S4 heart sound is a rare noise heard during which part and is associated with what condition?

• A. A rare noise in the middle of "lub," caused by a failing left ventricle and best heard in the cardiac apex
• B. The sound of the AV valves closing
• C. A noise during ventricular ejection
• D. A murmur due to aortic stenosis

Answer: (A)

S4 is a late diastolic sound produced when the atria contract and push blood into a noncompliant, stiff left ventricle. This atrial kick against a ventricle with reduced compliance creates a low-pitched gallop just before the first heart sound. It’s relatively rare and is best heard at the cardiac apex with the patient in the left lateral decubitus position, using the bell of the stethoscope. The presence of S4 points to diastolic dysfunction and is commonly associated with conditions that make the LV stiff, such as left ventricular hypertrophy from long-standing hypertension, cardiomyopathy, ischemic heart disease, or aging.

This fits the described option because it highlights a late diastolic event caused by a failing or stiff left ventricle and locates the best auscultation site. In contrast, S1 is the sound of the AV valves closing, the other choice points to a systolic event during ventricular ejection, and the remaining option describes a murmur from aortic stenosis—none of which correspond to the late diastolic atrial kick of S4.