Key result
Small positive aortic orifice inclination angles optimize hemodynamics with more symmetric shear stress.
Why the study?
Does varying the angle of inclination of a percutaneous aortic prosthesis affect the hydrodynamic blood flow and shear stress patterns in the ascending aorta?
Does varying the angle of inclination of a percutaneous aortic prosthesis affect the hydrodynamic blood flow and shear stress patterns in the ascending aorta?
Optimizing the tilt angle of transcatheter aortic valves to a small positive inclination may centralize ascending aortic flow and minimize asymmetric shear stress, potentially reducing adverse aortic remodeling.
Positive TAVR orifice angles may optimize ascending aortic flow patterns; extends in vitro positioning data but leaves clinical remodeling effects open.
Background: Due to the nature of the percutaneous prosthesis deployment process, a variation in its final position is expected. Prosthetic valve placement will define the spatial location of its effective orifice in relation to the aortic annulus. The blood flow pattern in the ascending aorta is related to the aortic remodeling process, and depends on the spatial location of the effective orifice. The hemodynamic effect of small variations in the angle of inclination of the effective orifice has not been studied in detail. Objective: To implement an in vitro simulation to characterize the hydrodynamic blood flow pattern associated with small variations in the effective orifice inclination. Methods: A three-dimensional aortic phantom was constructed, reproducing the anatomy of one patient submitted to percutaneous aortic valve implantation. Flow analysis was performed by use of the Particle Image Velocimetry technique. The flow pattern in the ascending aorta was characterized for six flow rate levels. In addition, six angles of inclination of the effective orifice were assessed. Results: The effective orifice at the -4° and -2° angles directed the main flow towards the anterior wall of the aortic model, inducing asymmetric and high shear stress in that region. However, the effective orifice at the +3° and +5° angles mimics the physiological pattern, centralizing the main flow and promoting a symmetric distribution of shear stress. Conclusion: The measurements performed suggest that small changes in the angle of inclination of the percutaneous prosthesis aid in the generation of a physiological hemodynamic pattern, and can contribute to reduce aortic remodeling.
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Gomes et al. (2017) studied Severe degenerative aortic stenosis (in vitro phantom) (n=1). Variations in the angle of inclination of the effective orifice vs. Zero angle of inclination was evaluated on Hydrodynamic blood flow pattern (velocity and shear stress fields). Small positive angles of inclination (+3° and +5°) of the effective orifice generated a centralized, physiological hemodynamic pattern with symmetric distribution of shear stress compared to negative angles.
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