IMPORTANCE OF TOTAL LEG MUSCLE MASS FOR EXERCISE INTOLERANCE IN CHRONIC HEART-FAILURE

Patients with chronic heart failure symptoms tend to avoid voluntary e ffort and are thus subject to physical deconditioning. The presence of symptoms in daily fife is thought to predispose to physical deconditi oning and subsequent skeletal muscle loss. This study was designed to describe the relation among daily physical activities, skeletal muscle loss and exercise capacity in patients with chronic heart failure. We studied 14 patients with severe cardiac dysfunction (left ventricular ejection fraction <40%) and 7 age-matched normal subjects. We measure d total leg muscle mass by dual energy X-ray absorptiometry. The patie nts were divided into 7 asymptomatic and 7 symptomatic individuals usi ng questionnaires for specific physical activities. Peak oxygen uptake and anaerobic threshold were significantly reduced in cardiac patient s as compared with normal subjects. The reduction in exercise capacity was greater in the symptomatic patients than in asymptomatic patients . Leg muscle mass was significantly reduced (-17%) in the symptomatic patients, while it remained normal in the asymptomatic patients. Oxyge n uptake in unit muscle mass at the level of anaerobic threshold and a t peak exercise was decreased in both the asymptomatic (-21% and -21%, respectively) and symptomatic patients (-27% and -30%, respectively) but the difference between these two groups was not significant. In th e asymptomatic patients, the reduced exercise capacity was accounted f or primarily by muscle mass-independent factors such as an impaired nu tritive blood flow to exercising muscles or metabolic abnormalities wi thin the muscle cell. In the symptomatic patients, the marked reductio n in exercise tolerance was attributable to a decrease in leg muscle m ass and to hemodynamic or metabolic abnormalities. We conclude that th e loss of leg muscle mass plays an important role in exercise intolera nce in patients who are prone to physical deconditioning as a result o f symptomatic heart failure.