Prosthetic heart valves and anticoagulation

01OverviewDefinition, clinical context and the essential points that orientate the chapter.

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.

Key points

Every mechanical valve requires lifelong vitamin K antagonist therapy; a DOAC is not an acceptable substitute.
The INR target is valve- and patient-specific: a modern bileaflet mechanical aortic valve commonly targets 2.5, while a mechanical mitral valve or added thromboembolic risk commonly targets 3.0; older high-thrombogenicity valves need higher targets.
A low INR risks valve thrombosis and embolism; a high INR risks bleeding. Use the implant record, valve position/type and risk factors to document one target explicitly.
After TAVI without another anticoagulation indication, NICE advises single antiplatelet therapy with aspirin, or clopidogrel if aspirin is not tolerated; do not add routine oral anticoagulation.
Early antithrombotic therapy after a surgical bioprosthesis differs by position; mitral/tricuspid valves have greater early thrombosis risk than aortic valves.
New symptoms or a changed click, gradient or regurgitation demand prompt TTE, then TOE/CT/fluoroscopy as needed; do not assume anticoagulation failure before defining obstruction.
Periprocedural interruption and bridging are determined by both bleeding risk and valve-thrombosis risk; a mechanical mitral valve is not equivalent to a low-risk bileaflet aortic valve.
Stable warfarin control still requires interaction, illness, alcohol, diet and adherence review; check INR 3-5 days after starting an interacting medicine.

02AetiologyUnderlying causes, associations and risk factors, with why each one matters.

Mechanical prosthesis thrombogenicity

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.

Insufficient anticoagulant effect

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.

Excess anticoagulant effect

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.

Non-thrombotic prosthetic dysfunction

Pannus, bioprosthetic tissue degeneration, endocarditis or paravalvular dehiscence can obstruct flow or cause regurgitation. These mechanisms require imaging rather than assumed anticoagulation failure.

03PathophysiologyThe causal sequence from the underlying abnormality to symptoms and harm.

1
Prosthetic flow activates coagulation
Non-endothelial surfaces, shear and regions of relative stasis promote thrombin generation and platelet adhesion. Mechanical valves retain this stimulus throughout their lifespan.
2
Anticoagulation suppresses thrombus
A vitamin K antagonist reduces functional clotting factors and limits thrombus formation on mechanical components. Inadequate exposure permits valve thrombosis and systemic embolisation.
3
Obstruction impairs haemodynamics
Thrombus or pannus restricts disc or leaflet movement, raising the transprosthetic gradient and sometimes causing regurgitation. Acute obstruction can trigger pulmonary oedema or shock.
4
Biological tissue deteriorates
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.
5
Anticoagulation weakens haemostasis
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.

04Clinical features and red flagsSymptoms, examination findings, patterns of presentation and time-critical warnings.

Obstructive valve thrombosisRed flag

Acute dyspnoea, pulmonary oedema, shock, embolus, new murmur or a softer/absent mechanical click is an emergency.

Prosthetic endocarditisRed flag

Fever, rigors, embolic features, new regurgitation or conduction delay needs urgent cultures and endocarditis-team imaging.

Structural degeneration

Gradual breathlessness with a rising bioprosthetic gradient or new intraprosthetic regurgitation suggests leaflet degeneration rather than acute thrombus.

Paravalvular leak

Heart failure, a new regurgitant murmur or unexplained haemolytic anaemia after replacement suggests dehiscence/leak; infection must be excluded.

Anticoagulant harmRed flag

Melaena, haematemesis, haematuria, severe headache, collapse or rapid haemoglobin fall on warfarin demands urgent severity and INR assessment.

Subtherapeutic anticoagulation

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.

05InvestigationsWhat to request, why it matters and how to interpret it.

Investigation order

Read from the initial assessment onwards. Tests may run in parallel in urgent care; first-line, preferred, confirmatory, definitive and gold-standard labels appear only when the chapter explicitly states them.

