[Assessment of the state of myocardial contractility based on analysis of heart rate variability during exercise tests]

To elucidate stability of 0.1 Hz component of heart rate variability (HRV) spectrum in patients with different state of myocardial contractile function during bicycle exercise tests under controlled breathing with 10 sec period.

Male patients with class II-III effort angina and either abnormal myocardial contractile function (n=45, age 51.0+/-2.5 years, left ventricular ejection fraction <50%), or without disturbances of myocardial contractility (n=35, age 52+/-6 years, ejection fraction > 60%).

All patients underwent Doppler echocardiography and submaximal exercise tests with initial loads 25 W. Registration of series of RR-intervals was done during controlled breathing with 10 sec periods (0.1 Hz) for 5 min at rest and exercise (25 W work load). Depth and balance of phases of controlled breathing were similar to those of spontaneous breathing. Analysis of the heart rate variability was made on the basis of auto-regression algorithm.

Stability of 0.1 Hz component of the heart rate variability spectrum to low-level exercise correlated with the severity of depression of myocardial contractility.