When are S2 heart sounds heard?

S2 heart sounds are produced specifically when the aortic and pulmonary valves close at the end of ventricular systole. This sound is a key part of the cardiac cycle, signaling the transition from the pumping phase of the heart to the filling phase. The closure of these semilunar valves indicates the end of blood being ejected from the ventricles into the aorta and pulmonary artery, marking the beginning of diastole.

The S2 sound is typically described as a "dub" and is crucial for auscultation assessments during a cardiovascular examination. In clinical practice, recognizing the S2 sound and its timing within the cardiac cycle aids in diagnosing various cardiac conditions and understanding heart function.

Other choices reference different phases of the cardiac cycle or valve actions that do not directly correspond to the characteristic sound being studied.