Rapid ventricular filling is associated with which heart sound?

The third heart sound, commonly referred to as S3, is associated with rapid ventricular filling. This sound occurs when blood flows into the ventricles during the early part of diastole, particularly when the ventricles are filled rapidly, as occurs in conditions like volume overload or heart failure. It is often described as a "gallop" rhythm, and it is more commonly heard in young individuals, athletes, and pregnant women due to their higher blood volume and compliant ventricles.

This characteristic of S3 helps clinicians assess the heart's filling dynamics and potential issues with ventricular compliance. The presence of an S3 sound in older adults may indicate underlying cardiac dysfunction, but it is normal in certain populations. In contrast, the first heart sound occurs during the closure of the atrioventricular valves prior to ventricular contraction, the second heart sound signals the closure of the semilunar valves at the end of ventricular systole, and the fourth heart sound reflects atrial contraction and is typically associated with stiff or hypertrophied ventricles. Therefore, the understanding of the heart sounds and their correlation with filling dynamics is critical for recognizing cardiac conditions in veterinary practice.