At the very least we need a grand, logical explanation as to why he needs a pacemaker. Good god, has it not been established that speedster metabolism puts healing into hyperdrive? We've seen multiple broken bones healed, wounds closed, noxious chemicals expelled ---a freaking EYEBALL restored--- all within an incredibly short period of time. How is a heart more complicated?
I want to see either the timeline restored or the Speed Force formed into a functioning cardiovascular organ, by golly! I can see that...a heart of pure speed force construct made to work and stay in form awake or asleep.