1351900 - The effect of Aortic Valve Replacement on 4D Flow-assessed aortic parameters in patients with Bicuspid and Tri-leaflet Aortic Valves with severe Aortic Stenosis

Altered haemodynamic flow patterns in the aorta are linked with increased risk of bicuspid aortic valve (BAV)-associated aortopathy(1-3). The effect of aortic valve replacement (AVR) on these abnormal aortic blood flow patterns, and whether differences exist between individuals with BAV and tri-leaflet aortic valves (TAV), is not clearly established.

Methods:

Four-dimensional flow-cardiac magnetic resonance imaging (4DF-CMR) of the aorta was performed in patients with BAV and TAV and severe symptomatic aortic stenosis (AS), before and 12 months after AVR. Healthy individual with TAV morphology but no significant valve dysfunction were recruited as controls. In-plane peak systolic velocity and maximum wall shear stress (WSS) were quantified on 2D analysis planes at the aortic root and distal ascending aorta using commercially available software. In-house Matlab code was used to quantify vortical flow by 3D volumetric calculation of the velocity, vorticity and Lambda2-criterion values (following 3D segmentation of the ascending aorta from the aortic root to the level of pulmonary artery bifurcation, Figure 1). Negative Lambda2 scalar values, derived from velocity field gradients, locate vortical cores since they reflect pressure minimums in a plane across the vortex, with more negative values representing greater vorticity. Parameters (mean  ± standard error) were compared in the BAV and TAV pre- and post-AVR patient groups and with the TAV controls.

Results:

32 patients with severe symptomatic AS (11 BAV, 21 TAV; mean age 68±10 years) and 9 age-matched controls (9 TAV; mean age 58±4 years) were prospectively recruited. Comparing pre-AVR to post-AVR parameters, significant improvements in peak velocity and vorticity parameters were noted for TAV patients, but these remained significantly higher than the TAV controls (Table 1). For the BAV patients, although numerical improvements of similar magnitude were noted in most parameters post-AVR, these differences did not reach statistical significance, and were again significantly higher compared to the TAV controls. No change in WSS was noted. There were no significant differences in 4DF-CMR parameters between the post-AVR BAV subgroup compared with the post-AVR TAV subgroup.

Conclusion: Most velocity and vorticity parameters measured by 4DF-CMR in the ascending aortas of individuals with severe AS improved post-AVR, reaching significance in TAV patients. There was no differences between BAV and TAV post-AVR parameters and both remained significantly higher than controls. The smaller effect of AVR suggests altered flow dynamics, especially accentuated vortical flow, are already present in individuals with BAV morphology without significant valve dysfunction. The similar changes to flow abnormalities demonstrated by both BAV and TAV morphologies post-AVR suggest that the ongoing risk of aortic complications may not be greater in BAV.