Wide Complex Tachycardia in the Emergency Department
A 55-year-old man with a history of myocardial infarction presents to the emergency department with palpitations and lightheadedness. He is diaphoretic and his blood pressure is 85/50 mmHg. ECG shows a regular wide-complex tachycardia at 180 bpm. The QRS duration is 160 ms, and there is a right bundle branch block morphology with a superior axis. He has an IV line and is on a monitor. The emergency physician asks for your help in managing this patient.
1. What is the most likely diagnosis, and what is the immediate management?
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The most likely diagnosis is ventricular tachycardia (VT), given the history of myocardial infarction, wide QRS, and RBBB morphology with superior axis (suggesting left posterior fascicular VT or scar-related VT). Immediate management: The patient is hemodynamically unstable (hypotension, diaphoresis). Perform synchronized cardioversion with sedation if possible. If the patient deteriorates, proceed to unsynchronized defibrillation. Do not delay for pharmacologic therapy. If cardioversion is unsuccessful, consider antiarrhythmic drugs (amiodarone) and correct electrolytes.
2. If the patient were hemodynamically stable, what would be your approach to differentiate VT from SVT with aberrancy?
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Use the Brugada criteria or other algorithms: (1) absence of RS complex in all precordial leads; (2) RS interval >100 ms in any precordial lead; (3) AV dissociation; (4) morphology criteria in V1–V2 and V6. In this case, the presence of a prior MI strongly favors VT. Other clues: extreme axis deviation, QRS >160 ms, and fusion beats. If still uncertain, administer adenosine (if no contraindication) to unmask underlying atrial activity, but avoid if pre-excited AF is suspected. For stable wide-complex tachycardia, amiodarone or procainamide can be used, but cardioversion is preferred if VT is confirmed.