ENDOTHELIAL DAMAGE OF THE VENOUS GRAFT IN CABG - INFLUENCE OF SOLUTIONS USED FOR STORAGE AND RINSING ON ENDOTHELIAL FUNCTION

A significant proportion of early graft occlusions after aortocoronary revascularization using autologous saphenous vein grafts (SVG) are du e to mechanical and/or metabolic or biochemical endothelial lesions. T he morphological examination of the endothelium, usually carried out u sing light microscopy or by various types of scanning electron microsc opy (SEM), does not give any indication of the functioning of the endo thelium (E). Functionally intact E is capable of producing endothelium -derived relaxing factor (EDRF); a practicable in vitro test is the re laxation of pre-contracted vein segments (VS) in response to acetylcho line (ACh) application. To study the effect of the solution used to ri nse and store the SVG between removal and implantation on the function al characteristics of the E, we performed in vitro tests on macroscopi cally intact VS removed from the saphenous vein of 30 male patients wh o underwent elective CABG surgery. Isolated VS rings were incubated fo r 60 min in heparinized whole blood (HWB), Bretschneider's cardioplegi c solution (HTK), human albumin solution (HAS), or Ringer's solution ( RS) and compared with the results obtained immediately after the remov al of untreated control samples (C) taken from the same patients. Afte r equilibration in carbogen aerated Krebs-Henseleit solution and preco ntraction by 3 x 10(-7) M noradrenaline (NE), relaxation induced by 10 (-6) M ACh was measured. Only the samples stored in HWB (13.4 +/- 0.4 mN) showed similar maximal contractions with NE to those in the contro l group (14.4 +/- 0.5 mN), i.e. all those segments which showed both c ontractions with NE and relaxation with ACh. Moreover, after HWB 29/30 veins contracted in response to NE, while after HTK, HAS and RS only 25/30, 13/30 and 12/30, respectively, exhibited a contractile response . Relaxation due to ACh, which is only possible with intact E, was fou nd in 72.4% of the samples after HWB, in 44% of the HTK samples, but i n none of the HAS and only in 1 RS sample. In addition, in 76.9% of th e HAS and 83.3% of the RS samples, paradoxical contractions in respons e to ACh were observed. These physiological results were correlated wi th blind evaluations of SEM examinations in the identical VS. Using es tablished scoring systems, it was not possible to predict the signific ant differences in endothelial function on the basis of the SEM examin ations of the same samples. These data indicate that, of all the solut ions used in clinical practice for rinsing and storing bypass veins, H WB is significantly better for maintaining functionally intact E than HTK, while other crystalloid and colloidal solutions lead to severe im pairment of endothelial function.