血管迷走性晕厥儿童在直立倾斜试验中血流动力学变化及其对美托洛尔疗效的预测

目的探讨直立倾斜试验（HUT）中血管迷走性晕厥（VVS）患儿的心率变化对美托洛尔治疗疗效的预测作用。方法将HUT或硝酸甘油激发HUT（SNHUT）中阳性并接受美托洛尔治疗的26例VVS患儿作为研究对象,根据长期随访资料,将患儿分为美托洛尔治疗有效组（16例）及治疗无效组（10例）,分析2组患儿在HUT或SNHUT过程中心率变化规律及其对美托洛尔治疗疗效的预测价值。结果2组患儿的年龄、性别、晕厥次数、病程、基础心率、血压、应用SNHUT的情况、阳性反应类型及随访时间差异均无统计学意义。治疗有效组患儿在HUT或SNHUT过程中阳性反应前心率显著快,与治疗无效组相比差异有统计学意义（123±15）次／min vs（96±17）次／min,P〈0．01]。HUT或SNHUT阳性反应前心率及较基础心率增加值在2组之间差异具有统计学意义（42±16）次／min vs（18±13）次／min,P〈0．01]。两组患儿在平卧位的基础心率及阳性发生时的心率改变差异无统计学意义,各阶段平均血压改变在两组之间差异均无统计学意义。取阳性反应前心率较基础心率增加30次／min作为界点,预测患儿对美托洛尔治疗有效的灵敏度为81％（13／16）,特异度为80％（8／10）,诊断准确度为81％（21／26）。结论对在阳性反应前存在明显心率增快者（心率较基础值〉30次／min者）选择应用β受体阻滞剂可能更加有效。

Hemodynamic changes during head-up tilt test and predictive value thereof in predicting the efficacy of metoprolol therapy in children with vasovagal syncope

OBJECTIVE: To investigate the value of hemodynamic changes during head-up tilt (HUT) test and predictive value thereof in evaluating the efficacy of metoprolol therapy in children with vasovagal syncope (VSS). METHODS: Twenty-six consecutive children with history of VSS diagnosed by head-up tilt (HUT) or sublingual nitroglycerin potentiated head-up tilt (SNHUT), who were treated with metoprolol for 6 approximately 12 months and followed up for (18 +/- 9) months (12 approximately 36 months), were divided into two groups according to effect of metoprolol: effective treatment group (n = 16, aged 12 +/- 2) without VSS recurrence during treatment and fellow-up, and futile treatment group (n = 10, aged 12 +/- 3). The heart rate changes during HUT or SNHUT were evaluated between the two groups. RESULTS: There were no significant differences between these 2 groups with regard to the demographic and clinical characteristics including age, gender, history, syncope spells, follow-up time and heart rate, mean blood pressure in supine position and during positive response. For example, the baseline heart rate of the effective treatment group was 81 +/- 12 beats/min, not significantly different from that of the futile treatment group (78 +/- 8 beats/min, P = 0.804). However, during tilt test 16 of the 26 patients in the effective treatment group showed tachycardia before positive response, with the mean heart rate of (123 +/- 15) beats/min, whereas all 10 patients in the futile group did not have tachycardia before positive response, with the mean heart rate of (96 +/- 17) beats/min. If an increase of 30 beats/min was taken as a borderline in heart rate during positive response in HUT compared with that of baseline value, in respect of predicting the metoprolol efficacy in the treatment of VVS, the sensitivity was 81% (13/16), the specificity was 80% (8/10), and the diagnostic value was 81% (21/26). CONCLUSION: A marked increase in heart rate in HUT or SNHUT is a better predictor of metoprolol efficacy in the treatment of children with VVS.