Reverse use-dependent QT prolongation during infusion of nifekalant in a case of recurrent ventricular tachycardia with old myocardial infarction

Pure class III antiarrhythmic agents cause reverse use-dependent QT prolong ation Nifekalant is a new class III antiarrhythmic agent and blocks rapid c omponent of the delayed rectifier K+ current (Ikr) selectively. To prevent recurrent ventricular tachycardia in a patient with old myocardial infarcti on, nifekalant was administered by continuous intravenous infusion. There w as little variation in the blood level of nifekalant during the 1-day perio d, but the QTc interval became shorter with an increase of the heart rate e arly in the morning. It is therefore considered advisable to monitor the he art rate and QTc interval during administration of nifekalant by continuous intravenous infusion.