Neural monitoring of vasovagal syncope
Neural monitoring of vasovagal syncope
复制标题
DOI：
10.1111/j.1540-8159.1997.tb03905.x
复制
发表时间：
1997-03-01
影响因子：
1.8
通讯作者：
Smith, ML
中科院分区：
文献类型：
--
作者：
Ellenbogen, KA;Morillo, CA;Smith, ML
平视倾斜试验已成为一种有价值和广泛接受的诊断工具，用于评估血管迷走神经性晕厥患者。该试验为临床研究人员提供了关注晕厥伴随的血流动力学、体液和神经变化的机会。我们回顾了动物和临床研究，提供了深入了解血管迷走神经性晕厥可能的病理生理机制。血管迷走神经性晕厥患者的血流动力学测量表明，在许多血管迷走神经性晕厥患者中可以看到心室大小相对减小和心脏收缩力增加。血管迷走神经性晕厥患者也表现出许多“夸张”的晕厥神经体液反应。一些研究者报道了血管迷走神经性晕厥患者在晕厥发作之前或期间血浆中肾上腺素、肾素、内皮素、血管加压素、皮质醇、催乳素、-内啡肽和P物质水平的差异变化。这些测量的确切病理生理学意义目前尚不清楚。自主神经张力图的测量可以通过心率变异性或压反射斜率的分析间接完成，也可以通过腓神经的交感神经记录直接完成。我们已经证明血管迷走神经性晕厥患者的压力反射斜率降低。通过微神经摄影，我们和其他人已经证明，在平视倾斜台测试中，在晕厥前11 +/- 3秒，交感神经活动减少。其他各种异常反射，包括运动时前臂血流反应钝化，已经被其他人证实。这些观察结果表明，在事件发生后进行起搏可能不如使用血流动力学传感器有帮助，后者会导致在交感神经戒断之前开始起搏或改变在晕厥之前发生的交感神经张力的下降。
Head-up tilt testing has become a valuable and widely accepted diagnostic tool for evaluation of patients with vasovagal syncope. This test has afforded clinical researchers the opportunity to focus on the hemodynamic, humoral, and neural changes that accompany syncope. We review the animal and clinical studies that provide insight into the possible pathophysiological mechanisms involved in vasovagal syncope. Hemodynamic measurements in patients with vasovagal syncope suggest that a relative decrease in ventricular size and increase in cardiac contractility may be seen in many patients with vasovagal syncope. Patients with vasovagal syncope have also demonstrated numerous ''exaggerated'' neurohumoral responses to syncope. Differential changes in plasma levels of epinephrine, renin, endothelin, vasopressin, cortisol, prolactin, beta endorphins, and substance P have been reported by some investigators either prior to or during a syncopal episode in patients with vasovagal syncope. The precise pathophysiological significance of these measurements is unknown at the present time. Measurements of autonomic tone map be accomplished indirectly with analysis of heart rate variability or baroreflex slope, or directly by sympathetic neural recordings of the peroneal nerve. We have demonstrated decreased baroreflex slopes in patients with vasovagal syncope. Using microneurography, we and others have demonstrated decreased sympathetic nerve activity occurring 11 +/- 3 seconds prior to syncope during head-up tilt table testing. A variety of other abnormal reflexes, including blunted forearm blood flow responses during exercise, have been demonstrated by others. These observations suggest that pacing instituted after the event may not be as helpful as the use of a hemodynamic sensor that will result in the initiation of pacing prior to sympathetic withdrawal or modify the decrease in sympathetic tone that occurs prior to syncope.