Atrial fibrillation (AF)
Atrial fibrillation is the most common sustained arrhythmia seen in emergency practice.
In the ED the priorities are to confirm the diagnosis, assess haemodynamic stability, identify and treat precipitants, choose an appropriate acute strategy (usually rate control; rhythm control when indicated), and make timely, safe anticoagulation and disposition decisions.
UK practice should follow NICE NG196 (diagnosis, risk stratification, anticoagulation, timing of cardioversion) and Resuscitation Council (UK) ALS guidance for cardioversion technique (NICE NG196; Resus UK).
ECG features and diagnosis
- Always confirm suspected AF with a 12‑lead ECG after pulse palpation; if paroxysmal AF is suspected and a single ECG is non‑diagnostic, arrange ambulatory ECG monitoring (NICE NG196).
- Typical ECG features:
- Irregularly irregular R‑R intervals with no consistent pattern.
- No discrete P waves; instead a loss of an isoelectric baseline with fibrillatory waves (coarse or fine).
- Usually narrow QRS complexes (<120 ms) unless there is bundle branch block, pre‑excitation, or rate‑related aberrancy.
- Common mimics to exclude:
- Atrial flutter with variable block (look for flutter waves in leads II, III, aVF).
- Multifocal atrial tachycardia (variable P‑wave morphologies).
- Frequent PACs or sinus arrhythmia.
- Context and comparison ECGs are often useful to distinguish these.