Endothelial integrity and nitric oxide synthase sources are better maintained in saphenous vein harvested by a ‘no-touch’ technique

Abstract

Abstract Background The saphenous vein (SV) is a commonly used conduit in bypass procedures. Early graft occlusion rates are greater than 20 per cent in both infrainguinal vein grafts and coronary artery bypass grafts (CABGs). Contributing factors include adventitial and endothelial damage, which may reduce nitric oxide availability in grafts. Nitric oxide has important vasorelaxant and thromboresistant properties beneficial to graft patency. Conventionally, during SV harvest, the perivascular tissue is stripped and the graft distended. A ‘no-touch’ technique has been described in which the SV is harvested together with a cushion of surrounding tissue without vein distension. This study compared endothelial integrity and the potential role of nitric oxide synthase (NOS) in segments of SV harvested by the two techniques. Methods SV was harvested from ten patients undergoing CABG. Distal and proximal ends of the SV were harvested using the no-touch technique, while the middle portion was stripped of the adventitia and distended. Sections of SV were cut and endothelial integrity was assessed with CD31 immunohistochemistry and quantified by morphometric analysis. Putative NOS was identified by reduced nicotinamide adenine dinucleotide phosphate (NADPH)–diaphorase histochemistry and autoradiographic localization of [3H]l-NG-nitroarginine binding. Results More dense CD31 staining was seen on the luminal aspect and vasa vasorum of vessels harvested by the no-touch technique. Morphometric analysis revealed a significant reduction in luminal CD31 staining in conventional compared with no-touch grafts (P < 0·05, Student's t test). NADPH staining was almost continuous on the luminal aspect, and was also present in the adventitia of no-touch vessels, compared with poor staining of conventionally harvested vessels. The pattern of NADPH staining corresponded to endothelial cells lining the vessel lumen as well as vasa vasorum and paravascular nerves in the adventitia. Autoradiographic analysis of specific [3H]nitroarginine binding also showed greater binding in the no-touch vessels. Conclusion Endothelial integrity is better maintained by the no-touch technique. NOS sources on the endothelium and adventitia are preserved, suggesting that nitric oxide availability is retained by these grafts. This technique may therefore lead to improved early patency rates of SV grafts in bypass surgery.