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Article Type

Original Study

Abstract

Background Prolonged myocardial contraction and QT interval duration may be found in ischemic viable myocardium, yet it is unclear if noninvasive examination of regional nonhomogeneous myocardial mechanics and QT duration may detect patients with significant coronary artery disease (CAD). Aim To assess the ability of cardiac mechanical and QTc dispersions to identify significant CAD in patients having chest pain with no prior myocardial infarction. Patients and methods We examined 125 patients who had chest pain and evaluated by coronary angiography. They are divided into two groups. CAD group included 75 patients with significant CAD, and control group included 50 patients without significant CAD. We used echocardiographic speckle tracking to calculate longitudinal strain. We measured cardiac contraction duration as the time between the ECG first deflection in QRS complex and longitudinal strain peak within every segment of the 17-segments left ventricular model. We measured mechanical dispersion by calculating the SD of 17-time intervals (dispersionSD17) or by subtracting the shortest contraction duration from the longest one (dispersion-delta). QTc dispersion was defined as the difference between the shortest and the longest QTc intervals as measured in the 12-lead ECG. We compared CAD group and control group regarding mechanical and QTc dispersions. Results The CAD group had longer average contraction duration than the control group (436.13 ± 51.97 vs. 417.79 ± 40.76 ms, P = 0.036), and the contraction duration was significantly associated with QTc interval (r = 0.501, P < 0.001). Mechanical dispersion had an independent correlation with CAD (P < 0.001), but QTc dispersion and duration did not exhibit a significant association with CAD. Mechanical dispersion exhibited an incremental value over global longitudinal strain, wall motion score index, and conventional risk factors in identifying significant CAD. Conclusions In individuals with no prior myocardial infarction, the myocardial mechanical and QTc dispersions can predict the existence of significant CAD. Cardiac mechanical dispersion has an incremental value on global longitudinal strain for identification of patients with significant CAD.

Keywords

Coronary artery disease, mechanical dispersion, QT dispersion, QT interval

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