The Role of Exercise Training in Heart Failure
This article discusses the role of exercise in heart failure under two broad categories: A) impairment of exercise capacity, and B) impact of exercise training.
A. Impairment of Exercise Capacity in Heart Failure includes involvement of central circulation, ventilatory system, and periphery (includes skeletal muscle, endothelium, neurohormal system, and inflammatory response).
1. Central circulation:
a) The measures of resting ventricular function—such as ejection fraction—demonstrate a poor correlation with exercise capacity.
b) An increase in ventricular filling pressures can give rise to secondary pulmonary hypertension, resulting in right ventricular dysfunction.
c) Mitral regurgitation can result if annular dilation or papillary muscle dysfunction is present.
d) A decreased cardiac output at submaximal and peak levels of effort is a result of a reduction in stroke volume coupled with a lower heart rate reserve.
e) Abnormalities of left ventricular (LV) diastolic function on Doppler studies (including the ratio of early diastolic peak transmitral velocity to myocardial tissue velocity and ratio of early to late transmitral diastolic velocity) are independent predictors of diminished exercise capacity in those with preserved LV function.
2. Ventilatory system: Ventilatory abnormalities do not limit peak exercise performance in most patients.
3. The Periphery
a) Skeletal muscle: With maximal exercise testing, the HF patient typically reports leg fatigue. Skeletal muscle biopsies performed on HF patients and control subjects matched for age and peak VO2 showed decreased vascular density and oxidative enzyme activity in the HF patients that could not be explained by deconditioning alone.
b) Endothelium: Abnormal endothelial function exists among patients with HF, which can be mitigated by exercise training.
c) Neurohormonal system: Catecholamine levels increase with exercise in HF patients, but it is unclear whether this contributes to exercise intolerance or an indication of advanced disease.
d) Inflammation: Increased inflammatory cytokines in HF may lead to increased muscle catabolism, loss of muscle protein, and apoptosis in skeletal myotubes associated with a decrease in maximal exercise capacity.
B. Impact of Exercise Training
1. Exercise training is a valuable adjunct in the treatment of stable HF patients, and is recommended by the American College of Cardiology and the American Heart Association at a Class 1 Level. Both aerobic exercise and resistance training are beneficial. Aerobic training results in increased exercise capacity, lower heart rate response to submaximal exercise, improved diastolic function, improved endothelial function, increased skeletal muscle oxidative capacity, enhanced vagal tone and lower sympathetic tone, reduced inflammatory cytokines, lower all-cause mortality or hospital stay, and improved overall health status. Resistance training increases muscle strength and endurance.
2. Exercise training results in improvements of 18-25% in peak VO2 and 18-34% in peak exercise duration, subjective symptoms, functional class, and quality of life measures.
3. The HF-ACTION (Heart Failure–A Controlled Trial Investigating Outcomes of exercise TraiNing) reported a nonsignificant reduction in the primary combined endpoint of all-cause mortality or hospital stay (hazard ratio, 0.93; p = 0.13). However, these findings must be interpreted in the background of the generally low rate of adherence to exercise in the training group, whereby only 30% of subjects exercised at or above the target number of minutes/week. Also, it is estimated that at least 8% of the control patients admitted to exercising throughout the entire study period.
In summary, the authors of the article opine that the preponderance of evidence supports the benefits and safety of an exercise training program for the stable, systolic HF patient who is receiving optimal medical treatment. Benefits include improvement in functional capacity, a decrease in symptoms of dyspnea and fatigue, and self-reported quality-of-life benefits.
Clinical Topics: Diabetes and Cardiometabolic Disease, Heart Failure and Cardiomyopathies, Prevention, Pulmonary Hypertension and Venous Thromboembolism, Sports and Exercise Cardiology, Valvular Heart Disease, Novel Agents, Acute Heart Failure, Pulmonary Hypertension, Exercise, Mitral Regurgitation
Keywords: Inflammation, Apoptosis, Cytokines, Mitral Valve Insufficiency, Biopsy, Exercise, Dyspnea, Heart Rate, Leg, Ventricular Dysfunction, Right, Resistance Training, Endothelium, Muscle Proteins, Muscle Strength, Hypertension, Pulmonary, Heart Failure, Stroke Volume, Ventricular Function, Muscle Fibers, Skeletal, Health Status, United States, Papillary Muscles
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