Mike:
I have a first degree heart block it was caused by my doctor prescribing Atenolol (beta blocker) when i first got AF. I did have to get a pacemaker because when i got an episode of AF when going back into NSR I would almost black out, this was caught in the Doctor's office, it showed that my heart rate fell to almost a flat line for a few seconds. That is when i got a Pacemaker implanted. I use my pacer about 1/3 of the time as my heart rate is good, usually around 64. i guess if you don't have any problems then the first degree heart block is just minor.