Fully quantitative mapping of abnormal aortic velocity and wall shear stress direction in patients with bicuspid aortic valves and repaired coarctation using 4D flow cardiovascular magnetic resonance

Abstract

Background Helices and vortices in thoracic aortic blood flow measured with 4D flow cardiovascular magnetic resonance (CMR) have been associated with aortic dilation and aneurysms. Current approaches are semi-quantitative or when fully quantitative based on 2D plane placement. In this study, we present a fully quantitative and three-dimensional approach to map and quantify abnormal velocity and wall shear stress (WSS) at peak systole in patients with a bicuspid aortic valve (BAV) of which 52% had a repaired coarctation. Methods 4D flow CMR was performed in 48 patients with BAV and in 25 healthy subjects at a spatiotemporal resolution of 2.5 × 2.5 × 2.5mm3/ ~ 42 ms and TE/TR/FA of 2.1 ms/3.4 ms/8° with k-t Principal Component Analysis factor R = 8. A 3D average of velocity and WSS direction was created for the normal subjects. Comparing BAV patient data with the 3D average map and selecting voxels deviating between 60° and 120° and > 120° yielded 3D maps and volume (in cm3) and surface (in cm2) quantification of abnormally directed velocity and WSS, respectively. Linear regression with Bonferroni corrected significance of P < 0.0125 was used to compare abnormally directed velocity volume and WSS surface in the ascending aorta with qualitative helicity and vorticity scores, with local normalized helicity (LNH) and quantitative vorticity and with patient characteristics. Results The velocity volumes > 120° correlated moderately with the vorticity scores (R ~ 0.50, P < 0.001 for both observers). For WSS surface these results were similar. The velocity volumes between 60° and 120° correlated moderately with LNH (R = 0.66) but the velocity volumes > 120° did not correlate with quantitative vorticity. For abnormal velocity and WSS deviating between 60° and 120°, moderate correlations were found with aortic diameters (R = 0.50–0.70). For abnormal velocity and WSS deviating > 120°, additional moderate correlations were found with age and with peak velocity (stenosis severity) and a weak correlation with gender. Ensemble maps showed that more than 60% of the patients had abnormally directed velocity and WSS. Additionally, abnormally directed velocity and WSS was higher in the proximal descending aorta in the patients with repaired coarctation than in the patients where coarctation was never present. Conclusion The possibility to reveal directional abnormalities of velocity and WSS in 3D provides a new tool for hemodynamic characterization in BAV disease.

Wall shear stress and relative residence time as potential risk factors for abdominal aortic aneurysms in males: a 4D flow cardiovascular magnetic resonance case–control study

“…WSS can also be assessed with three-dimensional (3D), time-resolved phase-contrast cardiovascular magnetic resonance (CMR) imaging with three-directional velocity encoding (4D flow CMR), that allows for 3D blood flow quantification in the vasculature throughout the cardiac cycle [ 19 ]. While 4D flow CMR has widely been used to investigate altered WSS in the diseased thoracic aorta [ 20 – 22 ], previous studies of WSS and OSI in patients with AAA are limited. Takehara et al [ 23 ] found reduced peak WSS values and elevated OSI in AAA when compared to non-dilated proximal aortic segments in a cohort of 18 AAA patients.…”

Combining 4D Flow MRI and Complex Networks Theory to Characterize the Hemodynamic Heterogeneity in Dilated and Non-dilated Human Ascending Aortas

“…3 ) can be explained by the presence of large-scale flow recirculation patterns. 19 , 31 , 46 Such flow features have been associated to (1) intimal lipid accumulation 22 in murine and rabbit thoracic aorta, and (2) atherosclerotic and thrombotic biological markers in an arterial replication platform. 32 As explained in Fig.…”

“…6,11,13,23,26 Furthermore, hemodynamic disturbances are intertwined with and exacerbated by concomitant AAo dilation and aortic valve abnormalities, such as bicuspid aortic valve (BAV) or deficient tricuspid aortic valves (TAV). 14,28,36,46 In recent years, 4D flow magnetic resonance imaging (MRI) has been increasingly used to obtain information on both aortic morphology and hemodynamics 5,14,31,35,43 -in particular in the presence of aortic vascular/valve pathologies 4,16,23,31 -providing risk markers of AAo wall degeneration. 14,25,43 With the objective of providing a comprehensive characterization of the spatiotemporal heterogeneity of large-scale aortic flow features and of their possible links with AAo dilation, a recently proposed approach integrating computational hemodynamics with Complex Networks (CNs) theory 7,8,13,37 is here extended for the first time to 4D flow MRI in patients with and without aortic dilation.…”

“… 6 , 11 , 13 , 23 , 26 Furthermore, hemodynamic disturbances are intertwined with and exacerbated by concomitant AAo dilation and aortic valve abnormalities, such as bicuspid aortic valve (BAV) or deficient tricuspid aortic valves (TAV). 14 , 28 , 36 , 46 …”

Abnormal aortic hemodynamics are associated with risk factors for aortic complications in patients with marfan syndrome

“…In this study, we present an aortic 4D flow MRI analysis, providing a comprehensive quantification and visualization of abnormal aortic velocity and WSS magnitude and direction with state-of-the-art techniques [15] , [16] in MFS patients. We hypothesize that an abnormal hemodynamic profile could be found in aortic regions which are known predilection sites for aortic dissection (aortic root and proximal descending aorta).…”