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