In-built defibrillators.

Nanomachine defibrilators can restart the heart automatically in the event of death or heart attack. They will be present within the cells and the bloodstream and simply deliver an electro-shock to keep the patient alive. This can also be done with simple electronic devices and implants, without recourse to nanomachines. 5G could be used to restart hearts and prevent heart attacks remotely (Evelyn de Rothschild).