Heart rhythm concerns - audio included?

Your symptoms, like exhaustion after exertion, the irregular heart beat, sounds very much like Atrial Fibrillation: the electrical impulses that cause the heart to contract go haywire (not a medical term lol) firing irregularly and from places they shouldn't. The only confusing thing is your ability to sprint at all. There is no one identified cause for this condition, but all those electrical shocks you've received might be a place to start. The thing is, this condition can happen to anyone at any age, though of course it is more likely to manifest in the older population. The length of time you have the condition has a bearing on the prognosis, so you probably shouldn't wait too long to have it checked. Good luck.