Biomechanical insight of the stent-induced thrombosis following flow-diverting strategy in the management of complicated aortic aneurysms.

Abstract:

BACKGROUND: The flow-diverting stent (FDS) emerges as an alternative strategy in treating complicated aortic aneurysms. However, the biomechanical behavior of the stent-induced thrombus (SIT) remains little understood. This study sought to investigate the impact of SIT on aneurysm wall stress and strain distribution and offer basic evidences for its large-scale application. METHODS: Aortic aneurysms treated with FDS and followed up over 5 years were selected. Case-specific models were created based on the pre-operative and 12 months follow-up imaging. The aortic central line was generated, perpendicular to which the slice with maximum aneurysm diameter was selected for two-dimensional modeling. Pre- and post-stenting models were compared, with emphasis laid on wall stress distribution and risk factors leading to local stress concentration. Clinical follow-up data was recorded to verify the biomechanical findings. RESULTS: A total of 6 cases (3 females, average age 56.3±17.2 years) were enrolled in this study. Complete sac thrombosis was documented in 5 cases at 12 months, while residual perfusion was seen in the remaining one. With the formation of SIT, the average wall tensile stress dropped from 58.60±11.11 KPa to 23.56±12.05 KPa (P=0.001) at diastolic phase, and from 88.00±15.94 KPa to 36.02±18.31 KPa (P=0.001) at systolic phase. Intra-wall calcium plaque and irregular, spontaneous intraluminal thrombus were recognized as risk factors for local stress concentration, which could be mitigated by the regular, well-organized SIT. Long-term follow-up at 5 years showed significant aneurysm shrinkage from 57.7±16.2 mm to 51.0±13.7 mm (P=0.009). CONCLUSIONS: The formation of SIT after FDS implantation might protect the aneurysm by reducing the wall tensile stress and erasing the local stress concentration. Clinical follow-up data seems to support the biomechanical role of SIT, but a larger study cohort is needed. A comprehensive understanding of SIT including both biomechanical and biological perspectives is warranted to draw an exhaustive conclusion.