The nurse knows beta blockers are as effective as antianginals because they do what?

• A. Increase oxygen to the systemic circulation.
• B. Maintain heart rate and blood pressure.
• C. Decrease heart rate and decrease myocardial contractility.
• D. Decrease heart rate and increase myocardial contractility.

Answer: (C)

Beta blockers relieve angina by lowering the heart’s oxygen demand. They do this primarily through two actions: slowing the heart rate (negative chronotropy) and reducing the force of contraction (negative inotropy). With a slower heart rate, the heart spends less time in active pumping, which lowers overall oxygen consumption. With weaker contractions, the heart uses less energy and oxygen per beat. Together, these effects lessen myocardial oxygen demand, helping prevent angina episodes just as other antianginal strategies aim to do.

Increasing oxygen delivery to the systemic circulation isn’t how beta blockers work, so that option doesn’t fit. Maintaining heart rate and blood pressure would not reduce oxygen demand. Decreasing heart rate while increasing contractility would raise oxygen use, which would worsen angina.