Amiodarone and QTc Interval Dispersion in the Acute Myocardial Infarction

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Abstract

Background QTc dispersion (defined as the difference between the maximal and the minimal QTc intervals in any of 12 surface electrocardiograhic leads) has been suggested as an index of heterogeneity of repolarization within the ventricles. It has been found that QTc dispersion is increased in patients suffering from serious arrhythmic events as compared with those without them. The effect of amiodarone on QTc dispersion has not been reported yet in patients with an acute myocardial infarction. Methods QTc dispersion was measured in 193 patients (144 men, 49 women; mean age 61 ± 12 years old) in the early stage of an acute myocardial infarction. All patients belonged to the ongoing GEMICA trial which is a multicenter, double-blind, placebo controlled study of amiodarone administration (9.9 grams of intravenous and oral amiodarone in the first 10 days of the acute stage). QTc intervals were measured in at least 10 leads of the surface ECG at10 ± 6 days after the onset of infarction. Results The mean RR interval in the amiodarone group was significantly greater (961 ± 175 msec) than in the placebo group (876 ± 160 msec); p < 0.0005. When the maximal QTc and QTc dispersion were analized, taking into account the location of the infarction, Killip-Kimball class and any associated drug treatment, no significant differences were found be-tween the amiodarone and placebo groups. The same was found when the maximal QTc dispersion were compared in both groups as a whole. To be noted, QTc dispersion was significantly greater in anterior wall myocardial infarction. Conclusions The results of this study showed that abnormal QTc dispersion during acute phase of myocardial infarction was not modified by high doses of amiodarone. If an increase of QTc dispersion may have proarrhythmic effects, our findings strongly support the hypothesis that amiodarone can be safely used as antiarrhythmic under these circumstances.