Speedy recovery John, one of my best friends is on exactly the same journey as you, so debilitating when he's having a bad day so I understand the angst it must be causing you.
a good few years ago he was bitten by a deer tick & contracted lyme disease which went undiagnosed for approx. 3 months, he's been told that this was unlikely to have been the cause of his heart problems but I'm not so sure, you never get rid of lyme disease once you've got it.