IMPELLER FOR AXIAL FLOW PUMP

• US 20150051438A1
• Filed: 08/14/2014
• Published: 02/19/2015
• Est. Priority Date: 08/14/2013
• Status: Active Grant

• Current Assignee: Heartware,Inc. (Medtronic Plc)
• Original Assignee: Heartware,Inc. (Medtronic Plc)
• Inventors: Taskin, Mustafa Ertan
• Granted Patent: US 9,561,313 B2
• Time in Patent Office: Days
• US Class Current: 600/16
• CPC Class Codes: A61M 60/148 in line with a blood vessel using resection or like techniques, e.g. permanent endovascular heart assist devices
• CPC Class Codes: A61M 60/178 drawing blood from a ventricle and returning the blood to the arterial system via a cannula external to the ventricle, e.g. left or right ventricular assist devices
• CPC Class Codes: A61M 60/237 the blood flow through the rotating member having mainly axial components, e.g. axial flow pumps
• CPC Class Codes: A61M 60/419 the force acting on the blood contacting member being permanent magnetic, e.g. from a rotating magnetic coupling between driving and driven magnets
• CPC Class Codes: A61M 60/422 the force acting on the blood contacting member being electromagnetic, e.g. using canned motor pumps
• CPC Class Codes: A61M 60/806 Vanes or blades
• CPC Class Codes: A61M 60/824 Hydrodynamic or fluid film bearings
• CPC Class Codes: F04D 29/0413 hydrostatic; hydrodynamic thrust bearings
• CPC Class Codes: F04D 29/181 Axial flow rotors F04D29/185 take precedence

Abstract

A rotor for an axial-flow blood pump has blades projecting outwardly from a hub and channels between the blades. The blades incorporate hydrodynamic bearing surfaces capable of suspending the rotor during operation. The rotor has a configuration which provides superior pumping action and reduced shear of blood passing through the pump. The forwardly facing pressure surfaces of the blades may include outflow corner surface at their downstream ends. The outflow corner surfaces desirably slope rearwardly and intersect the rearwardly-facing suction surfaces of the blades at outflow ends of the blades.

Claims

1. A rotor for an axial flow blood pump, the rotor having an axis extending in upstream and downstream axial directions and a plurality of generally helical blades extending from an inflow end of the rotor to an outflow end of the rotor, the blades projecting outwardly away from the axis in a spanwise direction, the blades being coextensive in the axial directions and spaced apart from one another in a circumferential direction around the axis so as to define generally helical channels between adjacent ones of the blades, each said blade having a pressure surface facing in a forward circumferential direction, a suction surface facing in a rearward circumferential direction and a tip surface extending between the pressure and suction surfaces of the blade, each said channel being bounded by the pressure side of one of said blades and the suction side of a next adjacent one of said blades, the tip surfaces of the blades defining hydrodynamic bearing regions capable of suspending the rotor, wherein the rotor is adapted to provide at least one of:

(a) at least 5 liters of blood flow at 75 mm Hg pressure head with a V₁₅₀ less than 25 mm³; and

(b) a specific blood flow rate of at least 50,000 mm/min at 75 mm Hg pressure head and a rotational speed of 15,000 revolutions per minute; and

(c) an average outflow angle less than 30 degrees.

2. A rotor as claimed in claim 1 having an average inflow angle less than 30 degrees.

3. A rotor as claimed in claim 1 wherein the rotor is adapted to provide 5 liters of blood flow at 75 mm Hg pressure head with a V₁₅₀ less than 25 mm³.

4. A rotor as claimed in claim 1 having a maximum diameter across the tip surfaces of the blades less than 13 mm.

5. A rotor as claimed in claim 4 having a maximum diameter across the tip surfaces of the blades less than 10 mm.

6. A rotor as claimed in claim 1 wherein the tip surfaces of the blades and the channels have width dimensions in the circumferential direction, the aggregate width dimensions of the tip surfaces being greater than the aggregate width dimensions of the channels over at least a major portion of the axial extent of the blades and channels.

7. A rotor as claimed in claim 1 wherein the channels provide a specific outflow area of at least 0.47 and a specific inflow area of at least 0.44.

29. A blood pump comprising a rotor as claimed claim 1 or claim 8 and a housing defining a bore with an interior surface in the form of a surface of revolution, the rotor being disposed within the housing with the axis of the rotor coaxial with the interior surface of the bore and with the interior surface of the bore closely overlying the tip surfaces of the blades, the pump further comprising a drive arranged to rotate the rotor about the axis.

30. A blood pump as claimed in claim 29 wherein, in operation, the rotor is suspended within the bore and maintained out of contact with the interior surface of the housing by operation of the hydrodynamic bearing surfaces.

31. A blood pump as claimed in claim 30 wherein the rotor includes a plurality of magnetic poles and the drive includes a plurality of coils spaced apart from one another around the circumference of the bore and an electrical circuit arranged to energize the coils so as to produce a rotating magnetic field within the bore.

32. A blood pump as claimed in claim 31 having a power-to-flow ratio of less than 1.05 watts per liter per minute at a pressure head of 75 mm Hg.

33. A method of pumping blood comprising the steps of implanting a blood pump as claimed claim 29 within the body of a patient, connecting the pump to the circulatory system of the patient, and actuating the pump to assist blood flow within the circulatory system.

34. A method as claimed in claim 33 wherein the step of connecting the blood pump is performed so as to place an inlet of the pump in communication with a ventricle of the patient'"'"'s heart and place an outlet of the pump in communication with an artery of the patient.

