Patient-specific computational fluid hemodynamics in the ascending aorta before and after thoracic endovascular repair

Abstract

Objective: To study hemodynamic variations due to thoracic endovascular aortic repair (TEVAR) by computational fluid dynamics (CFD).

Design & methods: Five patients were prospectively included in the study. For each patient, we collected cardio-computed tomography angiography scans, electrocardiogram measurements, and additional clinical data, including heart rate, systolic and diastolic blood pressures, and blood volumes, both before and after surgery. Such information was used to create patient-specific digital twin models. We conducted CFD simulations by integrating both geometric and clinical parameters of digital twins. Our analysis focused on bulk flow, velocity streamlines, flow distribution, and areas exposed to atherogenic stimuli. We calculated the time-averaged wall shear stress (TAWSS), oscillatory shear index (OSI), and relative residence time (RRT) to assess the conditions before and after TEVAR. Additionally, we measured the geometric parameters of the ascending aorta (length, diameter, and tortuosity) both before and after TEVAR.

Results: Mean age of the patients was 71 years; average time between follow-up appointments was 448 days. Three patients were women and two were men. Small geometric changes appear to occur in the aortic root and ascending aorta following stent insertion. Areas with low TAWSS tend to decrease overall, with a mean reduction of 23.55 % (±22.40); a more pronounced decrease of 29.16 % (±26.51) was observed in the endograft implantation area. The variation trends in areas with high OSI show a considerable level of interpatient variability, but generally tend to increase within the endograft, with an average increase of 5.23 % (±4.30). There is an average reduction of 32.62 % (±15.97) in the mean RRT value for each patient after TEVAR. Systolic flow patterns do not vary significantly. Coronary perfusion levels remain within the ranges reported in the literature. Coronary flow increases in three out of five patients.

Conclusion: No significant geometric remodeling is observed after TEVAR treatments; however, pronounced hemodynamic changes occur, leading to a reduced atherogenic risk. Nonetheless, there is considerable variability among patients.

Keywords: Aorta; CFD; Digital twin; Patient-specific; TEVAR.