Comparative efficiency of quinidine and verapamil in the maintenance of sinus rhythm after DC conversion of atrial fibrillation. A controlled clinical trial.

Fifty-three patients with chronic atrial fibrillation participated in a randomized cross-over trial in order to compare the ability of two drug regimens to establish and maintain sinus rhythm. The patients were given orally either sustained release quinidine 0.4 g twice day or verapamil 80 mg three times a day. Thirty-one patients tried both regimens. Quinidine was found to have a greater ability to induce conversion to sinus rhythm by drug alone (p less than 0.05) and also a greater ability to maintain sinus rhythm after conversion (after 3 months p less than 0.05). There was, however, also a significantly larger proportion of patients on quinidine who were withdrawn from the study due to side effects and two patients on quinidine died outside hospital. The study indicate that quinidine is somewhat superior to verapamil both in the establishing and preserving of sinus rhythm in subjects who are able to tolerate the drug.