01
INR with anticoagulation recordFirst step
Why
Measure current VKA effect and time in therapeutic range.
Interpretation and limitations
Interpret against the documented target, not a generic 2-3 range; low values support but do not prove thrombus.
02
Transthoracic echocardiography
Why
Compare gradients, effective orifice area, regurgitation and ventricular response with the postoperative baseline.
Interpretation and limitations
A rise from baseline is more useful than an isolated gradient; high flow, mismatch and obstruction can look similar.
03
TOE
Why
Assess leaflet/disc motion, thrombus, pannus, vegetations and paravalvular complications.
Interpretation and limitations
Urgent for suspected obstruction or endocarditis when TTE is non-diagnostic.
04
Gated cardiac CT and cinefluoroscopy
Why
Define mechanical leaflet opening and distinguish low-attenuation thrombus from pannus; assess bioprosthetic leaflet thickening.
Interpretation and limitations
Use when echo mechanism remains uncertain or procedural planning requires anatomy.
05
FBC, renal/liver profile, haemolysis screen and group-and-save
Why
Quantify bleeding/end-organ risk and detect paravalvular haemolysis.
Interpretation and limitations
Falling haemoglobin, raised LDH, low haptoglobin and fragments support mechanical haemolysis but do not locate the leak.
06
Three sets of blood cultures before antibiotics when stable
Why
Identify prosthetic valve endocarditis.
Interpretation and limitations
Do not delay antibiotics in sepsis or shock; negative cultures after prior antibiotics do not exclude infection.

06Differential diagnosisRealistic alternatives and the features that help distinguish them.

Prosthetic valve thrombus

Thrombus often presents relatively abruptly with a changed click, embolism or rising gradient, especially after subtherapeutic anticoagulation. TOE or cardiac CT helps define it.

Pannus

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.

Structural valve degeneration

A bioprosthesis may develop leaflet calcification, thickening or tearing, causing progressive stenosis or intraprosthetic regurgitation. Imaging shows abnormal tissue rather than mechanical thrombus.

Mismatch or high-flow state

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.

Endocarditis or paravalvular leak

Fever, positive cultures, new regurgitation, conduction delay or haemolytic anaemia suggests infection or dehiscence. TOE assesses vegetations, abscess and leakage around the sewing ring.

07ManagementImmediate care, first-line treatment, alternatives and escalation.

01RoutineSelect antithrombotic therapyFirst stepAfter valve replacement or when reviewing an established prosthesis.

1Identify valve type, manufacturer, position, implant date and separate indications for anticoagulation.
2For any mechanical valve, use lifelong warfarin with a written target INR; do not use a DOAC.
3For a surgical bioprosthesis, decide early aspirin versus VKA by valve position and bleeding risk; after the initial phase continue anticoagulation only for another indication unless the valve team specifies otherwise.
4After TAVI without another anticoagulation indication, use single antiplatelet therapy; if AF/VTE requires anticoagulation, use anticoagulation alone unless a separate recent coronary indication requires antiplatelet therapy.

02ThrombosisSuspected prosthetic valve thrombosisNew obstruction, embolism, acute heart failure or changed mechanical sounds.

1Admit, monitor, check INR and obtain urgent TTE; involve the valve/cardiothoracic team immediately if unstable.
2Use TOE plus CT or fluoroscopy to confirm obstruction and distinguish thrombus from pannus/degeneration.
3If obstructive mechanical thrombosis causes shock, choose emergency surgery or fibrinolysis through an expert multidisciplinary decision based on surgical availability, thrombus burden and bleeding risk.
4EscalationIf non-obstructive or stable small thrombus is confirmed, intensify parenteral/VKA anticoagulation with close repeat imaging; escalate for embolism, growth, persistent obstruction or deterioration.

03BleedingMajor warfarin-related bleedingLife-threatening, critical-site or ongoing major bleeding.

1Stop warfarin, resuscitate, send INR/FBC/fibrinogen/group-and-save and identify the bleeding site.
2Give four-factor prothrombin complex concentrate dosed to the pretreatment INR and body weight using its SmPC, plus slow IV phytomenadione 5-10 mg; obtain the INR urgently without delaying resuscitation or haemorrhage control.
3Recheck INR and clinical haemostasis promptly; repeat testing and treat the source with the relevant emergency specialty.
4Once controlled, the valve and bleeding teams must set timing and method of anticoagulation restart; prolonged unplanned interruption exposes a mechanical valve to thrombosis.

04ProcedurePlanned anticoagulant interruptionAn invasive procedure with clinically important bleeding risk.

1Classify procedure bleeding risk and valve thrombotic risk; many minor dental/skin procedures can proceed without stopping therapeutic warfarin.
2If interruption is required, set explicit last-dose and INR-check dates rather than telling the patient simply to stop warfarin.
3Bridge with therapeutic heparin when thrombotic risk is high, such as a mechanical mitral/tricuspid valve, older thrombogenic valve or recent embolism; lower-risk modern bileaflet aortic valves without added risk may not need bridging.
4Restart warfarin when haemostasis permits and continue bridging, when indicated, until the INR is therapeutic.

