Comparing the Changes in Ventricular Repolarization Parameters during the Exercise Test in Individuals with Positive and Negative Exercise Test Results

Although the changes in QT interval during and after exercise have been frequently investigated, the variations in the ventricular repolarization parameters during the exercise test have not been clearly evaluated. The present study aimed to assess the changes in these electrocardiographic (ECG) parameters as one of the main helpful criteria for interpreting the exercise test results. Forty-four suspected patients with a positive exercise test were considered as the case group and 25 with a negative exercise test were selected as the control group. All the participants were subjected to the treadmill stress test, which was performed according to the Bruce Protocol. In both groups, the changes in QT interval remained insignificant. QT dispersion was increased in 45.5% of the cases and in 28.0% of the controls, whereas this parameter was reduced in 34.1% of the cases and in 64.0% of the controls. Among the myocardial repolarization parameters in the case group, positive QT dispersion was more observed at recovery time than at rest (6.8% vs. 22.7%; P=0.004), while delta QT interval and QT dispersion ratio were adversely reduced at recovery time compared with resting. In the control group, the changes in all the parameters remained unchanged following exercise testing. Myocardial repolarization parameters exhibited different behaviors following exercise testing in both suspected ischemic and healthy conditions. The increase in QT dispersion, but an adverse decrease in QT dispersion ratio and delta QT interval, can be considered valuable parameters for discriminating ischemic from normal conditions.