Impacts of Thoracic Endovascular Aortic Repair and Thrombus Load on Aortic Radial Deformation

Purpose: Aortic stiffness and intraluminal thrombus at baseline have been suggested as potential determinants of the impact of aortic endovascular devices on aortic wall properties. We aim to assess the impact of the endograft and of thrombus load on aortic compliance through the assessment of changes in aortic radial deformation following thoracic endovascular aortic repair (TEVAR). Materials and Methods: The 3D geometric models of the aorta at peak systole and end diastole were constructed from both pre- and post-TEVAR 4D flow magnetic resonance imaging (MRI) of aortic aneurysm and dissection patients. Arclength, length-averaged curvature, and true- and whole lumen effective diameters and areas were assessed in different aortic segments (ascending aorta, endografted segment, and all aorta). Aortic radial deformation was defined as percentage change in aortic diameter from diastole to systole. Thrombus load was defined as thrombus volume divided by aortic volume. Spearman’s coefficient (R) was calculated to assess linear correlations. Results: The analysis was conducted on 14 patients/TEVAR procedures (n=7 aneurysms, n=7 dissections). Median time between pre- and postoperative MRI was 124.6 ± 81.7 days. Aortic radial deformation significantly decreased in the endografted segment (7.2% ± 3.6% vs 5.0% ± 2.0%, p<0.05), whereas it significantly increased in the ascending aorta (6.2% ± 2.3% vs 14.4% ± 4.0%, p<0.05). No significant impact was observed on axial deformation (length change) and bending pre-to-post-TEVAR in those 2 segments. Regarding changes in geometry, cardiac cycle-averaged ascending aortic diameter was found similar pre-to-post TEVAR (3.7 ± 0.3 cm vs 3.6 ± 0.4, p=0.23). Thrombus load at the level of the diseased thoracic aorta at baseline correlated strongly with the amplification in ascending aorta radial deformation (R=−0.80, R 2 =0.64), and in an even more significant manner when excluding the 2 patients with a history of prosthetic ascending aorta replacement (R=−0.88, R 2 =0.77). Conclusion: Following TEVAR, aortic radial deformation, is reduced in the stented segment and amplified in the ascending aorta. Greater baseline thrombus load results in lower radial deformation amplification post-TEVAR. These findings highlight the benefit of thrombus load assessment pre-TEVAR and the need for increasing the compliance of future grafts to minimize its impact. Clinical Impact Following thoracic endovascular aortic repair (TEVAR), aortic radial deformation, directly related to aortic compliance, is reduced in the stented segment, and amplified upstream in the ascending aorta, likely due to increased stiffness of the endograft, remodeling, and pressure pulse reflection. Thrombus load is found as an effective predictor of aortic radial deformation amplification following TEVAR. This highlights the benefit of thrombus assessment pre-TEVAR and the need for increasing compliance of future graft designs to minimize its impact.