In a preload augmentation trial, what would you observe in SV as EDV rises?

• A. SV should increase with rising EDV up to the Frank-Starling plateau.
• B. SV decreases.
• C. SV remains constant.
• D. SV increases indefinitely.

Answer: (A)

Rising EDV through preload augmentation stretches the heart muscle fibers more, which increases the force of contraction via length-dependent activation. As a result, stroke volume increases as EDV rises, following the ascending portion of the Frank-Starling relationship. This continues until the fibers reach near-optimal length, at which point further filling produces little additional contractile benefit and SV plateaus. So, you’d observe SV increase with EDV up to the Frank-Starling plateau.