The S1 heart sound, also known as the "lub" sound, is the first sound heard in the cardiac cycle. It is produced by the closure of the atrioventricular (AV) valves, specifically the mitral and tricuspid valves, at the beginning of systole.
The S1 sound is best heard at the apex of the heart, using a stethoscope. It is usually louder than the second heart sound (S2) and is often described as a sharp, crisp sound. s1 and s1 heart sounds
A booming or accentuated S1 suggests that the mitral or tricuspid valve leaflets are unusually far apart at the moment ventricular contraction begins, forcing them to slam shut with greater force. The S1 heart sound, also known as the
Specifically, S1 is produced by the near-simultaneous closure of two valves: It is usually louder than the second heart
Although the mitral and tricuspid valves close almost simultaneously, they do not close at exactly the same time. In a healthy individual, the . The time difference is normally less than 30 milliseconds (ms). At this interval, the human ear perceives a single, clean "Lub" sound.
To properly assess S1, use the of your stethoscope, as S1 is a relatively high-frequency sound. The best listening posts are the apex (fifth intercostal space, midclavicular line) for the mitral component and the lower left sternal border for the tricuspid component.