I am 51 yrs old with idiopathic dcm and a bi vent icd. ef now is 38%. told i need to exercise but when i try to walk or exercise i'm done for day?

Start slow... : The benefits of regular aerobic exercise are well documented, and your doctor is right in recommending it. It's discouraging when, in the beginning, you get wiped out in a short time. But if you persevere, you will be able to gradually build up, over weeks, to about 30 mins a day. The first few days & weeks will be difficult, but daily repetition will allow you to get there! good luck.