Which of the following would cause a decrease in stroke volume, when compared with the normal resting value?
**Core Concept**
Decrease in stroke volume can occur due to various factors affecting the heart's ability to pump blood. This can be influenced by changes in preload, afterload, contractility, or heart rate. The Frank-Starling mechanism explains how stroke volume increases with increased ventricular preload.
**Why the Correct Answer is Right**
A decrease in stroke volume occurs when the heart's ability to pump blood is impaired. In this scenario, **Option C: Hypovolemia** is the correct answer. Hypovolemia refers to a decrease in blood volume, which reduces the ventricular preload. As a result, the heart muscle contracts with a lower than normal volume, leading to a decrease in stroke volume. This is because the Frank-Starling mechanism is impaired, and the heart cannot generate the same force of contraction with a reduced preload.
**Why Each Wrong Option is Incorrect**
* **Option A:** Vasopressin is a vasoconstrictor that increases blood pressure by constricting blood vessels. It does not directly affect stroke volume, so it is not the correct answer.
* **Option B:** Bradycardia, or a slow heart rate, can actually increase stroke volume due to the increased diastolic filling time, which allows for more blood to be pumped with each beat.
**Clinical Pearl / High-Yield Fact**
The Frank-Starling mechanism is a critical concept in hemodynamics. Remember that an increase in ventricular preload leads to an increase in stroke volume, while a decrease in preload leads to a decrease in stroke volume.
**Correct Answer:** C. Hypovolemia.