What is the relationship between heart rate and cardiac output?

What is the relationship between heart rate and cardiac output?

• A. An increase in heart rate generally leads to an increase in cardiac output.
• B. An increase in heart rate always decreases cardiac output.
• C. Heart rate has no effect on cardiac output.
• D. Cardiac output depends only on stroke volume.

Answer: (A)

Cardiac output is the amount of blood the heart pumps per minute and is calculated as heart rate times stroke volume. When heart rate increases, there are more beats per minute, so cardiac output tends to rise, provided the ventricles can fill adequately and maintain a strong stroke volume. In practice, if the rate becomes very fast, diastolic filling time shortens and stroke volume can drop, which can limit or blunt the increase in cardiac output. This is why the statement that an increase in heart rate generally leads to an increase in cardiac output best captures the relationship. It’s not correct to claim there is no effect, and cardiac output depends on both heart rate and stroke volume, not only the latter.

Cardiac output is the amount of blood the heart pumps per minute and is calculated as heart rate times stroke volume. When heart rate increases, there are more beats per minute, so cardiac output tends to rise, provided the ventricles can fill adequately and maintain a strong stroke volume. In practice, if the rate becomes very fast, diastolic filling time shortens and stroke volume can drop, which can limit or blunt the increase in cardiac output. This is why the statement that an increase in heart rate generally leads to an increase in cardiac output best captures the relationship. It’s not correct to claim there is no effect, and cardiac output depends on both heart rate and stroke volume, not only the latter.