What is cardiac output?

• A. The volume of blood the heart pumps into the ventricles each minute.
• B. The rate at which blood flows through capillaries.
• C. The pressure generated by the heart during diastole.
• D. The amount of blood the heart pumps into blood vessels, affecting blood pressure.

Answer: (D)

Cardiac output is the amount of blood the heart pumps into the arterial system each minute. It’s determined by heart rate and stroke volume, so it reflects how much blood is being delivered to tissues per minute. This quantity helps drive tissue perfusion and also helps set arterial pressure when vascular resistance is stable. The option that describes the heart pumping blood into the blood vessels and that this affects blood pressure best captures both the per-minute ejection and its role in circulation, which is why it’s the most appropriate description. The other ideas miss the essential idea: cardiac output is about the volume ejected per minute into the arteries, not the volume entering the ventricles, not flow through capillaries, and not diastolic pressure.