**Core Concept:** Reversed Coarctation is a rare congenital heart defect where the descending aorta is hypoplastic and the brachiocephalic trunk and pulmonary artery are dilated. This results in a mismatch between the blood supply to the upper and lower body. In normal anatomy, the aorta is the largest artery and has a high pressure, while the pulmonary artery has a low pressure. In reversed coarctation, the pulmonary artery becomes the largest artery due to dilatation, while the descending aorta is hypoplastic and has a low pressure.

**Why the Correct Answer is Right:** Reversed Coarctation is seen in the context of hypoplastic left heart syndrome (HLHS). In HLHS, the left ventricle is unable to perfuse the systemic circulation due to severe left ventricular hypoplasia, and the right ventricle takes over the role of the left ventricle. As a result, the pulmonary artery dilates to match the increased workload, while the descending aorta is hypoplastic due to the reduced demand for oxygenated blood. This mismatch between the diameter of the pulmonary artery and the descending aorta leads to Reversed Coarctation.

**Why Each Wrong Option is Incorrect:**

A. Pulmonary stenosis (PS) is a narrowing of the pulmonary valve and the right ventricular outflow tract, which results in increased resistance and dilatation of the pulmonary artery. It is not associated with Reversed Coarctation.

B. Tetralogy of Fallot (ToF) is a congenital heart defect characterized by pulmonary artery stenosis, ventricular septal defect, overriding aorta, and right ventricular hypertrophy. While pulmonary artery dilatation is present, it does not cause Reversed Coarctation.

C. Coarctation of Aorta (COA) is a narrowing of the aorta, usually between the aortic arch and the descending aorta. Unlike Reversed Coarctation, COA does not result from a mismatch between pulmonary artery and descending aorta diameters.

D. Hypoplastic left heart syndrome (HLHS) is a severe form of cyanotic congenital heart defect characterized by severely reduced left ventricular output. In HLHS, the right ventricle takes over the role of the left ventricle, leading to Reversed Coarctation due to the mismatch between pulmonary artery and descending aorta diameters.

**Clinical Pearl:** Hypoplastic left heart syndrome (HLHS) is a critical condition that requires prompt diagnosis and intervention to prevent severe complications such as congestive heart failure, pulmonary vascular resistance elevation, and impaired oxygenation. Early recognition and intervention are essential in improving the survival rate of affected infants.