I recently discovered I have a heart condition? Help!

I wasn't quite sure what thread to post this in so I decided on support since I really need some. Recently this week I have come down with bronchitis (what started out as a sinus infection) and am slowly recovering. I had an echocardiagram (?) done on Wednesday because my doctor heard my heart murmur. It turns out I have a leaky heart valve in the bottom left of my heart. I potentially may not be able to be as physically active as I need to be to lose and maintain my goal size.

I am really discouraged and depressed because I have worked so hard to get to where I am now and if I have to just quit exercising, I'll be ruined. Exercising gave me happiness and a purpose.

On the off chance, if I can work out some, can anyone recommend low impact cardio workouts that will burn fat but won't cause any harm to my already "damaged" heart?

Thanks so much!