Introduction
Atrial fibrillation (AF) is the most common sustained cardiac arrhythmia encountered in clinical practice and is associated with an increased risk of ischaemic stroke and systemic thromboembolism. The irregular atrial rhythm can promote blood stasis, particularly in the left atrial appendage, increasing the potential for thrombus formation and subsequent embolization.
Stroke prevention is a central component of AF management. However, the risk of thromboembolism varies between individuals, making systematic risk assessment and appropriate selection of anticoagulation therapy essential. Healthcare professionals (HCPs) must consider clinical risk factors, bleeding risk, comorbidities, patient preferences and the suitability of available treatments when developing an individualised management plan.
1. Understanding the Relationship Between Atrial Fibrillation and Stroke
During AF, the atria contract in an uncoordinated manner, resulting in ineffective atrial mechanical function. This can promote blood stasis and thrombus formation, particularly in the left atrial appendage. If a thrombus enters the systemic circulation and reaches the cerebral arteries, it may cause an ischaemic stroke.
AF-related strokes can be associated with substantial morbidity and mortality. Consequently, identifying patients who may benefit from anticoagulation is a key clinical priority.
Importantly, the decision to initiate stroke-prevention therapy should be guided by the individual's thromboembolic risk rather than AF pattern alone. Patients with paroxysmal, persistent or permanent AF may all require assessment for anticoagulation.
2. Assessing Stroke Risk in Clinical Practice
Structured clinical risk assessment helps identify patients who may benefit from oral anticoagulation.
CHA₂DS₂-VASc score
The CHA₂DS₂-VASc score is widely used to estimate thromboembolic risk in patients with AF. It considers the following factors:
C - Congestive heart failure: History of heart failure or left ventricular dysfunction.
H - Hypertension: History of hypertension.
A₂ - Age 75 years or older: Assigned two points.
D - Diabetes mellitus: History of diabetes.
S₂ - Previous stroke, transient ischaemic attack (TIA) or systemic thromboembolism: Assigned two points.
V - Vascular disease: Such as previous myocardial infarction or peripheral arterial disease.
A - Age 65–74 years: Assigned one point.
Sc - Sex category: Female sex is included as a risk modifier in this scoring system.
A higher score generally indicates a greater risk of thromboembolic events. However, the score should support, rather than replace, clinical judgement and shared decision-making.
Guidelines differ in their preferred approach to risk scoring. The 2024 European Society of Cardiology (ESC) guideline recommends the CHA₂DS₂-VA score, which excludes sex category. Under this approach, oral anticoagulation is recommended for patients with a score of 2 or more and should be considered for those with a score of 1, following individual assessment.
HCPs should follow the applicable guideline and consider additional clinical factors that may influence stroke risk.
3. Balancing Stroke Risk Against Bleeding Risk
Although anticoagulation reduces thromboembolic risk, it can increase the risk of bleeding. Therefore, assessment should include factors such as:
Previous major bleeding or gastrointestinal haemorrhage.
Uncontrolled hypertension.
Renal or hepatic impairment.
Anaemia or thrombocytopenia.
Concomitant use of antiplatelet agents or non-steroidal anti-inflammatory drugs.
Excessive alcohol consumption and other potentially modifiable risks.
Tools such as the HAS-BLED score can help identify patients who require closer monitoring or modification of bleeding risk factors.
However, a high bleeding-risk score should not automatically exclude a patient from anticoagulation. Instead, it should prompt clinicians to address modifiable risk factors, review concomitant medicines and assess the overall balance of benefit and harm.
The final decision should incorporate clinical circumstances, patient preferences and the feasibility of safe long-term treatment.
4. Selecting an Appropriate Anticoagulation Strategy
Oral anticoagulants are the principal pharmacological option for reducing AF-related thromboembolic risk in eligible patients.
Direct oral anticoagulants
Direct oral anticoagulants (DOACs) include apixaban, dabigatran, edoxaban and rivaroxaban. For most eligible patients with AF, current guidelines favour DOACs over vitamin K antagonists because of their overall efficacy and safety profile.
The choice of agent and dose should account for renal function, age, body weight where relevant, potential drug interactions, adherence, affordability and other patient-specific factors.
Vitamin K antagonists
Warfarin remains an important treatment option for selected patients, particularly those with mechanical heart valves or moderate-to-severe rheumatic mitral stenosis. Its use requires monitoring of the international normalised ratio (INR) and appropriate dose adjustment.
Important prescribing considerations
Before initiating anticoagulation, HCPs should confirm the indication, review contraindications and assess relevant baseline parameters, including renal function and potential drug interactions.
Anticoagulant dosing should follow approved prescribing information and applicable clinical guidance. Empirical dose reduction without an appropriate indication may compromise stroke prevention.
Aspirin, alone or combined with clopidogrel, is not a suitable substitute for oral anticoagulation for AF-related stroke prevention in patients who are otherwise eligible for anticoagulation and have no separate indication for antiplatelet therapy.
5. Why Regular Reassessment Matters
AF management is an ongoing process rather than a one-time treatment decision. Stroke risk, bleeding risk, renal function, comorbidities and patient preferences may change over time.
Regular reassessment should include:
Reviewing stroke-risk factors and whether anticoagulation remains indicated.
Evaluating bleeding events and addressing modifiable risks.
Monitoring renal function and other parameters relevant to drug selection and dosing.
Reviewing adherence, tolerability and potential drug interactions.
Reassessing concomitant antiplatelet therapy and other medicines.
Discussing changes in treatment options and patient preferences.
Patients should also receive clear counselling on adherence, potential bleeding symptoms and when to seek urgent medical attention.
6. An Individualised Approach to Stroke Prevention
Effective stroke prevention requires more than calculating a risk score. Clinical decisions should integrate guideline recommendations with individual patient characteristics, comorbidities, bleeding risks and preferences.
For patients in whom long-term anticoagulation is contraindicated because of a non-reversible cause, left atrial appendage occlusion may be considered in selected cases following specialist assessment. This is not a routine replacement for anticoagulation and requires careful evaluation of the potential benefits and limitations.
A multidisciplinary approach involving cardiologists, primary care clinicians, pharmacists and other relevant healthcare professionals can support appropriate prescribing, medication adherence and long-term follow-up.
Conclusion
Atrial fibrillation is an important risk factor for ischaemic stroke, but appropriate risk assessment and evidence-based anticoagulation can substantially reduce thromboembolic risk in eligible patients.
In clinical practice, HCPs should use validated risk-assessment tools, evaluate bleeding risks without relying on bleeding scores in isolation, select anticoagulation according to patient-specific factors and reassess treatment regularly.
A structured, individualised and guideline-informed approach is central to safer anticoagulation and effective stroke prevention in patients with AF.