Which of the following is true about fouh hea sound 'S4'
4th hea sound cannot be heard even by a stethoscope since its frequency is below the audible limit (20 Hz). It is produced during last rapid filling of ventricles, which occurs due to atrial systole. Hence, it is also called "atrial sound". S1: Closure of A.V. valves (25-45 Hz) and S2: closure of semilunar valves (50 Hz). They can be heard by stethoscope.
Can be heard by the unaided ear
Frequency is greater than 20 Hz
Heard during ventricular filling phase
Heard during ventricular ejection phase
Cardiac Cycle