[Comparative study of mechanical heart valves for implantation in mitral position]

For hydrodynamic comparison of mechanical heart valves, three tilting disc valves (Björk-Shiley SD, Björk-Shiley CCD, Björk-Shiley Monostrut) and two bileaflet valves (St. Jude Medical, Duromedics) with annulus diameter dA = 31 mm were perfused in a mock circulation in mitral position. Flow, pressure, and orifice area were measured during pulsatile flow. Insufficiency, maximal orifice area, mean orifice area, performance index and efficiency index were calculated. The tilting disc valves show distinctly lower orifice areas than the bileaflet valves. The mean value of maximal orifice area Amax of the Björk-Shiley prostheses varies between 227.82 +/- 7.77 mm2 and 243.21 +/- 6.21 mm2. The mean value of Amax of the Duromedics prosthesis is 295.45 +/- 7.76 mm2 and that of the St. Jude Medical prosthesis is 477.43 +/- 11.32 mm2. The calculated mean orifice areas A of the bileaflet valves are also higher than those of the tilting disc valves. The mean values of A are: Björk-Shiley SD: 183.55 +/- 10.03 mm2; Björk-Shiley CCD: 206.30 +/- 8.62 mm2; Björk-Shiley Monostrut: 210.12 +/- 4.74 mm2; St. Jude Medical: 398.69 +/- 19.55 mm2; Duromedics: 262.90 +/- 6.84 mm2. The performance index PI is qualitatively identical with the values of the mean orifice area A because in this study only heart valves of the same size were investigated. For calculation of insufficiency I the entire reflux volume VR including closing volume VS and leakage volume VL was used, thus, insufficiency was also determined in intact prostheses. The values of insufficiency of the mechanical valves investigated are higher for the bileaflet valves than for the tilting disc valves.(ABSTRACT TRUNCATED AT 250 WORDS)