Defibrillators on flatlined patients?

We've all seen the scenes in movies and TV shows where a patient is lying still, and a monitor beside them makes a constant tone as the activity line remains flat. Then a doctor or nurse calls "Clear!" and the electric pads are applied, only for the patient to stir back to life as the monitor shows the line has peaks again.

The problem? Medical experts will confirm this doesn't happen. The electric shock is to stabilise a heart which isn't beating correctly, not to revive one which has stopped. This myth is so widespread in the media because it contains so much drama. There's nothing better to move a story along, or give one a happy ending, than a character being brought back to life. Unfortunately, that's just not how it is in this case.

First defibrillator demonstrated in 1899

In 1899 in Switzerland, two physiologists demonstrated  that electric shocks could cause ventricular defibrillation in dogs, and increasing the voltage would reverse it. By 1933 the idea had been developed By Dr. Albert Hyman who attached a needle and inserted this directly to the heart, with a charge.The first use on a human heart was in 1947, on a 14 year old boys open heart. In the mid 1950's, higher voltages still were used which enabled the pads to be applied to the unopened chest for the first time, and it is this design which we largely see today.

Even Wikipedia points out the popular concept of them reviving "dead" hearts is exaggerated, to put it mildly.

In modern times, all ambulances carry portable defibrillators and there is a movement to have them readily available in many city blocks with easy to use signage and instructions, and smartphone apps written to locate the nearest one in an emergency.