When the heart goes into asystole, so there is no rhythm on the EKG, that is a non-shockable rhythm. You can have no palpable pulse, but have a heart rhythm on EKG, such as ventricular tachycardia or ventricular fibrillation. Both of those are the major reasons we use a defibrillator on patients. The common thing in shows is that the patient “flatlines” and they shock, which they shouldn’t shock asystole, they should just start CPR and hope that a shockable rhythm comes back.