IJCS | Volume 33, Nº3, May / June 2020

DOI: https://doi.org/10.36660/ijcs.201810681 Introduction 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. 1-4 The QT interval dispersion (QTD) measurement is considered a promising instrument to improve the diagnostic accuracy of stress test. QTD was defined in the 1990s 5 as the difference between maximal and minimal QT interval durationmeasured in 12 ECG leads. It has been proposed as a regional marker of ventricular repolarization dispersion (VRD) and correlates with the dispersion of action potentials (AP) in animals and humans. 6 QT interval, measured from the beginning of the QRS complex to the end of the T wave, represents the time it takes for ventricular myocardial cells to depolarize and repolarize. 7 However, U-wave should not be included in the measurement. 8 During exertion, patients with chronic CAD present increased ventricular repolarization heterogeneity, 263 ORIGINAL ARTICLE International Journal of Cardiovascular Sciences. 2020; 33(3):263-271 Mailing Address: Alexandre Maulaz Barcelos R. Vênus, s/n - Industrial do Alecrim. Postal Code: 29118-300, Vila Velha, ES – Brazil. E-mail: alexandremaulazbarcelos@gmail.com QT Interval Dispersion Behavior in Patients with and without Obstructive Coronary Artery Disease Undergoing Exercise Test Alexandre Maulaz Barcelos, 1 M arcelo Perim Baldo, 2 S érgio Lamego Rodrigues, 2 J osé Geraldo Mill 2 CEAP - Centro de Ensino e Aperfeiçoamento em Pesquisa - Hospital Evangélico de Vila Velha, 1 Vila Velha, ES - Brazil Universidade Federal do Espírito Santo (UFES), 2 Espírito Santo, ES - Brazil Manuscript received on April 06, 2018; reviewed on July 02, 2019; accepted on July 30, 2019. 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. (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.