Assessment of abnormal transvalvular flow and wall shear stress direction for pediatric/young adults with bicuspid aortic valve: A cross-sectional four-dimensional flow study.

Aortic dilation is seen in pediatric/young adult patients with bicuspid aortic valve (BAV), and hemodynamic markers to predict aortic dilation are necessary for monitoring. Although promising hemodynamic metrics, such as abnormal wall shear stress (WSS) magnitude, have been proposed for adult BAV patients using four-dimensional (4D) flow cardiovascular magnetic resonance, those for pediatric BAV patients have less frequently been reported, partly due to scarcity of data to define normal WSS range. To circumvent this challenge, this study aims to investigate if a recently proposed 4D flow-based hemodynamic measurement, abnormal flow directionality, is associated with aortic dilation in pediatric/young adult BAV patients. 4D flow scans for BAV patients (<20 years old) and age-matched controls were retrospectively enrolled. Static segmentation for the aorta and pulmonary arteries was obtained to quantify peak systolic hemodynamics and diameters in the proximal aorta. In addition to peak velocity, WSS, vorticity, helicity, and viscous energy loss, direction of aortic velocity and WSS in BAV patients were compared with that of control atlas using registration technique; angle differences of >60 deg and >120 deg were defined as moderately and severely abnormal, respectively. The association between the obtained metrics and normalized diameters (Z-scores) was evaluated at the sinotubular junction, mid-ascending aorta, and distal ascending aorta. Fifty-three BAV patients, including 18 with history of repaired aortic coarctation, and 17 controls were enrolled. Correlation between moderately abnormal velocity/WSS direction and aortic Z-scores was moderate to strong at the sinotubular junction and mid-ascending aorta (R = 0.62-0.81; p < 0.001) while conventional measurements exhibited weaker correlation (|R| = 0.003-0.47, p = 0.009-0.99) in all subdomains. Multivariable regression analysis found moderately abnormal velocity direction and existence of aortic regurgitation (only for isolated BAV group) were independently associated with mid-ascending aortic Z-scores. Abnormal velocity and WSS directionality in the proximal aorta were strongly associated with aortic Z-scores in pediatric/young adult BAV patients.

Fujiwara T ，Malone LJ ，Chatfield KC ，Berthusen A ，Fonseca B ，Browne LP ，Barker AJ ... -  《-》

Regional aortic wall shear stress increases over time in patients with a bicuspid aortic valve.

Aortic wall shear stress (WSS) is a known predictor of ascending aortic growth in patients with a bicuspid aortic valve (BAV). The aim of this study was to study regional WSS and changes over time in BAV patients. BAV patients and age-matched healthy controls underwent four-dimensional (4D) flow cardiovascular magnetic resonance (CMR). Regional, peak systolic ascending aortic WSS, aortic valve function, aortic stiffness measures, and aortic dimensions were assessed. In BAV patients, 4D flow CMR was repeated after 3 years of follow-up and both at baseline and follow-up computed tomography angiography (CTA) were acquired. Aortic growth (volume increase of ≥5%) was measured on CTA. Regional WSS differences within patients' aorta and WSS changes over time were analyzed using linear mixed-effect models and were associated with clinical parameters. Thirty BAV patients (aged 34 years [interquartile range (IQR) 25-41]) were included in the follow-up analysis. Additionally, another 16 BAV patients and 32 healthy controls (aged 33 years [IQR 28-48]) were included for other regional analyses. Magnitude, axial, and circumferential WSS increased over time (all p < 0.001) irrespective of aortic growth. The percentage of regions exposed to a magnitude WSS >95th percentile of healthy controls increased from 21% (baseline 506/2400 regions) to 31% (follow-up 734/2400 regions) (p < 0.001). WSS angle, a measure of helicity near the aortic wall, decreased during follow-up. Magnitude WSS changes over time were associated with systolic blood pressure, peak aortic valve velocity, aortic valve regurgitation fraction, aortic stiffness indexes, and normalized flow displacement (all p < 0.05). An increase in regional WSS over time was observed in BAV patients, irrespective of aortic growth. The increasing WSSs, comprising a larger area of the aorta, warrant further research to investigate the possible predictive value for aortic dissection.

Minderhoud SCS ，Arrouby A ，van den Hoven AT ，Bons LR ，Chelu RG ，Kardys I ，Rizopoulos D ，Korteland SA ，van den Bosch AE ，Budde RPJ ，Roos-Hesselink JW ，Wentzel JJ ，Hirsch A ... -  《-》

Flow quantification within the aortic ejection tract using 4D flow cardiac MRI in patients with bicuspid aortic valve: Implications for the assessment of aortic regurgitation.

