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Fourth (4th) heart sound

Last reviewed dd mmm yyyy. Last edited dd mmm yyyy

Authoring team

The fourth heart sound is due to atrial contraction inducing ventricular filling towards the end of diastole. They are never audible in normal subjects. A fourth heart sound is the result of powerful atrial contraction filling an abnormally stiff ventricle.

Left atrial heart sound is maximal at the apex, with possible causes including:

  • left ventricular hypertrophy
  • fibrotic left ventricle
  • hypertrophic cardiomyopathy

Right atrial heart sound is maximal at the lower left sternal edge and on inspiration. This may occur in right ventricular hypertrophy.

Evidence base:

  • in patients referred for non-emergency left sided heart catherisation, third and fourth heart sounds detected by phonocardiography (1)
    • neither the phonocardiographic S3 nor the S4 is a sensitive marker of left ventricular dysfunction
    • the phonocardiographic S3 is specific for left ventricular dysfunction and appears to be superior to the moderate specificity of the phonocardiographic S4
  • thus the absence of a gallop rhythm should not be used to indicate the absence of left ventricular dysfunction and certainly cannot replace other diagnostic testing when screening for left ventricular dysfunction (2)


  1. Marcus GM et al. Association between phonocardiographic third and fourth heart sounds and objective measures of left ventricular dysfunction. JAMA 2005; 293:2238-44.
  2. Commentary. Evidence-Based Medicine 2005;10:182.

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