Abstract 10478: Comprehensive Mechanical Modelling of Thoracic Endovascular Aortic Repair in Type A Aortic Dissection

Abstract

Background: Thoracic endovascular aortic repair (TEVAR) in selected proximal (Stanford type A) aortic dissection (TAAD) cases has been reported, however, the limitation and criteria for TEVAR applied in TAAD remain controversial. Virtual stent-graft (SG) deployment simulation based on the finite element method is an emerging tool that allows TEVAR to be reproduced for detailed analysis of biomechanical interaction between native vessel wall and SG device. Methods: A TAAD patient underwent an unsuccessful TEVAR followed by salvage open surgical repair. Pre-TEVAR CT angiogram was used to establish the 3D geometry of the dissected aorta for later analysis. Perioperative DSA was used to measure the aortic root motion and determine SG position in the simulation model. Specimen of the harvested aortic tissue was used for histological analysis and tensile test to define isotropic hyperelastic properties of the aortic wall. Results: Aortic root motion was decomposed into a component normal to the sinotubular junction (STJ) and a component parallel to the STJ. The largest motion was 4.14 mm in normal direction and 3.5 mm in parallel direction. The continuous motion was used to define the displacement boundary condition at the aortic root in a finite element model. The histology revealed preserved both elastic fibres and collagen at the proximal landing zone. A small area of inflammatory infiltration was noted at the tunica externa which may related to the dissected lamella. Tensile testing showed that the aortic wall ruptured at the stress of 250-1250 kPa while the lamella ruptured at 80-160 kPa. Simulation precisely reproduced the SG configuration after TEVAR procedure. Maximum principal stress at 301 kPa was found on the lamella during simulation, which is significantly higher than stress tolerance of the lamella. Conclusion: Microstructure of the lamella and aortic wall components determine the capacity in resisting SG induced focal stress. During the deployment, the proximal end of SG landed directly onto the lamella where the maximum stress exceeded the tolerance of the lamella thus causing rupture and allowing the SG to penetrate into the false lumen.