P-011 A modification of the rabbit elastase model to produce more relevant aneurysm sizes

Introduction/purpose The rabbit elastase model has become a standard in vivo representation of human intracranial aneurysms, mimicking their histology and offering a means for laboratory testing of current and novel endovascular devices. Variations of the aneurysm creation procedure in rabbits exist, such as endovascular versus surgical exposure of the right common carotid artery (RCCA), where the aneurysm is induced. One particular variation, the modified elastase technique, results in aneurysms that are generally smaller than treated human aneurysms, making the model less relevant. The purpose of this study was to determine whether larger sizes could be created by combining calcium chloride (CaCl2) with elastase in the solution used to induce aneurysms with this technique. Methods/materials Animals were assigned to one of two groups, including elastase only (control, n=7) or a combination of CaCl2 and elastase (experimental, n=9). After administration of anesthetic, the RCCA was exposed, a temporary clip was placed at the brachiocephalic bifurcation, and a silk suture was used to ligate the vessel distally. An angiocatheter was placed in the occluded portion of the vessel and, depending on group assignment, either elastase only or CaCl2/elastase was injected into the occluded segment. After 20 min of incubation, the catheter was withdrawn and a silk suture was tied just proximal to the catheter entry site (3 cm distal to the bifurcation) to permanently occlude blood flow. The clip was then removed, and blood was re-perfused into the stump of the RCCA. After 4 weeks, angiographic results were obtained from each rabbit. Statistical analysis was performed using Student’s t-test. Results Mean angiographic aneurysm heights and widths were 5.16 mm±0.96 mm (SEM) and 2.48 mm±0.50 mm, respectively, in the control group and 7.82 mm±0.58 mm and 4.19 mm±0.25 mm, in the experimental group (p-value=0.03, 0.005). Calculated mean volumes were 24.98 mm3±10.93 mm3 and 75.93 mm3±12.22 mm3 in the control and experimental groups, respectively (p-value=0.009). Conclusion In the modified elastase technique of aneurysm creation in a rabbit model, the combination of CaCl2 and elastase results in increased aneurysm size and volume, versus elastase alone. When comparing our technique to the most commonly employed variations of the rabbit model in the literature, our modification yields aneurysms that are larger and within the size range of treated human aneurysms. Disclosures B. Belanger: None. M. Avery: None. A. Mitha: None.