Nguyen LA ，Gencer U ，Goudot G ，Craiem D ，Casciaro ME ，Cheng C ，Messas E ，Mousseaux E ，Soulat G ... -  《Diagnostic and Interventional Imaging》

Blood flow dynamics in the ascending aorta of patients with bicuspid aortic valve before and after transcatheter aortic valve replacement: a computational fluid dynamics study.

Abnormal blood flow patterns are known to contribute to the ascending aortic dilation in patients with bicuspid aortic valve (BAV). The present study elucidated the blood flow characteristics in the dilated ascending aorta before and after transcatheter aortic valve replacement (TAVR) using computational fluid dynamics (CFD) analysis. We performed CFD analysis in three BAV patients with ascending aortic dilation (maximum diameter ≥ 45 mm) who underwent TAVR. The blood flow streamline was visualized to evaluate the pre- and post-operative flow velocity, severity of vortex and helix, and wall shear stress (WSS) in the ascending aorta. Before the procedure, all three patients showed abnormal blood flow patterns, with vortex and helix in the ascending aorta. Regionally elevated WSS was also observed in the lateral or posterior ascending aortic wall (16.7 Pa, 12.2 Pa, and 14.5 Pa in patient 1, 2, and 3, respectively). After the procedure, the blood flow patterns significantly improved, and the maximum WSS also decreased (4.2 Pa, 1.1 Pa, and 3.2 Pa in patient 1, 2, and 3, respectively). Abnormal blood flow patterns and WSS appeared to improve after TAVR in BAV patients with ascending aortic dilation. The impact on the long-term aortic growth rate and the incidence of aortic dissection requires further studies. Changes of Ascending Aortic Diameter in Patients Undergoing Transcatheter Aortic Valve Replacement. gov number NCT05739253. Trial registration date 20,230,212.

An K ，Zhang F ，Ouyang W ，Pan X ... -  《BMC Cardiovascular Disorders》

Comprehensive sex-specific and age-dependent analysis of four-dimensional flow cardiovascular magnetic resonance assessed aortic blood flow-related parameters in normal subjects using single-vendor magnetic resonance systems and single-vendor software.

Aortic blood flow characterization by four-dimensional (4D) flow cardiovascular magnetic resonance (CMR) is increasingly performed in aneurysm research. A limited number of studies have established normal values that can aid the recognition of abnormal flow at an early stage. This study aims to establish additional sex-specific and age-dependent reference values for flow-related parameters in a large cohort of healthy adults. Two hundred and twelve volunteers were included, and 191 volunteers completed the full study protocol. All underwent 4D flow CMR of the entire aorta. Quantitative values for velocity, vorticity, helicity, as well as total, circumferential, and axial wall shear stress (WSS) were determined for the aortic root (AoR), ascending aorta (AAo), aortic arch, descending aorta (DAo), suprarenal aorta, and infrarenal aorta. Vorticity and helicity were indexed for segment volume (mL). The normal values were estimated per sex and age group, where significant differences between males (M) and females (F) were found only for specific age groups. More specifically, the following variables were significantly different after applying the false discovery rate correction for multiple testing: 1) velocity in the AAo and DAo in the 60-70 years age group (mean ± SD: (M) 47.0 ± 8.2 cm s-1 vs (F) 38.4 ± 6.9 cm s-1, p = 0.001 and, (M) 55.9 ± 9.9 cm s-1 vs (F) 46.5 ± 5.5 cm s-1, p = 0.002), 2) normalized vorticity in AoR in the 50-59 years age group ((M) 27,539 ± 5042 s-1 mL-1 vs (F) 30,849 ± 7285 s-1 mL-1, p = 0.002), 3) axial WSS in the Aao in the 18-29 age group ((M) 1098 ± 203 mPa vs (F) 921 ± 121 mPa, p = 0.002). Good to strong negative correlations with age were seen for almost all variables, in different segments, and for both sexes. This study describes reference values for aortic flow-related parameters acquired by 4D flow MRI. We observed limited differences between males and females. A negative relationship with age was seen for almost all flow-related parameters and segments.

Ramaekers MJFG ，Te Kiefte BJC ，Adriaans BP ，Juffermans JF ，van Assen HC ，Winkens B ，Wildberger JE ，Lamb HJ ，Schalla S ，Westenberg JJM ... -  《-》