In unstable tachycardia with narrow complex ≤ 0.11 sec, what is the recommended initial management?

• A. Synchronized Cardioversion & consider sedation ETOMIDATE 0.15 mg/kg IV/IO
• B. Adenosine 12 mg rapid IVP/IO
• C. Repeat Synchronized Cardioversion
• D. Defibrillate

Answer: (A)

When a patient has an unstable tachycardia with a narrow QRS complex, the priority is to rapidly restore a perfusing rhythm. A synchronized cardioversion delivers a shock that is timed to the heart’s R wave, which safely brakes the rapid rate and improves hemodynamics. This approach is favored because the patient is unstable, and pharmacologic attempts to terminate the rhythm can delay definitive relief of poor perfusion.

Sedation is considered if the patient can tolerate it and time allows. Etomidate at 0.15 mg/kg IV/IO is a common choice because it acts quickly and has minimal cardiovascular depressant effects, which is important in someone who is unstable.

Adenosine is typically reserved for stable narrow-complex SVT. In an unstable patient, trying adenosine risks a temporary loss of rhythm without addressing the instability, and it’s not the initial maneuver when you need rapid stabilization. Defibrillation is reserved for pulseless cardiac rhythms (no pulse) or for a rhythm that remains unstable after synchronized cardioversion. Repeating synchronized cardioversion is something you’d consider if the first attempt doesn’t convert, not as the first step.

So, the best initial management is synchronized cardioversion with the option to sedate using etomidate if the situation allows.