Monty is 12 and I've known about his murmur, since he was about nine, when it was barely noticeable. At 12 it is just above middling and he has since Christmas given a single cough on some mornings, though this could partly be due to his licking his long coat .
The vet said he was borderline for medication, so gave me the option and I went for it. he has Fortekor and Frusemide and had his second consultation last week. His heart rate, which was slightly above normal, is even nearer to normal, now and his gum response is good, so the drugs were worth it.
Modern drugs are very good as these two plus Vetmedin, gave Izzy over two years of quality life and he had a a very severe murmur.
The important thing is the way a dog's body copes with the problem, rather than the actual severity of the murmur.
Barbara, Monty, Joly and Teddy.