Heart Sounds S1, S2, S3, S4

When does the S1 heart sound occur?

At the beginning of systole (end of diastole). The "lub" in lub-dub.

What causes the S1 heart sound?

Related to the closure of the mitral and tricuspid valves.

When does the S2 heart sound occur?

At the beginning of Diastole (end of systole). The "dub" in lub-dub.

What causes the S2 heart sound?

Related to the closure of the aortic and pulmonic valves.

When does the S3 heart sound occur?

Low frequency sound in early diastole,

120 to 180 ms after S2

Why does the S3 heart sound occur?

Results from increased atrial pressure leading to increased flow rates.

Causes of the S3 heart sound?

The most common cause of the S3 is congestive heart failure, less common is valvular regurgitation and left to right shunts.

When does the S4 heart sound occur?

Low frequency sound just after atrial contraction ("atrial kick") at the end of diastole and immediately before S1.

Why does the S4 heart sound occur?

Seen in patients with stiffened left ventricles, resulting from conditions such as hypertension, aortic stenosis, ischemic or hypertrophic cardiomyopathy. In patient with mitral regurgitation, suggestive of acute onset of regurgitation due to the rupture of the chorda tendinae that anchor the Valvular leaflets.

During S1 which valve closes first? why

The mitral valve closes before the tricuspid valve.

During S2 which valve closes first? why

The aortic valve closes before the pulmonic valve.