Clinical Case

A 28-year-old man, previously healthy, presents to the emergency department with intense palpitations, diaphoresis, and dizziness that started about 40 minutes earlier.

He reports similar self-limited episodes in the past. He denies chest pain or dyspnea.

On examination:

  • HR ≈ 220 bpm
  • BP: 90/60 mmHg
  • Alert, anxious, and diaphoretic

A 12-lead ECG was obtained on admission.

Electrocardiogram showing an irregular wide QRS tachyarrhythmia consistent with pre-excited atrial fibrillation
Initial ECG: irregular wide QRS tachyarrhythmia

Question

What arrhythmia is seen on the ECG, and what should the initial management be?

Answer and discussion

1) Electrocardiographic diagnosis

The tracing shows:

  • A completely irregular tachyarrhythmia
  • Wide QRS
  • Variable QRS morphology
  • No organized P waves

This pattern is highly suggestive of pre-excited atrial fibrillation.

The differential diagnosis includes polymorphic ventricular tachycardia, but the extreme irregularity and beat-to-beat QRS variation favor AF with conduction over an accessory pathway.

2) Electrophysiological mechanism

In pre-excited atrial fibrillation, the disorganized atrial impulse is conducted to the ventricles predominantly over an accessory pathway with anterograde conduction, bypassing the AV node.

This results in:

  • Very high ventricular rates
  • Wide, variable QRS complexes
  • Risk of degeneration into ventricular fibrillation

3) Immediate management

The patient has hemodynamic instability (hypotension).

The correct management is:

  • Immediate synchronized electrical cardioversion

Important contraindications:

  • Beta-blockers
  • Calcium channel blockers
  • Digoxin
  • Adenosine

These drugs slow conduction through the AV node and may favor exclusive conduction over the accessory pathway, increasing the risk of ventricular fibrillation.

4) ECG after cardioversion

Electrocardiogram in sinus rhythm with a short PR and a delta wave consistent with ventricular pre-excitation
Post-cardioversion ECG: sinus rhythm with ventricular pre-excitation

After cardioversion, the ECG shows:

  • Sinus rhythm
  • Short PR
  • Delta wave

These findings are consistent with manifest ventricular pre-excitation, characteristic of Wolff-Parkinson-White syndrome.

Practical points

  • An irregular wide QRS tachyarrhythmia in a young patient should raise suspicion of pre-excited AF.
  • Instability → immediate cardioversion.
  • Avoid AV nodal blocking drugs.
  • Refer for electrophysiological evaluation and ablation of the accessory pathway.