Oi yous two - sqad's fancy piece is here, and I have not mentioned farting for yonks.... I have turned over a ladylike new leaf..
anyway, barron, I agree with sqad - no use speculating until you've had tests such as ecg, echocardiogram etc. There are many causes - when you say 'racing heart' - do you mean palpitations, ectopics (missed beats) or tachycardia? Is it constant, intermittent? At times of stress or particular positions (no sniggering you lot).
Seriously, I had svt since I was 12 - finally got it sorted out last year at Papworth by a brilliant lovely surgeon who was a dead ringer for Mr Bean. It had slowly worsened over the years, due to various factors, until it got to the point it was dangerous not to get it sorted. Prior to that, I lived with it for 36 years, mostly with no medication or treatment, just regular investigations. Then medication such as Verapamil.
I'm no cardiologist, but know quite a lot from personal experience. Many causes - stress, caffeine etc can be a cause - but you need to go to a GP to find out for sure. xx
(I do not fart bytheway; listen not to these two stirrers.... I flatulate. Rarely. And it always has the odour of Coco Chanel.)