Atrial Fibrillation

A 55 year old female presents to the emergency department with sudden onset palpitations that began 30 minutes ago. She describes a sensation of heart racing and reports lightheadedness and dizziness, without chest pain, shortness of breath, or syncope. She has had similar self resolving episodes in the past and has a history of coronary artery disease. Vital signs show a pulse rate of 180 beats per minute, blood pressure of 110/70 mm Hg, respiratory rate of 16 breaths per minute, oxygen saturation of 96 percent on room air, and temperature of 98.2 F. Laboratory studies are within normal limits. ECG shows absent P waves, irregularly irregular rhythm, and narrow QRS complexes. Transesophageal echocardiography demonstrates a thrombus in the left atrium. Diagnosis?

Diagnosis is Atrial fibrillation with left atrial thrombus.

1. Definition

Atrial fibrillation is a supraventricular arrhythmia characterized by disorganized atrial electrical activity, resulting in an irregularly irregular ventricular rhythm and loss of effective atrial contraction.

2. Modern Classification

Atrial fibrillation is now considered a disease continuum:

1. Stage 1: At risk for AF
2. Stage 2: Pre AF with structural or electrical abnormalities
3. Stage 3: AF including paroxysmal, persistent, and long standing persistent AF
4. Stage 4: Permanent AF

This framework emphasizes risk factor modification, early detection, and treatment.

3. Etiology and Risk Factors

1. Coronary artery disease
2. Hypertension
3. Valvular heart disease, especially mitral stenosis
4. Thyrotoxicosis
5. Alcohol use
6. Obstructive sleep apnea
7. Obesity and metabolic syndrome

4. Pathophysiology

1. Ectopic impulses arise from the pulmonary veins
2. Cause chaotic atrial depolarization
3. Loss of atrial kick reduces cardiac output
4. Leads to blood stasis in the left atrium, especially the left atrial appendage
5. Results in thrombus formation and risk of embolic stroke

5. Clinical Features

1. Palpitations
2. Dizziness or lightheadedness
3. Fatigue
4. Shortness of breath
5. May be asymptomatic

6. Diagnosis

1. ECG findings
• Absent P waves
• Irregularly irregular rhythm
• Narrow QRS complexes
2. Echocardiography
• Detects left atrial thrombus
• Evaluates structural heart disease
3. Laboratory evaluation
• Rule out thyroid dysfunction and electrolyte abnormalities

7. Management

Management is based on rate control, rhythm control, and stroke prevention

7.1 Rate Control

1. Beta blockers
2. Non dihydropyridine calcium channel blockers
3. Digoxin in selected patients

7.2 Rhythm Control

1. Early rhythm control is recommended to reduce AF burden and progression
2. Electrical cardioversion
• Indicated if hemodynamically unstable
3. Pharmacologic cardioversion
• Amiodarone, flecainide, ibutilide
4. Key cardioversion principles
• AF <48 hours
• Cardioversion may be performed
• Anticoagulation should still be considered based on stroke risk
• AF >48 hours or unknown duration
• Requires
• TEE to exclude thrombus, or
• At least 3 weeks of anticoagulation before cardioversion
• If left atrial thrombus is present
• Cardioversion is contraindicated
• Requires adequate anticoagulation and confirmation of thrombus resolution before cardioversion

7.3 Anticoagulation

1. Use CHA2DS2 VASc score to assess stroke risk
2. Anticoagulation is indicated when
• Score ≥2 in men or ≥2 in women
3. Direct oral anticoagulants are preferred over warfarin in nonvalvular AF
4. Continue anticoagulation for at least 4 weeks after cardioversion

7.4 Interventional Therapy

1. Catheter ablation
• First line in selected symptomatic patients, especially paroxysmal AF
2. Left atrial appendage occlusion
• For patients with contraindications to long term anticoagulation

8. Complications

1. Ischemic stroke
2. Systemic embolism
3. Heart failure
4. Tachycardia induced cardiomyopathy

9. Key Clinical Insight

Irregularly irregular rhythm with absent P waves and presence of left atrial thrombus indicates atrial fibrillation with high embolic risk, requiring anticoagulation and delaying cardioversion until thrombus resolution

10. Exam Level Pearls

1. Irregularly irregular rhythm is diagnostic of atrial fibrillation
2. Left atrial appendage is the most common site of thrombus formation
3. Cardioversion is contraindicated in the presence of atrial thrombus
4. Anticoagulation is the most important step to prevent stroke
5. Early rhythm control improves long term outcomes