EL ANÁLISIS DEL INTERVALO QT CORREGIDO INCREMENTA LA CAPACIDAD DE LA ERGOMETRÍA PARA DIAGNOSTICAR ENFERMEDAD ARTERIAL CORONARIA SIGNIFICATIVA;
The Analysis of the Corrected QT-Interval Increases Exercise Stress Test Capability to Detect Significant Coronary Artery Disease

Se ha demostrado que el evento más temprano en la primera fase de la injuria transmural es la prolongación del intervalo QT corregido (QTc). Objetivos Investigar si las modificaciones del intervalo QTc inducidas por el esfuerzo máximo (QTc Mx) sumadas al  infradesnivel del segmento ST (Infra ST) ≥1mm permiten incrementar la capacidad de la ergometría  para diagnosticar la presencia de enfermedad arterial coronaria (EAC) significativa y, si  otros signos  también pueden aportar información útil  para identificar a estos pacientes. Métodos 166 pacientes con Infra ST ≥1mm durante la fase de ejercicio y/ó recuperación de una  ergometría que se les realizó una coronariografía posterior fueron distribuídos en 2 grupos: Grupo I (GI): 118 pacientes que mostraron prolongación del intervalo QTcMx  y,  Grupo II (GII): 48 pacientes que acortaron normalmente el QTcMx.  Se analizaron parámetros clínicos, ergométricos y electrocardiográficos y la angiografía coronaria para comprobar la presencia de EAC significativa. Resultados En 102 de los 166 pacientes incluidos (61,4%) se diagnosticó EAC significativa, todos ellos pertenecientes al GI. El GI mostró alta prevalencia de pacientes con EAC significativa (86,4% vs 0%; p<0,001), bajo umbral isquémico, recuperación tardía del Infra ST, mayor ensanchamiento del complejo QRS Mx, incompetencia cronotrópica y baja tolerancia al ejercicio. Durante la PEG, los pacientes del G II presentaron mayor prevalencia de hipertensión arterial severa y el Infra ST < 1mm en el 2º min. del postesfuerzo. Conclusiones La prolongación del intervalo QTcMx sumado al Infra ST ≥1mm incrementó notoriamente la capacidad de la PEG para diagnosticar la presencia de EAC significativa, patología que estuvo ausente en todos los pacientes con  Infra ST que acortaron normalmente el QTcMx.

Background: The clinical usefulness of exercise stress testing to indicate the presence and functional severity of coronary arterystenoses is limited by the relatively low sensitivity and specificity of ST-segment depression. Therefore, the modifications ofother electrocardiographic variables during exercise, which may provide additional and complementary information to STsegmentdepression, should be investigated. It has been demonstrated that the corrected QT interval (QTc) prolongation isthe 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 significantcoronary 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 recoverystage of a stress test underwent coronary angiography. They were divided into two groups: Goup I (GI): 118 patients withQTcmax interval prolongation and Group II (GII): 48 patients with normal QTcmax shortening. Clinical, stress test-relatedand electrocardiographic parameters and coronary angiography were analyzed to identify the presence of significant coronaryartery 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 ischemicthreshold, 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 STsegmentdepression < 1 mm two minutes after exercise. Increased QTcmax interval resulted as an independent predictor ofcoronary artery disease (p < 0.001).Conclusions: QTcmax interval prolongation plus ST-segment depression ≥ 1 mm produced a considerable increase in thecapability of exercise stress testing to detect significant coronary artery disease, which was absent in all the patients withST-segment depression and normal QTcmax shortening.