What Is Atrial Fibrillation?
Atrial fibrillation (AFib) is a chaotic, irregular heart rhythm originating in the upper chambers (atria). Instead of beating in a coordinated fashion, the atria quiver rapidly — up to 400–600 times per minute — sending disordered impulses to the ventricles. The result is an irregular, often fast pulse. AFib affects more than 33 million people globally and is the most common sustained cardiac arrhythmia.
AFib is classified as paroxysmal (episodes that stop on their own within 7 days), persistent (lasting more than 7 days), or permanent (ongoing, where rhythm control is no longer pursued).
Causes and Risk Factors
- Hypertension — the single largest modifiable risk factor
- Coronary artery disease and prior myocardial infarction
- Heart failure and cardiomyopathy
- Valvular heart disease (especially mitral valve disease)
- Hyperthyroidism — excess thyroid hormone is a reversible trigger
- Obstructive sleep apnoea
- Heavy alcohol use — "holiday heart" describes AFib triggered by binge drinking
- Age over 65 — prevalence roughly doubles each decade after 55
- Obesity — visceral fat drives atrial inflammation and fibrosis
Symptoms
Up to 30% of people with AFib are asymptomatic — it's discovered on a routine ECG. When symptoms occur they include palpitations (described as fluttering, racing, or irregular heartbeat), fatigue and reduced exercise capacity, shortness of breath, dizziness, and chest discomfort. Symptoms are often worse during episodes of rapid ventricular rate.
Stroke Risk and the CHA₂DS₂-VASc Score
The chaotically beating atria allow blood to pool, particularly in the left atrial appendage, where clots can form and embolise to the brain. AFib raises stroke risk fivefold. The CHA₂DS₂-VASc score estimates annual stroke risk:
- Congestive heart failure (1 pt) · Hypertension (1 pt) · Age ≥75 (2 pts) · Diabetes (1 pt)
- Prior Stroke/TIA (2 pts) · Vascular disease (1 pt) · Age 65–74 (1 pt) · Female sex (1 pt)
Anticoagulation is generally recommended for men scoring ≥2 and women scoring ≥3. Direct oral anticoagulants (apixaban, rivaroxaban, dabigatran) are preferred over warfarin.
Treatment: Rate vs Rhythm Control
Rate control uses beta-blockers (metoprolol, bisoprolol) or calcium channel blockers (diltiazem, verapamil) to keep the resting ventricular rate below 110 bpm without necessarily restoring sinus rhythm. This is adequate for many older, less symptomatic patients.
Rhythm control aims to restore and maintain sinus rhythm using antiarrhythmic drugs (flecainide, propafenone, amiodarone, dronedarone) or electrical cardioversion (a synchronised DC shock under sedation). The EAST-AFNET 4 trial showed early rhythm control significantly reduced cardiovascular death and hospitalisation compared with rate control alone.
Catheter Ablation
Pulmonary vein isolation (PVI) uses radiofrequency energy or cryoablation to electrically isolate the pulmonary veins — the most common source of AFib triggers. Success rates are 70–80% for paroxysmal AFib after a single procedure, lower for persistent AFib. Ablation is increasingly recommended for symptomatic patients who prefer not to take lifelong antiarrhythmic drugs.
Lifestyle Modifications
Aggressive risk-factor management significantly reduces AFib burden. Weight loss of ≥10% in obese patients can reduce AFib episodes by up to 50%. Treating hypertension, managing sleep apnoea, limiting alcohol, and regular moderate-intensity exercise all reduce recurrence rates.