What is the diastolic sound?

• A. Systolic sound, associated with isovolumetric ventricular contraction.
• B. Diastolic sound, associated with isovolumetric ventricular relaxation.
• C. A short/sharp sound not related to valve activity.
• D. A continuous murmur.

Answer: (B)

The diastolic sound is the second heart sound, heard as the semilunar valves (aortic and pulmonary) snap shut at the start of diastole. This marks the moment when the ventricles stop ejecting and begin to relax, entering a brief period of isovolumetric relaxation when all valves are closed and the ventricular volume remains unchanged. That valve closure during this relaxation phase creates the characteristic “dub” sound that signals the onset of diastole.