Educational draft · awaiting clinical reviewThe full textbook explains uncertainty but does not replace live national or local guidance, specialist advice, or current prescribing information.
Select and monitor antithrombotic therapy, recognise prosthetic dysfunction and act safely on thrombosis or bleeding.
Mechanical valves are durable but thrombogenic; bioprostheses avoid lifelong valve-driven anticoagulation but can thrombose or degenerate. Antithrombotic decisions therefore depend on prosthesis, position, time from implantation and independent indications such as AF.
Prosthetic obstruction may be thrombus, pannus, endocarditis or structural degeneration. Management is imaging-led and urgent because empiric changes in anticoagulation cannot safely distinguish these causes.
Artificial surfaces and altered flow activate platelets and coagulation. Slower flow across mitral and tricuspid mechanical valves increases thrombosis risk compared with many modern aortic prostheses.
Missed warfarin, dietary change, vomiting, interacting medicines or an inappropriate target can leave a mechanical valve underprotected. Thrombus may form before symptoms or obstruction appear.
Drug interactions, acute illness, liver dysfunction or dosing error can raise anticoagulant effect and bleeding risk. The hazard depends on bleeding site and clinical severity, not the INR alone.
Pannus, bioprosthetic tissue degeneration, endocarditis or paravalvular dehiscence can obstruct flow or cause regurgitation. These mechanisms require imaging rather than assumed anticoagulation failure.
Non-endothelial surfaces, shear and regions of relative stasis promote thrombin generation and platelet adhesion. Mechanical valves retain this stimulus throughout their lifespan.
A vitamin K antagonist reduces functional clotting factors and limits thrombus formation on mechanical components. Inadequate exposure permits valve thrombosis and systemic embolisation.
Thrombus or pannus restricts disc or leaflet movement, raising the transprosthetic gradient and sometimes causing regurgitation. Acute obstruction can trigger pulmonary oedema or shock.
Bioprosthetic leaflets can thicken, calcify or tear over time. Progressive stenosis or regurgitation then increases chamber pressure or volume load and may cause heart failure.
Excess vitamin K antagonist effect reduces clot formation at injured vessels. Bleeding can become life-threatening, while prolonged reversal leaves a mechanical valve vulnerable to thrombosis.
Acute dyspnoea, pulmonary oedema, shock, embolus, new murmur or a softer/absent mechanical click is an emergency.
Fever, rigors, embolic features, new regurgitation or conduction delay needs urgent cultures and endocarditis-team imaging.
Gradual breathlessness with a rising bioprosthetic gradient or new intraprosthetic regurgitation suggests leaflet degeneration rather than acute thrombus.
Heart failure, a new regurgitant murmur or unexplained haemolytic anaemia after replacement suggests dehiscence/leak; infection must be excluded.
Melaena, haematemesis, haematuria, severe headache, collapse or rapid haemoglobin fall on warfarin demands urgent severity and INR assessment.
Missed doses, dietary change, vomiting/diarrhoea or a new inducer with low INR is clinically important even before symptoms, especially in a mechanical mitral valve.
Thrombus often presents relatively abruptly with a changed click, embolism or rising gradient, especially after subtherapeutic anticoagulation. TOE or cardiac CT helps define it.
Fibrous tissue can gradually grow around a prosthesis and restrict movement despite adequate anticoagulation. Its slow course and imaging characteristics distinguish it from fresh thrombus.
A bioprosthesis may develop leaflet calcification, thickening or tearing, causing progressive stenosis or intraprosthetic regurgitation. Imaging shows abnormal tissue rather than mechanical thrombus.
A small effective prosthetic orifice or increased flow from anaemia or infection can raise gradients without leaflet obstruction. Comparison with the postoperative baseline is especially helpful.
Fever, positive cultures, new regurgitation, conduction delay or haemolytic anaemia suggests infection or dehiscence. TOE assesses vegetations, abscess and leakage around the sewing ring.
Thrombus can immobilise prosthetic components and abruptly block forward flow. Acute dyspnoea, pulmonary oedema, hypotension or a softer mechanical click may signal a haemodynamic emergency.
Valve-associated thrombus can detach and enter the arterial circulation. Stroke, limb ischaemia or organ infarction may occur even before clinically obvious prosthetic obstruction.
Vitamin K antagonist treatment can cause gastrointestinal, intracranial or other critical-site haemorrhage. Immediate haemostasis and reversal require balancing with early planning to protect the valve again.
Infection can destroy adjacent tissue, form an abscess, loosen the sewing ring or impair conduction. Embolism, sepsis and severe regurgitation make this a specialist emergency.
Leaflet degeneration or paravalvular leakage produces chronic pressure or volume overload. High-velocity leak jets may fragment red cells, causing haemolytic anaemia alongside progressive heart failure.
A target of 2.5 generally means a working range around 2.0-3.0; documenting only a broad range encourages drift to its lower edge.
Slower flow makes mitral and tricuspid mechanical valves more thrombogenic than aortic prostheses.
DOACs are not recommended for mechanical prostheses; a mechanical-valve patient should remain on a VKA.
Thrombus, pannus, structural degeneration, prosthesis-patient mismatch and a high-flow state require different treatment.
Mechanical-valve anticoagulation in pregnancy is high risk for both mother and fetus and requires a Pregnancy Heart Team before conception wherever possible.
Switching a mechanical-valve patient from warfarin to a DOAC for convenience.
Using one INR target for every mechanical valve without checking position, design and risk factors.
Giving routine dual antiplatelet therapy or adding aspirin to warfarin without a separate indication.
Treating a rising prosthetic gradient as thrombus without multimodality imaging.
Stopping warfarin for a procedure without a dated interruption, bridging and restart plan.
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A 55-year-old with a mechanical mitral valve asks to replace warfarin with apixaban because INR checks are inconvenient. What is the best response?
National guidance is shown before implementation-dependent detail. Typical adult dose examples remain subject to patient factors, contraindications and the live BNF or specialist protocol. Source check completed 27 Aug 2026; clinical approval remains outstanding.
Editorial contact: Doctor’s Passport editorial team. Source-check date is separate from clinical approval. Report a content problem · Content changes
Narrow therapeutic index, major interactions, teratogenicity and bleeding. Do not copy a loading schedule without specialist assessment; record target and monitoring plan.
GI/other bleeding, aspirin hypersensitivity and additive bleeding with anticoagulants; do not add routinely to therapeutic warfarin.
Bleeding and drug interactions; dual antiplatelet therapy is not routine solely because of TAVI.
IV administration must be slow; reversal can make re-anticoagulation difficult, but haemostasis takes priority in life-threatening bleeding.
This is a product-specific regimen, not an interchangeable dose for every PCC. Use coagulation-expert supervision, check INR and clinical haemostasis, and monitor for thrombosis, DIC or anaphylaxis; Beriplex contains heparin and is contraindicated with a known history of HIT. A mechanical valve has high re-thrombosis risk, so reconsider anticoagulation as soon as haemostasis permits.