Rachel, very sorry about the diagnosis of your pup. I don't know if the diagnoses was made via your local vet or a cardiologist but if you have not seen a cardiologist you may wish to do so to get their opinion. 0
My oldest pup Aspen (who just turned 6 years old) was recently diagnosed with early onset mitral valve disease after a recent vet visit detected a new heart murmur. He had some concerning blood work results, which when combined with the onset of the murmur prompted them to make me an appointment with a cardiologist (they were concerned he had an infection in his heart). An echocardiogram was performed, which led the cardiologist to her diagnosis. Mitral valve disease also leads to heart failure sometime in the future, but as with DCM, they cannot predict when. With Aspen's disease there are no medications to administer until he is showing signs/symptoms of congestive heart failure.
I don't have experience with DCM (but have been researching diet induced dilated cardiomyopathy recently due to the attention it has been receiving), but I can lend you my approach and insight on Aspen's condition. I am obviously not happy with the diagnosis and the uncertainty around it. I have notified his breeder and provided them with the cardiologist's report. I was advised by the cardiologist not to limit his exercise, but let him determine his own activity level (ie. no more chuck it ball fetch). He is to have his heart checked by our local vet every 6 months to monitor the progression of the murmur (good news from the cardiologist - the vet had said his murmur was a grade 3/6, the cardiologist confirmed it as a grade 1 or 2/6). I am now monitoring his breathing rate and heart rate (more for my own information than anything else, but I feel like I need to do something). Other than that I'm loving on my pup the best I can, and continuing to give him the best Vizsla life he deserves. I'm trying not to focus on a time frame - there's no point. Dogs live in the moment and I am going to try to as well. The cardiologist did say that although heart problems have not been common in Vs, she is started to see more Vizslas with them.
More than anything I just wanted to offer you support. Aspen was diagnosed a couple of weeks ago and since then I have combed every article, forum, facebook group, etc for anything that might help.
Fingers crossed that both our pups remain symptom free for as long as possible.