I Was Diagnosed With A-fib/A-flutter 4 Months Ago. Finally, My

I was diagnosed with A-fib/A-flutter 4 months ago. Finally, my cardiologist did a cardioversion about 12 days ago and it got my heart back in sync. Soon after, my pulse dropped to the high 30s and I felt weak and anxious plus a bit dizzy. I told him and he changed my diltiazem from 240 to 180 and told me to come back in 3 months. I still have the same symptoms plus I now have a rash. I tried to quit altogether. Still taking a half of a 10 mg lisinopril daily. My pulse and blood pressure swings from too low toward the high side after not taking diltiazem for 2 days. How do I get off this stuff? My heart works good now. I don't need it. Thanks