Patent Description:
Implantable blood pumps are commonly used to assist the pumping action of a failing heart. Typically, the implantable blood pump is surgically implanted in the patient's body and includes a housing with an inlet and an outlet and has a rotor mounted within the housing. The inlet of the housing is connected to a chamber of the patient's heart, typically the left ventricle, whereas the outlet is connected to an artery such as the aorta. Rotation of the pump's rotor drives the blood from the inlet towards the outlet and thus assists flow from the chamber of the heart into the artery.

Some implantable blood pumps are provided with contactless bearings so that, in operation, the rotor floats within the housing. With contactless bearings, there is no solid-to-solid contact between the rotor and the housing and thus no mechanical wear during operation. One form of contactless bearing is a hydrodynamic bearing. In a hydrodynamic bearing, the liquid being pumped passes between a surface of the rotor and a surface of the clearance between the surfaces of a hydrodynamic bearing is many times larger than the dimensions of blood cells. However, in some cases the blood passing through the pump may contain particles of thrombus, a solid or semi-solid deposit generated within the patient's body. The thrombus can lodge on a surface of the hydrodynamic bearing and impede its operation. The surfaces are configured so that as the rotor turns, the fluid disposed between these surfaces exerts pressure on the surface of the rotor that holds the rotor away from the housing. Exemplary blood pumps are disclosed in <CIT> and <CIT>.

The techniques of this disclosure generally relate to an implantable centrifugal blood pump having a non-uniform thrust bearing gap.

In one aspect, the present disclosure provides for a blood pump having a housing including an inlet element. The inlet element has a proximal portion sized to be received within at least a portion of a heart of a patient and defines a major longitudinal axis. A rotor is configured to rotate within the housing about the major longitudinal axis and impel blood from heart. At least one stator is disposed within the housing and positioned within the housing at least one from the group consisting of upstream and downstream from the rotor. During operation of the blood pump the rotor is maintained at an oblique angle with respect to the major longitudinal axis.

In another aspect, the oblique angle is between <NUM>-<NUM> degrees from a longitudinal axis transverse to the major longitudinal axis.

In another aspect, the at least one stator includes a first stator downstream from the rotor and a second stator upstream from the rotor.

In another aspect, a first non-ferromagnetic disk is disposed between the first stator and the rotor and a second non-ferromagnetic disk is disposed between the second stator and the rotor.

In another aspect, the first stator includes a first back iron and the second stator includes a second back iron, and wherein at least one from the group consisting of the first back iron and the second back iron is disposed at an oblique angle with respect to the respective one of the first non-ferromagnetic disk and the second ferromagnetic disk.

In another aspect, the first back iron is disposed at an oblique angle with respect to the first non-ferromagnetic disk and the second back iron is disposed at an oblique angle with respect to the second ferromagnetic disk.

In another aspect, the oblique angle of the first back iron is the same as the oblique angle of the second back iron.

In another aspect, the rotor is an impeller, and wherein the impeller defines a plurality of hydrodynamic thrust bearings, and wherein the plurality of hydrodynamic thrust bearings face the second non-ferromagnetic disk.

In another aspect, the housing includes a center post, and wherein the rotor defines an opening sized to receive the center post, and wherein rotor rotates about the center post.

In another aspect, the center post includes a plurality of inner bearing magnets and wherein the rotor includes a plurality of outer bearing magnets, and wherein the plurality of inner bearing magnets and the plurality of outer bearing magnetics are configured to space the rotor a distance away from the center post, and wherein the plurality of inner bearing magnets are disposed at the oblique angle with respect the plurality of outer bearing magnets to cause the rotor to tilt at an oblique angle with respect to the major longitudinal axis.

In another aspect, the center post is symmetric about the major longitudinal axis.

In one aspect, the disclosure provides for a method of operating an implantable blood pump. The implantable blood pump includes an inflow cannula defining a major longitudinal axis and a rotor configured to rotate about the major longitudinal axis and impel blood downstream from the inflow cannula to an outlet downstream of the rotor. The method includes maintaining the impeller at a predetermined oblique angle with respect to the major longitudinal axis as it rotates about the major longitudinal axis.

In another aspect, the implantable blood pump is a centrifugal blood pump.

In another aspect, the oblique angle is between <NUM>-<NUM> degrees.

In another aspect, the implantable blood pump includes a stator having a back iron, and wherein the back iron is disposed at an oblique angle with respect to the major longitudinal axis.

In another aspect, the implantable blood pump includes a center post, and wherein the center post is disposed at an oblique angle with respect to the major longitudinal axis.

In another aspect, the implantable blood pump includes a center post, and wherein the center post includes a plurality of inner bearing magnets, and wherein the inner bearing magnets are disposed at an oblique angle with respect to the major longitudinal axis.

In another aspect, the implantable blood pump includes a stator having a back iron and a non-ferromagnetic disk disposed between the rotor and the stator, the back iron being spaced apart from non-ferromagnetic disk the and being disposed at an oblique angle with respect to the non-ferromagnetic disk.

