Gas station without pumps

2022 March 24

Lower PVC frequency

Filed under: Circuits course — gasstationwithoutpumps @ 09:58
Tags: , , ,

In PVC: Premature Ventricular Contraction, PVC and pulse, PVC again, and No PVC while exercising I posted some ECG recordings of my heart to show the premature ventricular complexes. Yesterday I tried recording the ECGs again, this time using only 2 electrodes using Lead I (LA–RA) and connecting the bias wire to right-arm electrode.  When I’ve tried that in the past it has not worked well, but with the new amplifier I got reasonably good recording, with only a bit more noise than I usually get with a 3-electrode configuration.  I did not do direct comparisons of the 2-electrode and 3-electrode configurations—I’ll have to try that sometime soon.

The interesting result is that my PVCs seem to be much less frequent now.  In a fairly long (454-second) recording, I had 355 normal spikes and 13 PVCs—a PVC burden of only 3.5%, with a pulse rate of 48.5 bpm.


The resting pulses looked pretty much like other recordings I made (averaged over all the pulses.

I also made a recording while on the bicycle ergometer: 100s just sitting, 400s pedaling moderately hard, and 500s recovering.  There were very few PVCs in that recording also (only 13 detected, for a PVC burden of 0.9%).  The averaging of waveforms across the entire recording did not produce a very useful result, as the heart rate varied from around 45bpm to around 154bpm.  I probably should modify the software to produce averages over just a dozen or so beats, to get the noise reduction without the confounding effect of variation in rate.

My attempt to produce a bpm vs time graph was not very successful—the signal was noisy enough that the spike detection algorithm was occasionally missing a spike or picking up an extra one, so that the method I was using of just inverting the time for n periods resulted in a very noisy graph at the higher heart rates.  I spent most of yesterday looking at two other ways of determining the period—one using the peak in an FFT and phase changes at that peak between overlapping windows and one using peaks in autocorrelation.  None of the three techniques worked well enough to produce a smooth graph, so I’ll probably work on them some more to try to come up with a more robust pulse finder.

I’ll report on the algorithms when I get something a little better than I have now.


  1. […] Lower PVC frequency, I promised “I’ll report on the algorithms when I get something a little better than I […]

    Pingback by Better heartbeat detection | Gas station without pumps — 2022 March 29 @ 14:37 | Reply

  2. […] Lower PVC frequency, I said “I did not do direct comparisons of the 2-electrode and 3-electrode […]

    Pingback by ECG: 2-electrode vs. 3-electrode | Gas station without pumps — 2022 April 16 @ 12:23 | Reply

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