Hi Vandemolen, B_jim and Demo,
The interim report mentions "a lowered heart rate and heart rate variability (HRV)" , but this is different from cardiac arrhythmia. They did not use the term "bradycardia", which is a heart rate below 60 bpm, and is a kind of arrhythmia. From my point of view, they use the measurement of heart rate and HRV only as a way to reflect the changes in vagal tone.
Maybe POIS can cause arrhythmia for certain POIS sufferers, but I do not think that the report makes any statement about that.
In my own case, POIS causes me marked hypotension ( when no prevention used), but no arrhythmia, and no cardiac problems.