A patient presents to the emergency department with palpitations, light-headedness, and a rapid pulse. On the monitor, you observe a narrow-complex tachycardia with no discernible P waves and a ventricular rate of 180 bpm. The patient is hemodynamically stable. What is the most appropriate initial intervention for this rhythm?
Administer intravenous adenosine rapidly followed by a saline flush.
Give atropine intravenously.
Administer intravenous amiodarone over 10 minutes.
Perform immediate synchronized cardioversion.