A 30-year-old woman with dyspnea on exertion has a systolic ejection murmur at the left sternal border and fixed splitting of S2. Echocardiography shows right ventricular volume overload with a left-to-right shunt. What is the most likely underlying diagnosis?

• A Ventricular septal defect
• B Patent ductus arteriosus
• C Partial anomalous pulmonary venous return
• D Ostium secundum atrial septal defect ✓

Explanation

Ostium secundum ASD classically presents with fixed splitting of S2 (delayed pulmonary valve closure unaffected by respiration due to equalized atrial pressures), systolic ejection murmur at left sternal border (increased flow across pulmonary valve), and right ventricular volume overload on echo. VSD causes a harsh holosystolic murmur. PDA gives a continuous murmur.

Reference: Harrison's Principles of Internal Medicine, 21st ed.

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Written and medically reviewed by the StethoPrep medical team.