Optimizing exercise training for subgroups of patients with chronic heart failure.

Patients with heart failure and severe left ventricular dysfunction are limited in their ability to tolerate exercise. Recent research has demonstrated that it is not a restricted cardiac output which limits exercise but an abnormality in the performance of a more peripheral component in the pathway of delivery of oxygen to the exercising muscles. Deficiencies in peripheral blood flow and skeletal muscle function and an exaggerated sensitivity to exercise-derived metabolic signals lead to early and profound exercise-induced fatigue and dyspnoea, the mechanisms of which we are only now beginning to understand. These findings raise the possibility of improving exercise tolerance by peripherally acting therapies such as exercise training of skeletal muscles in left ventricular dysfunction and chronic heart failure. Training has been shown to improve exercise tolerance at least as much as angiotensin-converting enzyme inhibitors in these syndromes; additionally, training improves ventilatory control, skeletal muscle metabolism and autonomic nervous system activity. As yet, the most appropriate forms of exercise therapy are not known nor is how best to choose the most suitable patients for this form of treatment. There is evidence that patients with at least moderate, and possibly severe but stable, heart failure can benefit from exercise rehabilitation, provided it is tailored to the capacity of the patient and certain safety considerations are taken into account.