Effect of the valve design on pressure drop, pressure recovery, and spatial positioning of vena contracta.

Background: Bioprostheses are complex structures and yield a very complex fluid dynamics. Hence, it can be hypothesized that prosthesis structural characteristics affect the position of the vena contracta and, consequently, influences the pattern and the extent of pressure recovery downstream from the vena contracta. Materials and methods: The study was performed on pericardial aortic prostheses, specifically Crown 21 and 23 (LivaNova PLC, UK), Trifecta 19 and 21 (Edwards Lifescience, USA), and Magna 19 and 21(Abbott, USA), tested in an "ad hoc" devised steady flow loop circuit at four flow rates (10, 15, 20, and 25 L/min). Fluid dynamic quantities were obtained by direct pressure measurement and Doppler interrogation. Results: Pressure drop at 25 L/min flow rate was 26.5 +/- 0.3 mm Hg and 14.9 +/- 0.1 mm Hg for the Trifecta 19 and 21, 37.1 +/- 1.0 mm Hg and 27.3 +/- 0.4 mm Hg for the Magna 19 and 21, and 36.6 +/- 1.0 mm Hg and 22.7 +/- 0.1 mm Hg for Crown 21 and 23, respectively. The vena contracta was shorter for Trifecta compared with the Magna and the Crown in which it developed further downstream and as far as 1 cm from the valve leaflets fringes. The pressure recovery was 54% +/- 1% for Trifecta 21, 39% +/- 1% for Magna 21, and 41% +/- 2% for Crown 23 with different patterns. Conclusion: The design of bioprosthesis affects pressure recovery and the position of the vena contracta. The different patterns of pressure recovery might have clinical impact.