Which of the following best describes the effect of epinephrine on the heart?

• A. Decreases heart rate
• B. No effect on the heart
• C. Increases heart rate, increases contractility, and increases conduction velocity
• D. Increases heart rate but decreases contractility

Answer: (C)

Epinephrine acts on beta-1 adrenergic receptors in the heart, triggering a cascade that raises intracellular cAMP. This increases calcium availability in cardiac cells, producing a stronger contraction (positive inotropy). It also speeds up the pacemaker activity in the SA node, raising heart rate, and enhances conduction through the AV node (positive dromotropy). So the overall effect is an uptick in heart rate, contractility, and conduction velocity. The other options don’t fit because epinephrine does not slow the heart, nor is its effect on the heart null, and it does not increase heart rate while reducing contractility.