(A-11) A Computational Fluid Dynamics Model of Seal Zone Stability in Endovascular Aneurysm Repair

Introduction:: Long-term durability of endovascular aneurysm repair (EVAR) is often compromised due to inadequate sealing of the endograft to the aorta. We hypothesize that geometric mismatch between the aorta and endograft can lead to the development of bird-beak regions, type Ia endoleaks, and endograft migration. Our novel computational model shows how geometric incompatibility at the seal zone contributes to endoleak formation and propagation.


Materials and Methods:: Using finite element modeling, we simulated endograft crimping and deployment in pressurized aortic models with different degrees of curvature (0º, 30º, 60º) and oversizing (0%, 20%, 25%). We then performed computational fluid dynamics (CFD) modeling with a detailed pressure analysis of various regions along the length of each model to determine the effects of shape and oversize on the stability of seal zone.


Results, Conclusions, and Discussions:: Results

We observed that curvature and oversizing introduced geometric incompatibilities that compromised the aorta-endograft seal. CFD analysis showed low-velocity endoleaks develop in these regions of compromised seal. Pressure analysis showed both higher and lower static pressures develop in the endoleak regions, resulting in heterogeneous pressure gradients between the endoleak and bulk flow.


Conclusions

We present one of the first computational models to study the sensitivity of seal zone mechanics to the degree of aorta-endograft mismatch. Our finding of pressure gradients that exist between the endoleak and bulk flow may represent regions of high mechanical instability that may further propagate the endoleak. Our results highlight the importance of shape and oversizing considerations when selecting the appropriate endovascular therapy for EVAR patients.


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