University thesis:
Dissertation, Albert-Ludwigs-Universität Freiburg, 2016
Footnote:
Description:
Zusammenfassung: Objective: We carried out 4D flow-sensitive MRI to analyze the evolution of hemodynamics in the thoracic aorta in patients with repaired aortic coarctation (CoA) while aiming to detect specific characteristics of patients with coexistent bicuspid aortic valve (BAV).Methods: Two 4D flow MRI scans (mean time interval 4.4 ± 1.2 years) were performed in 28 CoA patients (mean age t1: 14.6 ± 7.9 years, t2: 19.0 ± 8.3 years). We assessed wall shear stress (WSS), peak velocities and oscillatory shear index (OSI) at 9 defined levels of the thoracic aorta and measured aortic diameters at 4 defined locations (ascending (AAo) & descending (DAo) aorta, arch, CoA). Aortic blood flow was visualized by 3D particle traces. For statistical analysis, patients who underwent intervention and those with BAV were evaluated separately.Results: Quantitative analysis showed an overall decrease in WSS (mean t1:0.48±0.18 N/m², t2: 0.33±0.13 N/m²; p< 0.005) and an overall increase in OSI (t1:7.16±4.05, t2:9.98±4.76, p< 0.05). AAo/DAo ratio decreased in all subgroups (t1:1.44±0.29, t2: 1.34±0.18, p= 0.017) while we observed no significant alteration in relative diameters of the aortic arch or at the CoA site. Peak velocities dropped significantly in the AAo (t1:1.42±0.37m/s, t2: 1.27±0.37m/s; p< 0.001). BAV patients revealed lower OSI and higher WSS in the AAo (p>0.05) and lower peak velocities in the aortic arch, the CoA site and the DAo (p< 0.05). The total number of secondary flow patterns decreased, whereas the number of additional localized helices increased.Conclusion: In patients with repaired CoA, we noted the normalization of aortic hemodynamics. Patients with BAV showed specific characteristics in quantitative parameters. 4D flow-sensitive MRI permits the evaluation of qualitative and quantitative aortic changes in CoA patients over time that are not limited to the CoA site