Contribution of the peak exercise QT dispersion to the accuracy of an exercise test during the evaluation of coronary artery disease

Objective - Regional defects in ventricle repolarization are extremely sensitive to ischaemia which can be measured as QT dispersion (QTd). We investigated the role of QTd calculated at the time of peak exercise during treadmill studies. Methods and results - Thirty-three women and eighty men, whose treadmill test results and coronary angiography studies had been examined, were divided into four groups according to the test results: 1)subjects with a negative treadmill test and without significant stenosis results in the angiography, were considered normal (N; n = 35); 2) subjects with both a positive exercise test and a significant presence of stenotic coronary arteries, were considered true positive (TP; n = 52); 3) subjects with a positive exercise test, but without significant stenosis results in the angiography, were considered false positive (FP; n = 14); 4) subjects with a negative treadmill study, despite significantly stenotic arteries, were considered false negative (FN; n = 12), All subjects were evaluated on the basis of age, significant ST-segment depression, peak heart rate, rest and peak exercise QT, and QpT (measured from the beginning of the QRS complex to the highest point of the T wave) dispersion, and corrected (QTcd, QpTcd) values for heart rate. The most significant differences were observed between the N and the TP groups in terms of QTd and QTcd (p < 0.01), with a higher correlation (r = 0.48). A significant relationship was also observed in terms of QpT and QpTcd values during peak exercise (p < 0.01). The sensitivity of the peak exercise QTcd and QTcd greater than or equal to 70 ms in determining coronary artery disease was found to be 74%. In cases of QTcd greater than or equal to 70 ms, in addition to ST-segment depression, the test was found to be less sensitive, but more specific at 96%. Conclusion - It suggests that when peak exercise QTd and QpTd values are taken into account, with the exception of the ST-segment depression, the accuracy of the exercise test will increase and false positive results will decrease.