The muscle hypothesis: a model of chronic heart failure appropriate for osteopathic medicine.

Chronic heart failure is one of the most serious medical problems in the United States, affecting some 4 million persons. In spite of its common occurrence, and comprehensive literature regarding this condition, no unifying hypothesis has been accepted to explain the signs and symptoms of chronic heart failure. The cardiocirculatory and neurohormonal models place an emphasis on left ventricular ejection fraction and cardiac output and do not provide appropriate explanations for the symptoms of breathlessness and fatigue. The muscle hypothesis supplements these conventional models. It proposes that abnormal skeletal muscle in heart failure results in activation of muscle ergoreceptors, leading to an increase in ventilation and sensation of breathlessness, the perception of fatigue, and sympathetic activation. At least one fourth of patients with chronic heart failure are limited by skeletal muscle abnormalities rather than cardiac output. Cardiac rehabilitation exercise can lead to an increase in exercise capacity that is superior to that gained from digitalis or angiotensin-converting enzyme inhibitors. Exercise tends to reverse the skeletal muscle myopathy of chronic heart failure and reduces the abnormal ergoreflex. Other interventions that have been shown to have a favorable outcome include localized muscle group training, respiratory muscle training, and dietary approaches. The possibility that osteopathic manipulative treatment might be of benefit is an attractive, but untested, possibility.