Dusty was found to have a very slight heart murmer when she was 7 years old (she's 16 now). The only reason they found it was that she had pneumonia and they were doing alot of testing on her. She's never had medications for it, and we've checked her at work with the EKG and it just shows up occasionally after a few minutes. Every check up (3 times a year) the vet listens to her for quite a while and it's never gotten any worse. He said if I hadn't said something, he'd probably never have even caught it without some luck.

On the human front, I have an uncle that's had a mild heart murmer since he was a child and he has never needed meds for it either.

If your vet recommends testing I'd maybe think of giving it a try at least once to see how severe the murmer is and go from there.