I'm not a health professional, so keep that in mind, but it sounds a bit like a medical urban legend that has no basis in fact. I am a volunteer in a in a Cardiac hospital, and commonly family dogs are allowed to be visitors with patients who have had bypass. The furry friends have to endure some common paw-washing procedures that we all should do entering a CVCU, and like humans, they are instructed not to sit on the bed.