Aortic compliance following EVAR and the influence of different endografts: Determination using dynamic MRA

Purpose: To utilize dynamic magnetic resonance angiography (MRA) to characterize aortic stiffness (β) and elastic modulus (Ep) as indexes of wall compliance during the cardiac cycle and determine any influence of different endograft designs or the presence of endoleaks on these indexes. Methods: Eleven consecutive patients (11 men; median age 74 years, range 63-78) with abdominal aortic aneurysm (AAA) selected for endovascular repair were scanned pre- and postoperatively. Aortic area and diameter changes during the cardiac cycle were determined using dynamic MRA at 4 levels: 3 cm above the renal arteries, between the renal arteries, 1 cm below the renal arteries, and at the level of maximum aneurysm sac diameter. Ep and β were calculated. Data are presented as median (range); p<0.05 was considered significant. Results: Preoperatively, Ep and β were significantly higher at the level of the aneurysm sac compared to all other levels (p<0.05). Following EVAR, stiffness increased at this level (p<0.05). After implantation, patients with an Excluder endograft demonstrated Ep and β measurements at the aneurysm neck that were 94% and 60% higher, respectively, compared to those with a Talent (p<0.05) endograft. The presence of an endoleak had no effect on Ep or β. Conclusion: This study introduces the feasibility of dynamic MRA imaging-based calculations of aortic elastic modulus and stiffness. AAA patients demonstrate increased Ep and β at the level of the aneurysm sac. EVAR results in increased aneurysm sac Ep and β. Stent-graft design seems to alter Ep and β within the aneurysm neck, which may have consequences for endograft durability. The presence of an endoleak does not seem to have an effect on Ep or β.