Adenosine is used to treat which condition?

• A. Ventricular fibrillation
• B. Supraventricular tachycardia
• C. Atrial flutter
• D. Bradycardia

Answer: (B)

Adenosine is used to terminate episodes of narrow-complex supraventricular tachycardia by briefly blocking conduction through the AV node. It binds to A1 receptors in the AV node, causing potassium efflux and hyperpolarization, which temporarily halts AV nodal conduction and often interrupts the reentrant circuit that sustains the tachycardia. Because it has an extremely short half-life, its effect is brief, and it can convert the rhythm to normal sinus rhythm very quickly when the SVT is AV-nodal dependent. It’s given as an IV push with a rapid saline flush and continuous rhythm monitoring.

This is not used for ventricular fibrillation or pulseless VT, which require defibrillation and other agents. It won’t reliably convert atrial flutter and may only transiently slow AV nodal conduction to reveal flutter waves, but it does not treat the atrial flutter itself. In bradycardia, adenosine can worsen AV nodal block, so it is not an appropriate treatment.