More from Catster (/Dr. Stern at UC-Davis): "Facts on Feline Heart Disease."
Short personal story: I had a cat growing up (his name was Moon Pie- can you guess what colors?) and at one of his first kitten exams, our vet noticed he had a heart murmur, so he referred us to a specialist for an echocardiogram. First of all: this must have been like 2002, so I have no idea how there was a veterinary cardiologist operating in Burlington, Vermont, but there you go.
So we have his heart imaged, and the cardiologist prescribes medication for him. To my everlasting shame, we never actually tried to GIVE him the medication (it was one tiny pill)- we would just put the pill in his bowl of food, and sometimes he would eat it and sometimes he wouldn't. We didn't know any better! Moon Pie always suffered from an intermittent cough that was probably the result of his poorly-managed heart problem, but he lived a nice long life and ended up passing away days after my childhood dog (and his best friend).