Bicuspid Aortic Valve Is Associated With Altered Wall Shear Stress in the Ascending Aorta

Abstract

Correspondence to Alex J. Barker, PhD, Department of Radiology, Northwestern University, 737 N Michigan Ave, Suite 1600, Chicago, IL 60611. E-mail alex.barker@northwestern.edu Background-Hemodynamics may play a role contributing to the progression of bicuspid aortic valve (BAV) aortopathy.This study measured the impact of BAV on the distribution of regional aortic wall shear stress (WSS) compared with control cohorts. Methods and Results-Local WSS distribution was measured in the thoracic aorta of 60 subjects using 4-dimensional (4D) flow-sensitive magnetic resonance imaging. WSS analysis included 15 BAV patients: 12 with fusion of the right-left coronary cusp (6 stenotic) and 3 with fusion of the right and noncoronary cusp. The right-left BAV cohort was compared with healthy subjects (n=15), age-appropriate subjects (n=15), and age-/aorta size-controlled subjects (n=15). Compared with the age-appropriate and age-/aorta size-matched controls, WSS patterns in the right-left BAV ascending aorta were significantly elevated, independent of stenosis severity (peak WSS=0.9±0.3 N/m 2 compared with 0.4±0.3 N/m 2 in age-/aorta size-controlled subjects; P<0.001). Time-resolved (cine) 2D images of the bicuspid valves were coregistered with 4D flow data, directly linking cusp fusion pattern to a distinct ascending aortic flow jet pattern. The observation of right-anterior ascending aorta wall/jet impingement in right-left BAV patients corresponded to regions with statistically elevated WSS. Alternative jetting patterns were observed in the right and noncoronary cusp fusion patients. Conclusions-The results of this study demonstrate that bicuspid valves induced significantly altered ascending aorta hemodynamics compared with age-and size-matched controls with tricuspid valves. Specifically, the expression of increased and asymmetric WSS at the aorta wall was related to ascending aortic flow jet patterns, which were influenced by the BAV fusion pattern. (Circ Cardiovasc Imaging. 2012;5:457-466.)

Aortic Valve Stenosis Alters Expression of Regional Aortic Wall Shear Stress: New Insights From a 4‐Dimensional Flow Magnetic Resonance Imaging Study of 571 Subjects

“…A previous study from our group found that AS did not elevate WSS in a small pilot cohort of BAV patients (of n=15, only 8 had AS) 6. Contrary to the previous findings, this study found marked, significant increases of aortic 3D WSS in the presence of AS for both TAV‐TAA and BAV groups (Figure 3; Table 2).…”

“…Findings demonstrate that aortic dilatation with an otherwise normal aortic valve (TAV) generally leads to deranged (helical) slow flow with significantly lower WSS in the ascending aorta 10. In contrast, BAV or AS will result in significantly elevated flow velocities, localized outflow jet patterns, and eccentrically elevated WSS 6, 7. These observations indicate that aortic valve disease and aortic dilatation represent different manifestation of aortic pathologies that may lead to similar patient outcome (aneurysm, dissection), but are associated with substantially differing hemodynamics and WSS.…”

“…Genetic variants may contribute to BAV mediated aortopathy, but no common or unifying genetic pattern has emerged. The consistent observation of BAV‐mediated alterations in ascending aortic blood flow patterns, even without clinically relevant valve dysfunction,6, 7 has formed the basis for a hemodynamic hypothesis which postulates that regional BAV aortopathy is attributed to the impact of these altered blood flow patterns on vessel wall remodeling 2, 8, 9…”

Erratum to: Quantitative Assessment of Turbulence and Flow Eccentricity in an Aortic Coarctation: Impact of Virtual Interventions

“…41 Also outflow jet eccentricity has been associated with the aortic dilation and aneurysm formation, e.g., patients with bicuspid aortic valve (BAV) disease where significant flow displacement and jet-towall impingement could be observed compared to the general population. 3,14,17,50 Coarctation of the aorta (CoA) is a congenital cardiovascular malformation characterized by an iso-lated narrowing of the vessel lumen accompanied with jet-like and turbulent flow characteristics, leading to upper-body hypertension as a result of the increased trans-stenotic pressure drop. Despite recent advancement in intervention procedures, premature reduced life expectancy is frequently observed and linked to long-term cardiovascular complications.…”

“…2,32 Furthermore, elevated turbulence has shown to induce abnormal WSS 18,19,33 and increase local flow strain-rates significantly. 18 Also eccentric flows have been related to increased growth rate of aortic dilations, 25 elevated and complex WSS patterns at the vicinity of jet-impingement, 3,17,55 favor turbulence production 28,53 and produce large zones of vortex formation and flow recirculation, regions known to promote platelet thrombus formation. 26 While non-invasive assessment of TKE and eccentric flow has led to several interesting findings, they have not been used extensively in CFD studies of CoAs.…”