A Mortality Study in Bundle Branch Block

BUNDLE branch block has long been regarded as an ominous electrocardiographic sign. Numerous instances have been reported of prolonged survival of subjects with bundle branch block, and several studies have indicated that survival in the presence of this abnormality is considerably longer than was originally believed. These studies, however, have varied widely in the number of subjects followed, the time interval over which they were followed and the statistical methods employed in calculating the results obtained.1They have in common the fact that they were derived from patient records from hospitals, outpatient departments and private practices. In view of the fact that no mortality study has as yet been published on a group of persons not under medical care at the time of discovery of the lesion, it was felt worth while to review the accumulated electrocardiographic records of the Equitable Life Assurance Society of the United States for