Qualitative and Quantitative Assessments of Blood Flow on Tears in Type B Aortic Dissection With Different Morphologies

Simone Saitta; Baolei Guo; Selene Pirola; Claudia Menichini; Daqiao Guo; Yan Shan; Zhihui Dong; Xiao Yun Xu; Weiguo Fu

doi:10.3389/fbioe.2021.742985

Qualitative and Quantitative Assessments of Blood Flow on Tears in Type B Aortic Dissection With Different Morphologies

Front Bioeng Biotechnol. 2021 Oct 8:9:742985. doi: 10.3389/fbioe.2021.742985. eCollection 2021.

Authors

Simone Saitta^{1

2}, Baolei Guo³, Selene Pirola¹, Claudia Menichini¹, Daqiao Guo³, Yan Shan⁴, Zhihui Dong³, Xiao Yun Xu¹, Weiguo Fu³

Affiliations

¹ Department of Chemical Engineering, Imperial College London, London, United Kingdom.
² Department of Electronics Information and Bioengineering, Politecnico di Milano, Milan, Italy.
³ Department of Vascular Surgery, Zhongshan Hospital, Institute of Vascular Surgery, Fudan University, Shanghai, China.
⁴ Department of Radiology, Zhongshan Hospital, Fudan University, Shanghai, China.

Abstract

Objective: The interactions between aortic morphology and hemodynamics play a key role in determining type B aortic dissection (TBAD) progression and remodeling. The study aimed to provide qualitative and quantitative hemodynamic assessment in four different TBAD morphologies based on 4D flow MRI analysis. Materials and Methods: Four patients with different TBAD morphologies underwent CT and 4D flow MRI scans. Qualitative blood flow evaluation was performed by visualizing velocity streamlines and flow directionality near the tears. Quantitative analysis included flow rate, velocity and reverse flow index (RFI) measurements. Statistical analysis was performed to evaluate hemodynamic differences between the true lumen (TL) and false lumen (FL) of patients. Results: Qualitative analysis revealed blood flow splitting near the primary entry tears (PETs), often causing the formation of vortices in the FL. All patients exhibited clear hemodynamic differences between TL and FL, with the TL generally showing higher velocities and flow rates, and lower RFIs. Average velocity magnitude measurements were significantly different for Patient 1 (t = 5.61, p = 0.001), Patient 2 (t = 3.09, p = 0.02) and Patient 4 (t = 2.81, p = 0.03). At follow-up, Patient three suffered from left renal ischemia because of FL collapse. This patient presented a complex morphology with two FLs and marked flow differences between TL and FLs. In Patient 4, left renal artery malperfusion was observed at the 32-months follow-up, due to FL thrombosis growing after PET repair. Conclusion: The study demonstrates the clinical feasibility of using 4D flow MRI in the context of TBAD. Detailed patient-specific hemodynamics assessment before treatment may provide useful insights to better understand this pathology in the future.

Keywords: 4D flow MRI; aortic remodeling; flow imaging; thoracic endovascular aortic repair (TEVAR); type B aortic dissection.