INCREASED QT DISPERSION IN PATIENTS WITH VASOSPASTIC ANGINA

Background-The risk factors for ventricular arrhythmias in patients wi th coronary vasospasm have not been identified. We evaluated QT disper sion in patients with vasospastic angina and its relation to susceptib ility to ventricular arrhythmias during myocardial ischemia and reperf usion. Methods and Results-We assessed the corrected QT (QTc) dispersi on before induction of coronary artery spasm by intracoronary injectio n of acetylcholine (baseline) and 30 minutes after administration of i sosorbide dinitrate in 50 patients with vasospastic angina and 50 pati ents with atypical chest pain. The baseline QTc dispersion was signifi cantly greater in patients with vasospastic angina than in patients wi th atypical chest pain (mean+/-SD: 69+/-24 versus 44+/-19 ms, 95% conf idence interval of mean difference [CI]: 16 to 33 ms; P<0.001). QTc di spersion decreased significantly, to 48+/-15 ms (CI: 15 to 26 ms; P<0. 001 versus baseline), after administration of isosorbide dinitrate in patients with vasospastic angina but did not change significantly in p atients with atypical chest pain (mean+/-SD: 41+/-17 ms, CI: -3 to 9 m s). During the provocation test, 24 of 50 patients with vasospastic an gina experienced ventricular arrhythmias. The baseline QTc dispersion was significantly greater in patients with than without ventricular ar rhythmias (mean+/-SD, 77+/-23 versus 61+/-19 ms, CI: 4 to 26 ms; P<0.0 5). Conclusions-Patients with vasospastic angina exhibited an increase d baseline QTc dispersion compared with patients with atypical chest p ain, which suggests that inhomogeneity of repolarization and susceptib ility to ventricular arrhythmias are increased in patients with vasosp astic angina, even when asymptomatic. The association between increase d QTc dispersion and ventricular arrhythmias during the provocation te st suggests that measurement of QT dispersion may help predict which p atients with vasospastic angina are at high risk for ventricular arrhy thmias during ischemia.