Which statement about myocardial oxygen demand with epinephrine 1:1000 is correct?

• A. Decreases myocardial oxygen demand
• B. No effect on oxygen demand
• C. Decreases oxygen transport to the heart
• D. Increases myocardial oxygen demand

Answer: (D)

The key idea is that myocardial oxygen demand rises when factors that drive the heart to work harder increase. Epinephrine at 1:1000 activates beta-1 receptors in the heart, boosting heart rate and contractility. It also activates alpha-1 receptors in the vessels, increasing systemic vascular resistance and afterload. Both a faster heartbeat and stronger contractions raise the heart’s oxygen consumption, and the added wall stress from higher afterload further increases demand. While epinephrine can cause some coronary vasodilation to help supply the heart, this does not offset the overall rise in oxygen demand; the net effect is an increase in myocardial oxygen consumption. That’s why the correct statement is that myocardial oxygen demand increases.