I have a 4 year old black lab who has "EIC" (Exhaustion Intolerance & collapse). I pretty much have that under control and he is doing quite well thanks to someone's advise from this website The vet advised me that he has an enlarged heart as well. I noticed lately that his breathing is very heavy after playing fetch for just a few minutes. I am going to give him Omega 3-6 for his heart...is there anything else that I can give him. I don't want to start pumping him full of synthetic medicine as I fear that that could pose even more problems.
I would take him for more frequent short walks, and not play the games that include heavy exertion.There are human drugs that strengthen the left side of the heart and lower blood pressure. Perhaps your vet would consider your dog for that treatment.