Dr said normal: estimated lvef is 65 - 70%. biplane method used to measure ejection fraction. normal cavity size, wall thickness, systolic function (ejection fraction normal) and diastolic function. mild mid-cavity obstruction <- meaning of this?

Your cardiac size and function appear normal. The ejection fraction is higher than the normal range and may reflect anxiety while you were getting the test done,or the effect of concomitant medication like those used for asthma. Mild mid-cavity "obstruction" implies that the reading physician felt that hyperdynamic contraction caused mild obstruction to blood flow. Please clarify further.

It means your heart is functioning normally, with normal chambers, but the mid portion of the main pumping chamber is squeezing more than the rest. This could be simply due to volume status, like if you were a little dehydrated when it was done. Other more serious causes of cavity obstruction (Hypertrophic Cardiomyopathy) would also show abnormal thickening of the walls, like the septum.