Can you use a DOAC with a mechanical heart valve?

No. Warfarin, a vitamin K antagonist, is the only appropriate oral anticoagulant for a mechanical valve. Dabigatran is contraindicated after the RE-ALIGN trial was stopped early for more thromboembolic events and more major bleeding than with warfarin, and apixaban's label says it is not recommended with prosthetic valves. In patients with prosthetic valves, DOACs are an option only for atrial fibrillation with a bioprosthetic valve more than 3 months after implantation.

What is the INR goal for a mechanical mitral valve?

The target is 3.0 (range 2.5 to 3.5) with warfarin. A modern bileaflet mechanical aortic valve without thromboembolic risk factors is kept at 2.5 (range 2.0 to 3.0), rising to 3.0 with atrial fibrillation, previous thromboembolism or LV dysfunction. Older caged-ball valves also need a target of 3.0.

What are the signs of prosthetic valve thrombosis?

Mechanical valve thrombosis presents with obstruction (dyspnea, heart failure, a new stenotic murmur) or with embolic events such as stroke, typically after warfarin has been stopped or the INR has run low. Echocardiography shows a high gradient across the valve, and TEE, CT or fluoroscopy shows restricted leaflet motion and helps separate thrombus from pannus. Obstructive left-sided thrombosis is treated with fibrinolytic therapy or surgery.

Why does a prosthetic valve cause hemolytic anemia?

Red cells are fragmented by shear stress as blood jets through a paravalvular leak or around a malfunctioning mechanical valve. The pattern is intravascular hemolysis: anemia with high LDH and indirect bilirubin, low haptoglobin and schistocytes, and chronic hemosiderinuria can add iron deficiency. Management means finding and fixing the leak, surgically or with catheter-based closure in selected patients, and replacing iron if needed.

What organisms cause prosthetic valve endocarditis?

Early prosthetic valve endocarditis, within 1 year of surgery, is dominated by staphylococci: in the first 2 months Staphylococcus aureus is most frequent, followed by coagulase-negative staphylococci such as Staphylococcus epidermidis, gram-negative bacilli and Candida. From 2 to 12 months, streptococci, S. aureus and coagulase-negative staphylococci predominate, and infection after 1 year resembles native-valve endocarditis. TEE is preferred because TTE has limited sensitivity with prosthetic valves.

Prosthetic Valve Complications: PATCHES Mnemonic

Prosthetic heart valves fail in a small set of testable ways: thrombosis and thromboembolism, bleeding from anticoagulation, endocarditis, paravalvular leak with hemolysis, structural deterioration or pannus, and conduction block, remembered here as PATCHES. Mechanical valves last but need lifelong warfarin (a vitamin K antagonist, VKA): the usual target INR is 2.5 for a bileaflet mechanical aortic valve without thromboembolic risk factors and 3.0 for a mechanical mitral valve or a higher-risk aortic valve, and DOACs are not used (dabigatran is contraindicated and apixaban is not recommended). Bioprosthetic (tissue) valves usually need only aspirin long term but deteriorate faster, especially in younger patients.

