Sneddon J F, Counihan P J, Bashir Y, Haywood G A, Ward D E, Camm A J
Department of Cardiological Sciences, St. George's Hospital Medical School, London, United Kingdom.
Am J Cardiol. 1993 Jan 1;71(1):72-6. doi: 10.1016/0002-9149(93)90713-m.
Immediate responses to head-up tilt were determined in 78 consecutive patients with unexplained syncope undergoing 45-minute tilt tests at 60 degrees. Thirty-four patients developed neurally mediated syncope (mean time to syncope 18 minutes), 40 tolerated the full duration of tilt, and 4 were unable to complete the study but did not develop syncope. Blood pressure, heart rate, forearm blood flow and forearm vascular resistance were measured at baseline and after 2 and 5 minutes of tilt. Syncopal and nonsyncopal patients were well-matched for age and baseline hemodynamic parameters. There was no difference between the groups in heart rate or blood pressure at 2 minutes, but there was a small but significant difference in percent reduction in mean arterial pressure at 5 minutes. After 2 and 5 minutes of tilt, mean forearm blood flow was 2.4 and 2.6 ml/min/100 ml, respectively, in syncopal patients compared with 1.6 (p < 0.05) and 1.7 ml/min/100 ml (p < 0.01), respectively, in patients who tolerated 45 minutes of tilt. In syncopal patients, forearm vascular resistance was 51.0 and 44.0 at 2 and 5 minutes, respectively, whereas in nonsyncopal patients, it was 82.4 (p < 0.02) and 73.1 (p < 0.001), respectively. These differences remained consistent when only data for patients developing syncope after > 15 minutes were included in the analysis. Patients with neurally mediated syncope have clearly demonstrable abnormalities in vascular control immediately after assumption of the upright posture. The results shed new light on the pathophysiology of neurally mediated syncope.
对78例不明原因晕厥患者进行了60度45分钟的倾斜试验，以确定其对头部上抬倾斜的即时反应。34例患者发生神经介导性晕厥（晕厥平均时间为18分钟），40例患者耐受了整个倾斜试验过程，4例患者无法完成研究但未发生晕厥。在基线、倾斜2分钟和5分钟后测量血压、心率、前臂血流量和前臂血管阻力。晕厥和未晕厥患者在年龄和基线血流动力学参数方面匹配良好。两组在倾斜2分钟时心率或血压无差异，但在倾斜5分钟时平均动脉压降低百分比存在微小但显著的差异。倾斜2分钟和5分钟后，晕厥患者的平均前臂血流量分别为2.4和2.6 ml/min/100 ml，而耐受45分钟倾斜的患者分别为1.6（p<0.05）和1.7 ml/min/100 ml（p<0.01）。在晕厥患者中，倾斜2分钟和5分钟时前臂血管阻力分别为51.0和44.0，而在未晕厥患者中分别为82.4（p<0.02）和73.1（p<0.001）。当仅将倾斜15分钟后发生晕厥的患者数据纳入分析时，这些差异仍然一致。神经介导性晕厥患者在采取直立姿势后立即在血管控制方面有明显可证实的异常。这些结果为神经介导性晕厥的病理生理学提供了新的线索。
