Stieglis R, et al. - Given the uncertainty concerning how many automated external defibrillators (AEDs) and text message (TM)-responders should be incorporated in a program of early defibrillation using volunteer rescuers in order to be successful, researchers sought to determine the required density of available and activated AEDs and of alerted TM-responders required for early defibrillation in residential areas via implementing a dispatcher driven alert-system using TMs (TM-system) directing local rescuers (TM-responders) to out-of-hospital cardiac arrest (OHCA) patients. Between 2010–2017, OHCA cases with the TM-system activated in residential areas were included. For each case, they calculated densities/km² of activated AEDs and TM-responders within a 1,000 m circle. Further, they calculated time intervals between 112-call and first defibrillation. In total, a shockable initial rhythm was reported in 813 patients (45%). In 17%, the first shock was delivered by a TM-system AED. A decrease in time to defibrillation in residential areas was observed with increasing AED and TM-responder density within a TM-system. They noted competition of AED and TM-responders only with ambulances, not with first responders. For the earliest defibrillation, the suggested density of AEDs and TM-responders is 2 AEDs/km² and > 10 TM-responders/km².