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