Yeah but this is referencing the movie trope where the person has a fully stopped heart and they shock it back to life. In reality applying cpr is just keeping the blood pumping to supply the brain with oxygen in the hope the body restarts the heart itself. That’s why modern defib machines check the nerve impulses to see if shocking it would help. Of there is no heartbeat, it won’t help and will refuse to shock. Once the body restarts the heart but the rhythm isn’t correct shocking can help. The shocks also aren’t huge shocks where the person violently lurches up and putting in more energy won’t help either. The machine checks the rhythm and applies a series of shocks to help the nerves regain their normal pattern and thus tell the heart to pump in the right sequence and speed. Just randomly zapping will probably do more harm than good.

It’s pretty nice the emergency defib machines we have all over the place these days are smart enough to help without needing to know how it does their thing. Because 80s and 90s TV and movies have muddied the water quite a bit.