A comparison of the QT and QTc dispersion among patients with sustained ventricular tachyarrhythmias and different etiologies of heart disease

Objectives: To determine if etiology of heart disease is associated with differences in QT and QTc dispersion among patients with ventricular tachyarrhythmias. Methods: This study was undertaken in 145 patients undergoing electrophysiological testing for sustained ventricular tachycardia or ventricular fibrillation. Patients were divided into groups based on etiology of heart disease determined by history, ECG, coronary angiography, and echocardiography. The groups included patients with: dilated cardiomyopathy (n = 29), myocardial infarction (n = 90), established coronary artery disease without a myocardial infarction (n = 11), or hypertension induced left ventricular hypertrophy (n = 15). The QT intervals on a 12-lead ECC were determined and Bazett's formula was used to derive the QTc intervals. The QT and QTc dispersion were determined by subtracting the shortest QT(c) interval from the longest on each 12-lead recording. Results: The patients with dilated cardiomyopathy had significantly higher QT and QTc dispersion values as compared to any of the other three groups (P < 0.05 for both). No other differences in electrocardiographic variables were found between groups. Conclusions: In a group of patients with a history of ventricular tachycardia or ventricular fibrillation, QT and QTc dispersion are significantly greater among patients with dilated cardiomyopathy than for patients with a previous myocardial infarction, established coronary artery disease without a myocardial infarction, or hypertensive left ventricular hypertrophy.