Prosthetic heart valves: anticoagulation and durability
THE CONTEXT
Mechanical and biological heart valves differ in their anticoagulation requirements, durability and suitability for different patients.
Anticoagulation targets
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The International Normalised Ratio (INR) target* is 3.0–4.0 for ball-and-cage valves such as Starr–Edwards and 2.5–3.0 for bi-leaflet valves such as St Jude.
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The target INR for biological valves with atrial fibrillation is 2.0–3.0.
Mechanical valves
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All mechanical valves require long-term anticoagulation with vitamin K antagonists because they can cause systemic thromboembolism or develop valve thrombosis or obstruction.
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Prosthetic clicks may become inaudible when a mechanical valve malfunctions.
Biological valves
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Biological valves do not require anticoagulants to maintain valve function, although accompanying atrial fibrillation may require anticoagulation, especially in patients undergoing mitral valve replacement.
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Biological valves are less durable than mechanical valves and may degenerate 7 or more years after implantation, particularly in the mitral position.
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Durability is greater in the aortic position and in older patients. Biological valves are particularly appropriate for patients over 65 undergoing aortic valve replacement.
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Younger patients choosing a biological aortic valve to avoid lifelong vitamin K antagonist risks will require redo surgery or a valve-in-valve procedure when it degenerates. A valve-in-valve procedure places a transcatheter aortic valve inside the original biological valve.