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

Experimental Broad-Based Curved Sidewall Aneurysms in Rabbits Mimicking Human Carotid Siphon Aneurysms: Proof of Feasibility and Comparability Using Computational Fluid Dynamics

BACKGROUND/OBJECTIVE

Broad-based sidewall aneurysms of the carotid artery are primarily treated endovascularly. However, recurrence or rupture after treatment still poses a significant risk. Hence, reliable animal models mimicking this aneurysm type are essential for to evaluate the performance of new advanced endovascular devices.

METHODS

Experimental aneurysms were created in 12 New Zealand white rabbits (2.5-3.5 kg). The human carotid siphon was mimicked with an end-to-end anastomosis of both common carotid arteries. A venous pouch was sutured on the convexity to mimic a broad-based side wall aneurysm. Patency and configuration were investigated 4 weeks postoperatively by 3-T magnetic resonance angiography. To compare flow conditions of broad-based sidewall aneurysms in rabbits and humans, exemplary computational fluid dynamics simulations were performed using species-specific blood viscosity values.

RESULTS

We were able to achieve 0% peri- or postoperative mortality. Patency was confirmed by 3-T magnetic resonance angiography in 11 of 12 aneurysms (91.7%). Aneurysm lengths ranged from 6.4 to 9.8 mm and aneurysm necks from 7.3 to 9.8 mm. Computational fluid dynamics showed simple flow profiles with one vortex in rabbit as well as in human aneurysms. Wall shear stress rates were comparable using species-specific blood viscosity values (rabbit mean 1.65 Pa vs. human mean 1.7 Pa).

CONCLUSIONS

The broad-based curved sidewall aneurysm model mimicking the carotid siphon showed high aneurysm patency rates with low morbidity. High comparability with human flow patterns and human intranaeurysmal biomechanical forces was shown using simulations.

Preclinical extracranial aneurysm models for the study and treatment of brain aneurysms: A systematic review

Animal models make an important contribution to our basic understanding of the pathobiology of human brain aneurysms, are indispensable in testing novel treatment approaches, and are essential for training interventional neuroradiologists and neurosurgeons. Researchers are confronted with a broad diversity of models and techniques in various species. This systematic review aims to summarize and categorize extracranial aneurysm models and their characteristics, discuss advantages and disadvantages, and suggest the best use of each model. We searched the electronical Medline/PubMed database between 1950 and 2020 to identify main models and their refinements and technical modifications for creation of extracranial aneurysms. Each study included was assessed for aneurysm-specific characteristics, technical details of aneurysm creation, and histological findings. Among more than 4000 titles and abstracts screened, 473 studies underwent full-text analysis. From those, 68 different techniques/models in five different species were identified, analyzed in detail, and then grouped into one of the five main groups of experimental models as sidewall, terminal, stump, bifurcation, or complex aneurysm models. This systematic review provides a compact guide for investigators in selecting the most appropriate model from a range of techniques to best suit their experimental goals, practical considerations, and laboratory environment.

Neurovascular devices for the treatment of intracranial aneurysms: emerging and future technologies

Introduction: Despite numerous advances in the endovascular treatment of intracranial aneurysms (IAs), treatment in cases of wide-neck, complex configurations or branching locations remains challenging. Apart from the paradigm shift introduced by flow diverters, several other devices have seen the light or are under development in order to address these challenges.Areas covered: We performed a review of the novel implantable endovascular devices which have been introduced for the treatment of IAs, from 1 January 2014 to 1 September 2019, excluding classic flow diverter and intracranial stent designs.Expert opinion: Alternative designs have been proposed for the treatment of IAs at branching positions, which do not jail the side branches, with or without flow diversion effect, most of which with good initial outcomes. Endosaccular devices have also been proposed, some of which with lower initial total occlusion rates. Alternative materials such as biopolymers have also been proposed and are under bench research. Despite the challenges in the exploitation of some of the new devices, most of them seem to provide solutions to some current technical shortcomings. The exploitation of the biological phenomena and the physical properties of the devices will allow us to expand the therapeutic armamentarium for more complex IA cases.

