Medtronic-Hall Valve :  This is a low profile central tilting disc valve. The disc is made of pyrolitic carbon and housing is single piece of machined titanium. Introduced in 1977, this is one of the first rotatable valves. After sutures are tied-off, valve can be rotated to the ideal position without obstruction of the disc. Anticoagulation and prophylaxis against endocarditis are mandatory. Mechanical failures have not been reported.