Effects of external periodic perturbations on short-term heart rate variability in healthy subjects and ischemic heart disease patients

Aims: To characterise the frequency response of short-term heart rate variability to external periodic perturbations in healthy and ischemic heart disease subjects. Methods: Eleven healthy men and 11 ischemic heart disease patients were enrolled in this study. The frequency response of heart rate variability was assessed during periodic eyes opening test and controlled breathing at frequencies ranging from 0.08 to 0.25 Hz using autoregressive spectral analysis. Results: In subjects of both groups the mean heart rate and blood pressure were unchanged across experimental sessions. In healthy subjects eyes opening at rate of 8 and 6 times/min (0.12 and 0.10 Hz) evoked high-power peaks (P<0.05) at the same frequencies in the R–R power spectrum. The largest frequency response of heart rate variability was seen during eyes opening at 0.1 Hz (P<0.05). Ischemic heart disease patients failed to respond to periodic eyes opening with any changes in heart rate variability. During controlled breathing healthy subjects showed the highest heart rate variability frequency responses when breath frequency was 0.1 Hz (P<0.05). Comparatively, patients with ischemic heart disease had reduced frequency responses of heart rate variability at all breath rates and its magnitude did not depend on the perturbation frequency. Conclusions: Our results demonstrate that the frequency response of short-term heart rate variability to external periodic perturbations is dependent on the perturbation frequency and the presence disease processes in the cardiovascular system.