Evaluation of 3D blood flow patterns and wall shear stress in the normal and dilated thoracic aorta using flow-sensitive 4D CMR

Background: the purpose of this study was to investigate 3d flow patterns and vessel wall parameters in patients with dilated ascending aorta,age-matched subjects,and healthy volunteers. methods. thoracic time-resolved 3d phase contrast cmr with 3-directional velocity encoding was applied to 33 patients with dilated ascending aorta (diameter ≥40 mm,age=60±16 years),15 age-matched normal controls (diameter ≤37 mm,age=68±7.5 years) and 15 young healthy volunteers (diameter ≤30 mm,age=23±2 years). 3d blood flow was visualized and flow patterns were graded regarding presence of supra-physiologic-helix and vortex flow using a semi-quantitative 3-point grading scale. blood flow velocities,regional wall shear stress (wss),and oscillatory shear index (osi) were quantified. results: incidence and strength of supra-physiologic-helix and vortex flow in the ascending aorta (aao) was significantly higher in patients with dilated aao (16/33 and 31/33,grade 0.9±1.0 and 1.5±0.6) than in controls (2/15 and 7/15,grade 0.2 ± 0.6 and 0.6 ± 0.7,p<.05) or healthy volunteers (1/15 and 0/15,grade 0.1 ± 0.3 p<.05). greater strength of the ascending aortic helix and vortex flow were associated with significant differences in aao diameters (p<.05). peak systolic wss in the ascending aorta and aortic arch was significantly lower in patients with dilated aao (p<.0157-.0488). aao diameter positively correlated to time to peak systolic velocities (r=0.30-0.53,p<.04),osi (r=0.33-0.49,p<0.02) and inversely correlated to peak systolic wss (r=0.32-0.40,p<.03). peak systolic wss was significantly lower in aao aneurysms at the right and outer curvature within the aao and proximal arch (p<.01-.05). conclusions: increase in aao diameter is significantly correlated with the presence and strength of supra-physiologic-helix and vortex formation in the aao,as well with decrease in systolic wss and increase in osi. © 2012 bürk et al.; licensee biomed central ltd.