Flow displacement and increased circumferential wall shear stress predict ascending aortic dilatation: a prospective 5-year follow-up study

Background Ascending aortic (AA) dilatation is a significant condition that can lead to life-threatening complications such as aortic rupture or dissection. While the exact mechanisms of aortic dilatation are not fully understood, hemodynamic factors such as flow displacement (FD) and wall shear stress (WSS) have been identified as potentially influencing the progression of aortic enlargement. Four-dimensional (4D) flow magnetic resonance imaging (MRI) has become an important tool for studying these hemodynamic parameters. Purpose The primary objective of this study was to investigate whether baseline 4D flow MRI parameters, specifically flow displacement (FD) and wall shear stress (WSS), can predict increases in aortic diameter over a 5-year follow-up period in patients with ascending aortic dilatation and anatomically normal tricuspid aortic valves (TAV), without known genetic syndromes. The study aimed to determine whether these hemodynamic parameters could serve as non-invasive biomarkers for identifying patients at risk of progressive aortic dilatation. Methods A prospective cohort of 47 patients with ascending aortic dilatation and 15 healthy controls underwent baseline and 5-year follow-up MRI scans, including 4D flow analysis. Aortic diameters were measured at the sinus of Valsalva and mid-ascending aorta. FD and WSS were quantified in 10 standardized planes of the thoracic aorta. Statistically significant aortic growth was determined based on measurement error thresholds. Results Over the 5-year follow-up period, 29.8% (n = 14) of patients with AA dilatation experienced statistically significant aortic growth. In the patients with significant aortic growth, the median baseline FD at the sinus of Valsalva was 5.5%, compared to 3.0% in patients without significant aortic growth (p = 0.02). In patients with aortic growth, FD strongly correlated with increased circumferential WSS in the outer curvature of the ascending aorta (r = 0.58–0.78, p < 0.05). Other 4D flow parameters and WSS alone did not show associations with aortic growth. Conclusion FD, along with increased circumferential WSS at the sinus of Valsalva, was associated with increased aortic diameter in patients with ascending aortic dilatation and normal TAV. These parameters may serve as non-invasive biomarkers for identifying patients at risk for progressive aortic dilatation and guiding follow-up imaging strategies.