| Abstrakt: |
Infarction of the interventricular septum of the dog's heart by ligation of the front septal branch of the left coronary artery was successfully produced in 4 of 28 animals. The changes involved from one to two-thirds of the surface of the left side of the septum, and about one-tenth of the right. The infarct was widest about 1 cm. below the attached margin of the aortic cusps, its edges jagged, though well defined, and tapering in the direction of the apex. In one heart, 10 days after operation, the course of the left branch of the bundle of His was plainly visible just beneath the endocardium and over the infarcted muscle. Roughening or other alteration of the lining of the cavities of the heart was not observed.Microscopically the tissues immediately beneath the endocardium, including the Purkinje fibers of the bundle, were unaltered, but the subjacent muscle had undergone coagulation necrosis and was in varying stages of organization, according to the age of the lesion. Approximately one-tenth of the A-V node was involved in the infarction, regions of varying size disseminated irregularly throughout the node.There was no auriculo-ventricular dissociation demonstrated in post-operative electrocardiograms, and no significant irregularity in rhythm noted by other methods. The earliest after operation that an initial post-operative electrocardiographic tracing was made was 2 days, the latest, 10 days; a transient effect on the rhythm may have escaped recognition.It seems probable that obstruction of the septal branch of the left coronary artery in the dog does not produce permanent dysfunction of the A-V node or the His bundle. The endocardium and tissues immediately beneath it, including part of the conduction system, may have received nourishment by seepage of blood in the same direct way that the inner lining of some of the arteries is nourished. |
