A newborn with hepatomegaly, tachycardia, and feeding problems is most likely experiencing which condition?

The condition being described—hepatomegaly, tachycardia, and feeding problems in a newborn—is most indicative of Congestive Heart Failure (CHF). This is because CHF in neonates can lead to a backlog of blood flow, causing the liver to become engorged, resulting in hepatomegaly. Furthermore, due to the heart's inability to pump effectively, tachycardia occurs as the body attempts to maintain adequate circulation. Feeding problems can arise due to both the increased work of breathing associated with heart failure and the reduced energy availability for feeding, which often leads to poor feeding habits or difficulty in feeding.

Conditions like Tetralogy of Fallot, Ventricular Septal Defect, and Patent Ductus Arteriosus are specific types of congenital heart defects; while they can lead to complications, they do not typically present with the specific combination of symptoms mentioned in the question. These defects may cause cyanosis or other symptoms related to blood flow but are less directly associated with hepatomegaly and feeding difficulties as seen in CHF. Thus, the symptoms presented are most consistent with a diagnosis of Congestive Heart Failure in the newborn.