Collaborative Care PLLC · Washington

Atrial fibrillation: deciding together about stroke prevention

Work through two standard risk scores, then compare what each treatment option would be expected to do for a person with those scores — in plain numbers you can talk through together, out of 100 similar people over one year.

For education and shared decision-making only. Not a substitute for clinical judgment. Verify dosing, eligibility, renal function, interactions, and current guideline recommendations before prescribing. No information you enter here is saved or sent anywhere — it stays on this screen.

Step 1 · Risk factors

First, the person's risk without treatment

Tap each factor that applies. Age is shared by both scores, so set it once. Everything below updates as you go.

Age band

Counts toward CHA₂DS₂-VASc (age 65–74: +1 · 75+: +2). HAS-BLED's “elderly” point is defined as age over 65, so it is added for the 66–74 and 75+ bands but not at exactly 65 — that is why 65 has its own button.

Stroke risk — CHA₂DS₂-VASc

Estimated stroke risk without anticoagulation:
0% per year

0
of 9 points

Bleeding risk — HAS-BLED

Major bleeds in the original cohort:
1.13 per 100 people per year

0
of 9 points
HAS-BLED ≥ 3 — high bleeding risk. Treat this as a prompt, not a stop sign: address the modifiable factors (blood pressure, alcohol, NSAIDs / antiplatelet drugs, INR stability), correct what can be corrected, and follow up more closely. A high HAS-BLED score on its own is not a reason to withhold anticoagulation from someone at high stroke risk.

Step 2 · Compare treatments

What each option changes

Estimated events per year for a person with the scores above. Tap any row to see it as a picture of 100 people below. “Simple net difference” = strokes prevented minus extra major bleeds, per 100 people per year, compared with no treatment — strokes and bleeds counted equally (see how these numbers are built).

Treatment Stroke
% / year		 Major bleed
% / year		 Simple net
difference		 Stroke vs bleed

Aspirin, alone or with clopidogrel, is included because patients often ask about it. The 2023 ACC/AHA/ACCP/HRS atrial fibrillation guideline states that aspirin either alone or combined with clopidogrel, as an alternative to anticoagulation, is not recommended to reduce stroke risk (Class 3: Harm), and that direct oral anticoagulants are recommended over warfarin for eligible patients without moderate–severe rheumatic mitral stenosis or a mechanical valve.

Step 3 · See it as people

Out of 100 similar people over one year

No antithrombotic therapy

0
would have a stroke
(0% per year)
1
would have a major bleed
(1.1% per year)
99
would have neither
in that year
Stroke Major bleed Neither event

How to read this: each figure is one person. Percentages are rounded to the nearest whole person, so a risk under 0.5% shows as zero figures even though the risk is not zero — the exact percentages are shown above the picture. A person can in principle have both a stroke and a bleed in the same year; the picture shows expected counts for each event separately, so the “neither” count is 100 minus the two rounded counts.

