Background:

Exercise tests are usually used for diagnosis of cardiac abnormalities. ST segment depression reflects myocardial ischemia and ventricular repolarization dispersion is used as a risk factor. The aim of this study was to evaluate the kinetics of QT dispersion (QTd) during exercise and recovery from 12-lead electrocardiogram depending on ST depressions (STd).

Method:

Thirty six patients performed a treadmill incremental test followed by 6-min of recovery with 12-leads ECG recording each minute. Two groups of patients were defined according to STd criteria: Positive (STd <= -1 mm., n = 23), Control (high cardiovascular risk factor patients without STd, n = 13). Ventricular repolarization modifications were assessed by QTd, standard deviation of the 12-leads and QTd normalized by QT mean.

Results:

All parameters of ventricular repolarization increased significantly according to exercise level (P <= 0.0001) without significant differences between groups. Moreover, all ventricular repolarization parameters decreased deeply during recovery (P <= 0.001). Finally, at the end of recovery the values of ventricular repolarization were shorter than during the resting period (P <= 0.001).

Conclusion:

Acute exercise induced a sharp decrease of QTd during the recovery whatever the ST segment depression. These results may explain the positive impact of exercise training on QTd.