ACUTE-ISCHEMIA - A DYNAMIC INFLUENCE ON QT DISPERSION

Background The aim of this study was to test the hypothesis that acute myocardial ischaemia increases QT dispersion measured from the 12-lea d electrocardiogram. Methods Incremental atrial pacing was used to ind uce myocardial ischaemia in 18 patients with coronary artery disease a nd QT dispersion was measured. Six patients with normal coronary arter ies served as the control group. Findings All the patients with corona ry artery disease developed angina and/or ST depression accompanied by marked increases in QT dispersion (mean increase 38 ms, 95% CI 30 to 45 ms, p<0.001). In contrast patients with normal coronary arteries wh o without symptoms and without ST changes, there was no significant ch ange in QT dispersion in response to pacing. Baseline QT dispersion di d not distinguish those patients with coronary artery disease from tho se with normal coronary arteries (44 ms [95% CI 39-49 ms] vs 40 ms [25 -55 ms]), respectively. Interpretation These results demonstrate that myocardial ischaemia induced by incremental atrial pacing in patients with coronary artery disease causes an acute increase in QT dispersion . Such ''inducible'' QT dispersion may prove more useful than resting QT dispersion in assessing the individual risk of arrhythmic events in patients with coronary artery disease.