Dataset Information

Aortic flow patterns and wall shear stress maps by 4D-flow cardiovascular magnetic resonance in the assessment of aortic dilatation in bicuspid aortic valve disease.

ABSTRACT:

Background

In patients with bicuspid valve (BAV), ascending aorta (AAo) dilatation may be caused by altered flow patterns and wall shear stress (WSS). These differences may explain different aortic dilatation morphotypes. Using 4D-flow cardiovascular magnetic resonance (CMR), we aimed to analyze differences in flow patterns and regional axial and circumferential WSS maps between BAV phenotypes and their correlation with ascending aorta dilatation morphotype.

Methods

One hundred and one BAV patients (aortic diameter???45 mm, no severe valvular disease) and 20 healthy subjects were studied by 4D-flow CMR. Peak velocity, flow jet angle, flow displacement, in-plane rotational flow (IRF) and systolic flow reversal ratio (SFRR) were assessed at different levels of the AAo. Peak-systolic axial and circumferential regional WSS maps were also estimated. Unadjusted and multivariable adjusted linear regression analyses were used to identify independent correlates of aortic root or ascending dilatation. Age, sex, valve morphotype, body surface area, flow derived variables and WSS components were included in the multivariable models.

Results

The AAo was non-dilated in 24 BAV patients and dilated in 77 (root morphotype in 11 and ascending in 66). BAV phenotype was right-left (RL-) in 78 patients and right-non-coronary (RN-) in 23. Both BAV phenotypes presented different outflow jet direction and velocity profiles that matched the location of maximum systolic axial WSS. RL-BAV velocity profiles and maximum axial WSS were homogeneously distributed right-anteriorly, however, RN-BAV showed higher variable profiles with a main proximal-posterior distribution shifting anteriorly at mid-distal AAo. Compared to controls, BAV patients presented similar WSS magnitude at proximal, mid and distal AAo (p?=?0.764, 0.516 and 0.053, respectively) but lower axial and higher circumferential WSS components (p?ConclusionsDifferent BAV-phenotypes present different flow patterns with an anterior distribution in RL-BAV, whereas, RN-BAV patients present a predominant posterior outflow jet at the sinotubular junction that shifts to anterior or right anterior in mid and distal AAo. Thus, RL-BAV patients present a higher axial WSS at the aortic root while RN-BAV present a higher circumferential WSS in mid and distal AAo. These results may explain different AAo dilatation morphotypes in the BAV population.

SUBMITTER: Rodriguez-Palomares JF

PROVIDER: S-EPMC5918697 | biostudies-literature | 2018 Apr

REPOSITORIES: biostudies-literature

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Publications

Aortic flow patterns and wall shear stress maps by 4D-flow cardiovascular magnetic resonance in the assessment of aortic dilatation in bicuspid aortic valve disease.

Rodríguez-Palomares José Fernando JF Dux-Santoy Lydia L Guala Andrea A Kale Raquel R Maldonado Giuliana G Teixidó-Turà Gisela G Galian Laura L Huguet Marina M Valente Filipa F Gutiérrez Laura L González-Alujas Teresa T Johnson Kevin M KM Wieben Oliver O García-Dorado David D Evangelista Arturo A

Journal of cardiovascular magnetic resonance : official journal of the Society for Cardiovascular Magnetic Resonance 20180426 1

<h4>Background</h4>In patients with bicuspid valve (BAV), ascending aorta (AAo) dilatation may be caused by altered flow patterns and wall shear stress (WSS). These differences may explain different aortic dilatation morphotypes. Using 4D-flow cardiovascular magnetic resonance (CMR), we aimed to analyze differences in flow patterns and regional axial and circumferential WSS maps between BAV phenotypes and their correlation with ascending aorta dilatation morphotype.<h4>Methods</h4>One hundred an ...[more]

