Acute inflammation and endothelial injury in vein grafts

An experimental study of autogenous vein graft morphology 6 hours after arterial implantation was performed in dogs. The animals were divided into five groups. The first control group had veins harvested and stored but not implanted. The endothelium showed excellent preservation by routine histology and scanning electron microscopy. The second control group had grafts implanted and flow decreased to 30 to 50 ml/minute. There was a massive acute inflammatory response with subendothelial and transmural accumulation of neutrophils causing widespread endothelial sloughing. A third group had grafts implanted, but flow was not reduced (mean, 170 ml/minute). Although an inflammatory response was also present, it was much less severe than in the low flow grafts and the endothelium remained grossly intact. Two other groups had low flow grafts implanted, but were treated with either lidocaine or steroids. Lidocaine had no effect on the inflammatory response or endothelial injury. High doses of alpha-methylprednisolone succinate almost completely prevented both endothelial loss and inflammatory infiltration. This study supports the premise that an acute inflammatory response can initiate endothelial injury after autogenous grafting, an effect that is much more prominent in low flow than high flow grafts. It also demonstrated that steroids can almost totally suppress the injury during the initial 6 hours after implantation.