American Association of Critical-Care Nurses (AACN) Certification Practice Test

A normal S3 heart sound, also known as a third heart sound or "physiological S3," is typically heard during early diastole and can be a normal finding, particularly in certain populations such as children, young adults, and pregnant women. In these groups, the sound is often associated with rapid ventricular filling and reflects normal hemodynamic changes as the heart accommodates increased blood volume.

The presence of an S3 heart sound in these populations indicates that the heart is functioning properly, and the sound arises from the vibration of the valves and surrounding structures as blood rushes into the ventricles. Understanding that this finding can be normal helps differentiate it from pathological S3 sounds, which may suggest conditions such as heart failure or volume overload in older adults.

In contrast, conditions such as systolic heart failure or mitral stenosis might produce an abnormal S3 sound related to underlying cardiac dysfunction. Decreased cardiac output may result in various changes to heart sounds, but it doesn't inherently correlate with a normal physiological response represented by the S3 sound in the right context. Recognizing when an S3 is physiological versus pathological is critical for accurate assessment and management.