Cat with thickened heart muscle?

Hey, This probably doesnt really help, but my cat was born with a heart murmer, but was told he would grow out of it which he has..... Im not sure if older cats can out grow this condition but it is not a major thing.... The only thing that will really bother him is very very load noises or being extreamly scared. However dont get worried if your cat runs around a lot or over exerts himself as this will only make it stronger so make sure you dont do what we did for a while and treat him like he is fragile.... If he seems back to his old self im sure he will be fine.... Just look after him.... But dont spoil him to much or he will turn into a piggy like my 7 month old rascal!!!! Hes going to be soooooooo fat!