Heart assist device with expandable impeller pump
View Patent ↗An impeller includes a hub and a blade supported by the hub. The impeller has a stored configuration in which the blade is compressed so that its distal end moves towards the hub, and a deployed configuration in which the blade extends away from the hub. The impeller may be part of a pump for pumping fluids, such as blood, and may include a cannula having a proximal portion with a fixed diameter, and a distal portion with an expandable diameter. The impeller may reside in the expandable portion of the cannula. The cannula may have a compressed diameter which allows it to be inserted percutaneously into a patient. Once at a desired location, the expandable portion of the cannula may be expanded and the impeller expanded to the deployed configuration. A flexible drive shaft may extend through the cannula for rotationally driving the impeller within the patient.
1. A catheter pump comprising:
a cannula having an inlet and an outlet;
an impeller disposed in the cannula, the impeller comprising a hub and a plurality of blades positioned along the hub that define a first diameter of the impeller in a stored configuration and further define a second diameter of the impeller in a deployed configuration, wherein the first diameter is at most half the second diameter; and
a stator disposed downstream of the impeller in the cannula between the impeller and the outlet, the stator comprising a blade configured to reduce swirl velocity from discharge flow from the impeller.
2. The catheter pump of claim 1 , wherein the impeller comprises at least one long helical blade exhibiting a significant degree of wrap around the hub.
3. The catheter pump of claim 2 , wherein the plurality of blades of the impeller comprises a plurality of divisions of the at least one long helical blade into blade rows, wherein individual blades of the blade rows have a height-to-chord length ratio of about 0.5 to 1.5.
4. The catheter pump of claim 3 , wherein the individual blades of the blade rows have a camber of no more than 10 percent.
5. The catheter pump of claim 4 , wherein the forward lean is in a range of about 30 degrees to 60 degrees, inclusively.
6. The catheter pump of claim 3 , wherein the individual blades of the blade rows have a wrap angle, from a leading edge to a trailing edge, of no more than 30 degrees around the hub.
7. The catheter pump of claim 2 , wherein the at least one long helical blade has a camber of at least 15 percent along its root.
8. The catheter pump of claim 1 , wherein each blade of the plurality of blades of the impeller exhibits a forward lean toward a respective pressure face of the blade.
9. The catheter pump of claim 1 , wherein the plurality of blades of the impeller comprise a material having a flexural modulus of about 1,000 pounds per square inch (PSI) in the stored configuration, and having a flexural modulus of about 10,000 PSI in the deployed configuration.
10. The catheter pump of claim 1 , wherein each blade of the plurality of blades of the impeller comprises a tip having a tip pitch angle measured relative to a circumferential plane, and a root, where the blade joins the hub, having a root pitch angle measured relative to the circumferential plane, wherein the tip pitch angle is less than the root pitch angle.
11. The catheter pump of claim 10 , wherein the tip pitch angle is in a range of about 15 degrees to 30 degrees, inclusively.
12. The catheter pump of claim 1 , wherein each blade of the plurality of blades of the impeller comprises a rigid portion and a flexible portion, wherein deformation of the flexible portion enables folding of the blade toward the hub and into the stored configuration.
13. The catheter pump of claim 12 , wherein the flexible portion comprises a hinge.
14. The catheter pump of claim 12 , wherein the rigid portion comprises a first material and the flexible portion comprises a second material more deformable than the first.
15. The catheter pump of claim 1 , wherein each blade of the plurality of blades of the impeller comprises a material having a linear flexural modulus under operational stresses in the deployed configuration, and having a non-linear flexural modulus under stresses exhibited during transition from the deployed configuration to the stored configuration.
16. The catheter pump of claim 15 , wherein the plurality of blades of the impeller comprise a polyurethane polymer having a flexural modulus between about 3,000 pounds per square inch (PSI) and 30,000 PSI, inclusively.
17. The catheter pump of claim 1 , wherein at least one blade of the plurality of blades of the impeller comprises a winglet extending proximally away from a pressure face of the at least one blade.
18. The catheter pump of claim 1 , wherein at least one blade of the plurality of blades of the impeller comprises a winglet extending distally away from a suction face of the at least one blade.
19. The catheter pump of claim 18 , wherein the winglet defines a tip gap, between the at least one blade and an inner wall of the cannula, of about 0.25 to 0.30 times a maximum thickness of a distal end of the at least one blade when in the deployed configuration.
20. The catheter pump of claim 1 , wherein at least one blade of the plurality of blades of the impeller comprises a rounded blade tip defining a tip gap, between the at least one blade and an inner wall of the cannula, of about 0.10 to 0.15 times a maximum thickness of a distal end of the at least one blade when in the deployed configuration.