Flow characterization of the ADVANTAGE and St. Jude Medical bileaflet mechanical heart valves.

BACKGROUND AND AIM OF THE STUDY

The study aim was to characterize time-dependent flow fields and flow structures within the ADVANTAGE (ADV) and St. Jude Medical (SJM) prosthetic bileaflet mechanical heart valves.

METHODS

Three-dimensional unsteady computational fluid dynamic simulations were conducted in the aortic position for both valves. Flow boundary conditions were acquired from an in-vitro experiment. The governing equations were solved by a finite volume method that employed a moving cell technique to simulate the motion of the valve leaflet in the cardiac cycle. The computed velocities were subsequently validated using the velocities measured in the in-vitro experiment.

RESULTS

Both valves had similar flow phenomena at the geometric symmetry plane of the valve housing, and both experienced a waterhammer effect upon closure. However, flow characteristics in the pivots differed distinctively between both valves. More dynamic flow activity was observed at the bi-level butterfly pivots of the ADV valve. Flow vena contracta and large flow boundary separation zones at the central flow orifice were captured adjacent to the pivots of the SJM valve. During valve opening, retrograde systolic flow at the bottom of the pivot was observed. No persistent flow stases were seen in the pivots of either valves.

CONCLUSION

Although overall flow characterization for both valves was similar, flow features within each valve's pivots correlated to the pivot design. The bi-level butterfly pivot design of the ADV valve appeared to provide relatively easy passages for pivot flow washing.