Morphological changes in endocardium subjected to global ischaemia.

To provide insight into the effects of severe ischaemia on endocardium, the sequence of morphological changes which develop in the endocardium of the isolated rat heart subjected to 0-12 hours of global ischaemia at 37 degrees C was examined. A progression of changes occurred. Following one or more hours of ischaemia crater-like depressions and blebs appeared on the luminal surfaces of ventricular endothelial cells, with margination and clumping of nuclear chromatin, loss of glycogen granules, swelling of mitochondria, and the development of subendothelial membrane-bound dilatations of myocytes. Following two or more hours of ischaemia there was progressive separation of endothelial cells along their intercellular boundaries and desquamation of an increasing proportion of these cells. In regions of desquamation the surface was initially smooth due to persistence of the lamina densa of the basal lamina, but after longer periods of ischaemia the surface became rough with exposure first of the subendothelial connective tissue fibres (4 hours) and eventually of cardiac muscle cells (12 hours).