Hemodynamics Changes in Aortic Flux Due to TEVAR Quantified by 4D-flow-MRI

Abstract

Introduction: TEVAR (Thoracic endovascular aortic repair) in traumatic aorta injury has shown good long-term results (1). The interaction between endograft and the dynamic anatomy of the thoracic aorta is not well characterized for repetitive physiologic stressors and subsequent issues related to long-term durability. TEVAR could also modify the flow and in the long term increase the risk of cardiovascular diseases (2). The alteration of flow characteristics in the heart and aorta have been related to atherosclerosis, aneurysms, and hypertension (3). The hemodynamic patterns alterations that occur in the aorta after performing TEVAR have not been previously described. The description of these changes could help us understand the pathophysiology of these diseases. The aim of our study was to quantify these changes using 4D-flow-MRI by comparing between healthy volunteer (HV) and TEVAR in trauma patient. Methods: Both individuals underwent non-contrast-enhanced 4D flow-MRI, obtaining flow field and 3D angiography. Geometric and flow parameters were determined at 20 planes positioned from sinotubular junction to proximal DAo. Local vortex characterization was obtained through the computation of in-plane rotational flow (IRF, helical flow) at peak systole and systolic flow reversal ratio (SFRR) (figure 1.A), i.e. the ratio of forward to backward through-plane systolic flow obtained by the time-integral over systolic phases, which is also known as systolic backward flow. Peak-systolic wall shear stress (WSS) was calculated at 64 points equally distributed on the segmented vessel contour. Contour-averaged axial (WSSax) and circumferential WSS (WSScirc) were obtained. Results: The patient with TEVAR presented an abnormal inversion of the direction of the in-plane circulation. Proximal to TEVAR both the patient and the HV presented a clockwise IRF of around 35 cm2/s. However, inside and shortly distally of the TEVAR the patient presented a marked and sustained counterclockwise direction (IRF = -30 cm2/s) while the HV presented clockwise rotation (IRF = 20 cm2/s) (figure 1.B). Similarly, circumferential WSScirc was reversed through the whole length of the TEVAR (figure3). Of note, WSSax was markedly reduced all along the length of the TEVAR (figure 1.C) Conclusion: The presence of TEVAR was associated with abnormal behavior of rotational flow whose eventual consequences are unknown. The reduced friction of the TEVAR inner surface may have repercussion on axial WSS.