The prognostic value of QTc interval and QT dispersion following myocardial infarction in patients treated with or without dofetilide

Background: Acute myocardial infarction (MI) is associated with an increased risk of death, with a I-year mortality close to 10% in patients discharged from hospital alive. During the first year following MI, close to 50% of deaths are assumed to be due to arrhythmic events. Hypothesis: The study was undertaken to determine the interaction between dofetilide treatment and pretreatment QTc interval and QT dispersion regarding mortality in patients with left ventricular (LV) dysfunction and a recent MI. Methods: The study population consisted of 894 patients with a recent MI and LV systolic dysfunction, who were randomized to receive dofetilide or placebo. The study was a substudy of the Danish Investigations of Arrhythmia and Mortality on Dofetilide-MI (DIAMOND-MI). Results: During a minimum of 1-year follow-up, 261 (29%) patients died. Baseline QTc interval did not hold any prognostic value on mortality for placebo-treated patients. When pretreatment QTc interval was < 429 ins, dofetilide resulted in a 45% reduction of mortality (hazard ratio 0.55, 95% confidence limits 0.34-0.88, p < 0.02) compared with placebo. When QTc interval was > 429 ms, dofetilide did not influence mortality significantly. This study revealed no statistically significant relation between QT dispersion dofetilide treatment, and mortality. Conclusion: In patients with a recent MI, LV dysfunction, and a short baseline QTc interval, dofetilide is associated with significant survival benefit. This benefit is not seen with a longer QTc interval. QT dispersion is not a risk factor in this population.