Cardiac reserve is defined as which of the following?

Cardiac reserve is defined as which of the following?

• A. The capacity to increase cardiac output above resting levels.
• B. The maximum heart rate achievable.
• C. The amount of blood ejected per beat.
• D. The difference between systolic and diastolic pressure.

Answer: (A)

Cardiac reserve refers to the heart’s ability to boost its output beyond resting levels to meet higher metabolic demands, such as during exercise or stress. It is defined by how much max cardiac output exceeds resting cardiac output, reflecting the extra blood the heart can pump when needed. This capacity arises from the combined ability to raise heart rate and increase stroke volume (since CO = heart rate × stroke volume). The idea is about the overall draw the heart can make on the system, not just a single parameter. The other ideas—maximum heart rate alone, amount ejected per beat, or the difference between systolic and diastolic pressure—don’t capture the heart’s enhanced output relative to rest.

Cardiac reserve refers to the heart’s ability to boost its output beyond resting levels to meet higher metabolic demands, such as during exercise or stress. It is defined by how much max cardiac output exceeds resting cardiac output, reflecting the extra blood the heart can pump when needed. This capacity arises from the combined ability to raise heart rate and increase stroke volume (since CO = heart rate × stroke volume). The idea is about the overall draw the heart can make on the system, not just a single parameter. The other ideas—maximum heart rate alone, amount ejected per beat, or the difference between systolic and diastolic pressure—don’t capture the heart’s enhanced output relative to rest.