Chronic heart failure and skeletal muscle myopathy: Effects of exercise training

Chronic heart failure (CHF) is a clinical syndrome in which left ventricular impairment produces secondary changes in other organ systems, leading to debilitating symptoms such as muscular fatigue, dyspnea and reduced exercise capacity. It was previously thought that the exercise limitation was due to cardiac dysfunction. However functional, morphologic and metabolic abnormalities of the skeletal muscle are now recognized to be the basic mechanisms for exercise intolerance. There is increasing evidence that neurohormonal, immune and metabolic abnormalities may play an important role in the progression of the syndrome, leading to catabolic/anabolic imbalance that is likely to be responsible for the development of the wasting process. The pathophysiological mechanisms involved in the wasting process induce morphologic and functional impairment in different body systems. Skeletal muscle is an organ that develops a special "myopathy" that is associated with functional, metabolic and structural changes. The functional capacity of CHF patients depends on both central hemodynamic parameters and peripherally mediated oxygen utilization. However, the potential to increase cardiac output is limited by heart failure. Exercise training induces peripheral adaptations in CHF patients and appears to be a suitable intervention to enhance their functional capacity. Exercise training improves the hemodynamic profile, functional capacity, quality of life and morbidity of CHF patients, and a recent meta-analysis of randomized controlled trials indicated that exercise improved survival. Moreover, exercise induces peripheral adaptations improving skeletal muscle and endothelial dysfunction. This knowledge about the beneficial effects of exercise training has changed the treatment of CHF patients. Patients are now advised to exercise regularly and to participate in cardiac rehabilitation programs.