The effect of aortic valve replacement on 4D flow-measured flow displacement in patients with bicuspid and tri-leaflet aortic valves with severe aortic stenosis

Abstract

Abstract Introduction Eccentric outflow jet direction in the ascending aorta is correlated with the altered haemodynamic flow patterns thought to contribute to bicuspid aortic valve (BAV)-associated aortopathy. Purpose We aimed to analyse the impact of surgical aortic valve replacement (AVR) on outflow jet displacement in the ascending aorta, and determine if differences exist between individuals with BAV and tri-leaflet aortic valves (TAV). Method Four-dimensional flow-cardiac magnetic resonance imaging (4D Flow) of the aorta was performed in prospectively recruited patients with BAV and TAV and severe symptomatic aortic stenosis (AS), before and 12 months after AVR. Healthy individuals with BAV and TAV morphology, but no significant valve disease, were also recruited as controls. Outflow direction was calculated from the in-plane, normalised flow displacement (NFD), defined as the distance between the centre of the aortic lumen (Clum) and the centre of velocity (Cvel) of the forward flow and normalised to the lumen diameter (Figure 1). Mean NFDs were evaluated at peak systole on planes perpendicular to 25 equidistant nodes along the centreline between the aortic root to the level of the pulmonary artery bifurcation in all subjects using custom Matlab code. Results 32 subjects with severe symptomatic AS (BAV n=11, TAV n=21; mean age 68±10 years) and 17 controls (BAV n=8, TAV n=9; mean age 57±7 years) were assessed (Table 1). In those with TAV, there were no differences in NFD between patients with severe AS pre-AVR compared to post-AVR, or compared to TAV controls. However, in BAV subjects, pre-AVR BAV patients with severe AS had a significantly higher mean NFD compared to BAV controls, and compared to pre-AVR TAV patients with severe AS. Post-AVR, there was no longer a significant difference in mean displacement between BAV vs TAV. Conclusion Our observations suggest that the BAV morphology plays a predominant role in the abnormal eccentric flow displacement in the ascending aorta, which may be normalised following bioprosthetic valve replacement. This may have implications for monitoring aortas post-AVR in BAV subjects.