Abstract：
BACKGROUND: 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.
METHODS: BAV patients and age-matched healthy controls underwent 4D flow 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 three years follow-up and both at baseline and follow-up computed tomography angiography (CTA) was acquired. Aortic growth (volume increase of ≥5%) was measured on CTA. Regional WSS differences within patients\' aorta and WSS changes over time were analysed using linear mixed-effect models and were associated with clinical parameters.
RESULTS: Thirty BAV patients (aged 34 years [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).
CONCLUSIONS: An increase of regional WSS over time was observed in BAV patients, irrespective of aortic growth. The increasing WSSs comprising a larger area of the aorta warrants further research to investigate the possible predictive value for aortic dissection.
METHODS: BAV patients and age-matched healthy controls underwent 4D flow 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 three years follow-up and both at baseline and follow-up computed tomography angiography (CTA) was acquired. Aortic growth (volume increase of ≥5%) was measured on CTA. Regional WSS differences within patients\' aorta and WSS changes over time were analysed using linear mixed-effect models and were associated with clinical parameters.
RESULTS: Thirty BAV patients (aged 34 years [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).
CONCLUSIONS: An increase of regional WSS over time was observed in BAV patients, irrespective of aortic growth. The increasing WSSs comprising a larger area of the aorta warrants further research to investigate the possible predictive value for aortic dissection.
摘要：
背景：主动脉壁切应力（WSS）是二叶主动脉瓣（BAV）患者升主动脉生长的已知预测指标。这项研究的目的是研究BAV患者的区域性WSS和随时间的变化。
方法：BAV患者和年龄匹配的健康对照者接受4D流量CMR。区域,收缩期升主动脉WSS峰值，主动脉瓣功能,评估主动脉硬度测量值和主动脉尺寸.在BAV患者中，随访三年后重复进行4D流CMR，并在基线和随访时获得计算机断层扫描血管造影（CTA）。在CTA上测量主动脉生长(体积增加≥5%)。使用线性混合效应模型分析患者主动脉内的局部WSS差异和随时间的WSS变化，并与临床参数相关。
结果：30例BAV患者（年龄34岁[IQR25-41]）纳入随访分析。此外,另外16例BAV患者和32例健康对照(年龄33岁[IQR28~48])被纳入其他区域分析.幅度,轴向，与主动脉生长无关，周向WSS随时间增加（所有p<0.001）。暴露于幅度WSS>95百分位数的健康对照的区域的百分比从21%(基线506/2400区域)增加至31%(随访734/2400区域)(p<0.001)。WSS角度,测量主动脉壁附近的螺旋度,在随访期间有所下降。WSS随时间的变化与收缩压有关，主动脉瓣峰值速度,主动脉瓣反流分数，主动脉僵硬度指数,和归一化流量位移(所有p<0.05)。
结论：在BAV患者中观察到局部WSS随时间增加，无论主动脉生长。增加的WSS包含更大的主动脉面积，需要进一步研究以调查主动脉夹层的可能预测价值。
方法：BAV患者和年龄匹配的健康对照者接受4D流量CMR。区域,收缩期升主动脉WSS峰值，主动脉瓣功能,评估主动脉硬度测量值和主动脉尺寸.在BAV患者中，随访三年后重复进行4D流CMR，并在基线和随访时获得计算机断层扫描血管造影（CTA）。在CTA上测量主动脉生长(体积增加≥5%)。使用线性混合效应模型分析患者主动脉内的局部WSS差异和随时间的WSS变化，并与临床参数相关。
结果：30例BAV患者（年龄34岁[IQR25-41]）纳入随访分析。此外,另外16例BAV患者和32例健康对照(年龄33岁[IQR28~48])被纳入其他区域分析.幅度,轴向，与主动脉生长无关，周向WSS随时间增加（所有p<0.001）。暴露于幅度WSS>95百分位数的健康对照的区域的百分比从21%(基线506/2400区域)增加至31%(随访734/2400区域)(p<0.001)。WSS角度,测量主动脉壁附近的螺旋度,在随访期间有所下降。WSS随时间的变化与收缩压有关，主动脉瓣峰值速度,主动脉瓣反流分数，主动脉僵硬度指数,和归一化流量位移(所有p<0.05)。
结论：在BAV患者中观察到局部WSS随时间增加，无论主动脉生长。增加的WSS包含更大的主动脉面积，需要进一步研究以调查主动脉夹层的可能预测价值。
