The bird beak configuration has no adverse effect in a magnetic resonance functional analysis of thoracic stent grafts after traumatic aortic transection.

BACKGROUND: This study used magnetic resonance imaging (MRI) to analyze functional long-term outcome after endovascular repair of blunt aortic injury.

METHODS: This prospective study enrolled 27 of 53 patients who were treated between 1999 and 2008. Patients underwent functional multidimensional contrast-enhanced MRI with flow analysis or compliance measurements of the aorta, or both. Ten patients were treated with the Medtronic Valiant (Medtronic World Medical, Sunrise, Fla), 14 patients received a Gore TAG (W. L. Gore & Associates, Flagstaff, Ariz), and two received a C (conformable)-TAG (W. L. Gore & Associates) stent graft. For several patients, repetitive measurements over time could be done. Median follow-up was 3.92 ± 2.7 years. The MRI parameters were: three-dimensional flow: echo time/repetition time = 3.1/5.3 ms, Δx(pixel density) = 2.5 × 2.5 × 3 mm(3); respiratory navigator, α = 15°, venc(encoding velocity) = 200 cm/s along anterior-posterior, right-left, and foot-head direction, 40 cardiac phases. Cine: echo time/repetition time = 1.7/3.4 ms, Δx(pixel density) = 1.2 × 1.2 × 6 mm(3), breathhold, α = 60°, 40 cardiac phases.

RESULTS: The flow analysis showed flow acceleration at the proximal end of the stent graft, with higher values in patients with a nonoptimal alignment of the stent graft. No differences were found between different devices (median acceleration was 75.99 ± 37.98 cm/s for Gore and 71.59 ± 17.22 cm/s for Medtronic). The values were stable during follow-up. In the compliance analysis, the part of the aorta covered with the stent graft showed nearly no expansion, whereas the ascending and descending aorta showed normal expansion. This behavior did not change over the time. At the proximal end of the stent graft, a slight compression could be noted (-0.5 ± 0.14 mm), except in those patients with a C-TAG device from Gore.

CONCLUSIONS: Functional analysis showed no adverse long-term outcome of the bird beak configuration of stent grafts in the aortic arch after endovascular repair after blunt aortic injury.