Dispersion of ventricular repolarization is determined by the presence of myocardial viability in patients with old myocardial infarction - A dobutamine stress echocardiography study

Aims The study sought to investigate the relationship of myocardial viabili ty detected by dobutamine stress echocardiography to changes of QT dispersi on and to the presence of arrhythmias during dobutamine infusion in patient s with old myocardiaI infarction. We also examined whether patency of the i nfarct-related artery is associated with the presence of myocardial viabili ty and QT dispersion. Background QT dispersion and myocardial variability have been associated wi th the presence of arrhythmias during late post infarction but not during d obutamine stress. Restoration of anterograde coronary how has beneficial ef fects on ventricular systolic function and repolarization, suggesting that the extent of viable myocardium may determine ventricular repolarization. Methods Seventy five patients with previous myocardial infarction were stud ied in a low dose (up to 20 mu g(-1). kg(-1) min(-1)) dobutamine stress ech ocardiography study. ECGs were obtained at rest and peak stress for measure ment of QT intervals. The presence of ventricular arrhythmias (Lown grade > 1b) during stress was noted. A reduction in the total wall motion score of the left ventricle at peak stress confirmed the presence of myocardial viab ility. Results Dobutamine infusion increased QT dispersion in all patients (P<0.01 ). Patients with myocardial viability had a lower resting QT dispersion (P< 0.05) and a greater increase in QT dispersion% (P<0.01) than patients witho ut. The combination of a resting QT dispersion <65 ms or an increase in QT dispersion >30% predicted viability with a sensitivity of 67%, a specificit y of 96%, and an accuracy of 78%. A patent infarct-related artery, as well as ventricular arrhythmias, were more commonly observed in patients with ev idence of viable myocardium (p<0.05). Patients with arrhythmias had a highe r QT dispersion than patients without (P<0.05). Conclusion The combination of a resting QT dispersion +/- 65 ms or an incre ase in QT dispersion >30% predicts the presence of viable myocardium and th us, may represent a simple index for the assessment of viability in everyda y clinical practice. Myocardial viability is related to a patent coronary a rtery and to a high incidence of arrhythmias accompanied by a greater incre ase in QT dispersion at peak dobutamine infusion. (C) 2000 The European Soc iety of Cardiology.