In another aspect, the implantable blood pump includes a second stator having a second back iron and a second non-ferromagnetic disk disposed between the rotor and the second stator, the second back iron being spaced apart from second non-ferromagnetic disk the and being disposed at an oblique angle with respect to the second non-ferromagnetic disk.

In one aspect, the disclosure provides for a blood pump. The blood pump includes a housing including an inlet element, the inlet element having a proximal portion sized to be received within at least a portion of a heart of a patient and defining a major longitudinal axis. A rotor is configured to rotate within the housing about the major longitudinal axis and impel blood from heart. A first stator is disposed within the housing positioned downstream from the rotor and a second stator positioned within the housing positioned upstream from the rotor. A first non-ferromagnetic disk is disposed between the first stator and the rotor. During operation of the blood pump, the rotor is maintained at a predetermined and constant non-uniform distance from the first non-ferromagnetic disk.

Referring now to the drawings in which like reference designators refer to like elements there is shown in <FIG> an exemplary blood pump constructed in accordance with the principles of the present application and designated generally "<NUM>. " The blood pump <NUM> according to one embodiment of the disclosure includes a static structure or housing <NUM> which houses the components of the blood pump <NUM>. In one configuration, the housing <NUM> includes a lower housing or first portion <NUM>, an upper housing or second portion <NUM>, and an inlet element or inflow cannula <NUM> which includes an outer tube 18a and an inner tube 18b. The first portion <NUM> and the second portion <NUM> cooperatively define a volute-shaped chamber <NUM> having a major longitudinal axis <NUM> extending through the first portion and inflow cannula <NUM>. The chamber <NUM> defines a radius that increases progressively around the axis <NUM> to an outlet location on the periphery of the chamber <NUM>. The first portion <NUM> and the second portion <NUM> define an outlet <NUM> in communication with chamber <NUM>. The first portion <NUM> and the second portion <NUM> also define isolated chambers (not shown) separated from the volute chamber <NUM> by magnetically permeable walls.

The inflow cannula <NUM> is generally cylindrical and extends from second portion <NUM> generally along the axis <NUM>. The inflow cannula <NUM> has an upstream end or proximal end <NUM> remote from the second portion <NUM> and a downstream end or distal end <NUM> proximate the chamber <NUM>. The parts of the housing <NUM> mentioned above are fixedly connected to one another so that the housing <NUM> as a whole defines a continuous enclosed flow path. The flow path extends from upstream end <NUM> at the upstream end of the flow path to the outlet <NUM> at the downstream end of the flow path. The upstream and downstream directions along the flow path are indicated in <FIG> by the arrows U and D respectively. A center post <NUM> is mounted to first portion <NUM> along and symmetric about axis <NUM>. A generally disc-shaped ferromagnetic rotor or impeller <NUM> with a central hole <NUM> is mounted within chamber <NUM> for rotation about the axis <NUM>. The rotor <NUM> includes a permanent magnet and flow channels for transferring blood from adj acent the center of the rotor <NUM> to the periphery of the rotor <NUM>. In the assembled condition, the post <NUM> is received in the central hole of the rotor <NUM>. A first stator <NUM> having at least two coils a first back iron <NUM> may be disposed within the first portion <NUM> downstream from the rotor <NUM>. The first stator <NUM> may be axially aligned with the rotor along the axis <NUM> such that when a current is applied to the coils in the first stator <NUM>, the electromagnetic forces generated by the first stator <NUM> rotate the rotor <NUM> and pump blood. A second stator <NUM> including a second back iron <NUM> may be disposed within the second portion <NUM> upstream from the rotor <NUM>. The second stator <NUM> may be configured to operate in conjunction with or independently of the first stator <NUM> to rotate the rotor <NUM>.

Electrical connectors <NUM> and <NUM> are provided on first portion <NUM> and second portion <NUM> respectively, for connecting the coils to a source of power such as a controller (not shown). The controller is arranged to apply power to the coils of the pump to create a rotating magnetic field which spins rotor <NUM> around axis <NUM> in a predetermined first direction of rotation, such as the direction R indicated by the arrow in <FIG>, that is, counterclockwise as seen from the upstream end of inflow cannula <NUM>. In other configurations of the blood pump <NUM>, the first direction may be clockwise. Rotation of the rotor <NUM> impels blood downstream along the flow path so that the blood, moves in a downstream direction D along the flow path, and exits through the outlet <NUM>. A first non-ferromagnetic disk <NUM>, for example a ceramic disk, may be disposed within the first portion <NUM> downstream from the rotor <NUM> between the first stator <NUM> and the rotor <NUM>. A second non-ferromagnetic disk <NUM> may be disposed upstream from the rotor <NUM> within the second portion <NUM> between the second stator <NUM> and the rotor <NUM>. The first and second disks <NUM> and <NUM> may be composed of a ceramic material which is attached to the first portion <NUM> or the second portion <NUM> of the housing <NUM>. During rotation, hydrodynamic bearings <NUM> and a plurality of inner magnetic bearings <NUM> and a plurality of outer magnetic bearings <NUM> support the rotor <NUM> and maintain the rotor <NUM> out of contact with the inner surfaces of the first non-ferromagnetic disk <NUM> and the second non-ferromagnetic disk <NUM>. In other words, the operation of the rotor <NUM> is contactless in that it does not contact any component of the pump <NUM> other than fluid flowing through the pump <NUM>. The general arrangement of the components described above may be similar to the blood pump <NUM> sold under the designation HVAD® by HeartWare, Inc. , assignee of the present application. The arrangement of components such as the magnets, electromagnetic coils, and hydrodynamic bearings used in such a pump and variants of the same general design are generally described in <CIT>; <CIT>; <CIT>; and <CIT>.

