In vitro and in vivo testing of a novel, hyperelastic thin film nitinol flow diversion stent^†

A flexible, low profile, flow diversion stent could replace endovascular coiling for the treatment of intracranial aneurysms. Micropatterned-thin film nitinol (TFN) is a novel biomaterial with high potential for use in next-generation endovascular devices. Recent advancements in micropatterning have allowed for fabrication of a hyperelastic thin film nitinol (HE-TFN). In this study, the authors describe in vitro and in vivo testing of novel HE-TFN based flow diverting stents. Two types of HE-TFN with expanded pores having long axes of 300 and 500 μm were used to fabricate devices. In vitro examination of the early thrombotic response in whole blood showed a possible mechanism for the device's function, whereby HE-TFN serves as a scaffold for blood product deposition. In vivo testing in swine demonstrated rapid occlusion of model wide-neck aneurysms. Average time to occlusion for the 300-μm device was 10.4 ± 5.5 min. (N = 5) and 68 ± 30 min for the 500-μm device (N = 5). All aneurysms treated with bare metal control stents remained patent after 240 min (N = 3). SEM of acutely harvested devices supported in vitro results, demonstrating that HE-TFN serves as a scaffold for blood product deposition, potentially enhancing its flow-diverting effect. Histopathology of devices after 42 days in vivo demonstrated a healthy neointima and endothelialization of the aneurysm neck region. HE-TFN flow-diverting stents warrant further investigation as a novel treatment for intracranial aneurysms. © 2011 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 2012.