Exercise Training in Heart Failure: When?

Abstract

The cardinal symptoms limiting exercise in patients with chronic heart failure (CHF) are fatigue and/or dyspnea. Conventionally, it has been taught that both are the direct result of reduced cardiac output. Fatigue was thought to arise from the impaired cardiac pumping capacity delivering inadequate amounts of oxygen to the exercising muscle so that there is a buildup of products of anaerobic metabolism within the muscle. Dyspnea was thought to arise from the effects of impaired cardiac function increasing left atrial pressures and thereby pulmonary venous pressures and producing pulmonary congestion. This explanation formed the basis of the subdivision of heart failure into forward and backward heart failure symptoms. Several recent lines of evidence, however, have questioned these assumptions. Persistent vasoconstrictor drive, endothelial dysfunction, and a wide array of structural and functional abnormalities of skeletal muscle have all been described as being better able to explain fatigue in CHF [1]. Dyspnea appears to be related to enhanced ventilatory effort rather than pulmonary congestion in most well-treated nonedematous patients [2]. This may in particular be related to augmented re_ex control systems such as the arterial chemore_exes and the muscle ergore_exes (metabore_exes) [3,4]. Furthermore, even the differentiation between fatigue and dyspnea may be arti~cial in many patients, since as either symptom can occur with subtle alterations in the exercise testing procedure, and in many patients a sensation of exhaustion may have elements of both [5]. The cause of the perceptions of fatigue and dyspnea may arise from similar sensory afferents from the abnormal muscle of chronic heart failure patients. For all these reasons, attention has turned to the role of peripheral manifestations of chronic heart failure and in particular to whether exercise training programs could reverse some of these abnormalities and thereby improve the symptoms and exercise tolerance of the patient with CHF. This special issue reviews some of the evidence for a role for exercise training, concentrating on particular aspects of the use of training as a therapeutic option in the clinical setting. This article will concentrate on the timing of exercise in the management of patients with left ventricular dysfunction and chronic heart failure throughout their clinical course. Bene~cial Effects of Exercise Training in Cardiac Patients