Referring now to <FIG>, in one configuration, during operation of the pump <NUM>, the rotor <NUM> is maintained at an oblique angle with respect to the major longitudinal axis <NUM>. For example, the rotor <NUM> may be tilted with respect to the major longitudinal axis <NUM> such that a gap between at least one from the group consisting of the first non-ferromagnetic disk <NUM> and the second non-ferromagnetic disk <NUM> is maintained at a predetermined non-uniform distance. In particular, as shown in <FIG>, the rotor <NUM> has a smaller gap between the first non-ferromagnetic disk <NUM> toward a first hemisphere <NUM> of the first non-ferromagnetic disk <NUM> and a larger gap toward a second hemisphere <NUM> of the first non-ferromagnetic disk <NUM> opposite the first hemisphere <NUM>. This gap is maintained as the rotor <NUM> rotates about the axis <NUM>, as explained in more detail below, which may provide a gap through which thrombus can escape to avoid clotting or otherwise being deposited on the rotor <NUM>.

In one configuration, to achieve and maintain the tilt of the rotor <NUM> at an oblique angle, which may be, for example, between <NUM>-<NUM> degrees, or any oblique angle, the second back iron <NUM> of second stator <NUM> may be angled with respect to the second non-ferromagnetic disk <NUM>. In the example shown in <FIG>, the second back-iron <NUM> is angled at an oblique angle which causes the rotor <NUM> to be tilted at an opposite oblique angle. In other words, the second back-iron <NUM> is angled so that it is closer to the second hemisphere <NUM> of the second non-ferromagnetic disk <NUM> than the first hemisphere <NUM>. In such a configuration, the portion of the second back-iron that is closer to the rotor <NUM> exhibits a greater pull on the rotor <NUM> than compared to the portion of the back-iron <NUM> farther away from the rotor <NUM>. During operation, the hydrodynamic thrust bearings <NUM> push the rotor <NUM> away from the second non-ferromagnetic disk <NUM> and counteract the pulling force of second back iron <NUM>, thus the gap between the second non-ferromagnetic disk <NUM> and the second stator <NUM> is greater where the second back-iron <NUM> exerts less of a pulling force and the gap is maintained at this non-uniform distance.

In another configuration, as shown in <FIG>, both the second back-iron <NUM> and the first back-iron <NUM> are tilted at the same or substantially the same oblique angles, which may be between <NUM>-<NUM> degrees, with respect to their respective non-ferromagnetic disks <NUM> and <NUM>. The effect of both back irons <NUM> and <NUM> being tilted is to cause the rotor <NUM> to tilt at the same or substantially the same oblique angle as that of the back irons <NUM> and <NUM>. In particular, as with the configuration shown in <FIG>, the second back-iron <NUM> is closer to the second hemisphere <NUM> of the second non-ferromagnetic disk <NUM> compared to the first hemisphere <NUM> of the second non-ferromagnetic disk <NUM>, whereas the first back-iron <NUM> is closer to the first hemisphere <NUM> of the first non-ferromagnetic disk <NUM> compared to the second hemisphere <NUM> of the second non-ferromagnetic disk <NUM>. The tilt of the rotor <NUM> in this configuration may also be maintained at this non-uniform oblique angle during operation.

Claim 1:
A blood pump (<NUM>), comprising:
a housing (<NUM>) including an inlet element (<NUM>), the inlet element (<NUM>) having a proximal portion sized to be received within at least a portion of a heart of a patient and defining a major longitudinal axis (<NUM>);
a rotor (<NUM>) configured to rotate within the housing (<NUM>) about the major longitudinal axis (<NUM>) and impel blood from heart;
at least one stator (<NUM>, <NUM>) disposed within the housing (<NUM>) and positioned within the housing (<NUM>) at least one from the group consisting of upstream and downstream from the rotor (<NUM>); and
during operation of the blood pump (<NUM>), the rotor (<NUM>) is maintained at an oblique angle with respect to the major longitudinal axis (<NUM>).