Preload of heart reduced by:
**Core Concept**
The preload of the heart refers to the initial stretching of the cardiac myocytes prior to contraction, which is directly related to the volume of blood in the ventricles at the end of diastole. It is a critical determinant of cardiac performance, as it affects the stroke volume and cardiac output.
**Why the Correct Answer is Right**
The preload of the heart is reduced by factors that decrease the volume of blood in the ventricles at the end of diastole. This can be achieved through increased venous return to the heart, which can be enhanced by factors such as increased sympathetic tone, decreased venous capacitance, or increased intrathoracic pressure. On the other hand, factors that decrease venous return, such as increased abdominal pressure, decreased blood volume, or increased venous capacitance, can also reduce preload. In this context, **Option D: Increased abdominal pressure** is correct because it can decrease venous return to the heart, thereby reducing the preload.
**Why Each Wrong Option is Incorrect**
* **Option A:** This option is not directly related to the reduction of preload.
* **Option B:** This option is not a relevant factor in reducing preload.
* **Option C:** This option is not a correct answer, as it does not directly relate to the reduction of preload.
**Clinical Pearl / High-Yield Fact**
A key point to remember is that factors that decrease venous return to the heart, such as increased abdominal pressure or decreased blood volume, can reduce cardiac preload and lead to decreased cardiac output.
**Correct Answer: D. Increased abdominal pressure**