Analysis of the Relationship between Amplitude Modulation of Low Frequency Heart Rate Variability and Blood Pressure Variability

Analysis of the Relationship between Amplitude Modulation of Low Frequency Heart Rate Variability and Blood Pressure Variability

Yui Sugimoto, Ken Kiyono, Kohzoh Yoshino
Vol. 8 (2019) p.78-84

It has been reported that increased intermittent non-Gaussian fluctuations in the instantaneous amplitude of low-frequency heart rate variability (LF-HRV) are related to high mortality risk in cardiac patients. However, little is known about the physiological origin of the amplitude modulation of LF-HRV. The purpose of this study was to clarify the relationship between amplitude modulation of LF-HRV and that of low-frequency blood pressure variability (LF-BPV). Eight normal male subjects performed movie-watching and calculation tasks in a sitting position for 40 min each while electrocardiogram and continuous blood pressure waveforms were recorded. From these signals, we calculated the instantaneous amplitude of the LF-band RR interval (RRILFamp) signal and that of the LF-band systolic blood pressure (SBP) signal (SBPLFamp) via band-pass filter and Hilbert transform. All subjects exhibited significant and relatively high positive correlation coefficients between RRILFamp and SBPLFamp in both tasks (mean Pearson correlation coefficient > 0.45). Mean coherence in the 0.01–0.05 Hz band between RRILFamp and SBPLFamp was also significant in all but one subject (mean coherence > 0.42). These results indicate a relatively high positive correlation between the amplitude modulation of LF-HRV and that of LF-BPV. We calculated the peak time lags of the cross correlation between RRILFamp and SBPLFamp in the 0.01–0.05 Hz band. A negative peak time lag implies that the amplitude modulation of LF-HRV precedes that of LF-BPV. All subjects exhibited negative peak time lag in the movie-watching task. All but one subject exhibited negative or zero peak time lag in the calculation task. These results imply that the amplitude modulation of LF-HRV precedes that of LF-BPV in the frequency range of 0.01–0.05 Hz.

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