Where are you from that you list your weight in "Stones"? I looked it up and am now familiar with the weight you are speaking of.
Adrenaline can be a real problem. I have anxiety about my arrhythmia, PVC's (Trigeminy for about 20 cycles or so, then normal, PVC's, back to Trigeminy, a few Bigeminys thrown in for good measure, etc.) and occasional PSVT. Not all day but it comes in cycles throughout the day. My Doctor assures me my heart is functionally normal, I am just having problems with stress. Also, I have a swallowing induced component to the arrhythmia that the Doctor feels is caused by Vagal Responses.
Once the fear gets hold of you it's hard to stop the cycle. I would jump out of bed due to my arrhythmia and my wife would tell me to relax. I could feel my face getting hot and my breathing becoming rapid, and the PVC's would get worse. I have taken Klonopin and eventually begin to relax. I have fallen asleep at the computer since I didn't want to lay in bed again and fret about the arrhythmia. Slowly making my way to bed from the computer, the Klonopin seemed to help, but at times I have lost so much sleep I pay for it the next day. My Doctor says just go to sleep and don't worry about it. Right!
More recently I have been put on Paxil. I take a small dose as of yet, and I feel more tense than ever. BUT, I somehow seem to be better able to tolerate the arrhythmia, at least most of the time.
Sleep and Breathing. Get as much sleep as humanly possibly. For the most part, when you are asleep, you are not in stress. I awake feeling fine, for about 2 minutes. I can feel my stomach tense and my PVC's start.
I have also noticed that my breathing seems to be part of the reason for my arrhythmia. At least I can almost always hold my breath-in (a moderately deep breath) and my arrhythmia stops. I have also noticed that I can sometimes (more than should be possible from coincidence) protract my breathing as I breath out and stop the arrhythmia (until I breathe in again). I breathe like a hamster. Very frequent but very short breaths. I am sure in my case, if I were to learn to breathe correctly and deeply that I would have less problems with the arrhythmia. The times that I have been most arrhythmia free is the times I can remember breathing a natural deep in and out with natural pauses at either end of the cycle. Watch someone sleeping or take notice of your own breathing when you are all but asleep.
I just had a test for Catecholamines. (Epinephrine, Norepinephrine, and Dopamine), though the Doctor feels that I would be symptomatic other than the constant anxiety and PVC's if I had a problem with the levels. I am awaiting the results.
What is your pulse. Mine was 60 BPM with 37.5 mg Atenolol twice a day (I broke a 25 mg in half and took it with a 25 mg). On 40 mg Nadolol, I was running about 56 BPM. Pretty good indicator that the Beta-Blocker is working. But it has it's limitations. Too much adrenaline seems to overwhelm it, the pulse is still low but the darned PVC's can be quite bad.
Wish you a normal ryhthm for your heart and life.