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Physiological Splitting of Second Heart Sound

Components of Second Heart Sound
  • Second heart sound (S2) is produced due to the closure of semilunar valves.

  • Semilunar valves include:

    • Aortic valve: between the left ventricle and aorta

    • Pulmonary valve: between the right ventricle and pulmonary artery

  • So actually there are two components of second heart sound:

    • Aortic component (A2)

    • Pulmonary component (P2)

The Mechanism of Splitting

Pressure in the aorta is higher than that in the pulmonary artery

The aortic valve closes slightly before the closure of the pulmonary valve

The sound of closure of the aortic valve is produced a bit earlier than that of the pulmonary valve

Splitting of S2 into A2 and P2 components

Accentuation of Splitting During Deep Inspiration

Deep inspiration

Intrathoracic pressure becomes more negative

Venous return to the right heart increases as compared to that in the left heart

Emptying of the right ventricle takes a little longer than the left ventricle

Closure of pulmonary valve is delayed

Accentuation of splitting of second heart sound


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