Tochikubo O, Kawano Y, Miyajima E, Toshihiro N, Ishii M
Second Department of Internal Medicine, Urafune Hospital of Yokohama City University, Japan.
Hypertens Res. 1997 Sep;20(3):157-66. doi: 10.1291/hypres.20.157.
It is well known that cardiovascular accidents such as myocardial infarction frequently occur in the morning, but their triggering mechanisms are not clear. The present study investigated circadian variations of hemodynamics and baroreflex functions. Twenty-three patients with essential hypertension were studied. Direct blood pressure (BP) and ECG were recorded by telemeter over 24 h, and then computer-analyzed. The pulse-contour method was used to measure cardiac output (CO) and total peripheral vascular resistance (TPR). The ratio of low to high frequency components (LF/HF) of the RR-interval on ECG was calculated by power spectral analysis. The baroreflex sensitivity index (BRI) was measured on the basis of the ratio delta RR/delta Ps (delta Ps = spontaneous decrease in systolic BP, delta RR = change in RR). Furthermore, 24-h BP changes were transformed algebraically into positive load component (PC) and negative load component (NC) by using a Windkessel model. The circadian variation of hematocrit (Ht) was also measured. The least squares method was used to determine the time at which the maximum and minimum value of each measurement occurred. Whereas the maximum values for BP and CO occurred in the evening (18:30, 17:00), the maximum values for TPR and LF/HF occurred between 06:30 and 08:00, and the minimum value for BRI occurred at 08:00. PC significantly correlated with Ps, heart rate, and CO (r = 0.81, 0.92, 0.67), and NC significantly correlated with BRI and LF/HF (r = 0.71, 0.64). PC (related to cardiovascular function) reached a maximum and NC (related to baroreflex function) reached a minimum in the late morning (11:00). Ht was highest immediately after the subjects got out of bed. These hemodynamic imbalances may negatively influence coronary blood flow in the morning.
众所周知，心肌梗死等心血管意外事件常在早晨频发，但其触发机制尚不清楚。本研究调查了血流动力学和压力反射功能的昼夜变化。对23例原发性高血压患者进行了研究。通过遥测技术记录24小时的直接血压（BP）和心电图，然后进行计算机分析。采用脉搏轮廓法测量心输出量（CO）和总外周血管阻力（TPR）。通过功率谱分析计算心电图RR间期的低频与高频成分之比（LF/HF）。基于RR变化量与收缩压变化量之比（ΔPs = 收缩压自发下降，ΔRR = RR变化）测量压力反射敏感性指数（BRI）。此外，利用Windkessel模型将24小时血压变化代数转换为正负荷分量（PC）和负负荷分量（NC）。还测量了血细胞比容（Ht）的昼夜变化。采用最小二乘法确定每次测量的最大值和最小值出现的时间。BP和CO的最大值出现在晚上（18:30、17:00），TPR和LF/HF的最大值出现在06:30至08:00之间，BRI的最小值出现在08:00。PC与收缩压、心率和CO显著相关（r = 0.81、0.92、0.67），NC与BRI和LF/HF显著相关（r = 0.71、0.64）。PC（与心血管功能相关）在上午晚些时候（11:00）达到最大值，NC（与压力反射功能相关）达到最小值。受试者起床后Ht立即最高。这些血流动力学失衡可能会对早晨的冠状动脉血流产生负面影响。
