Centrifugal and mixed-flow impellers for use with a blood pump
Apparatus and methods are described including a left-ventricular assist device ( 20 ) that includes a pump-outlet tube ( 28 ). A mixed-flow impeller ( 100 ) is configured to pump blood from a subjects left ventricle to the subjects aorta, by pumping the blood into the pump-outlet tube ( 28 ) via one or more blood inlet openings ( 108 ) disposed within the left ventricle, and by pumping blood out of the pump-outlet tube ( 28 ) via one or more blood outlet openings ( 30 ) disposed within the aorta. The mixed-flow impeller ( 100 ) includes an expandable portion ( 116 ) disposed along its axis and shaped such that a diameter of the expandable portion increases from a distal end of the expandable portion to its proximal end. The mixed-flow impeller ( 100 ) is configured to impart radial flow components to blood as the blood flows from its distal end to its proximal end. Other applications are also described.
1 . An apparatus, comprising:
a left-ventricular assist device configured to assist left-ventricular functioning of a subject, the left-ventricular assist device including:
a pump-outlet tube configured such that a proximal portion of the pump-outlet tube traverses an aortic valve of the subject, and a distal portion of the pump-outlet tube is disposed within a left ventricle of the subject, the pump-outlet tube defining at least one blood inlet opening that is configured to be disposed within the left ventricle and at least one blood outlet opening that is configured to be disposed within an aorta of the subject;
a mixed-flow impeller disposed in the pump-outlet tube and configured to pump blood through the pump-outlet tube from the subject's left ventricle to the subject's aorta, the mixed-flow impeller comprising:
a central axial spring,
one or more impeller blades defined by elongate elements which wind around the central axial spring and a film of material supported between the central axial spring and the elongate elements, and
an inflatable portion disposed along an axis of the impeller and between the edges of the impeller blades and the central axial spring, the inflatable portion being shaped such that, in an expanded configuration of the inflatable portion, a diameter of the inflatable portion increases from a distal end of the inflatable portion to a proximal end of the inflatable portion,
the mixed-flow impeller thereby being configured to impart radial flow components to blood as the blood flows from the distal end to the proximal end of the mixed-flow impeller.
2 . The apparatus according to claim 1 , wherein the pump-outlet tube defines a widened region in the vicinity of the impeller, which is wider than a portion of the pump-outlet tube proximal thereto, and wherein the pump-outlet tube is configured to redirect the radial blood flow components axially, by the pump-outlet tube narrowing within the portion of the pump-outlet tube that is proximal to the widened portion.
3 . The apparatus according to claim 1 , wherein, in the inflated configuration, the inflatable portion of the impeller has a three-dimensional teardrop shape.
4 . The apparatus according to claim 1 , wherein the inflatable portion of the impeller comprises a shape memory alloy that is shape set such that the inflatable portion of the impeller is self inflatable.
5 . The apparatus according to claim 1 , further comprising an expandable flow rectifier that is configured to reduce radial flow components from blood flow through the pump-outlet tube prior to the blood flowing from the at least one blood outlet opening, the expandable flow rectifier being disposed along an axis of the pump-outlet tube and, in the expanded configuration of the flow rectifier, being shaped such that a diameter of the flow rectifier decreases from a distal end of the expandable flow rectifier to a proximal end of the expandable flow rectifier.
6 . The apparatus according to claim 1 , wherein the left-ventricular assist device is configured for use with a purging fluid, wherein the left-ventricular assist device comprises a purging system configured to purge portions of the left-ventricular assist device by pumping the purging fluid through the left-ventricular assist device, and wherein the inflatable portion of the impeller is configured to be inflated with the purging fluid.
7 . The apparatus according to claim 6 , wherein the purging system is configured to control the inflation of the inflatable portion of the impeller, by modulating the pressure at which the purging fluid is pumped into the ventricular assist device.
8 . The apparatus according to claim 1 , wherein the one or more impeller blades are shaped to transition from being spiral shaped within a distal portion of the impeller to being substantially radially-extending within a proximal portion of the impeller.
9 . The apparatus according to claim 8 , wherein the distal portion of the impeller is configured primarily to impart axial flow to blood that is pumped by the distal portion of the impeller, and the proximal portion of the impeller is configured to impart substantial radial flow to blood that is pumped by the proximal portion of the impeller.
10 . The apparatus according to claim 1 , further comprising one or more spiral flow rectifiers disposed within the pump-outlet tube, proximally with respect to the impeller, the spiral flow rectifiers being configured to reduce radial flow components from blood flow by converting radial flow components to axial flow prior to the blood flowing out of the at least one blood outlet opening.
11 . The apparatus according to claim 10 , wherein the one or more spiral flow rectifiers have spiral shapes with a pitch of the spiral shapes increasing from the distal ends of the flow rectifiers to their proximal ends, such that the spiral flow rectifiers are configured to gradually covert radial flow to axial flow.