A patient presents with wide-complex tachycardia at rate 180/min. ECG shows atrioventricular dissociation, capture beats, and fusion beats. What is the most likely diagnosis and immediate management?

• A SVT with aberrant conduction; adenosine 6 mg IV push
• B Antidromic AVRT; IV verapamil or diltiazem
• C Hyperkalaemia-induced wide QRS tachycardia; calcium gluconate IV
• D Ventricular tachycardia (VT); if haemodynamically stable: IV amiodarone; if unstable: synchronised DC cardioversion ✓

Explanation

AV dissociation (P waves independent of QRS), capture beats (narrow QRS sinus capture during VT), and fusion beats (hybrid QRS from simultaneous ventricular and sinus activation) are pathognomonic features of ventricular tachycardia. These three signs together constitute the Wellens/Brugada criteria for VT diagnosis. Management: haemodynamically unstable VT requires immediate synchronised DC cardioversion; stable VT is managed with IV amiodarone (150 mg over 10 min then infusion) or IV procainamide. Verapamil or adenosine must never be given empirically in wide-complex tachycardia of uncertain origin as they can cause haemodynamic collapse in VT.

Reference: Harrison's Principles of Internal Medicine, 21st ed.

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Written and medically reviewed by the StethoPrep medical team.