What is the typical chest X-ray finding in a child with tetralogy of Fallot?

In children with tetralogy of Fallot, the typical chest X-ray finding is decreased pulmonary vascular markings. This is largely due to the effects of the structural defects associated with this congenital heart disease, which include pulmonary stenosis, ventricular septal defect, overriding aorta, and right ventricular hypertrophy.

The decreased pulmonary vascular markings occur because the right ventricle is not able to pump efficiently into the pulmonary artery due to the stenosis, leading to reduced blood flow to the lungs. This insufficient pulmonary blood flow results in less visibility of the pulmonary arteries and vascular markings on a chest X-ray.

In contrast, increased pulmonary vascular markings would indicate increased blood flow to the lungs, which is not typical in tetralogy of Fallot. Normal vascular markings would suggest normal pulmonary blood flow, and cardiomegaly is often associated with conditions that involve volume overload or heart failure, which is also not a characteristic finding in patients with tetralogy of Fallot. Therefore, decreased pulmonary vascular markings accurately reflects the underlying pathology in tetralogy of Fallot.