ELECTROPHYSIOLOGIC EFFECTS OF ISCHEMIC PRECONDITIONING ON QT DISPERSION DURING CORONARY ANGIOPLASTY

Objectives. The aim of this study was to examine the effect of ischemi c preconditioning on the manner of ventricular repolarization by asses sing the change in QT dispersion during coronary angioplasty. Backgrou nd. QT interval dispersion reflects regional variations in ventricular repolarization and cardiac electrical instability. Previous studies h ave suggested that increased QT dispersion is associated with an incre ased incidence of malignant ventricular arrhythmias, whereas brief epi sodes of myocardial ischemia can render the heart more resistant to su bsequent ischemic episodes, a phenomenon called ischemic preconditioni ng. Methods. To assess the effects of ischemic preconditioning on myoc ardial repolarization by examining the change in QT dispersion during coronary angioplasty, we studied 47 consecutive patients (39 men and 8 women; mean age 57 +/- 16 years). QT dispersion,vas measured after ea ch balloon inflation during coronary angioplasty. Statistical analysis was performed by using repeated measurement of analysis of variance. Results. There were significant differences in QT dispersion as the nu mber of balloon inflations increased (mean +/- SD 52 +/- 14 42 +/- 11, 36 +/- 9, 31 +/- 10 and 29 +/- 11 ms, respectively [p < 0.01], for th e first, second, third, fourth and fifth balloon inflations). The magn itude of decrease in QT dispersion was significant in the first and se cond balloon inflations, then became insignificant with later inflatio ns. Conclusions. These data indicate that the gradual decrease in QT d ispersion provoked by coronary artery occlusion and reperfusion during coronary angioplasty may be associated with electrophysiologic effect s of ischemic preconditioning on myocardium in the human heart.