Question

Why do cats harts beat so fast

Answer 1

Cats are almost scared of every little sound, even in their sleep they are constantly alert just in case they're gonna be attacked by an alien. jk, no one really knows why cats are so paranoid of everything, but because of that their body continuously uses energy, which causes theyre heart to beat quicker.

Answer 2

Well have you ever heard how fast a humming birds heart beat goes? no?
well ill tell you that it goes 1,260 beats per minute which is A LOT. well remember how they fly? cmon you remember this one... really fast!
and just for my sake they go 70 times per second! And in order to fly this fast they are always going from flower to flower collecting that sweet nectar juice. That is their source of energy. 
Cats are a little bigger and dont use as much energy as those birds but they have energy packed in their muscles so that when.... they get scarred... they can jump or run across the room to get away from it:)
So they always have the energy to be curious and a scaredy cat :D