Question about Ejection fraction

I am a young otherwise healthy woman in my early 40's with a history of MVP/MVR, which I've had from a child.  Within the last 10 years the regurgitation has gone from mild to moderate/severe  I am probably going to have surgery within a year or so, but my doctor is not pushing for it yet.  I'm debating weather or not to see a surgeon for a 2nd opinion.  My question is this ------I recently had a 3d echo and it states that my ejection fraction is 55-65%.  I'm confused why they gave a range like this.  I recently obtained a CD with the images and on certain images, there is text that says the following:

LA Dimension 4.6cm
LVIDs 3.67 cm
ESV (2D Teich) 57.0 ml
EF (2D Teich) 46.2%

LVIDs 3.86 cm
ESV (2D Teich) 64.3 ml
EF (2D Teich) 39.3%

Max MR Velocity 507 cm/sec
MR VTI 157 cm

MV PISA Radius 0.6 cm

I don't understand why EF (which I'm understanding is EJECTION FRACTION) has different percentages than then written report states. There are about 53 images on the CD and these particular measurements are printed in the upper right hand corner of certain pictures.

I know that my MVR has gotten worse because I'm starting to have more fatigue than usual.  

Thank you for your help.  I appreciate it.

[Cleveland Clinic]

I would suggest a second opinion especially that you are getting more fatigued.  EF's are reported by the reading physician not by the machine.  The latter is usually very incorrect in assessing EF because it only looks at one frame.  I would say that if your EF is close to 55% that you should ahve your surgery soon.

[ocean12]

Thank you for your reply.  I also had asked why was my EF was reported as 55-65%.  Is it normal to give such a large range like this?  If my EF was at 55%, then that would mean that I should have surgery soon, especially with the severe regurgitation.  But if my EF is 65%, then that would be fine.  Is this normally done -- it sure creates a level of confusion.

I also thought that EF was based on a formula (EDV-ESV = stroke volume.  Then the stroke volume is divided by EDV = Ejection Fraction).  

Is it done calculated that way?  I didn't know it was based on visual.  One person might view it differently than another.  How can that be accurate?  I apologize for the question again, but I remain somewhat confused.  I appreciate your help.