For bradycardia due to a 2nd-degree heart block in non-symptomatic patients, which medication is indicated?

• A. Atropine
• B. Epinephrine
• C. Calcium chloride
• D. Amiodarone

Answer: (A)

Atropine works by blocking the parasympathetic influence on the heart, specifically reducing vagal tone at the SA node and AV node. That relief of inhibition speeds automaticity and improves AV nodal conduction, which can raise the heart rate in bradycardia caused by AV nodal block. In a stable patient with a second-degree AV block, giving atropine IV can quickly increase rate and help maintain perfusion while you assess the block and monitor for response. If atropine works, you have a temporizing measure; if there’s no improvement or if the block is more advanced (Mobitz II or higher), pacing becomes the next step. The other medications aren’t first-line for this scenario: epinephrine can be reserved for unstable bradycardia or codes and carries more risk of tachyarrhythmias and increased myocardial oxygen demand; calcium chloride addresses electrolyte issues like hyperkalemia or certain overdoses rather than AV-block–related bradycardia; amiodarone is used for tachyarrhythmias and may worsen AV conduction.