METHODS OF STUDY OF HEART SOUNDS
Heart sounds are studied
by three methods:
1. By using stethoscope
2. By using microphone
3. By using
phonocardiogram.
BY STETHOSCOPE
First and second heart
sounds are heard on the auscultation areas, by using the stethoscope. The chest
piece of the stethoscope
is placed over four areas on the chest, which are called auscultation areas.
Auscultation Areas
i. Mitral
area (Bicuspid area)
Mitral area is in the left
5th intercostal space, about 10 cm away from the midline (midclavicular line).
Sound produced by the closure of mitral valve (first heart) sound)
is transmitted well into this area. It is also called apex beat
area because apex beat is felt in this area.
Apex beat
Apex beat is the thrust of
the apex of ventricles, against the chest wall during systole.
ii. Tricuspid area
Tricuspid area is on the
xiphoid process. Sound produced by the closure of tricuspid
valve (first heart
sound) is transmitted well
into this area.
iii. Pulmonary area
Pulmonary area is on the
left 2nd intercostal space, close to sternum. Sound produced by the closure of
pulmonary valve (second
heart sound) is heard well on this area.
iv. Aortic area
Aortic area is over the
right 2nd intercostal space, close to the sternum. On this area, the sound
produced
by the closure of aortic
valve (second heart sound) is heard well.
First heart sound is best
heard in mitral and tricuspid areas. However, it is heard in other areas also
but the intensity is less. Similarly, the second heart sound is best heard in
pulmonary and aortic areas. It is also heard in other areas with less intensity.
BY MICROPHONE
A highly sensitive microphone
is placed over the chest. The heart sounds are
amplified by means of an amplifier and
heard by using a loudspeaker. First, second and third heart sounds are
heard by this method.
BY PHONOCARDIOGRAM
Phonocardiography is the
technique used to record the heart sounds. Phonocardiogram is the graphical
record of heart sounds. It is done by placing an electronic sound transducer
over the chest. This transducer is connected to a recording device
like polygraph. All the four heart sounds can be recorded in phonocardiogram.
It helps to analyze the frequency of the sound waves.
Appearance of Heart
Sounds in Phonocardiogram
In phonocardiogram, the
heart sounds are recorded in the following manner.
First heart sound
First heart sound is recorded
as single group of waves. The waves are of small amplitude to start with.
Later, the amplitude rapidly rises and falls to form crescendo and diminuendo
series of waves. About 9 to 13 waves appear.
Second heart sound
Second heart sound appears
as single group of waves, which have same amplitude. About 4 to 6 waves are recorded.
Third heart sound
Third heart sound is found
in phonocardiogram with only 1 to 4 waves grouped together.
Fourth heart sound
Mostly,
the fourth heart sound merges with first heart sound. If it appears as
separate form, it has 1 to 2 waves with very
low amplitude
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