Woodie, several years ago I had what is called "ventricular tachycardia" which was a racing of my heart, up to 200 bpm. This was relieved in ER several times before I had have an ablation, where they went in a lasered a nerve pathway on the outside of my heart.
I'm not trying to diagnose you by any means, but was wondering if they had considered this?
The ablation itself took a lot of time...seems like it was 4 hours, you're kept in a "twilight" sleep during, so don't feel anything. They ran the laser up through the arteries in my groin. My problem was I kept snoring lol, and they did wake me as he lasered the nerve, but them put me back under quickly, so its not really painful. I've not had any experiences since of rapid heart beat.
Good luck to you and hope your depression lifts. My thoughts and prayers are with you.