1. What Are Heart
Sounds?
- Heart
sounds are noises produced by the vibration of valves and blood flow
during the cardiac cycle.
- Best heard
using a stethoscope.
2. Types of Heart
Sounds
There are two normal (physiological) heart sounds and two
extra (abnormal or sometimes normal) heart sounds:
Normal Heart Sounds:
- First
Heart Sound (S₁) – “Lub”
- Second
Heart Sound (S₂) – “Dub”
Additional Heart Sounds (may
be normal or abnormal):
- Third
Heart Sound (S₃)
- Fourth
Heart Sound (S₄)
S₁ – First Heart Sound
(Lub)
- Due to closure
of AV valves (Mitral and Tricuspid valves)
- Occurs at
the beginning of ventricular systole
- Best heard
at the apex of the heart
- Low-pitched
& long
Mnemonic: "M-T" (Mitral &
Tricuspid closure = S₁)
S₂ – Second Heart Sound
(Dub)
- Due to closure
of semilunar valves (Aortic and Pulmonary valves)
- Occurs at
the beginning of diastole
- Best heard
at the base of the heart
- High-pitched
& short
Mnemonic: "A-P" (Aortic &
Pulmonary closure = S₂)
S₃ – Third Heart Sound
- Due to rapid
ventricular filling
- Occurs just
after S₂
- Best heard
in young individuals, athletes, and pregnancy (can be normal)
- In older
adults, may indicate heart failure
Mnemonic: "Kentucky" rhythm (S₁ - S₂ -
S₃)
S₄ – Fourth Heart Sound
- Due to atrial
contraction against stiff ventricle
- Occurs just
before S₁
- Always abnormal
in adults – indicates LV hypertrophy, HTN
Mnemonic: "Tennessee" rhythm (S₄ - S₁
- S₂)
3. Auscultation Areas
of the Heart
|
Valve Area |
Location (Intercostal Space) |
|
Aortic valve |
Right 2nd ICS, just next to sternum |
|
Pulmonary valve |
Left 2nd ICS, next to sternum |
|
Tricuspid valve |
Left 4th or 5th ICS, near sternum |
|
Mitral valve |
Left 5th ICS, midclavicular line (apex) |
4. Clinical
Significance
- Murmurs – due to
turbulent blood flow or valve defects.
- Splitting
of S₂ – may be normal during inspiration or pathological.
- Gallop rhythm – combination of S₁, S₂, and S₃/S₄ – indicates cardiac dysfunction.
