when your depressed you usually push people away.
1. i think you should leave a message on his voice mail, email whatever and tell him that you are here for him when he's ready to talk and that you care about him.
2. if you believe in God pray for him.
3. i would give him some space, it would be easy for him to not answer his phone or his door.
he has to be strong and get help for himself. i think it would be dangerous if he has a heart problem and he' drinking, and taking a lot of medications.
dont stress yourself out over this and dont apply pressure.