Efficacy of type 1C antiarrhythmic agents for treatment of resistant atrial fibrillation.

In order to determine the efficacy of type 1C agents (flecainide, encainide, propafenone) in patients with atrial fibrillation who have failed to maintain sinus rhythm with type 1A agents (quinidine, procainamide, disopyramide), 147 patients, that were admitted into the John Dempsey Hospital with new or recurrent atrial fibrillation between 1987-1991, were studied retrospectively. Out of the total, 29 patients converted spontaneously to sinus rhythm, 14 patients were left in atrial fibrillation, and 104 patients were given a type 1A antiarrhythmic. Sixty-five of these patients remained in sinus rhythm (54% converted on drug alone, 46% required electrical cardioversion) for at least 6 months. Of the remaining 39 patients, 28 were given a type 1C antiarrhythmic; 13 were successfully converted (61% chemical, 39% electrical) to and remained in sinus rhythm for at least 6 months; the remaining 15 either failed to convert or reverted to atrial fibrillation. New onset atrial fibrillation had a significantly lower incidence of congestive heart failure (10%) than recurrent atrial fibrillation (33%; P < 0.01). No differences in digoxin, beta blocker use, or other clinical characteristics were seen either between type 1A or type 1C successes or failures. Similarly, echocardiographic dimensions did not predict success or failure with either class of agent. In conclusion, type 1C antiarrhythmics for suppression of recurrent atrial fibrillation represent a reasonable therapeutic alternative for suppression of atrial fibrillation in patients who have failed type 1A agents. Prognostic factors predicting success or failure remain undetermined.