There is a plateau beyond which increasing preload does not raise stroke volume. This statement describes:

• A. Stroke volume continues to rise linearly with preload.
• B. There is a plateau beyond which increasing preload does not raise stroke volume.
• C. Preload decreases stroke volume after exceeding a limit.
• D. Preload has no effect on stroke volume.

Answer: (B)

The concept being tested is the Frank-Starling relationship: as preload (venous return) increases, stroke volume rises because the heart muscle fibers are stretched to an optimal length, enhancing contractile force. However, this rise is not infinite—there is a plateau where further increases in preload no longer boost stroke volume. That’s exactly what the statement describes. The other options imply either a continuous linear rise, a decrease, or no effect, which don’t match the physiological relationship.