Takase B, Bjerregaard P, Greenwalt T, Kotar M S, Janosik D
Department of Internal Medicine, St. Louis University School of Medicine, Missouri, USA.
Jpn Circ J. 1996 Nov;60(11):841-52. doi: 10.1253/jcj.60.841.
Indices of heart rate variability are non-invasive indicators of neural control of the heart. To investigate the significance of changes in heart rate variability in neurally mediated syncope, we performed head-up tilt testing in 45 patients with syncope of undetermined etiology. Seventeen patients showed a negative response and 28 showed a positive response; 18 had a vasodepressor response (systolic blood pressure dropped > or = 50% without a decrease in heart rate) and 10 had a vasovagal response (systolic blood pressure dropped > or = 50% with a decrease in heart rate of > or = 30%). The mean RR-interval, the standard deviation of normal sinus RR-intervals (standard deviation of RR-interval) and power spectra were measured in consecutive 2 min periods throughout the study. Power spectra consisted of low frequency (0.04-0.15 Hz), high frequency (0.15-0.40 Hz) and total spectra (0.01-1.0 Hz). Both high frequency spectra and the low/high frequency spectra ratio significantly changed with head-up tilt testing regardless of the response. However, high frequency, low frequency and total spectra increased in relation to symptoms. These changes were most profound in the high frequency spectra of subjects with a vasovagal response. Since high frequency spectra reflect parasympathetic tone, a profound change in the high frequency spectra implies that parasympathetic activities play a significant role in patients with a vasovagal response. The assessment of heart rate variability during head-up tilt testing can provide new insight into the pathogenesis of syncope of undetermined etiology.
心率变异性指标是心脏神经控制的非侵入性指标。为了研究心率变异性变化在神经介导性晕厥中的意义，我们对45例病因不明的晕厥患者进行了直立倾斜试验。17例患者呈阴性反应，28例呈阳性反应；18例有血管减压反应（收缩压下降≥50%且心率无下降），10例有血管迷走反应（收缩压下降≥50%且心率下降≥30%）。在整个研究过程中，连续2分钟测量平均RR间期、正常窦性RR间期的标准差（RR间期标准差）和功率谱。功率谱由低频（0.04 - 0.15Hz）、高频（0.15 - 0.40Hz）和总谱（0.01 - 1.0Hz）组成。无论反应如何，高频谱以及低频/高频谱比值在直立倾斜试验中均有显著变化。然而，高频、低频和总谱随症状而增加。这些变化在有血管迷走反应的受试者的高频谱中最为明显。由于高频谱反映副交感神经张力，高频谱的显著变化意味着副交感神经活动在有血管迷走反应的患者中起重要作用。直立倾斜试验期间心率变异性的评估可为病因不明的晕厥的发病机制提供新的见解。
