Effects of exercise training on chronotropic incompetence in patients withheart failure

Objective To describe the effects of exercise training on chronotropic inco mpetence in patients with stable heart failure, as measured by their inabil ity to achieve a peak exercise heart rate greater than 85% of maximum. Background Exercise intolerance and chronotropic incompetence are character istic of patients with heart failure. Exercise training improves exercise c apacity in these patients; however, to what extent reversal of chronotropic incompetence contributes to such a response remains uncertain. Methods Fifty-one patients undergoing standard medical therapy were randoml y assigned to a 24-week exercise training program or a no exercise control group. Twenty-one of 26 patients assigned to the exercise group and 22 of 2 5 control patients completed the study. Peak oxygen consumption, resting an d exercise plasma norepinephrine level, and quality of life (Living With He art Failure Questionnaire) were assessed. Results A significant (P <.05) increase in peak heart rate was observed in the exercise group (9 +/- 3 beats/min) when compared with the central group (1 +/- 3 beats/min). Among exercise-trained patients with chronotropic inc ompetence at baseline (n = 14), the increase in peak heart rate at week 24 was 12 +/- 3 beats/min. Peak oxygen consumption was significantly (P <.05) increased in the exercise group (204 +/- 57 mL/min) versus the control grou p (72 +/- 33 mL/min). Health-related quality of life was not significantly changed with exercise training. Twenty-four weeks of exercise training indu ced a greater (P <.05) reduction in plasma norepinephrine at rest and durin g exercise in patients with a nonischemic cardiomyopathy versus those with ischemic cardiomyopathy. Conclusions Exercise training results in on increase in peak heart rate and partial reversal of chronotropic incompetence among patients with stable h eart failure. These responses contribute, in part, to the exercise training -induced increase in exercise capacity that occurs in these patients.