Corrected QT Interval Prolongation: A New Predictor of Cardiovascular Risk in Patients With Non-ST-Elevation Acute Coronary Syndrome

Abstract

Recently we reported that prolongation of the corrected QT (CTc) interval is an independent risk factor in patients with unstable angina and acute ischemic changes. The aim of this study was to determine the prognostic value of this variable in patients with non-ST-segment elevation acute coronary syndrome who do not exhibit acute ischemic changes on admission ECG. The study included 55 patients with this syndrome. On admission, a standard 12-lead ECG was recorded, the cardiac troponin-T was measured and a TIMI (Thrombolysis in Myocardial Infarction) risk score was calculated. The primary endpoint was the combination of nonfatal acute myocardial infarction, percutaneous or surgical revascularization, and cardiac death up to 30 days after discharge. Two independent investigators measured the QT interval manually and the corrected value was derived using Bazett's formula. In the statistical analysis, the following cut-off points were used: the median TIMI risk score, a cardiac troponin-T level of 0.04 ng/mL, and a QTc of 0.458 s. Of the 21 patients (38%) who reached the primary endpoint, 17 (81%) had QTc prolongation. Binary logistic regression analysis showed that QTc prolongation was an independent predictor of the combined endpoint. This study shows that QTc prolongation is an independent predictor of cardiovascular risk in patients with non-ST-segment elevation acute coronary syndrome but without acute ischemic changes on admission ECG.