When should warfarin be started in a patient with native (non‑replaced) valvular heart disease, such as rheumatic mitral stenosis, who has atrial fibrillation, a left‑atrial thrombus, or a prior systemic embolic event?

When to Start Warfarin in Native Valvular Heart Disease

Warfarin anticoagulation (target INR 2.5, range 2.0–3.0) must be started immediately in patients with native valvular heart disease who have atrial fibrillation, left atrial thrombus, or prior systemic embolism—these are absolute indications for anticoagulation. 1

Absolute Indications for Warfarin (Start Immediately)

Rheumatic Mitral Valve Disease with High-Risk Features

Start warfarin immediately if any of the following are present:

• Atrial fibrillation (regardless of mitral stenosis severity or left atrial size) 1
• Left atrial thrombus documented on echocardiography 1
• Prior systemic embolism or stroke, even if currently in sinus rhythm 1

These recommendations carry the highest level of evidence (Grade 1A), meaning warfarin is mandatory and not optional. 1

Rheumatic Mitral Valve Disease in Sinus Rhythm with Enlarged Left Atrium

Consider starting warfarin if:

• Left atrial diameter ≥55 mm on echocardiography, even without atrial fibrillation 1, 2
• Dense spontaneous echo contrast in the left atrium 1, 2

This carries a Grade 2C recommendation, meaning the evidence is weaker but warfarin is still suggested over no therapy. 1

Target INR and Monitoring Protocol

Initial dosing and monitoring:

• Start warfarin at 2–5 mg daily (avoid loading doses to minimize bleeding risk) 3
• Target INR: 2.5 (acceptable range 2.0–3.0) for all native valve disease 1, 4, 3
• Check INR weekly during initiation until therapeutic range achieved 5, 2, 3
• Once stable, check INR monthly 5, 2, 3
• Reassess renal and hepatic function at least annually 5, 2

Critical Contraindications and Pitfalls

Direct Oral Anticoagulants (DOACs) Are Prohibited

NOACs/DOACs (apixaban, rivaroxaban, dabigatran, edoxaban) are absolutely contraindicated in:

• Moderate-to-severe rheumatic mitral stenosis (Class III: Harm) 1, 5, 2
• All patients with rheumatic valve disease and atrial fibrillation 1, 4, 5

This prohibition exists because these patients were systematically excluded from all landmark DOAC trials, and one trial (RE-ALIGN) in mechanical valves showed excess thromboembolism and bleeding with dabigatran. 1, 5 While one small study suggested dabigatran might be comparable to warfarin in valvular AF 6, this contradicts all major guideline recommendations and should not guide practice. 1, 4, 5

Aspirin Alone Is Inadequate

Aspirin monotherapy is insufficient for stroke prevention in rheumatic valve disease with atrial fibrillation:

• Aspirin reduces stroke risk by only 19–22% versus placebo 4
• Warfarin reduces stroke risk by 62–64% 4
• One study showed 15 embolic events with aspirin versus only 3 with warfarin (when INR was therapeutic) 7

Do not add aspirin to warfarin routinely in rheumatic valve disease, as it increases bleeding without proven additional benefit unless a separate indication exists (e.g., coronary artery disease). 4

Special Situation: Pre-Procedural Management

Before Percutaneous Mitral Balloon Valvotomy (PMBV)

If left atrial thrombus is found on pre-procedure TEE:

• Postpone PMBV immediately 1
• Start warfarin with higher target INR 3.0 (range 2.5–3.5) 1
• Repeat TEE to document thrombus resolution (occurs in ~62% of cases within 6 months) 1
• If thrombus persists despite anticoagulation, do not perform PMBV 1

Predictors of thrombus resolution include NYHA class II or better, thrombus size <1.6 cm², and maintaining INR ≥2.5. 1

Patients Who Do NOT Require Warfarin

Warfarin is not indicated in:

• Rheumatic mitral valve disease in sinus rhythm with left atrial diameter <55 mm and no prior embolism or thrombus (Grade 2C suggests no antiplatelet or anticoagulation) 1
• Asymptomatic patent foramen ovale or atrial septal aneurysm without cryptogenic stroke 1
• Infective endocarditis (anticoagulation is contraindicated unless a separate indication exists) 1

Algorithmic Approach

Patient with native valvular heart disease
    ↓
Does patient have ANY of the following?
• Atrial fibrillation
• Left atrial thrombus on echo
• Prior systemic embolism/stroke
    ↓
YES → START WARFARIN IMMEDIATELY
       Target INR 2.5 (range 2.0-3.0)
       Check INR weekly until stable, then monthly
    ↓
NO → Is patient in sinus rhythm?
    ↓
YES → Measure left atrial diameter
    ↓
≥55 mm → CONSIDER WARFARIN (Grade 2C)
<55 mm → NO ANTICOAGULATION needed

Never use DOACs in rheumatic valve disease—warfarin is the only acceptable oral anticoagulant. 1, 4, 5, 2