Paradoxical splitting of S2 is most characteristic of which condition?

• A. Hypertrophic cardiomyopathy
• B. Mitral stenosis
• C. Aortic stenosis
• D. Aortic regurgitation

Answer: (C)

Paradoxical splitting of S2 happens when the aortic component (A2) closes later than the pulmonic component (P2), so the order of the two sounds reverses on expiration. This occurs because the left ventricle takes longer to eject blood, delaying A2. On expiration the delay is still present and you hear P2 before A2, creating a split that may be audible; on inspiration the normal delay of P2 reduces the difference and the split may disappear. Severe aortic stenosis fits this pattern because it prolongs LV outflow and delays A2.

Other conditions listed don’t typically produce this characteristic splitting pattern: mitral stenosis and aortic regurgitation have different auscultatory cues (opening snap or diastolic murmurs, and wide pulse pressure with a softer A2, respectively), and hypertrophic cardiomyopathy isn’t the classic cause of paradoxical S2 splitting.