Evaluation of QT interval and QT dynamics in healthy male adults following isotonic and isometric exercise

Introduction: Electrocardiogram can be used an objective tool to assess cardiovascular response to physical exercise. The QT interval in ECG denoting ventricular depolarization and repolarization is particularly important in this regard as any change in its duration is known to be associated with arrhythmia. Studies reporting a change in QT duration in the post exercise period have variable results. Cardiac repolarization normally adapts to heart rate; therefore, various rate correction formulas have been used to calculate the corrected QT interval or QTc. Of these Bazzet’s formula and Fridericia formula are commonly used. These correction formulas are best suited for steady state conditions only. Hence, QT dynamics may be a better measure of QT dependence on heart rate in the post exercise period. Objectives: The aim of the study was to assess changes in QT interval and QT dynamics in healthy male adults following isotonic and isometric exercise. Materials and Methods: The study was conducted in 30 healthy male subjects. Temporal sequence of QT interval and QT dynamics before and after both isotonic and isometric exercise were measured. QT dynamics was assessed by linear regression analysis method. Results: The QTc calculated with standard rate correction formulae showed inconsistent values in the post exercise period. The slope of QT-RR relationship increased especially following isotonic exercise. Conclusion: QT interval duration increases following exercise, although, the degree of change is different for isotonic and isometric exercise.