“Experimental myocarditis. A study of the histological changes following intravenous injections of adrenalin” 1

Intravenous injections of adrenalin in doses of one-tenth cubic centimeter, soon raised to five-tenths and given on alternate days, cause, in addition to lesions of the aorta, degenerative changes in the myocardium which are most marked after the fifth injection. The majority of the animals (rabbits) which recover from the early injections exhibit a fibrous myocarditis either focal or diffuse. These proliferative changes are not analogous to those occasionally produced experimentally by bacterial toxins, but resemble rather those following obstruction of the coronary arteries. It is essentially a process of repair following degeneration of muscle fibers. The latter is due apparently to temporary ischemia of terminal vascular territories at a time when the heart muscle exerts an increased contractile effort necessary to overcome the greatly augmented intra-vascular tension. Thus both nutritive and mechanical disturbances appear to play a part in its etiology.