Chronic Bifascicular Block: Evaluation of Familial Factors

We studied whether familial factors are significant in chronic bifascicular block. One hundred thirty-four first- and second-degree relatives of 44 outpatients with chronic bifascicular block were examined. These relatives were studied to ascertain the presence or absence of cardiac disease and conduction defects. A race-, age-, and sex-matched control group (age range, 18 to 65) was randomly chosen from a population of employed volunteers for comparison purposes. The study group had a significantly greater frequency of conduction defects than the control group (24/95 versus 10/95, P less than 0.02). Study group members less than 18 years of age (32 patients) had a similar frequency of conduction defects when compared with patients described in the literature. In study group members older than 65 years, 5 out of 7 had conduction defects, a high frequency. In conclusion, the findings suggest an age-related familial tendency to conduction disease among relatives of patients with chronic bifascicular block.