Hi, Michael. Congratulations on quitting smoking. That s quite an accomplishment. It is difficult but certainly worthwhile for your health. A-fib, or Atrial Fibrillation, can be aggravated by stress, electrolyte deficiencies (usually potassium, but sometimes calcium or magnesium), caffeine and other stimulant drugs, and binge-drinking of alcohol. If your heart sonogram (or Echocardiogram) is normal, showing normal heart chamber sizes and normal valvular function, that usually lowers the risk of recurrent A-Fib. You don t say whether your heart rhythm went back to normal or whether it is still fibrillating (an important distinction in deciding whether we can stop or need to continue certain heart drugs). Cardizem, a brand of Diltiazem, is one drug that we sometimes use to either slow the rapid pulse of A-Fib or to help maintain normal rhythm. You should tell your doctor what side effects you feel or why you feel you cannot tolerate the cardizem. There are other classes of drugs that could be tried to maintain normal rhythm. If you can stop drinking alcohol, it is possible that you could be observed or have a 24-hour EKG monitor to screen you for recurrent A-Fib, without being on a drug unless the arrhythmia returns. You could try to search for either another Cardiologist or perhaps an Electrophysiologist (or Cardiac Electrophysiologist). Those doctors I call Arrhythmia Specialists, and they can monitor or treat you with specialty expertise. The Electrophysiologist can also recommend or perform an EPS test to search for the abnormal electrical pathway that triggers your A-Fib; this invasive test can be followed by an Ablation, in which the doctor burns that electrical wire within the heart to try to prevent the A-Fib from recurring. For people who have side effects or drug intolerances from anti-arrhythmic drugs, an ablation can successfully prevent recurrence and remove the necessity to take medicine, since burning out the pathway that caused the arrhythmia has a very high success rate for preventing future occurrences. If the electrical wire is removed/burnt/ablated, then there is no need to take a medicine to calm it down or keep that wire inactive. Good luck to you.