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The benefits of moderate exercise appear to outweigh the risks
The hallmark symptoms of chronic heart failure (CHF) are fatigue and breathlessness, leading to impaired quality of life and capacity for activities of daily living (ADLs). Exercise training has the potential to delay the onset of fatigue and breathlessness, not just in patients with CHF, but in all people who exercise regularly. However, cardiologists have been concerned with recommending exercise to their patients with CHF, owing to perceptions that habitual exercise training may accelerate the disease process via cardiac hypertrophy and remodelling, deterioration in central haemodynamics and neurohormonal overactivity. All of these have strong associations with increased morbidity and mortality in these patients. A further concern has been that of sudden death from exercise‐induced arrhythmias and, to a lesser extent, severe perturbations in blood pressure. Exercise training in patients with CHF is a relatively recent development, and studies to date have generally been limited to clinically stable, younger (<65 years) and less complicated cases.1 Very few women have been studied. The mortality outcome data so far are limited to less than 20 studies of a total of approximately 1000 individuals. The purpose of this Leader is to provide an overview of the benefits, or otherwise, of exercise training for people with stable CHF in terms of its intermediate clinical influences on central haemodynamics, intracardiac volumes and pressures, and autonomic balance, and on their longer‐term associations with symptom progression and mortality.
There have been no reports of sudden death or the need for cardiac life support during supervised exercise in clinical trials of exercise training in patients with heart failure (HF), although this may be partly attributed to the relatively low number of patient‐hours accumulated to date, and the closely controlled conditions of these trials, including biases in volunteer inclusion. There is a small but growing body of evidence showing lower mortality in patients with CHF who exercise, compared with inactive controls. A meta‐analysis of nine randomised clinical trials for a total of 801 patients2 involved in exercise training yielded a number needed to treat of 17 patients to prevent one death every 2 years. This compares favourably with a number needed to treat of 19 for the first‐line HF drug class of ACE inhibitors,3 underscoring the clinical significance of exercise for patients with HF. The relative risk ratio of mortality for exercising patients to that for inactive controls was 0.65 (95% CI of 0.42 to 0.92).2 Larger‐scale mortality outcome studies are currently underway to expand this limited evidence base.4
Six months of aerobic exercise training at moderate intensities (60–70% of VO2peak) and volumes (150 min per week) were associated with small but significant improvements (falls) in end‐diastolic volume and end‐systolic volume5,6 in patients with CHF, whereas these volumes increased in the inactive CHF volunteers, indicating that moderate‐intensity exercise training for up to 6 months is safe and may also promote reverse remodelling of the left ventricle in CHF. Exercise training in CHF improves cardiac vagal influence,7,8 and this may protect the heart during acute exercise from arrhythmias, and during chronic exercise by retarding the development of cardiomegaly.9 Intense exercise regimens (both aerobic and strength) are associated with sharp increases in platelet reactivity, whereas moderate‐intensity training is associated with relatively counterbalanced stimuli to the thrombogenic and fibrinolytic systems. Therefore, patients with CHF, particularly those with (a history of) atrial fibrillation, unstable atherosclerotic plaque or shortly after coronary artery stenting, should avoid high‐intensity exercise.10 For many other reasons, high‐intensity exercise should not normally be included in exercise programmes for patients with CHF. Pragmatically, a sedentary lifestyle often contributes to the development of CHF, with many individuals harbouring long‐term aversions to exercise. It is more likely that they will accept, and then enthusiastically adopt, healthful enduring exercise if that exercise is at relatively comfortable intensities. As a guide, moderate intensity exercise approximates to 60–70% of VO2peak (aerobic) and 60–70% of 3RM (strength: maximum load that can be lifted for 3, but not 4, repetitions). CHF is characterised by a myopathy syndrome, manifested by a loss of strength in mild cases through to cachexia in severe cases. The goal for including resistance (strength) training for patients with CHF is to (partially) reverse the deficits of muscle wasting and weakness. An associated goal is to improve the capacity for ADLs and quality of life, since most ADLs involve strength more than endurance. Moderate‐intensity strength training also improves aerobic capacity,8 partly via improvements to skeletal muscle mitochondrial ATP production rates.11 High‐intensity strength training may engender valsalva effects, with central haemodynamic compromise, and so moderate‐intensity training is preferred. The goals for including aerobic training include benefits to endothelial integrity and function (anti‐inflammatory, anti‐atherogenic, anti‐thrombogenic), decreasing fat mass in those who need to do so, improving mood and alleviating depression and improving aerobic capacity. Although the latter is strongly linked to improved mortality outcomes,12 the results of large mortality outcome training studies are awaited.
Combinations of moderate‐intensity aerobic and strength training programmes for patients with CHF improve aerobic capacity, skeletal muscle structure and function, peripheral blood flow, and neurohormonal and endothelial function, with some evidence for improvements in central haemodynamics, cardiac volumes and mortality. Larger studies are underway for morbidity and mortality outcomes, and more studies are needed to examine the safety versus efficacy for patients with more advanced and complicated disease. Patients need to be medically assessed before referral to clinically qualified exercise physiologists who are trained to recognise adverse signs and symptoms and intervene appropriately. The evidence to date points to benefits outweighing the risks for moderate‐intensity exercise training in people living with CHF.
Competing interests: None declared.