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.

Parallel-Stenting Technique in a Sandwich Configuration for Hypogastric Artery Preservation during Endovascular Aneurysm Repair: An In Vitro Study.

BACKGROUND: The aim of the study was to identify the best conditions in iliac sandwich procedure for hypogastric artery preservation during endovascular aneurysm repair, testing different devices, different oversizing (OS) degrees as well as different methods to measure it. METHODS: Four external iliac devices (16-mm Endurant and 12-mm Aorfix limb extensions; 11- and 13-mm Viabahn endografts) were tested with 2 distinct internal iliac stent grafts (8-mm Advanta V12 and 8-mm Viabahn) inside different proximal silicon iliac limb models (10, 12, 14, 16, and 18 mm), simulating an iliac sandwich procedure for hypogastric preservation. After remodeling all devices in a saline bath at 37°C, the combinations were computed tomography scanned. Gutter size, parallel-stent compression, and inadequate parallel-stent deployment or infolding were recorded. Oversizing between both parallel stents and the iliac limb models were examined in terms of added diameter, perimeter, and area being additionally compared. RESULTS: All three sizing methods (diameter, perimeter, and area) were highly correlated (diameter OS to perimeter and area OS correlation coefficient 0.998 and 0.997, respectively, P < 0.001 for both); thus, diameter OS was used for further comparisons. Increasing diameter OS (< 30%, 30-55%, 55-75%, and > 75%) showed a significant tendency toward smaller gutters (38.9, 12.2, 5.4, and 2.6 mm2, respectively, P < 0.001) but also increasing parallel-stent compression (13.5%, 28.9%, 43.9%, and 55.1%, P < 0.001) and infolding (0%, 0%, 38%, and 60%, P < 0.001). There were no significant differences between the analyzed devices. CONCLUSIONS: In iliac sandwich procedures, better apposition is usually achieved when using 30-55% diameter OS; higher OS is related to smaller gutters but higher rates of malpositioning and parallel-stent compression. No clear recommendations in material selection can be performed. All sizing methods are highly correlated and predictable.