Value of the corrected QT interval dispersion obtained exercise electrocardiography in determining remote vessel disease in patients with healed Q-wave myocardial infarction.

BACKGROUND: QT and corrected QT dispersion (QTD, QTcD) obtained by using the standard 12-lead ECG is a marker of nonhomogenous ventricular repolarization. QTD obtained from exercise ECG increases the diagnostic reliability of ST-segment changes. The aim of this study was to investigate the diagnostic accuracy of the QTD and QTcD obtained by a 12-lead ECG during the peak exercise in determining remote vessel disease in patients with healed Q-wave MI.

METHODS: Eighty patients with healed Q-wave MI (mean age 54 +/- 8 years; 71 men, 9 women; 29 anterior; 51 inferior MI) who underwent exercise stress testing and coronary angiography were included in this study. Patients were divided into two groups, with (group I) and without (group II) remote vessel coronary artery disease. During peak exercise, sensitivity, specificity, negative and positive predictive value of the ST-segment depression, and QTcD were compared between both groups. Moreover, the resting and peak exercise ECG parameters were compared between group I and group II.

RESULTS: In coronary angiography, remote vessel disease was detected in 48 patients (group I). In determining remote vessel disease, the sensitivity, specificity, and the negative and positive predictive values of the peak exercise QTcD > or = 70 ms were significantly higher than those of the peak exercise ST-segment depression (81%, 63%, 69%, and 76% vs 71%, 53%, 55%, and 69%, respectively; P < 0.01 for all comparisons). In group I, QTD and QTcD were significantly higher in patients with anterior wall MI than those with inferior wall MI both during the resting and peak exercise ECG. In group II, the resting QTD and QTcD were significantly higher in patients with anterior wall MI than those with inferior wall MI. In patients with anterior wall MI and inferior wall MI, QTD and QTcD significantly increased with exercise in group I.

CONCLUSION: In patients with healed Q-wave MI, the value of QTcD > or = 70 ms increases the diagnostic accuracy of the exercise stress testing in determining remote vessel disease.