ObjectivesClinical depression is a risk factor for cardiac mortality in patients with coronary heart disease. High QT interval variability is a risk factor for arrhythmic events, including sudden cardiac death. The purpose of this study was to determine whether depression is associated with increased QT variability in patients recovering from myocardial infarction.MethodsTwenty patients with major depression recovering from a recent myocardial infarction were matched with 20 nondepressed post–myocardial infarction patients on age and sex, and all underwent 24-hour Holter monitoring.ResultsThere were no differences between groups on average heart rate, heart rate variability, or other electrocardiographic measures. However, the QT interval showed significantly greater variability in the depressed than in the nondepressed group, especially at midnight and at 6:00 AM.ConclusionsDepressed post–myocardial infarction patients may be at greater risk for sudden cardiac death as a result of abnormalities in ventricular repolarization. More work is needed to determine the clinical and prognostic significance of QT variability in these patients.