Beneficial effects of amiodarone pretreatment on early ischemic ventricular arrhythmias relative to infarct size and regional myocardial blood flow in the conscious dog.
The effects of chronic pretreatment with amiodarone on ischemic ventricular arrhythmias were evaluated in fully conscious instrumented dogs. In control dogs (n = 14) with large myocardial infarcts, early (first 30 min) ventricular arrhythmias occurred in a bimodal distribution with peaks at 3-5 min and at 12-25 min, with only the former associated with epicardial conduction delay. Ventricular fibrillation occurred equally frequently during each peak of early ventricular arrhythmias. Amiodarone (30 mg/kg daily) for 3-4 weeks had no significant effect (n = 11) on anatomic infarct size (28 +/- 6 vs. 30 +/- 5% of left ventricular weight) nor on collateral blood flow in the center of the infarct (19 +/- 11 vs. 15 +/- 7 ml/min/100 g of tissue) or on the ratio of endocardial/epicardial perfusion (0.23 +/- 0.19 vs. 0.28 +/- 19). Despite significant lengthening of peak epicardial conduction delay (191 +/- 20 to 239 +/- 81 ms, p less than 0.05), the frequency of early ventricular arrhythmias, especially during the second peak of ectopic activity, were markedly attenuated by amiodarone pretreatment, with the extrasystole-free intervals often being as long as 6 h. The incidence of ventricular fibrillation was 9% in the treated animals compared with 29% in the controls. In the control animals, arrhythmias always supervened when epicardial fractionation was significant, and no ectopy-free interval was present in the first 6 h following coronary occlusion. The data indicate that chronic amiodarone pretreatment exerts a beneficial effect on the frequency and severity of such ventricular tachyarrhythmias, with reduction in the incidence of ventricular fibrillation and ectopic activity in the early phases following coronary occlusion.
D000638:Amiodarone / Q000097:blood / Q000494:pharmacology*; D000818:Animals; D001145:Arrhythmias, Cardiac / Q000503:physiopathology*; D001572:Benzofurans / Q000494:pharmacology*; D002851:Chromatography, High Pressure Liquid; D003326:Coronary Circulation / Q000187:drug effects*; D003327:Coronary Disease / Q000503:physiopathology*; D003331:Coronary Vessels; D004285:Dogs; D004562:Electrocardiography; D005260:Female; D006439:Hemodynamics / Q000187:drug effects*; D008026:Ligation; D008297:Male
D001572:Benzofurans; D000638:Amiodarone