In a stable patient with a narrow-complex tachycardia, which nonpharmacologic maneuver can be attempted first?

• A. Vagal maneuvers
• B. Adenosine IV bolus
• C. Calcium channel blocker infusion
• D. Electrical cardioversion

Answer: (A)

In a stable patient with a narrow-complex tachycardia, the best first step is to try vagal maneuvers because they are safe, quick, and noninvasive. These maneuvers increase parasympathetic (vagal) tone and slow conduction through the AV node. If the tachycardia is AV-nodal dependent, slowing or interrupting AV nodal conduction can terminate the reentrant circuit and restore normal rhythm without using medications. That’s why these maneuvers are attempted before drug therapy or electrical intervention.

If vagal maneuvers don’t work, the next step is a rapid IV adenosine bolus, which transiently blocks AV nodal conduction and often terminates SVT or reveals the underlying rhythm. Pharmacologic options like calcium channel blockers are more invasive and carry more risk, so they aren’t the initial maneuver after trying vagal techniques. Electrical cardioversion is reserved for instability or failure of other measures.