A2-OS interval

Mitral Stenosis A2-OS interval

Opening snap (OS) of the mitral stenosis is a high-pitched early diastolic sound due to sudden tensing of the valve leaflets and subvalvular apparatus at the end of the opening excursion.

  • The OS occurs 40-120 milliseconds after A2.
  • A2-OS interval is inversely proportional to the height of the left atrial (LA)-LV diastolic pressure gradient.
  • Mitral Stenosis severity – A2-OS interval varies inversely with the severity of mitral stenosis.

A2-OS interval

  1. Mild MS – A2-OS interval of more than 100 milliseconds usually indicates mild MS
  2. Moderate MS – A2-OS interval 70 -100 milliseconds usually suggests Moderate MS
  3. Severe MS – A2-OS interval less than 70 milliseconds usually suggests severe MS

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