Heart Sounds Types Mechanism

1. Heart Sounds
“Heart sounds are the sounds produced by the heart during a cardiac cycle, specifically when
heart valves snap shut.”
It can detected and heard easily with a stethoscope or by the help of a phonocardiograph.

2. Phonocardiograph

3. Types of Heart Sound
1. First heart sound
2. Second heart sound
3. Third heart sound
4. Fourth heart sound

5. First Heart Sound
• Its is heard dull and prolonged often described as “LUB”.
• It occur at the beginning of ventricular systole.
• It is generated due to closure of Atrio ventricular valves.
• Its frequency is 30-80 cps.
• It varies from 0.09s to 0.16s and averages 0.14s.
Significance:
• Indicates ventricular systole
• It indicates the condition of myocardium
• Indicates the compliance of Atrio Ventricular valves

7. Second Heart Sound
• It is sharp and short usually described as “DUB”.
• It occur at the end of ventricular systole.
• Its frequency is 150-200 cps.
• Its duration is 0.11s.
• It is generated due to closure of semilunar valves.
Significance:
• Indicates end of systole and beginning of diastole.
• Indicates the compliance of the semilunar valves.

9. Third Heart Sound
• It is heard occasionally and weak and rumbling in nature.
• It occur at the beginning of middle third of the diastole.
• Its frequency is below 40 cps.
• Its duration is 0.04s.
• It is generated due to the oscillation of blood back and forth between the walls of
the ventricles and is initiated by inrushing blood from atria.
• It is benign in youth, athletes, and in pregnancy.
Significance:
• It indicates the beginning of the ventricular filling.
• If third heart sound is heard as “lub-dub-ta”, then it indicates the cardiac failure.

11. Fourth Heart Sound
• It is weak and rumbling.
• It can’t be observed with stethoscope but can be recorded on phonocardiogram.
• It occur when atria contracts.
• Its frequency is 20 cps.
• Its sound is similar to those of third heart sound.
Significance:
It indicates the end of ventricular filling and occurs just before the first heart
sound.

14. Heart Murmurs
“Abnormal or ectopic heart sounds are known as heart murmurs”.
It occurs when there is some valvular or anyother abnormality causing
turbulence of blood flow either due to great velocity of ejection or its
regurgitation.

15. Types of murmur
1. Aortic Stenosis
2. Aortic Regurgitation
3. Mitral Regurgitation
4. Mitral Stenosis

16. Stenosis
“It is an abnormal narrowing in blood vessel.”
• Associated with unusal heart sound
• Occurs due to narrowed blood vessel
• Main cause is Atherosclerosis
• Due to atherosclerosis, stroke volume decreases, which results in decrease in
cardiac output, causes the blood to be ejected at higher velocity due to decrease
in the diameter of blood vessel.

17. Stenosis

18. Regurgitation
“The blood flow in the opposite direction from normal, as the
backward flowing of blood into heart or between heart chambers is
known as Regurgitation.”
• It happens due to the problems in heart valves.

19. Aortic Stenosis
• It occur during (mid) systole.
• It causes the blood to be ejected with tremendous velocity causing
turbulence in the root of aorta.
• It sound as harsh and very loud often described as “RUNG”.

20. Aortic Regurgitation
• It occur during (early) diastole.
• It results from from turbulence of blood jetting backwards into the
blood already in the left ventricle.
• It is a blowing murmur of relatively high pitch and with a swishing
quality “LUSH”

21. Mitral Regurgitation
• It occur (throughout) systole.
• It results from back flow of blood from left ventricle into left atrium.
• It is a high frequency “blowing” swishing sound often described as
“LUSK”.

22. Mitral Stenosis
• It occur in the (middle) diastole.
• It is produced due to the difficult passage of blood through stenotic
mitral valves from left atrium into left ventricle.
• It is weak and of very low frequency.
• Often described as “RRUFF”.

23. End