Text: When a patient displays a cardiac flatline, the treatment of choice is cardiopulmonary resuscitation and injection of vasopressin (epinephrine and atropine are also possibilities). Successful resuscitation is generally unlikely and is inversely related to the length of time spent attempting resuscitation. Defibrillation is not recommended, despite commonly appearing on medical dramas as a remedy for asystole, but can be used for certain other causes of cardiac arrest.

Question: can you restart a heart that has flatlined?
yes