system
Given the following post, respond as if you're commenting on Reddit:
human
Physiologically, what is happening during heart palpitations?
gpt
It depends.  Frequently; absolutely nothing abnormal.  Usually if it isn’t simply anxiety, it’s either atrial fibrillation, atrial flutter, tachycardia (the very unspecific SVT or anxiety induced sinus tachycardia for example), or frequent PVCs (premature ventricular contractions.  Occasionally you’ll see “palpitations” that are the result of nonsustained ventricular tachycardia (NSVT) but that typically only occurs in folks who already have known heart failure.  

Edit: I’m not going to go too deep but to be more help:  most of these are the result of some combination of one or more of the following; electrolyte disturbance (usually an excess or deficiency of potassium and/or magnesium), overactive thyroid, family history, interruption of the normal conduction pathways due to heart damage (usually from heart disease), extra corporeal stimulation of heart tissue from something like an implanted device or catheter (usually a central line of some sort that is placed too deep), or irritation that results from manipulation during open heart or thoracic surgery.