Isolating the Effect of Arch Architecture on Aortic Hemodynamics Late After Coarctation Repair: A Computational Study

Abstract

ObjectivesEffective management of aortic coarctation (CoA) affects long-term cardiovascular outcomes. Full appreciation of CoA hemodynamics is important. This study aimed to analyze the relationship between aortic shape and hemodynamic parameters by means of computational simulations, purposely isolating the morphological variable.MethodsComputational simulations were run in three aortic models. MRI-derived aortic geometries were generated using a statistical shape modeling methodology. Starting from n = 108 patients, the mean aortic configuration was derived in patients without CoA (n = 37, “no-CoA”), with surgically repaired CoA (n = 58, “r-CoA”) and with unrepaired CoA (n = 13, “CoA”). As such, the aortic models represented average configurations for each scenario. Key hemodynamic parameters (i.e., pressure drop, aortic velocity, vorticity, wall shear stress WSS, and length and number of strong flow separations in the descending aorta) were measured in the three models at three time points (peak systole, end systole, end diastole).ResultsComparing no-CoA and CoA revealed substantial differences in all hemodynamic parameters. However, simulations revealed significant increases in vorticity at the site of CoA repair, higher WSS in the descending aorta and a 12% increase in power loss, in r-CoA compared to no-CoA, despite no clinically significant narrowing (CoA index >0.8) in the r-CoA model.ConclusionsSmall alterations in aortic morphology impact on key hemodynamic indices. This may contribute to explaining phenomena such as persistent hypertension in the absence of any clinically significant narrowing. Whilst cardiovascular events in these patients may be related to hypertension, the role of arch geometry may be a contributory factor.

Using computed tomography angiography and computational fluid dynamics to study aortic coarctation in different arch morphologies

“…Meanwhile, the sharp corners of the gothic arch could lead to greater pressure changes, which adversely affect the cardiovascular system. Increased aortic arch WSS causes structural changes in the aortic wall, increased stiffness, and decreased compliance, and long-term changes lead to progressive damage and pathological remodeling of vascular structure ( 31 , 32 ), and eventually may lead to ascending thoracic aneurysms (ATAA) ( 33 ).…”

Coarctation of the Aorta: Diagnosis and Management

“…Distinct arch features including characteristics associated with a gothic arch correlated to these indices of cardiac function, a finding which has been replicated in other studies. [ 49 ] Flow characteristics of CMR-derived aortic geometries have also been studied through computer simulation to assess the impact of arch shape on flow characteristics, with repaired CoAs demonstrating higher wall shear stress in the descending aorta compared to normal aortas, even where no residual stenosis is present [ 50 ]. Thus, we are likely at the beginning of being able to phenotype this patient population in a far more detailed way than previously, with important implications for improving risk stratification and a more personalised approach to treating individual patients with unique anatomical characteristics.…”