Look - if you have even the slightest suspicion that you are having a heart problem - whether an exercise induced arhythmia, an electrolyte imbalance, a reaction to a temperature or hydration situation - Go To The Doctor.

Saying something is an arythmia or a fibrulation does not mean that it's OK to have those. Some of them are OK, some of them lead to something called "Sudden Cardiac Death." I'm totally not making this up, I learned it from my cardiologist.

I just went through this a couple months ago. I ride 8000+ miles a year, am not overweight, and have minimal cardiac risk factors apart from family history - and the second I said "chest pain" the advice nurse told me to come to the ER. I don't want to share all the details, but it did turn out I had some test results that were worth knowing.

Any doctor will take this very seriously, and the first round of testing can be non-invasive and relatively inexpensive. It's just not something to screw around with - there are conditions that can make you literally drop dead, with no or almost no warning. At any age and at any fitness level.

Anyway, My $.02, it's your life.