Question:medium
All of the following statements about the third heart sound (S3) are true, except:
All of the following statements about the third heart sound (S3) are true, except:
Show Hint
S3 is early diastole; the sound tied to atrial contraction is a different one.
Updated On: Jun 24, 2026
- Occurs due to rapid filling of the ventricles during atrial systole
- Seen in constrictive pericarditis
- Seen in atrial septal defect (ASD)
- Seen in ventricular septal defect (VSD)
Show Solution
The Correct Option is A
Solution and Explanation
Each heart sound maps to a specific moment in the cardiac cycle, and the trick here is to match S3 to its correct timing. The diastolic sounds are S3 in early diastole and S4 in late diastole.
S3 is generated as blood rushes into the ventricle during the early, rapid, passive filling phase right after the mitral and tricuspid valves open. It has nothing to do with the atria squeezing. The sound that comes from atrial systole pushing the final bolus of blood into a stiff ventricle is S4, not S3. So the option that ties S3 to atrial systole is the wrong one and the answer to this except question.
Checking the disease associations confirms the rest. Constrictive pericarditis gives a pericardial knock, an early diastolic sound treated as an S3 equivalent because the rigid pericardium stops filling abruptly. Left-to-right shunts such as an atrial septal defect and a ventricular septal defect drive extra volume across the AV valves, and that brisk diastolic inflow produces an audible S3. All three of these statements are therefore true.
Only the timing claim is false.
$$\boxed{\text{Occurs due to rapid filling of the ventricles during atrial systole}}$$
S3 is generated as blood rushes into the ventricle during the early, rapid, passive filling phase right after the mitral and tricuspid valves open. It has nothing to do with the atria squeezing. The sound that comes from atrial systole pushing the final bolus of blood into a stiff ventricle is S4, not S3. So the option that ties S3 to atrial systole is the wrong one and the answer to this except question.
Checking the disease associations confirms the rest. Constrictive pericarditis gives a pericardial knock, an early diastolic sound treated as an S3 equivalent because the rigid pericardium stops filling abruptly. Left-to-right shunts such as an atrial septal defect and a ventricular septal defect drive extra volume across the AV valves, and that brisk diastolic inflow produces an audible S3. All three of these statements are therefore true.
Only the timing claim is false.
$$\boxed{\text{Occurs due to rapid filling of the ventricles during atrial systole}}$$
Was this answer helpful?
0
