Numerical analysis of the hemodynamic performance of bileaflet mechanical heart valves at different implantation angles.

Background And Aim Of The Study: The effects of the implantation angle of bileaflet mechanical heart valves (BMHVs) on the sinus region and downstream flow profiles were investigated. Three-dimensional numerical simulations of BMHVs were performed under physiologic pulsatile flow conditions. The study aim was to examine how the flow fields of different aortic sinus shapes and the downstream aortic arch geometry would be affected by implantation angle.

Methods: Two geometric models of sinus were investigated: a simplified axisymmetric sinus; and a three-sinus aortic root model, with two different downstream geometries, namely a straight pipe and a simplified curved aortic arch. A 29 mm St. Jude Medical BMHV geometric model was used and positioned at four different angles (0 degrees, 30 degrees, 60 degrees and 90 degrees).

Results: The simulation results showed variation in downstream flow profiles at different implantation angles. Generally, at position Z = 1D along the centerline (where Z refers to the axis normal to the x-y plane and D is the inlet diameter), the triple-jet structures were observed with a slight shift of the center jet for three-sinus aortic cases. Apparent differences were observed at position Z = 2D and 4D, such as higher velocity profiles at the inner arch wall. The flow field downstream of the valve implanted at 0 degrees (anatomic position) showed the smallest overall asymmetry at peak systole, while the flow field downstream of the valve implanted at 90 degrees (anti-anatomic position) exhibited high regions of recirculation.

Conclusion: Valve orientation was found not to affect the shear stress distribution significantly in the downstream aorta, and this was in agreement with the findings of earlier studies.