Aortic shear stress in patients with bicuspid aortic valve with stenosis and insufficiency

Abstract

Objectives Bicuspid aortic valve (BAV), characterized by valve malformation and risk for aortopathy, displays profound alteration in systolic aortic outflow and wall shear stress (WSS) distribution. The present study performed 4-dimenstional flow MRI in BAV patients with right-left (R-L) cusp fusion, focusing on the impact of valve function upon hemodynamic status within ascending aorta. Methods Four-dimensional flow MRI was performed in 50 R-L BAV subjects and 15 age- and aortic size-matched controls with tricuspid aortic valve. BAV patients were categorized into 3 groups according to their aortic valve function as follows: BAV with no more than mild aortic valve dysfunction (BAV-CTL, n=20), BAV with severe aortic insufficiency (BAV-AI, n=15), and BAV with severe aortic stenosis (BAV-AS, n=15). Results All R-L BAV patients exhibited peak WSS at the right-anterior position of the ascending aorta (BAV vs. TAV at right-anterior position: 0.91±0.23 N/m2 vs. 0.43±0.12 N/m2, p<0.001) with no distinct alteration between BAV-AI and BAV-AS. The predominance of dilatation involving the tubular ascending aorta (82%, type 2 aortopathy) persisted, with or without valve dysfunction. Compared to BAV-CTL subjects, the BAV-AI group displayed universally elevated WSS (0.75±0.12 N/m2 vs. 0.57±0.09 N/m2, p<0.01) in the ascending aorta, which was associated with elevated cardiac stroke volume (p<0.05). The BAV-AS group showed elevated flow eccentricity in the form of significantly increased standard deviation of circumferential WSS, which correlated with markedly increased peak aortic valve velocity (p<0.01). Conclusions The location of peak aortic WSS and type of aortopathy remained homogeneous among R-L BAV patients irrespective of valve dysfunction. Severe aortic insufficiency or stenosis resulted in further elevated aortic WSS and exaggerated flow eccentricity.

Elevated diastolic wall shear stress in regurgitant semilunar valvular lesions

“…The presence of aortic stenosis was associated with a further increase in WSS . Data regarding the particular effect of AR appear conflicting . Our findings of increased WSS in AR are in accord with the study by Shan et al that showed systolic WSS to be elevated in the AR subgroup of 15 BAV patients.…”

“…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 .…”

“…The presence of aortic stenosis was associated with further increases in WSS . However, the impact of aortic regurgitation (AR) on WSS is less clear . It is important to note that these studies commented only on systolic WSS, while diastolic WSS was not described.…”

“…[5][6][7][8] The development of 4D flow cardiovascular magnetic resonance imaging (MRI), with velocity-encoding in all three spatial directions, as well as in relation to time, has enabled detailed study of normal and abnormal flow conditions, as well as allowing the study of advanced hemodynamic parameters including WSS. 9 In valvular heart disease, WSS has been extensively studied in bicuspid aortic valve (BAV), [10][11][12][13][14][15][16][17][18][19][20][21] and was shown to correlate with pathological changes in the aorta. 16 The presence of aortic stenosis was associated with further increases in WSS.…”