Accelerated intimal hyperplasia in aortocoronary internal mammary vein grafts in minipigs

Six minipigs underwent aortocoronary bypass grafting using standard cardiopulmonary bypass and cardioplegic arrest. Mammary vein were grafted in a reversed manner from ascending aorta to left anterior descending coronary artery (LAD). The proximal LAD was ligated, rendering the anterior left ventricle vein graft-dependent. Minipigs were killed after 4 weeks, and vein grafts were harvested. Histological and immunohistological investigation were performed with respect to morphometric analysis, endothelial damage/dysfunction (v-Willebrand-factor (vWF)), smooth muscle cells (α-smooth actin) and proliferation rate (proliferation marker Ki 67).Mean intimal area of vein grafts was increased compared to ungrafted mammary veins. Intimal hyperplasia in vein grafts was characterized by massive accumulation of smooth muscle cells with a high proliferation rate and endothelial perturbation. Significant (p = 0.001) intimal hyperplasia of the grafted mammary vein compared to the ungrafted mammary vein was found. These changes were absent in ungrafted mammary veins.The present study demonstrates a pig model of aortocoronary vein graft intimal hyperplasia which is characterized by an accelerated progression within internal mammary veins. The model is suitable to investigate the pathophysiology of aortocoronary vein graft intimal hyperplasia as well as therapeutic approaches.The saphenous vein is still a conduit of choice for coronary artery bypass grafting. Following arterializations, vein grafts undergo immediate injury like ischemia and wall stress. The histological changes associated with vein graft failure are defined as intimal hyperplasia. They include acute thrombosis or early medial and intimal thickening that may be focally progressive. Further reason is late artheroma formation, which is the most important cause of failure beyond five years after implantation [1]. This vein graft failure is result of progressive thickening of the intima and media acting over the first mont