Programmed electrical stimulation in conscious dogs: electropharmacologic testing of amrinone

In order to assess possible proarrhythmic properties of amrinone, serial programmed electrical stimulation was performed via several previously implanted electrodes in 12 conscious dogs during the late reperfusion phase following experimental myocardial infarction. In 6 dogs, programmed electrical stimulation was carried out before and following the administration of amrinone (Wincoram) at cumulative doses of 0.3, 1 and 3 mg/kg, i.v., while the rest served as control group and received matching volumes of saline. Amrinone decreased atrioventricular refractoriness but did not alter ventricular refractory periods in both normal and infarct zones. Amrinone (3 mg/kg) substantially enhanced intraventricular conduction. Induction of ventricular arrhythmias was attempted only at base line and following 3 mg/kg of amrinone. Inducibility was unaltered by amrinone. However, in two experiments we observed more severe forms of arrhythmia to be inducible following drug administration. The number of extrastimuli necessary for the induction of arrhythmias was decreased in two cases during treatment. In the control group, neither the nature of induced arrhythmias nor the number of extrastimuli was changed. We conclude that, in our model, amrinone exerts a moderate proarrhythmic effect when assessed by programmed electrical stimulation. This arrhythmogenic property may be due to an enhancement of intraventricular conduction.