Relation of QT dispersion in sinus beats and ventricular premature beats with myocardial ischemia induced by exercise stress echocardiography in patients with ventricular arrhythmias

Abstract Background QT dispersion (QTd) is a measure of inhomogeneous repolarization of myocardium. Abnormally high QTd has been correlated with risk of cardiac death in coronary patients. Corrected QT dispersion, commonly measured in sinus beats (QTdc-S), can also be calculated in premature ventricular beats (QTdc-V). Prolonged QTdc-V is associated with a significantly increased risk for arrhythmic events in postinfarction patients, and the prognostic significance of QTdc-V exceeds that of QTdc-S. Purpose The aim of this study was to establish the relation of QT dispersion in sinus beats and ventricular premature beats with myocardial ischemia induced by exercise stress echocardiography (ESET) in patients with ventricular arrhythmias. Methods The study involved 157 patients with ventricular arrhythmias, average age 53.8 years. In all subjects clinical examination, standard ECG and exercise stress echocardiography, were performed. The criterion for myocardial ischemia was the appearance of transient segmental wall motion abnormality. The first ECG was done before the exercise stress echocardiography and the second one was done immediately after exercise, with calculation of QTdc-S and QTdc-V. Results During exercise stress echocardiography, in 58 (36.9 %) subjects wall motion abnormality occurred (group with myocardial ischemia: MI), and 99 (63.1 %) subjects were without ischemia (group without myocardial ischemia: NMI). Before starting the exercise stress echocardiography, MI group patients had significantly higher values of QTdc-S (57.4 ± 18.3 vs 41.4 ± 14.8 ms; p < 0.001) and QTdc-V (63.5 ± 19.2 vs 45.8 ± 17.6 ms; p < 0.001) in comparison to NMI group patients. During ESET there was a significant increase in QTdc-S (from 57.4 ± 18.3 to 88.5 ± 21.2 ms; p < 0.001) as well as QTdc-V (from 63.5 ± 19.2 to 90.8 ± 22.4 ms; p < 0.001) in MI group. In the NMI group there were no significant changes in the values of QTdc-S and QTdc-V during ESET. Conclusions Significant increase of QTdc-S and QTdc-V is associated with the occurrence of myocardial ischemia during ESET in patients with ventricular arrhythmias. This new diagnostic approach, of using QT dispersion, significantly improves the clinical usefulness of ESET in detecting myocardial ischemia in patients with ventricular arrhythmias. Assessment of QTdc-S and QTdc-V on standard ECG may be useful for identifying patients with coronary artery disease and those with possible serious ventricular arrhythmias.