Atrial Fibrillation (AF)

A 72-year-old man presents to the emergency department with palpitations, progressive fatigue, and exertional dyspnea for 3 days. He reports having intermittent similar episodes over the past several months that resolved spontaneously. His medical history is significant for hypertension, obesity, and obstructive sleep apnea. He drinks alcohol occasionally. On examination, his pulse is irregularly irregular at 130/min, blood pressure is 128/78 mmHg, and oxygen saturation is normal. Cardiac examination reveals variable intensity of S1 without a distinct S4. Electrocardiogram shows absence of P waves, an irregularly irregular rhythm, and a fibrillatory baseline. Transthoracic echocardiography demonstrates left atrial enlargement with preserved left ventricular ejection fraction. His CHA₂DS₂-VASc score is 3. Diagnosis?

Diagnosis is Atrial fibrillation.

1. Definition

Atrial fibrillation is a supraventricular arrhythmia characterized by disorganized atrial activation, resulting in an irregularly irregular ventricular response and absence of P waves, and is associated with an increased risk of thromboembolism.

2. Etiology

2.1 Cardiovascular Causes

  1. Hypertension (most common)
  2. Coronary artery disease
  3. Heart failure
  4. Valvular disease (especially mitral)

2.2 Non-Cardiac Causes

  1. Hyperthyroidism
  2. Alcohol (“holiday heart”)
  3. Obesity
  4. Obstructive sleep apnea
  5. Pulmonary disease

2.3 Risk Factors (Modifiable Emphasis)

  1. Obesity
  2. Hypertension
  3. Diabetes
  4. Alcohol use
  5. Sleep apnea

3. Pathophysiology

  1. Pulmonary vein ectopic activity initiates AF
  2. Electrical remodeling
    • Shortened atrial refractory period
  3. Structural remodeling
    • Atrial fibrosis and dilation
  4. Leads to:
    • Loss of atrial contraction
    • Blood stasis → thrombus formation
    • Reduced cardiac output

4. Clinical Features

4.1 Core Features

  1. Palpitations
  2. Dyspnea
  3. Fatigue
  4. Dizziness or syncope

4.2 Associated Features

  1. Examination findings:
    • Irregularly irregular pulse
    • Pulse deficit
  2. Complications:
    • Stroke or systemic embolism
    • Heart failure
    • Tachycardia-induced cardiomyopathy
  3. Distinguishing feature:
    • Irregularly irregular rhythm with absent P waves
  4. Other features:
    • May be asymptomatic
    • Alcohol can trigger episodes
    • Symptoms worsen with comorbid illness

5. Diagnosis

5.1 ECG

  1. Irregularly irregular rhythm
  2. Absence of P waves
  3. Fibrillatory baseline

5.2 Classification (ACC 2023)

  1. Stage 1: At risk (risk factors present)
  2. Stage 2: Pre-AF (structural/electrical abnormalities)
  3. Stage 3: AF
    • 3A: Paroxysmal (<7 days)
    • 3B: Persistent (>7 days)
    • 3C: Long-standing persistent (>12 months)
    • 3D: Successful AF ablation
  4. Stage 4: Permanent AF

5.3 Stroke Risk Assessment

  1. Use validated clinical risk score (CHA₂DS₂-VASc)
  2. Anticoagulation is recommended based on estimated annual thromboembolic risk
    • Men ≥2
    • Women ≥3
  3. Intermediate risk → consider:
    • AF burden
    • Age
    • Comorbidities
    • Renal function
  4. Reassess periodically

5.4 Additional Evaluation

  1. Echocardiography
    • Left atrial size
    • Structural heart disease
  2. Laboratory tests:
    • Thyroid function
    • Electrolytes
  3. Ambulatory monitoring (paroxysmal AF)

6. Management

6.1 Goals of Therapy

  1. Stroke prevention
  2. Symptom control
  3. Maintain sinus rhythm / reduce AF burden
  4. Prevent progression
  5. Risk factor modification

6.2 Acute Management

  1. Hemodynamically unstable
    • Immediate synchronized cardioversion
  2. Hemodynamically stable
    • Rate control:
      • Beta-blocker
      • Diltiazem / verapamil (if normal LVEF)

6.3 Rate Control

  1. Beta-blockers (first-line)
  2. Non-DHP calcium channel blockers
    • Diltiazem / verapamil (only if normal LVEF)
  3. Digoxin
    • Useful in selected patients
    • May be added for additional rate control

6.4 Rhythm Control (GUIDELINE EMPHASIS)

  1. Early rhythm control is emphasized, especially in:
    • Symptomatic AF
    • Recently diagnosed AF
    • Heart failure
  2. Benefits:
    • Symptom improvement
    • Reduced AF burden
    • Reduced heart failure risk
    • Slows disease progression
  3. Options:
    • Electrical cardioversion
    • Antiarrhythmic drugs

6.5 Catheter Ablation (CLASS 1 IN SELECTED PATIENTS)

  1. First-line in:
    • Selected patients, generally younger with few comorbidities
    • Symptomatic paroxysmal AF
  2. Also Class 1:
    • AF with heart failure with reduced EF
  3. Benefits:
    • Improves symptoms
    • Reduces AF recurrence and progression

6.6 Stroke Prevention

  1. DOACs preferred over warfarin
  2. Warfarin only if:
    • Mechanical valve
    • Moderate–severe mitral stenosis
  3. After ablation:
    • Continue anticoagulation ≥3 months
    • Long-term based on stroke risk (NOT rhythm status)
  4. Left atrial appendage occlusion:
    • Reasonable in patients with moderate/high stroke risk
    • Used when anticoagulation is contraindicated

6.7 Risk Factor Modification (CORE THERAPY)

  1. Weight loss (~10% if overweight/obese)
  2. Blood pressure control
  3. Regular exercise
  4. Treat sleep apnea
  5. Reduce alcohol
  6. Smoking cessation

7. Complications

  1. Stroke / systemic embolism
  2. Heart failure
  3. Tachycardia-induced cardiomyopathy
  4. Progression of AF

8. Key Clinical Insight

Irregularly irregular rhythm + absent P waves + fibrillatory baseline = atrial fibrillation → assess stroke risk (CHA₂DS₂-VASc) for anticoagulation

9. Exam Level Pearls

  1. Most common sustained arrhythmia
  2. Irregularly irregular pulse = AF
  3. Stroke risk (not symptoms) determines anticoagulation
  4. DOACs preferred over warfarin
  5. Early rhythm control reduces progression
  6. Catheter ablation is first-line in selected patients
  7. Use non-DHP CCBs only if LVEF is normal
  8. Anticoagulation continues after ablation based on risk
By Prabin Duwadee at

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