What heart sound is produced by rapid ventricular filling into an already distended ventricle?

The heart sound produced by rapid ventricular filling into an already distended ventricle is the third heart sound, or S3. This sound occurs early in diastole when the atrioventricular valves open, allowing blood to flow into the ventricles. If the ventricles are already stiff or compliant—conditions often seen in heart failure or volume overload—the rapid influx of blood can lead to the generation of this sound.

S3 is commonly associated with conditions that result in an increase in blood volume entering the ventricles or a decrease in ventricular compliance. It is often described as a "gallop" sound and may be an important indicator of heart failure in patients.

The other options present alternative heart sounds or phenomena that occur under different circumstances. The S4 sound, or "atrial gallop," occurs just before S1 and is associated with a stiff ventricle, typically due to conditions like hypertensive heart disease or left ventricular hypertrophy. An opening snap is related to mitral stenosis and represents the sudden tensing of the mitral valve leaflets when they open. Lastly, an exaggerated S2 often occurs due to conditions such as hypertension or increased blood flow across the valves but does not typically relate to rapid ventricular