A 68-year-old woman with rapid atrial fibrillation at 180 per minute develops hypotension and altered sensorium. She has a pulse and is breathing spontaneously. The most appropriate immediate intervention is:
- A Unsynchronized defibrillation at 360 J monophasic
- B IV adenosine 6 mg rapid bolus
- C Synchronized cardioversion starting at 120 to 200 J biphasic ✓
- D Amiodarone 300 mg IV bolus over 1 hour
Correct answer: C. Synchronized cardioversion starting at 120 to 200 J biphasic
Explanation
An unstable tachyarrhythmia with a pulse requires immediate synchronized cardioversion. For atrial fibrillation the initial recommended biphasic energy is 120 to 200 J. Unsynchronized shocks risk delivery on the T wave and provoking ventricular fibrillation, which kills option A. Amiodarone is an adjunct for refractory cases, not the first move, and adenosine is ineffective in atrial fibrillation.
Reference: AHA Guidelines for CPR and Emergency Cardiovascular Care, 2020 ed.
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