PATCHES: the prosthetic valve complications mnemonic

Letter	Complication	Why it happens	Classic stem clue	What to do
P	Paravalvular leak	Blood leaks around the sewing ring instead of through the valve; more common after TAVI than after surgical replacement	New regurgitant murmur, heart failure or hemolysis after valve replacement	Echo to locate it; repair by surgery or, in selected patients without active infection, catheter-based closure
A	Anticoagulant-related bleeding	Lifelong warfarin for mechanical valves	Bleeding with a high INR	Reverse warfarin; prothrombin complex concentrate for significant bleeding
T	Thrombosis and thromboembolism	Interrupted or subtherapeutic warfarin; obstructive thrombosis occurs mainly with mechanical valves	Dyspnea, heart failure or an embolic event (such as stroke) with a low INR; high gradient across the valve	TTE, then TEE, CT or fluoroscopy; obstructive left-sided thrombosis: fibrinolysis or surgery
C	Conduction block	Aortic valve replacement, more often TAVI than surgery; valve ring abscess in endocarditis	New heart block after valve replacement; new AV block during endocarditis	Permanent pacemaker when needed; abscess or heart block in endocarditis is an indication for early surgery
H	Hemolysis	Shear stress fragments red cells, especially with a paravalvular leak or a malfunctioning mechanical valve	Anemia with ↑ LDH, ↑ indirect bilirubin, ↓ haptoglobin and schistocytes; iron deficiency from hemosiderinuria	Look for and treat a paravalvular leak; replace iron if deficient
E	Endocarditis	Early (within 1 year of surgery): staphylococci lead in the first 2 months; late: organisms like native-valve endocarditis	Fever or persistent bacteremia in anyone with a prosthetic valve	Blood cultures and TEE; early surgery for heart failure, abscess, heart block, fungi or resistant organisms, or persistent bacteremia
S	Structural deterioration and pannus	Bioprosthetic leaflets degenerate over years, faster in younger patients; pannus is fibrous tissue ingrowth that narrows a prosthesis	Gradual heart failure and a new stenotic or regurgitant murmur years after bioprosthetic replacement	Echo; reoperation, or a catheter-based valve-in-valve procedure in selected patients

Three of the letters travel together on exams: a paravalvular leak (P) causes hemolysis (H), and endocarditis (E) that spreads into the valve ring causes abscesses and conduction block (C).

Mechanical vs bioprosthetic valves

Feature	Mechanical valve	Bioprosthetic (tissue) valve
Durability	Very durable	Finite; deteriorates faster in younger patients
Long-term antithrombotic therapy	Lifelong warfarin for every patient	Lifelong aspirin if there is no other indication for anticoagulation
Early after surgical implantation	Warfarin	Warfarin (INR about 2.5) for 3 to 6 months is an option if bleeding risk is low
DOACs	Not used: dabigatran contraindicated, apixaban not recommended	An alternative to warfarin for atrial fibrillation starting more than 3 months after implantation
Main trade-off	More bleeding, from lifelong anticoagulation	More reintervention, from faster deterioration
Usual choice for aortic valve replacement	Under age 50	Over age 65; between 50 and 65, individualized

Survival and valve thrombosis rates are similar with the two types; the choice turns on bleeding risk versus durability. The age cutoffs follow durability: ACC/AHA guideline tables put the 15-year risk of structural deterioration of a bioprosthesis at about 30% for a 40-year-old and 50% for a 20-year-old, but under 10% for patients older than 70.

Anticoagulation targets for mechanical valves

Valve	Warfarin target
Bileaflet mechanical aortic valve, no thromboembolic risk factors	INR 2.5 (range 2.0–3.0)
Mechanical aortic valve with atrial fibrillation, previous thromboembolism or LV dysfunction	INR 3.0 (range 2.5–3.5)
Mechanical mitral or tricuspid valve	INR 3.0 (range 2.5–3.5)
Older caged-ball or caged-disk valve	INR 3.0 (range 2.5–3.5)
Any mechanical valve	No DOACs: dabigatran contraindicated, apixaban not recommended

Low-dose aspirin is added to warfarin only in selected cases, for example after thromboembolism despite a therapeutic INR. It never replaces warfarin.

Why not DOACs? In RE-ALIGN, dabigatran was compared with warfarin in patients with mechanical valves, and the trial was stopped early because dabigatran caused more thromboembolic events (valve thrombosis, stroke, transient ischemic attack and myocardial infarction) and more major bleeding. Dabigatran's label now lists a mechanical valve as a contraindication, apixaban's label says it is not recommended with prosthetic valves, and the 2020 ACC/AHA guideline says patients with a mechanical prosthesis and atrial fibrillation should receive a VKA. For how these drugs work, see heparin, warfarin and DOACs.

Valve thrombosis vs pannus

Both obstruct a prosthesis, but the treatment differs:

Feature	Valve thrombosis	Pannus
What it is	Clot on the valve	Fibrous tissue ingrowth
Typical setting	Interrupted or subtherapeutic warfarin, mainly with mechanical valves	Gradual ingrowth, identified on imaging
Imaging	TEE or CT shows thrombus	TEE or CT shows tissue ingrowth
Treatment	Fibrinolysis or surgery	Surgery is favored

The ACC/AHA table for choosing between fibrinolysis and surgery favors surgery with low surgical risk and available expertise, a large clot (> 0.8 cm²), recurrent thrombosis, NYHA class IV symptoms, left atrial thrombus, other valve disease, coronary disease needing revascularization, a contraindication to fibrinolysis, or possible pannus; it favors fibrinolysis with high surgical risk, a small clot (≤ 0.8 cm²), a first episode and NYHA class I to III symptoms.

