S3 is typically associated with which form of heart failure?

• A. Diastolic CHF
• B. Right-sided CHF
• C. High-output failure
• D. Systolic CHF

Answer: (D)

S3 reflects rapid, early filling of a ventricle that is volume overloaded and not contracting effectively. When the left ventricle has reduced systolic function (reduced ejection fraction), it becomes dilated and holds more blood. In early diastole, blood rushing into this compliant but weakened ventricle generates a low-pitched sound—the S3. This pattern is a classic sign of systolic heart failure, where the ventricle struggles to pump out blood and filling pressures are high.

In contrast, a stiff, noncompliant ventricle from diastolic dysfunction tends to produce an S4, not an S3. While S3 can appear in other states, its association with a dilated, poorly contracting ventricle makes it most consistent with systolic heart failure.