Either your wife's phone number or your mistress's phone number, but not both (unless you want to entertain the emergency room staff).
It does happen. I knew a guy who told his wife he went for long bike rides. He actually went for short rides to his girl friends house. I forget the details of his heart attack, but do recall that he woke up to find both the wife and girl friend in the hospital room. Some how he eventually managed to get back into the good graces of both.