ECG is recorded with phonocardiogram to identify the different heart sounds. Second heart sound will appear at which point in the following diagram?
A. Point A
B. Point B
C. Point C
D. Point D
Answer- B. Point B
- Second heart sound (S2) precedes or appears 0.09 sec after summit of “T” wave. In the given figure, A=E= S1; B= S2; C= S3; D= S4.
- The first is a low, slightly prolonged ‘lub’ (first sound), caused by vibrations set up by the sudden closure of the AV valves at the start of ventricular systole.
- The second is a shorter, high-pitched. “dup” (second sound), caused by vibrations associated with closure of the aortic and pulmonary valves just after the end of ventricular systole. A soft, low-pitched third sound is heard about one-third of the way through diastole in many normal young individuals. It coincides with the period of rapid ventricular filling and is probably due to vibrations set up by the inrush of blood. A fourth 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 hypertrophy. It is due to ventricular filling and is rarely heard in normal adults.