Endothelial cells of the cardiac microvasculature during and after cold cardioplegic ischaemia: Comparison of Endothelial and Myocyte Damage

Abstract

Ultrastructural changes in endothelial cells of the myocardial microvasculature were studied in 18 patients who underwent aortocoronary bypass surgery under cold ischaemic cardioplegia. Biopsy specimens for electron microscopy were taken from the right atrium before and at the end of aortic cross-clamping and after 20 and 60 min of reperfusion. At the end of the cold ischaemic cardioplegia, the endothelial cells showed reduced numbers of pinocytotic vesicles, moderate intracellular oedema and slight nuclear changes. During reperfusion the endothelial changes became more pronounced and interstitial oedema developed. These changes persisted, or even increased in the first 60 min of reperfusion, in contrast to the myocytic changes, which tended to regress. The endothelial cells of the myocardial microvasculature thus appeared to be more vulnerable than the myocytes to cold ischaemic cardioplegia and reperfusion. Focally reduced blood reperfusion due to endothelial swelling and interstitial oedema did not seem to be the main cause of the focal postischaemic myocytic damage.

Key Words:

• cardioplegia
• myocardial microvascular endothelium