A 28-year-old woman with rheumatic mitral stenosis has a loud S1 and an opening snap. Over successive years her A2 to opening snap interval shortens while the murmur lengthens. What does this change indicate?
- A The left atrial pressure has fallen
- B The mitral stenosis has become more severe ✓
- C Coexistent aortic regurgitation has developed
- D The valve has become more calcified and immobile
Correct answer: B. The mitral stenosis has become more severe
Explanation
The B2 to opening snap interval is inversely proportional to left atrial pressure: higher LA pressure closes the mitral valve earlier in diastole, shortening the interval. B shorter B2-OS interval therefore signals worsening mitral stenosis, along with a longer diastolic rumble extending toward the second sound. Calcification would actually reduce the intensity of S1 and soften the snap, so option D contradicts the preserved loud S1 described.
Reference: Harrison's Principles of Internal Medicine, 21st ed.
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Written and medically reviewed by the StethoPrep medical team.