Which drug class decreases heart rate and contractility?

• A. Nitrates
• B. Calcium channel blockers
• C. Beta-blockers
• D. Diuretics

Answer: (C)

Blocking sympathetic stimulation to the heart with beta-blockers reduces both the heart’s rate and its pumping strength. They inhibit beta-1 receptors in the heart, lowering cAMP, which decreases calcium entry into cardiac cells. That slows the SA node, slows AV conduction, and reduces contractility—producing negative chronotropic and negative inotropic effects. This combination is why beta-blockers are the class that decreases heart rate and contractility.

Nitrates mainly reduce preload through venodilation and can cause reflex tachycardia, so they don’t directly lower contractility. Diuretics decrease blood volume and pressure with little direct effect on the heart’s pumping strength. Calcium channel blockers can also reduce heart rate and contractility (especially non-dihydropyridines), but the classic class associated with both reductions is beta-blockers.