Diagnostic value of QT interval hysteresis loop in coronary artery disease

The dynamics behavior of QT interval as an effect of heart rate changes has not been clearly defined. Exercise ECG as diagnostic tool permits to notice physiologic changes in QT interval within a wide range of heart rates. The purpose of the present study is to characterize the QT interval behavior during the whole Exercise ECG procedure in previously diagnosed Coronary Artery Disease patients and normal volunteers. The sample was composed by a database obtained from a daily-performed procedure in the Hospital Universitario de Caracas. Signal acquisition and segmentation was carried out with a system developed in the authors´ laboratory. The study was based on parameters extracted from the observed hysteresis loop phenomenon, the area surrounded by this loop and fixed within the maximal and submaximal heart rates achieved by the patients. Results allow the authors to find by Wilcoxon-Mann-Whitney nonparametric test, an adequate ability of these parameters to discriminate evaluated groups