I Am 35 Yrs Old. 6yrs Ago It Revealed That

i am 35 yrs old. 6yrs ago it revealed that my hear is enlarge & ef is 25%. That time i took medicine. But due to some problem i did not take any medicine for 4yrs. Now i went to a doctor for 2months. He is saying i had to place a AICD device. I am worried. I do not want to take any device now. Is there any way to improve EF. I am non smoker, non alcholic.