Cardiology. Reassessment of left bundle-branch block

In a population of patients who seek medical attention because of possible cardiac symptoms and are found to have left bundle-branch block, the vast majority have obvious cardiac disease, usually atherosclerotic or hypertensive. The prognosis in this group is poor and is a function of the underlying heart disease and not the conduction defect per se. The situation is distinctly different in a population of asymptomatic subjects whose conduction defect is discovered during routine electrocardiographic screening. In some of these individuals the conduction defect reflects previously unrecognized cardiac disease, but the majority have no other evidence of cardiovascular abnormality and approximately two thirds continue to do well over a relatively long follow-up period. It seems reasonable to reassure such patients regarding their prognosis, while at the same time maintaining careful follow-up. In situations where there is an important need to know for certain whether an individual has underlying cardiac disease, cardiac catheterization is indicated and should include coronary arteriography and hemodynamic measurements during exercise.