Ultrastructural changes of the myocardium in regional ischaemia and infarction.

This study describes ultrastructural changes observed in experimental myocardial ischaemia and infarction in the dog heart. In myocardial cells, the evaluation of the state of mitochondria, nuclei and myofilaments by electron microscopy allows the differentiation of reversible versus irreversible ischaemic injury. Other subcellular symptoms such as glycogen loss, lipid deposition or occurrence of cytoplasmic proteinous substances are indicative of metabolic disturbances in ischaemia. The microvasculature shows degenerative as well as regenerative processes; a close interaction of the endothelium with platelets and leucocytes is evident. The extravascular space shows necrosis of interstitial cells as well as proliferation indicating early preparations for scar formation. Blood cells in the tissue are found to be typical of an early unspecific inflammatory response. Regional ischaemia seems to provoke a whole cascade of events on the subcellular level which are apparently closely linked with each other.