Bjork-Shiley Valve (B-S) : This is one of the earliest types of tilting disc valves introduced in early 70's. The earlier models like concavo-convex disc valves were withdrawn from market because of mechanical failure. The monostrut B-S valve was introduced in 1982. It has a pyrolitic carbon disc and cage made of Cobalt-chromium alloy. The disc opens to 70". Anticoagulation and endocarditis prophylaxis are mandatory. Mechanical failure is not reported. This valve is rarely used now.