Effect of Exercise and Dobutamine Stress Test on QT Dispersion in Patients with Coronary Heart Disease

Interderivational QT variability on 12-lead electrocardiography (ECG) is defined as QT dispersion (QTd), and it is accepted that this dispersion reflects regional variability of ventricular repolarization. In the present study symptom-limited maximal treadmill exercise testing and dobutamine stress echocardiography (DSE) (maximum 40g/kg/min) were performed in 28 cases in whom major coronary artery stenosis of more than 50% was established by coronary angiography. In cases with or without myocardial ischemia the relationship between QTd was investigated. While the difference between QTd which was measured at rest and peak exercise in cases who had ischemia during exercise test was significant (p<0.05), no significant difference was observed in cases without ischemia. Moreover, a significant difference was established between QTd before and during maximum dobutamine infusion in cases with ischemia during DSE, whereas there was no significant difference in cases without ischemia. Hence, in stress tests performed by pharmacological and nonpharmacological agents, QTd values increased in patients with ischemia but there was not any significant difference between the methods used.