I have an Echocardiogram every 6 months, and my doctor considers it mandatory. The ECG is a very benign test, using an ultrasound wand to see if the valves are functioning properly, and looking at the heart itself to see if size is normal and if it's pumping normaly.
My understanding of the MUGA is that it is a much more precise and accurate test, but it also uses a small amount of radioactive substance, appx. the same amount as is received from an x-ray, and just personally I feel that over time all these exposures to radiation for tests adds up, so I try to limit it to just what's necessary. Since my heart is doing ok so far, a more benign test for now is fine, and if there's ever a question I can then have a MUGA test.
Hugs,
Lolly