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

This question uses two chest X-ray clues, heart size and lung field blood flow, to sort out cyanotic heart disease in a neonate. Check each option against both clues.

1. Pulmonary atresia: Lung fields are oligemic since little blood reaches the lungs, but the heart is usually enlarged because of the abnormal tricuspid valve and right atrium, not normal sized.
2. TOF: Right ventricular outflow obstruction restricts blood flow to the lungs, giving oligemic fields, while the heart itself stays close to normal size since it does not dilate much. This fits both clues in the question.
3. TGA: The parallel circulation keeps pushing a large volume of blood through the lungs, so the fields look plethoric, not oligemic, and the heart classically looks like an egg on a string.
4. VSD: A left to right shunt causes plethoric fields and an enlarged heart from extra blood volume, and it is not a cyanotic lesion at this stage.

Only TOF gives cyanosis, oligemic fields, and a normal sized heart together.

Let's summarize:

• Oligemic lungs plus a normal sized heart in a cyanotic neonate points to TOF.
• Pulmonary atresia usually enlarges the heart, while TGA and VSD both cause plethoric, not oligemic, lung fields.

So the diagnosis is TOF.