Heart sound

In medicine, heart sounds are the "sounds heard over the cardiac region produced by the functioning of the heart. There are four distinct sounds: the first occurs at the beginning of systole and is heard as a "lubb" sound; the second is produced by the closing of the aortic valve and pulmonary valve and is heard as a "dupp" sound; the third is produced by vibrations of the ventricular walls when suddenly distended by the rush of blood from the heart atria; and the fourth is produced by atrial contraction and ventricular filling."

Normal heart sounds

The location of the heart below the thoracic wall.

S₁

S₁, which originates from closure of the mitral and tricuspid valves is normally louder than S₂ at the cardiac apex (fifth left intercostal space).

S₂

S₂ is normally louder than S₁ at the cardiac base (second left intercostal space).

The S₂ is composed of A₂ and P₂:

• A₂ originates from closure of the aortic valve
• P₂ originates from closure of the pulmonic valve, is best heard at the cardiac base (second left intercostal space), and is quieter than A₂.
  • During expiration, A₂ and P₂ are perceived as a single sound in 90% of people.
  • During inspiration, the interval between A₂ and P₂ lengthens ('splits') and may as long as 60 msecs.

Bibliography

• McGee, Steven R. (2007). Evidence-Based Physical Diagnosis: Text with BONUS PocketConsult Handheld Software. Philadelphia: Saunders. ISBN 1-4160-2898-6. 
• Drummond Rennie; David Simel (2008). THE RATIONAL CLINICAL EXAMINATION: EVIDENCE-BASED CLINICAL DIAGNOSIS (Jama & Archives Journals). McGraw-Hill Professional. ISBN 0-07-159030-7. 

See also

• Heart murmur