Prognostic significance of arrhythmia in tetralogy of fallot after intracardiac repair

The significance of arrhythmia and conduction defects was studied in 395 patients who underwent intracardiac repair of tetralogy of Fallot between 1958 and 1976. In 91 of these patients (group I), the median date of repair was 1964 and all underwent stress testing. In 107 patients (group II), the median date of repair was significantly later (1971), but all subjects were too young for stress testing. The remaining 197 patients (group III, median date of repair 1963) included all those who did not participate in stress testing or who had died; 42 of these patients were later excluded from analysis because of insufficient electrocardiographic records. The overall incidence of any form of arrhythmia (19 percent) was the same for each group. However, in group II (patients who underwent intracardiac repair more recently), no tachyarrhythmia was observed and there were fewer patients with 1° atrioventricular (A-V) block (p <0.001) and more patients with complete right bundle branch block (p <0.001) than in groups I and III. In two patients (both in group I), unexpected, late sudden death unrelated to strenuous physical activity occurred. Arrhythmia was least common in patients with primary intracardiac repair and more common in those with either palliation before intracardiac repair or multiple intracardiac repairs. In group I, 41 of 91 patients with arrhythmia of even minor degree at rest (n = 13) or exercise (n = 28) had a significantly larger heart, greater right ventricular pressure and lesser exercise performance than did those without arrhythmia, thus suggesting the presence of residual abnormality or dysfunction. No tachyarrhythmia was induced by exercise in this study. Patients with either arrhythmia or bifascicular block have generally had a benign course without strong evidence of progression of arrhythmia.