Objective To study the safety of the novel high nitrogen nickel-free austenitic stainless steel bare metal stents (BMS) in a recognized porcine coronary model and to select a better grid structure of it.
Methods Three types of stents were randomly implanted in different coronary arteries of the same pig: 316L stainless steel BMS (316L-BMS) (n=12), novel high nitrogen nickel-free stents Grid A (NF-A-BMS) (n=12) and novel high nitrogen nickel-free stents Grid B (NF-B-BMS) (n=12). In total, eighteen animals underwent successful random placement of 36 oversized stents in the coronary arteries. Coronary angiography was performed after 36 d of stents implantation. Nine animals were respectively sacrificed after 14 d and 36 d for histomorphologic analysis.
Results Quantitative coronary angiography (QCA) showed similar luminal loss (LL) in the three groups:(0.21±0.17) mm for 316L-BMS, (0.16±0.12) mm for NF-A-BMS, (0.24±0.15) mm for NF-B-BMS (P>0.05). Histomorphomeric analysis after 15 d and 36 d revealed that there was also no significant difference among the three groups in neointimal area (NA) with similar injury scores respectively. High magnification histomorphologic examination showed similar inflammation scores in the three groups, but NF-A-BMS group had poorer endothelialization scores compared with NF-B-BMS group, 2.00±0.63 vs. 2.83±0.41 (P=0.015) at 15 d, which also could be proved by the scanning electron microscope. However, the difference could not been observed at 36 d.
Conclusion The novel NF-BMS showed similar safety as 316L-BMS during the short-term study. NF-B-BMS had better endothelialization than NF-A-BMS and this may owe to the specific strut units.