Impeller housing
Apparatus and methods are described including a ventricular assist device that includes a frame having struts that define a plurality of cells. In its non-radially-constrained configuration, the frame includes a generally cylindrical portion. A tube defines blood outlet openings, and a portion of the tube is disposed outside the frame and is coupled to the generally cylindrical portion of the frame, such that the portion of the tube conforms with a structure of struts of the frame. An inner lining is coupled to an inside of the generally cylindrical portion of the frame, such as to provide the generally cylindrical portion of the frame with a smooth inner surface. An impeller is disposed at least partially inside the generally cylindrical portion of the frame and is configured to pump blood through the tube and out of the one of more blood outlet openings. Other applications are also described.
1. An apparatus, comprising:
a ventricular assist device comprising:
a frame comprising struts that define a plurality of cells, the frame being configured such that, in a non-radially-constrained configuration of the frame, the frame comprises a generally cylindrical portion;
a tube that defines one or more blood outlet openings, a portion of the tube being disposed outside the frame and coupled to the generally cylindrical portion of the frame, such that the portion of the tube conforms with a structure of struts of the frame;
an inner lining coupled to an inside of the generally cylindrical portion of the frame, such as to provide the generally cylindrical portion of the frame with a smooth inner surface;
an impeller disposed at least partially inside the generally cylindrical portion of the frame and configured to pump blood through the tube and out of the one of more blood outlet openings.
2. The apparatus according to claim 1 , wherein the inner lining is configured to be coupled to the inside of the generally cylindrical portion of the frame, such that it provides a generally circular inner cross-section to the generally cylindrical portion of the frame.
3. The apparatus according to claim 1 , wherein the impeller is disposed within the frame such that a location along the impeller that defines a maximum span of the impeller is disposed within the generally cylindrical portion of frame throughout operation of the impeller.
4. The apparatus according to claim 1 , wherein the inner lining is configured to reduce hemolysis caused by pumping of blood by the impeller, by providing the generally cylindrical portion of the frame with the smooth inner surface.
5. The apparatus according to claim 1 , wherein the frame is shaped to define a widened inlet to the tube.
6. The apparatus according to claim 1 , wherein the frame is shaped to define a narrowing in a vicinity of a location within the frame that is configured to house the impeller.
7. The apparatus according to claim 1 , wherein the inner lining and the tube are made from different materials from each other, and a thermoforming temperature of a material from which the inner lining is made is higher than a thermoforming temperature of a material from which the tube is made.
8. The apparatus according to claim 1 , wherein the portion of the tube that is coupled to the generally cylindrical portion of the frame is disposed around the entire generally cylindrical portion of the frame, such the portion of the tube overlaps with the entire inner lining.
9. The apparatus according to claim 1 , wherein the portion of the tube that coupled to the generally cylindrical portion of the frame is disposed around only a portion of the generally cylindrical portion of the frame, such the portion of the tube does not overlap with the entire inner lining.
10. The apparatus according to claim 9 , wherein the portion of the tube that is coupled to the generally cylindrical portion of the frame is configured to prevent radial expansion of a portion of the generally cylindrical portion of the frame to which the portion of the tube is coupled, thereby causing the portion of the generally cylindrical portion of the frame to which the portion of the tube is coupled to be narrower than a portion of the generally cylindrical portion of the frame to which the portion of the tube is not coupled.
11. The apparatus according to claim 1 , wherein, in the non-radially-constrained configuration of the frame, a width of each of each of the cells within the generally cylindrical portion as measured around a circumference of the generally cylindrical portion is less than 2 mm.
12. The apparatus according to claim 11 , wherein, in the non-radially-constrained configuration of the frame, the width of each of the cells within the generally cylindrical portion as measured around the circumference of the generally cylindrical portion is between 1.4 mm and 1.6 mm.
13. The apparatus according to claim 11 , wherein, in the non-radially-constrained configuration of the frame, the width of each of the cells within the generally cylindrical portion as measured around the circumference of the generally cylindrical portion is between 1.6 mm and 1.8 mm.
14. The apparatus according to claim 1 , wherein the impeller is stabilized with respect to the frame such that a gap is maintained between an outer edge of the impeller and the inner lining throughout operation of the impeller.
15. The apparatus according to claim 14 , wherein the impeller is stabilized with respect to the frame such that a gap of less than 1 mm is maintained between an outer edge of the impeller and the inner lining throughout operation of the impeller.
16. The apparatus according to claim 15 , wherein the impeller is stabilized with respect to the frame such that a gap of less than 0.4 mm is maintained between an outer edge of the impeller and the inner lining throughout operation of the impeller.
17. The apparatus according to claim 14 , wherein:
the left-ventricular assist device further comprises an axial shaft and proximal and distal radial bearings disposed, respectively, at proximal and distal ends of the frame, the axial shaft passing through the proximal and distal radial bearings;
the impeller is coupled to the axial shaft; and
the impeller is stabilized with respect to the frame by the impeller being held in a radially-fixed position with respect to the axial shaft and the axial shaft being rigid.
18. The apparatus according to claim 17 , wherein the impeller comprises bushings that are disposed around the axial shaft, and at least one of the bushings is configured to be slidable with respect to the axial shaft, wherein the impeller is stabilized with respect to the frame by a region along the axial shaft over which the at least one bushing is configured to be slidable with respect to the axial shaft being coated with a coating, such as to substantially prevent the impeller from vibrating by the coating reducing a gap between the at least one bushing and the axial shaft.
19. The apparatus according to claim 18 , wherein:
the left-ventricular assist device further comprises an axial shaft and proximal and distal radial bearings disposed, respectively, at proximal and distal ends of the frame, the axial shaft passing through the proximal and distal radial bearings;
the impeller is coupled to the axial shaft; and
the impeller is stabilized with respect to the frame by a ratio of a length of the generally cylindrical portion of the frame to a total length of the frame being more than 1:2, such as to substantially prevent vibration of the frame with respect to the axial shaft.