Which medication class is contraindicated in bradycardia or AV block?

• A. ACE inhibitors.
• B. Beta-blockers.
• C. Nitrates.
• D. Diuretics.

Answer: (B)

In bradycardia or AV block, you avoid drugs that further slow the heart rate or impair conduction through the AV node. Beta-blockers do exactly that: they block beta-adrenergic receptors, which decreases the heart rate (negative chronotropy) and slows AV nodal conduction (negative dromotropy). When the heart is already running slowly or the AV node isn’t conducting well, adding a beta-blocker can worsen the block or drop the heart rate enough to reduce cardiac output, leading to dizziness, syncope, or worse. That makes this class contraindicated in these states.

The other options don’t primarily affect AV nodal conduction. ACE inhibitors, nitrates, and diuretics mainly influence blood pressure or fluid status rather than the electrical conduction system, so they aren’t inherently contraindicated by bradycardia or AV block because of their primary actions. In practice, the focus is on stopping or adjusting the offending agent and managing symptoms, with pacing considered if the patient is unstable or the block is advanced.