Preparation of the saphenous vein for coronary artery bypass grafting: A new technique -"no touch" -that maintains the vein wall integral and provides high immediate patency Preparo da veia safena na cirurgia de revascularização miocárdica: uma nova técnica -"no touch"-que mantém a parede da veia íntegra e proporciona uma alta perviabilidade imediata Method: A prospective randomized study in 156 patients who underwent CABG was performed comparing three SV harvesting techniques. The techniques were conventional (c) (adventitial stripping of the vein, manual distention and storing in saline solution); Intermediate (I) (after adventitial stripping, the vein was left in situ, covered with a papaverinesoaked compress, and stored in heparinized blood); and "no touch" (SV dissected with its surrounding tissue was left in situ, covered with a saline-soaked compress and stored in heparinized blood). A morphological study of the endothelium was preformed using scanning electronic microscopy and an angiographic assessment of the vein graft patency was performed at 18 months mean follow-up time. Also an immunohistochemistry assessment was performed to identify the enzyme, nitric oxide synthase (NOS) in the vein wall.Results: The preservation of the endothelial cell integrity was greater with the "no touch" technique than with the other procedures. At angiographic follow up, the patency for NT was 95.4%, 88.9% for grafts in group C and 86.2% for grafts in group I. The immunohistochemistry assessment revealed NOS in all three layers of the vein wall that was prepared by the "no touch" technique. However, a great reduction of this enzyme in veins treated by the conventional technique was observed. Conclusion:The endothelial integrity and NOS activity were better preserved when using the "no touch" technique for vein graft harvesting. The vasorelaxation and thromboresistant activities of nitric oxide (NO) may be responsible for the reduced of vasospasms and improved patency rate. Furthermore, the mechanical properties provided by the Rev Bras Cir Cardiovasc 2003; 18(4): 303-311