Adult-Gerontology Clinical Nurse Specialist (CNS) Practice Exam

What best describes the S4 heart sound?

1. Closure of the tricuspid and mitral valves.

2. Closure of the aortic and pulmonary valves.

3. Low-frequency sound heard early in diastole.

4. Low-frequency sound heard late in diastole.

The correct answer is: Low-frequency sound heard late in diastole.

The S4 heart sound is characterized as a low-frequency sound that occurs late in diastole, just before the S1 heart sound that marks the beginning of ventricular contraction. This sound is produced during the active filling phase of the ventricles when the atria contract to push blood into the ventricles. It is often associated with conditions that lead to increased stiffness of the ventricle, such as hypertension or heart failure, where the atrial contraction creates a turbid flow of blood into a non-compliant ventricle. In contrast, closure of the tricuspid and mitral valves generates the first heart sound (S1), and closure of the aortic and pulmonary valves produces the second heart sound (S2). Thus, the descriptions of these other sounds do not accurately relate to the characteristics or timing associated with the S4 heart sound. This differentiation is crucial for clinicians when evaluating heart sounds during auscultation.