Value of QT Dispersion in the Interpretation of Exercise Stress Test in Women

Background: Exercise testing in women is associated with a high incidence of false-positive ECG changes and should be combined with an imaging study. The QT dispersion (QTD), recorded as the difference between maximum and minimum QT intervals on a 12-lead ECG, is sensitive to myocardial ischemia and may improve the accuracy of exercise testing in women. Methods and Results: Exercise ECGs were analyzed in 64 women who had undergone exercise ECG and coronary angiography for clinical indications: 20 patients with normal exercise stress test and nonsignificant (≤50% diameter narrowing of a major epicardial coronary artery) coronary artery disease (CAD) on angiography (true-negative; TN group), 20 patients with positive exercise stress tests (≤1 mm ST-segment depression or reversible perfusion defects) and significant CAD (true-positive; TP group), and 24 patients with positive exercise stress tests but no significant CAD (false-positive; FP group). The exercise QTD was 45±15 ms in TN, 80±23 ms in TP (P<.0001 versus TP), and 41±14 ms in FP (P=NS versus TN and <.0001 versus TP) groups. A stress QTD of >60 ms had a sensitivity of 70% and specificity of 95% for the diagnosis of significant CAD compared with 55% (P<.05) and 63% (P<.01), respectively, for ≤1 mm ST-segment depression during stress. When QTD of >60 ms was added to ST-segment depression as a condition for positive test, the specificity increased to 100%. Conclusions: Exercise QTD is an easily measurable ECG variable that significantly increases the accuracy of exercise testing in women.