Endocardial fibrosis. Detection by cardiac pacing.

ENDOCARDIAL FIBROSIS occurs in diverse diseases. An infantile form appears to reflect an unexplained congenital derangement in which a thick layer of collagen and elastin lines the left ventricular cavity.' Sporadic instances noted in the adolescent have also been presumed to be of congenital origin.2 A poorly understood cause of heart failure occurs frequently in Uganda and South Africa in association with extensive endocardial fibrosis.3 Endocardial fibrosis also occurs as one of the pathological changes of subendocardial myocardial infarction, and, in the right ventricle, in the carcinoid syndrome. Localized areas of endocardial fibrosis have been noted in association with sustained hypertension and with valvular stenosis and regurgitation.4 Despite the frequent occurrence of this abnormality in many types of heart disease, proof of endocardial fibrosis has not been possible except