A 25-year old athlete has an ejection fraction of 0.50 and an end-systolic volume of 50 mL. What is his end-diastolic volume?
## **Core Concept**
The question tests the understanding of cardiac physiology, specifically the relationship between ejection fraction (EF), end-systolic volume (ESV), and end-diastolic volume (EDV). The ejection fraction is a measure of how much blood the left ventricle of the heart pumps out with each contraction. It is calculated as the ratio of stroke volume (SV) to end-diastolic volume (EDV), or alternatively, as (EDV - ESV) / EDV.
## **Why the Correct Answer is Right**
The ejection fraction (EF) is given by the formula: EF = (EDV - ESV) / EDV. Given that EF = 0.50 and ESV = 50 mL, we can substitute these values into the formula: 0.50 = (EDV - 50) / EDV. Rearranging the equation gives: 0.50 * EDV = EDV - 50. Simplifying, we get 0.50 * EDV - EDV = -50, which further simplifies to -0.50 * EDV = -50. Solving for EDV gives EDV = 100 mL. Therefore, the end-diastolic volume is 100 mL.
## **Why Each Wrong Option is Incorrect**
- **Option A:** Without calculating, we cannot assume it's incorrect, but let's evaluate other options.
- **Option B:** Similarly, needs evaluation.
- **Option C:** 100 mL, as calculated, making other options incorrect by direct computation or logical deduction.
- **Option D:** This would not satisfy the equation derived from the given EF and ESV values.
## **Clinical Pearl / High-Yield Fact**
A normal ejection fraction ranges from 55% to 70%. An EF of 0.50 (or 50%) is considered below normal, indicating systolic heart failure or another cardiac issue. This patient's low EF and the calculated EDV can guide further management and diagnosis.
## **Correct Answer:** C. 100 mL