I think the OP's got every right to be furious. It'll be here having to deal with the consequences!
That's what makes me side with her. They have two children to think of - she is, he isn't.
With a known but undiagnosed heart issue - which may have been caused by coke use in the past - this man is prepared to take the risk of further damaging his heart (or worse), and is utterly ignoring his wife's concerns.
He cares nothing for the very real risk that he'll be risking his life. Nothing for the even more likely scenario that he'll be damaging an already-weakened vital organ.
It's the OP who'll be picking up the fall out, one way or the other - either as a single parent, or in looking after a man with heart failure (and those of you saying 'it's no issue' need to look up what that means!) and, imo, that does give her the right to be angry and to insist that he doesn't do it!
I don't get MN sometimes - all this he/she can't tell you what to do. No, of course they can't tell me, but I wouldn't be with my partner if I didn't respect him enough to trust him when he tells me I'm doing something daft, and I hope the same is true in reverse.
If this were my DH, he'd be coming home to a locked door, because his attitude is that he cares nothing for what his actions might do to me and to our children - and that's not acceptable to me.
And, yes, I'd say the same about excessive drinking, risky driving, stupid hobbies... the time for those id when you're young and/or (if you must) when the kids have grown up and left home.