Which statement best describes the S3 heart sound?

Which statement best describes the S3 heart sound?

• A. Rapid ventricular filling
• B. Occurs during ejection phase
• C. Best heard with the diaphragm at the base
• D. Normal only in elderly

Answer: (A)

S3 is a low-frequency sound that occurs in early diastole, right after the second heart sound, during rapid ventricular filling when the ventricle is compliant. The sound comes from the sudden deceleration of the inflowing blood as the atrium fills the ventricle, producing a brief “gallop” that is best heard with a bell, usually at the apex with the patient in the left lateral position. This timing and mechanism explain why rapid ventricular filling describes the S3 best. It is not tied to the ejection phase of systole, and in older adults it may indicate pathology rather than being a normal finding, whereas in children and young adults it can be normal.

S3 is a low-frequency sound that occurs in early diastole, right after the second heart sound, during rapid ventricular filling when the ventricle is compliant. The sound comes from the sudden deceleration of the inflowing blood as the atrium fills the ventricle, producing a brief “gallop” that is best heard with a bell, usually at the apex with the patient in the left lateral position. This timing and mechanism explain why rapid ventricular filling describes the S3 best. It is not tied to the ejection phase of systole, and in older adults it may indicate pathology rather than being a normal finding, whereas in children and young adults it can be normal.