Complex bilobular, bisaccular, and broad-neck microsurgical aneurysm formation in the rabbit bifurcation model for the study of upcoming endovascular techniques

Abstract

Background and purpose: Despite rapid advances in the development of materials and techniques for endovascular intracranial aneurysm treatment, occlusion of large broad-neck aneurysms remains a challenge. Animal models featuring complex aneurysm architecture are needed to test endovascular innovations and train interventionalists.

Materials and methods: Eleven adult female New Zealand rabbits were assigned to 3 experimental groups. Complex bilobular, bisaccular, and broad-neck venous pouch aneurysms were surgically formed at an artificially created bifurcation of both CCAs. Three and 5 weeks postoperatively, the rabbits underwent 2D-DSA and CE-3D-MRA, respectively.

Results: Mortality was 0%. We observed no neurologic, respiratory, or gastrointestinal complications. The aneurysm patency rate was 91% (1 aneurysm thrombosis). There was 1 postoperative aneurysm hemorrhage (9% morbidity). The mean aneurysm volumes were 176.9 ± 63.6 mm(3), 298.6 ± 75.2 mm(3), and 183.4 ± 72.4 mm(3) in bilobular, bisaccular, and broad-neck aneurysms, respectively. The mean operation time was 245 minutes (range, 175-290 minutes). An average of 27 ± 4 interrupted sutures (range, 21-32) were needed to create the aneurysms.

Conclusions: This study demonstrates the feasibility of creating complex venous pouch bifurcation aneurysms in the rabbit with low morbidity, mortality, and high short-term aneurysm patency. The necks, domes, and volumes of the bilobular, bisaccular, and broad-neck aneurysms created are larger than those previously described. These new complex aneurysm formations are a promising tool for in vivo animal testing of new endovascular devices.

Fig 1.

Schematic sketches of surgical steps, (A–C), intraoperative photographs under the operating microscope (A1–C1), and 2D-DSA (A2–C2) as well as CE-3D-MRA (A3–C3) screen shots of bilobular, bisaccular, and broad-neck aneurysms. A, Bilobular aneurysm. The jugular vein bifurcation stump is anastomosed to the CCA bifurcation, as described in the text and presented in Fig 3. B, Bisaccular aneurysm. Two venous pouches of the left or right external jugular vein are sutured together (white arrow) and anastomosed to the CCA bifurcation. C, Broad-based aneurysm. A 1-cm segment of the left external jugular vein is incised in a longitudinal manner, folded along its transverse axis (1), sutured together proximally (4–5 sutures) and distally (2–3 sutures) (2), and anastomosed to the CCA bifurcation (3).

Fig 2.

Arterial (red, A) and venous (blue, B) neck vascular anatomy of the rabbit. A, The LCCA is exposed and isolated for a segment of at least 5 cm. The RCCA is dissected distally to its proximal origin at the brachiocephalic trunk (black circle) to achieve a tensionless end-to-side anastomosis of the RCCA to the LCCA (black arrow). B, A 10- to 15-mm segment of the right or left external jugular vein is used for the construction of bisaccluar and broad-neck aneurysms. The internal-external (asterisk) or transverse-external (double asterisks) jugular vein bifurcation serves as a graft for the creation of bilobular aneurysms.

Fig 3.

Surgical steps of the conventional microsurgical saccular (berry-shaped) venous pouch bifurcation aneurysm model. A, Anastomosis sequences on the back side of the aneurysm (white arrows): 1) The LCCA is sutured to the RCCA. 2) The VP is sutured to the RCCA. 3) The VP is sutured to the LCCA. B, Anastomosis sequences on the front side of the aneurysm (black arrows): 4) The LCCA is sutured to the RCCA. 5) The VP is sutured to the RCCA. 6) The VP is sutured to the LCCA.

Fig 4.

A, The screenshots illustrate 2D-DSA measurements, including parent vessels and aneurysm length, width, and neck in reference to an external sizing device (highlighted inset boxes). B, The same vessel and aneurysm characteristics are measured in CE-3D-MRA.