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

Abstract

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.