Chronic heart failure. The relationship between increased activity of skeletal muscle ergoreceptors and reduced exercise tolerance

Abstract

Background: In chronic heart failure (CHF), skeletal muscle abnormalities may lead to the overactivation of ergoreceptors which in turn may cause sympathetic overactivation and increased ventilatory response to exercise.

Aim: To assess ergoreceptor reflex response to exercise and to evaluate whether ergoreceptor overactivity is related to the progression of CHF.

Methods: In 69 patients with CHF (66 males, mean age 62.7+/-11.6 years, NYHA class I/II/III/IV - 11/32/24/2 patients, respectively) and 24 controls without CHF (22 males, mean age 59+/-4.6 years) the ergoreflex contribution to the ventilatory and haemodynamic responses to exercise was evaluated. Moreover, in 13 patients with CHF, reproducibility of the measurements was assessed by repeating the test 1 to 7 days later.

Results: Enhanced ergoreflex effects on ventilation (1.9+/-1.6 vs 0.14+/-0.7 l/min, p<0.05) and systolic blood pressure (19.2+/-14.9 vs 6.1+/-5.9 mmHg, p<0.05) were found in patients with CHF compared with control subjects. Ergoreceptor overactivity was associated with a worse symptomatic state (NYHA class I vs II vs III, IV: 0.9 vs 1.5 vs 2.9 l/min, p<0.05) and lower exercise tolerance (peak V0(2): r=-0.51, p<0.0001; VE/VC0(2): r=0.50, p<0.0001). The mean values of the ergoreceptor reflex did not differ significantly between the two tests (t=1.5, p=0.14; variability coefficient = 21.5%).

Conclusions: In CHF, overactivation of the ergoreflex is associated with the progression of the syndrome and may be responsible for reduced exercise tolerance. Reproducibility of ergoreflex measurements is satisfactory.