Key Facts

Atrial fibrillation (AF) is the most common sustained cardiac arrhythmia, characterised by disorganised atrial electrical activity leading to irregular ventricular response. It is a major cause of stroke and heart failure.

Epidemiology

• ~1.4 million people in the UK (~2% of general population)
• Prevalence: <1% in <60 years; ~10% in >75 years
• Lifetime risk: ~25% for those >40 years
• AF-related strokes are more severe with higher mortality than non-AF strokes
• ~25% of all ischaemic strokes are AF-related

Aetiology

• Cardiac: hypertension (most common), valvular heart disease (especially mitral), heart failure, IHD, cardiomyopathy, post-cardiac surgery
• Non-cardiac: thyrotoxicosis, alcohol excess ('holiday heart'), PE, pneumonia, sepsis, caffeine, electrolyte abnormalities, obesity, OSA
• Lone AF: no identifiable cause (~10-15%, usually younger patients)

Pathophysiology

• Multiple re-entrant wavelets within the atria
• Ectopic foci, particularly from pulmonary veins, initiate and maintain AF
• Atrial remodelling ('AF begets AF'): electrical and structural changes promote persistence
• Loss of organised atrial contraction → loss of atrial 'kick' (reduces CO by ~15-25%)
• Stasis in left atrial appendage → thrombus formation → stroke risk

Classification

• Paroxysmal: episodes self-terminate within 7 days (usually <48 hours)
• Persistent: sustained >7 days, requires intervention for termination
• Long-standing persistent: continuous AF for >12 months, rhythm control strategy adopted
• Permanent: AF accepted; no further rhythm control attempts

Symptoms

• Palpitations (most common)
• Dyspnoea
• Fatigue and exercise intolerance
• Dizziness or lightheadedness
• Chest pain/discomfort
• May be asymptomatic (~30%)

Signs

• Irregularly irregular pulse
• Variable intensity S1
• Pulse deficit (apical rate > radial rate)
• Features of underlying cause (thyrotoxicosis, valvular disease)

Red Flags

• Haemodynamic instability (synchronised DC cardioversion)
• Very rapid rate >150 bpm with pre-excited AF (WPW) — avoid AV nodal blocking drugs
• Stroke or TIA symptoms
• Acute heart failure/pulmonary oedema

Bedside

• ECG: irregularly irregular, absent P waves, fibrillatory baseline, variable RR intervals
• Pulse check: irregularly irregular pulse

Bloods

• TFTs: thyrotoxicosis
• U&Es: electrolyte abnormalities (K⁺, Mg²⁺)
• FBC: anaemia, infection
• LFTs: alcohol, hepatic congestion
• Coagulation screen: baseline before anticoagulation
• eGFR/CrCl: dose adjustment for DOACs

Imaging

• Echocardiography: LV function, valvular disease, LA size, LVH
• Transoesophageal echo (TOE): exclude LA appendage thrombus before cardioversion if AF >48h and not anticoagulated for ≥3 weeks

Special Tests

• 24h/48h/7-day Holter monitor: paroxysmal AF detection
• Event recorder/implantable loop recorder: if suspected paroxysmal AF not captured
• CHA₂DS₂-VASc score: stroke risk assessment
• ORBIT score: bleeding risk assessment (NICE preferred over HAS-BLED)

Non-pharmacological

• Address modifiable risk factors: weight loss, alcohol reduction, OSA treatment, exercise
• Patient education about stroke risk and anticoagulation

Pharmacological

1. Anticoagulation (stroke prevention):

• Assess CHA₂DS₂-VASc: anticoagulate if ≥2 (men) or ≥3 (women)
• Consider anticoagulation if score = 1 (men) or 2 (women)
• DOAC preferred (NICE NG196): apixaban 5mg BD, rivaroxaban 20mg OD, edoxaban 60mg OD, dabigatran 150mg BD
• Dose reduction: apixaban 2.5mg BD if ≥2 of: age ≥80, weight ≤60kg, Cr ≥133
• Warfarin if DOAC contraindicated or mechanical heart valve (target INR 2-3)
• Do NOT use aspirin alone for stroke prevention in AF
• Left atrial appendage occlusion (Watchman device): if anticoagulation contraindicated

2. Rate control (first-line per NICE):

• Beta-blocker: bisoprolol 2.5-10mg OD (first-line)
• Rate-limiting CCB: diltiazem 120-360mg MR OD (not with beta-blocker if HFrEF)
• Digoxin: add-on if monotherapy insufficient; or first-line if sedentary/HF
• Target resting HR <110 bpm (RACE-II trial: lenient rate control non-inferior to strict)

3. Rhythm control:

• Consider if symptomatic despite adequate rate control, or as first-line if young/paroxysmal/reversible cause
• DC cardioversion: if AF <48h or adequately anticoagulated ≥3 weeks (or TOE excludes thrombus)
• Pharmacological cardioversion: flecainide 300mg PO (pill-in-pocket) or IV (if no structural heart disease); amiodarone IV if structural heart disease or HF
• Maintenance antiarrhythmic: flecainide 50-150mg BD, dronedarone 400mg BD, amiodarone 200mg OD
• Continue anticoagulation for ≥4 weeks post-cardioversion (indefinitely if risk factors persist)

Landmark trials:

• AFFIRM/RACE: rate control non-inferior to rhythm control (older drugs)
• EAST-AFNET 4: early rhythm control may improve outcomes
• RE-LY (dabigatran), ROCKET-AF (rivaroxaban), ARISTOTLE (apixaban), ENGAGE AF (edoxaban): DOACs vs warfarin

Surgical/Interventional

• Catheter ablation (pulmonary vein isolation): for paroxysmal/persistent AF refractory to drugs
  • Success rate: ~70-80% for paroxysmal, ~50-60% for persistent
  • CASTLE-AF: ablation improved outcomes in AF with HFrEF
• Surgical ablation (Maze procedure): at time of cardiac surgery
• AV node ablation + permanent pacemaker: last resort for rate control
• LAA occlusion: if anticoagulation contraindicated

Referral Criteria

• All new AF: confirm diagnosis, investigate, start anticoagulation
• Symptomatic despite rate control: cardiology for rhythm control options
• Consider ablation referral: young patients, paroxysmal AF, drug-refractory

• AF increases stroke risk 5-fold and doubles mortality
• AF-related strokes are more severe, with 30-day mortality ~25%
• With appropriate anticoagulation: stroke risk reduced by ~65%
• Heart failure risk doubled in AF patients
• Many patients can be well-controlled with rate/rhythm control
• Post-ablation: ~70% remain in sinus rhythm at 1 year for paroxysmal AF
• Quality of life significantly improved with symptom control

CHA₂DS₂-VASc Score

DOAC Summary for AF