Heart murmur

[normag]

not sure if Im in the right forum but here goes anyway.
My female shiba has been diagnosed with a heart murmer
its not a useual problem with the breed and she is such a
physical dog I have a hard time believing this. She runs like
the wind and doses'nt come back breathless. She is now
on a special diet and needs to take a pill everyday.
I feel so bad, did I do somthing wrong ??