Question

What is the likely cause of central cyanosis and oligemic lung fields in a neonate with a normal sized heart?

• A. Pulmonary atresia
• B. TOF
• C. TGA
• D. VSD

Hint:

Cyanosis with oligemic lungs and a normal sized heart in a neonate suggests TOF.

Answer 1

The Correct Option is B

Step 1: Understanding the Question:
A neonate has central cyanosis, oligemic (reduced blood flow) lung fields on X-ray, and a normal sized heart. We need the diagnosis that matches all three findings together.

Step 2: Key Formula or Approach:
Cyanotic congenital heart disease can be sorted by two X-ray clues: heart size, and whether the lung fields look full (plethoric, more blood flow) or empty (oligemic, less blood flow). Matching these clues narrows the diagnosis quickly.

Step 3: Detailed Explanation:
Tetralogy of Fallot (TOF) causes obstruction to blood flow out of the right ventricle into the lungs (pulmonary stenosis), so less blood reaches the lungs and the fields look oligemic. Because the right ventricle pumps against this obstruction rather than dilating hugely, the heart size on X-ray usually stays normal, giving the classic boot shaped but normal sized heart. This matches the question exactly.
Pulmonary atresia usually shows a more abnormal heart silhouette, and depending on the tricuspid valve findings, the heart is often enlarged rather than staying a normal size.
Transposition of the great arteries (TGA) generally shows increased, plethoric lung fields, not oligemic ones, since the parallel circulation still pushes a large blood volume through the lungs, and the heart classically looks like an "egg on a string," a different shape from a normal sized heart.
Ventricular septal defect (VSD) is a left to right shunt lesion. It causes plethoric lung fields with an enlarged heart from volume overload, and it does not cause cyanosis on its own unless it has progressed to Eisenmenger physiology, which is not the picture here in a neonate.

Step 4: Final Answer:
Cyanosis with oligemic lungs and a normal sized heart is the classic picture of Tetralogy of Fallot. \[ \boxed{\text{TOF}} \]