Pathology of stent implantation in internal mammary artery

The internal mammary artery(IMA) is the most durable conduit for bypassing the left anterior descending (LAD) coronary artery in patients undergoing coronary artery bypass graft surgery (CABG). However, little is known about how the IMA reacts histologically to stentimplantation. From CVPath stentregistry (1048 lesions, 614 cases), we obtained 4 stentlesions (2 bare metal stents, 2 drug-eluting stents) involving IMA grafts. The mean age of our patients was 63 years and the duration of stentimplantation in the IMA ranged from 5 days to 5 years. Stentedarteries were dissected from hearts and embedded in plastic, segmented at 3 mm intervals, sectioned at 4–6 microns and stained with H&E and Movat pentachrome stains. Histological observations were performed. Majority of stents(3 of 4) were implanted in anastomosis between IMA and LAD while 1 stentwas implanted in IMA body. One stentwith duration of 5 days showed stentthrombosis while others were all patent with fully coverage by varying degrees of neointima. Foamy macrophage, lipid pool and calcification in neointimawere observed in 1 stentwith duration of 5 years but it was limited only to the distal LAD part within the stentedsegment. Overall, in this small pathologic series, the majorities of stentswere implanted in IMA-to-LAD anastomosis site and demonstrated acceptable pathologic responses.