CO = ________ x ________

• A. Heart Rate x Stroke Volume
• B. Mean Arterial Pressure x Systemic Vascular Resistance
• C. Stroke Volume x Afterload
• D. Heart Rate x Contractility

Answer: (A)

Cardiac output is the volume of blood the heart pumps each minute. It depends on how often the heart beats and how much blood is ejected with each beat. Multiply heart rate (beats per minute) by stroke volume (mL per beat) to get CO in mL per minute (often expressed as L/min when you convert).

The other relationships describe different things: mean arterial pressure relates to CO and systemic vascular resistance (MAP = CO × SVR), not CO itself; stroke volume times afterload doesn’t define the flow per minute; and heart rate times contractility isn’t a standard way to express CO because contractility affects stroke volume, not as a separate multiplier for CO.

So the product of heart rate and stroke volume is the correct representation of cardiac output. For example, 70 beats/min with 70 mL/beat gives about 4900 mL/min, or ~4.9 L/min.