Takase Bonpei, Masaki Nobuyuki, Hattori Hidemi, Ishihara Masayuki, Kurita Akira
Department of Intensive Care Medicine, National Defense Medical College, National Defense Medical College Research Institute, Saitama, Japan.
Anadolu Kardiyol Derg. 2009 Jun;9(3):189-95.
The electrocardiographic index of QT dispersion (QTd) is related to the occurrence of arrhythmia. In patients with suspected or known coronary artery disease, QTd may be affected by exercise. We investigated whether QTd that is automatically calculated by a newly developed computer system could be used as a marker of exercise-induced myocardial ischemia.
The design of this study was prospective and observational. Eighty-three consecutive patients were enrolled in this study. Their QTd was measured at rest and after 3 min of exercise during exercise-stress Thallium-201 scintigraphy and compared with conventional ST-segment changes. The patients were classified into 4 groups (normal group, redistribution group, fixed defect group, redistribution with fixed defect group) based on the result of single photon emission computed tomography. As statistical analysis, one-way ANOVA with post-hoc Scheffe's method, receiver-operating characteristics (ROC) and multiple logistic regression analysis were performed.
At rest, QTd was significantly greater (p<0.05) in the fixed defect group (52+/-21 ms) and the redistribution with fixed defect group (53+/-20 ms) than in the normal group (32+/-14 ms) and the redistribution group (31+/-16 ms). However, QTd tended to increase after exercise in the redistribution group, while QTd tended to decrease in the normal group, the fixed defect group, and the redistribution with fixed defect group (QTd after exercise, normal group, 28+/-17 ms, redistribution group, 35+/-19 ms, fixed defect group, 43+/-25 ms, redistribution with fixed defect group, 49+/-27 ms). Exercise significantly increased QTcd (RR interval-corrected QT dispersion) in the redistribution group. The best cut-off values of QTd and QTcd obtained from ROC curves for exercise-induced myocardial ischemia were 41.6 ms and 40.4 ms, respectively (Qtd--AUC 0.68, 95%CI 0.53- 0.83 and QTcd--AUC 0.67, 95%CI 0.55-0.80). Using these values as cut-off ones, QTd, QTcd, and conventional ST-segment change had comparable sensitivities and specificities for detecting exercise-induced myocardial ischemia (sensitivity - 60%, 58% and 49%, respectively;specificity - 78%, 80% and 83%, respectively). In addition, multiple logistic regression analysis showed that QTd (OR=2.01, 95%CI 1.15-4.10, p<0.05), QTcd (OR=2.12, 95% CI 1.02-4.30, p<0.05) and ST-segment change (OR=1.89, 95%CI 1.03-3.40, p<0.05), were the significantly associated with exercise-induced myocardial ischemia.
QT dispersion and/or QTcd after exercise could be a useful marker for exercise-induced myocardial ischemia in routine clinical practice.
QT离散度（QTd）这一心电图指标与心律失常的发生有关。在疑似或已知冠心病患者中，QTd可能受运动影响。我们研究了新开发的计算机系统自动计算的QTd是否可作为运动诱发心肌缺血的标志物。
本研究设计为前瞻性观察性研究。连续纳入83例患者。在运动负荷铊-201心肌显像期间，于静息时及运动3分钟后测量其QTd，并与传统ST段改变进行比较。根据单光子发射计算机断层扫描结果将患者分为4组（正常组、再分布组、固定缺损组、再分布合并固定缺损组）。作为统计分析，采用事后Scheffe法的单因素方差分析、受试者工作特征（ROC）分析及多元逻辑回归分析。
静息时，固定缺损组（52±21毫秒）和再分布合并固定缺损组（53±20毫秒）的QTd显著高于正常组（32±14毫秒）和再分布组（31±16毫秒）（p<0.05）。然而，再分布组运动后QTd有增加趋势，而正常组、固定缺损组和再分布合并固定缺损组运动后QTd有下降趋势（运动后QTd，正常组28±17毫秒，再分布组35±19毫秒，固定缺损组43±25毫秒，再分布合并固定缺损组49±27毫秒）。运动使再分布组的QTcd（RR间期校正的QT离散度）显著增加。从ROC曲线获得的运动诱发心肌缺血的QTd和QTcd的最佳截断值分别为41.6毫秒和40.4毫秒（QTd——曲线下面积0.68，95%可信区间0.53 - 0.83；QTcd——曲线下面积0.67，95%可信区间0.55 - 0.80）。以这些值作为截断值，QTd、QTcd和传统ST段改变在检测运动诱发心肌缺血方面具有相当的敏感性和特异性（敏感性分别为60%、58%和49%；特异性分别为78%、80%和83%）。此外，多元逻辑回归分析显示，QTd（比值比=2.01，95%可信区间1.15 - 4.10，p<0.05）、QTcd（比值比=2.12，95%可信区间1.02 - 4.30，p<0.05）和ST段改变（比值比=1.89，95%可信区间1.03 - 3.40，p<0.05）与运动诱发心肌缺血显著相关。
运动后的QT离散度和/或QTcd可能是常规临床实践中运动诱发心肌缺血的有用标志物。
