Yoshimura M, Matsumoto K, Watanabe M, Yamashita N, Sanuki E, Sumida Y
Department of Cardiology, Saiseikai Hiroshima Hospital, Hiroshima, Japan.
Jpn Circ J. 1999 Jul;63(7):517-21. doi: 10.1253/jcj.63.517.
The poor sensitivity and the poor predictive value of ST-segment depression have limited the usefulness of the exercise electrocardiogram (ECG) in the diagnosis and evaluation of coronary artery disease (CAD). The QT dispersion (QTD), recorded as the difference between maximal and minimal QT intervals on a 12-lead exercise ECG, is sensitive to myocardial ischemia and may improve the accuracy of exercise testing in patients with CAD who do not show an ST-segment depression. Exercise ECGs were analyzed in 50 subjects who had undergone coronary angiography for clinical indications. None of them showed an ST-segment depression during or after exercise: There were 25 patients with significant coronary artery stenosis and 25 without significant stenosis. The QTD measured before, immediately after, and 1 min after exercise was similar in the 2 groups. The QTD at 3 and 5 min after exercise was significantly greater in patients with CAD than in the controls, and the most marked difference in QTD was observed at 3 min after exercise. A QTD at 3 min after exercise of >60 ms had a sensitivity of 80% and specificity of 88% regarding the diagnosis of CAD. When a deltaQTD (post-exercise QTD minus QTD at rest) at 3 min after exercise of >0 ms was added to a QTD of >60 ms as a condition for positivity, the specificity increased to 96%. QTD measured at 3 min after exercise increases the accuracy of exercise testing in patients with CAD who do not show an ST-segment depression.
ST段压低的敏感性和预测价值欠佳，限制了运动心电图（ECG）在冠状动脉疾病（CAD）诊断和评估中的应用。QT离散度（QTD）记录为12导联运动心电图上最大和最小QT间期的差值，对心肌缺血敏感，可能会提高在运动时未出现ST段压低的CAD患者运动试验的准确性。对50例因临床指征接受冠状动脉造影的受试者的运动心电图进行了分析。他们中没有人在运动期间或运动后出现ST段压低：有25例患者存在明显冠状动脉狭窄，25例无明显狭窄。两组在运动前、运动后即刻和运动后1分钟测量的QTD相似。CAD患者运动后3分钟和5分钟时的QTD显著高于对照组，运动后3分钟时QTD的差异最为明显。运动后3分钟时QTD>60 ms对CAD诊断的敏感性为80%，特异性为88%。当将运动后3分钟时的deltaQTD（运动后QTD减去静息时QTD）>0 ms作为阳性条件添加到QTD>60 ms时，特异性提高到96%。运动后3分钟时测量的QTD提高了在运动时未出现ST段压低的CAD患者运动试验的准确性。