8. A rotor for an axial flow blood pump, the rotor having an axis extending in upstream and downstream axial directions and a plurality of generally helical blades extending from an inflow end of the rotor to an outflow end of the rotor, the blades projecting outwardly away from the axis in a spanwise direction, the blades being coextensive in the axial directions and spaced apart from one another in a circumferential direction around the axis so as to define generally helical channels between adjacent ones of the blades, each said blade having a pressure surface facing in a forward circumferential direction, a suction surface facing in a rearward circumferential direction and a tip surface extending between the pressure and suction surfaces of the blade, each said channel being bounded by the pressure side of one of said blades and the suction side of a next adjacent one of said blades, the tip surfaces of the blades defining hydrodynamic bearing surfaces capable of suspending the rotor, wherein the pressure surface of each said blade includes an outflow corner surface at the outflow end of the blade, the outflow corner surface extending over a major portion of the spanwise extent of the blade, the outflow corner surface sloping rearwardly in the downstream axial direction and extending to within 0.4 mm of the suction surface of the blade at a downstream extremity of the blade adjacent the tip surface of the blade.

9. A rotor as claimed in claim 8 wherein each said outflow corner surface extends to within 0.15 mm of the suction surface of the blade over at least a major portion of the spanwise extent of the blade.

10. A rotor as claimed in claim 8 wherein each said outflow corner surface defines an outer edge at the tip surface of a blade and an inner edge extending along an inner curve at an inner end of the outflow corner surface, the inner curve sloping rearwardly in the downstream axial direction, the inner curve diverging in the forward circumferential direction from the outer curve.

11. A rotor as claimed in claim 8 wherein, over at least a major portion of the outflow corner surface, a vector normal to the outflow corner surface has positive, non-zero components in the outward direction and in the downstream axial direction.

12. A rotor as claimed in claim 8 wherein the rotor includes a central hub, the blades projecting outwardly from the body and the body defining outwardly-facing floor surfaces, each such floor surface bounding one said channel, the rotor further comprising outflow scoop fillets adjacent the outflow end of the rotor, each said outflow scoop fillet joining the suction surface of one said blade and the floor surface of the channel bounded by such suction surface, the fillet having a radius which increases progressively in the downstream direction.

13. A rotor as claimed in claim 12 wherein the radius of each said outflow scoop fillet at the outflow end of the rotor is at least about 25% of the spanwise extent of each said channel.

14. A rotor as claimed in claim 12 or claim 13 wherein the suction surface of each said blade has a pitch angle of less than 10 degrees in a region adjacent the outflow end of the rotor where the outflow scoop fillet is provided.

15. A rotor as claimed in claim 12 or claim 13 or claim 14 wherein the hub has a diameter which increases progressively in the downstream direction over at least a portion of the axial extent of the channels, whereby the floor surfaces of the channels slope outwardly in the downstream direction over at least such portion of the axial extent.

16. A rotor as claimed in claim 8 wherein, in each said blade, the suction surface includes an inflow end region at the inflow end of the blade, the inflow end region having a pitch angle of less than 90 degrees over its entire extent, the inflow end region extending to within 1 mm of the pressure surface of the blade at and adjacent the tip surface of the blade.

17. A rotor as claimed in claim 16 wherein the inflow end region of each said blade extends to within 1 mm of the pressure surface over at least the major portion of the span of the blade.

18. A rotor as claimed in claim 17 wherein suction surface of each blade includes a middle region remote from the inflow and outflow ends of the blade, the suction surface having a first pitch angle in the middle region, the inflow end region of the suction surface having a pitch angle greater than the first pitch angle.

19. A rotor as claimed in claim 17 wherein the pitch angle of the inflow end region of each said blade increases progressively toward the upstream extremity of the blade.

20. A rotor as claimed in claim 16 wherein, at each axial location within the axial extent of the inflow end regions, the pitch angles of the inflow end regions are greater than the pitch angles of the pressure surfaces of the blades, whereby the inflow end region of the suction surface bounding each said channel diverges from the pressure surface bounding that channel and each said channel widens circumferentially in the upstream direction.

21. A rotor as claimed in claim 8 wherein the blades have inflow edges at the inflow end, and wherein the inflow edges of the blades slope in the downstream axial direction over a major portion of the span of the blades.

22. A rotor as claimed in claim 8 wherein the tip surfaces of the blades have an aggregate area of at least 50% of the area of a theoretical solid surface of revolution about the axis having radius at each location along the axis corresponding to the maximum radius of the blades at the same location along the axis.

23. A rotor as claimed in claim 22 wherein the tip surface of each said blade includes a surface of revolution about the axis and one or more of said hydrodynamic bearing surfaces, each said hydrodynamic bearing surface having a leading edge at the pressure surface of the blade, each said leading edge being recessed inwardly from the surface of revolution, and each said hydrodynamic bearing surface sloping outwardly in a rearward circumferential direction away from the leading edge.

24. A rotor as claimed in claim 23 wherein the leading edge of each said hydrodynamic bearing surface is recessed radially inwardly from the surface of revolution by 0.076 to 0.010 mm.

25. A rotor as claimed in claim 23 wherein the hydrodynamic bearing surfaces of each blade include a front hydrodynamic bearing surface adjacent the inflow end of the rotor and a rear hydrodynamic bearing surface adjacent the outflow end of the rotor, the front and rear hydrodynamic bearing surfaces being separated from one another by an intermediate wall defining a portion of the surface of revolution.

26. A rotor as claimed in claim 25 wherein a ratio of the area of the front hydrodynamic bearing surface to the area of the rear hydrodynamic bearing surface is less than 1.13.

27. A rotor as claimed in claim 26 wherein said ratio is 1.10.

28. A rotor as claimed claim 8 wherein each said blade has a constant span over at least the majority of its axial extent.