Rao R K, Yeragani V K
Department of ECE, Indian Institute of Science, Bangalore.
Auton Neurosci. 2001 Apr 12;88(1-2):99-108. doi: 10.1016/S1566-0702(01)00219-3.
In this study, we investigated measures of nonlinear dynamics and chaos of heart rate time series in 30 normal control subjects and 36 age-matched patients with panic disorder in supine and standing postures. We obtained minimum embedding dimension (MED), largest Lyapunov exponent (LLE) and measures of nonlinearity (NL) of heart rate time series. MED quantifies system's complexity, LLE predictability and NL, deviation from linear processes. There was a significant increase in complexity (p < 0.00001), an increase in predictability (decreased chaos) (p < 0.00001) and an increase in nonlinearity (Snet GS) (p = 0.00001), especially in supine posture in patients with panic disorder. Increased NL score in supine posture may be due to a relative increase in cardiac sympathetic activity and an overall decrease in LLE may indicate an impaired cardiac autonomic flexibility in these patients due possibly to a decrease in cardiac vagal activity. These findings may further explain the reported higher incidence of cardiovascular mortality in patients with anxiety disorders.
在本研究中，我们调查了30名正常对照受试者和36名年龄匹配的惊恐障碍患者在仰卧位和站立位时心率时间序列的非线性动力学和混沌指标。我们获得了心率时间序列的最小嵌入维数（MED）、最大Lyapunov指数（LLE）和非线性度（NL）指标。MED量化系统复杂性，LLE量化可预测性，NL量化与线性过程的偏差。复杂性显著增加（p < 0.00001），可预测性增加（混沌减少）（p < 0.00001），非线性度增加（Snet GS）（p = 0.00001），尤其是在惊恐障碍患者的仰卧位时。仰卧位时NL评分增加可能是由于心脏交感神经活动相对增加，而LLE总体下降可能表明这些患者心脏自主神经灵活性受损，这可能是由于心脏迷走神经活动减少所致。这些发现可能进一步解释了焦虑症患者心血管死亡率较高的报道。
