Introduction
Patient with atrial fibrillation and not anticoagulated. The first step consists of applying the CHA₂DS₂-VA score, a variation of CHA₂DS₂-VASc that does not include sex as a variable, while maintaining similar predictive value, with potential superior performance in individuals over 75 years of age.
CHA₂DS₂-VA score
Points are assigned as follows: 1 point for heart failure or reduced ejection fraction, arterial hypertension, age between 65 and 74 years, diabetes mellitus and vascular disease — whether peripheral, coronary or aortic. Two points are assigned for age 75 years or older and for previous history of stroke, transient ischaemic attack or embolism.
Decision according to the score
If the patient has 2 or more points, oral anticoagulation is indicated. In cases with only 1 point, the decision should be individualised, considering thrombotic and bleeding risk, as well as the patient’s preference. If the score is 0, anticoagulation is not recommended.
Contraindications to anticoagulation
Before starting anticoagulant therapy, it is essential to assess for absolute or relative contraindications. Absolute contraindications include large oesophageal varices, severe thrombocytopenia below 50,000 platelets per microlitre, hypersensitivity to an anticoagulant drug and major surgery within the previous 72 hours with high bleeding risk. Relative contraindications include previous intracranial haemorrhage, recent extracranial bleeding with no identified cause, documented peptic ulcer within the previous 3 months, history of falls in patients with high bleeding risk, dementia or inability to adhere to treatment, and chronic harmful alcohol use.
Bleeding risk stratification
In these cases, the HAS-BLED score should be considered to estimate bleeding risk. Although it should not be used in isolation to decide on anticoagulation, it helps identify modifiable bleeding risk factors.
Therapeutic option
In the absence of contraindications, oral anticoagulation with a NOAC — non-vitamin K antagonist oral anticoagulants — is the recommended choice. Antiplatelet monotherapy is not effective for stroke prevention in atrial fibrillation, and the combination of anticoagulants and antiplatelet agents should be avoided, unless there is another formal indication for this combination.
Choice of NOAC
The choice of NOAC may be guided by specific clinical characteristics. In patients with high thrombotic risk and low bleeding risk, dabigatran has greater efficacy in reducing ischaemic stroke. When bleeding risk is high, drugs such as apixaban, reduced-dose dabigatran or edoxaban should be considered, as they have a lower risk of major bleeding. In moderate to severe renal impairment, apixaban, edoxaban or rivaroxaban may be used with dose adjustment. If there is a history of gastrointestinal bleeding or peptic ulcer disease, apixaban and edoxaban are preferred because of their greater gastrointestinal safety. For secondary prevention after stroke, rivaroxaban and apixaban are options with good evidence. For patients who prefer once-daily dosing, rivaroxaban or edoxaban are the preferred options.
When to avoid NOACs
In situations where there are contraindications to NOAC use, such as mechanical heart valves, moderate to severe rheumatic mitral stenosis, pregnancy, antiphospholipid syndrome, advanced liver disease — especially Child C stage — or renal disease with creatinine clearance below 15 mL/min, vitamin K antagonists should be considered or the patient should be referred for specialist support.
Dose adjustment and interactions
Finally, doses should be adjusted according to renal function, age, weight and potential drug interactions. Drugs such as verapamil, amiodarone, dronedarone, rifampicin, azole antifungals, antiepileptic drugs and immunosuppressants may interfere with NOAC activity and should be carefully assessed before initiation. For safe and effective use, it is essential to consult interaction tables and adjust doses individually.
Conclusion
Thus, anticoagulation in atrial fibrillation should always be based on a systematic assessment of thrombotic and bleeding risk, with treatment adapted to the clinical context and the patient’s preferences.
