Bjork-Shiley (Tilting disc) 25 mm
Peak gradient:	12 ± 4 mmHg
Mean gradient:	6 ± 2 mmHg
Peak velocity:	1.75 ± 0.38 m/s
Pressure half-time:	99 ± 27 ms
Effective orifice area:	1.72 ± 0.6 cm2