Efeito da pressão de distensão e da solução de preservação sobre a ultraestrutura do endotélio da veia safena magna

Abstract

The saphenous vein (SV) remains relevant in the context of myocardial revascularization (CABG) surgery. Studies that indicate limited long-term patency of this conduit imposes constant search for better surgical results. The objective of this study was to evaluate, using scanning electron microscopy (SEM), the effects of using different graft preservation solutions, and different intraluminal distention pressures on ultrastructural anatomy, and in endothelial integrity of SV segments in CABG. 42 segments of SV obtained from twelve patients undergoing CABG were divided into seven groups. Group 1 (control) consisted of SV segments that, after surgical excision, were immediately preserved in a fixation solution. Segments of groups 2 and 3 were distended and preserved with autologous heparinized arterial blood (AHB) (group 2) or normal saline (NS) solution (group 3) at a pressure of 30 mmHg and then kept under this pressure with fixing solution. Segments in groups 4 and 5 were distended at a constant pressure of 100 mmHg with AHB (group 4) or NS (group 5). SVs of groups 6 and 7 were distended at a constant pressure of 300 mmHg with AHB (group 6) or NS (group 7). Venous grafts were analyzed by SEM, and a score was used to measure the degree of endothelial damage. It was observed that SV segments preserved with NS had significantly greater endothelial damage both compared to the control group and to the groups submitted to distention pressures of 30 mmHg and 100 mmHg. Venous segments stretched with a pressure of 300 mmHg showed a soaring degree of damage, with considerable loss and separation of endothelial cells, extensive exposure of the basement membrane, and numerous fractures of the intimate layer, with no differences regarding the preservation solution used. SV distended with a pressure of 30 mmHg showed scarce endothelial damage, compared to segments dilated with pressures higher than that. In summary, it is concluded that the preparation of SV using saline solution and with intraluminal distension pressures above 30 mmHg are factors related to greater damage to the endothelium of these grafts, which could reduce their patency after CABG. Additionally, adoption of blood as a preservation solution, in association to lower distension pressures were factors related to endothelial protection.