Furlan R
Unità Sincopi e Disturbi della Postura, Medicina Interna II, Ospedale L. Sacco, Centro Ricerche Cardiovascolari del CNR, Centro LITA di Vialba, Università degli Studi, Milano.
Ital Heart J Suppl. 2001 May;2(5):484-90.
In the present manuscript the different methodologies aimed at assessing the autonomic profile in humans during a gravitational stimulus have been described. In addition, strengths and drawbacks of the tilt test in relation to occasional orthostatic intolerance were addressed. Finally, different autonomic abnormalities underlying occasional and chronic orthostatic intolerance syndromes have been schematically highlighted. The direct recording of the neural sympathetic discharge from the peroneal nerve (MSNA), in spite of its invasive nature, still represents the recognized reference to quantify the changes in the sympathetic activity to the vessels attending postural modifications. The increase of plasma norepinephrine during a tilt test is achieved by both an increase in plasma spillover and a concomitant decrease in systemic clearance. Changes in the indices of cardiac sympathetic and vagal modulation may also be quantified during a tilt test by power spectrum analysis of RR interval variability. The spectral markers of cardiac autonomic control, if evaluated concomitantly with MSNA, may contribute to assess abnormalities in the regional distribution of the sympathetic activity to the heart and the vessels. The capability of the tilt test of reproducing a vasovagal event or of inducing "false positive responses" seems to be markedly affected by the age, thus suggesting that additional or different etiopathogenetic mechanisms might be involved in the loss of consciousness in older as compared to younger subjects. In subjects suffering from occasional or habitual neurally mediated syncope an increase or, respectively, a decrease in cardiac and vascular sympathetic modulation has been documented before the loss of consciousness. In patients with pure autonomic failure, a global dysautonomia affecting both the sympathetic and the vagal modulation to the heart, seems to be present. In chronic orthostatic intolerance, the most common form of dysautonomia of young women, an abnormal regional distribution of sympathetic activity has been hypothesized during up-right posture. Indeed, during standing a blunted increase of sympathetic activity to the vessels is attended by a cardiac sympathetic overactivity leading to an exaggerated tachycardia.
在本手稿中，已描述了旨在评估人类在重力刺激期间自主神经特征的不同方法。此外，还讨论了倾斜试验与偶发性体位性不耐受相关的优点和缺点。最后，已示意性地突出了偶发性和慢性体位性不耐受综合征背后的不同自主神经异常。尽管腓总神经的神经交感神经放电（MSNA）直接记录具有侵入性，但它仍然是量化因体位改变而导致的血管交感神经活动变化的公认参考标准。倾斜试验期间血浆去甲肾上腺素的增加是由血浆溢出增加和全身清除率同时降低共同实现的。倾斜试验期间，还可通过RR间期变异性的功率谱分析来量化心脏交感神经和迷走神经调节指标的变化。如果与MSNA同时评估心脏自主神经控制的频谱标志物，则可能有助于评估交感神经活动在心脏和血管区域分布的异常情况。倾斜试验重现血管迷走神经事件或诱导“假阳性反应”的能力似乎明显受年龄影响，这表明与年轻受试者相比，老年受试者意识丧失可能涉及额外的或不同的病因发病机制。在偶发性或习惯性神经介导性晕厥患者中，在意识丧失之前已记录到心脏和血管交感神经调节分别增加或减少。在纯自主神经功能衰竭患者中，似乎存在影响心脏交感神经和迷走神经调节的全身性自主神经功能障碍。在慢性体位性不耐受（年轻女性自主神经功能障碍最常见的形式）中，有人假设在直立姿势期间交感神经活动存在异常的区域分布。事实上，站立时血管交感神经活动的增加减弱，同时伴有心脏交感神经活动过度，导致心动过速加剧。
