With the onset of Atrial fibrillation
- The first heart sound becomes variable in Intensity (Soft to loud in pliable valve / Soft to softer in calcified valve )
- Opening snap continue to occur as long as the valves are pliable and noncalcified .The timing may vary but Intensity remain same .
- A 2-OS interval is usually less influenced by AF as it is primarily determined by mean LA pressure at the onset of diastole which has little variation beat to beat .
- Length of the diastolic murmur varies . In Short cycles MDM can be very brief or even in audible.
- In long cycles MDM will be distinct.
- A late diastolic murmur in long cycle indicates severe MS.
- Even pre-systolic accentuation may be appreciable in some of the long cycles .
Link to Echo Image of Mitral stenosis .
How to assess the severity of MS in the presence of AF ?
- Presence of AF by itself indicate presence of severe MS in most .
- A2-OS interval may be useful
- Concentrate on long cycle .Look for ( rather listen !) for late diastolic component of MDM .If you hear it , MS is usually severe
Other signs are often useful
Low volume pulse
Inconspicuous LV impulse
Presence of any significant Pulmonary hypertension