Heart Sounds

Heart sounds are produced by pressure changes and valve movement during the cardiac cycle. S1, the first heart sound, occurs primarily when the mitral and tricuspid atrioventricular valves close as ventricular systole begins. S2 occurs primarily when the aortic and pulmonic semilunar valves close at the end of systole. During inspiration, the pulmonic component may close later than the aortic component, creating a normally split S2. An extra sound or murmur is not interpreted in isolation. S3 is an early-diastolic filling sound; it can be normal in children, young adults, pregnancy, and high-flow states, but a new S3 in many adults suggests ventricular dysfunction or volume overload. S4 occurs late in diastole when atrial contraction pushes blood into a stiff ventricle and is generally abnormal. Atrial fibrillation eliminates effective atrial contraction, so S4 is absent in atrial fibrillation. A murmur is caused by turbulent blood flow rather than simple valve closure. It may reflect stenosis, regurgitation, congenital disease, altered hemodynamics, or another structural problem; it may also be innocent. A quiet murmur is not automatically benign, and loudness alone does...