**Core Concept**
Eisenmenger syndrome is a type of pulmonary arterial hypertension (PAH) characterized by a reversal of the left-to-right shunt in congenital heart defects, leading to cyanosis and right-to-left shunting. This results from the progressive increase in pulmonary vascular resistance, causing a decrease in pulmonary blood flow and an increase in systemic venous blood flow through the defect.

**Why the Correct Answer is Right**
The correct answer is an exception to the statement. Eisenmenger syndrome is indeed characterized by the following features:
- **Reversal of left-to-right shunt**: The left-to-right shunt is reversed due to the increase in pulmonary vascular resistance.
- **Cyanosis**: The cyanosis is due to the right-to-left shunting of blood through the defect.
- **Right-to-left shunting**: The right-to-left shunting occurs due to the reversal of the left-to-right shunt.

**Why Each Wrong Option is Incorrect**
* **Option A:** This option is incorrect because Eisenmenger syndrome is not typically associated with a decrease in systemic vascular resistance.
* **Option B:** This option is incorrect because Eisenmenger syndrome is not typically associated with a decrease in pulmonary blood flow.
* **Option C:** This option is incorrect because Eisenmenger syndrome is not typically associated with a decrease in pulmonary vascular resistance.
* **Option D:** This option is incorrect because Eisenmenger syndrome is not typically associated with a decrease in systemic venous blood flow through the defect.

**Clinical Pearl / High-Yield Fact**
Eisenmenger syndrome is a progressive condition that can lead to significant morbidity and mortality if not managed promptly. The management of Eisenmenger syndrome involves addressing the underlying congenital heart defect, managing symptoms, and preventing complications such as pulmonary embolism and stroke.

**Correct Answer: A.**