Heart sound

2. 2
Heart sound:
The vibratory motion of heart produced
during the different events of cardiac cycle
conducts through the structure surrounding
the heart and produces special audible
sound called Heart Sound.
OR,
Heart sound may be defined as the sound
produced in the heart during cardiac cycle
due to vibrations and is transmitted to the
chest wall after traversing various structures
of the chest cavity.

3. 3
Causes of Heart sound / Heart sounds
are produced by :
 1. Vibration of taut valves immediately
after closure
 2. Vibration of adjacent blood (turbulent
flow)
 3. Vibration of the wall of the heart and
major vessels around the heart

4. 4
Types of heart sound:
(1) 1st heart sound
(2) 2nd heart sound
(3) 3rd heart sound
(4) 4th heart sound
 1st and 2nd heart sounds are normally
heard through the stethoscope during
each cardiac cycle. 3rd is heard in many
normal young individuals and 4th heart
sounds is not heard through the
stethoscope. All sounds can be recorded
by phonocardiogram.***

5. Characteristics of
Different Heart sounds:

6. 6
 1st heart sound:
Cause: It occurs due to vibrations set up by sudden closure
of the A-V valves (mitral & tricuspid) at the onset of
ventricular systole.
Characteristics:
1. It is soft & low pitched (frequency: 20-45 Hz) and of prolonged
duration (0.15 sec.) and like the word L-U-B.
2. It is best heard over the left 5th intercostal space just
medial to the mid clavicular line.
3. It coincides with the apex beat & the carotid pulse & the
spike of the R wave of ECG.
Significance:
1. It indicates the clinical onset of ventricular systole.
2. It indicates the proper closure of AV valve.
3. The duration & intensity indicates the condition of the
myocardium.

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2nd heart sound:
Cause: It occurs due to vibrations associated with the
closure of the aortic & pulmonary valves at the onset of
ventricular diastole or just after the end of ventricular
systole.
Characteristics:
1. It is high pitched (frequency: 50Hz), loud and sharp sound
with sharp sound with short duration (0.12 sec.) and like the
word D-U-B.
2. It is best heard over the 2nd intercostal space 11/2 inch
away from the midsternal line.
3. It occurs just after the apex beat and cardiac pulse.
Significance:
1. It indicates the end of systole & beginning of diastole.
2. Clear 2nd heart sound indicates proper closure of the
semilunar valves.

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3rd heart sound:
Cause: It is produced due to sudden rapid rush of
blood into the ventricle during 1st rapid filling
phase of ventricular diastole.
Characteristics:
1. Frequency: Low.
2. Duration: 0.1 sec.
3. It can be recorded by phonocardiogram in only one
third to one half of all people.
Significance: It indicates the beginning of
ventricular filling.

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4th heart sound:
Cause: It occurs due to contraction of atrial musculature
( active atrial contraction) during the last rapid filling phase
of ventricular diastole.
Characteristics:
1. Frequency: Low, about 20 Hz.
2. Duration: Short.
3. Not audible by stethoscope, due to low frequency.
4. Can be recorded by phonocardiogram sometimes.
Significance:
1. It indicates the end of the ventricular filling.
2. It can sometimes be heard immediately before the 1st heart
sound when atrial pressure is high or the ventricle is stiff in
conditions such as ventricular hypertrophy.

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Heart sound Physiological significance Clinical significance
1st heart
sound
1. It indicates the clinical onset of
ventricular systole
Loud 1st heart sound
indicates mitral
stenosis
2. It indicates the proper closure
of AV valve
3. The duration & intensity
indicates the condition of the
myocardium
2nd heart
sound
1. It indicates the end of systole &
beginning of diastole
1. Loud 2nd heart
sound indicates
systemic &
pulmonary
hypertension
2. Clear 2nd heart sound indicates
proper closure of the semilunar
valves
2. Splitting of 2nd
sound indicates
atrial septal defect
Significance of 1st heart sound & 2nd heart sound:

