Abstract

CRUDO, Norma et al. The Analysis of the Corrected QT-Interval Increases Exercise Stress Test Capability to Detect Significant Coronary Artery Disease. Rev. argent. cardiol. [online]. 2014, vol.82, n.6, pp.512-518. ISSN 1850-3748.

Background: The clinical usefulness of exercise stress testing to indicate the presence and functional severity of coronary artery stenoses is limited by the relatively low sensitivity and specificity of ST-segment depression. Therefore, the modifications of other electrocardiographic variables during exercise, which may provide additional and complementary information to ST-segment depression, should be investigated. It has been demonstrated that the corrected QT interval (QTc) prolongation is the earliest event during the first stage of transmural ischemia. Objectives: The aim of this study was to investigate whether modifications of the QTc interval induced by maximal exercise (QTcmax) together with ST-segment depression ≥ 1 mm can increase the capability of the stress test to detect significant coronary artery disease and if other signs may also provide useful information to identify these patients. Methods: One hundred and sixty six patients with ST-segment depression ≥ 1 mm during exercise or during the recovery stage of a stress test underwent coronary angiography. They were divided into two groups: Goup I (GI): 118 patients with QTcmax interval prolongation and Group II (GII): 48 patients with normal QTcmax shortening. Clinical, stress test-related and electrocardiographic parameters and coronary angiography were analyzed to identify the presence of significant coronary artery disease. Results: Significant coronary artery disease was detected in 102 of the 166 patients included in the study (61.4%), all from GI. Group I showed high prevalence of patients with significant coronary artery disease (86.4% vs. 0%; p < 0.001), low ischemic threshold, late recovery of ST-segment depression, wider QRSmax complex, chronotropic incompetence and low exercise capacity. During graded exercise stress testing, GII patients presented greater prevalence of severe hypertension and ST-segment depression < 1 mm two minutes after exercise. Increased QTcmax interval resulted as an independent predictor of coronary artery disease (p < 0.001). Conclusions: QTcmax interval prolongation plus ST-segment depression ≥ 1 mm produced a considerable increase in the capability of exercise stress testing to detect significant coronary artery disease, which was absent in all the patients with ST-segment depression and normal QTcmax shortening.

Keywords : Exercise Stress Test; QTc Interval; ST-segment Depression.

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