Natale A, Akhtar M, Jazayeri M, Dhala A, Blanck Z, Deshpande S, Krebs A, Sra J S
Electrophysiology Laboratory, Milwaukee Heart Institute of Sinai Samaritan Medical Center, Milwaukee, Wis., USA.
Circulation. 1995 Jul 1;92(1):54-8. doi: 10.1161/01.cir.92.1.54.
Head-up tilt test is increasingly being used to evaluate patients with syncope. This study was designed to evaluate the specificity of head-up tilt testing using different tilt angles and isoproterenol infusion doses in normal volunteers with no prior history of syncope or presyncope.
One hundred fifty volunteers were randomized to two groups of 75 each. In group 1, subjects were further randomized to have head-up tilt testing at a 60, 70, or 80 degree angle at baseline followed by repeat tilt testing during a low-dose isoproterenol infusion that increased the heart rate by an average of 20%. In group 2, after having a baseline head-up tilt test at a 70 degree angle for a maximum of 20 minutes, subjects were randomized to have a repeat tilt table testing at a 70 degree angle during a low-dose, 3 micrograms/min, or 5 micrograms/min isoproterenol infusion. In group 1, syncope or presyncope along with hypotension developed in 2 subjects during the baseline test at 60 and 70 degrees of tilt and in 5 subjects during tilting at 80 degrees. The addition of low-dose isoproterenol reduced the specificity minimally from 92% to 88% at both 60 and 70 degrees of tilt but substantially to 60% at an 80 degrees angle. However, 6 of the 10 subjects with a positive test at an 80 degree angle had an abnormal response after 10 minutes of tilt testing. In group 2, using various isoproterenol doses with tilt table testing at a 70 degree angle, low-dose (mean infusion dose, 1.5 +/- 0.45 microgram/min), 3 micrograms/min, and 5 micrograms/min isoproterenol infusions elicited an abnormal response in 1 (4%), 5 (20%), and 14 (56%) of the subjects, respectively. Using multiple logistic regression analysis, head-up tilt testing at an 80 degree angle (P = .01) or during 3 micrograms/min (P = .02) and 5 micrograms/min isoproterenol infusion rates (P < .001) was the most significant predictor of an abnormal response.
Head-up tilt testing at a 60 or 70 degree angle with or without low-dose isoproterenol infusion provides an adequate specificity. Caution is needed, however, in interpreting the results if the head-up tilt test at 80 degrees is extended beyond 10 minutes or if high doses of isoproterenol are used.
头高位倾斜试验越来越多地用于评估晕厥患者。本研究旨在评估在无晕厥或晕厥前病史的正常志愿者中，使用不同倾斜角度和异丙肾上腺素输注剂量进行头高位倾斜试验的特异性。
150名志愿者被随机分为两组，每组75人。在第1组中，受试者进一步随机分为在基线时以60度、70度或80度角进行头高位倾斜试验，随后在低剂量异丙肾上腺素输注期间重复倾斜试验，该输注使心率平均增加20%。在第2组中，在以70度角进行最长20分钟的基线头高位倾斜试验后，受试者被随机分为在低剂量（3微克/分钟或5微克/分钟）异丙肾上腺素输注期间以70度角重复倾斜试验。在第1组中，在60度和70度倾斜的基线试验期间，2名受试者出现晕厥或晕厥前状态并伴有低血压，在80度倾斜时5名受试者出现上述情况。添加低剂量异丙肾上腺素在60度和70度倾斜时将特异性从92%降至88%，降低幅度最小，但在80度角时大幅降至60%。然而，在80度角试验阳性的10名受试者中，有6名在倾斜试验10分钟后出现异常反应。在第2组中，在70度角进行倾斜试验时使用不同剂量的异丙肾上腺素，低剂量（平均输注剂量，1.5±0.45微克/分钟）、3微克/分钟和5微克/分钟的异丙肾上腺素输注分别使1名（4%）、5名（20%）和14名（56%）受试者出现异常反应。使用多因素逻辑回归分析，80度角（P = 0.01）或在3微克/分钟（P = 0.02）和5微克/分钟异丙肾上腺素输注速率时（P < 0.001）进行头高位倾斜试验是异常反应的最显著预测因素。
60度或70度角进行头高位倾斜试验，无论是否输注低剂量异丙肾上腺素，都具有足够的特异性。然而，如果80度头高位倾斜试验超过10分钟或使用高剂量异丙肾上腺素，则在解释结果时需要谨慎。
