What is atrial fibrillation, how is it diagnosed and treated?

Atrial Fibrillation: Definition, Diagnosis, and Treatment

Atrial fibrillation (AF) is a supraventricular tachyarrhythmia characterized by uncoordinated atrial activation with consequent deterioration of atrial mechanical function, which significantly increases the risk of stroke, heart failure, and mortality if not properly managed. 1, 2

What is Atrial Fibrillation?

Atrial fibrillation is the most common sustained cardiac arrhythmia, characterized by:

• Uncoordinated electrical activity in the atria
• Loss of effective atrial contraction ("atrial kick")
• Irregular ventricular response
• Reduced cardiac output (20-30% decrease in stroke volume)
• Increased risk of thromboembolic events, particularly stroke (5-fold higher risk)

Classification of AF:

• Paroxysmal AF: Self-terminating within 7 days
• Persistent AF: Continuous AF lasting >7 days
• Long-standing persistent AF: Continuous AF >12 months
• Permanent AF: When rhythm control strategy is abandoned 2

Diagnosis of Atrial Fibrillation

ECG Findings (Essential for Diagnosis):

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

Diagnostic Approach:

1. 12-lead ECG: The gold standard for diagnosis
2. Holter monitoring: For paroxysmal AF with frequent episodes
3. Event recorder: For infrequent episodes
4. Portable ECG recording tool: For documentation of paroxysmal AF 1, 2

Minimum Evaluation:

• History and physical examination: To identify symptoms, type of AF, onset, frequency, precipitating factors
• Electrocardiogram: To verify AF and identify other cardiac abnormalities
• Chest radiograph: To evaluate lung parenchyma and pulmonary vasculature when clinically indicated
• Echocardiogram: To identify valvular disease, atrial size, ventricular function, and potential thrombi
• Blood tests: Thyroid function, complete blood count, electrolytes, renal and liver function 1, 2

Treatment of Atrial Fibrillation

Treatment focuses on three main goals:

1. Prevention of Thromboembolism:

• Risk stratification: Using CHA₂DS₂-VASc score

• Anticoagulation options:

  • Warfarin: Target INR 2.0-3.0
  • Direct Oral Anticoagulants (DOACs): Apixaban, rivaroxaban, dabigatran, edoxaban

  Apixaban has demonstrated superiority to warfarin in reducing stroke and systemic embolism (hazard ratio 0.79) with fewer major bleeding events 3

2. Rate Control:

• First-line agents:
  • Beta-blockers (e.g., metoprolol, carvedilol)
  • Non-dihydropyridine calcium channel blockers (e.g., verapamil, diltiazem)
  • Digoxin (less effective during exercise or sympathetic states)
• Target heart rate: 60-100 beats per minute at rest 2, 4

3. Rhythm Control:

• Pharmacological cardioversion:

  • Class IC agents (flecainide, propafenone): Most effective for recent-onset AF in structurally normal hearts
  • Class III agents (amiodarone, sotalol, dofetilide): Preferred in structural heart disease

• Electrical cardioversion: Direct current cardioversion when pharmacological methods fail or urgent restoration of sinus rhythm is needed

• Catheter ablation: For symptomatic patients refractory to or intolerant of antiarrhythmic medications 1, 2, 4

Treatment Strategy Selection

The choice between rate control and rhythm control depends on:

1. Patient symptoms and quality of life impact
2. Age and comorbidities
3. Left atrial size and duration of AF
4. Previous treatment failures

Important caveat: Rhythm control has not been shown to be superior to rate control in reducing mortality or morbidity for most patients with AF, but may improve quality of life in symptomatic patients 2, 5

Complications and Monitoring

• Stroke: Most devastating complication, requires proper anticoagulation
• Heart failure: Due to tachycardia-induced cardiomyopathy with sustained rapid ventricular rates
• Tachycardia-mediated cardiomyopathy: Especially in patients unaware of the arrhythmia
• Cognitive dysfunction: May occur due to asymptomatic embolic events 1, 2

Common Pitfalls to Avoid

1. Inadequate anticoagulation: Failing to properly assess stroke risk and prescribe appropriate anticoagulation
2. Inappropriate rate control targets: Excessively strict rate control may lead to symptomatic bradycardia
3. Antiarrhythmic drug selection errors: Using Class IC drugs in patients with structural heart disease
4. Discontinuing anticoagulation after cardioversion: Stroke risk persists even after restoration of sinus rhythm
5. Missing paroxysmal AF: Inadequate monitoring in patients with suspected paroxysmal episodes

Proper management of AF requires a systematic approach addressing stroke prevention, symptom management, and treatment of underlying conditions to improve quality of life and reduce morbidity and mortality.