Abstract
In order to study on the morphological factors concerning of the mechanism of appearance of ischemic heart diseases without atherosclerosis, the coronary arteries of the dogs were observed histologically. The following results were obtained . 1 ) Peculiar annular folds were found perpendicular to the blood stream in the main branch of the coronary artery in all 50 adult dogs except 5 young dogs. 2) At the folded portion, the internal elastic lamina was interrupted or deficient and the arrangement of the smooth muscle cells was irregular. 3) The smooth muscle cells of the media at the fold were shrinked to become polygonal after injection of vasopressin and electrical stimulation of the stellate ganglion. 4) There were no findings of atherosclerosis at the folded portion. 5) The folds occurred often at the left circumflex artery. The fact that the internal elastic lamina was interrupted or deficient at the folded portion will be a factor for inducing coronary sclerosis in the future, as a result of increased vascular permeability. Injection of vasopressin into the coronary artery and electrical stimulation of the stellate ganglion induced marked deformity of the smooth muscle cells of the media at the folded portion of the coronary artery. Therefore, it is considered that the existence of the folded portion is related to the increased incidence of local spasm of the coronary artery. The folds were observed mainly at the main branch of the coronary artery, and the location of the folds was exactly in accordance with that of coronary sclerosis and coronary vasospasm in men. From these facts the folds seem to be important as an anatomical factor for the occurrence of ischemic heart diseases.
