Background. Low-frequency (LF) oscillations in heart rate (HR) are largely an index of baroreflex gain. Controlled 0.1 Hz breathing maybe used as input stimuli for study of this resonance phenomenon in LF oscillations in HR. The aim of this study was the investigation of the dynamic characteristics of LF oscillations in the heart rate (HR) of chronic heart failure (CHF) patients during bicycle exercise (BE) tests, under 0.1 Hz controlled breathing. Methods. Forty five male patients aged 50±3 years with left ventricle ejection fraction (EF) <50% and 35 male patients aged 52±6 years with EF>50% participated in the study. BE tests were performed for all participants. Five-minute recording of R-R intervals was performed first in sedentary posture and in 25 W load stage of BE test. The frequency estimates of heart rate variability in LF spectrum bands were obtained. Results. Under the load rising till 25 W in CHF patients with EF<50%, consequent depression of LF band power was observed 2-3 times in comparison with the relaxed condition. There was no similar significant expressed dynamic in the group with EF>50%. Conclusions. The stability of LF oscillations in HR to low-intensity loads depends from the severity of myocardial contractility damage. The power dynamic of 0.1 Hz component of the heart rate variability spectrum may be considered an independent index of dynamic stability of the heart autonomic control in CHF patients.
Health Science Journal 2013; 7(1): 90-98.