Which agent is used to terminate certain rapid heart rhythms by AV nodal suppression?

Which agent is used to terminate certain rapid heart rhythms by AV nodal suppression?

• A. Cimetidine
• B. Adenosine
• C. Vaccines
• D. Recombinant DNA

Answer: (B)

Adenosine is used to terminate certain rapid heart rhythms by AV nodal suppression. It works by briefly activating A1 receptors in the AV node, which causes a transient block of AV conduction. This interruption stops the reentrant circuit that depends on fast AV nodal transmission, allowing the heart to reset to a normal rhythm. The effect is very short-lived because adenosine is rapidly metabolized, so a rapid IV bolus can stop the tachycardia within seconds with minimal lasting effects. Other options do not affect AV nodal conduction—cimetidine is a gastric acid reducer, vaccines are immunizations, and recombinant DNA is a lab technique—so they aren’t used for terminating AV nodal–dependent tachyarrhythmias.

Adenosine is used to terminate certain rapid heart rhythms by AV nodal suppression. It works by briefly activating A1 receptors in the AV node, which causes a transient block of AV conduction. This interruption stops the reentrant circuit that depends on fast AV nodal transmission, allowing the heart to reset to a normal rhythm. The effect is very short-lived because adenosine is rapidly metabolized, so a rapid IV bolus can stop the tachycardia within seconds with minimal lasting effects. Other options do not affect AV nodal conduction—cimetidine is a gastric acid reducer, vaccines are immunizations, and recombinant DNA is a lab technique—so they aren’t used for terminating AV nodal–dependent tachyarrhythmias.