Introduction: exercise in patients with chronic heart failure

The treatment of patients with chronic heart failure represents a dynamic clinical responsibility that combines the use of agents which date back decades (if not centuries) with more contemporary medical and device therapies, all aimed at preventing death, lessening hospitalizations, and improving both physical function and quality of life. Yet, the search for new agents or treatments aimed at further improving upon these endpoints continues at an unyielding pace, because the clinical, public health, and economic burdens imposed today by heart failure are uncompromising and continue to rise. The above not withstanding, over the past 20 years there has been one novel therapy for patients with chronic heart failure that has transitioned from once being considered unsafe and ineffective to one that is now actively employed in many patients. This therapy is regular exercise training. After the initial landmark trials conducted by Lee et al. [1], Sullivan et al. [2], and Coats et al. [3], dozens of single site randomized trials followed and demonstrated the many benefits of regular exercise in the care of patients with chromic heart failure. And as is nicely pointed out in the articles in this special issue of Heart Failure Reviews, the benefits of regular exercise are widespread, in that not only have we observed the partial reversal of the abnormal central and systemic pathophysiology that define the disease, but the benefits of regular exercise may include improved clinical outcomes as well. In this special issue, six articles review the effects of aerobic and resistance training on patient safety and clinical outcomes; cardiac, skeletal muscle, and autonomic function; and the inflammatory response. Two other papers complement the above articles by describing how to safely prescribe exercise and how to address the complex behavioral issues that confound long-term exercise compliance. It is our hope that this assembled body of works provides both the novice and the experienced clinician involved in the care of patients with heart failure with the essential information needed to determine who might benefit from exercise, what should be expected, and how to go about safely prescribing exercise training. Although we would like to think that the current research has sufficiently answered the important questions concerning the safety and efficacy of exercise training in patients with chronic heart failure, a critical review of the topic suggests that this is not the case. Fortunately, the multi-site HF-ACTION (Heart Failure—A Controlled Trial Investigating Outcomes of Exercise Training) trial that began in 2002 is nearly completed and will report its findings in the fall of 2008 [4]. In this trial, over 2,300 patients have been randomized to usual care versus usual care plus at least 1 year of initially supervised cardiac rehabilitation followed by home-based exercise. If HFACTION finds that long-term exercise improves clinical outcomes, then additional research will be needed to address how best to optimize compliance so that its therapeutic benefits can be derived by the greatest number of eligible patients. Alternatively, if the HF-ACTION shows no improvement in all-cause mortality and hospitalizations with exercise training, as long as exercise is shown to be safe it will likely continue to be recommended for selected patients because of its well established effect on lessening exercise intolerance and improving symptoms and quality