Key Facts

AF is characterised by rapid, irregular atrial activation replacing normal sinus rhythm. It is a major modifiable risk factor for ischaemic stroke. Primary care is central to detection, risk stratification, anticoagulation, and rate/rhythm control.

Epidemiology

• Prevalence: 2% of UK population (approximately 1.4 million people)
• Prevalence rises steeply with age: 0.5% at age 50-59; >10% at age >75
• Lifetime risk of developing AF: 25% for those aged ≥40
• AF-related strokes tend to be more severe and carry higher mortality

Aetiology

• Cardiovascular: hypertension (most common), valvular heart disease (especially mitral), heart failure, coronary artery disease, cardiomyopathy
• Non-cardiovascular: hyperthyroidism, acute infection/sepsis, alcohol excess ('holiday heart'), PE, post-cardiac surgery, obesity, OSA
• Lone AF: no identifiable cause, typically younger patients (<60 years)

Pathophysiology

• Multiple re-entrant circuits and/or rapid focal ectopic firing (commonly from pulmonary veins) cause chaotic atrial depolarisation at 350-600 bpm
• Loss of coordinated atrial contraction leads to irregular ventricular response and loss of atrial 'kick' (15-25% of cardiac output)
• Atrial stasis predisposes to thrombus formation, particularly in the left atrial appendage
• Electrical and structural remodelling ('AF begets AF') promotes persistence

Symptoms

• Palpitations (irregular, rapid heartbeat)
• Breathlessness on exertion
• Fatigue and reduced exercise tolerance
• Dizziness or light-headedness
• Chest tightness
• Many patients are asymptomatic (detected incidentally)

Classification

• Paroxysmal: self-terminating within 7 days (usually <48 hours)
• Persistent: sustained >7 days; requires cardioversion
• Long-standing persistent: continuous >12 months
• Permanent: accepted by patient and clinician; rhythm control not pursued

Presentation as Complication

• Ischaemic stroke or TIA (first presentation in some cases)
• Acute heart failure (fast AF with decompensation)
• Systemic embolisation

Red Flags

• Haemodynamic instability (hypotension, syncope) — emergency DC cardioversion
• Acute stroke symptoms — thrombolysis/thrombectomy pathway
• Very fast ventricular rate (>150 bpm) with chest pain — consider WPW or urgent rate control
• Signs of heart failure — urgent assessment and treatment
• New AF with thyrotoxicosis — treat thyroid disease

Bedside

• Pulse palpation: irregularly irregular rhythm
• 12-lead ECG: absent P waves, irregular R-R intervals, narrow QRS complex (unless bundle branch block)
• Blood pressure
• Heart rate

Bloods

• TFTs: exclude hyperthyroidism (mandatory in new AF)
• FBC: exclude anaemia
• U&Es: baseline renal function for DOAC dosing
• LFTs: baseline for anticoagulation
• Coagulation screen: baseline
• BNP/NT-proBNP: if heart failure suspected

Imaging

• Echocardiogram: assess LV function, valvular disease, left atrial size — recommended for all patients with AF (NICE NG196)
• CXR: if heart failure suspected

Special Tests

• 24-hour or 7-day Holter monitor: if paroxysmal AF suspected but not captured on ECG
• Event recorder or implantable loop recorder: for infrequent episodes
• CHA₂DS₂-VASc score: stroke risk assessment
• HAS-BLED score: bleeding risk assessment (does not contraindicate anticoagulation but identifies modifiable risk factors)
• Ambulatory ECG: assess rate control adequacy

Non-pharmacological

• Lifestyle modification: weight loss (LEGACY trial showed AF burden reduction with 10% weight loss), alcohol reduction, treat OSA, exercise
• Patient education about AF, stroke risk, and anticoagulation
• Pulse self-monitoring

Pharmacological

Stroke prevention (NICE NG196):

• Assess stroke risk with CHA₂DS₂-VASc:
  • Score 0 (men) or 1 (women): no anticoagulation
  • Score 1 (men): consider anticoagulation
  • Score ≥2 (men) or ≥3 (women): offer anticoagulation
• First-line: DOAC — apixaban 5mg BD (reduced to 2.5mg BD if ≥2 of: age ≥80, weight ≤60kg, creatinine ≥133 μmol/L) or rivaroxaban 20mg OD with food (15mg if CrCl 15-49 mL/min) or edoxaban 60mg OD (30mg if CrCl 15-50 mL/min, weight ≤60kg, or certain P-gp inhibitors) or dabigatran 150mg BD (110mg BD if age ≥80 or on verapamil)
• Warfarin: if DOAC contraindicated (mechanical heart valve, moderate-severe mitral stenosis); target INR 2.0-3.0
• Do NOT offer aspirin as sole stroke prevention in AF

Rate control (first-line for most patients, NICE NG196):

• Bisoprolol 2.5-10mg OD (or other beta-blocker)
• Diltiazem 120-360mg daily (non-dihydropyridine CCB; avoid with beta-blocker)
• Digoxin: add if monotherapy inadequate or in sedentary patients; loading dose 500mcg then 125-250mcg OD
• Target resting heart rate <110 bpm (lenient) initially; <80 bpm (strict) if persistent symptoms

Rhythm control (consider if symptomatic despite rate control, young, first episode, or patient preference):

• Flecainide 100-150mg BD (only if no structural heart disease; 'pill-in-the-pocket' for paroxysmal AF)
• Amiodarone 200mg TDS for 1 week, 200mg BD for 1 week, then 200mg OD maintenance (significant side effects: thyroid, pulmonary fibrosis, liver, photosensitivity)
• DC cardioversion: for persistent AF; pre-anticoagulate for ≥3 weeks or exclude LAA thrombus with TOE

Catheter ablation:

• Pulmonary vein isolation for symptomatic paroxysmal or persistent AF refractory to ≥1 antiarrhythmic drug (NICE NG196)
• CASTLE-AF trial: improved outcomes in AF with heart failure

Surgical

• Left atrial appendage occlusion (Watchman device): if anticoagulation contraindicated
• Maze procedure: during concomitant cardiac surgery

Referral Criteria

• Haemodynamically unstable AF: emergency admission
• Suspected underlying structural heart disease: cardiology referral + echo
• Considering rhythm control strategy: cardiology
• AF in WPW (delta wave on ECG): urgent cardiology (avoid AV nodal blocking agents)
• Young patients (<50) with lone AF: cardiology
• Anticoagulation in challenging cases (renal impairment, bleeding history): haematology/cardiology

• AF increases stroke risk 5-fold; anticoagulation reduces this by 60-70% (DOACs) or 65% (warfarin)
• Heart failure develops in approximately 20-30% of AF patients over time
• Mortality: AF associated with 1.5-2 fold increased all-cause mortality
• Catheter ablation: freedom from AF at 1 year in 60-80% (paroxysmal) and 50-60% (persistent); may require repeat procedures
• Anticoagulation-related major bleeding: approximately 2-3% per year with DOACs (lower intracranial haemorrhage rate compared to warfarin)
• Rate control achieves adequate symptom control in >80% of patients

CHA₂DS₂-VASc Score

Landmark DOAC Trials in AF