Construction of 3 animal experimental models in the development of honeycomb microporous covered stents for the treatment of large wide-necked cerebral aneurysms

Abstract

The treatment of large or wide-necked cerebral aneurysms is extremely difficult, and carries a high risk of rupture, even when surgical or endovascular methods are available. We are developing novel honeycomb microporous covered stents for treating such aneurysms. In this study, 3 experimental animal models were designed and evaluated quantitatively before preclinical study. The stents were prepared using specially designed balloon-expandable stents (diameter 3.5-5.0 mm, length 16-28 mm) by dip-coating to completely cover their struts with polyurethane film (thickness 20 µm) and microprocessing to form the honeycomb pattern after expansion. (1) In an internal carotid artery canine model (n = 4), all stents mounted on the delivery catheter passed smoothly through the tortuous vessel with minimal arterial damage. (2) In an the large, wide-necked, outer-sidewall aneurysm canine model, almost all parts of the aneurysms had embolized immediately after stenting (n = 4), and histological examination at 2 months revealed neointimal formation with complete endothelialization at all stented segments and entirely organized aneurysms. (3) In a perforating artery rabbit model, all lumbar arteries remained patent (n = 3), with minimal change in the vascular flow pattern for over 1 year, even after placement of a second, overlapping stent (n = 3). At 2 months after stenting, the luminal surface was covered with complete thin neointimal formation. Excellent embolization performance of the honeycomb microporous covered stents without disturbing branching flow was confirmed at the aneurysms in this proof-of-concept study.

Hydrodynamical evaluation of microporous covered stent for the treatment of intracranial aneurysms: Comparison of flow reduction property with flow diverter stent by using particle imaging velocimetry and in vitro flow simulator

“…From this result, it is clear that MCS's flow reduction property is superior to Pipeline Flex stent, and reliable IA embolization treatment can be provided by using MCS. Strong flow reduction can lead to occlusion of the side-branch where the stent is placed, but good patency was observed on the part of the MCS in previous study [9].…”

“…The influence of blood flow shear rate on thrombosis promotion has been reported in previous papers [10,11]; therefore, we only studied the relationship between the pore design of the shielding stent and the shear rate of IA flow [17]. Both reliable IA embolization and patency of the perforating arteries were achieved by placing MCS (NCVC-CS1) in a previous study [9]. The main objectives of this study were evaluation of the flow reduction property of MCS's pore design and compare to that of FD, an existing IA embolization device, by focusing on the shear rate.…”

“…The second was an FD model with an imitated mesh pattern of Pipeline Flex [12], a typical flow diverter stent, for IA treatment. The third was an MCS model, with the imitated mesh pattern of our developing stent (NCVC-CS1) [9] for IA treatment. The diameter and length of NCVC-CS1 were 3.5-5.0 mm and 16-28 mm, respectively.…”

“…Microporous covered stents (MCSs) [7][8][9] have also been developed for the treatment of giant and/or wide-neck IAs. An MCS is completely embedded within a thin microporous film of segmented polyurethane, which provides a flat luminal surface.…”

“…By adjusting the pore size and porosity of the microporous film, flow reduction is controlled to induce thrombosis in IA and to not excessively inhibit blood flow in side-branch vessels [8]. To investigate the MCS's easy-navigation, IA embolization, and side-branch patency preservation properties, we previously performed in vivo studies [9].…”