PMID: 29695249

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Project description:OBJECTIVES:The objectives of this study were to investigate an association between the magnitude of flow-mediated aortic wall shear stress (WSS) and medial wall histopathology in patients with bicuspid aortic valve (BAV) with aortopathy. METHODS:Patients with BAV (n = 27; 52 ± 15 years; 3 women; proximal thoracic aorta diameter = 4.4 ± 0.7 and 4.6 ± 0.5 cm) who underwent prophylactic aortic resection received preoperative 3-dimensional time-resolved phase-contrast magnetic resonance imaging with 3-dimensional velocity encoding to quantify WSS relative to a population of healthy age- and sex-matched tricuspid aortic valve control participants (n = 20). Quantitative histopathology was conducted on BAV aorta tissue samples resected at surgery (n = 93), and correlation was performed between elastic fiber thickness and in vivo aortic WSS as continuous variables. Validation of elastic fiber thickness was achieved by correlation relative to tissue stiffness determined using biaxial biomechanical testing (n = 22 samples). RESULTS:Elastic fibers were thinner and WSS was higher along the greater curvature compared with other circumferential regions (vs anterior wall: P = .003 and P = .0001, respectively; lesser curvature: both P = .001). Increased regional WSS was associated with decreased elastic fiber thickness (r = -0.25; P = .02). Patient stratification with subanalysis showed an increase in the correlation between WSS and histopathology with aortic valve stenosis (r = -0.36; P = .002) and smaller aortic diameters (<4.5 cm: r = -0.39; P = .03). Elastic fiber thinning was associated with circumferential stiffness (r = -0.41; P = .06). CONCLUSIONS:For patients with BAV, increased aortic valve-mediated WSS is significantly associated with elastic fiber thinning, particularly with aortic valve stenosis and in earlier stages of aortopathy. Elastic fiber thinning correlates with impaired tissue biomechanics. These novel findings further implicate valve-mediated hemodynamics in the progression of BAV aortopathy.

Project description:OBJECTIVES:Bicuspid aortic valve, characterized by valve malformation and risk for aortopathy, displays profound alteration in systolic aortic outflow and wall shear stress distribution. The present study performed 4-dimensional flow magnetic resonance imaging in patients with bicuspid aortic valve with right-left cusp fusion, focusing on the impact of valve function on hemodynamic status within the ascending aorta. METHODS:Four-dimensional flow magnetic resonance imaging was performed in 50 subjects with right-left bicuspid aortic valve and 15 age- and aortic size-matched controls with tricuspid aortic valve. Patients with bicuspid aortic valve were categorized into 3 groups according to their aortic valve function as follows: bicuspid aortic valve with no more than mild aortic valve dysfunction (bicuspid aortic valve control, n = 20), bicuspid aortic valve with severe aortic insufficiency (n = 15), and bicuspid aortic valve with severe aortic stenosis (n = 15). RESULTS:All patients with right-left bicuspid aortic valve exhibited peak wall shear stress at the right-anterior position of the ascending aorta (bicuspid aortic valve vs trileaflet aortic valve at the right-anterior position: 0.91 ± 0.23 N/m2 vs 0.43 ± 0.12 N/m2, P < .001) with no distinct alteration between bicuspid aortic valve with severe aortic insufficiency and bicuspid aortic valve with severe aortic stenosis. The predominance of dilatation involving the tubular ascending aorta (82%, type 2 aortopathy) persisted, with or without valve dysfunction. Compared with bicuspid aortic valve control subjects, the bicuspid aortic valve with severe aortic insufficiency group displayed universally elevated wall shear stress (0.75 ± 0.12 N/m2 vs 0.57 ± 0.09 N/m2, P < .01) in the ascending aorta, which was associated with elevated cardiac stroke volume (P < .05). The bicuspid aortic valve with severe aortic stenosis group showed elevated flow eccentricity in the form of significantly increased standard deviation of circumferential wall shear stress, which correlated with markedly increased peak aortic valve velocity (P < .01). CONCLUSIONS:The location of peak aortic wall shear stress and type of aortopathy remained homogeneous among patients with right-left bicuspid aortic valve irrespective of valve dysfunction. Severe aortic insufficiency or stenosis resulted in further elevated aortic wall shear stress and exaggerated flow eccentricity.

