Tulppo M P, Mäkikallio T H, Seppänen T, Airaksinen J K, Huikuri H V
Department of Medicine, University of Oulu, Finland.
Am J Physiol. 1998 Mar;274(3):H810-6. doi: 10.1152/ajpheart.1998.274.3.H810.
Concomitant sympathetic and vagal activation can occur in various physiological conditions, but there is limited information on heart rate (HR) behavior during the accentuated sympathovagal antagonism. Beat-to-beat HR and blood pressure were recorded during intravenous infusion of incremental doses of norepinephrine in 18 healthy male volunteers (mean age 23 +/- 5 yr). HR and blood pressure spectra and two-dimensional Poincaré plots were generated from the baseline recordings and from the recordings at different doses of norepinephrine. The mean blood pressure increased (from 90 +/- 7 to 120 +/- 9 mmHg, P < 0.001), HR decreased (from 60 +/- 9 to 48 +/- 7 beats/min, P < 0.001), and the high-frequency spectral component of HR variability increased (P < 0.001) during the norepinephrine infusion as evidence of accentuated sympathovagal interaction. Abrupt aperiodic changes in sinus intervals that were not related to respiratory cycles or changes in blood pressure occurred in 14 of 18 subjects during the norepinephrine infusions. These fluctuations in sinus intervals resulted in a complex or parabola-shaped structure of the Poincaré plots of successive R-R intervals and a widening of the high-frequency spectral peak. In four subjects, the abrupt fluctuations in sinus intervals were followed by a sudden onset of fixed R-R interval dynamics with a loss of respiratory modulation of HR, resulting in a torpedo-shaped structure of the Poincaré plots. These data show that HR behavior becomes remarkably unstable during accentuated sympathovagal interaction, resembling stochastic dynamics or deterministic chaotic behavior. These features of HR dynamics can be better identified by dynamic analysis of beat-to-beat behavior of R-R intervals than by traditional analysis techniques of HR variability.
交感神经和迷走神经的同时激活可发生在多种生理状态下，但关于交感迷走神经拮抗增强时心率（HR）行为的信息有限。在18名健康男性志愿者（平均年龄23±5岁）静脉输注递增剂量去甲肾上腺素期间，记录逐搏心率和血压。从基线记录以及不同剂量去甲肾上腺素记录中生成心率和血压谱以及二维庞加莱图。去甲肾上腺素输注期间，平均血压升高（从90±7 mmHg升至120±9 mmHg，P<0.001），心率降低（从60±9次/分钟降至48±7次/分钟，P<0.001），心率变异性的高频谱成分增加（P<0.001），作为交感迷走神经相互作用增强的证据。在18名受试者中有14名在去甲肾上腺素输注期间出现与呼吸周期或血压变化无关的窦性间期突然非周期性变化。这些窦性间期的波动导致连续R-R间期的庞加莱图呈复杂或抛物线形结构，高频谱峰增宽。在4名受试者中，窦性间期的突然波动之后是固定R-R间期动态的突然出现，心率的呼吸调节丧失，导致庞加莱图呈鱼雷形结构。这些数据表明，在交感迷走神经相互作用增强期间，心率行为变得非常不稳定，类似于随机动力学或确定性混沌行为。与传统的心率变异性分析技术相比，通过对R-R间期的逐搏行为进行动态分析可以更好地识别心率动力学的这些特征。
