迷走神經性昏厥(Vaso-vagal Syncope)之年輕患者通常具有敏感性內皮功能(Endothelial Function)及副交感過盛,當姿勢變更時會有低血壓及低心跳現象
Endothelial function in young subjects with vaso-vagal syncope.
Biomed Pharmacother. 2006; 60(8):448-52 (ISSN: 0753-3322)
Galetta F; Franzoni F; Plantinga Y; Ghiadoni L; Merico G; Tocchini L; Braccini L; Rossi M; Carpi A; Taddei S; Santoro G
Department of Internal Medicine, University of Pisa, Via Roma 67, Pisa, Italy.
BACKGROUND: The aim of this study was to determine whether endothelial function and inappropriate peripheral vasomotion have a significant role in the pathogenesis of neurally mediated syncope. METHODS: In 16 patients (mean age 28.2+/-5.8 years) with previous vaso-vagal syncope and in matched healthy subjects, endothelium-dependent flow-mediated dilation (FMD) and endothelium-independent response to glyceryl trinitrate (GTN), 25 mug, were measured in the brachial artery from high-resolution ultrasonography. Heart rate variability (HRV) analysis at rest and during tilt test was compared between two groups. RESULTS: In the subjects with positive tilt test, all HRV parameters were significant higher respect to subjects with negative tilt test (P<0.001). The patients with positive tilt test, showed persistent, marked variability of heart rate (HR), due to increased vagal activity with withdrawal sympathetic tone and consequently reduction of blood pressure (BP) (-30.4+/-4.2 mmHg, P<0.001) accompanied by a decrease in HR (-24.3+/-4.5 beats/min, P<0.001) compared to negative tilt test subjects. These findings prove the real presence of vagal hypertone in patients with syncope. In our study, HR reached values lower than 40 beats/min. FMD in patients with neurally mediated syncope were significantly greater than those in controls (respectively, 9.2+/-2.8% vs. 4.6+/-1.4%, P<0.01) whereas no differences were shown in the response to GTN (18.4+/-4.4% vs. 16.1+/-4.2%, n.s.). CONCLUSIONS: The augmented endothelial function and the abnormal vasodilation of peripheral arteries in association with bradycardia play an important role in the development of vaso-vagal syncope in young subjects.