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Atrial Fibrillation

caution
Lead II
25 mm/s10 mm/mV
Heart rate
72bpm
RR
833ms
QT
328ms

Atrial Fibrillation

Chaotic, disorganized electrical activity in the atria. Multiple wavefronts depolarize the atrial tissue simultaneously, producing no coordinated atrial contraction. The AV node conducts impulses irregularly.

Recognition· 4
  • No P waves (fibrillatory baseline instead)
  • Irregularly irregular rhythm
  • Narrow QRS complex
  • Variable RR intervals
Mechanism

Atria quiver chaotically instead of contracting — AV node filters impulses randomly

Multiple areas in the atria fire electrical impulses chaotically at 350-600/min. The atria quiver instead of contracting effectively. The AV node acts as a gatekeeper, randomly conducting some impulses to the ventricles, creating the characteristic irregular ventricular response.

Findings· 4
  • Irregularly irregular rhythm.
  • No discrete P waves — replaced by fibrillatory baseline.
  • Narrow QRS (unless aberrant conduction).
  • Variable RR intervals.
Clinical Impact
Stroke risk 5× higher
↓
Heart failure from prolonged rapid rates
↓
Most common sustained arrhythmia (2-4% of population)RISK

Blood pools in atria → clot risk → stroke

Management· 2
1

Primary Treatment

Rate control (beta-blockers, calcium channel blockers) or rhythm control (cardioversion, antiarrhythmics).

2

Additional Options

Anticoagulation based on CHA₂DS₂-VASc score to prevent stroke.

Differential· 2
Atrial Flutter

Can appear irregular with variable block. Look for organized sawtooth baseline vs chaotic fibrillatory waves.

SVT

If AFib rate is very fast and appears regular. SVT has uniform RR intervals; AFib is irregularly irregular.