Atrial Fibrillation: A Comprehensive Guide

What is Atrial Fibrillation?

Atrial fibrillation (AFib) is the most common sustained cardiac arrhythmia, affecting over 6 million Americans. It's characterized by chaotic, disorganized atrial electrical activity where multiple electrical impulses fire simultaneously, causing the atria to quiver rather than contract effectively.

ECG Characteristics

Primary Features:

1. Irregularly Irregular Rhythm - The hallmark of AFib with completely unpredictable R-R intervals
2. Absent P Waves - Normal P waves are replaced by fibrillatory waves
3. Fibrillatory (f) Waves - Fine, irregular baseline oscillations best seen in leads V1 and II
4. Narrow QRS Complexes - Typically normal duration unless bundle branch block coexists
5. Variable Ventricular Rate - Usually 100-180 bpm when untreated

Rate Classification:

• Slow AFib: 100 bpm (uncontrolled)

Clinical Significance

Hemodynamic Impact:

• Loss of Atrial Kick: Reduces cardiac output by 20-30%
• Reduced Diastolic Filling: Particularly problematic in heart failure
• Tachycardia-Induced Cardiomyopathy: Can develop with prolonged rapid rates

Thromboembolic Risk:

• Blood stasis in left atrial appendage increases clot formation
• 5-fold increased stroke risk compared to sinus rhythm
• Risk stratified using CHA₂DS₂-VASc score

Management

Immediate Assessment:

1. Hemodynamic stability (BP, mental status, chest pain)
2. Stroke risk calculation (CHA₂DS₂-VASc score)
3. Rate vs rhythm control strategy

Treatment:

• Rate Control: Beta-blockers, calcium channel blockers, digoxin
• Rhythm Control: Antiarrhythmics, cardioversion, ablation
• Anticoagulation: Based on stroke risk (DOAC or warfarin)

Key Points

• AFib = irregularly irregular rhythm without P waves
• Always assess hemodynamic stability
• Stroke prevention is critical
• New-onset <48h may allow cardioversion
• Chronic AFib needs anticoagulation consideration