Heart Health

Aspirin is not a substitute for anticoagulation

Applies whatever the score Always

Recommendationaf-aspirin-not-substituteNo one has reached this rule yet

Aspirin is not an alternative to anticoagulation

Clinical review

All reviewers

No clinician has signed off this rule yet. It reflects our reading of the guidelines cited below, which has not been independently checked.

What someone who reaches this rule is told

Word for word, as generated for the example person below. Figures in the text are theirs.

  • Not recommended for you

    Aspirin is not a substitute for a blood thinner in atrial fibrillation. If you are on aspirin instead of anticoagulation to prevent an AF stroke, that is worth questioning directly.

    Proven in trialsTrials counted real events, like heart attacks, strokes, or deaths, and this changed them.

    ACC/AHAClass 3: HarmLevel B-R
    Why, and the source

    This is the most consequential misunderstanding in AF care. Aspirin is markedly less effective than anticoagulation at preventing the clots that form in a fibrillating atrium, while still carrying meaningful bleeding risk — so it offers a fraction of the protection at much of the cost. The guideline explicitly recommends against aspirin, alone or with clopidogrel, as an alternative to anticoagulation in someone who is a candidate for it. Plenty of people are still on that arrangement from an earlier era.

    Where the guidelines stand

    ACC/AHA (US)

    2023 ACC/AHA/ACCP/HRS Guideline for the Diagnosis and Management of Atrial Fibrillation · Class 3: Harm · Level B-R

  • Strongly recommended

    If someone raises your bleeding risk as a reason not to anticoagulate, the right response is to fix what can be fixed rather than to skip the drug.

    Expert guidelinesOfficial guidelines recommend it, based on trials plus expert judgment.

    ACC/AHAClass 1Level B-NR
    Why, and the source

    Bleeding-risk scores are meant to flag modifiable contributors, not to identify people who should go without protection — and in most people the stroke risk being prevented outweighs the bleeding risk being added. The modifiable parts are concrete: get blood pressure to goal, cut alcohol, stop routine NSAIDs like ibuprofen and naproxen, review any interacting medication, and treat anaemia or a bleeding source if one exists. A genuinely uncontrolled bleeding problem is a different conversation, and left atrial appendage closure exists for it.

    Where the guidelines stand

    ACC/AHA (US)

    2023 ACC/AHA/ACCP/HRS Guideline for the Diagnosis and Management of Atrial Fibrillation · Class 1 · Level B-NR

An example person who reaches it

“Atrial fibrillation, blood thinner not yet discussed” — an illustrative profile, not a real user.

77-year-old womanBP 142/86 on medicationLDL 130diabetes, A1c 6.8%atrial fibrillation, diagnosed10-yr PREVENT-ASCVD 13.2%

Their path through atrial fibrillation

  1. Atrial fibrillation?Yes
  2. How was it found? (the evidence differs)Clinically diagnosed
  3. CHA2DS2-VASc — untreated stroke risk above ~2% a year?Yes (score >=2 men / >=3 women)
  4. Applies whatever the scoreAlways ← this rule
  5. Applies whatever the scoreAlways
  6. Applies whatever the scoreAlways

Where it sits

Asked after: Atrial fibrillation

Sources

Cited by the recommendations above.

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Runs in lib/engine/afPathway.ts as af-aspirin-not-substitute.