The incidence of asymptomatic paroxysmal atrial fibrillation in patients treated with propranolol or propafenone.

Anti-arrhythmic therapy for paroxysmal atrial fibrillation leads to complete symptomatic relief in a number of patients. The elimination of symptoms may be associated either with a complete elimination of arrhythmia or with a conversion of symptomatic atrial fibrillation into asymptomatic episodes of arrhythmia. The aim of the study was to evaluate the occurrence of asymptomatic paroxysmal atrial fibrillation in 52 patients treated with propafenone (35 drug trials) or propranolol (34 drug trials) by means of ambulatory ECG Holter monitoring. Propafenone was clinically effective (complete relief of symptoms) in 26 (74%) patients. However, in 7 cases (27%) asymptomatic episodes of arrhythmia were still recorded when awake. In patients treated with propranolol clinical symptoms were absent in 18 (53%). However, in 4 (22%) patients attacks of paroxysmal atrial fibrillation were present. The mechanism of drug-induced conversion of symptomatic episodes of atrial fibrillation into asymptomatic spells of arrhythmia was a marked shortening in duration of episodes in 7 patients (from 2215 +/- 3843 s to 16 +/- 10 s, N.S.) or by a significant slowing of ventricular response during atrial fibrillation in 4 patients (from 125 +/- 27 to 84 +/- 8 beats/min, P = 0.05). In conclusion, in a significant proportion of patients with symptomatic paroxysmal atrial fibrillation asymptomatic episodes of arrhythmia may occur while on anti-arrhythmic drug therapy. Some of these patients, particularly those with other risk factors for stroke such as advanced age or the presence of organic heart disease, may require anti-coagulant therapy or change in anti-arrhythmic treatment, and can be selected on the basis of ambulatory ECG monitoring.