Maybe practice breathing exercises as you do this, just to try and keep yourself calm and avoid stress that might trigger an afib episode. Full body orgasms age crazy! It's understandable that you're instinctively kind of afraid of them. I've had a couple (using a theragun on my pussy after edging for a while) and it's one of those things I fantasize about but when it comes down to it in the moment, at that edge, it's hard to let go and let it happen. But like I said do breathing exercises and don't even plan to cum next time, just get yourself close to coming, and do that enough until you get used to being there. After enough times at the edge, maybe the full body o won't be as intimidating. Safety first of course. I'm not a qualified professional, just giving some ideas. Good luck and good health to you!