Which of the following best describes preload reserve when SV response to EDV is minimal during a preload augmentation protocol?

• A. High preload reserve
• B. Moderate preload reserve
• C. Low preload reserve
• D. No change to preload reserve

Answer: (C)

Preload reserve is how much stroke volume can rise when filling (end-diastolic volume) increases. In a preload augmentation protocol, you raise EDV to see how SV responds. If the SV changes only slightly despite more filling, the heart isn’t able to convert the extra preload into greater output, so the preload reserve is low. This flat or blunted response can happen when the ventricle is stiff, contractility is reduced, or afterload limits efficient ejection, all of which blunt the Frank-Starling relationship. So the description that fits best is a low preload reserve.