Mechanical Prosthetic Heart Valve and Moderate Mitral Stenosis Require Warfarin
Among the factors listed, a mechanical prosthetic heart valve and moderate mitral stenosis are absolute indications for warfarin rather than direct oral anticoagulants (DOACs) in patients with atrial fibrillation requiring secondary stroke prevention. 1
Definitive Contraindications to DOACs
Mechanical Prosthetic Heart Valve
- Warfarin is mandatory for all patients with mechanical prosthetic heart valves, regardless of valve position or type. 1
- DOACs are explicitly contraindicated (Class III: Harm) in this population; dabigatran was studied in the RE-ALIGN trial and showed increased thromboembolic events and major bleeding, leading to early trial termination. 1
- Target INR is 2.5 (range 2.0–3.0) for bileaflet valves in the aortic position, and 3.0 (range 2.5–3.5) for tilting disk or bileaflet valves in the mitral position. 2
Moderate-to-Severe Mitral Stenosis
- Patients with moderate-to-severe mitral stenosis (typically rheumatic) must receive warfarin, not DOACs, for stroke prevention in atrial fibrillation. 1
- This exclusion applies whether the patient is in sinus rhythm or atrial fibrillation. 3, 4
- Target INR is 2.5 (range 2.0–3.0). 3, 4
- All landmark DOAC trials systematically excluded patients with moderate-to-severe mitral stenosis, leaving no evidence base for their use. 5, 6, 7
Factors That Do NOT Require Warfarin
Pregnancy
- Warfarin is absolutely contraindicated in pregnancy due to teratogenic effects (fetal warfarin syndrome with nasal hypoplasia and stippled epiphyses in the first trimester) and risk of fetal hemorrhage. 8
- DOACs are also contraindicated in pregnancy due to unknown teratogenic potential and lack of safety data. 8
- For pregnant patients requiring anticoagulation (e.g., mechanical valve), adjusted-dose unfractionated heparin or low-molecular-weight heparin throughout gestation is recommended. 8
- Pregnancy does not "require warfarin"—it prohibits warfarin entirely.
BMI of 35
- Obesity with BMI 35 does not contraindicate DOAC use or mandate warfarin. 8
- DOAC trials included patients across a wide BMI range without safety concerns at this level of obesity. 8
- DOACs remain preferred over warfarin in DOAC-eligible patients regardless of this BMI. 1
End-Stage Renal Disease (ESRD)
- ESRD or dialysis (CrCl <15 mL/min) does not absolutely require warfarin, though the evidence for DOACs is limited in this population. 1
- The 2019 AHA/ACC/HRS guideline states it "might be reasonable" (Class IIb) to prescribe either warfarin (INR 2.0–3.0) or apixaban in ESRD patients with AF. 1
- Warfarin remains the better-studied option, but apixaban has emerging data supporting its use. 8
- This is a clinical judgment call, not an absolute warfarin requirement.
Warfarin Monitoring Requirements
When warfarin is prescribed for mechanical valves or mitral stenosis:
- Check INR weekly during initiation until therapeutic range is achieved. 1
- Once stable, check INR monthly. 1
- Reassess renal and hepatic function at least annually. 1
- Strive for high time-in-therapeutic-range (TTR) to maximize efficacy and minimize bleeding risk. 4
Common Pitfalls to Avoid
- Do not use DOACs in bioprosthetic valves placed for rheumatic mitral stenosis—the underlying rheumatic pathology maintains high thromboembolic risk requiring warfarin. 4
- Mild mitral stenosis is not an absolute contraindication to DOACs, though more evidence is needed; moderate-to-severe stenosis is the threshold. 6, 7
- Bioprosthetic valves in other positions (not for rheumatic disease) may use DOACs after the first 3 months post-implantation. 4