I thought about the heart monitor too. The design of the mask that the “Joker” wears resembles the line indicating the heart pulses, plus the sound of the Roadrunner being similar. I knew about the Looney Tunes reference from before the issue was released thanks to Bleeding Cool, but you people posted some great theories about the reason of the chase! I didn’t give it much thought. Probably I was too occupied being amazed by the incredible art