I'm no expert but since no one else has replied, I'll give my two cents. I had heart failure at age 22 because my mitral valve ruptured. I was born with a disease that made me more predisposed to that happening, but I do think that drugs are what caused it to completely tear. At the time I was partying hard with alcohol, marijuana, and even some molly.
It's been a full 2 years now and my EF is NEARLY normal. I don't party nearly as hard as I used to, but I lack self control and I do pot, Adderall, and occasionally drink. Honestly I think it's a miracle my EF managed to go up with all the stupid crap I do, and I'm willing to bet that if I had been smart enough to just STOP all drugs for a year or so while I recovered, I could have a completely normal EF.
You can get better. You're young and your heart can repair itself. Did your doctor put you on any medications? Those can save your life. You will be able to exercise again, but if I were you I would just stay away from the partying. If you keep living that lifestyle then all your friends will be partiers and it will be incredibly hard to stay away from bad things. Just remember, now that you've had heart disease once you're at risk for the rest of your life. You knew that drugs were bad for you before, but now it's different and you're way less likely to get away with it.
Every time I do even soft drugs like weed, I regret it because I feel in my heart that it's harmful. I want nothing more than to live a totally clean lifestyle and that's my goal no matter how hard I struggle..
Best of luck to you. Stay positive, it makes all the difference.