If afterload increases, what happens to stroke volume and end-systolic volume?

• A. Stroke volume increases and end-systolic volume decreases when afterload rises.
• B. Stroke volume typically decreases and end-systolic volume increases when afterload rises.
• C. Stroke volume remains unchanged and end-systolic volume remains unchanged.
• D. Stroke volume increases, and end-systolic volume increases.

Answer: (B)

Afterload is the pressure the ventricle must overcome to eject blood. When afterload increases, the ventricle has to generate a higher pressure to open the aortic valve. If preload and contractility stay the same, the heart ejects less blood each beat, so stroke volume falls. Because less blood is ejected, more remains in the ventricle after systole, causing the end-systolic volume to rise. Since SV = EDV − ESV, a drop in SV (with EDV relatively unchanged) corresponds to an increase in ESV. In real life, changes in venous return can shift EDV, but the typical response to higher afterload is decreased stroke volume and increased end-systolic volume.