A soft low-pitched sound heard best at the apex in early diastole, shortly after the second heart sound, in a 22-year-old woman is most consistent with which finding?
- A Physiological third heart sound from rapid passive ventricular filling ✓
- B Fourth heart sound from atrial contraction against a stiff ventricle
- C Opening snap of mitral stenosis
- D Midsystolic click of mitral valve prolapse
Correct answer: A. Physiological third heart sound from rapid passive ventricular filling
Explanation
The third heart sound occurs in early diastole at the end of the rapid filling phase, when blood decelerating against the ventricular wall sets up vibrations. It is physiological in children, young adults and pregnancy. The fourth sound, option B, occurs in late diastole just before S1 and reflects atrial contraction, while an opening snap follows S2 earlier and is high pitched.
Reference: Harrison's Principles of Internal Medicine, 21st ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
Written and medically reviewed by the StethoPrep medical team.