Name two major contraindications to adenosine use.

• A. Second- or third-degree AV block; active asthma or significant bronchospasm
• B. Hypertension and hyperlipidemia
• C. Chronic kidney disease and diabetes
• D. Atrial flutter and sinus tachycardia

Answer: (A)

Adenosine works by briefly blocking conduction through the AV node, which can terminate SVTs that rely on the AV node for propagation. The two major contraindications are preexisting second- or third-degree AV block and active asthma or significant bronchospasm. In someone with high-grade AV block, further slowing the AV node can lead to dangerous bradycardia or even asystole, so giving adenosine is unsafe. In asthma, adenosine can provoke bronchoconstriction via receptors in the airways, risking a severe asthma attack. Because of these risks, those conditions are strong reasons to avoid adenosine. Other listed conditions don’t inherently preclude its use; for example, hypertension, hyperlipidemia, chronic kidney disease, and diabetes aren’t direct contraindications, and while atrial flutter or sinus tachycardia aren’t primarily treated with adenosine, they aren’t absolute contraindications.