The best in vitro conditions for two and three parallel stenting during endovascular aneurysm repair.

OBJECTIVE: The aim of this study is to identify which endograft-parallel stent combinations and which degree of oversizing result in the most adequate fit in a juxtarenal abdominal aneurysmal neck, when using a double or triple parallel-stent (chimney) technique. METHODS: In vitro silicon, juxtarenal, abdominal aortic aneurysmal neck models of different diameters, with two and three side-branches (simulating both the renal and superior mesenteric arteries), were constructed. Two different endografts of three diameters each, with two or three parallel stents (of 6 mm and 6 mm; or 6 mm, 6 mm, and 8 mm) were tested (Endurant-II endograft [Medtronic Inc, Santa Rosa, Calif] with balloon-expandable BeGraft stent [Bentley InnoMed, Hechingen, Germany] and an Excluder endograft [W. L. Gore and Associates, Flagstaff, Ariz] with self-expanding Viabahn stent [W. L. Gore and Associates]), applying three endograft-oversizing degrees: recommended (15%), excessive (30%), and over-excessive (40%). After remodeling, using the kissing-balloon technique at 37°C (98.6°F), 36 endograft-stent-oversizing models were scanned by computed tomography. The area of the gutters, parallel-stent compression, and main endograft infolding were recorded. RESULTS: Increasing oversizing (15%, 30%, and 40%) revealed a nonsignificant propensity toward smaller gutters and similar parallel-stent compression, but it significantly augmented infolding, more in three parallel-stent models (0%, 0%, 67% and 0%, 33%, 83% of cases; P = .015 and .018, for two and three parallel-stent models; n = 36) and mainly for the Excluder-Viabahn combination. The Excluder-Viabahn showed significantly smaller gutters, but with higher stent compression, than Endurant-BeGraft combinations for both two and three parallel stents (8.2 mm2, 22.6 mm2; P = .002 and 14.4 mm2, 23.3 mm2; P = .009 gutter area; and 18%, 2%; P < .001 and 15%, 2%; P = .007 relative stent area compression, respectively). CONCLUSIONS: Better endograft stent apposition was usually attained when using 30% oversizing during two and three parallel-stent techniques. Higher oversizing was related to nonsignificant smaller gutters but higher rates of infolding. Smaller gutters, but higher stent compression and risk of infolding, were achieved with the Excluder-Viabahn than with the Endurant-BeGraft combination.