[Ultrastructural and histochemical criteria of myocardial hypoxia and a morphological assessment of the various methods for its protection (based on biopsy data of the human heart)].

Short-term ischemia (up to 10 minutes) induced by clamping of the aorta in correction of a ventricular septal defect causes no essential ultrastructural, metabolic or functional changes in the myocardium. In much longer period of ischemia (of up to 40 minutes) during operation for congenital heart diseases, the use of deep hypothermia is effective. Cold cardioplegia is a sufficiently reliable method for myocardial protection when the aorta is clamped for up to 60 minutes in operations for acquired heart diseases.