Heart rate measurement using blood pump impeller location
A method of determining a heart rate of a patient having an implanted blood pump including applying a voltage to a plurality of coils of a stator of the blood pump to produce an electromagnetic force to rotate a rotor in communication with the plurality of coils; displaying a waveform associated with a back electromotive force in the plurality of coils of the blood pump, the waveform being proportional to an axial position of the rotor relative to the stator; determining a time interval between a first alteration in the waveform relative to a baseline and a second alteration in the waveform relative to the baseline; and determining the heart rate of the patient based on the time interval.
1. A system comprising:
an implantable blood pump comprising a rotor and a stator with a plurality of coils, wherein the implantable blood pump is configured to pump blood from a chamber of a heart of a patient; and
a controller comprising a memory and processing circuitry configured to:
generate a waveform representing a back electromotive force in the plurality of coils during operation of the implantable blood pump;
detect a plurality of alterations in the waveform relative to a baseline, the plurality of alterations including one or both of rises and falls in the waveform relative to the baseline;
record a time interval between at least a pair of adjacent alterations of the plurality of alterations;
determine a heart rate of the patient based on the time interval; and
output an indication of the heart rate.
2. The system of claim 1 , wherein the waveform is proportional to an axial position of the rotor relative to the stator.
3. The system of claim 2 , wherein the axial position of the rotor relative to the stator is proportional to a thrust through the implantable blood pump, and the thrust is proportional to a fluid flow through the implantable blood pump.
4. The system of claim 1 , wherein the processing circuitry is further configured to determine the heart rate of the patient in a presence of a non-linear relationship between a fluid flow through the implantable blood pump and a motor current of the implantable blood pump.
5. The system of claim 1 , wherein the time interval corresponds to a complete heartbeat of the patient.
6. The system of claim 5 , wherein the processing circuitry is further configured to correlate the time interval to a predetermined figure to determine a number of heart beats per minute.
7. The system of claim 1 , wherein the baseline corresponds to an upper hysteresis band, and the processing circuitry is configured to detect a rise in the waveform in response to the waveform crossing the upper hysteresis band.
8. The system of claim 1 , wherein the baseline corresponds to a lower hysteresis band, and the processing circuitry is configured to detect a fall in the waveform in response to the waveform crossing the lower hysteresis band.
9. The system of claim 1 , wherein the processing circuitry is further configured to determine the heart rate of the patient based on a frequency analysis of the waveform.
10. The system of claim 1 , wherein the processing circuitry is further configured to determine a variability with respect to the determined heart rate of the patient over a select duration.
11. A device comprising:
a memory; and
processing circuitry configured to:
generate a waveform representing a back electromotive force in a plurality of coils of a blood pump device during operation of the blood pump device;
detect a plurality of alterations in the waveform relative to a baseline, the plurality of alterations including one or both of rises and falls in the waveform relative to the baseline;
record a time interval between at least a pair of adjacent alterations of the plurality of alterations;
determine a heart rate of a patient based on the time interval; and
output an indication of the heart rate.
12. The device of claim 11 , wherein the waveform is proportional to an axial position of a rotor of the blood pump device relative to a stator of the blood pump device.
13. The device of claim 11 , wherein the processing circuitry is further configured to:
determine the heart rate of the patient in a presence of a non-linear relationship between a fluid flow through the blood pump device and a motor current of the blood pump device.
14. The device of claim 11 , wherein the time interval corresponds to a complete heartbeat of the patient.
15. The device of claim 11 , wherein the baseline corresponds to an upper hysteresis band, and the processing circuitry is configured to detect a rise in the waveform in response to the waveform crossing the upper hysteresis band.
16. The device of claim 11 , wherein the baseline corresponds to a lower hysteresis band, and the processing circuitry is configured to detect a fall in the waveform in response to the waveform crossing the lower hysteresis band.
17. A method comprising:
generating a waveform representing a back electromotive force in a plurality of coils of a blood pump device during operation of the blood pump device;
detecting a plurality of alterations in the waveform relative to a baseline, the plurality of alterations including one or both of rises and falls in the waveform relative to the baseline;
recording a time interval between at least a pair of adjacent alterations of the plurality of alterations;
determining a heart rate of a patient based on the time interval; and
outputting an indication of the heart rate.
18. The method of claim 17 , wherein the waveform is proportional to an axial position of a rotor of the blood pump device relative to a stator of the blood pump device.
19. The method of claim 17 , further comprising determining the heart rate of the patient in a presence of a non-linear relationship between a fluid flow through the blood pump device and a motor current of the blood pump device.
20. The method of claim 17 , wherein the time interval corresponds to a complete heartbeat of the patient.