AHA Guidelines for Stroke Prevention in Atrial Fibrillation

Atrial fibrillation (AF) is the commonest sustained arrhythmia in older people and is a major cause of cardioembolic stroke, heart failure, and death.

Stroke in AF arises mainly from thrombus in the left atrial appendage (LAA) — hence the anatomical basis of all preventive strategies.

The absolute stroke reduction from oral anticoagulation is greatest in the elderly, because baseline stroke risk rises steeply with age and outweighs the bleeding risk.

All patients with AF must be routinely scored for stroke risk — the recommended tool is the CHA2DS2-VASc score.

Anticoagulation is a Class I recommendation at CHA2DS2-VASc ≥2 in men and ≥3 in women. It should be considered at a score of 1 in men and 2 in women.

All patients over 75 with AF should therefore be anticoagulated unless there is a major contraindication.

Bleeding risk must be assessed in parallel using HAS-BLED, ORBIT, ATRIA, HEMORR2HAGES, or the biomarker-based ABC bleeding score.

A high bleeding score is not a reason to withhold anticoagulation — it identifies modifiable risk factors (uncontrolled BP, labile INR, alcohol, concomitant NSAIDs/antiplatelets) that should be corrected.

In non-valvular AF, DOACs are recommended over warfarin (Class I) in patients without contraindications.

Warfarin is mandatory in moderate-to-severe mitral stenosis and in mechanical prosthetic heart valves (Class I) — DOACs are contraindicated and less effective in these groups.

Warfarin efficacy depends on time in therapeutic range (TTR) with a target INR 2–3; the higher the TTR, the lower the risk of both stroke and bleeding.

Antiplatelet therapy is inferior — a meta-analysis of nine trials showed VKA superior to aspirin with a 39% relative risk reduction, and ACTIVE-W showed anticoagulation superior to aspirin–clopidogrel (RRR 40%).

BAFTA (age ≥75): warfarin (INR 2–3) reduced stroke, systemic embolism, and intracranial bleeding by 52% versus aspirin 75 mg, with no difference in major haemorrhage.

RE-LY: dabigatran 150 mg BD reduced stroke/systemic embolism by 35%; 110 mg BD was non-inferior with 20% less bleeding.

ARISTOTLE: apixaban 5 mg BD reduced stroke/systemic embolism by 21%, major bleeding by 31%, and death by 11%.

ENGAGE AF-TIMI 48: edoxaban 60 mg OD had similar efficacy with 20% less major bleeding. ROCKET-AF: rivaroxaban 20 mg OD had similar efficacy with less intracranial and life-threatening bleeding.

AVERROES: apixaban was superior to aspirin in patients unsuitable for warfarin, with an acceptable safety profile.

In patients >75 years, DOACs as a class were superior to warfarin in both efficacy and safety. Apixaban had the lowest risk of major bleeding, and apixaban, edoxaban, and dabigatran had lower rates of intracranial haemorrhage than rivaroxaban or warfarin. NON-PHARMACOLOGICAL OPTIONS AND SPECIAL SITUATIONS

Percutaneous LAA occlusion (WATCHMAN) is an option for patients with high stroke risk and a non-reversible contraindication to long-term anticoagulation — for example prior intracranial haemorrhage on OAC, or recurrent embolic stroke despite adequate anticoagulation.

Surgical LAA excision or exclusion should be considered in AF patients undergoing cardiac surgery; concomitant surgical AF ablation reduces stroke and has a Class I indication.

After cardioembolic stroke, delay starting anticoagulation for about 2 weeks because early benefit is offset by haemorrhagic transformation — but start immediately after TIA or minor stroke.

Falls risk and dementia are frequently used as inappropriate reasons to withhold anticoagulation; only end-stage dementia clearly tips the balance against treatment.