Acute effect of disopyramide on atrial fibrillation in the Wolff-Parkinson-White syndrome.

Disopyramide was administered intravenously to 54 patients during atrial fibrillation and predominantly pre-excited QRS configuration at the time of electrophysiologic study. All patients had Wolff-Parkinson-White syndrome and no patient had coexistent heart disease. The drug was given during sustained atrial fibrillation (n = 45) or during sinus rhythm before induction of atrial fibrillation for patients whose atrial fibrillation was self-terminating in the control state (n = 9). Atrial fibrillation converted to sinus rhythm within 15 min after disopyramide in 37 (82%) of the 45 patients. The shortest RR intervals between two pre-excited cycles increased from 208 +/- 42 to 293 +/- 117 ms (p less than 0.0001). The average RR interval of all cycles prolonged from 332 +/- 60 to 396 +/- 117 ms(n = 45, p less than 0.0001). The 9 patients in whom pre-excitation was abolished after the drug had a significantly longer initial shortest RR interval than that of the 36 patients in whom pre-excitation persisted (246 +/- 47 versus 199 +/- 36 ms, p = 0.0022). No patients developed significant hemodynamic or other adverse effects after disopyramide. These data support the intravenous use of disopyramide in patients with normal ventricular function who have atrial fibrillation and a predominant ventricular response over an accessory atrioventricular pathway.