Tags: Disease.
The fourth heart sound or S4 is a rare extra heart sound that occurs immediately before the normal two lub-dub heart sounds (S1 and S2). It occurs just after atrial contraction and immediately before the systolic S1 and is caused by the atria contracting forcefully in an effort to overcome an abnormally stiff or hypertrophic ventricle.This produces a rhythm classically compared to the cadence of the word Tennessee with the first syllable (Ten-) representing S4.
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