Gas station without pumps

2022 February 18

No PVC while exercising

Filed under: Circuits course — gasstationwithoutpumps @ 14:44
Tags: , , ,

In PVC: Premature Ventricular Contraction, PVC and pulse, and PVC again I posted some ECG recordings of my heart to show the premature ventricular complexes.

This week, I built a new ECG amplifier with a lower gain (especially on the first stage), with the voltage reference in the middle of the voltage range, and with a somewhat higher corner frequency for the high-pass filter, so that I would not clip the signals, even if there were fairly substantial movement artifacts.   I’m not going to provide that design here, as the design is still a lab in my textbook (and I have caught students copying not-so-great designs from earlier blog posts, without understanding what they were copying).

I also used longer wires to connect to the electrodes, so that I could sit upright on my bicycle ergometer without pulling the amplifier off the book rest on the handlebars. Because I was just recording Lead I (left arm minus right arm), I put the body-bias electrode on my sternum, halfway between the other electrodes, rather than as a left-leg electrode, so that I could keep the wires bundled together better.  This seemed to work fine for recording Lead I.

I recorded the ECG signal both resting (sitting at a table) and exercising, but I did not use the optical pulse monitor. The exercise session started out with me sitting still on the ergometer, then pedaling at about 70rpm with a resistance of about 30 N•m (about 220W).

I modified the software to report the instantaneous beats per minute (based on 6 periods):

bpm-2022-Feb-17

The resting heart rate shows some fluctuation, which seems to be at lest partially due to PVCs disrupting the normal rhythm, but the normal sinus beats are a bit irregular also. The exercise shows a smooth increase from about 60bpm to 148bpm, then a gradual recovery as I stopped pedaling. The two big upward spikes and the big downward spike are places where they simple spike detector I was using either caught an extra spike or missed a spike. I looked at the bandpass-filtered signal in those places, and I did not see an easy way to improve the spike detector.

 

The resting recording was similar to my previous ones, showing an average heart rate of 49.5bpm, with 156 normal spikes and 53 PVCs, for a PVC burden of 25.9%. 

The exercise recording showed very few PVCs (only 4)—and those at the beginning and end of the recording, when I was not exercising.   My average heart rate was 113.5bpm, with 601 normal spikes and 4 PVCs, for a PVC burden of 0.6%.  It looks to me like normal sinus beats prevent the PVCs, and I only get PVCs when my sinus rhythm drops way down—as if my heart was trying to compensate for inadequate pacemaking at the sinoatrial node.

Lead-I-2022-Feb-17

The averages for the normal ECG recordings are fairly similar, thought the T-wave seems to be smaller and earlier in the exercise recording. The exercise PVC average is only averaging 4 spikes, and so is very noisy. It is not clear to me whether the slightly earlier T-wave is meaningful here—though it does seem to correspond with the earlier time when exercising for the normal T-wave.

Also this week I contacted  Dr. Gregory M. Marcus at UCSF, who wrote Evaluation and Management of Premature Ventricular Complexes by , Circulation. 2020;141:1404–1418 https://doi.org/10.1161/CIRCULATIONAHA.119.042434. I asked whether there were any more recent articles about risk for people in my circumstances (normal left-ventricular ejection fraction (LVEF), no symptoms, >10% burden) and whether there was any information about people who developed PVCs after having sinus bradycardia.  He told me that he knew of no newer material and no known connection between extant sinus bradycardia and PVC burden.  He just repeated the suggestion to get an echocardiogram annually and not be otherwise treated until something changes. 

Now that I know that my PVCs decrease when I exercise, I went looking for papers that might make sense of that.  I found  “Significant reduction in the density of premature ventricular complex with ß-blocker medication in fast rate-dependent premature ventricular complex” by Park, Y.M., Kim, C.Y., Seo, J. et al.  Int J Arrhythm 21, 20 (2020). https://doi.org/10.1186/s42444-020-00028-2, in which they categorized PVC patients into 3 groups: those whose rate of PVCs went up with heart rate (fast rate-dependent PVC), those whose PVCs went down with heart rate (slow rate-dependent PVC), and those whose PVCs seemed independent of heart rate.  I believe that I fall into the second group, though I’ve not worn a 24-hour Holter monitor to determine this the way they did.  The take-away from the article is that it probably would not do any good for me to take beta-blockers (which I wasn’t planning to do anyway).

Aside: I found it rather amusing that the article in the International Journal of Arrhythmia used the wrong character for β-blockers, referring to them as ß-blockers (using the German Esszett character instead of the Greek lower-case beta). I don’t fault the authors (who were all Korean), but the reviewers and copy-editors of the journal, who should have caught the error.

1 Comment »

  1. […] 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 […]

    Pingback by Lower PVC frequency | Gas station without pumps — 2022 March 24 @ 09:58 | Reply


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