Atrial septal defect vs Ventricular septal defect
How to tell Atrial septal defect and Ventricular septal defect apart when a board question makes them look alike.
ASD: wide fixed split S2; VSD: harsh holosystolic murmur at the lower left sternal border.
Side by side
Fixed wide split S2 with systolic flow murmur from increased right-sided volume.
Harsh holosystolic murmur at the lower left sternal border from LV-to-RV systolic flow.
Atrial-level left-to-right shunt chronically increases right atrial and right ventricular volume.
Ventricular-level pressure gradient drives systolic left-to-right shunt, with pulmonary overcirculation if large.
ASD: wide fixed split S2, right axis deviation, incomplete right bundle branch block (rsR' in V1), and right atrial/ventricular enlargement on echo. The most common type is ostium secundum; ostium primum is associated with Down syndrome and atrioventricular canal defects.
VSD: holosystolic LLSB murmur with a palpable thrill, left atrial and left ventricular enlargement on echo, and a louder murmur in smaller (restrictive) defects. VSD is the most common congenital cardiac defect; large defects cause Eisenmenger physiology if not repaired in infancy.
The trap
Both are initially left-to-right shunts and both can lead to Eisenmenger if large and unrepaired.
Watch it explained
The repair move
Decide ASD versus VSD by S2 splitting first, then murmur character. A wide fixed split S2 names ASD even when the flow murmur is hard to hear. A holosystolic LLSB murmur with a thrill names VSD even when S2 sounds normal. Both can progress to Eisenmenger syndrome (reversed right-to-left shunt with cyanosis and clubbing) if large and unrepaired. ASD repair is indicated for Qp:Qs above 1.5 or right heart enlargement. Most small muscular VSDs close spontaneously; large defects causing failure to thrive or pulmonary hypertension need closure in infancy.
Try a free question
CoreA child has a fixed, wide split S2 with a systolic ejection murmur from increased flow across the pulmonic valve. Which septal defect is most likely?
Show answer and explanation
Answer: A. Atrial septal defect. ASD classically causes a fixed split S2 due to persistent increased right-sided flow.
Why the other choices are tempting
- B. VSD causes a harsh holosystolic murmur at the lower left sternal border.
- C. PDA causes a continuous machinery murmur.
- D. Aortic stenosis causes systolic ejection murmur radiating to carotids.
- E. Mitral regurgitation is holosystolic at the apex radiating to axilla.
Flashcards
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What is the fastest separator for Atrial septal defect vs Ventricular septal defect?
ASD: wide fixed split S2; VSD: harsh holosystolic murmur at the lower left sternal border.
What clue should make you choose Atrial septal defect?
Fixed wide split S2 with systolic flow murmur from increased right-sided volume.
Quick answers
What is the fastest way to tell Atrial septal defect from Ventricular septal defect?
ASD: wide fixed split S2; VSD: harsh holosystolic murmur at the lower left sternal border.
What is the key clue for Atrial septal defect?
Fixed wide split S2 with systolic flow murmur from increased right-sided volume.
What is the key clue for Ventricular septal defect?
Harsh holosystolic murmur at the lower left sternal border from LV-to-RV systolic flow.
What is the common trap with Atrial septal defect vs Ventricular septal defect?
Both are initially left-to-right shunts and both can lead to Eisenmenger if large and unrepaired.