The relation of QT dispersion to spontaneous ventricular arrhythmias during the acute phase of myocardial infarction

Background: QT dispersion is associated with ventricular arrhythmias and sudden death among patients with a previous myocardial infarction (MI). The relationship between QT dispersion and ventricular arrhythmias during the acute phase of MI is uncertain. Methods: Patients enrolled in the Multicenter Study of Silent Myocardial Ischemia who had first Q wave myocardial infarctions (n = 363) were screened for the presence of ventricular arrhythmias during the initial hospitalization. Twelve patients had ventricular fibrillation, and 18 patients had an episode of monomorphic ventricular tachycardia. Each patient who had ventricular arrhythmias was matched with four controls on the basis of age, peak creatine kinase, thrombolysis, and the presence of congestive heart failure. The final study population consisted of 150 patients: 12 patients with ventricular fibrillation (VF+) who were compared to 48 controls (VF-), and 18 patients with ventricular tachycardia (VT+) who were compared to 72 controls (VT-). The RR, QRS, and QT intervals were measured manually using standard 12-lead ECGs (25 mm/s) obtained after hospital admission. The maximal QT dispersion (maximum - minimum value) was calculated. Multivariate logistic regression analysis was performed to determine if QT dispersion was independently associated with ventricular arrhythmias during the acute phase of MI. Results: QT dispersion was significantly greater in VF+ patients compared to VF- patients (89 ± 18 ms vs 66 ± 22 ms, P < 0.01). QT dispersion was similar in VT+ and VT- patients (68 ± 25 ms vs 68 ± 26 ms, P = NS). QT dispersion was the only variable that was independently associated with ventricular fibrillation (OR 1.7 for each 10-ms increment in QT dispersion; 95% CI 1.2-2.6; P = 0.008). QT dispersion was not associated with monomorphic ventricular tachycardia (OR 1.0; 95% CI 0.8-1.2; P = NS). Conclusion: QT dispersion is independently associated with ventricular fibrillation, but not monomorphic ventricular tachycardia, during the acute phase of MI.