Key medicines and prescribing safety5 treatments · regimens, roles and cautions

Lifelong thromboprophylaxis for every mechanical valve; temporary therapy for selected new surgical bioprostheses.

Warfarin

SmPC typical induction 10 mg once daily for 2 days and usual maintenance 3-9 mg once daily, but prosthetic-valve dosing must be individualised to INR; common targets are 2.5 for a modern bileaflet aortic valve and 3.0 for a mechanical mitral valve or added risk.

Narrow therapeutic index, major interactions, teratogenicity and bleeding. Do not copy a loading schedule without specialist assessment; record target and monitoring plan.

Single antiplatelet option after TAVI when there is no indication for oral anticoagulation; also an early option after selected surgical aortic bioprostheses.

Aspirin

75 mg by mouth once daily.

GI/other bleeding, aspirin hypersensitivity and additive bleeding with anticoagulants; do not add routinely to therapeutic warfarin.

Alternative single antiplatelet after TAVI when aspirin is not tolerated.

Clopidogrel

75 mg by mouth once daily.

Bleeding and drug interactions; dual antiplatelet therapy is not routine solely because of TAVI.

Sustained VKA reversal while PCC supplies immediate clotting factors.

Phytomenadione (vitamin K1)

5-10 mg by slow IV injection for severe or life-threatening warfarin-related haemorrhage, given with four-factor PCC; reassess INR about 3 hours later.

IV administration must be slow; reversal can make re-anticoagulation difficult, but haemostasis takes priority in life-threatening bleeding.

Rapid factor replacement for major VKA-related bleeding or emergency surgery when immediate correction is required; INR correction is commonly achieved in about 30 minutes.

Four-factor prothrombin complex concentrate (Beriplex P/N example)

For urgent VKA reversal, dose by the pretreatment INR and body weight capped at 100 kg: INR 2.0-3.9, 25 IU factor IX/kg (maximum 2500 IU); INR 4.0-6.0, 35 IU/kg (maximum 3500 IU); INR above 6.0, 50 IU/kg (maximum 5000 IU), by IV injection at the SmPC rate. Give with vitamin K; routine repeat PCC dosing is not supported.

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.

08ComplicationsImportant consequences, why they occur and why they matter clinically.

Obstructive valve thrombosis

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.

Systemic embolism

Valve-associated thrombus can detach and enter the arterial circulation. Stroke, limb ischaemia or organ infarction may occur even before clinically obvious prosthetic obstruction.

Major anticoagulant bleeding

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.

Prosthetic endocarditis

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.

Degeneration, leak and haemolysis

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.

09Monitoring and follow-upTreatment response, safety checks and longer-term review.

Keep valve type, position, manufacturer, implant date and target INR visible in the record and patient-held information.
Check INR at a frequency driven by stability; even stable patients need at least regular scheduled testing, and high-risk/poor control needs 1-2-weekly review.
After an interacting medicine is started, check INR after 3-5 days and again after it stops when interaction persists.
Obtain a baseline post-procedure TTE and compare subsequent gradients/regurgitation against it; new symptoms trigger earlier imaging.
Review bleeding, embolic symptoms, adherence, diet, alcohol, illness and all prescription/OTC/herbal medicines at anticoagulation contacts.
After a confirmed thrombus or treatment change, repeat imaging on the timescale set by thrombus size and haemodynamic effect, not just at annual review.

10Special situationsVariants, exceptions and circumstances that change the usual approach.

INR targets are medians

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.

Position changes risk

Slower flow makes mitral and tricuspid mechanical valves more thrombogenic than aortic prostheses.

DOAC means no for mechanical valves

DOACs are not recommended for mechanical prostheses; a mechanical-valve patient should remain on a VKA.

A rising gradient has a differential

Thrombus, pannus, structural degeneration, prosthesis-patient mismatch and a high-flow state require different treatment.

Pregnancy needs advance planning

Mechanical-valve anticoagulation in pregnancy is high risk for both mother and fetus and requires a Pregnancy Heart Team before conception wherever possible.

11Common pitfallsFrequent interpretation and management errors.

01
Switching a mechanical-valve patient from warfarin to a DOAC for convenience.
02
Using one INR target for every mechanical valve without checking position, design and risk factors.
03
Giving routine dual antiplatelet therapy or adding aspirin to warfarin without a separate indication.
04
Treating a rising prosthetic gradient as thrombus without multimodality imaging.
05
Stopping warfarin for a procedure without a dated interruption, bridging and restart plan.