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 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, the baseline being an upper hysteresis band, and a second alteration in the waveform relative to the baseline; and
determining the heart rate of the patient based on the determined time interval.
2. The method of claim 1 , wherein the first alteration is a first rise in the waveform relative to the baseline and the second alteration is a second rise in the waveform relative to the baseline.
3. The method of claim 2 , further comprising recording a plurality of time intervals between a plurality of rises in the waveform relative to the baseline and calculating the heart rate based on the plurality of time intervals.
4. The method of claim 1 , wherein the first alteration is a first fall in the waveform relative to the baseline and the second alteration is a second fall in the waveform relative to the baseline.
5. The method of claim 4 , further comprising recording a plurality of time intervals between a plurality of falls in the waveform relative to the baseline and calculating the heart rate based on the plurality of time intervals.
6. The method of claim 1 , wherein the axial position of the rotor relative to the stator is proportional to a thrust through the blood pump, and the thrust is proportional to a fluid flow through the blood pump.
7. The method of claim 6 , further comprising determining the heart rate of the patient in a presence of a non-linear relationship between the fluid flow through the blood pump and a motor voltage of the blood pump.
8. A method of determining a heart rate of a patient having an implanted blood pump comprising:
generating a waveform representing a back electromotive force in a plurality of coils of the blood pump during operation;
detecting a plurality of alterations in the waveform relative to a baseline, the plurality of alterations being one of the group consisting of a rise and a fall in the waveform relative to the baseline, the baseline is an upper hysteresis band, and the rise in the waveform includes a crossing of the upper hysteresis band;
recording a time interval between at least a pair of adjacent alterations of the plurality of alterations; and
determining the heart rate of the patient based on the time interval.
9. The method of claim 8 , wherein the blood pump includes a rotor and a stator in communication with the rotor, and the waveform is proportional to an axial position of the rotor relative to the stator.
10. The method of claim 9 , wherein the axial position of the rotor relative to the stator is proportional to a thrust through the blood pump, and the thrust is proportional to a fluid flow through the blood pump.
11. The method of claim 10 , further comprising determining the heart rate of the patient in a presence of a non-linear relationship between the fluid flow through the blood pump and a motor current of the blood pump.
12. The method of claim 8 , wherein the time interval corresponds to a complete heartbeat of the patient.
13. The method of claim 12 , further comprising correlating the time interval to a predetermined figure.
14. The method of claim 13 , further comprising dividing the time interval by the predetermined figure of sixty to determine a number of heart beats per minute.
15. The method of claim 1 , further comprising correlating the waveform to a lower hysteresis band separate from the upper hysteresis band, and wherein the fall in the waveform includes a crossing of the lower hysteresis band.
16. The method of claim 8 , further comprising calculating the heart rate of the patient based on a frequency analysis of the waveform.
17. The method of claim 8 , further comprising determining a variability with respect to the determined heart rate of the patient over a select duration.