Aortic valve stenosis and aortic diameters determine the extent of increased wall shear stress in bicuspid aortic valve disease

Abstract

BackgroundUse of 4‐dimensional flow magnetic resonance imaging (4D‐flow MRI) derived wall shear stress (WSS) heat maps enables identification of regions in the ascending aorta with increased WSS. These regions are subject to dysregulation of the extracellular matrix and elastic fiber degeneration, which is associated with aortic dilatation and dissection.PurposeTo evaluate the effect of the presence of aortic valve stenosis and the aortic diameter on the peak WSS and surface area of increased WSS in the ascending aorta.Study TypeProspective.SubjectsIn all, 48 bicuspid aortic valve (BAV) patients (38.1 ± 12.4 years) and 25 age‐ and gender‐matched healthy individuals.Field Strength/SequenceTime‐resolved 3D phase contrast MRI with three‐directional velocity encoding at 3.0T.AssessmentPeak systolic velocity, WSS, and aortic diameters were assessed in the ascending aorta and 3D heat maps were used to identify regions with elevated WSS.Statistical TestsComparisons between groups were performed by t‐tests. Correlations were investigated by univariate and multivariate regression analysis.ResultsElevated WSS was present in 15 ± 11% (range; 1–35%) of the surface area of the ascending aorta of BAV patients with aortic valve stenosis (AS) (n = 10) and in 6 ± 8% (range; 0–31%) of the ascending aorta of BAV patients without AS (P = 0.005). The mid‐ascending aortic diameter negatively correlated with the peak ascending aortic WSS (R = –0.413, P = 0.004) and the surface area of elevated WSS (R = –0.419, P = 0.003). Multivariate linear regression analysis yielded that the height of peak WSS and the amount of elevated WSS depended individually on the presence of aortic valve stenosis and the diameter of the ascending aorta.Data ConclusionThe extent of increased WSS in the ascending aorta of BAV patients depends on the presence of aortic valve stenosis and aortic dilatation and is most pronounced in the presence of AS and a nondilated ascending aorta. Level of Evidence: 2 Technical Efficacy: Stage 2J. MAGN. RESON. IMAGING 2018;48:522–530.

Elevated diastolic wall shear stress in regurgitant semilunar valvular lesions

“…Elevated WSS in BAV has been previously reported . The presence of aortic stenosis was associated with a further increase in WSS .…”

“…In valvular heart disease, WSS has been extensively studied in bicuspid aortic valve (BAV), and was shown to correlate with pathological changes in the aorta . The presence of aortic stenosis was associated with further increases in WSS . However, the impact of aortic regurgitation (AR) on WSS is less clear .…”

Transcatheter aortic valve replacement alters ascending aortic blood flow and wall shear stress patterns: A 4D flow MRI comparison with age-matched, elderly controls

“…Cohort-averaged velocity and WSS three-dimensional (3D) 'heat maps' were created from the control group data, delineating elevated velocity and WSS in the aorta of TAVR patients [17,18]. A 'shared' geometry of the control group was created and each aorta was co-registered to this shared geometry, followed by interpolation of systolic velocity and WSS values.…”

“…Finally, the heat maps were projected on cohort-specific 'shared' geometries [19]. By addition of the heat maps, a 3D incidence map showing regional incidence of elevated velocity and WSS was created [18]. Aortic dimensions were calculated using a 3D surface mesh, delineating the aortic wall, which was created from the segmentation and smoothed with a Laplacian filter.…”

“…Aortic dimensions were calculated using a 3D surface mesh, delineating the aortic wall, which was created from the segmentation and smoothed with a Laplacian filter. Normal vectors were calculated on each point on the wall and used for: (1) 3D WSS calculation as previously described [17] and (2) 3D diameter calculation by tracking the length of the inward normal upon exiting the opposite aortic wall [18].…”