Evaluating the safety and technical effectiveness of a newly developed intravascular 'flow isolator' stent for the treatment of intracranial aneurysms: study protocol for a first-in-human single-arm multiple-site clinical trial in Japan

INTRODUCTION

Wide-neck or large intracranial aneurysms are difficult to cure by conventional surgical or endovascular procedures. A flow diverter (FD) is an implantable, stent-like, fine-mesh medical device for the treatment of intracranial aneurysms. Although endovascular treatment with FDs is becoming a routine first-line option, a systematic review noted the heterogeneity and publication biases of the clinical studies for FDs. We have developed a new honeycomb microporous covered stent (NCVC-CS1) as a 'flow isolator' for the endovascular treatment of intracranial aneurysms.

METHODS AND ANALYSIS

We planned the NCVC-CS1_UAN as a first-in-human study to evaluate the safety and technical effectiveness of the NCVC-CS1, a newly developed honeycomb microporous covered stent, for the treatment of intracranial aneurysms that are difficult to cure by conventional surgical or endovascular procedures. The study is a multicentre, open-label, uncontrolled, exploratory, medical device, investigator-initiated clinical study. The primary safety endpoint of this study is any stroke or death related to the procedure within 180 days, while for efficacy, the endpoint is complete obliteration of the target aneurysm and patency of the target vessel (less than 50% stenosis) confirmed by angiography at 180 days after the procedure.

ETHICS AND DISSEMINATION

Full ethics approval of institutional review boards was obtained at all participating sites. A clinical trial notification as a new medical device was accepted by the Japanese regulatory agency before it started. The study should be followed by a pivotal study to obtain satisfactory data for an application for marketing approval. The main results of this study will be submitted for publication in a peer-reviewed journal. The planned subject number for this study is 12.

TRIAL REGISTRATION NUMBER

NCT02907229.

Large animals in neurointerventional research: A systematic review on models, techniques and their application in endovascular procedures for stroke, aneurysms and vascular malformations

Neuroendovascular procedures have led to breakthroughs in the treatment of ischemic stroke, intracranial aneurysms, and intracranial arteriovenous malformations. Due to these substantial successes, there is continuous development of novel and refined therapeutic approaches. Large animal models feature various conceptual advantages in translational research, which makes them appealing for the development of novel endovascular treatments. However, the availability and role of large animal models have not been systematically described so far. Based on comprehensive research in two databases, this systematic review describes current large animal models in neuroendovascular research including their primary use. It may therefore serve as a compact compendium for researchers entering the field or looking for opportunities to refine study concepts. It also describes particular applications for ischemic stroke and aneurysm therapy, as well as for the treatment of arteriovenous malformations. It focuses on most promising study designs and readout parameters, as well as on important pitfalls in endovascular translational research including ways to circumvent them.

Development of New Endovascular Devices for Aneurysm Treatment

Since the first use of the Guglielmi detachable coil system for cerebral aneurysm embolization in 1990, various endovascular methods have been developed to treat large numbers of aneurysms. The main strategic and technical modifications introduced to date include balloon-assisted coil embolization, stent-assisted coil embolization, flow diverters, and flow disrupters. The development and introduction of such devices have been so persistent and rapid that new devices are being approved worldwide even before the earlier ones become available in some countries. However, even if some patient populations may possibly benefit from earlier introduction of new devices, the approval authorities should balance the available evidence of the safety and effectiveness of novel devices. This review aims to provide an overview of the recent innovations in endovascular treatment of cerebral aneurysms and a brief review of market access policies and regulations for importing high-risk medical devices, such as those used for endovascular aneurysm management, which correspond to class III devices, as defined by the U.S. Food and Drug Administration. We focus on the current situation in Korea and compare it with that in other Asian countries, such as China and Japan.