Second Heart Sounds Opening Snap and Second Heart Sound An opening snap occurring early in diastole along with a single second heart sound can mimic a split second heart sound.An opening snap is caused by thickened valve leaflets. When they open it produces a snapping sound.The more severe the thickening the earlier in diastole the opening snap occurs. In this example you are hearing an opening snap which occurs 75 milliseconds after the start of the second heart sound. play pause Position: Mitral Chestpiece: Diaphragm Maneuver: Supine Phonocardiogram Cardiac Animation Table of Contents 1Second Heart Sound - Physiologically Split #2 2Second Heart Sound with Persistent Splitting 3Second Heart Sound with Fixed Splitting 4Second Heart Sound: Fixed Splitting, Increased Aortic Intensity 5Second Heart Sound: Fixed Splitting, Decreased Aortic Intensity 6Second Heart Sound and Late Systolic Click 7Second Heart Sound and a Tumor Plop 8Opening Snap and Second Heart Sound Practice Drill