S4 occurs, if heard, coincides with atrial contraction at the end of (ventricular) diastole. Like S3, it represents an additional sound caused by the relatively rapid filling rate against a relatively stiff ventricle. An S4, if heard should occur 25-75 ms before S1. As with an S3, a patient could have a left sided S4 (best heard with the bell of the stethoscope at the apex of heart while the patient is in the left lateral decubitus position), a right sided S4 (best heard with the bell of the stethoscope in the tricuspid region with the patient in the supine position during inspiration) or both.
An S4 can occasionally be normal, but is generally
pathological.
A normal S4 rarely occurs in:
An abnormal S4 (also known as an atrial sound or atrial gallop) is associated with:
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(16 October 2006)
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