Make a list of the people most likely to be present when / if you have a cardiac arrest. Make sure they get trained in CPR.
Make sure those people know how they are going to get you from the recliner onto the floor...or out of bed and onto the floor. If they are strong enough to pick you up and lay you down on your back on the floor, that's super - but most likely, they are not. In that case...If you're in a recliner, they should use the handle to make the recliner as level as possible, throw a cushion onto the floor where your head will hit the floor, grab your ankles and pull until you are on the floor. If you're in bed, they should un-tuck the bottom sheet on the far side of the bed, toss it over you, return to the side of the bed where you are, throw a pillow on the floor where your head will hit the floor, and pull on the sheet until you roll out of bed.
Make sure they know how to make that 911 call: when you say "911 what is your emergency?, they should tell the (make-believe) operator (a) where you are, (b) what is wrong, (c) what you are doing about it. If you are in a locked home, they should make the call while walking to the front door to unlock it.
This sounds silly, but can you think of something that you didn't do better on your second try? Right. So why should they wait for the real emergency to practice calling 911? Tell them to eave the phone off when they practice. Do they have to enter the PIN code to dial 911? ...or will 911 calls bypass the phone's security. Tell them "Go ahead. Make a "make believe" call to 911."
Oh, by the way. As long as you are getting all those around you prepared to deal with your potential cardiac arrest...return the favor. Get yourself trained, too.