In adult tachycardia without signs of cardiovascular instability, if the QRS complex is less than 0.12 seconds, which intervention is recommended?

• A. True - vagal maneuvers are recommended, along with adenosine (if regular rhythm) and beta-blocker/Calcium channel blocker
• B. False - vagal maneuvers are not recommended
• C. Adenosine should be given regardless of rhythm
• D. Immediate cardioversion is indicated

Answer: (A)

When a patient has a narrow QRS tachycardia and is hemodynamically stable, this points to a supraventricular mechanism rather than a ventricular one. The first move is to try vagal maneuvers. These maneuvers increase vagal tone and slow conduction through the AV node, which can interrupt certain reentrant tachycardias that rely on the AV node. If the rhythm is regular and the tachycardia persists after vagal maneuvers, adenosine is the next best step. Adenosine transiently blocks AV nodal conduction, often terminating typical AV nodal reentrant tachycardia and also helping confirm the diagnosis by briefly altering the conduction pattern. If adenosine doesn’t terminate the tachycardia, move to rate control with a beta-blocker or a nondihydropyridine calcium channel blocker to slow AV nodal conduction and maintain stability while monitoring. Immediate cardioversion is not required in a stable, narrow-QRS tachycardia.