Peak regurgitant diastolic wall shear stress increases in bicuspid aortic valve regurgitation: association of regurgitation severities and aortic root dilation

Abstract

Background: Bicuspid aortic valve (BAV) disease, especially with regurgitation, lacks adequate clinical management. While root aortopathy is often attributed to genetic factors and aortic regurgitation, the diastolic hemodynamic characteristics in BAV patients with varying regurgitation severities are not well understood. Flow-derived velocity-weighted flow displacement (FD) and wall shear stress (WSS) are linked to aortopathy progression. We sought to evaluate peak systolic and peak regurgitant diastolic regional WSS and FD at the aortic root in BAV patients with regurgitation (BAV-REG) and BAV patients without or with trivial regurgitation (BAV-No/Trivial REG). Methods: To conduct this retrospective study, a total of 98 subjects (N=38 BAV-No/Trivial REG, age: 48±16 years, N=35 BAV-REG, age: 52±13 years, and N=25 healthy, age: 38±14 years) were recruited. All subjects underwent routine cardiac magnetic resonance imaging (MRI) followed by four-dimensional cardiovascular magnetic resonance flow imaging using a 3.0 Tesla MRI scanner. Regional peak systolic (WSSSys) and peak regurgitant diastolic (WSSDia) WSS as well as FD (FDSys, FDDia) at annulus, sinus of Valsalva, sinotubular junction, and mid ascending aorta planes were calculated by dividing the extracted two-dimensional planes into eight sectors. Patients were also followed for the occurrence of aortic valve surgery. Independent-samples Kruskal-Wallis H test (Bonferroni corrected at a 0.05 significance level), along with univariate and logistic regression analyses statistical tests were used. Results: BAV-REG had similar planar WSSSys patterns compared to BAV-No/Trivial REG. However, peak regurgitant planar WSSDia was significantly higher in BAV-REG compared to both healthy controls and BAV-No/Trivial REG at the annulus and sinus of Valsalva planes (P<0.05) in specific left-sided octants. Normalized peak regurgitant FDDia was significantly higher only in BAV-REG compared to healthy controls (P=0.03). WSSDia showed a significant association with the regurgitation severities at the annulus (ρ=0.34, P<0.001), sinus of Valsalva (ρ=0.34, P<0.001), sinotubular junction (ρ=0.48, P<0.001) planes. Furthermore, logistic regression analysis highlighted the potential role of peak regurgitant WSSDia in the likelihood of requiring surgery (β=5.49, P=0.009). Conclusions: Higher WSSDia in BAV patients, particularly in BAV-REG, and the significant association between WSSDia and regurgitation severity underscore its potential pathophysiological role in aortic root dilation.