An Epidemiological Assessment of Bundle-Branch Block

Complete bundle-branch block was found in 57 of 1,560 (3.7%) electrocardiograms routinely recorded on members of a retirement community. Of this number, 19 were identified as left bundle-branch block (LBBB), while 38 fulfilled the criteria for right bundlebranch block (RBBB). Individuals with LBBB were found to have cardiomegaly more frequently than did individuals with normal electrocardiograms. Individuals with RBBB, regarded as a homogeneous group, also demonstrated a greater prevalence of cardiomegaly than did the control group, but the difference from normals was less striking than in the case of LBBB. Neither LBBB nor RBBB was significantly associated with hypertension, as defined in the text. When the common, uncomplicated RBBB was regarded as a separate entity, the prevalences of hypertension and cardiomegaly were indistinguishable from those of a control group with normal electrocardiograms. The RBBB variant, regarded as a possible manifestation of left ventricular disease secondary to hypertrophy or myocardial infarction, was found to be frequently associated with hypertension, cardiomegaly, and the need for digitalis therapy. RBBB with left axis deviation, regarded as a complication of the common RBBB due to left ventricular hypertrophy or myocardial infarction, was similarly associated with a high prevalence of cardiovascular disease. None of the 38 cases of RBBB fulfilled the criteria for classic RBBB. It is suggested, therefore, that the chronic uncomplicated RBBB in the adult may indeed bear a less ominous portent than has previously been ascribed to it. This is suggested only in relation to the parameters evaluated, however; prospective evaluation is clearly necessary to assess the validity of such an inference.