Comparative pathological findings between coronary bare-metal stent implantation and balloon angioplasty over 16 years

A 68-year old man underwent bare metal stent (BMS; Palmaz-Shatz stent) implantation in the distal right coronary artery (RCA; #4PL) and balloon angioplasity (BA) in the proximal left circumflex coronary artery (LCX; #11) for stable angina. After 5 years after initial stent implantation, de novo lesion located in mid RCA was treated by BMS (NIR stent) implantation additionally. After 16 years from first BMS implantation, the patient died from heart failure due to cardiac amyloidosis, and pathologic examination was performed for the specimen of stented RCA segment and LCX BA segment. An autopsy demonstrated that the lesions of stented site at RCA and BA site LCX were histopathologically different. In the stented segment, severe luminal stenosis is observed due to marked proliferation of the neointima in all stented sites. In addition, neovascularization and spotty calcification with mild lymphocyte infiltration were observed especially around the struts. In contrast, at the BA site of the proximal LCX lesion, in the neointima, the smooth muscle cells were rather atrophic and abundant collagen fibers were evident in the intercellular spaces, which showed very stable findings. Compared with these BMS implanted portions, the site of BA was associated with a trend for smaller late lumen loss. These findings suggested that in the stented site, chronic inflammatory reaction to the stent struts could evoke continuous proliferation of neointima resulting in severe late lumen loss.