Magnitude of the forces acting on target vessel stents as a result of a mismatch between native aortic anatomy and fenestrated stent-grafts.

PURPOSE

To quantify the compression force acting on target vessel stents as a consequence of the misalignment between the native aortic anatomy and the fenestrated stent-graft owing to measuring errors during the design of the device.

METHODS

The material properties of a fenestrated Zenith stent-graft were determined using a standardized tensile testing protocol. Aortic anatomy was modeled using fresh porcine aortas that were subjected to tensile testing. The net force acting on a target vessel stent due to incremental discrepancy between the target vessel ostia and the stent-graft fenestrations was calculated as the difference in wall tension between the aorta and the stent-graft in diastole and systole. The change in diameter between diastole and systole was set to 8%.

RESULTS

Using the diastole model, underestimation of circumferential target vessel position by 15°, 22.5°, and 30° resulted in net forces on the target vessel stent of 0.6, 0.8, and 1.1 N, respectively. Overestimation of target vessel position by the same increments resulted in net forces of 0.3, 0.6, and 0.9 N, respectively. With the systolic model, underestimating target vessel position by 30° resulted in a 2.1-N maximum force on the stent, which potentially threatened the seal. In the longitudinal direction, underestimating target vessel separation by up to 10 mm resulted in a maximal force on the stent of 6.1 N, while overestimating target vessel separation did not result in any additional force on the stent due to fabric infolding.

CONCLUSION

The magnitude of the forces generated solely due to mismatch between stent-graft design and native anatomy is modest and is unlikely to cause significant deformation of target vessel stents. Mismatch, however, may cause loss of seal.