the blood outlet; an impeller disposed within the housing and including at least one blade.

2. 2. The blood pump of claim 1, wherein the wrap angle of the at least one blade relative to the central axis is at least 100 degrees.

3. 3. The blood pump of claim 2, wherein the wrap angle is at least 180 degrees.

4. 4. The blood pump of claim 3, wherein the wrap angle is at least 200 degrees.

5. 5. The blood pump of claim 1, wherein a leading edge angle of said at least one blade relative to a central axis is equal to a trailing edge angle of said at least one blade relative to said central axis.

6. 6. The blood pump of claim 5, wherein the leading edge angle and the trailing edge angle are between 55 and 60 degrees.

7. 7. The blood pump of claim 1, wherein the at least one blade has an axial length of 7.5 mm or less.

8. 8. The blood pump of claim 7, wherein the at least one blade has an axial length of 7 mm or less.

9. 9. The blood pump of claim 8, wherein the axial length of at least one blade is 6.5 mm or less.

10. 10. The blood pump of claim 1, further comprising an outer coating disposed on an outer surface of the one or more struts and coupled to the outflow tube, the outer coating disposed at the blood inlet and extending without exceeding a trailing edge of the inner coating.

11. 10. The blood pump of claim 1, wherein the blood pump does not have an outer coating disposed on the outer surface of the one or more struts.

12. 12. The blood pump of claim 1, wherein the axial length of the inner coating corresponds to the length of at least one blade, the axial length being no more than 50% of the total length of the at least one blade.

13. 13. The blood pump of claim 12, wherein the axial length is no more than 30% of the overall length of the at least one blade.

14. 14. The blood pump of claim 13, wherein the axial length is no more than 20% of the overall length of the at least one blade.

15. 15. The blood pump of claim 1, wherein the axial length of the inner coating corresponds to the length of the impeller, the axial length being 50% or less of the total length of the impeller.

16. 16. The blood pump of claim 15, wherein the axial length is 30% or less of the overall length of the impeller.

17. 17. The blood pump of claim 16, wherein the axial length is no more than 20% of the overall length of the impeller.

18. 18. The blood pump according to claim 15, wherein the length of the impeller covered by the inner coating is 15% or less of the total length of the impeller.

19. 19. The blood pump of claim 18, wherein the length of the impeller covered by the inner coating is 10% or less of the total length of the impeller.

20. 20. The blood pump of claim 1, wherein a leading edge of the at least one blade is not covered by the inner coating and is configured to be positioned a fixed distance from a trailing edge of the inner coating.

21. 21. The blood pump of any one of claims 1 to 20, wherein the one or more struts comprise nitinol.

22. A blood pump according to any preceding claim, wherein the inner coating is polyurethane.

23. The blood pump of any one of claims 1 to 22, wherein the at least one blade comprises at least two blades.

24. 24. The blood pump of any one of claims 1 to 23, wherein the at least one blade comprises two blades.

25. one or more struts coupled to the catheter, the one or more struts defining a housing having a blood inlet and a blood outlet, the one or more struts having an inner surface and an outer surface opposite the inner surface; an inner coating disposed on the inner surface at the blood inlet and extending partially axially toward the blood outlet; an outflow tube coupled to the outer surface, the outflow tube overlying the blood outlet and overlying at least a first portion of the inner coating and extending axially beyond the blood outlet; an impeller disposed within the housing and including at least one blade.

26. a pump housing coupled to a catheter configured for insertion into a blood vessel, the pump housing including an inner layer disposed on an inner surface of an expandable mesh layer defining a blood inlet and a blood outlet, the inner layer having a first end at the blood inlet and a second end axially offset a first predetermined distance (D1) from the first end; a blood pump including an impeller disposed within the pump housing, the impeller including at least one blade and having a first end and a second end, the first end of the impeller being axially offset from the first end of the inner layer by a second predetermined distance (D2), and the second end of the impeller being axially offset from the first end of the inner layer by a third predetermined distance (D3); A blood pump in which D3>D2 and D2≧D1 or D1−D2≦50% of the axial length of the impeller.

27. 27. The blood pump according to claim 26, wherein D1-D2≦30% of the axial length of the impeller.

28. 28. The blood pump according to claim 27, wherein D1-D2≦20% of the axial length of the impeller.

29. A blood pump according to any one of claims 1 to 28; a controller operably coupled to the blood pump.

30. A blood pump according to any one of claims 1 to 28; a controller configured to be operably coupled to the blood pump.

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