Cine MRI Assessment of Aortic Aneurysm Dynamics before and after Endovascular Repair

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Abstract
Purpose: To evaluate stent-graft and aneurysm wall motions during the cardiac cycle using cine magnetic resonance imaging (MRI) to identify mechanisms of long-term failure of endovascular aneurysm repair (EVAR). Methods: Prior to and after EVAR in 7 patients with abdominal aortic aneurysms (AAA), 12 MRI images per cardiac cycle were acquired in transverse, sagittal, and coronal planes of the aneurysm. Two independent observers blinded to the aim of the study manually traced stent-graft and aneurysm wall contours. Translation was defined as the maximal displacement of the contours in the peak-systolic image compared to the end-diastolic image. Aneurysm wall motions before and after repair were compared. Stent-graft and aneurysm configuration changes during the cardiac cycle were evaluated. The relation between translation and the degree of angulation of the stent-graft was calculated. Results: The anteroposterior translation of the aneurysm decreased from a median 1.05 mm (range <0.5–1.29) before EVAR to within pixel size (<0.5 mm) after EVAR (p=0.04). The cranial-caudal translation of the aneurysm increased from a median 1.01 mm (range 0.05). Conclusions: After EVAR, increased longitudinal translation of both the aneurysm and stent-graft was observed, indicating downward pulling forces at the proximal fixation site. Secondly, increased bending was seen at the site of maximal angulation, which implies a risk of metal fatigue and fabric damage at sites of stent-graft angulation.