Narrow vs Wide Complex Tachycardia: The Decision Tree That Passes Questions
Stable or unstable, narrow or wide, regular or irregular — the four-branch tree that resolves nearly every tachycardia question.
December 5, 2026 · 7 min read
Tachycardia questions look complicated and are not. Two yes-or-no questions determine the answer.
Question 1: Is the patient unstable?
Hypotension, altered mental status, chest pain, signs of shock, or acute heart failure mean unstable. Unstable plus tachycardia equals synchronized cardioversion, with sedation if time allows.
Question 2: Narrow or wide?
- Stable + narrow + regular: vagal maneuvers, then adenosine 6 mg then 12 mg
- Stable + narrow + irregular: likely atrial fibrillation — rate control per protocol, do not use adenosine
- Stable + wide + regular: treat as VT — amiodarone or procainamide infusion
- Stable + wide + irregular: consider polymorphic VT / torsades — magnesium, be ready to defibrillate
Sinus tachycardia is a symptom
Rate under about 150 with visible P waves is usually sinus tach driven by fever, pain, hypovolemia, hypoxia, or anxiety. Treat the cause. Cardioverting sinus tachycardia is always the wrong answer.
Pulseless wide complex
No pulse changes everything: pulseless VT is treated exactly like VF — defibrillate, CPR, epinephrine, amiodarone.
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