Oliver, Alexander A

Purpose Large aneurysms have a higher rupture risk, yet no available in vivo animal model consistently produces large aneurysms for testing endovascular therapies. Recent research suggests that adding calcium chloride (CaCl 2 ) to elastase yields larger aneurysms in a surgical rabbit model. We evaluated whether this effect translates to an endovascular approach by comparing aneurysm sizes created using elastase alone versus a CaCl 2 –elastase combination. Methods Aneurysms were created in the right common carotid artery of New Zealand rabbits. One group received 1 mL porcine elastase; the other received elastase plus 0.055 g CaCl 2 (0.5 M). After four weeks, patency was confirmed via digital subtraction angiography. Two blinded co-authors measured the neck, width, and height of the aneurysms. Aneurysm volumes were estimated using AngioCalc.com. Statistical analyses were performed using either the Mann–Whitney U -test or t -test based on data distribution. Results Twenty-nine (29) New Zealand rabbits were included in the study: six in the CaCl 2 and elastase groups, 23 in the elastase-alone group. All induced aneurysms remained patent at follow-up. Mean neck size was significantly larger in the CaCl 2 + elastase group than in the elastase-alone group (4.4 ± 1.1 mm vs 3.5 ± 0.95 mm; respectively, p = 0.02). Differences in width (4.1 ± 0.92 mm vs 3.4 ± 0.36 mm; p = 0.06), height (9.0 ± 1.1 mm vs 9.1 ± 2.1 mm; p = 0.46), and volume (83.5 ± 38.35 mm ³ vs 53.0 ± 16.94 mm³; p = 0.11) were not significant between CaCl 2 + elastase and elastase-alone, respectively. Conclusions CaCl 2 modestly increased neck size but did not significantly enlarge overall aneurysm dimensions. Further studies are needed to assess its utility in endovascular aneurysm models.

Background and purpose New Zealand White Rabbits are a useful preclinical model for neurovascular research. Inducing right common carotid artery aneurysms in New Zealand White Rabbits gives researchers the ability to test neurovascular devices in vivo. This study takes advantage of archived angiograms to obtain vascular measurements of interest for future research in rabbit models. Methods Rabbit angiograms from endovascular studies conducted in-house between 2005 and 2024 were analyzed using ImageJ at points of interest along the thoracic and abdominal aorta. Using scale references, the diameters of various New Zealand White Rabbit (2.5–3.5 kg) arteries were measured for aneurysm models and controls. Anatomic vascular variations were categorized and recorded. Results Measurable artery diameters at 39 points of interest were recorded for 170 female New Zealand White Rabbits. Type 1 vascular anatomy was the most common rabbit aortic arch, characterizing 85% of identifiable rabbit anatomies in this study. Conclusion By making these measurements available, this study simplifies future neurovascular studies, allowing for vasculature to be selected by size depending on the application. Additionally, the study offers insight into the relationship between elastase-induced aneurysms and surrounding vasculature size and draws size comparisons between some key arteries of interest.

Background Although flow diverters (FDs) have benefited from several technical improvements, recently concerns have arisen regarding the braid stability after implantation. Thus, we investigated frequency, predictive factors, and clinical impact of the phenomenon of FD braid deformation (FDBD). Methods Consecutive intracranial aneurysms (IAs) treated with various FDs, between January 2018 and July 2023, were reviewed to identify FDBD (defined as the deformation of a FD without any external force applied to it). Patient, aneurysm, procedural, and FD characteristics were retrieved and analyzed using univariate and multivariable analyses. Morbidity is defined as a score of +1 in the modified Rankin Scale at 3 months. Results In total, 245 FD procedures (271 FDs implanted; 25 multiple IAs treated with 1 FD) in 228 patients; FDBD was observed in 36/245 cases (14.7%), mainly at follow-up angiography (32/36, 88.9%); fish-mouthing was the most frequent FDBD. Morbidity was related to fish-mouthing and braid collapse and was significantly higher in the FDBD group after retreatment (p=0.04). Drawn filled tubing with platinum (DFT) (adjusted odds ratio (aOR)=7.0, 95% CI 3.0 to 17.5; p<0.001) and FD diameter (aOR=2.2, 95% CI 1.3 to 4.1; p<0.01) were identified as independent predictors of FDBD. The metal alloy composing the FD (p=0.13) and coated surfaces were not significantly associated with FDBD (p=0.54 in multivariable analysis). Conclusions FDBD is a frequent phenomenon observed in about 15% of cases, and it was responsible for higher morbidity. Only FD characteristics (DFT and FD diameter) were independent determinants of FDBD. Future research should focus on the impact of novel braid configurations and materials on braid stability.

The New Zealand rabbit elastase-induced arterial aneurysm of the right common carotid artery remains a widely used model for assessing the effectiveness and safety of new neuroendovascular devices.1 This model offers a simple and reliable platform for pre-clinical in vivo investigations, crucial for comprehending the biological processes underlying aneurysm healing after endovascular treatment.2 Notably, the induced aneurysm exhibits morphological, hemodynamic, and histological characteristics similar to human intracranial aneurysms. The creation of the aneurysm is performed using open and endovascular techniques. Each step of the procedure requires a meticulous and controlled gesture to ensure reproducibility of the aneurysm and minimize animal misuse. In video 1 we present a step-by-step procedural guide for aneurysm creation and follow-up. We hope this resource will help in promoting this model and provide useful guidance for researchers in the field. Video 1 Surgical procedure of creating elastase-induced aneurysms in rabbits.

Platinum-containing stents are commonly used in humans with hypercholesterolemia, whereas preclinical stent evaluation has commonly been performed in healthy animal models, providing inadequate information about stent performance under hypercholesterolemic conditions. In this investigation, we used an ApoE−/− mouse model to test the impact of hypercholesterolemia on neointima formation on platinum-containing implants. We implanted 125 μm diameter platinum wires into the abdominal aortas of ApoE−/− and ApoE+/+ mice for 6 months, followed by histological and immunofluorescence examination of neointimal size and composition. It was found that ApoE−/− mice developed neointimas with four times larger area and ten times greater thickness than ApoE+/+ counterparts. Neointimas developed in the ApoE−/− mice also contained higher amounts of lipids quantified as having 370 times more coverage compared to ApoE+/+, a 3-fold increase in SMCs, and a 22-fold increase in macrophages. A confluent endothelium had regenerated in both mouse strains. The ApoE−/− mice experienced luminal reductions more closely resembling clinically relevant restenosis in humans. Overall, the response to platinum arterial implants was highly dependent upon the atherogenic environment.

The use of flow diverters is a rapidly growing endovascular approach for the treatment of intracranial aneurysms. All FDA-approved flow diverters are composed of nitinol or cobalt-chromium, which will remain in the patient for the duration of their life. Bioresorbable flow diverters have been proposed by several independent investigators as the next generation of flow diverting devices. These devices aim to serve their transient function of occluding and healing the aneurysm prior to being safely resorbed by the body, eliminating complications associated with the permanent presence of conventional flow diverters. Theoretical advantages of bioresorbable flow diverters include (1) reduction in device-induced thrombosis; (2) reduction in chronic inflammation and device-induced stenosis; (3) reduction in side branch occlusion; (4) restoration of physiological vasomotor function; (5) reduction in imaging artifacts; and (6) use in pediatric applications. Advances made in the similar bioresorbable coronary stenting field highlight some of these advantages and demonstrate the feasibility and safety of bioresorbable endovascular devices in the clinic. The current work aims to review the progress of bioresorbable flow diverters, identify opportunities for further investigation, and ultimately stimulate the advancement of this technology.