Antioxidant vitamins decrease exercise-induced QT dispersion after myocardial infarction.

Background: Antioxidant vitamins C and E inhibit neutrophil-mediated production of free radicals in acute myocardial infarction (MI) which may limit MI size and improve myocardial perfusion.

Aim: To examine whether treatment with vitamin C and E reduces inhomogeneity of repolarisation in patients with acute MI.

Methods: In this double-blind, placebo-controlled randomised trial 37 patients with acute MI were enrolled and assigned to vitamin C and E (600 mg/day each) or placebo treatment, starting on the first day of acute MI and lasting for 14 days. Inhomogeneity of repolarisation was assessed by examining QT interval dispersion (QTd), measured both at rest and at the end of sub-maximal exercise test, performed before discharge.

Results: Baseline QTd was similar in both groups, however, exercise-induced QTd was significantly lower in patients treated with antioxidant vitamins compared with the placebo group (59 +/- 20 msec vs 74 +/- 24 msec, p<0.05).