EFFICACY AND PROARRHYTHMIC HAZARDS OF PHARMACOLOGICAL CARDIOVERSION OF ATRIAL-FIBRILLATION - PROSPECTIVE COMPARISON OF SOTALOL VERSUS QUINIDINE

Objectives. This study compared the efficacy and safety of sotalol and quinidine for conversion and prevention of recurrent atrial fibrillat ion. Background. Atrial fibrillation is the most common arrhythmia. Ph armacologic therapy has been advocated for both immediate restoration of sinus rhythm and prevention of recurrent atrial fibrillation, Quini dine is the therapeutic mainstay for both purposes, but its safety has recently been questioned, Although sotalol has been used successfully to maintain sinus rhythm after direct current cardioversion, its effi cacy in pharmacologically reverting atrial fibrillation has not been e xamined. Methods. Fifty consecutive patients,vith persistent atrial fi brillation were randomized to receive quinidine or sotalol for up to 7 days to restore sinus rhythm, Patients were followed up for 6 months. Results. Quinidine was more effective than sotalol in terminating atr ial fibrillation (60% vs, 20%, p = 0.009). When nonresponders to drug therapy underwent subsequent direct current cardioversion, total conve rsion rates in the quinidine and sotalol groups were comparable (88% v s, 68%, p = 0.17), as was the efficacy of the two drugs in preventing recurrent atrial fibrillation. Side effects nesessitating drug discont inuation were more often observed with quinidine, No patient receiving sotalol but four patients receiving quinidine had drug-associated arr hythmia (torsade de pointes in three patients, sustained ventricular t achycardia in one patient). Precordial QT dispersion determined on the surface electrocardiogram (EGG) increased with quinidine (mean +/- SD 34 +/- 9 vs. 44 +/- 16 ms, p = 0.02), indicating enhanced inhomogenei ty in ventricular repolarization. There was no change in QT dispersion in patients receiving sotalol (36 +/- 18 vs, 40 +/- 17 ms, p = 0.44). Conclusions. Quinidine is more effective than sotalol in terminating atrial fibrillation but is associated with more side effects, The proa rrhythmic risk may be related to quinidine's propensity to increase di sparity in ventricular repolarization. This risk warrants careful ECG monitoring during the 1st 4 to 7 days of therapy, Because most proarrh ythmic effects occurred shortly after restoration of sinus rhythm, obs ervation should continue greater than or equal to 2 to 3 days after si nus rhythm is reestablished.