Its difficult to believe your EF is at 40% (systole, weak contractions) and able to average 16 METs. If it be true, then your system is compensating very well for a weak heart. Normal EF is approx. 50 to 75 and heart failure is below 30%.
There can be a serious heart problem and no symptoms!...before there can be a prognosis regarding your EF, the underlying cause should be identified. Almost always inadequate pumping functionality is due to heart muscle disease and successful treatment can be beneficial.
To answer your question one would first have to know which type of dysfunction you actually have; was it systolic or diastolic?
To add to my previous querry - my performance on TMT and stress thalium is excellent - average 16 mts.