Electron microscopic evaluation of the degree of ischemic injury in diseased human hearts is a very useful tool in estimating the quality of any method of myocardial preservation. Ultrastructural alterations give accurate data in the clinical setting. Our semiquantitative scoring system was created considering existing evaluation systems and based on our own observations. Eight grades of ischemic injury were defined, ranging from 1 (normal ultrastructural appearance) to 8 (irreversible ischemic damage) with respect to integrity and swelling of mitochondria, nuclei, myofilaments, membranes, organelles and components, as well as extracellular structures.