ESSENTIALS OF ECHOCARDIOGRAPHY # 3 Heart Muscle Disease

Chronic elevation of myocardial stress due to pressure overload, as in hypertension or aortic stenosis, causes cardiac muscle to hypertrophy with a resulting increase in myocardial thickness. There is normally little or no change in overall cardiac size, so the wall thickening occurs at the expense of the cavity (Fig. 1 and Fig. 2). In the case of mitral regurgitation, on the other hand, ventricular volume increases with little or no change in maximum developed pressure; wall thickness does not alter significantly but total myocardial mass increases because of the ventricular enlargement. Except in the case of neonates, increase of mass does not alter the number of myocardial cells; the primary histological changes are intracellular, involving changes in the number and arrangement of the sarcomeres. In chronic cases widespread interstitial fibrosis occurs.