Improvement in conformability of the latest generation of thoracic stent grafts

Poor aortic arch apposition increases the risk of technical failure after thoracic endovascular repair. The aim of this study was to assess the conformability of the latest generation of thoracic stent grafts in relation to the degree of device oversizing and aortic arch angulation.

A benchtop pulsatile flow model was designed to test stent graft anchorage in a 2-cm-long proximal landing zone at varying landing zone angles (from 140° down to 70°) and stent graft oversizing (12%-28%). The experiments were performed using 10 human thoracic cadaveric aortas and four stent grafts: C-TAG, Zenith TX2 Pro-Form, Valiant Captivia, and Relay. Device-wall apposition was measured as a function of landing zone angulation and oversizing during static and dynamic (60 pulses/min, 300/150 mm Hg) tests.

The Valiant stent graft remained apposed to the aortic wall at each increment of neck angulation and device oversizing. Lack of apposition of the proximal anchorage segment was observed with the C-TAG above 120° landing zone angulation (1-2 mm) and with the Relay above 110° landing zone angulation (1-4 mm). Lack of "body" apposition (1-4 mm) was first observed with the Zenith Pro-Form stent graft above 110° angulation (P = .001). When the device was not apposed to the aortic wall, an increase in stent graft oversizing significantly (P = .01) decreased device-wall apposition.

The requirement for close conformability has influenced the design of next-generation devices. Manufacturers have modified devices and/or their deployment system to specifically address this problem. When compared with the results of our previous experimental test, this study demonstrates that these alterations have resulted in a marked improvement in the performance of commercially available stent graft systems.