My EF went from 40 to 30-35 since February. Should I be concerned?

An estimate of EF (ejection fraction) can sometimes vary by about 10% and is difficult to estimate more accurately than that. The estimate can vary with the same study if two doctors estimate it, or even if the same person estimates it at different times. It can also vary if the test is done on different days or if different types of studies are performed. It is best to discuss with your cardiologist to determine if the change is real and if it is, if anything can be done to improve it.