Action of amiodarone over the extension and reversibility of experimental myocardial infarction in pigs.

The purpose of the present work is to evaluate the action of a benzofuran derivative, Amiodarone, on an experimental acute infarction model. Six pigs were intravenously administered 1 mg/kg Amiodarone (A) 20 minutes before inducing ischemia (I) by occlusion of the anterior descending coronary artery, which was maintained for 90 minutes. A similar dose level was repeated 20 minutes before ligation release (R). Similarly, another six animals received a placebo and formed the Control Group (C). The extent of myocardial injury was assessed by summations of ST segments (Sigma ST) and R (Sigma R) and Q (Sigma Q) waves of electrocardiographic epicardial mappings, as well as by serum levels for SGOT and LDH. Systemic blood pressure, pulmonary pressure, right atrial pressure, systemic resistance and cardiac output were also controlled. Two hundred and ten minutes after R, the animal was sacrificed for the purpose of carrying out morphological and histochemical studies. No significant differences were observed in the blood pressure of either group. During I, systemic resistance values suffered a drop in the Amiodarone Group A, whereas they increased in both groups after reperfusion. Pulmonary pressure was higher in Group A. Cardiac output showed a similar behavior in both groups up to R, when it significantly decreased in animals receiving Amiodarone. The Sigma ST and the Sigma Q were higher in the Control Group C, whereas the Sigma R was higher in Group A. The SGOT and LDH levels were higher during R in Group C. Histochemistry showed a higher activity for SDH and LDH in treated animals. Due to its action on afterload, its contractility and its direct myocardial action, Amiodarone limited the extent of necrosis and increased the recoverable amount of myocardium.