Lee T M, Su S F, Wang T D, Wang W L, Chen M F, Liau C S, Lee Y T, Tsai C H
College of Medicine, National Taiwan University, National Taiwan University Hospital, Taipei.
Am J Cardiol. 1998 Sep 1;82(5):615-20. doi: 10.1016/s0002-9149(98)00410-x.
The interlead variation in QT interval (QT dispersion) can be used to assess regional inhomogeneity of ventricular repolarization under a variety of conditions, including stress. Patients with syndrome X may have increased sympathetic activity that could change QT interval regionally and give rise to an increase in QT dispersion under exercise testing. To test the hypothesis, 26 consecutive patients with syndrome X (group 1) were studied. Two additional groups matched in terms of age, sex, and left ventricular mass index consisting of 26 nonconsecutive patients with coronary artery disease (group 2) and 20 normal subjects (group 3) were studied for comparison. Standing induced a significantly higher increase of heart rate in group 1 than in groups 2 and 3 (7.5+/-6.0 vs 4.0+/-6.3 and 1.1+/-3.6 beats/min; p = 0.05 and 0.003, respectively). There were significant differences in QT dispersion between groups 1 and 2 on upright standing (48+/-12 vs 34+/-14 ms, p = 0.0003), but not at baseline (33+/-14 vs 38+/-11 ms, p = NS) or at peak exercise (38+/-9 vs 38+/-9 ms, p = NS). Results did not change when QTc dispersion was substituted for QT dispersion. From a conditional multivariate logistic regression analysis, the only independent predictor of occurrence of syndrome X on upright standing was QTc dispersion (odds ratio = 1.255, p = 0.01). Electrocardiographic QTc dispersion provides important clinical information. Patients with syndrome X had a higher increase of heart rate and QTc dispersion in response to standing from the supine position compared with patients with coronary artery disease and normal subjects.
导联间QT间期差异（QT离散度）可用于评估多种情况下心室复极的区域不均一性，包括应激状态。X综合征患者可能存在交感神经活动增强，这可能会使QT间期出现区域性改变，并导致运动试验时QT离散度增加。为验证这一假设，对26例连续的X综合征患者（第1组）进行了研究。另外两组在年龄、性别和左心室质量指数方面相匹配，分别为26例非连续的冠心病患者（第2组）和20例正常受试者（第3组），用于对比研究。站立时，第1组心率升高幅度显著高于第2组和第3组（分别为7.5±6.0、4.0±6.3和1.1±3.6次/分钟；p分别为0.05和0.003）。站立位时第1组和第2组的QT离散度存在显著差异（48±12与34±14毫秒，p = 0.0003），但在基线时（33±14与38±11毫秒，p = 无显著性差异）以及运动峰值时（38±9与38±9毫秒，p = 无显著性差异）无差异。用校正QT离散度（QTc离散度）替代QT离散度时结果不变。条件多因素逻辑回归分析显示，站立位时X综合征发生的唯一独立预测因素是QTc离散度（比值比 = 1.255，p = 0.01）。心电图QTc离散度提供了重要的临床信息。与冠心病患者和正常受试者相比，X综合征患者从仰卧位转为站立位时心率和QTc离散度升高幅度更大。
