What effect does an increased heart rate generally have on the heart's cardiac output?

What effect does an increased heart rate generally have on the heart's cardiac output?

• A. Decreases it
• B. Has no effect
• C. Increases it
• D. Only affects the rhythm

Answer: (C)

An increased heart rate typically leads to an increase in cardiac output, which is the volume of blood the heart pumps per minute. Cardiac output is calculated using the formula: Cardiac Output = Heart Rate x Stroke Volume. When the heart rate rises, provided that stroke volume remains constant or is capable of maintaining itself, the overall output of blood by the heart will increase.

In many situations, especially during exercise or physical exertion, the body requires more oxygen and nutrients, necessitating an increase in cardiac output. This is primarily achieved by elevating the heart rate. Although there are limits to how much heart rate can rise before stroke volume starts to decrease (due to the reduced diastolic filling time at extremely high rates), a generally higher heart rate correlates with a higher output in typical scenarios.

This rationale supports why the correct answer is an increase in cardiac output in response to a higher heart rate.