Auscultation: Heart Sounds
Closure of the heart valves is responsible for normal heart sounds.
S1 = Pressure from the contracting left ventricle, exceeds left atrial pressure closing the mitral valve.
Early Systolic Ejection click: may be present in some pathologic conditions with the closing of the aortic valve.
S2 = The aortic valve shutting results in the second heart sound. The valve closes as the left ventricle pressure drops below the aortic pressure.
O.S = Opening Snap = mitral stenosis, as the mitral valve opens as the left ventricle relaxes and its pressure falls below that of the left atrial pressure.
S3 = 3rd heart sound = May occur in children and young adults, Marked by a period of rapid ventricular filling as blood flows early in diastole from left atrium to left ventricle.
S4 = 4th heart sound = Not often heard in normal adults. Marks atrial contraction. It immediatly preceeds S1 of the next beat.
Bates, Barbara. 1974. A Guide to Physical Examination. J.B. Lippincott Company, Toronto.