Heart block and sudden death associated with fibrosis of the conduction system at the margin of a ventricular septal defect.

Isolated ventricular septal defects in clinically well patients are not generally thought to cause sudden death. We document a case in which heart block, with sudden collapse and death, is related to the presence of fibrous interruption of the conduction system of the heart due to progressive fibrous closure of a small ventricular septal defect.