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Controlled trial of physical training in chronic heart failure. Exercise performance, hemodynamics, ventilation, and autonomic function.
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1992
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In chronic heart failure, secondary abnormalities and exercise limitation are thought to stem from physical deconditioning, yet no prospective controlled study had examined training effects on hemodynamics and autonomic function. The study employed an 8‑week controlled crossover exercise training protocol in 17 men with moderate‑to‑severe CHF, measuring exercise tolerance and peak oxygen uptake against controls. Exercise training raised cardiac output at submaximal and peak exercise, lowered systemic vascular resistance and minute ventilation, and shifted sympathovagal balance toward enhanced vagal activity, yielding significant functional gains in CHF patients.
Many secondary abnormalities in chronic heart failure (CHF) may reflect physical deconditioning. There has been no prospective, controlled study of the effects of physical training on hemodynamics and autonomic function in CHF.In a controlled crossover trial of 8 weeks of exercise training, 17 men with stable moderate to severe CHF (age, 61.8 +/- 1.5 years; left ventricular ejection fraction, 19.6 +/- 2.3%), increased exercise tolerance (13.9 +/- 1.0 to 16.5 +/- 1.0 minutes, p less than 0.001), and peak oxygen uptake (13.2 +/- 0.9 to 15.6 +/- 1.0 ml/kg/min, p less than 0.01) significantly compared with controls. Training increased cardiac output at submaximal (5.9-6.7 l/min, p less than 0.05) and peak exercise (6.3-7.1 l/min, p less than 0.05), with a significant reduction in systemic vascular resistance. Training reduced minute ventilation and the slope relating minute ventilation to carbon dioxide production (-10.5%, p less than 0.05). Sympathovagal balance was altered by physical training when assessed by three methods: 1) RR variability (+19.2%, p less than 0.05); 2) autoregressive power spectral analysis of the resting ECG divided into low-frequency (-21.2%, p less than 0.01) and high-frequency (+51.3%, p less than 0.05) components; and 3) whole-body radiolabeled norepinephrine spillover (-16%, p less than 0.05). These measurements all showed a significant shift away from sympathetic toward enhanced vagal activity after training.Carefully selected patients with moderate to severe CHF can achieve significant, worthwhile improvements with exercise training. Physical deconditioning may be partly responsible for some of the associated abnormalities and exercise limitation of CHF, including abnormalities in autonomic balance.