Backward Aortic Flow Is Associated with Impaired Left Ventricular Mechanics in Young Adults with Bicuspid Aortic Valve: A Prospective Cardiovascular Magnetic Resonance Study.

Objectives: The presence of a bicuspid aortic valve (BAV) is known to alter transvalvular flow and increase shear stress on the ascending aorta, contributing to alterations in aortic geometry and the progression of BAV-related aortopathy. The purpose of the current study was to characterize aortic flow abnormalities and their associations with aortic geometry and ventricular mechanics using cardiac magnetic resonance imaging (CMR). Methods: In this prospective cross-sectional study, 56 young adults with CMR-confirmed BAV and 56 age- and sex-matched healthy volunteers underwent standardized CMR. Biventricular volumes and function, LV global longitudinal strain (LV-GLS), LV torsional mechanics, ascending aortic geometry, pulse-wave velocity, aortic distensibility, and two-dimensional phase-contrast-derived forward and backward flow parameters were quantified. Associations between myocardial mechanics and haemodynamic variables were assessed using correlation analyses and multivariable linear regression. Results: Compared with healthy controls, patients with BAV exhibited preserved LV ejection fraction but impaired LV-GLS, reduced LV torsion, increased aortic stiffness, and a significantly greater backward-flow burden despite similar net aortic flow (all p < 0.001). Higher peak backward-to-forward flow-rate ratios were associated with less negative LV-GLS (p = 0.006), whereas greater aortic regurgitant volume was also associated with impaired longitudinal deformation (p = 0.001). In multivariable analysis, LV-GLS and aortic regurgitant volume remained associated with the peak backward-to-forward flow-rate ratio within the specified model, whereas ascending-aortic dimensions were not. The final model explained 52% of the variability in backward-flow burden. Conclusions: CMR identified a subclinical ventricular-aortic phenotype in young adults with BAV characterized by altered LV mechanics, increased aortic stiffness, and greater relative backward-flow burden despite preserved conventional LV systolic function. The association between backward-flow burden and LV longitudinal mechanics suggests that these abnormalities may represent interrelated manifestations of BAV disease; however, their temporal and causal relationships cannot be established from this cross-sectional study.