If end-diastolic volume decreases while end-systolic volume remains constant, which of the following statements is correct regarding stroke volume and ejection fraction?

• A. Stroke volume increases; ejection fraction increases.
• B. Stroke volume decreases; ejection fraction increases.
• C. Stroke volume decreases; ejection fraction typically decreases.
• D. Stroke volume stays the same; ejection fraction decreases.

Answer: (C)

Stroke volume is the amount of blood ejected per beat, given by SV = EDV − ESV. If the end-diastolic volume (the filling before contraction) decreases while the end-systolic volume (the amount left after contraction) stays the same, the difference shrinks, so stroke volume falls.

Ejection fraction is the fraction of the filled ventricle that is ejected, EF = SV/EDV. With EDV reduced and ESV unchanged, the numerator (SV) decreases and the denominator (EDV) also decreases, but the change causes the ratio to drop. In algebra terms, EF = (EDV − ESV)/EDV = 1 − (ESV/EDV); with ESV constant and EDV falling, that ratio ESV/EDV increases, so EF decreases.

So the scenario results in stroke volume decreasing and ejection fraction decreasing.