Question:medium
What is the differentiating feature of an atrial septal defect (ASD) from a ventricular septal defect (VSD) on chest X-ray?
What is the differentiating feature of an atrial septal defect (ASD) from a ventricular septal defect (VSD) on chest X-ray?
Show Hint
In which defect does the extra volume bypass the left atrium?
Updated On: Jun 24, 2026
- Pulmonary hypertension
- Absence of left atrial enlargement
- Pulmonary congestion
- Aortic shadow
Show Solution
The Correct Option is B
Solution and Explanation
To separate ASD from VSD on a plain film, ask which cardiac chambers carry the extra volume, because the X-ray simply reflects which chambers dilate.
Pulmonary plethora, pulmonary hypertension and pulmonary congestion are common to any large left-to-right shunt, so they appear in both lesions and cannot be used to tell them apart. The aortic shadow is not a distinguishing feature either.
The decisive clue is the left atrium. In a VSD the recirculated blood travels through the lungs and floods the left atrium and left ventricle, producing left atrial enlargement. In an ASD the defect sits at the atrial level, so the surplus blood is shunted straight into the right atrium and right ventricle and never overloads the left atrium. A normal-sized left atrium in the presence of a left-to-right shunt therefore points to ASD rather than VSD.
\[\boxed{\text{Absence of left atrial enlargement}}\]
Pulmonary plethora, pulmonary hypertension and pulmonary congestion are common to any large left-to-right shunt, so they appear in both lesions and cannot be used to tell them apart. The aortic shadow is not a distinguishing feature either.
The decisive clue is the left atrium. In a VSD the recirculated blood travels through the lungs and floods the left atrium and left ventricle, producing left atrial enlargement. In an ASD the defect sits at the atrial level, so the surplus blood is shunted straight into the right atrium and right ventricle and never overloads the left atrium. A normal-sized left atrium in the presence of a left-to-right shunt therefore points to ASD rather than VSD.
\[\boxed{\text{Absence of left atrial enlargement}}\]
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