Low and Oscillatory Wall Shear Stress Is Not Related to Aortic Dilation in Patients With Bicuspid Aortic Valve

Abstract

Objective: To assess the relationship between regional wall shear stress (WSS) and oscillatory shear index (OSI) and aortic dilation in patients with bicuspid aortic valve (BAV). Approach and Results: Forty-six consecutive patients with BAV (63% with right-left-coronary-cusp fusion, aortic diameter ≤ 45 mm and no severe valvular disease) and 44 healthy volunteers were studied by time-resolved 3-dimensional phase-contrast magnetic resonance imaging. WSS and OSI were quantified at different levels of the ascending aorta and the aortic arch, and regional WSS and OSI maps were obtained. Seventy percent of BAV had ascending aorta dilation. Compared with healthy volunteers, patients with BAV had increased WSS and decreased OSI in most of the ascending aorta and the aortic arch. In both BAV and healthy volunteers, regions of high WSS matched regions of low OSI and vice versa. No regions of both low WSS and high OSI were identified in BAV compared with healthy volunteers. Patients with BAV with dilated compared with nondilated aorta presented low and oscillatory WSS in the aortic arch, but not in the ascending aorta where dilation is more prevalent. Furthermore, no regions of concomitant low WSS and high OSI were identified when BAV were compared according to leaflet fusion pattern, despite the well-known differences in regional dilation prevalence. Conclusions: Regions with low WSS and high OSI do not match those with the highest prevalence of dilation in patients with BAV, thus providing no evidence to support the low and oscillatory shear stress theory in the pathogenesis of proximal aorta dilation in the presence of BAV.

Changes in aorta hemodynamics in Left-Right Type 1 bicuspid aortic valve patients after replacement with bioprosthetic valves: An in-silico study

“…The results presented herein confirm the findings of Dux-Santoy et al[ 26 ] suggesting that hemodynamics resulting due to BAV are not associated with low and oscillating TAWSS in the AAo (Figs 10 and 14 ); on the contrary, strong and unidirectional, eccentric aortic jets lead to high TAWSS/ low OSI on large parts of the AAo wall. Fig 17 shows that high OSI regions generally matched with those experiencing low TAWSS, but these regions, on average, made up less than 20% of the AAo surface area with BAVs ( Fig 18 ).…”

“…Focused investigations into the association between BAV aortopathy and the underlying blood flow appear to suggest that the hemodynamic determinants of aortic diameter modifications might follow a different mechanism. A recent study by Dux-Santoy et al [ 26 ] compared WSS on the AAo in 46 BAV patients to 44 healthy volunteers using time-resolved 3D MRI and found that regions exposed to low and oscillating wall shear stress in BAV patients did not match those with the highest prevalence of dilation. In other studies, the group also showed, through cardiac MRI analysis and in silico modeling that BAV patients exhibited strong helical flows in the aorta, with increased axial circulation [ 27 ] and circumferential wall shear stress [ 28 ] compared to healthy controls.…”

Fluid–structure interaction simulations outperform computational fluid dynamics in the description of thoracic aorta haemodynamics and in the differentiation of progressive dilation in Marfan syndrome patients

“…However, there are serious limitations in both spatial and temporal resolution of the signals and data are corrupted by noise-like phase error [17]. Recently, multiple studies have used 4D flow MRI for the assessment of haemodynamics of the aorta evaluating aortic flow patterns, WSS and regional aortic stiffness (via pulse wave velocity (PWV) in the thoracic aorta of bicuspid aortic valve [8,[18][19][20] and MFS [21,22] patients). Outlet boundary conditions can be simulated using the Windkessel model.…”

Fully Three-Dimensional Hemodynamic Characterization of Altered Blood Flow in Bicuspid Aortic Valve Patients With Respect to Aortic Dilatation: A Finite Element Approach

“…Wall shear stress has also been extensively studied in patients with BAV ( 6 , 9 , 15 – 17 , 21 , 39 , 42 , 43 ). In this study, we found statistically significant differences for the magnitude of WSS between HV and patients with BAV with AAo dilated and all patients together.…”