Bioresorbable magnesium flow diverter promotes early aneurysm occlusion in rabbits

BACKGROUND: Bioresorbable flow diverters (BRFDs) may overcome the limitations of permanent flow diverters (FDs). We developed a long period stacking ordered-type magnesium (Mg) alloy with superior strength, processability, and corrosion resistance using rapidly solidified powder metallurgy. Thin Mg wires were coated with poly L-lactic acid (PLLA) by electrospinning to extend bioresorption, and braided into 48 wire Mg-BRFDs. METHODS: We compared mechanical properties, angiographic outcomes, and biological responses of Mg-BRFDs with cobalt-chromium/platinum-tungsten FDs (CoCr-FDs) in a rabbit elastase induced aneurysm model and abdominal aorta. Assessments included angiography, optical coherence tomography, scanning electron microscopy, and histopathology at 0.5, 1, and 3 months. RESULTS: Mg-BRFDs had a mean strut diameter of 56 µm (including a 10 µm PLLA coating), porosity of 53.9%, and pore density of 23 pores/mm². Complete occlusion rates in CoCr-FDs were 20% (1/5), 0% (0/7), and 57% (4/7) at 0.5, 1, and 3 months, respectively; corresponding rates with Mg-BRFDs were 50% (3/6), 75% (6/8), and 100% (8/8). Among cases with incomplete occlusion, neointimal coverage rate of the aneurysm neck was significantly greater with Mg-BRFDs (median 70.2% vs 26.1%, P=0.006). No occlusion of side branches covered by FDs occurred in either group. Neointimal ionized calcium binding adapter molecule 1 (Iba-1) positive cell counts were higher with Mg-BRFDs but declined over time (P=0.0003). CONCLUSIONS: Mg-BRFDs promoted early neointimal formation during bioresorption, leading to faster and more complete aneurysm occlusion than CoCr-FDs. These findings demonstrate the feasibility of Mg-BRFDs as a promising next generation therapeutic strategy.