Abstract
Purpose
To assess numerically the flexibility and mechanical stresses undergone by stents and fabric of currently manufactured stent-grafts.
Methods
Eight marketed stent-graft limbs (Aorfix, Anaconda, Endurant, Excluder, Talent, Zenith Flex, Zenith LP, and Zenith Spiral-Z) were modeled using finite element analysis. A numerical benchmark combining bending up to 180° and pressurization at 150 mmHg of the stent-grafts was performed. Stent-graft flexibility, assessed by the calculation of the luminal reduction rate, maximal stresses in stents, and maximal strains in fabric were assessed.
Results
The luminal reduction rate at 90° was <20% except for the Talent stent-graft. The rate at 180° was higher for Z-stented models (Talent, Endurant, Zenith, and Zenith LP; range 39%–78%) than spiral (Aorfix, Excluder, and Zenith Spiral-Z) or circular-stented (Anaconda) devices (range 14%–26%). At 180°, maximal stress was higher for Z-stented stent-grafts (range 370–622 MPa) than spiral or circular-stented endografts (range 177–368 MPa). At 90° and 180°, strains in fabric were low and did not differ significantly among the polyester stent-grafts (range 0.5%–7%), while the expanded polytetrafluoroethylene fabric of the Excluder stent-graft underwent higher strains (range 11%–18%).
Conclusion
Stent design strongly influences mechanical performances of aortic stent-grafts. Spiral and circular stents provide greater flexibility, as well as lower stress values than Z-stents, and thus better durability.
Keywords
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