What is an S4 heart sound typically associated with?

An S4 heart sound is typically associated with a stiff, noncompliant left ventricle, which is often the result of hypertrophy due to chronic hypertension or other underlying conditions. In a healthy heart, the ventricles relax during diastole, allowing for adequate filling with blood. However, when the left ventricle becomes stiff, it can no longer accommodate the blood volume effectively during this phase. This leads to the distinct sound of the S4 heart sound, which occurs just before the first heart sound (S1) as the atria contract and push blood into a noncompliant ventricle.

The presence of the S4 heart sound indicates that there is increased resistance to filling in the left ventricle, often seen in conditions such as heart failure with preserved ejection fraction (HFpEF). This sound reflects an underlying pathology of reduced ventricular compliance rather than simply increased pressure or overload alone. It is essential to differentiate this from other cardiac sounds and conditions to accurately assess the underlying issues in patients with suspected heart failure.