What heart sound is typically associated with rapid ventricular filling?

The heart sound typically associated with rapid ventricular filling is the third heart sound, known as S3. This sound occurs soon after S2, during the rapid filling phase of the ventricles when blood flows from the atria into the ventricles. It is often referred to as a "ventricular gallop." The presence of S3 can indicate that the ventricles are compliant and able to accommodate the rapid influx of blood, which is a normal finding in children and young adults, but may signify heart failure or volume overload in older adults.

Additionally, while S1 marks the closure of the mitral and tricuspid valves and S2 marks the closure of the aortic and pulmonic valves, they are not associated with the filling phase of the ventricles. Snaps are associated with certain valvular dysfunctions but are not part of the normal heart sounds associated with rapid filling. Thus, S3 is the critical sound reflecting this physiological event in the cardiac cycle.