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The fourth heart sound or S 4 is a rare extra heart sound that occurs immediately before the normal two "lub-dub" heart sounds (S 1 and S 2). It occurs just after...
Fourth Heart Sound (S4) The fourth heart sound is the sound of the vibration of a non-compliant ventricle that is forced to accept blood during atrial systole.
Both the third and fourth heart sounds (S3 and S4) are low frequency. S4 is lower than S3. This is a pattern that occurs with improvement of heart failure.
Fourth Heart Sound Gallop auscultation guide. Course #25; The fourth heart sound occurs in late diastole just prior to the first heart sound.
The fourth heart sound is due to atrial contraction inducing ventricular filling towards the end of diastole. They are never audible in normal subjects.
Fourth Heart Sound repetition training - ID#42; This web site is for use by medical professionals. All information is for educational purposes only.