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Atrial Fibrillation (AF)

Key Points ⚡

  • AF is the most common cardiac arrhythmia in adults, with prevalence increasing with age (10% in those >85 years).
  • Categorised into:
  • Paroxysmal: episodes >30 seconds, spontaneously terminate within 7 days (often 48 hrs).
  • Persistent: episodes >7 days or terminated by cardioversion.
  • Permanent: accepted AF, no further rhythm control attempts.
  • Pathophysiology: chaotic atrial electrical activity (often from pulmonary veins) causes loss of coordinated atrial contraction, irregularly irregular ventricular rhythm, and increased thromboembolism risk.
  • Common causes include hypertension (most common), ischemic heart disease, heart failure, valvular disease, and non-cardiac causes like thyroid disease, electrolyte disturbances, infection.
  • Risk factors: male sex, Caucasian ethnicity, advancing age, alcohol, smoking, obesity, chronic kidney disease, obstructive sleep apnea.
  • Symptoms vary from asymptomatic to palpitations, breathlessness, chest discomfort, dizziness, syncope.
  • Diagnosis confirmed by 12-lead ECG showing absent P waves, irregularly irregular RR intervals, variable ventricular rate.
  • Management priorities:
  • Anticoagulation (reduce stroke risk) guided by CHA₂DS₂-VASc score.
  • Symptom management via rate control or rhythm control strategies.
  • Rhythm control options: electrical or pharmacological cardioversion (flecainide, amiodarone).
  • Rate control options: beta-blockers, calcium channel blockers, digoxin.
  • Invasive options: left atrial ablation, pace-and-ablate strategy.
  • Complications include thromboembolism (stroke), tachycardia-induced cardiomyopathy, heart failure exacerbation.

Introduction

  • AF is a supraventricular arrhythmia characterised by chaotic atrial electrical activity leading to ineffective atrial contraction and irregular ventricular response.
  • Prevalence increases with age; common in elderly.

Cardiac Conduction System

  • Electrical impulses originate in sinoatrial node (SAN), modulated by autonomic nervous system.
  • Impulses spread through atria → AV node → Bundle of His → bundle branches → Purkinje fibers.

Pathophysiology

  • Ectopic foci near pulmonary veins trigger re-entry circuits → chaotic atrial depolarisation.
  • Irregular conduction through AV node causes irregular ventricular rate.
  • Blood stasis in atria increases risk of thrombus formation → stroke or systemic embolism.

Causes

Cardiac Causes

  • Hypertension (most common)
  • Ischemic heart disease
  • Heart failure with reduced EF
  • Valvular disease (stenosis, regurgitation)
  • Congenital heart disease
  • Atrial/ventricular dilation or hypertrophy
  • Pre-excitation syndromes (e.g. WPW)
  • Sick sinus syndrome

Non-cardiac Causes

  • Acute infection
  • Electrolyte imbalances (hypokalemia, hyponatremia)
  • Pulmonary embolism
  • Thyroid dysfunction (hyper/hypothyroidism)
  • Diabetes mellitus

Risk Factors

  • Male sex, Caucasian ethnicity
  • Increasing age
  • Alcohol consumption
  • Smoking
  • Obesity
  • Comorbidities: CKD, OSA

Clinical Features

History

  • May be asymptomatic; incidental ECG finding.
  • Symptoms: palpitations, breathlessness, chest discomfort, light-headedness, reduced exercise tolerance, syncope.
  • TIA or stroke can be first presentation.
  • Assess cardiac and medical history, medications, social factors.

Examination

  • Irregularly irregular pulse (radial-apical delay common).
  • Signs of heart failure: raised JVP, added heart sounds, crackles, peripheral edema.

Differential Diagnosis

  • Other supraventricular tachycardias
  • Ventricular ectopics

Investigations

Bedside

  • Vital signs to assess stability.
  • 12-lead ECG diagnostic: absent P waves, irregularly irregular rhythm, variable rate.

Ambulatory ECG

  • 24h, 7-day Holter, or implantable loop recorder for paroxysmal AF.

Laboratory

  • FBC (infection), U&E (electrolytes), LFTs (baseline for anticoagulants), TFTs (thyroid disease), CRP, coagulation screen, NT-proBNP (heart failure assessment).

Imaging

  • Echocardiogram (if results alter management) for structural or valvular disease.
  • Chest X-ray for heart failure signs.

Diagnosis

  • ECG evidence with typical arrhythmia pattern lasting ≥30 seconds.

Management

Immediate

  • ABCDE assessment; urgent synchronized DC cardioversion if unstable/shock/syncope/ischemia/heart failure.

Ongoing

  • Anticoagulation based on CHA₂DS₂-VASc score (≥2 in men, ≥3 in women usually anticoagulate).
  • Use ORBIT score to assess bleeding risk.
  • Rhythm control: cardioversion (electrical or pharmacological with flecainide or amiodarone).
  • Rate control: beta-blockers, rate-limiting calcium channel blockers, digoxin.
  • Specialist referral if symptoms uncontrolled.

Rhythm Control

  • Suitable in new-onset AF or symptomatic patients despite rate control.
  • Anticoagulate for 4-6 weeks pre and post cardioversion (unless AF onset <48h).

Rate Control

  • Appropriate if rhythm control contraindicated or not preferred.
  • Drugs: bisoprolol, verapamil, diltiazem, digoxin.

Paroxysmal AF

  • ‘Pill-in-the-pocket’ approach with Class 1C antiarrhythmics in selected patients.

Invasive Management

  • Left atrial ablation to isolate pulmonary vein triggers.
  • Pace and ablate strategy for refractory rate control.

Complications

  • Stroke and systemic embolism
  • Tachycardia-induced cardiomyopathy
  • Worsening heart failure
  • Cardiac ischemia

Key Summary

  • AF causes irregular atrial and ventricular contraction.
  • Most common arrhythmia with multifactorial aetiology.
  • Presents variably; diagnosis confirmed on ECG.
  • Main treatments: anticoagulation, rate or rhythm control tailored to patient.
  • Invasive options reserved for drug-refractory cases.

References

  • Benjamin et al. Heart Disease and Stroke Statistics, 2019.
  • NICE CKS Atrial Fibrillation, 2024 update.
  • European Society of Cardiology 2020 Guidelines on AF.
  • Pluymaekers et al., Early vs delayed cardioversion, J Med, 2019.
  • Brignole et al., APAF-CRT Mortality Trial, Eur Heart J, 2021.
  • Marrouche et al., Catheter Ablation for AF, NEJM, 2018.
  • Acute Coronary Syndrome (ACS)
  • Acute Heart Failure
  • Atrioventricular Block
  • Brugada Syndrome
  • Bundle Branch Block