Ultrastructural consequences of reperfusion of the ischaemic myocardium.

Ultrastructural changes following ischaemic myocardial injury have been investigated in dogs. After 15 to 120 min global normothermic ischaemia the hearts were reperfused in a special heart-lung model for 60 min and then subjected to electron microscopic examination. The degree of morphological alterations and the duration of ischaemia were approximately interrelated. The ischaemic hearts showed characteristic changes such as mitochondrial, sarcolemmal and myofibrillar defects (swelling, disruption of cristae, loss of matrical density and contractile bands, myofibrillar rupture and lysis, blurred Z-lines). The hypercontractions are no artifacts but consequences of irreversible cellular injury and the observed stiffness during reperfusion is a good marker of the myocardial damage suffered.