Changes in myocardial norepinephrine in Indian domestic pigs after two-stage coronary ligation

Acute myocardial ischaemia in the anaesthetised pig: local catecholamine release and its relation to ventricular fibrillation

In anaesthetised open-chest pigs, sequential myocardial samples were obtained before and after occlusion of the distal half of the LAD. These samples were analysed histofluorimetrically to determine the density of catecholamine containing neurones in each sample (quantified morphometrically), and radioenzymatically for total tissue noradrenaline content. Following coronary artery occlusion, 75% of the animals (24 out of 32) died in ventricular fibrillation in the first 30 min, the other 25% (8/32) survived the first 60 min of myocardial ischaemia. Coronary artery occlusion led to a significant reduction in the density of fluorescing fibres in the ischaemic myocardium of animals which fibrillated (from 1.25 +/- 0.2% to 0.67 +/- 0.10% at 15 min) whereas in the survivors there was no significant change in fluorescing area during the course of the experiment. Animals which fibrillated had a significant reduction in tissue noradrenaline concentration of the ischaemic myocardium (from an initial concentration of 612 +/- 72 to 402 +/- 64 ng/g ww) within the first 5 min of ischaemia. It is concluded that in this model of myocardial ischaemia, the development of ventricular fibrillation in the early phase seems to be related to the release of noradrenaline from the sympathetic neurones after the onset of myocardial ischaemia.

Antiarrhythmic effect of aprindine on several types of ventricular arrhythmias

The antiarrhythmic effect of aprindine was compared with those of lidocaine and propranolol on several ventricular arrhythmias-epinephrine arrhythmias in cats, ouabain arrhythmias in cats and guinea pigs, ischemic ventricular arrhythmias in coronary-ligated Beagle dogs. Antiarrhythmic effects of aprindine and lidocaine were observed both in ouagain and ischemic arrhythmias, but not in epinephrine arrhythmias. While propranolol had a strong antiarrhythmic effect against epinephrine and ouabain arrhythmias, it did not increase sinus beats in ischemic arrhythmias. Marked anti-arrhythmic effects of aprindine in ischemic arrhythmias were observed in dogs using either single intravenous administration (4 mg/kg) or intravenous infusion (200 mug/kg/min, 2 mg/kg). Antiarrhythmic activity of aprindine is considered to be about twice as strong as that of lidocaine, but lidocaine is less toxic in experimental animals.