I've had a couple dogs that have died from heart related issues. Both of them had heart murmurs that got progressively worse over the years, but none were diagnosed as young as yours. Most didn't get it until around 5+ years old. Both (neither dog a GSD) died from heart failure at around 10 years old, but it was a life long thing once diagnosed. Echocardiograms every six months and what not. It gets expensive.
In my experience, this is something you should take very seriously. What did you vet say? Did you let your breeder know?