How would you describe the pulmonary vasculature, and what does this imply?
The vessels are congested and enlarged and tortuous without overt features of pulmonary oedema. The term active congestion or pulmonary plethora can be used. It implies increased right cardiac output (usually >2.5 times normal) and usually a left to right shunt.
What is the most likely diagnosis? Why?
A ventriculoseptal defect is the most likely diagnosis, as it is by far the most common cause of a left to right shunt, especially when the cardiac silhouette (other than being prominent) is otherwise normal.
What clinical information is particularly important in assessing congenital heart defects? What would the case be in this patient?
Whether or not the patient is cyanotic. In a left to right shunt, the patient would not be cyanotic.
Chest x-ray demonstrates prominent pulmonary vasculature (active congestion) without pleural effusions or convincing consolidation. The heart is prominent.