Safety and effectiveness of oral quinidine in cardioversion of persistent atrial fibrillation.

The effectiveness of oral quinidine for conversion of atrial fibrillation to sinus rhythm was evaluated in 49 patients with persistent atrial fibrillation on anticoagulation therapy. Atrial fibrillation was considered as persistent when the duration was longer than 3 days but less than 6 months. Patients received orally one to 7 doses of 150 mg hydroquinidine hydrochloride every one hour until restoration of sinus rhythm, or to a maximum of 7 tablets. Patients who were not converted underwent elective electrical cardioversion. Thirty-nine of 49 patients (79.6%) were converted with quinidine and only one of the remaining 10 was converted with electrical cardioversion. Quinidine had no significant effect on blood pressure or unexpected changes on the QRS duration and the QT interval. Four patients developed gastrointestinal symptoms (8.1%). Oral quinidine was safe and effective in the conversion of persistent atrial fibrillation to sinus rhythm.