The presence of an opening snap on auscultation is most characteristic of which condition?

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

Answer: (A)

Opening snap is produced when the mitral valve leaflets abruptly separate as they are forced open in early diastole. This occurs in mitral stenosis, where the valve is thickened and rigid, so the leaflets stay closed most of diastole and then snap open once atrial pressure overcomes the stiff valve. The sound is best heard at the apex, with the patient in the left lateral position, just after S2 and often followed by a low-pitched diastolic rumble from the narrowed orifice. This finding points to mitral stenosis (often rheumatic in origin) rather than to mitral regurgitation, aortic stenosis, or pulmonary hypertension, which have different auscultatory patterns.