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Traits 1st heart sound 2nd heart sound
1. Cause Closure of atrio-ventricular
valves
Closure of the semilunar
valves
2. Relation with
cardiac cycle
Occurs at the beginning of
ventricular systole
Occurs at the beginning of
ventricular diastole
3. Character Soft & low pitched (frequency:
20-45 Hz) and like the word
L-U-B.
Loud & high pitched
(frequency: 45-50Hz), loud
and like the word D-U-B.
4. Duration Prolonged (0.15 sec.) Short (0.125 sec.)
5. Relation with
apex beat &
carotid pulse
Coincides with apex beat &
carotid pulse
Occurs just after the apex
beat & carotid pulse
6. Best heard Over the left 5th intercostal
space just medial to the mid
clavicular line
Over the 2nd intercostal
space 11/2 inch away from
midsternal line
7. Pause It comes after a long pause It comes after a short pause
Differences between 1st and 2nd heart sound:

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Apex beat:
It is the lowest and outermost point of definite cardiac
pulsation.
Position: Left 5th intercostal space just medial to the
midclavicular line.
Importance:
1. Determination of heart rate.
2. Determination of the position of the heart-whether
dextrocardia or not.
3. Diagnosis of different heart diseases.
4. Determination of displacement of the mediastinum either to
the right or left-due to pleural effusion, pneumonia, collapse
of lung, pneumothorax, left ventricular hypertrophy etc.

15. 15
Cardiac murmur: (Abnormal heart sound)
Murmurs or bruits are the abnormal sounds heard in
various parts of the vascular system. But murmur is
more commonly used to denote abnormal sounds or
noise heard over the heart then over blood vessels.
Cause of murmur: It occurs due to
1. Abnormal blood flow (turbulence) through normal
valves or
2. Normal blood flow through abnormal/diseased
valves.

17. 17
Sites where the heart sounds are best
heard: 1st heart sound is best heard in the
mitral and tricuspid areas. 2nd heart sound is best
heard in the aortic and pulmonary areas.
1. Mitral area: On the apex beat, in the left 5th
intercostal space just medial to the midclavicular line.
2. Tricuspid area: In the left 4th intercostal space just
lateral to the sternum.
3. Aortic area: Right 2nd intercostal space just lateral
to the sternum.
4. Pulmonary area: Left 2nd intercostal space just
lateral to the sternum.

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Question:
Why the duration of 1st heart sound is longer than the
2nd heart sound?
Answer:
The reason for the shorter 2nd heart sound is that the
semilunar valves are more taught than the AV valves,
so that they vibrate for a shorter period than do the AV
valves.

20. 20
Question:
Why has the 2nd heart sound a higher frequency than
1st sound?
Answer:
2nd sound normally has a higher frequency than 1st
sound for two reasons:
1. The tautness of the semilunar valves in comparison
with much less taut AV valves and
2. The greater elastic co-efficient of the taut arteries
that provide the principal vibrating chambers for the 2nd
sound in comparison with the much looser ventricular
chambers that provide the vibrating system for the 1st
sound.

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Question:
In which cases 3rd heart sound is heard?
Answer:
3rd heart sound is heard only in those subjects who
have a very good venous return (as during exercise
and recumbent posture). It is heard clinically in
athletes and children and best heard in the mitral
area.

22. 1st Heart sound 2nd heart sound 3rd heart sound 4th heart sound
Nature-dull, low
pitched,
prolonged
Nature-short,
sharp and high
pitched
Nature-soft and
low pitched
Nature-low
pitched
Duration-0.14
sec
Duration-0.11
sec
Duration-0.1 sec Short
Time of
occurrence-At
the onset of
vent. systole
Time of
occurrence-At
the onset vent.
diastole
Time of
occurrence-At
1st 3rd of
ventricular
diastole
Time of
occurrence-
during last rapid
filling phase
Cause-Sudden
closure of A-V
valve
Cause-Sudden
closure of
semilunar valve
Cause-inrushing
of blood from
atria to ventricles
Cause-Due to
active atrial
contraction
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