Cardiac pump with speed adapted for ventricle unloading
A blood pump system is implantable in a patient for ventricular support. A pumping chamber has an inlet for receiving blood from a ventricle of the patient. An impeller is received in the pumping chamber. A motor is coupled to the impeller for driving rotation of the impeller. A motor controller is provided for tracking systolic and diastolic phases of a cardiac cycle of the patient and supplying a variable voltage signal to the motor in a variable speed mode to produce a variable impeller speed linked to the cardiac cycle. The impeller speed comprises a ramping up to an elevated speed during the diastolic phase in order to reduce a load on the ventricle at the beginning of the systolic phase.
1. A blood pump system for implanting in a patient for ventricular support, comprising:
a pumping chamber having an inlet for receiving blood from a ventricle of the patient;
an impeller received in the pumping chamber;
a motor coupled to the impeller for driving rotation of the impeller; and
a motor controller for determining a time period of a systolic phase and a time period of a diastolic phase of a cardiac cycle of the patient, and supplying a variable voltage signal to the motor in a variable speed mode to produce a variable impeller speed linked to the cardiac cycle, wherein the impeller speed comprises a ramping up to an elevated speed beginning at a point in time during the determined time period of the diastolic phase, and prior to the determined time period of the systolic phase in order to reduce a load on the ventricle at the beginning of the systolic phase.
2. The pump system of claim 1 wherein the impeller speed comprises a ramping down to a reduced speed during the systolic phase to avoid collapse of the ventricle.
3. The pump system of claim 1 wherein the cardiac cycle provides a variable flow rate, and wherein the motor controller changes in the impeller speed inversely with changes in the flow rate.
4. The pump system of claim 3 wherein the variable speed mode is comprised of a constant current mode.
5. The pump system of claim 1 wherein the variable speed mode is comprised of matching impeller speed to a target speed.
6. The pump system of claim 5 wherein the target speed ramps up to the elevated speed during the diastolic phase and ramps down to a reduced speed during the systolic phase to avoid collapse of the ventricle.
7. The pump system of claim 6 wherein the ramp up of the target speed begins at a moment between about 50% to about 90% into the diastolic phase.
8. The pump system of claim 6 wherein the ramp down of the target speed begins at a moment between about 50% to about 90% of the systolic phase.
9. The pump system of claim 1 wherein the motor controller is configurable to provide the variable voltage signal to the motor in either the variable speed mode or a constant speed mode, wherein the constant speed mode maintains a substantially constant speed of the impeller over each respective cardiac cycle, and wherein a selection between the variable speed mode and the constant speed mode is determined according to a physiologic capability of the patient.
10. The pump system of claim 1 wherein the motor controller includes a current sensor, and wherein the motor controller tracks the systolic and diastolic phases in response to a waveform from the current sensor.
11. The pump system of claim 1 wherein the motor controller is adapted to communicate with a pacemaker implanted in the patient in order to track the systolic and diastolic phases.