VSD vs ASD
How to tell VSD and ASD apart when a board question makes them look alike.
Step 2 CK pairs are in open beta while clinical review finishes. Spot an issue? Tell us.
Fixed wide split S2 points to ASD, not isolated VSD.
Side by side
A harsh holosystolic murmur at the left lower sternal border with possible thrill favors ventricular septal defect.
Fixed wide split S2 with systolic flow murmur at the pulmonic area favors atrial septal defect.
Left-to-right shunting across the ventricular septum increases pulmonary blood flow and can raise pulmonary vascular resistance over time.
Left-to-right shunting across the atrial septum causes chronic right-sided volume overload.
Echocardiography shows septal defect in the ventricular wall with increased Qp:Qs ratio above 1.5:1 in significant shunts.
Echocardiography shows atrial-level communication with right atrial and right ventricular dilation; secundum ASD often has increased pulmonary flow without cyanosis in childhood.
The trap
Flow murmurs lead to overcalling VSD when the key clue is a fixed split second heart sound. Missing ASD delays closure consideration and long-term right-heart protection.
The repair move
Next best step: obtain transthoracic echocardiography to define defect type and shunt size, monitor growth and pulmonary pressures, and refer for transcatheter or surgical closure when ASD causes right-heart dilation or when VSD remains hemodynamically significant despite medical therapy. Use diuretics such as furosemide 1 mg/kg/dose for heart-failure symptoms in large VSD while awaiting repair.
Try a free question
CoreA 6-year-old boy has a fixed wide split S2 and mild exercise intolerance. What is the next best step in management?
Show answer and explanation
Answer: A. Transthoracic echocardiography for suspected ASD. Fixed split S2 strongly suggests ASD, and echocardiography is the diagnostic next step.
Why the other choices are tempting
- B. Wrong. Prostaglandin is for ductal-dependent neonatal lesions, not stable school-age murmurs.
- C. Wrong. No infectious signs indicate endocarditis therapy.
- D. Wrong. Structural murmurs require targeted evaluation.
- E. Wrong. Medication without diagnosis is inappropriate.
Flashcards
Tap a card to flip it.
Which auscultatory finding is the fastest discriminator for ASD in children?
A fixed wide split S2.
What murmur quality is classic for VSD?
A harsh holosystolic murmur at the left lower sternal border.
Quick answers
What is the fastest way to tell VSD from ASD?
Fixed wide split S2 points to ASD, not isolated VSD.
What is the key clue for VSD?
A harsh holosystolic murmur at the left lower sternal border with possible thrill favors ventricular septal defect.
What is the key clue for ASD?
Fixed wide split S2 with systolic flow murmur at the pulmonic area favors atrial septal defect.
What is the common trap with VSD vs ASD?
Flow murmurs lead to overcalling VSD when the key clue is a fixed split second heart sound. Missing ASD delays closure consideration and long-term right-heart protection.