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Recording provided by Jules Constant, MD.

Mitral Valve Opening Snap
Sound is that of S 1 -A 2 -OS with a relatively long A 2 -OS interval. The opening snap, most commonly caused by mitral stenosis, is thought to be caused by abrupt downward bulging (snapping) of the anterior leaflet as left ventricular pressure drops below left atrial pressure during diastole. A 2 -OS can be distinguished from a split S 2 by dynamic maneuvers (OS intensity increases with inspiration, A 2 -OS interval widens with standing), a triple S 2 (ie, A 2 -P 2 -OS), and a louder volume at the apex.