倾斜试验过程中血浆内皮素的变化及意义

Changes of Plasma Endothelin during Head-up Tilt Test

目的 :探讨血管迷走性晕厥 (VS)患者倾斜试验过程中血浆内皮素 (ET)水平的变化及其意义。 方法 :接受倾斜试验的 42例 VS患者基础倾斜试验阳性反应 (基础阳性组 ) 14例 ,异丙肾上腺素 (ISO)激发阳性反应(ISO阳性组 ) 2 1例 ,阴性反应 (ISO阴性组 ) 7例。11例正常健康人倾斜试验呈阴性反应 (对照组 )。在倾斜试验前 ,倾斜后5、2 0、45分及试验结束或阳性反应时采集外周静脉血 ,以放射免疫法测定血浆 ET水平。 结果 :ISO阳性组阳性反应时血压显著下降 ,ISO阴性组血压始终稳定。试验前有晕厥史者 3组的血浆 ET水平显著高于对照组。倾斜后 5分 ,各组血浆 ET水平显著升高 (P均 <0 .0 1) ;2 0分又明显下降 (P均 <0 .0 1) ,与倾斜前相似 (P均 >0 .0 5 )。阳性反应时或试验结束时 ,各组血浆 ET水平与 45分时相似 ,但仍明显高于倾斜前。 结论 :VS患者倾斜前基础状态下血浆 ET水平升高。倾斜后血浆 ET水平的变化与倾斜试验结果无直接关系 ,只是机体对体位改变或长时间倾斜后的一种代偿性反应。

Objective:To study the changes of plasma endothelin during head up tilt test in patients with vasovagal syncope. Methods:Venous blood samples were obtained serially during head up tilt test in 42 patients with vasovagal syncope and 11 normal subjects.Plasma endothelin was measured with radioimmunoessay. Results:In 14 Patients of basal positive tilt test (basal positive group),24 of positive isoproterenol tilt test (ISO positive group),and 7 of negative isoproterenol tilt test (ISO negative group),the baseline endothelin concentration was significantly higher than in normal subjects(control group) ( p <0 01,<0 05,<0 01,respectively).At the 5th minute after tilt,plasma endothelin increased significantly in all groups (a11 p <0 01) and at the 20th minute it returned almost to baseline(all p >0 05).At the 45th minute,it increased slightly but significantly as compared to baseline.At the end of test or at the time when positive response appeared,the plasma endothelin in all groups was similar to that at the 45th minute after tilt except the basal positive group (similar to that at the 20th minute). Conclusion:The baseline endothelin concentration is elevated in patients with vasovagal syncope.The change of plasma endothelin after tilt is a compensatory mechanism in response to postural change or to prolonged tilt.