A meta-analysis of the effect of exercise training on left ventricular remodeling in heart failure patients

A hallmark of heart failure is a reduced ability to perform aerobic exercise. Indeed, the inability to perform exercise without discomfort may be one of the first symptoms experienced by patients with heart failure. For generations, this limitation in exercise capacity was used to define the management paradigm: restriction of physical activity and exercise training in patients with heart failure. Then, during the 1990s, 15 controlled trials of exercise training in heart failure demonstrated improvements in exercise capacity, as measured by peak V0₂. Ten trials, during roughly the same period, also reported improvements in clinical and biological parameters other than VO₂ among heart failure patients, induding improved peak workload, exercise duration, and parameters of submaximal exercise performance. In addition, quality of life (QOL) improved in parallel to improvements in exercise capacity. In 2004, a Cochrane systematic review of 29 trials concluded that training improves exercise capacity and QOL in patients with mild to moderate heart failure. However, the trials provided no information relating to the effect of exercise training on clinical outcomes. Moreover, the authors noted, their conclusions were based on "small-scale trials in patients who are unrepresentative of the total population of patients with heart failure." Other groups (more severe patients, the elderly, and women) may also benefit, but available data were simply too limited. In late 2006, a meta-analysis identified 35 studies published between 1991 and 2004 and the combined results were similar to those of the Cochrane analysis. As for the risks of activity in this population, an evaluation of 21 exercise training studies conducted in a total of 467 patients with chronic heart failure showed a low adverse event rate for either supervised or home-based rehabilitation programs. Subsequently, the American College of Cardiology/American Heart Association (ACC/AHA) guidelines formally recognized exercise training for patients with current or prior symptoms of heart failure with reduced systolic function, giving it a class I recommendation. The guidelines state that exercise training can lessen symptoms, increase exercise capacity, and improve QOL. Moreover, the improvement is "comparable to that achieved with pharmacological interventions" and is in addition to the benefits of angiotensin-converting enzyme (ACE) inhibitors and betablockers. Also, exercise training is associated with an enhancement of endothelium-dependent peripheral vasodilation and skeletal muscle metabolism. The ACC/AHA guidelines conclude: Exercise training should be considered for all stable outpatients with chronic heart failure who are able to participate in the protocols needed to produce physical conditioning. Exercise training should be used in conjunction with drug therapy.