Long-term histologic and immunohistochemic findings in human venous aorto-coronary bypass grafts
Résumé
Aim of the study was to analyse the long-term histology and immunohistochemistry of the plaque composition and cellular infiltration of saphenous vein grafts (SVG) containing metallic stents. Percutaneous interventions in SVG bear a worse long-term clinical outcome compared to stenting of coronary arteries. Whether the pathologic features of old, degenerated SVG condition the efficacy of drug-eluting stents also is unknown. Histology and immunohistochemistry of 7 SVG to the coronary circulation containing 12 metallic stents implanted 5 to 61 months before retrieval were analised in patients undergoing a second aorto-coronary bypass surgery at a mean time of 11±6 years. Pathology of old SVG showed important thrombotic and necrotic composition of the plaque with plaque protrusion through the stent wires and a fragile media layer that can be easily damaged by stent placement with subsequent neointimal proliferation; indeed, stents showing medial fracture showed significantly greater mean neointimal thickness (1.37±0.68mm 2} versus 0.81±0.47mm 2}, p<0.02). Neointimal inflammatory cell density correlated with increased neointimal thickness in patent vessels (r 2}=0.43, p<0.001). Immunostaining showed the total absence of estrogen receptors, a poor cellular proliferative state according to the presence of Ki-67 marker, persistent inflammation close to the stent wires marked by KP-1, and angiotensin-converting enzyme (ACE) immunostaining in most inflammatory cells in contact with the metal. These pathologic findings may contribute to the more severe progression of disease and worse clinical outcome observed after conventional stented angioplasty of SVG and might also interfere with the efficacy of drug-eluting stents in this specific atherosclerotic milieu.
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