The S1 heart sound is a low-frequency sound that occurs at the beginning of systole, which is the phase of the cardiac cycle when the heart muscle contracts. It is produced by the closure of the atrioventricular (AV) valves, specifically the mitral and tricuspid valves. The S1 sound is often described as a "lub" or "dup" sound, and it is typically louder than the second heart sound (S2).
S1 = Closure of Mitral + Tricuspid valves. M1 always occurs slightly before T1 (by approximately 20���30 milliseconds), though they are usually heard as a single sound. s1 heart sound
Contrary to popular belief, the heart sound is not the blood rushing through the chambers, nor is it the muscle contracting. Specifically, it is the sound generated by the sudden closure of the atrioventricular (AV) valves ���the mitral (M1) and tricuspid (T1) valves. The S1 heart sound is a low-frequency sound
A normal S1 heart sound has the following characteristics: S1 = Closure of Mitral + Tricuspid valves