Which condition is most classically associated with an opening snap heard on auscultation?

• A. Mitral stenosis
• B. Aortic stenosis
• C. Mitral regurgitation
• D. Pulmonary embolism

Answer: (A)

Opening snap is an audible clue that the mitral valve is not moving freely. It occurs when the stiff, thickened mitral valve leaflets abruptly open at the start of diastole, producing a high-pitched snap after S2. This is most characteristic of mitral stenosis, commonly due to rheumatic disease, where the valve is restricted and leaflets resist opening until a point in early diastole when they finally snap open. The opening snap is often followed by a low-pitched diastolic rumble heard best at the apex with the patient in the left lateral decubitus position. The interval after S2 and the snap tends to shorten as stenosis becomes more severe.

This finding is not typical for aortic stenosis (a systolic murmur), mitral regurgitation (a holosystolic murmur), or pulmonary embolism (no opening snap).