Toward chronocardiologic and chronomic insights: dynamics of heart rate associated with head-up tilting

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• 作者：Kubo ; Yutaka ; Murakami ; Shogo ; Matsuoka ; Osamu ; Hotta ; Norihiro ; Oinuma ; Sachiko ; Shinagawa ; Makoto ; et. al.
• 关键词：Head-up tilting ; Heart rate variability ; Non-linear analysis ; Fractals
• 刊名：Biomedicine and Pharmacotherapy
• 出版年：2003
• 出版时间：October, 2003
• 年：2003
• 卷：57
• 期：Supplement 1
• 页码：110-115
• 全文大小：139 K

文摘

As a step towards investigating the chronome (i.e. the inferential endpoints of chaos, trends and rhythms) of heart rate (HR) variability (HRV), we investigated whether the fractality or complexity of HRV is affected by a head-up tilting (HUT) test in the morning after an overnight fast. Spectral and non-linear analyses of HR were performed on data gathered during an 80° passive HUT test in 15 men and 28 women 32.8 ± 11.5 years of age. The non-linear endpoints included the scaling exponents α₁ (<11 beats) and α₂ (>11 beats), which indicate fractal properties, calculated with detrended fluctuation analysis, and the approximate entropy (ApEn), a measure of overall complexity. Passive HUT increased α₁ (from 0.986 ± 0.217 to 1.370 ± 0.185; P = 0.0001), but did not alter α₂ (from 0.925 ± 0.110 to 0.958 ± 0.130; P = 0.19). A slight but statistically significant decrease in ApEn was seen during HUT (from 1.114 ± 0.131 to 1.013 ± 0.197; P = 0.002). In the tilt-up position, there was a statistically significant negative correlation between α₁ and ApEn (r = –0.490; P < 0.05). In both the supine and the tilt-up position, α₁ was correlated weakly with HF (r = –0.343 and r = –0.322, respectively), and strongly with LF/HF (r = 0.557 and r = 0.795), respectively. There was also a negative correlation between ApEn and LF/HF (r = –0.406 and r = –0.357, respectively). α₂ did not correlate with any spectral or non-linear measures of HRV. Short-term fractal properties and complexity of HR were lowered with orthostatic stress. Alterations of the autonomic activities could be partly responsible for these changes and await extension of such studies to assess the broad spectral element of HRV, that includes, with components of ~3.6 and ~10.5 s, cycles with very much lower frequencies, along the scales of hours and even years, that critically modulate the mislabeled (only relatively high- and low-frequency) components in the range of seconds or minutes.