Project description:Background and purposePrognostic models based on cardiovascular hemodynamic parameters may bring new information for an early assessment of patients with bicuspid aortic valve (BAV), playing a key role in reducing the long-term risk of cardiovascular events. This work quantifies several three-dimensional hemodynamic parameters in different patients with BAV and ranks their relationships with aortic diameter.Materials and methodsUsing 4D-flow CMR data of 74 patients with BAV (49 right-left and 25 right-non-coronary) and 48 healthy volunteers, aortic 3D maps of seventeen 17 different hemodynamic parameters were quantified along the thoracic aorta. Patients with BAV were divided into two morphotype categories, BAV-Non-AAoD (where we include 18 non-dilated patients and 7 root-dilated patients) and BAV-AAoD (where we include the 49 patients with dilatation of the ascending aorta). Differences between volunteers and patients were evaluated using MANOVA with Pillai's trace statistic, Mann-Whitney U test, ROC curves, and minimum redundancy maximum relevance algorithm. Spearman's correlation was used to correlate the dilation with each hemodynamic parameter.ResultsThe flow eccentricity, backward velocity, velocity angle, regurgitation fraction, circumferential wall shear stress, axial vorticity, and axial circulation allowed to discriminate between volunteers and patients with BAV, even in the absence of dilation. In patients with BAV, the diameter presented a strong correlation (> |+/-0.7|) with the forward velocity and velocity angle, and a good correlation (> |+/-0.5|) with regurgitation fraction, wall shear stress, wall shear stress axial, and vorticity, also for morphotypes and phenotypes, some of them are correlated with the diameter. The velocity angle proved to be an excellent biomarker in the differentiation between volunteers and patients with BAV, BAV morphotypes, and BAV phenotypes, with an area under the curve bigger than 0.90, and higher predictor important scores.ConclusionsThrough the application of a novel 3D quantification method, hemodynamic parameters related to flow direction, such as flow eccentricity, velocity angle, and regurgitation fraction, presented the best relationships with a local diameter and effectively differentiated patients with BAV from healthy volunteers.

Project description:ObjectiveGuidelines for repair of bicuspid aortic valve-associated ascending thoracic aortic aneurysms have been changing, most recently to the same criteria as tricuspid aortic valve-ascending thoracic aortic aneurysms. Rupture/dissection occurs when wall stress exceeds wall strength. Recent studies suggest similar strength of bicuspid aortic valve versus tricuspid aortic valve-ascending thoracic aortic aneurysms; thus, comparative wall stress may better predict dissection in bicuspid aortic valve versus tricuspid aortic valve-ascending thoracic aortic aneurysms. Our aim was to determine whether bicuspid aortic valve-ascending thoracic aortic aneurysms had higher wall stresses than their tricuspid aortic valve counterparts.MethodsPatients with bicuspid aortic valve- and tricuspid aortic valve-ascending thoracic aortic aneurysms (bicuspid aortic valve = 17, tricuspid aortic valve = 19) greater than 4.5 cm underwent electrocardiogram-gated computed tomography angiography. Patient-specific 3-dimensional geometry was reconstructed and loaded to systemic pressure after accounting for prestress geometry. Finite element analyses were performed using the LS-DYNA solver (LSTC Inc, Livermore, Calif) with user-defined fiber-embedded material model to determine ascending thoracic aortic aneurysm wall stress.ResultsBicuspid aortic valve-ascending thoracic aortic aneurysms 99th-percentile longitudinal stresses were 280 kPa versus 242 kPa (P = .028) for tricuspid aortic valve-ascending thoracic aortic aneurysms in systole. These stresses did not correlate to diameter for bicuspid aortic valve-ascending thoracic aortic aneurysms (r = -0.004) but had better correlation to tricuspid aortic valve-ascending thoracic aortic aneurysms diameter (r = 0.677). Longitudinal stresses on sinotubular junction were significantly higher in bicuspid aortic valve-ascending thoracic aortic aneurysms than in tricuspid aortic valve-ascending thoracic aortic aneurysms (405 vs 329 kPa, P = .023). Bicuspid aortic valve-ascending thoracic aortic aneurysm 99th-percentile circumferential stresses were 548 kPa versus 462 kPa (P = .033) for tricuspid aortic valve-ascending thoracic aortic aneurysms, which also did not correlate to bicuspid aortic valve-ascending thoracic aortic aneurysm diameter (r = 0.007).ConclusionsCircumferential and longitudinal stresses were greater in bicuspid aortic valve- than tricuspid aortic valve-ascending thoracic aortic aneurysms and were more pronounced in the sinotubular junction. Peak wall stress did not correlate with bicuspid aortic valve-ascending thoracic aortic aneurysm diameter, suggesting diameter alone in this population may be a poor predictor of dissection risk. Our results highlight the need for patient-specific aneurysm wall stress analysis for accurate dissection risk prediction.

Dataset Information

Aortic flow patterns and wall shear stress maps by 4D-flow cardiovascular magnetic resonance in the assessment of aortic dilatation in bicuspid aortic valve disease.

Background

Methods

Results

Publications

Aortic flow patterns and wall shear stress maps by 4D-flow cardiovascular magnetic resonance in the assessment of aortic dilatation in bicuspid aortic valve disease.

Similar Datasets

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