Our vet has said that my dog Luka has a very slight heart murmur. ( I have asked for a cardio referral) He is 2.5 years and is very active. We give him lots of excersise which he seems to love. He always runs aroundd when he is off the lead. He never pants or seems breathless. Could over exertion have caused this early onset. I f so what levels should we now adopt.

Hope someone can help