Ectopic ventricular rhythms and myocardial infarction in the domestic pig and their response to nialamide, a monoamine oxidase inhibitor.

The development in Indian domestic pigs of ectopic ventricular rhythms and a low-frequency tachycardia after the two-stage ligature of the anterior descending branch of the left coronary artery is described. When the ligature was tied 26+/-3 mm from the left auricular margin, the change in rhythm developed after 2 to 2.5 hr, reached a maximum after 6 hr and persisted up to 28 hr. The histopathological character of the resultant acute myocardial infarction is presented. In all, 52 pigs were used. Pretreatment of 9 pigs, with 3 as controls, with a monoamine oxidase inhibitor, nialamide, 20 mg/kg daily for 2 to 4 days, suppressed the development of experimental ventricular arrhythmia and favourably influenced the ischaemic myocardium by reducing the oedema and the formation of microthrombi. A possible mode of action involving monoamine oxidase inhibition is suggested.