Corrected QT Interval Prolongations in Patients with non–ST-Elevation Acute Coronary Syndrome

Abstract

Background: The presence of different risk groups among patients with the non–ST-elevation acute coronary syndrome indicates the need for new tools to establish early diagnoses and prognostic stratifications. The role of prolonged corrected QT (QTc) intervals in myocardial ischemia has yet to be thoroughly assessed. The purpose of our study was to assess the significance of QTc prolongations during acute non–ST-segment elevation myocardial infarction (NSTEMI) or unstable angina.

Methods: The QTc interval was measured in 205 patients admitted with NSTEMI or unstable angina to the Coronary Care Unit of Fatemeh Zahra Hospital between 2014 and 2015. On that basis, the patients were divided into those with normal (<440 ms) and the ones with prolonged (≥440 ms) QTc intervals. Echocardiography and coronary angiography were performed within 48 to 72 hours after hospitalization. A logistic regression model was applied to assess the predictors of left ventricular systolic dysfunction.

Results: The mean age of the patients was 58.21±10.72 years, and men comprised 51% of the participants. Overall, a QTc interval prolongation of ≥440 ms was present in 45 subjects (21.95% of the patients), which was significantly associated with a previous myocardial infarction (MI) (P=0.024), a minimum ST depression of 1 mm in the inferior leads (P=0.006), and a maximum left ventricular ejection fraction of 35% (P=0.018). Furthermore, among the different electrocardiographic variables, only a prolonged QTc interval (OR=0.275, 95% CI=0.078–0.976; and P=0.046) was inversely associated with the left ventricular systolic function.

Conclusion: Our study showed that prolonged QTc intervals can be used as a useful risk marker for identifying high-risk patients with the acute coronary syndrome.