Endothelium-dependent relaxation in human saphenous vein grafts. Effects of preparation and clinicopathologic correlations
Activity of endothelium-dependent relaxation factor (EDRF) was measured in 139 open ring preparations of fresh human saphenous vein from 85 patients undergoing coronary bypass grafting. The veins were constricted with phenylephrine and relaxed with the EDRF-dependent agents calcium ionophore A23187 or acetylcholine. EDRF activity produced a 36% +/- 4% relaxation of baseline contraction in response to calcium A23187. Vein graft preparation with room-temperature heparinized normal saline and pressurization to 400 mm Hg caused EDRF relaxation to fall to 10.6% +/- 2.0% versus 32.4% +/- 3.4% for control segments (p less than 0.05). Storage alone in room-temperature saline reduced EDRF response to 17.4% +/- 3.9% versus a control of 29.6% +/- 4.7% (p less than 0.05). Storage in heparinized room-temperature blood produced relaxation of 31.4% +/- 4.3% versus 34.1% +/- 5.7% (p less than 0.05). Storage in Plasma-Lyte solution (Travenol Laboratories, Inc., Deerfield, Ill), produced relaxation of 28.4% +/- 6.3% versus 30.1% +/- 5.3% (control) (p greater than 0.05). Veins stored at 2 degrees to 4 degrees C had severe depression of EDRF: 18.2% +/- 4.0% versus 34.0% +/- 5.4% for 37 degrees C storage (p less than 0.05). Pressurization to 400 mm Hg lessened EDRF relaxation: 20% +/- 3% versus 34% +/- 4% (control) (p less than 0.05), and use of nitroglycerin, papaverine, or verapamil produced no improvement. Twenty-eight vein grafts prepared with Plasma-Lyte solution were obtained from 12 patients who died 11.6 days (range up to 66 days) after operation. When compared with control veins prepared with saline and obtained at similar intervals, they had significantly more intact endothelium, less subintimal cellular infiltration, less fibrin deposition, fewer medial inflammatory changes, and less necrosis. Thus EDRF activity is significantly affected by vein graft preparation. Changes in technique to preserve EDRF produced better graft morphology early after operation.