Third heart sound

Third heart sound ; ;
Synonyms	S3 ;
Specialty	Cardiology ; ; ; ; ; ; ;
Diagnosis	Auscultation ; ; ; ; ; ; ;

File:Diagram of the human heart (cropped).svg

Diagram of the human heart (cropped)

The third heart sound (S3) is a low-frequency sound that occurs early in diastole during the rapid filling phase of the ventricles. It is often associated with increased volume of blood within the ventricle and can be a normal finding in children and young adults. However, in older adults, it may indicate the presence of heart failure or other cardiac conditions.

Physiology[edit]

The third heart sound is produced by the rapid deceleration of blood flow into the left ventricle from the left atrium. This sound is best heard with the bell of the stethoscope at the apex of the heart with the patient in the left lateral decubitus position. It is often described as a "dull" or "thudding" sound.

Clinical Significance[edit]

In young individuals, an S3 can be a normal variant and is often referred to as a "physiological S3." In older adults, an S3 is more likely to be pathological and may indicate conditions such as:

Diagnosis[edit]

The presence of an S3 can be detected through auscultation during a physical examination. It is important to differentiate an S3 from other heart sounds, such as the fourth heart sound (S4), which occurs just before the first heart sound (S1) and is associated with a stiff or hypertrophic ventricle.