Influence of the adrenal medulla on cardiac rhythm disturbances following acute coronary artery occlusions.

The present study was designed to examine the relationship between epinephrine secreted from the adrenal medulla and acute occlusion of the left anterior descending (LAD) coronary artery in alpha-chloralone-anesthetized cats. Occlusion of the LAD artery produced arrhythmia in all of the animals, with 39% developing ventricular fibrillation (VF). Epinephrine content in the adrenal venous blood increased 5-fold immediately after occlusion and was associated with the development of arrhythmia and VF. The adrenal venous epinephrine levels increased 8-fold after occlusion in the animals that developed VF while, in those that did not develop VF, the epinephrine levels increased only 1.5-fold. Bilateral ligation of the adrenal veins 1 hour prior to occlusion of the LAD artery did not alter the pattern of development of arrhythmia but prevented the occurrence of VF. Pretreatment of animals with either practolol or sotalol 15 min prior to LAD artery occlusion also did not affect the occurrence of arrhythmia but prevented the incidence of VF. The data indicate that acute occlusion of the LAD coronary artery produces a sharp rise in epinephrine from the adrenal medulla and that epinephrine is a major factor in producing VF but does not seem to be involved to any great extent in the production of less ominous ventricular arrhythmias.