<prompt> All of the following statements about third Hea sound S3 are true, exceptOccurs due to rapid filling of the ventricles during atrial systoleSeen in in constrictive pericarditisSeen in Atrial Septal Defect ASDSeen in Ventricular Septal Defect VSD  <response>: A third hea sound S 3 is often heard in large left-to-right shunts caused by high flow across the mitral valve with VSD or patent ductus aeriosus and with high flow across the tricuspid valve with ASD.In constrictive pericarditis, an early prominent sound of a somewhat higher frequency is heard - called the pericardial knock, which is considered as a variant of S 3.HurstsThe third hea sound S 3 occurs during the rapid filling phase of ventricular diastole. Harrisons. The rapid filling phase mid-diastole begins when the tricuspid and mitral valves open. Ventricular filling occurs passively in this period. Presystole begins with atrial contraction and occurs just before the first hea sound. Active filling from atrial systole contributes about 20 of the blood volume to the ventricles during diastole in contrast with the 80 from rapid, passive filling in mid-diastole.The first option mentions ventricular filling during atrial contraction. Hence, it is the answer.Ref : Hurst 13e p287; Harrison 18e p1827 