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 < 0.02). Study group members less than 18 years of age (32 patients) had a similar frequency of conduction defects when compared wih 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.