Fouh hea sound is caused by: (A) Closure of AV valves, (B) Closure of semilunar valves, (C) Rapid ventricular filling, (D) Atrial contraction
Answer is D. A fouh sound can sometimes be heard immediately before the first sound when atrial pressure is high or the ventricle is stiff in conditions such as ventricular hyperophy. It is due to ventricular filling and is rarely heard in normal adults.Ref: Ganong&;s Review of medical physiology 25th edition. Page: 542