Skeletal muscle blood flow, metabolism and morphology in chronic congestive heart failure and effects of short- and long-term angiotensin-converting enzyme inhibition.

Blood flow to skeletal muscle during exercise is limited in patients with chronic congestive heart failure compared with normal persons. This may, in part, be attributed to the inability of the vessels to dilate adequately. In addition, an abnormal skeletal muscle metabolism with oxidative capacity can be demonstrated in patients with chronic congestive heart failure. The latter may partially explain why vasodilators and inotropes that improve central hemodynamics, global leg perfusion or skeletal muscle blood flow during exercise do not increase oxygen uptake by working muscle after acute drug administration. Furthermore, increases in blood flow to skeletal muscle may be redistributed to inactive or less oxygen-dependent muscle fibers. Although acute angiotensin-converting enzyme inhibition usually neither exerts substantial improvement in exercise hemodynamics nor interferes with leg perfusion during exercise, skeletal muscle blood flow and oxygen uptake gradually increases with long-term angiotensin-converting enzyme therapy, leading to improved systemic oxygen consumption and exercise tolerance. Several factors, such as reduction in plasma and vascular angiotensin II and sympathetic nervous activity, increased prostaglandin levels and renal function may contribute to this beneficial long-term effect.