That sort of medical explanation from a TMS perspective usually means it's a normal anomaly, like gray hair of the spine is in relation to herniated discs. I did a quick perusal of the TMS literature, looking in the indexes and glossaries for heart conditions. The general answers were that "irregular" heart beats CAN be and usually are due to anxiety. The heart is one of the first organs to react to the release of adrenaline due to emotions. The heart naturally pumps faster in response to fearful situations--the fight/flight response. I recommend anyone here get a small library of TMS books together as part of their medicine cabinet, all four of Dr. Sarnos's books (so you have one left after you lend them out), Steven Ray Ozanich's , "THE GREAT PAIN DECEPTION" a TMS tome text for its great glossary of TMS conditons and as many other TMS books necessary to read until you turn the corner on your thinking about the causes of pain and trust yourself as much as the docs.
It sounds like you've been to the docs for your heart "condition", did they tell you to restrict your activities? I recall on one of my first doctor visits as a child, the doc saying to my dad that I had a heart-murmer--the doc was a cardiologist so he likely had a keen ear for any quirks in hearts. More then fifty years later I still remember it. You get labeled and compartmentalized by such loose medical talk. Since then I've completed thirteen marathons and hundreds of 5 and 10k races at respectable speeds and play tennis and swim daily.
I don't know the particulars of your case--and as per the TMS literature--you should get a medical work-up to rule out anything serious--sounds like you've been checked out at least a couple of times. Docs I've known, either leave you with a warning on the way out, to scare you healthy, because if you're healthy, they may not see you for a long time, and, like your mother did, wants to put a little fear of the Lord into you until your next office visit. Or, the kind of doc I have now, who will tell me a symptom is not a big deal--although his P.A., (physician's assistant), likes to scare me more.
So, back to you, look up "heart" or heart conditions, in the good TMS books, and you'll find many citations that irregular heart beats can be TMS/emotionally related.