IN-VITRO EFFECTS OF CARDIOPLEGIC SOLUTIONS ON HUMAN SAPHENOUS-VEIN ENDOTHELIUM - A SCANNING ELECTRON-MICROSCOPY STUDY

In order to evaluate the effects of potassium cristalloid cardioplegic solutions (CPS) on the endothelial morphology, human saphenous veins were studied by scanning electron microscopy after exposure to three C PS named MKP (magnesium-potassium-procaine cardioplegia), LK (low-pota ssium cardioplegia), and HKA (high-potassium-albumin cardioplegia) and to their main components. Vein rings, selected from the saphenous vei ns sampled for graft harvesting in 63 patients undergoing aorto-corona ry bypass surgery, were exposed for 30, 60, and 120 minutes to the fol lowing buffered solutions: Krebs bicarbonate (as control); MKP cardiop legia; KCl (16.0 mmol/L); MgCl22 . 6H2O (16.0 mmol/L); Procaine (0.05 mmol/L); NaCl (92.5 mmol/L); LK cardioplegia; KCl (10.0 mmol/L); Manni tol (74.3 mmol/L); Glucose (27.7 mmol/L); HKA cardioplegia; KCl (30 mm ol/L). Severe endothelial lesions, consisting of diffuse disendothelia lization and diffuse signs of endothelial suffering, were induced by K Cl (30 and 16 mmol/L) after 60-120 min, and by MKP cardioplegia and KC l (10 mmol/L) after 120 min. Moderate endothelial lesions, characteris ed by diffuse endothelial surface changes and focal cellular loss, wer e induced by KCl (30 and 16 mmol/L) after 30 min, MKP cardioplegia and KCl (10 mmol) 30-60 min, LK cardioplegia, HKA cardioplegia, and MgCl2 . 6H2O after 120 min. Slight endothelial lesions, consisting of diffu se endothelial bulging, or absence of significant endothelial changes, were found in samples otherwise treated. Our findings showed a signif icant damaging effect of CPS on the human saphenous vein endothelium i n-vitro. The endothelial lesions seemed related to the presence of pot assium and magnesium, and to prolongation of the time of exposure to t he cardioplegic solutions. On the other hand, these lesions were signi ficantly reduced in samples exposed to a low-potassium cardioplegia co ntaining glucose and mannitol, and in samples exposed to a high-potass ium cardioplegia containing albumin, glucose, and mannitol. The most s ignificant alteration consisted in loss of endothelial cells accompani ed by wide exposure of subendothelial connective tissue. This lesion m ay induce thrombogenic mechanisms and consequently it may favour graft occlusion.