Changes in Ascending Aortic and Aortic Arch Secondary Flow Patterns Following Endovascular Repair of the Descending Thoracic Aorta

Objective: This study aimed to assess modifications of aortic secondary flow patterns following thoracic endovascular aortic repair (TEVAR) using four dimensional flow magnetic resonance imaging (4D flow MRI). Methods: FASCAT is a French, prospective, observational, single centre study. All included patients underwent cardiac MRI, including aortic magnetic resonance angiography and 4D flow MRI acquisition, before and three months after TEVAR. Visual and quantitative aortic flow patterns were assessed using Tempus Pixel Cardio and cvi42 software. Basic 4D flow MRI metrics—such as aortic forward flow (AFF), aortic reverse flow (ARF), aortic net flow (ANF), and peak and mean velocities—were initially assessed. 4D flow MRI derived advanced metrics—such as pulse wave velocity (PWV) related to aortic stiffness, flow ejection angle, flow eccentricity (ECC), and mean systolic fraction of reverse flow (FRF)—and their duration over systole (FRFd_sys and ECCd_sys, respectively) were also measured on pre- and post-operative MRIs. Results: The analysis was conducted on 15 TEVAR procedures in 14 patients (seven aneurysms and seven dissections). The median time between pre- and post-operative MRI was 122.8 days. PWV statistically significantly increased within the stented segment (17.8 ± 12.1 cm/s vs. 9.4 ± 8.5 cm/s; p = .005), while it statistically significantly decreased upstream of the graft (8.8 ± 9.1 cm/s vs. 4.9 ± 6.2 cm/s; p = .035) post TEVAR. No statistically significant changes were found in terms of mean AFF, ANF, velocities, or flow ejection angle pre to post TEVAR. Mean systolic FRF statistically significantly decreased post TEVAR (37%, 26%, and 48% at the sinotubular junction, mid ascending aorta, and TEVAR inlet, respectively). FRFd_sys and ECCd_sys also statistically significantly decreased post TEVAR. Conclusion: This pre to post TEVAR 4D flow MRI study found a statistically significant decrease in ARF and ECC upstream of the graft, suggesting improved upstream aortic flow fields post TEVAR.