BAROREFLEX HYSTERESIS AND ARTERIAL STIFFNESS

这项研究将机械地描述一个知之甚少的方面，动脉压力反射控制，可以影响全身动脉压的调节。 动脉压-心动周期关系并不是简单地描述S形曲线，而是表现出滞后。 也就是说，心动周期反应取决于压力变化的方向;在任何压力下，心率在福尔斯下降期间都比在上升期间慢。 动脉压力反射的这一特点可能具有重要的临床意义，特别是在认识水肿综合征方面。 这项工作将探讨可能的压力反射滞后的关键组成部分-压力感觉血管扩张。较低的扩张性不仅可以改变压力反射敏感性，而且可以增加压力反射滞后。 如果滞后被动脉硬化放大，这本身就可能产生不协调的心率反应，从而导致脑血流量减少和晕厥。 将使用快速血压诱导的动脉压变化来表征整个反射范围内的自主压力反射滞后。 自主神经反应和压力变化将与颈动脉压力感觉血管拉伸的并行测量相关，以检查压力反射滞后的粘弹性成分。 由于主要的拉伸决定了压力感觉血管的扩张性，因此将在两种条件下表征滞后以改变拉伸水平（仰卧和倾斜45 °）。由于颈动脉僵硬度较大的个体可能表现出适应不良的夸张滞后，这些关系将不仅在血压正常者中进行检查，而且在先前已显示颈动脉僵硬度较大的中年高血压患者中进行检查。 这项工作可能会提供关键的见解，以了解动脉血压失调的高患病率，以秩序和高血压患者。

This research will mechanistically describe a poorly understood aspect of arterial baroreflex control which can impact the regulation of systemic arterial pressure. The arterial pressure - heart period relation does not simply describe a sigmoid, but demonstrates a hysteresis. That is, heart period responses depend on the direction of pressure change; at any pressure, heart rates are slower during falls than during rises. This characteristic of the arterial baro-reflex may have significant clinical import especially in understanding hypotensive syndromes. This work will examine the likely key component of baroreflex hysteresis -- barosensory vessel distensibility. Lesser distensibility may not only alter baroreflex sensitivity, but also augment baroreflex hysteresis. If hysteresis is exaggerated by arterial stiffening, this alone could produce discordant heart rate responses to hypotensive stimuli, leading to reduced cerebral blood flow and syncope. Rapid pharmacologically induced arterial pressure changes will be used to characterize autonomic baroreflex hysteresis through the full reflex range. The autonomic responses and pressure changes will be related to concurrent measures of carotid barosensory vessel stretch to examine the viscoelastic component of baroreflex hysteresis. Since the prevailing stretch determines barosensory vessel distensibility, hysteresis will be characterized under two conditions to vary the level of stretch (supine and 45 tilt). Since individuals with greater carotid stiffness may demonstrate a maladaptive exaggerated hysteresis, these relationships will be examined not only in normotensives but also in middle aged hypertensives who have been shown previously to have greater carotid stiffness. This work may provide key insight to understand the high prevalence of arterial pressure dysregulation in order and hypertensive individuals.