Classified as biological (tissue) or mechanical.
Biological valves are divided into homografts (allografts) or heterografts (xenografts).
Mechanical valves are subdivided into ball-in-cage, single or double tilting disk types.
Homograft aortic and pulmonary valves are harvested from human cadavers.
Heterograft valves are porcine valves or made up of bovine pericardium.
Patients with first generation aortic valves, and mitral valves are at higher risk of stroke than patients with newer valves and those with aortic valve replacements.
Risk of stroke in patients with mechanical valves and in whom warfarin has been stopped is estimated at 0.08-3.6% per day while the INR is subtherapeutic.
Complications of mechanical prostheses include most commonly thromboembolism, valve dehiscence, endocarditis of the valve ring, pannus formation with stenosis, para valvular leak and perivalvular abscess.
With mechanical prosthetic heart valve lifelong thromboprophylaxis is recommended with warfarin.
For short term anticoagulation when warfarin is started or temporarily int2242upted low molecular weight heparin is used for bridge anticoagulation during the time the patient is not anticoagulated with warfarin.