There are two general types of valves commonly used in valve replacement today: mechanical and biologic valves. The mechanical valve is composed of a fabric sutured edge + metal ring + pyrolytic carbon leaflet. The disadvantage is that it requires a lifetime of anticoagulant medication, and the dosage of anticoagulant medication is individualized (i.e., each person takes a different amount of medication, which requires periodic blood coagulation tests to determine), which is relatively cumbersome.