What happens to cardiac output if both heart rate and stroke volume increase?

What happens to cardiac output if both heart rate and stroke volume increase?

• A. Cardiac output increases.
• B. Cardiac output decreases.
• C. Cardiac output remains unchanged.
• D. Cardiac output becomes unpredictable.

Answer: (A)

Cardiac output is the amount of blood pumped by the heart each minute, and it depends on two factors: heart rate (how many beats per minute) and stroke volume (how much blood is ejected with each beat). The relationship is CO = HR × SV. If both heart rate and stroke volume increase, their product increases as well, so cardiac output rises. For example, going from 70 beats per minute with a 70 ml stroke volume to 90 beats per minute with a 90 ml stroke volume changes CO from about 4.9 L/min to about 8.1 L/min. In real life, very high heart rates can sometimes reduce filling time and limit stroke volume, but when both are increasing, the overall output goes up.

Cardiac output is the amount of blood pumped by the heart each minute, and it depends on two factors: heart rate (how many beats per minute) and stroke volume (how much blood is ejected with each beat). The relationship is CO = HR × SV. If both heart rate and stroke volume increase, their product increases as well, so cardiac output rises. For example, going from 70 beats per minute with a 70 ml stroke volume to 90 beats per minute with a 90 ml stroke volume changes CO from about 4.9 L/min to about 8.1 L/min. In real life, very high heart rates can sometimes reduce filling time and limit stroke volume, but when both are increasing, the overall output goes up.