Background Abdominal aortic aneurysms (AAA) can lead to catastrophic events such as dissection or rupture, and are an expression of general aortic disease. Low wall shear stress (WSS), high oscillatory shear index (OSI), and high relative residence time (RRT) have been correlated against increased uptake of inflammatory markers in the vessel wall and may improve risk stratification of AAA. We sought to obtain a comprehensive view of WSS, OSI, and RRT in the whole aorta for patients with AAA and age-matched elderly controls and young normal controls. Methods 4D Flow cardiovascular magnetic resonance images of the whole aorta were acquired in 18 AAA patients (70.8 +/- 3.4 years), 22 age-matched controls (71.4 +/- 3.4 years), and 23 young subjects (23.3 +/- 3.1 years), all males. Three-dimensional segmentations of the whole aorta were created for all timeframes using a semi-automatic approach. The aorta was divided into five segments: ascending aorta, arch, descending aorta, suprarenal and infrarenal abdominal aorta. For each segment, average values of peak WSS, OSI, and RRT were computed. Students t-tests were used to compare values between the three cohorts (AAA patients vs elderly controls, and elderly controls vs young controls) where the data were normally distributed, and the non-parametric Wilcoxon rank sum tests were used otherwise. Results AAA patients had lower peak WSS in the descending aorta as well as in the abdominal aorta compared to elderly controls (p <= 0.001), similar OSI, but higher RRT in the descending and abdominal aorta (p <= 0.001). Elderly controls had lower peak WSS compared to young controls throughout the aorta (p < 0.001), higher OSI in all segments except for the infrarenal aorta (p < 0.001), and higher RRT throughout the aorta, except the infrarenal aorta (p < 0.001). Conclusions This study provides novel insights into WSS, OSI, and RRT in patients with AAA in relation to normal ageing, highlighting how AAA patients have markedly abnormal hemodynamic stresses not only in the infrarenal, but in the entire aorta. Moreover, we identified RRT as a marker for abnormal AAA hemodynamics. Further investigations are needed to explore if RRT or other measures of hemodynamics stresses best predict AAA growth and/or rupture.

Aims Patients with bicuspid aortic valve (BAV) and aortic regurgitation have higher rate of aortic complications compared with patients with BAV and stenosis, as well as BAV without valvular disease. Aortic regurgitation alters blood haemodynamics not only in systole but also during diastole. We therefore sought to investigate wall shear stress (WSS) during the whole cardiac cycle in BAV with aortic regurgitation.Methods and results Fifty-seven subjects that underwent 4D flow cardiovascular magnetic resonance imaging were included: 13 patients with BAVs without valve disease, 14 BAVs with aortic regurgitation, 15 BAVs with aortic stenosis, and 22 normal controls with tricuspid aortic valve. Peak and time averaged WSS in systole and diastole and the oscillatory shear index (OSI) in the ascending aorta were computed. Students t-tests were used to compare values between the four groups where the data were normally distributed, and the non-parametric Wilcoxon rank sum tests were used otherwise. BAVs with regurgitation had similar peak and time averaged WSS compared with the patients with BAV without valve disease and with stenosis, and no regions of elevated WSS were found. BAV with aortic regurgitation had twice as high OSI as the other groups (P <= 0.001), and mainly in the outer mid-to-distal ascending aorta.Conclusion OSI uniquely characterizes altered WSS patterns in BAVs with aortic regurgitation, and thus could be a haemodynamic marker specific for this specific group that is at higher risk of aortic complications. Future longitudinal studies are needed to verify this hypothesis. Graphical Abstract Patients with bicuspid aortic valve and aortic regurgitation present with regions of elevated oscillatory shear index in the ascending aorta, namely in the outer mid-to-distal segments. The 2D map represents segments with higher oscillatory shear index for a group of patients with bicuspid aortic valve and aortic regurgitation compared with patients with bicuspid aortic valve without valve disease. I, inner edge of ascending aorta, identified based on the inner insertion of the aortic annulus; O, outer edge; R, right edge; L, left edge.

Aims Understanding the mechanisms underlying ascending aortic dilation is imperative for refined risk stratification of these patients, particularly among incidentally identified patients, most commonly presenting with tricuspid valves. The aim of this study was to explore associations between ascending aortic haemodynamics, assessed using four-dimensional flow cardiovascular magnetic resonance imaging (4D flow CMR), and circulating biomarkers in aortic dilation. Methods and results Forty-seven cases with aortic dilation (diameter >= 40 mm) and 50 sex-and age-matched controls (diameter < 40 mm), all with tricuspid aortic valves, underwent 4D flow CMR and venous blood sampling. Associations between flow displacement, wall shear stress (WSS), and oscillatory shear index in the ascending aorta derived from 4D flow CMR, and biomarkers including interleukin-6, collagen type I alpha 1 chain, metalloproteinases (MMPs), and inhibitors of MMPs derived from blood plasma, were investigated. Cases with dilation exhibited lower peak systolic WSS, higher flow displacement, and higher mean oscillatory shear index compared with controls without dilation. No significant differences in biomarkers were observed between the groups. Correlations between haemodynamics and biomarkers were observed, particularly between maximum time-averaged WSS and interleukin-6 (r = 0.539, P < 0.001), and maximum oscillatory shear index and collagen type I alpha 1 chain (r = -0.575, P < 0.001 in cases). Conclusion Significant associations were discovered between 4D flow CMR derived whole-cardiac cycle WSS and circulating biomarkers representing inflammation and collagen synthesis, suggesting an intricate interplay between haemodynamics and the processes of inflammation and collagen synthesis in patients with early aortic dilation and tricuspid aortic valves.