CMR 4D-Flow Wall Shear Stress and Aortic Dilation in Bicuspid Aortic Valve

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.

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Effect of Bicuspid Aortic Valve Cusp Fusion on Aorta Wall Shear Stress: Preliminary Computational Assessment and Implication for Aortic Dilation

World Journal of Cardiovascular Diseases ◽

10.4236/wjcd.2015.56016 ◽

2015 ◽

Vol 05 (06) ◽

pp. 129-140 ◽

Cited By ~ 13

Author(s):

Kai Cao ◽

Philippe Sucosky

Keyword(s):

Shear Stress ◽

Aortic Valve ◽

Wall Shear Stress ◽

Bicuspid Aortic Valve ◽

Aortic Dilation ◽

Aorta Wall ◽

Wall Shear

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Bicuspid aortic valve disease associates with abnormal wall shear stress, viscous energy loss, and pressure drop within the ascending thoracic aorta

European Heart Journal ◽

10.1093/ehjci/ehaa946.2335 ◽

2020 ◽

Vol 41 (Supplement_2) ◽

Author(s):

P Geeraert ◽

F Jamalidinan ◽

M Bristow ◽

C Lydell ◽

A.G Howarth ◽

...

Keyword(s):

Shear Stress ◽

Pressure Drop ◽

Aortic Valve ◽

Wall Shear Stress ◽

Energy Loss ◽

Bicuspid Aortic Valve ◽

Ascending Aorta ◽

Funding Source ◽

4D Flow ◽

Wall Shear

Abstract Introduction We use 4D Flow MRI to (1) investigate the effects of bicuspid aortic valve (BAV) disease on downstream pressure drop (PD), wall shear stress (WSS), and viscous energy loss (EL) in the ascending aorta (AAo) and (2) explore the associations between AAo diameter and PD, WSS, and EL. Hypothesis BAV patients show increased PD, WSS, and EL in the AAo compared to age-matched controls Methods 32 healthy controls (41±15 y, 10 female) and 53 BAV patients (44±16 y, 19 female) underwent cardiac MRI at 3T, inclusive of cine imaging and 4D flow. Cross sections were placed along segmented aortas at the: left ventricular outflow tract (LVOT), sinuses of Valsalva (SOV), mid-ascending aorta (MAA), and proximal to first aortic branch (AA1). Locations were analyzed for (i) net flow, (ii) aortic diameter (normalized to BSA), (iii) systolic PD (referenced to LVOT), (iv) systolic EL (measured within LVOT-AA1 volume and normalized by LVOT net flow; mW/mL), and (v) systolic WSS. Sub-vectors of WSS, axial (WSSax) and circumferential (WSScirc), were also analyzed. Results In comparison to controls, BAV patients showed greater PD (e.g. MAA: 9.5±8.0 vs. 2.8±2.4mmHg; p<0.01), EL (0.09±0.05 vs. 0.04±0.01 mW/mL; p≤0.01), and WSScirc (e.g. MAA: 0.3±0.1 vs. 0.2±0.06 Pa; p≤0.01) throughout the AAo (Table 1 and Fig. 1). BAV patients exhibited significantly lower WSS and WSSax only at the SOV. In univariate analyses, AAo diameter was inversely correlated with WSS (R=−0.32, p<0.01) and WSSax (R=−0.51, p≤0.01). In multivariate analyses, AAo diameter was associated with WSS (β=−0.36, p<0.01) and WSSax (β=−0.26, p<0.01). Conclusions BAV patients demonstrate significantly increased PD, EL, and WSScirc in the AAo, and an inverse association between AAo diameter and WSS measures. Funding Acknowledgement Type of funding source: Public Institution(s). Main funding source(s): Alberta Health Services

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