BackgroundThe relationship between blood flow characteristics and ascending aortic (AA) dilatation has not been studied in patients with a tricuspid aortic valve (TAV) without aortic stenosis.
PurposeTo evaluate whether four-dimensional (4D) flow characteristics determined in MRI are related to AA dilatation by comparing dilated AA and non-dilated AA subjects with TAV.
Study type
Prospective.Population 20 patients with dilated AA, 20 age-matched patients with non-dilated AA.
Field Strength/Sequence1.5T/4D flow, 2D flow and anatomic images.
AssessmentAltogether 16 different 4D flow parameters were assessed in 10 planes in the thoracic aorta. Intra-and inter-observer reproducibility were analyzed.
Statistical testIndependent T-test for normal-distributed and Mann-Whitney-test for skewed distributed parameters were used. Paired-samples T-test was used to compare 2D and 4D flow parameters. Intraclass correlation coefficient (ICC) was used in intra-and inter-observer reproducibility analysis.
ResultsAortic flow was displaced from the center line of the aorta in the proximal and tubular planes. Flow displacement (FD) was greatest in the proximal plane of AA and was higher in dilated AA (4.5%, range 3.0-5.8%) than in non-dilated AA (2.0%, 1.0-3.0%, p<0.001). Total wall shear stress (WSS) values were 1.3±0.4 times higher on the displaced side than on the opposite side of the aorta (p<0.01). The circumferential WSS (WSSC) ratio to total WSS was greater in dilated AA, being 0.48±0.11 vs. 0.32±0.09 in the inner curvature of the proximal AA (p<0.001) and 0.37±0.11 vs. 0.26±0.07 in whole aortic ring in the distal AA (p<0.001). Depending on 4D flow parameter, reproducibility varied from excellent (ICC=0.923) to very low (ICC=0.204).
Data conclusionThe present study demonstrates that 4D flow measurements help to visualize the pathological flow patterns related to aortic dilatation. Flow displacement and an increased WSSc/WSS ratio are significantly associated with AA dilatation.
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