S2 (dupp) corresponds to which event?

• A. Marks the beginning of systole
• B. Marks the end of systole
• C. Best heard at the apex
• D. Caused by closure of the aortic and pulmonic valves; best heard in the aortic and pulmonic area

Answer: (D)

The event being tested is the closure of the semilunar valves—the aortic and pulmonic valves—that marks the end of ventricular ejection. When these valves snap shut at the end of systole, they produce the second heart sound, described as “dupp.” That sound is best heard at the base of the heart, over the aortic and pulmonic listening areas, because the sound radiates through the great vessels to those chest locations. In normal physiology, this second sound has two components: A2 from the aortic valve and P2 from the pulmonic valve, with a brief splitting that can be more noticeable on inspiration. So, the correct choice ties together the valve closure causing S2 and the typical auscultation sites.