Light and electron microscopic observations of the myocardium of dogs in hemorrhagic shock.

Abstract

Morphologic change of the myocardium of the dog were observed in oligemic and normovolemic shock produced by Wiggers' standard method.Subendocardial hemorrhages, usually superficial and located mostly in the ventricular aspect of the septum, were remarkable in the normovolemic shock group, but rare in the oligemic shock group. The zonal lesion appeared in the early period of oligemic shock becoming more apparent with lapse of time. Ultrastructural studies revealed some differences of the findings of the zonal lesion between oligemic and normovolemic shock. In oligemic shock, the zonal lesion was identical to the supercontraction of myofilaments and dislocation of mitochondria. Supercontraction of myofibrils was usually unilateral, and herniation of damaged myocytes was frequently noticed in the unilateral lesion. In the normovolemic shock, supercontracted areas near the intercalated disc were usually stretched and the myofilaments became irregular in arrangement. In addition, the accumulation of glycogen granules and presence of clear flocculent areas were observed in the cytoplasm of some myocardial cells.Cell edema, swelling and destruction of mitochondria and contraction bands were found in the damaged myocyte, especially in the terminal stage of normovolemic shock. Swelling of the capillary endothelial cell was already observed in the early period of oligemic shock. In addition, the pathogenesis of the zonal lesion and the mechanism of cardiac depression in hemorrhagic shock were discussed.