Slides

Internal Mammary Artery Graft Stenosis and Revascularization
The internal mammary artery (IMA) is currently considered the vascular conduit of choice for patients who undergo elective surgical coronary artery bypass graft surgery with a bypass to the left anterior descending coronary artery (LAD). When compared to saphenous vein grafts, IMA grafts have shown superior long-term patency rates, lower frequency of reoperation and lower long-term myocardial infarction and mortality rates.
The higher long-term patency and low restenosis rate of the IMA grafts when compared to saphenous vein grafts can be attributed to an apparent resistance of this vessel to accelerated atherosclerosis. The production of endothelial vasodilators (i.e., nitric oxide and prostacyclin) by IMA grafts, platelet-to-vessel wall interaction, as well as different contractile and proliferative characteristics of their smooth muscle cells, may play an important role in prolifereative graft vessel disease, and therefore in graft patency rates. And smooth muscle cells from IMA grafts have also less pronounced growth activity in response to serum or platelet-derived growth factor-BB (PDGF-BB) than saphenous vein grafts, despite a normal PDGF receptor expression and function. When compared to saphenous vein graft, IMA grafts showed that cyclin-dependent kinase inhibitors (i.e., p27Kip1 and p21 Cip1), which cause cell cycle arrest in cultured cells in G1, are less downregulated. In this results, smooth muscle cell proliferation in IMA grafts decrease.
Contrary to saphenous vein graft stenosis, balloon angioplasty of the IMA graft have the lots of experiences and showed good clinical results. Gruberg et all reported that balloon angioplasty had a 8-30% of restenosis rates and stenting had a 33% rates (p=ns). Zavalloni et al also reported that there were no differences both between stents and balloon angioplasty and between drug eluting stents and bare metal stents.
REFERENCES
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6. Klein LW. Balloon angioplasty of internal mammary artery bypass grafts: bailing out the surgeons. Cathet Cardiovasc Diagn 1998;44:157–8.

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