I would also wonder if a well-monitored exercise study, or perhaps a Stress-ECHO, would help your doctors to sort-out the relative contributions of heart and lungs to your severe dyspnea with exertion. In that regard,
it is important to remember there
is not always a good correlation between symptoms, including breathlessness, and the absolute level (40-45%) of the EF. That is, LV function can be significantly deranged in the presence of a modest decrease in EF.