In vitro fluid dynamic characteristics of the Medtronic-Hall pivoting disc heart valve prosthesis

The need for better low-profile mechanical valves led to the design and development of the Medtronic-Hall (formerly known as the Hall-Kaster valve) pivoting disc heart valve prosthesis in 1976. In vitro flow studies indicate that it has improved pressure drop characteristics compared to the Lillehei-Kaster and convexoconcave Björk-Shiley (60 degrees model) tilting disc valves. It does, however, have a somewhat larger regurgitant volume compared to the Björk-Shiley valve design. Velocity measurements with a laser-Doppler anemometer in the immediate downstream vicinity of the Medtronic-Hall valve indicate no region of stagnation near the outflow face of the disc. Regions of stagnation were, however, observed adjacent to the two titanium "pivot stops" situated on either side of the disc in the major orifice and along the pivot post in the minor orifice, together with a region of flow separation adjacent to the sewing ring of the minor outflow region. The results of the present in vitro study indicate a small but significant improvement in the overall fluid dynamic performance of the Medtronic-Hall valve, compared to the convexo-concave Björk-Shiley (60 degrees model) and Lillehei-Kaster tilting disc prostheses in current clinical use.