Bjork-Shiley (Tilting disc) 31 mm
Peak gradient:	6 ± 3 mmHg
Mean gradient:	2 ± 1.9 mmHg
Peak velocity:	1.41 ± 0.26 m/s
Pressure half-time:	70 ± 14 ms
Effective orifice area:	2.2 ± 0.3 cm2