Hydrodynamic investigation of mechanical bileaflet valves

For hydrodynamic comparison, 11 mechanical bileaflet valves have been perfused in a mock circulation system under pulsatile flow conditions. Six St. Jude Medical valves with different sizes from No. 21 to No. 31 and five Duromedics prostheses with corresponding sizes from No. 21 to No. 29 have been investigated. Flow, pressure, and orifice area were measured, while cardiac output was varied between 2 and 6 L/min. Insufficiency (I), maximal orifice area (Amax), mean orifice area (A), discharge coefficient (CD), performance index (PI), and efficiency index (EI) were determined. The St. Jude Medical valves show higher values of orifice area when compared with the Duromedics valves. For smaller valve sizes up to No. 25, the values of the orifice area are similar. The Duromedics valves show much lower values of insufficiency; thus, for small valve sizes, the Duromedics prosthesis seems to be superior. For larger valve sizes (No. 27, No. 29, and No. 31), a decision has to be made whether higher insufficiency and higher orifice area of the St. Jude Medical valve or lower insufficiency with lower orifice area is more acceptable.