What is Atrial Fibrillation?
Atrial fibrillation (AF) is the most common sustained cardiac arrhythmia, characterised by disorganised atrial electrical activity producing an irregularly irregular ventricular response. It is classified as first diagnosed, paroxysmal (<7 days, self-terminating), persistent (>7 days), long-standing persistent (>12 months), or permanent. AF substantially increases stroke risk (5× compared to general population) and doubles all-cause mortality.
Pathophysiology
AF is driven by ectopic triggers (commonly pulmonary vein foci) and a susceptible atrial substrate with areas of fibrosis, inflammation, and electrical heterogeneity. Perpetuation involves multiple re-entrant wavelets and rotors. Atrial remodelling — electrical, structural, and autonomic — occurs as AF begets AF, making early rhythm control essential before irreversible substrate change. Risk factors include hypertension, heart failure, valvular disease, obesity, and obstructive sleep apnoea.
Clinical Features & Symptoms
- Palpitations (irregularly irregular)
- Dyspnoea and exercise intolerance
- Fatigue and lethargy
- Chest discomfort or tightness
- Dizziness or pre-syncope
- Polyuria (atrial natriuretic peptide release)
- Up to 30% of patients are asymptomatic ("silent AF")
Diagnosis
AF diagnosis requires ECG documentation showing: irregular RR intervals without discernible P waves, fibrillatory baseline at 350–600 bpm. A 12-lead ECG or single-lead recording (≥30 seconds or full 12-lead ECG) is required. Wearable or implantable loop recorders are used for paroxysmal AF detection. Always evaluate for triggers: thyroid function, electrolytes, echocardiography, sleep study.
Current Treatment Guidelines
Anticoagulation (CHA₂DS₂-VASc guided)
Class I, Level ANOACs (apixaban, rivaroxaban, dabigatran, edoxaban) preferred over warfarin for non-valvular AF. Start if CHA₂DS₂-VASc ≥2 in males or ≥3 in females. Always assess HAS-BLED for modifiable bleeding risks before initiation.
Rate control
Class I, Level BBeta-blockers (bisoprolol) or rate-limiting CCBs (diltiazem, verapamil) as first-line. Target resting HR <110 bpm. Digoxin as second-line in HFrEF. Avoid rate-limiting CCBs in HFrEF.
Rhythm control
Class IIa, Level BEarly rhythm control (within 12 months of diagnosis) now preferred (EAST-AFNET 4). Options: flecainide/propafenone (structurally normal heart), amiodarone (HF/LV dysfunction), or catheter ablation as first-line in paroxysmal AF.
Catheter ablation
Class I, Level A (paroxysmal, failed drugs)Pulmonary vein isolation (PVI) is recommended for symptomatic paroxysmal or persistent AF after failure of antiarrhythmic drugs, or as first-line in paroxysmal AF. Superior to drugs for maintaining sinus rhythm.
ABC pathway (ESC 2020)
Class I, Level BA = Anticoagulation, B = Better symptom control (rate/rhythm), C = Cardiovascular risk factor management (HTN, obesity, OSA, exercise). Structured AF management pathway reduces outcomes.
Monitoring & Treatment Targets
Annual reassessment of CHA₂DS₂-VASc and HAS-BLED scores. Renal function every 6–12 months (NOAC dosing). ECG monitoring for AF burden. INR if on warfarin (TTR >70%). 24-hour Holter for recurrence post-ablation.
Key Clinical Trials
Clinical Guidelines
External Resources
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Frequently Asked Questions
When should anticoagulation be started in atrial fibrillation?
Oral anticoagulation is recommended for all patients with non-valvular AF and a CHA₂DS₂-VASc score ≥2 in males or ≥3 in females (Class I, Level A). NOACs are preferred over warfarin. Female sex alone (score = 1) does not warrant anticoagulation. Always assess HAS-BLED score to identify and correct modifiable bleeding risks.
What is the difference between rate control and rhythm control in AF?
Rate control aims to slow the ventricular response (target HR <110 bpm at rest) without attempting to restore sinus rhythm. Rhythm control aims to restore and maintain sinus rhythm using antiarrhythmic drugs or catheter ablation. The EAST-AFNET 4 trial showed early rhythm control significantly reduces cardiovascular events versus rate control, making it the preferred strategy when initiated within 12 months of AF diagnosis.
Which NOAC is best for atrial fibrillation?
All four NOACs (apixaban, rivaroxaban, dabigatran, edoxaban) are superior or non-inferior to warfarin for stroke prevention in non-valvular AF. Choice depends on renal function, bleeding risk, dosing preference, and drug interactions. Apixaban has the most evidence for a combined efficacy-safety benefit. Dabigatran 110mg is preferred in patients with high bleeding risk. All require dose adjustment for renal impairment.
Medical disclaimer: This content is intended for qualified healthcare professionals and does not constitute medical advice. Always apply clinical judgment and refer to current local guidelines and institutional protocols.