Atrial fibrillation: predisposing factors and considerations in older people
THE CONTEXT
Atrial fibrillation (AF) can accompany structural heart disease or occur in structurally normal hearts. Older age adds specific presentation and anticoagulation considerations.
Predisposing factors and lone AF
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Many forms of heart disease can present with AF, particularly conditions associated with atrial enlargement or dilatation.
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Common causes include alcohol excess, obesity, hypertension, coronary artery disease, hyperthyroidism and chronic lung disease. Multiple predisposing factors may coexist.
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About 50% of patients with paroxysmal AF and 20% with persistent or permanent AF have structurally normal hearts; this is termed lone atrial fibrillation.
Presentation and outcomes in older people
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AF prevalence reaches 9% in people over 80 years. It may be asymptomatic but is often accompanied by diastolic heart failure.
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AF may be the dominant manifestation of otherwise silent or occult hyperthyroidism.
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Recurrence after cardioversion is common, occurring in approximately 70% at one year.
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AF is an important cause of cerebral embolism and is found in 15% of all stroke patients and 2%–8% of patients with transient ischaemic attacks.
Anticoagulation considerations
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Both thromboembolism risk and anticoagulation hazards increase with age. Increased comorbidity, particularly cognitive impairment and falls, contributes to anticoagulation hazards.
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Direct oral anticoagulants are alternatives to warfarin. They require no blood monitoring, have fewer drug interactions, and use fixed dosing that may aid adherence.
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Renal impairment affects dosing. The passage specifies reducing apixaban from 5 mg twice daily to 2.5 mg twice daily when at least two criteria apply: estimated glomerular filtration rate below 30 mL/min/1.73 m², age at least 80 years, or weight no more than 60 kg.
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For warfarin-treated patients over 75 years, the International Normalised Ratio should be maintained below 3.0 because of increased intracranial haemorrhage risk.