QT dispersion during dobutamine stress J echocardiography as an index for l myocardial viability in patients with old c myocardial infarction

Abstract

QT dispersion and myocardial viability have been associated with the presence of arrhythmias during late post infarction period. Restoration of anterograde coronary flow has beneficial effects on ventricular systolic function and repolarization suggesting that the extent of viable myocardium may determine ventricular repolarization. This study sought to investigate the relationship of myocardial viability detected by dobutamine stress echocardiography to changes of QT dispersion and to the presence of arrhythmias during dobutamine infusion in patients with old myocardial infarction. Thirty patients with previous myocardial infarction (one of them was excluded for difficulty in differentiation between T and U wave) were studied in a low dose (up to 10 mug/Kg/min) dobutamine stress echocardiography study. ECGs were obtained at rest and peak stress for measurement of QT dispersion. The presence of ventricular arrhythmias, ST segment elevation and chest pain during stress were noted. Patients with myocardial viability showed positive correlation and significant statistical difference as regard percent reduction of wall motion score (P<O.OOI), number of segments improved after dobutamine infusion (P < 0.001) and percent increase of ejection fraction after dobutamine infusion (P < 0.001). Those patients also showed a greater increase in the percentage of QT dispersion with a significant P-value of