倾斜实验中脑-心耦合关系研究

Investigation on Brain-Heart Coupling during Head-Up Tilt Test

大脑皮层能够通过自主神经系统对心血管活动进行调控,其机理的研究对心律不齐、高血压、心衰等疾病的诊疗与防控有重要的价值。同步采集27名健康被试在静息和70°直立倾斜实验(HUT)中前额叶皮层(MPFC)的近红外光谱和心电、连续血压及胸阻抗信号,通过心率变异性、格兰杰因果方法(GC)等研究心血管参数的变化,以及MPFC血流量与交感/副交感输出流(由nLF和HF表示)、RRI的耦合关系。研究结果显示:HUT实验中心输出量(CO)平均减少24%(P<0.001),心率(HR)增加35%(P<0.001),舒张压(DBP)升高7%(P<0.001),收缩压(SBP)在HUT初期降低,但均值较静息状态无明显变化;nLF逐渐增强,HF逐渐减弱,随后分别保持高于38.75±9.25 vs58.62±8.58(P<0.001)和低于1.11±0.76 vs 0.80±0.48(P<0.05)静息状态的稳定水平;MPFC血流量与交感和副交感输出流显著相关,相关系数分别为0.58和0.66;GC分析显示频段特异性,在0.04~0.15 Hz(主频0.1 Hz)频段表现为"脑→心"(P<0.05),而在0.15~0.4 Hz(主频0.3 Hz)频段表现为"心→脑"(P<0.001)。研究结果表明:HUT能引起显著的心血管响应,主要由交感和副交感输出流所调控;MPFC参与该响应过程,且由主频0.1 Hz的低频振荡信号(~0.1 Hz)介导其与自主输出流的联系。研究发现脑-心耦合的新证据,即健康机体在直立应激过程中的脑-心交互特征,~0.1 Hz振荡信号在介导MPFC调控自主输出流方面具有重要作用。

Cerebral cortex can modulate cardiovascular activities,which is mediated by autonomic nervous system（ ANS）. The investigation of the underlying mechanism plays an important role in the diagnosis,treatment,prevention and control of diseases such as arrhythmia,hypertension and heart failure. ECG,BP,chest impedance signals and near infrared spectroscopy（ NIRS） signals in the medial prefrontal cortex（ MPFC）were collected synchronously in 27 healthy subjects in supine condition and during 70° head-up tilt test（ HUT）. Heart rate variability（ HRV） and Granger causality（ GC） methods were applied to investigate cardiovascular responses in HUT and demonstrate the interactions between cerebral blood volume（ CBV） in the MPFC and sympathetic/parasympathetic outflows（ indicated by nLF and HF,respectively） as well as between CBV in the MPFC and RRI. Results showed that 1） CO decreased by 24%（ P〈0. 001）,HR and DBP increased by 35%（ P〈0. 001） and 7%（ P〈0. 001） respectively,while SBP almost showed no change compared with baseline even though it declined at the beginning of HUT; 2） nLF increased while HF decreased gradually,and then kept a relatively stable state with the former more activated（ 38. 75±9. 25 vs 58. 62±8. 58,P0. 001） while the latter less activated（ 1. 11±0. 76 vs 0. 80±0. 48,P0. 05） than the supine condition; 3）CBV in the MPFC was significantly correlated with both sympathetic and parasympathetic outflows and the correlation coefficients were 0. 58 and 0. 66 respectively; 4） GC showed frequency specificity with preference of＂brain→heart＂（ P0. 05） in the frequency band of 0. 04-0. 15 Hz while＂heart→brain＂（ P0. 001） in the frequency band of 0. 15-0. 4 Hz. Our results indicated that significant cardiovascular responses,mainly modulated by sympathetic and parasympathetic outflows,were elicited during HUT and that the MPFC was involved in the ANS-mediated cardiovascular control with ~ 0. 1 Hz oscillations mediating the process. This study provided new evidence for the brain-heart coupling（ the characteristic brain-heart interactions in healthy subjects during HUT） and we found that ~ 0. 1 Hz oscillations play an important role in mediating cerebral autonomic control.