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Conditions · Chest

Atrial fibrillation !

Atrial fibrillation is the most common lasting irregular heartbeat: the upper chambers quiver instead of beating, raising the risk of clots and stroke.

Updated 2026-10-30

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Why it happens

What it is

The most common sustained arrhythmia: disorganised electrical activity in the atria replaces normal sinus rhythm, so the atria quiver and the ventricles beat irregularly.

Who gets it

Becomes more common with age. In Latin America, rheumatic mitral disease and Chagas cardiomyopathy are important additional causes, often in younger patients. A 2016 review found that 46% of Latin American outpatients with atrial fibrillation lacked guideline-based anticoagulation, from 41.8% in Brazil to 54.8% in Colombia.

Causes

  • Hypertension and hypertensive heart disease
  • Heart failure and coronary artery disease
  • Valve disease, especially rheumatic mitral stenosis
  • Hyperthyroidism
  • Alcohol ("holiday heart"), surgery, infection or pulmonary embolism
  • Sometimes no cause is found

Risk factors

  • Older age
  • Hypertension
  • Obesity and obstructive sleep apnoea
  • Diabetes
  • Heart failure
  • Alcohol use

Pathophysiology

Rapid, chaotic impulses, often triggered from the pulmonary vein sleeves, bombard the atrioventricular node, which conducts them irregularly. The atria lose effective contraction, so blood stagnates, especially in the left atrial appendage, where clots form. Atrial stretch and fibrosis help the arrhythmia sustain itself.

Classification

  • Paroxysmal: ends on its own or with treatment within 7 days
  • Persistent: lasts more than 7 days
  • Long-standing persistent: more than 1 year when rhythm control is chosen
  • Permanent: patient and clinician accept the arrhythmia and stop trying to restore rhythm
  • Valvular (moderate–severe mitral stenosis or mechanical valve) vs non-valvular

Symptoms and signs

  • Palpitations
  • Irregularly irregular pulse
  • Breathlessness and reduced exercise tolerance
  • Fatigue, dizziness
  • Chest discomfort
  • Can be silent and found by chance or after a stroke

Diagnosis

Clinical
Irregularly irregular pulse; pulse deficit between apex and radial pulse. Stroke risk is estimated with CHA2DS2-VASc and bleeding risk with tools such as HAS-BLED; guidelines vary on the scores used.
Tests
12-lead ECG: no P waves, fibrillatory baseline and irregularly irregular RR intervals. Holter or event monitoring for paroxysmal episodes. Thyroid function, electrolytes, kidney function and blood count.
Imaging
Echocardiography for atrial size, valves (mitral stenosis) and ventricular function; transoesophageal echo looks for left atrial appendage clot before cardioversion.

Differential diagnosis

  • Atrial flutter with variable block
  • Multifocal atrial tachycardia
  • Sinus rhythm with frequent ectopic beats
  • Other supraventricular tachycardias

Goal of treatment

Prevent stroke and systemic embolism, control symptoms with rate or rhythm control, and treat the underlying causes.

Treatment

Acute
Unstable patients: urgent synchronised electrical cardioversion.
Medical
Rate control: beta-blockers or non-dihydropyridine calcium channel blockers, sometimes digoxin, to slow conduction through the atrioventricular node.
Medical
Anticoagulation according to stroke risk (CHA2DS2-VASc): direct oral anticoagulants, or vitamin K antagonists for moderate–severe mitral stenosis or mechanical valves.
Procedure
Rhythm control in selected patients: antiarrhythmic drugs, electrical cardioversion and catheter ablation (pulmonary vein isolation); left atrial appendage occlusion when anticoagulation is not possible.
Lifestyle
Control of blood pressure, weight, sleep apnoea and alcohol reduces recurrences.

Drugs for this condition

Complications

  • Ischaemic stroke and systemic embolism
  • Tachycardia-induced cardiomyopathy and heart failure
  • Bleeding related to anticoagulation
  • Cognitive decline

Prognosis

Often recurrent and progressive, but with anticoagulation and good rate or rhythm control most patients live well. Stroke risk rises with the CHA2DS2-VASc score; untreated, it is a major cause of disabling stroke.

Prevention

  • Control of hypertension, obesity and diabetes
  • Moderate alcohol
  • Treatment of sleep apnoea
  • Prevention of rheumatic heart disease

Test yourself

Think of the answer, then tap the question to see it.

What are the ECG features of atrial fibrillation?

No P waves, a fibrillatory baseline and irregularly irregular RR intervals, usually with narrow QRS complexes.

What score estimates stroke risk in non-valvular atrial fibrillation?

CHA2DS2-VASc: heart failure, hypertension, age, diabetes, prior stroke/TIA, vascular disease and sex category.

Where do most clots form in atrial fibrillation?

In the left atrial appendage, where blood stagnates when the atria stop contracting effectively.

What is the first step in an unstable patient with fast atrial fibrillation?

Urgent synchronised electrical cardioversion.

Which anticoagulant class is used in AF with moderate–severe mitral stenosis or a mechanical valve?

Vitamin K antagonists; direct oral anticoagulants are not used in these settings.

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Educational information, not medical advice. For any symptom, see a health professional.

Sources: Atrial Fibrillation (StatPearls (NCBI Bookshelf), 2026); Targeting stroke risk and improving outcomes in patients with atrial fibrillation in Latin America (Sao Paulo medical journal, 2016) · adapted, CC BY 4.0.

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Representative model, for educational purposes only.

Left atrium highlighted on the Durgical 3D model