Flexible catheter with a drive shaft
A blood pump assembly comprising a pump casing, at least a portion of which is disposed around one or more blades coupled to a drive cable, and a motor configured to drive the drive cable and the one or more blades rotationally, wherein the drive cable is configured to undergo axial displacement with respect to the pump casing during rotation.
1. A blood pump assembly, comprising:
a pump casing configured to be placed inside a left ventricle of a patient, at least a portion of the pump casing being disposed around one or more blades, the one or more blades being coupled to a drive cable; and
a motor configured to drive the drive cable and the one or more blades rotationally to pump blood from the left ventricle to an aorta of the patient, and wherein the drive cable and the one or more blades are configured to undergo axial displacement with respect to the pump casing while being driven rotationally by the motor to pump blood through the pump casing, the axial displacement being along a longitudinal axis of the drive cable.
2. The blood pump assembly of claim 1 , further comprising:
a first bearing element proximal of the one or more blades;
a second bearing element proximal of the one or more blades, and configured to allow the drive cable to move with respect to the second bearing element; and
a third bearing element distal of the one or more blades, and configured to allow the drive cable to move with respect to the third bearing element,
wherein the drive cable passes through the first bearing element, the second bearing element, and the third bearing element, and
wherein the drive cable is coupled to the first bearing element such that the first bearing element is held in an axially-fixed position with respect to the drive cable, but such that the first bearing element is not held in an axially-fixed position with respect to the second bearing element.
3. The blood pump assembly of claim 1 , further comprising:
a first bearing element proximal of the one or more blades;
a second bearing element proximal of the one or more blades, and configured to allow the drive cable to move with respect to the second bearing element; and
a third bearing element distal of the one or more blades, and configured to allow the drive cable to move with respect to the third bearing element,
wherein the drive cable passes through the first bearing element, the second bearing element, and the third bearing element, and
wherein the one or more blades are coupled to the drive cable such that rotation of the one or more blades causes the drive cable to undergo axial displacement with respect to the second bearing element and the third bearing element.
4. The blood pump assembly of claim 1 , wherein the motor is configured to drive the drive cable in a given direction of rotation, and
wherein the drive cable comprises a plurality of wires wound around a longitudinal axis of the drive cable in a first direction such that, in response to the drive cable rotating in the given direction of rotation, at least portion of the drive cable shortens axially.
5. The blood pump assembly of claim 4 , wherein the drive cable comprises a plurality of wires wound around a longitudinal axis of the drive cable in a second direction such that, in response to the drive cable rotating in the given direction of rotation, at least a portion of the drive cable lengthens axially.
6. The blood pump assembly of claim 1 , further comprising:
a flexible catheter comprising:
a sleeve surrounding the drive cable; and
a sheath surrounding the drive cable and the sleeve,
wherein the drive cable, the sleeve and the sheath are configured to be flexible,
wherein the drive cable, at a proximal end of the drive cable, has a coupling element for connecting the drive cable with the motor, and
wherein the drive cable is comprised at least partially of an alloy which comprises at least 10% by weight of chromium, nickel and cobalt.
7. The blood pump assembly of claim 6 , wherein the alloy comprises at least one of:
(i) 30%-40% by weight nickel,
(ii) 30%-40% by weight cobalt, or
(iii) 15%-25% by weight chromium.
8. The blood pump assembly of claim 6 , wherein the alloy has a tensile strength between 1800 N/mm 2 and 2400 N/mm 2 .
9. The blood pump assembly of claim 8 , wherein the sleeve is at least partially made from the alloy that has the tensile strength between 1800 N/mm 2 and 2400 N/mm 2 .
10. The blood pump assembly of claim 6 , wherein the sleeve is at least partially made of a same material as the drive cable.
11. The blood pump assembly of claim 6 , wherein the sleeve is configured as a bearing coil with one or more windings, wherein each winding rotates helically around a longitudinal axis of the drive cable.
12. The blood pump assembly of claim 11 , wherein the bearing coil comprises a wound ribbon which rotates helically around a longitudinal axis of the drive cable.
13. The blood pump assembly of claim 12 , wherein an axially measured width of the ribbon lies in a range of 0.36 mm to 0.84 mm, and a radially measured thickness the ribbon lies in a range of 0.06 mm to 0.14 mm.
14. The blood pump assembly of claim 12 , wherein ribbon has an axial tilting of less than 5° relative to a longitudinal axis of the drive cable when the drive cable is held in a straight condition without curvature.
15. The blood pump assembly of claim 12 , wherein lateral edges of the ribbon are rounded.
16. The blood pump assembly of claim 15 , wherein the lateral edges of the ribbon have a curvature radius of 0.04 mm or more.
17. The blood pump assembly of claim 11 , wherein at least one of the one or more windings of the bearing coil has a pitch in a range of 0.43 to 0.98.
18. The blood pump assembly of claim 6 , wherein an inner diameter of the sleeve lies in a range between 0.6 mm and 1.4 mm and an outer diameter of the sleeve lies in a range of 0.72 mm to 1.68 mm.
19. The blood pump assembly of claim 1 , wherein a surface of the drive cable has a roughness RZ between 0.01 microns and 1 micron.
20. The blood pump assembly of claim 1 , further comprising:
a coupling between a proximal end of the drive cable and the motor, the coupling configured to allow axial displacement between the proximal end of the drive cable and the motor while still enabling the motor to drive the drive cable rotationally.