What is atrial fibrillation (A fib)?

What is Atrial Fibrillation (A-fib)?

Atrial fibrillation is a supraventricular tachyarrhythmia characterized by uncoordinated atrial activation with consequent deterioration of atrial mechanical function, resulting in irregular heartbeats and increased risk of stroke and heart failure. 1

Electrocardiographic Characteristics

Atrial fibrillation is diagnosed based on three key ECG findings:

• Irregular RR intervals (when AV conduction is intact)
• Absence of distinct P waves
• Replacement of P waves with rapid oscillations or fibrillatory waves that vary in amplitude, shape, and timing 1, 2

The fibrillatory waves are often more visible in certain ECG leads, particularly V1, and typically have intervals between atrial activations of less than 200 ms 2.

Pathophysiology

The pathophysiology of atrial fibrillation involves:

• Uncoordinated electrical activation of the atria
• Loss of effective atrial contraction ("atrial kick")
• Irregular ventricular filling
• Potential for thrombus formation, particularly in the left atrial appendage 1, 3

The ventricular response to atrial fibrillation depends on several factors:

• Electrophysiological properties of the AV node
• Level of vagal and sympathetic tone
• Presence or absence of accessory conduction pathways
• Effects of medications 1, 2

Clinical Significance and Complications

Atrial fibrillation is associated with significant morbidity and mortality:

• Increased stroke risk (5-fold higher than general population) 1, 4
• Heart failure (3-fold increased risk) 1, 4
• Doubled risk of all-cause mortality 1, 4
• Reduced quality of life due to symptoms
• Increased healthcare utilization and costs 1

Common Symptoms

Symptoms of atrial fibrillation vary widely and may include:

• Fatigue (most common symptom) 1
• Palpitations
• Dyspnea
• Chest pain
• Dizziness or syncope
• Exercise intolerance 4

Importantly, approximately 10-40% of patients with atrial fibrillation are asymptomatic 4.

Risk Factors and Associated Conditions

Atrial fibrillation is commonly associated with:

• Advanced age (prevalence increases significantly after age 65) 1
• Hypertension (present in over 80% of AF patients) 1
• Heart failure 1
• Coronary artery disease 1
• Valvular heart disease 1
• Diabetes mellitus 1
• Obesity 4
• Hyperthyroidism 1
• Chronic kidney disease 1

Clinical Implications

Atrial fibrillation requires management focused on:

1. Stroke prevention through anticoagulation (reduces stroke risk by 60-80% in high-risk patients) 4
2. Rate control to manage symptoms and prevent tachycardia-induced cardiomyopathy 1
3. Rhythm control in selected patients to restore and maintain sinus rhythm 4

Important Considerations

• Patients with atrial fibrillation who have a stroke risk of ≥2% per year generally benefit from anticoagulation therapy 4
• Direct oral anticoagulants (DOACs) like apixaban and rivaroxaban are generally preferred over warfarin due to lower bleeding risks 3, 5, 4
• Stopping anticoagulation therapy increases stroke risk and should not be done without medical supervision 3, 5
• Lifestyle modifications (weight loss, exercise) are recommended for all patients with AF or at risk of developing AF 4

Atrial fibrillation represents a significant healthcare burden, affecting millions of adults and requiring careful management to reduce complications and improve quality of life.