A 45-year-old woman with rheumatic heart disease presents with progressive exertional dyspnea. Auscultation reveals an opening snap followed by a low-pitched rumbling diastolic murmur best heard at the apex with the patient in the left lateral decubitus position. The shorter the interval between S2 and the opening snap, the more likely the mitral valve area is:
- A Severely reduced (< 1.0 cm²) ✓
- B Mildly reduced (1.5–2.0 cm²)
- C Within normal limits (> 4 cm²)
- D Unrelated to the S2-OS interval
Correct answer: A. Severely reduced (< 1.0 cm²)
Explanation
In mitral stenosis, the S2-to-opening-snap (OS) interval reflects left atrial pressure: a shorter interval indicates higher left atrial pressure, which in turn correlates with more severe (smaller) mitral valve area. A very short S2-OS interval (< 60 ms) implies critical stenosis with a valve area below 1 cm². Mild stenosis with a larger valve area is associated with a longer S2-OS interval because left atrial pressure is only modestly elevated. The interval is therefore directly related to disease severity, not independent of it.
Reference: Harrison's Principles of Internal Medicine, 21st ed.
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Written and medically reviewed by the StethoPrep medical team.