Cardiostimulator

The cardiostimulator is a Federation medical device used to restart a stopped heart.

In 2154, Doctor Phlox attempted to use cardiostimulators to save Major Hayes. Unfortunately, the Major's injuries were too extensive, and he died. 

Doctor Leonard McCoy used a portable version of the device aboard the USS Enterprise (NCC-1701) during an operation on Ambassador Sarek, after the power to sickbay had failed and the operating table's own cardiostimulator had ceased functioning. 

In 2371, The Doctor used a cardiostimulator to revive Commander Chakotay after his bio-neural energy was displaced by the Komar.