Faculté de Médecine d'Angers, UMR CNRS 6214 Inserm 1083 (Biologie Neurovasculaire et Mitochondriale Intégrée), Rue Haute de Reculée, 49045 Angers Cedex, France.
Eur J Appl Physiol. 2013 Sep;113(9):2253-61. doi: 10.1007/s00421-013-2655-2. Epub 2013 May 8.
Heart rate spontaneously fluctuates despite homeostatic regulatory mechanisms to stabilize it. Harmonic and fractal fluctuations have been described. Non-harmonic non-fractal fluctuation has not been studied because it is usually thought that it is caused by apparatus noise. We hypothesized that this fluctuation looking like apparatus noise (that we call "noisy fluctuation") is linked to challenged blood pressure stabilization and not to apparatus noise. We assessed noisy fluctuation by quantifying the small and fastest beat-to-beat fluctuation of RR-interval by means of spectral analysis (Nyquist power of heart rate variability: nyHRV) after filtering out its fractal component. We observed nyHRV in healthy supine subjects and in patients with vasovagal symptoms. We challenged stabilization of blood pressure by upright posture (by means of a head-up tilt table test). Head-up position on the tilt table dramatically decreased nyHRV (0.128 ± 0.063 vs. 0.004 ± 0.002, p < 0.01) in healthy subjects (n = 12). Head-up position also decreased nyHRV in patients without vasovagal symptoms (n = 24; 0.220 ± 0.058 vs. 0.034 ± 0.015, p < 0.05), but not in patients with vasovagal symptoms during a head-up tilt table test (age and sex paired, 0.103 ± 0.041 vs. 0.122 ± 0.069, not significant). Heart rate variability includes a physiological non-harmonic non-fractal noisy fluctuation. This noisy fluctuation indicates low engagement of regulatory mechanisms because it disappears when the cardiovascular system is challenged (upright posture). It also indicates cardiovascular instability because it does not disappear in upright patients before vasovagal syncope, a transient failure of cardiovascular regulation.
尽管存在稳态调节机制来稳定心率，但心率仍会自发波动。已经描述了谐波和分形波动。非谐波非分形波动尚未研究，因为通常认为它是由仪器噪声引起的。我们假设这种看起来像仪器噪声的波动（我们称之为“噪声波动”）与挑战血压稳定有关，而与仪器噪声无关。我们通过对 RR 间期的小而最快的逐拍波动进行频谱分析（心率变异性的 Nyquist 功率：nyHRV）来评估噪声波动，方法是在滤除其分形成分后。我们观察了健康仰卧位受试者和血管迷走性症状患者的 nyHRV。我们通过直立姿势（使用头高位倾斜台试验）来挑战血压稳定。头高位倾斜台位置显著降低了 nyHRV（健康受试者 n = 12，0.128 ± 0.063 对 0.004 ± 0.002，p < 0.01）。头高位倾斜台位置也降低了无血管迷走性症状患者的 nyHRV（n = 24，0.220 ± 0.058 对 0.034 ± 0.015，p < 0.05），但在血管迷走性症状患者中没有降低 nyHRV 在头高位倾斜台试验期间（年龄和性别配对，0.103 ± 0.041 对 0.122 ± 0.069，无显著性差异）。心率变异性包括一种生理性的非谐波非分形噪声波动。这种噪声波动表明调节机制的参与度较低，因为当心血管系统受到挑战（直立姿势）时，它会消失。它还表明心血管不稳定，因为在血管迷走性晕厥之前，它不会在直立患者中消失，这是心血管调节的短暂失败。
