A 30-year-old woman with rheumatic mitral stenosis has been followed annually. The interval between A2 and the opening snap on phonocardiography has shortened from 110 ms to 65 ms over three years. What does this change indicate?
- A The mitral stenosis has become more severe, with rising left atrial pressure ✓
- B The mitral stenosis has improved as the valve calcified further
- C Left ventricular systolic function has deteriorated
- D Coexisting aortic regurgitation has developed
Correct answer: A. The mitral stenosis has become more severe, with rising left atrial pressure
Explanation
The A2 to opening snap interval is inversely proportional to left atrial pressure. Higher LA pressure causes the mitral valve to snap open earlier in diastole, shortening the interval. An interval under 70 ms indicates severe mitral stenosis, whereas an interval over 120 ms suggests mild disease. Calcification would not improve the gradient, and the OS disappears when the valve becomes heavily calcified and immobile. Left ventricular function and aortic regurgitation do not determine when the stenotic valve opens.
Reference: Harrison's Principles of Internal Medicine, 21st ed.
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