Which of the following is true about fouh hea sound 'S4' :

C i.e. Heard during ventricular filling It is a low pitched presystolic sound which can almost never be heard with a stethoscope (& ear) because of its weakness and very low frequency - usually 520 cycles/ second (1-1,)Q. It is caused by in thrushing of blood into ventricles (ventricular fillingQ, which initiates vibration) when the atria contractsQ. S4, sometime becomes audible, when atrial pressure is very high or ventricle is stiff (diminished ventricular compliance) increasing the resistance to normal filling. When audible it is best heard with bell of stethescope, at left ventricular apex in left lateral position and accentuated by exercise (isotonic or isometric) in the supine position. Pathologically S4 may be seen in Pulmonary stenosis & hypeension (right S4) Aoic stenosis & systemic hypeension Ischemic hea disease - HOCM - Mitral regurgitation Advanced age (physiological) Feature 1st hea sound 2" hea sound 3rd heat sound 4th hea sound Character Low pitched (frequency) slightly prolonged "lub" Shoer high pitched "dup" Soft low pitched weak rumbling Aerial hea sound Duration 0.14 second 0.11 sec 0.1 sec ? Frequency 25-45 Hz 50 Hz < 20 HzQ Cause Sudden closure of mitral & tricuspid valves Closure of aoic & pulmonary valves Rapid ventricular fillingQ d/t inthrushing of blood from atria Ventricular fillingQ d/t atrial contraction causing inthrushing of blood Timing Sta of ventricular systole Just after end of ventricular systole Begining of middle third of diastole Immediately before 1st hea sound (presystolic) Heard Si & S2 can be heard with stethoscope S3 & S4 can not be heard by stethoscope (ear)Q. S3 oftenly and Sa sometimes can be recorded in phonocardiorgam