This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: C.V.S, Subject name: Medicine
True about third hea sound is- 
Select and explain. 
A. Present in constrictive pericariditis, B. Absent in aoic aneurysm, C. Absent in MS, D. Present in cardiac yamponade
C: Absent in MS
Answer: C: Absent in MS 
Explanation: 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. A left-sided S 3 in patients with chronic hea failure ispredictive of cardiovascular morbidity and moality. Interestingly,an S 3 is equally prevalent among hea failure patients with andwithout LV systolic dysfunction.Harrison's principle of internal medicine,20edition,pg no.1554