Background
The high radial force and durability of cobalt-chromium alloy enable the construction of low-profile stents with thin struts, which improves their elasticity and may play a key role in reducing the incidence of neointimal hyperplasia as well as allow faster endothelialization. The aim of this study was to compare cobalt-chromium (CoCr) and stainless steel (SS) coronary stents in a pig model of neointimal hyperplasia.
Material and Method
Eighteen stents were implanted into the coronary arteries of nine pigs. Control coronarography was performed 28 days after stent implantation. The animals were then sacrificed, their hearts explanted, and the coronary arteries isolated for further histopathological analysis.
Results
Quantitative coronary angiography and histomorphometric analysis revealed no statistically significant difference between the two groups of stents. However, there was a trend toward greater late lumen loss (p=0.09) and neointimal area in the CoCr stents (p=0.08). The qualitative histopathology of the CoCr stents revealed findings typical of bare metal stents reviewed in the literature and approved for use in clinical practice. No signs of stent thrombosis, necrosis, or fibrin deposits were observed nor signs of excessive inflammatory reaction. Endothelialization was complete within 28 days.
Conclusions
Despite thinner struts, CoCr stents have no advantage over stainless steel stents in terms of neointimal hyperplasia inhibition. However, their positive safety results together with their high radial strength, low profile, and excellent elasticity can ensure their usage, especially in lesions of complex morphology.

Keywords: Stainless Steel, Hyperplasia - prevention & control, Coronary Restenosis - therapy, Coronary Angiography, Chromium Alloys, Stents, Sus scrofa