Try not to worry, my
EF went from 75% in 2001 to 55% in 2005, in fact the cardio seems more pleased when it was 55% than 75% , remember
EF can vary , some docs look at the same
echo and cal itl 50%, another may call it 55%, another 60%, that why its is often referred as + - /5%, I wouldn't worry about this but mention it to your doc or get rechecked, some centers call 55-70% normal, others 50-75%, 50 % would be considered low normal, unless you have other symptoms, don't lose sleep over this , mean symptoms , swelling of lower extremities, or shortness of breath on little exertion and extrme fatigue.