Abstract Body: Background: Bioresorbable flow diverter (FD) has the potential to overcome some of the disadvantages of permanent FDs. In the field of coronary arteries, magnesium (Mg) resorbable stents have been developed and their efficacy has already been reported in clinical practice. On the other hand, due to the poor machinability of Mg, the development of Mg bioresorbable FD (Mg-BRFD) with the specifications of porosity, pore density and strut diameters comparable to existing FDs has not yet been successful.
Methods: We developed 48 braided Mg-BRFD and compared them with FDs composed of cobalt-chromium and platinum-tungsten (CoCr-FD). Mg-BRFD (n=22) and CoCr-FD (n=19) were implanted in the rabbit elastase aneurysm models, and Mg-BRFD (n=12) and CoCr-FD (n=9) in the rabbit abdominal aorta. Aneurysmal occlusion rate, branch vessels patency, neointima and inflammation were assessed at 0.5, 1, and 3 months after implantation, respectively.
Results: The mean strut diameter of Mg-BRFD was 56 μm (of which 10 μm was poly-L-lactic acid coated), porosity was 53.9%, and pore density was 23 pores/mm². The CoCr-FD group had 20% (1/5), 0% (0/7) and 57% (4/7) of aneurysms completely occluded at 0.5 months, 1 month and 3 months, whereas the Mg-BRFD group had 50% (3/6), 75% (6/8) and 100% (8/8). Neointimal coverage rate of the aneurysm neck in cases of incomplete occlusion was significantly higher in the Mg-BRFD group (n=5) than CoCr-FD group (n=14) (median 75.8% vs 25.7%; p=0.006). On the other hand, occlusion of side branch vessels covered by FD was not observed in either group. Immunostaining of the neointima showed significantly more Iba-1-positive cells representing inflammation in the Mg-BRFD group in each period, but a decreasing trend over time (p=0.0003).
Conclusions: With its characteristics of early neointimal formation in addition to bioresorption, Mg-BRFD could achieve earlier and higher occlusion rates in rabbit aneurysm models compared to CoCr-FD.