<prompt> All of the following statements about third Hea sound S3 are true, except -Occurs due to filling of the ventricles during atrial systoleSeen in mitral regurgitationSeen in Atrial Septal Defect ASDSeen in Ventricular Septal Defect VSD  <response>: The third hea sound S 3 occurs during the rapid filling phaseof ventricular diastole. It can be a normal finding in children,adolescents, and young adults; however, in older patients it signifieshea failure. A left-sided S 3 is a low-pitched sound best heard overthe left ventricular LV apex. A right-sided S 3 is usually betterheard over the lower left sternal border and becomes louder withinspiration. Harrisons principle of internal medicine,20th edition,pg no.1545 