Association of Regional Wall Shear Stress and Progressive Ascending Aorta 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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Contributing Factor of Proximal Arch Dilation in Patients with Bicuspid Aortic Valve—Wall Shear Stress or Upward Extension of Ascending Aorta Dilation?

The Heart Surgery Forum ◽

10.1532/hsf.2925 ◽

2020 ◽

Vol 23 (4) ◽

pp. E435-E440

Author(s):

Fei Li ◽

Qi Gao ◽

En Qiao ◽

Gang Yin ◽

Ru-Jiao Zhang ◽

...

Keyword(s):

Shear Stress ◽

Aortic Valve ◽

Wall Shear Stress ◽

Bicuspid Aortic Valve ◽

Ascending Aorta ◽

Aortic Diameter ◽

Selective Approach ◽

Significant Difference ◽

Wall Shear ◽

The One

Purpose: The dilation of proximal arch (PArc) was suspected to develop as a result of valve-related hemodynamics or in consequence to the upward extension of the ascending aorta (AAo) dilation. We aimed to investigate the one that could be the possible contributing factor in patients with bicuspid aortic valve (BAV). Methods: All enrolled BAV patients underwent four-dimensional flow magnetic resonance imaging. Contour-averaged circumferential wall shear stress (WSScirc,avg) and the diameter of the middle of AAo (mid-AAo) were compared between the patients with and without PArc dilation. Additionally, we analyzed the correlation between WSScirc,avg and aortic diameter at PArc section, as well as the correlation between the diameter of mid-AAo and that of PArc. Results: No significant difference was observed in WSScirc,avg at PArc section between the patients with and without PArc dilation (P = .621). However, the diameter of mid-AAo in the patients who suffered PArc dilation was higher than those without it (P = .007). In addition, the aortic diameter did not correlate with the WSScirc,avg at PArc level (R = -0.068, P = .701). The correlation was observed between PArc diameter and mid-AAo diameter (R = 0.521, P = .002). Conclusion: Hemodynamics may not contribute to the development of PArc dilation. PArc diameter correlated with mid-AAo diameter, indicating PArc dilation may be secondary to the upward extension of AAo dilation. The influence of AAo dilation extending upward could be treated by AAo replacement; hence, a selective approach to transverse PArc replacement might be appropriate.

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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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Left Main Stenosis Stenting Normalises Wall Shear Stress of Ascending Aorta in Bicuspid Aortic Valve

Heart International ◽

10.17925/hi.2020.14.2.121 ◽

2020 ◽

Vol 14 (2) ◽

pp. 121

Author(s):

Gianluca Rigatelli ◽

Marco Zuin ◽

◽

Keyword(s):

Shear Stress ◽

Aortic Valve ◽

Wall Shear Stress ◽

Bicuspid Aortic Valve ◽

Ascending Aorta ◽

Left Main ◽

Left Main Stenosis ◽

Wall Shear

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Circumferential wall shear stress predicts co-localized progressive dilation in bicuspid aortic valve patients

European Heart Journal ◽

10.1093/eurheartj/ehab724.1978 ◽

2021 ◽

Vol 42 (Supplement_1) ◽

Author(s):

A Guala ◽

L Dux-Santoy ◽

G Teixido-Tura ◽

A Ruiz-Munoz ◽

K M Johnson ◽

...

Keyword(s):

Growth Rate ◽

Shear Stress ◽

Aortic Valve ◽

Wall Shear Stress ◽

Bicuspid Aortic Valve ◽

Outer Region ◽

Ascending Aorta ◽

Axial Component ◽

Wall Shear

Abstract Background Bicuspid aortic valve (BAV), a congenital heart defect, is associated with ascending aorta (AAo) dilation. Whether the high prevalence of dilation in BAV patients is related to alteration of aortic blood flow and thus in wall shear stress (WSS) [1,2], which have been associated with aortic wall degeneration [3], or intrinsic abnormalities of the aortic wall, such as altered aortic stiffness [4], has not been established. Recently, a technique for the semi-automatic quantification of progressive aortic dilation maps via image registration has been introduced [5]. Purpose To test whether ascending aorta WSS predicts co-localized progressive dilation in BAV patients. Methods Forty BAV patients free from moderate and severe aortic valve regurgitation (regurgitant fraction <16%) and stenosis (maximum velocity at the aortic valve <3m/s), with no previous aortic or aortic valve surgery or replacement and included in a double-blind clinical trial (BICATOR, NCT02679261) were enrolled. All patients underwent a baseline 4D flow CMR study to assess aortic hemodynamics, followed by two contrast-enhanced computed tomography angiographies to quantify progressive dilation. WSS was computed at 64 pre-specified standardized ascending aortic regions, automatically obtained dividing the ascending aorta into 8 equidistant longitudinal sections which were further divided along the circumference into 8 equal regions (I = inner, L = left, O = outer and R = right) [2]. WSS was also projected into axial and circumferential directions, as previously described [1,2]. Progressive dilation was assessed in terms of growth rate (GR), i.e. increase in diameter divided by follow-up duration [mm/year], following a previously described methodology [5], at the same 64 pre-specified ascending aortic locations. A two-tailed p-value <0.05 was considered statistically significant. Results Demographic and clinical characteristics of the patients are shown in Table 1. WSS and growth rate maps are shown in Figure 1. Follow-up duration was 44.8±2.6 months. Growth rate (Figure 1A) was heterogeneously distributed, being highest (up to 0.26 mm/year) in the outer region of the mid AAo and in the inner region of the proximal-mid AAo. Circumferential WSS showed highest values in the outer region of the mid AAo (Figure 1C) while WSS (magnitude) and its axial component (Figure 1B and D) presented maximum values in the right region of the mid AAo. Maps of statistically significant association between GR and WSS values showed circumferential WSS to be correlated with GR in regions where progressive dilation was fastest, while WSS magnitude and its axial component resulted in limited associations with GR maps. Conclusions Circumferential wall shear stress predicts location-matched progressive dilation in bicuspid aortic valve patients. FUNDunding Acknowledgement Type of funding sources: Public grant(s) – National budget only. Main funding source(s): This study has received funding from the Instituto de Salud Carlos III (PI17/00381). Guala A. has received funding from Spanish Ministry of Science, Innovation and Universities (IJC2018-037349-I). Table 1. Demographics Figure 1. GR and WSS maps and correlations

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