Localization of Tissue Plasminogen Activator in Relation to Morphologic Changes in Human Saphenous Veins Used as Coronary Artery Bypass Autografts

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Abstract
Employing the histochemical fibrin slide technique, we studied the localizatin of fibrinolytically active sites in reltin to morephologic changes in saphenous veins used as coronary artery bypass autografts. Of veins from 100 patients undergoing surgery for coronary heart disease, 63 samples reveraled well-demarcaetd intimal fibrinolyti activity. Distinct foci of lysis were persent in the media and advantitia of all vein samples corresponding to the distribution of the vasa vasorum. Graft specimens obtained by autopsy from 13 patients surviving from 30 minutes to 13 days reverled considerableintimal damage with loss of fibrinolyticd activity. Medial fibrinolytic activity disappearedearly concomitant with disorganization of the medial muscle fibers, folowed by necrosis, atropny and fibrous transformation ofteh muscular structures. Adventitial activity disappeareed later. One reoperation sample obtainedafter 8 weeks in situ showed moderate proliferative intimal fibrosis without an apparent neo-intima and without fibrinolytic activity, and one section showedevidence of valve cusp fibrosis, while most of the mediav had been replaced by fibrous tissue. Numerous foci of “mendial” advential fibrinolytic activity indicated presence of vascular structures in the vnous wall. The fibrin slide technique is a covenient tool for studying the process ofrevasuclarization.