What is the effect of increased venous return on stroke volume?

What is the effect of increased venous return on stroke volume?

• A. Increased venous return leads to increased stroke volume due to greater preload.
• B. Increased venous return leads to decreased stroke volume due to stretch.
• C. Venous return does not affect stroke volume.
• D. Increased venous return increases afterload, reducing stroke volume.

Answer: (A)

Preload determines how much the ventricle is stretched at the end of filling. When venous return increases, more blood fills the heart, raising the end-diastolic volume. This greater stretch allows the cardiac muscle to contract more forcefully (the Frank-Starling mechanism), so a larger amount of blood is ejected with each beat. In healthy hearts, increasing venous return thus raises stroke volume through a stronger contraction tied to preload. The idea that stretch would reduce stroke volume isn’t accurate in normal physiology, and venous return mainly changes stroke volume by altering preload rather than increasing afterload.

Preload determines how much the ventricle is stretched at the end of filling. When venous return increases, more blood fills the heart, raising the end-diastolic volume. This greater stretch allows the cardiac muscle to contract more forcefully (the Frank-Starling mechanism), so a larger amount of blood is ejected with each beat. In healthy hearts, increasing venous return thus raises stroke volume through a stronger contraction tied to preload. The idea that stretch would reduce stroke volume isn’t accurate in normal physiology, and venous return mainly changes stroke volume by altering preload rather than increasing afterload.