Caffeine and other stimulants can also cause a rapid heart rate, at least for me. No cough syrup, no antihistamines,..sugar can also cause me some palps. Just so aggravating. Trying to pinpoint what causes them each time I get PVC's or such is v,v hard tho. Sometimes they just come for no apparent reason at all. Make sure you stay well hydrated. And, yes stress can be a factor too.
Hey, my name is Chrissy. I am a medical care technician. I took an ECG class a few years ago and learned different heart rhythms. When you experience this how long does it last? If it only lasts a few minutes you are probably having tachycardia. My father used to have some kind of arrythmia that would cause that and he would have to take some deep breathes to get it to slow back down. Yes, stress can cause a bit of a rapid heart beat and so can anxiety. If you are getting yourself worked up when this happens it can cause it to keep beating rapidly.