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Abstract
Abstract Background: Stress test is used to detect coronary artery disease (CAD). The QTc interval dispersion (dQTc) is an electrocardiographic index of ventricular repolarization heterogeneity. Some researchers have linked transient myocardial ischemia induced by physical exertion with increased heterogeneity of ventricular repolarization measured by dQTc. Objectives: To study the patterns of dQT in patients with and without chronic obstructive CAD and to define a reliable cutoff point for dQT that could become a diagnostic criterion for myocardial ischemia. Methods: We retrospectively analyzed the electrocardiogram in resting and in exercise of 63 patients submitted to exercise test and cardiac catheterization. We divided the patients into three groups: true negative (VN), true positive (VP) and false positive (FP). VN: patients with coronary lesion lower than 70% and exercise test without myocardial ischemia; VP: individuals with stenosis greater than 70% in coronary arteries and a test suggestive of myocardial ischemia; FP: people with stenosis lower than 70% in the coronary arteries and stress test with ischemia criteria. Values of p < 0.05 were considered statistically significant. Results: Resting dQTc was not different among the three groups. However, for the dispersion of the QTc interval in exercise was, respectively, 47 ± 17 ms, 72 ± 42 ms, and 61 ± 31 ms for VN, VP and FP (p = 0.003). Conclusions: Obstructive chronic coronary disease patients have an increase in dQTc during exercise. Measurement of dQTc may be helpful in the diagnosis of myocardial ischemia in the stress test.
Highlights
Stress test has been used in Brazil since 1972 and its sensitivity and specificity for the diagnosis of chronic coronary artery disease (CAD) are 50-72% and 69-74%, respectively.[1,2,3,4] The QT interval dispersion (QTD) measurement is considered a promising instrument to improve the diagnostic accuracy of stress test
The aims of this study are to evaluate whether the QTD index is sensitive to action potential changes in the presence of stress induced myocardial ischemia, as well as to define a cutoff point for QTD that could become a diagnostic criterion for myocardial ischemia
People who had any of the following conditions were excluded from the study: previous acute myocardial infarction (AMI), complete right [RBBB] or left [LBBB] bundle branch block, patients with long QT syndrome; patients with known ventricular dysfunction; unreadable ECG traces or ECG where less than eight electrocradiographic leads were available for QTI measurement.[17]
Summary
Stress test has been used in Brazil since 1972 and its sensitivity and specificity for the diagnosis of chronic CAD are 50-72% and 69-74%, respectively.[1,2,3,4] The QT interval dispersion (QTD) measurement is considered a promising instrument to improve the diagnostic accuracy of stress test. QTD was defined in the 1990s5 as the difference between maximal and minimal QT interval duration measured in 12 ECG leads. Some researchers have linked transient myocardial ischemia induced by physical exertion with increased heterogeneity of ventricular repolarization measured by dQTc. Objectives: To study the patterns of dQT in patients with and without chronic obstructive CAD and to define a reliable cutoff point for dQT that could become a diagnostic criterion for myocardial ischemia. (Int J Cardiovasc Sci. 2020; 33(3):263-271) Keywords: Coronary Artery Disease/physiopathology; Exercise Test/method; Electrocardiography/method; Myocardial Ischemia; Electrophysiology; QT Dispersion Interval Measurement of dQTc may be helpful in the diagnosis of myocardial ischemia in the stress test. (Int J Cardiovasc Sci. 2020; 33(3):263-271) Keywords: Coronary Artery Disease/physiopathology; Exercise Test/method; Electrocardiography/method; Myocardial Ischemia; Electrophysiology; QT Dispersion Interval
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