Abstract 95: A Conformable and Compliant Nanocomposite Polymer Stent-Graft for Endovascular Repair of Aortic Arch

Abstract

Objectives: To develop new aortic stent-graft from polyhedral oligomeric silsesquioxane (POSS) and poly (carbonate-urea) urethane (PCU) nanocomposite polymer (NP) to achieve better conformability to arch anatomy and reduce aorta-prosthesis compliance mismatch. Methods: A constructed model of curved thoracic aorta from MRI was developed and anatomically accurate sutureless stent-graft was moulded using surface-modified Nitinol stents with composition of 55.8 wt.% Ni, diameter 0.62 mm and Af temperature less than 18 oC bonded to NP. An in vitro pulsatile flow phantom perfused NP stent-graft at physiological pulse pressure and flow. Diametrical compliance and stiffness index were calculated and comparison was made with ePTFE based in Gore TagTM thoracic stent-graft. Results: The NP stent-graft had uniform thickness of 150.7±6.6 μg and in its fully expanded shape, with diameter of 30 mm, matched curvature of aortic arch. Over temperature 37±1°C, mean pressure range 30-100 mm Hg, and pulse pressure 49±6 mm Hg, flow rate for NP stent-graft was 132±24 ml/min and ePTFE stent-graft was 140±25 ml/min (P=NS). Overall compliance of NP stent-graft was 3.3 ± 0.61%/mm Hg x 10-2 which was significantly better compared with ePTFE stent-graft (2.3±0.95 %/mm Hg x 10-2; P=0.0003). The ePTFE stent-graft was significantly stiffer with stiffness index β 92.7±46.1 compared to NP stent-graft (β 39.1±5.91; P<0.0001). The ePTFE stent-graft failed to exhibit anisotropic behaviour (i.e. visco-elasticity similar to natural vascular tissue) which was demonstrated by NP stent-graft. Conclusion: An innovative, curved, self-expanding and sutureless stent-graft is proposed for endovascular repair of thoracic aorta and aortic arch. The study confirmed the superior compliance, reduced elastic stiffness and visco-elasticity of POSS-PCU NP, which can help in improving device longevity by offering superior physiological and haemodynamic environment in vivo.