VENTILATORY RESPONSE TO EXERCISE CORRELATES WITH IMPAIRED HEART-RATE-VARIABILITY IN PATIENTS WITH CHRONIC CONGESTIVE-HEART-FAILURE

In chronic congestive heart failure (CHF) an overactivity of muscle er goreceptors and peripheral chemoreceptors may lead to an increased ven tilatory response to exercise and contribute to the autonomic imbalanc e. The analysis of heart rate variability (HRV), which is a reliable m ethod of studying autonomic regulations within the cardiovascular syst em, showed depressed HRV indexes in CHF, but predictors of abnormal HR V pattern in CHF remain controversial. Considering a common mechanism involved in generation of bath abnormal ventilation and autonomic dysf unction in CHF, we hypothesized that impaired ventilation may be bette r than other variables of CHF severity in determining HRV parameters. Seventy-two patients with CHF (57 +/- 9 years, ejection fraction: 28 /- 11%) underwent cardiopulmonary exercise testing; the relation betwe en ventilation and carbon dioxide production (VE/VCO2) was used as an index of the ventilatory response to exercise. Time and frequency-doma in measurements of HRV were derived from 24-hour electrocardiographic monitoring. patients had reduced exercise tolerance with abnormal vent ilatory response (peak oxygen consumption [VO(2)max]: 17.8 +/- 5.5 ml/ kg/min, VE/VCO2: 36.0 +/- 9.8). Correlations were found between HRV me asures and etiology, New York Heart Association (NYHA) functional clas s, and VO(2)max, but the strangest relation was observed for VE/VCO2 s lope (r values from -0.33 to -0.65, p <0.01). In the multiple regressi on analysis only VE/VCO2 was found to correlate independently with all HRV measurements. To investigate the role of peripheral chemoreceptor overactivity as the mechanism of autonomic imbalance and the increase d ventilatory response to exercise, we assessed peripheral chemosensit ivity in 22 patients (mean value of peripheral chemosensitivity: 0.62 +/- 0.34 L/min/%SaO(2), significantly higher than in normal controls, mean valve: 0.29 +/- 0.20 L/min/%SaO(2) in our laboratory). The activi ty of the peripheral chemoreflex inversely correlated with all paramet ers of HRV. Increased ventilatory response to exercise correlated with depressed HRV measures in patients with CHF better than other clinica l variables. An important role of the increased peripheral chemosensit ivity in this relation may be relevant, being also a potential link be tween functional severity and sympathovagal imbalance in CHF. (C)1998 by Excerpta Medica, Inc.