Bioprosthetic valves can thrombose too; with leaflet degeneration, thrombosis is one of the two causes of bioprosthetic valve dysfunction, and therapeutic warfarin has been associated with less reduced leaflet motion, a sign of leaflet thrombosis, on imaging.

Exam traps

A DOAC for a mechanical valve is the wrong answer. Use warfarin, not dabigatran or apixaban.
Aspirin never replaces warfarin for a mechanical valve; it is only an add-on in selected patients.
Dyspnea or an embolic event with a low INR in someone with a mechanical valve means valve thrombosis until proven otherwise. Obstructive thrombosis needs fibrinolysis or surgery; restarting warfarin alone does not relieve the obstruction.
New AV block during endocarditis signals spread into the valve ring (abscess), an indication for early surgery. Prosthetic valve infections are particularly likely to cause ring abscesses, and TTE sensitivity is limited, so get a TEE. For native-valve endocarditis, see the infective endocarditis Q-bank breakdown.
Early prosthetic valve endocarditis isn't only S. epidermidis. Coagulase-negative staphylococci are the classic association, but in the first 2 months S. aureus is the most frequent cause, followed by coagulase-negative staphylococci, gram-negative bacilli and Candida; late infection looks like native-valve endocarditis (streptococci, S. aureus, coagulase-negative staphylococci, enterococci).
TAVI vs surgical aortic valve replacement: TAVI increases the need for a permanent pacemaker and causes more paravalvular regurgitation.
Hemolysis after valve replacement can leave iron deficiency from chronic hemosiderinuria.
Pregnancy: warfarin crosses the placenta and can cause fetal abnormalities, mainly in the first trimester, but the risk is dose-dependent and very low at 5 mg/day or less. Substituting heparin for warfarin in the first 12 weeks and the last 2 weeks of pregnancy reduces the risk.

Worked example

Vignette. A 58-year-old man with a bileaflet mechanical mitral valve stopped taking warfarin 2 weeks ago because of cost. He has 2 days of worsening dyspnea, crackles at both lung bases and a diastolic murmur. INR is 1.1. TTE shows a markedly elevated transmitral gradient, and fluoroscopy shows restricted leaflet motion. What is the most appropriate management?

Answer: Urgent treatment of obstructive mechanical valve thrombosis with fibrinolytic therapy or surgery; with NYHA class IV symptoms, surgery is favored if his surgical risk is low and expertise is available.

Reasoning: A subtherapeutic INR, a stenotic murmur, acute heart failure and restricted leaflet motion add up to obstructive left-sided mechanical valve thrombosis. The ACC/AHA table weighs surgical risk, clot size, NYHA class, recurrence and the possibility of pannus to choose between fibrinolysis and surgery. Restarting warfarin alone does not relieve an obstructed valve, and a DOAC is not an option for a mechanical valve. Once he recovers, his target INR is 3.0.

Key takeaways

PATCHES: Paravalvular leak, Anticoagulant bleeding, Thrombosis and thromboembolism, Conduction block, Hemolysis, Endocarditis, Structural deterioration and pannus.
Mechanical valves: lifelong warfarin; INR 2.5 for a low-risk bileaflet aortic valve, 3.0 for a mitral or higher-risk aortic valve; no DOACs.
Bioprosthetic valves: lifelong aspirin, with warfarin for 3–6 months after surgery as an option if bleeding risk is low; deterioration is faster in the young.
Obstructive mechanical valve thrombosis: fibrinolysis or surgery, chosen by surgical risk, clot size, NYHA class and possible pannus.
Prosthetic valve endocarditis: staphylococci dominate the first 2 months; use TEE; abscess or heart block means early surgery.
Paravalvular leak causes regurgitation and hemolysis; catheter-based closure is an option in selected patients without active infection.