Hi Vik,
Welcome back to the forum.
There are several ways to calculate an EF. Echo is the most common but MUGA, MRI, ventriculogram during cardiac cath, etc can all provide generally reliable EF calculations.
A well performed MUGA test is often fairly reliable. Sometimes the images with Echo can be suboptimal and contrast is needed to truly see the heart walls sufficiently well to make a reliable EF calculation.
Frankly, at the end of the day, I would trust your mom's physician. Electrophysiologists implant ICDs and pacemakers for a living and they believe in them. The fact that the EP doc is advising against it at this time suggests that your mom may not need it. There is no harm in repeating an echo if this would provide you peace of mind but you may find yourself going back and forth with this "dilemma".
I would move forward following the EP doc's advice. If in the future a repeat echo (or MUGA) suggests a deteriorating EF and CRT is now being recommended then I would pursue that at that time.
I know this can be confusing but I suggest you follow the cardiologist's advice. If you do not trust this cardiologist, then I would seek a 2nd opinion.
Best,
Dr. Rich
Thanks again, I really appreciate your input.