The S3 heart sound occurs as the mitral valve opens and allows blood to fill the left ventricle passively. The sound happens as a result of blood striking the left ventricle during early diastole. An ...

A third heart sound, or S3, is a low-frequency, extra heart sound that may be heard with a stethoscope right after the normal S1 and S2 heart sounds. S1 and S2 are the "lub-dub" sounds of a heartbeat ...

An S4 heart sound is a low-pitched sound that occurs toward the end of the diastole. In some cases, an underlying health condition, often one affecting the left ventricle, may cause the S4 heart sound ...