[Bifascicular block: long-term follow-up. Report of 40 cases].

A total of 14,500 E.C.G. tracings were reviewed to determine the incidence of bifascicular block and those patients were followed up to assess prognosis. Forty patients with bifascicular block (complete right bundle branch block associated with left anterior hemiblock), diagnosed with standard E.C.G., according to Medrano's criteria from January 1978 to September 1980 were studied in our Service. The incidence of this intraventricular conduction defect was 0.0033 (3.3 per thousand). Males predominated over females at a rate of 2.4 to 1. This block was more frequent from the sixth to the ninth decades of life. Thirty five percent of the patients had no evidence of cardiovascular pathology; 32.5 percent had high blood pressure, 2.5 percent had coronary heart disease, 2.5 percent rheumatic heart disease, 5 percent chronic pulmonale, and 37.5 percent had diabetes mellitus as an associated finding. During the follow up which covered 20.2 months/patient, only one patient developed junctional rhythm and periods of asystolia and syncope; this case was treated with a permanent pacemaker with good results. Two patients died, one from digitalis intoxication and the other at home, the cause was not determined. It is necessary to study this conduction defect with longer follow up periods and according to the underlying heart disease, in order to assess properly the prognosis and behavior of this conduction defect.