Transparency

How these numbers are built

  • Baseline stroke risk comes from the CHA₂DS₂-VASc score using the adjusted annual stroke rates published with the score (Lip et al., 2010): score 0 → 0%, 1 → 1.3%, 2 → 2.2%, 3 → 3.2%, 4 → 4.0%, 5 → 6.7%, 6 → 9.8%, 7 → 9.6%, 8 → 6.7%, 9 → 15.2% per year. Rates do not rise perfectly smoothly at scores 7–8 in the original cohort because few patients had those scores — treat high-score figures as approximate. Observed rates vary between populations.
  • Treatment effects on stroke are applied as relative risks to that baseline: warfarin 0.36 and antiplatelet therapy 0.78 vs no treatment (Hart et al. meta-analysis, 2007); aspirin + clopidogrel 0.72 vs aspirin alone for stroke (ACTIVE A, 2009). Each direct oral anticoagulant is then applied relative to warfarin using its pivotal trial: dabigatran 110 mg 0.91 and 150 mg 0.66 (RE-LY), rivaroxaban 0.88 (ROCKET AF, intention-to-treat), apixaban 0.79 (ARISTOTLE), edoxaban 60 mg 0.79 and 30 mg 1.07 (ENGAGE AF–TIMI 48).
  • Major bleeding is anchored to the person's HAS-BLED rate from the original cohort (Pisters et al., 2010: 0 → 1.13, 1 → 1.02, 2 → 1.88, 3 → 3.74, 4 → 8.70, 5 → 12.5 bleeds per 100 patient-years; above 5 the anchor is held at 12.5 because the original cohort had too few such patients to estimate reliably). That rate is used as the warfarin anchor. Other treatments are scaled from it: aspirin ×0.59 (warfarin increased major extracranial hemorrhage by about 70% vs aspirin in the Hart meta-analysis), aspirin + clopidogrel ×1.57 vs aspirin (ACTIVE A), and each DOAC by its trial major-bleeding ratio vs warfarin (dabigatran 110 mg 0.80, 150 mg 0.93; rivaroxaban 1.04; apixaban 0.69; edoxaban 60 mg 0.80, 30 mg 0.47). “No treatment” bleeding is the one figure here that no trial measures directly for this score: it is set at 45% of the warfarin anchor as a clearly labelled simplifying assumption, so that every drug shows a bleeding rate above the untreated background (major bleeding does occur with no antithrombotic drug at all, and in the lower-risk trial populations pooled by Hart et al. the absolute increase on therapy was small, ≤0.3%/year). These are estimates for conversation, not predictions for an individual.
  • Simple net difference is our own plain calculation, shown so the trade-off is visible: (baseline stroke % − treatment stroke %) − (treatment bleed % − no-treatment bleed %), per 100 people per year. It weights one stroke and one major bleed equally and is not the weighted net-clinical-benefit figure used in some research, which counts intracranial hemorrhage more heavily.
  • Doses shown are the standard trial doses. Several of these drugs have reduced-dose criteria, renal restrictions, or are not the locally approved dose for every patient — check the current label and guideline before prescribing.

Sources

References

  1. Lip GYH, Nieuwlaat R, Pisters R, Lane DA, Crijns HJGM. Refining clinical risk stratification for predicting stroke and thromboembolism in atrial fibrillation using a novel risk factor-based approach: the Euro Heart Survey on atrial fibrillation (CHA₂DS₂-VASc). Chest. 2010;137(2):263–272. Score and adjusted stroke-rate table summarised at PMC4555351.
  2. Pisters R, Lane DA, Nieuwlaat R, de Vos CB, Crijns HJGM, Lip GYH. A novel user-friendly score (HAS-BLED) to assess 1-year risk of major bleeding in patients with atrial fibrillation: the Euro Heart Survey. Chest. 2010;138(5):1093–1100. Bleeds per 100 patient-years by score, summarised at PMC7753878 and UC San Diego Health anticoagulation guidelines.
  3. Hart RG, Pearce LA, Aguilar MI. Meta-analysis: antithrombotic therapy to prevent stroke in patients who have nonvalvular atrial fibrillation. Ann Intern Med. 2007;146(12):857–867. (Warfarin −64% and antiplatelet therapy −22% for stroke vs control; absolute increase in major extracranial hemorrhage ≤0.3%/year.)
  4. Connolly SJ, et al.; ACTIVE Writing Group. Effect of clopidogrel added to aspirin in patients with atrial fibrillation (ACTIVE A). N Engl J Med. 2009;360:2066–2078. (Stroke relative risk 0.72 and major bleeding relative risk 1.57 for aspirin + clopidogrel vs aspirin alone.)
  5. Connolly SJ, et al. Dabigatran versus warfarin in patients with atrial fibrillation (RE-LY). N Engl J Med. 2009;361:1139–1151.
  6. Patel MR, et al. Rivaroxaban versus warfarin in nonvalvular atrial fibrillation (ROCKET AF). N Engl J Med. 2011;365:883–891.
  7. Granger CB, et al. Apixaban versus warfarin in patients with atrial fibrillation (ARISTOTLE). N Engl J Med. 2011;365:981–992.
  8. Giugliano RP, et al. Edoxaban versus warfarin in patients with atrial fibrillation (ENGAGE AF–TIMI 48). N Engl J Med. 2013;369:2093–2104. Trial event rates and ratios for references 5–8 are tabulated at PMC4897006.
  9. Joglar JA, et al. 2023 ACC/AHA/ACCP/HRS Guideline for the Diagnosis and Management of Atrial Fibrillation. Circulation. 2024;149:e1–e156. (DOACs recommended over warfarin for eligible patients; aspirin alone or with clopidogrel as an alternative to anticoagulation is not recommended — Class 3: Harm.) Overview at PMC11344489.