Atrial fibrillation

Atrial fibrillation (AF or Afib) is a type of arrhythmia characterized by an irregular and often rapid heart rhythm that originates in the atria, the upper chambers of the heart. This abnormal rhythm can impair the heart's ability to efficiently pump blood, increasing the risk of serious complications such as stroke, heart failure, and blood clots.

Electrocardiogram showing atrial fibrillation

Types of Atrial Fibrillation

Atrial fibrillation can be classified into four major types based on duration and response to treatment:

Paroxysmal atrial fibrillation

Paroxysmal AF occurs intermittently and resolves spontaneously within 7 days, often within 24 hours. It may be asymptomatic or cause noticeable palpitations. When paroxysmal AF alternates with bradycardia, the condition is called tachybrady syndrome.

Persistent atrial fibrillation

This type of AF persists for more than 7 days and typically requires medical intervention, such as cardioversion, to restore normal rhythm.

Long-standing persistent atrial fibrillation

AF that continues for more than 12 months. It is often resistant to treatment and may lead to structural changes in the heart.

Permanent atrial fibrillation

When AF cannot be restored to normal rhythm despite attempts at treatment or when the decision is made not to pursue rhythm control, it is termed permanent.

Causes

Heart changes associated with AF

AF results from abnormalities in the heart's electrical conduction system and structural changes in cardiac tissue. Common causes include:

• Hypertension
• Ischemic heart disease
• Heart valve disease
• Cardiomyopathy
• Congenital heart defect
• Hyperthyroidism
• Sleep apnea
• Alcohol abuse ("Holiday heart syndrome")
• Postoperative changes (especially after cardiac surgery)
• Pericarditis or myocarditis
• Aging-related fibrosis

Risk Factors

Several risk factors are associated with increased likelihood of developing AF:

• Advanced age (especially >65 years)
• Family history
• Obesity
• Diabetes mellitus
• Chronic kidney disease
• Pulmonary diseases (e.g., COPD)
• Excessive alcohol or stimulant use
• Sedentary lifestyle or extreme endurance training
• Thyroid disorders

Signs and Symptoms

Symptoms of AF vary in severity and may include:

• Palpitations
• Fatigue
• Shortness of breath
• Dizziness or syncope
• Chest pain
• Hypotension

Some patients may remain asymptomatic, and AF is discovered incidentally.

Diagnosis

Diagnosis of AF typically involves:

• Electrocardiogram (ECG) – confirms the absence of P waves and irregularly irregular ventricular response.
• Echocardiography – assesses structural abnormalities, thrombus formation.
• Holter monitor – records rhythm over 24–48 hours.
• Event monitor or implantable loop recorder – for intermittent symptoms.
• Blood tests – to assess thyroid function, electrolytes.
• Transesophageal echocardiography (TEE) – to detect atrial thrombi before cardioversion.

Complications

AF increases the risk of several complications:

• Stroke – due to thrombus formation in the left atrial appendage.
• Heart failure – from prolonged rapid ventricular response.
• Cognitive impairment – from cerebral hypoperfusion.
• Sudden cardiac arrest – rarely.

Treatment

Management goals include stroke prevention, rate or rhythm control, and treatment of underlying conditions.

Stroke Prevention

• Anticoagulation therapy (e.g., warfarin, dabigatran, rivaroxaban, apixaban)
• CHA2DS2-VASc score guides anticoagulation decisions.

Rate Control

• Beta-blockers (e.g., metoprolol)
• Calcium channel blockers (e.g., diltiazem)
• Digoxin

Rhythm Control

• Antiarrhythmic drugs (e.g., amiodarone, flecainide)
• Electrical cardioversion
• Catheter ablation – for drug-refractory or symptomatic patients

Surgical Options

• Maze procedure
• Left atrial appendage closure – e.g., Watchman device

Prevention

Preventive strategies include:

• Managing blood pressure, lipid disorders, and diabetes
• Maintaining a healthy weight
• Limiting alcohol and stimulant use
• Treating sleep apnea
• Smoking cessation

Epidemiology

• Affects 2.7–6.1 million people in the U.S.
• Increases with age: ~9% prevalence in adults ≥65
• More common in males and individuals of European descent

See Also

• Arrhythmia
• Heart failure
• Stroke
• Cardiac electrophysiology

External Links

• American Heart Association – Atrial Fibrillation
• CDC Factsheet on AFib
• NIH – Atrial Fibrillation