Sick Sinus Syndrome? (Sudden slow beats that last for hours to days...)

[Dracom]

I have been experiencing what I can only describe as heart rate irregularities since the beginning of last year and they have always been rather episodic. I have been trying to identify and eliminate triggers from caffeine and large meals to poor sleep but to no avail. Before I started taking beta-blockers last August, these sudden slow beats would be associated with tachycardia and cause my heart rate to maintain in the 90s to 100s for hours. While I don't have any symptoms like fainting or angina during these episodes, they tend to cause anxiety and mild chest discomfort as I am aware of the sensations.

Recently, I bought a portable ECG/EKG monitor (Kardia/Alivecor) to check for ectopic beats. While I have managed to capture and interpret the odd PAC and PVC, this one has me stumped. It always begins as a faint flutter in the top of my chest (it's like I can feel it coming). This is then followed up by a sudden drop in heart rate as can be seen here:

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As the waves themselves show no deformation at all (like in the case of PVCs/PACs/Afib would), I was wondering if this is something other than a regular ectopic.

I've had an echo and 24-hour Holter monitor done recently, but that turned up nothing. I've approached my own cardiologist on this issue, but he doesn't seem to think anything of it citing PVCs and PACs. Could it be just a regular fluctuation of my heart rate that I've just become far more sensitive to? Are there PVCs and PACs that do not show up as deformed waves on the ECG? Something related to an overly sensitive vagus nerve? Is it related to body position/muscle spasm that leads to heart irritation? Or is it Sick Sinus Syndrome? Is that something that they would have caught during the echo?

The thing is, I'm used to PVCs and PACs and have already made my peace with them. As long as I am assured that these slow beats are benign, I can move on with my life. However, at this point in time, I have yet to get a clear answer as to what these sensations are and they are weighing on my mind...

[Dracom]

Dracom…. I had a look at your self-administered ECG (I also have various arrhythmias which I monitor using a Healforce ECG). Even though I’ve looked at hundreds of my traces and many others on the internet, I’m not a qualified person. But I would hazard a guess that you’re getting the odd PVC followed by a compensatory pause. Unlikely to be sick sinus syndrome.

The rest of your trace (excluding that one noticeable PVC and pause) shows a heart rate varying from about 66 to 75 bpm – normal, in other words.

Presuming your cardio did a twelve lead ECG (far more accurate than any two/three lead version) along with the ambulatory monitoring, and found nothing remarkable, then I think you should believe him (even though the most benign of arrhythmias can be unpleasant and worrying – I’ve been having mine for over thirty-odd years and they haven’t finished me off yet).

Thank you very much for the reassurance. Indeed, the doctors did do multiple 12-lead ECGs in addition to a 24-hour Holter monitoring. However, as these beats were episodic, they didn't show themselves during those times.

I would like to think that they are PVCs or PACs, as I do sometimes get them, but as mentioned, the waveform doesn't really show any kind of distortion like you would when getting PVCs or PACs.

I know I'm not an expert either, but I did some googling and the reading seems to match perfectly up with a sinoatrial exit block or pause:

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I forgot to mention that I do actually have a weakened aortic valve, causing aortic regurgitation, so sinoatrial exit blocks or pauses are not out of the question.

I know self-diagnosing isn't really a good thing, but I wanted something to present to my doctor during my next appointment. Fortunately, this is one of those cases were googling turned out to be far more reassuring than anxiety-inducing as it seems that these things do not warrant treatment (with a pacemaker) unless symptomatic.

Then again, it just might be an oversensitive Vagus nerve or something... Gah, I hate that ectopic beats never show up during proper ECG scans...