Citizen Responders and Bystander Defibrillation

Quick Takes

  • Smartphone activation of citizen responders increases initiation of CPR and defibrillation when these responders reach the scene of out-of-hospital cardiac arrest (OHCA) before EMS.
  • Randomized trials are ongoing to quantify the impact of citizen responder systems on survival after OHCA.

Study Questions:

What is the association between arrival of citizen responders before emergency medical services (EMS) and bystander cardiopulmonary resuscitation (CPR) and bystander defibrillation at the scene of out-of-hospital cardiac arrest (OHCA) during the first year of implementation of a citizen responder system using a smartphone app?


In this prospective observational study in Copenhagen, Denmark, citizen responders using the HeartRunner app were dispatched to start CPR or retrieve an automated external defibrillator (AED) (the first responder was instructed to start CPR, and others to retrieve AEDs). OHCAs where at least a responder arrived before EMS were compared with OHCAs where EMS arrived first. Primary outcomes were bystander CPR and bystander defibrillation, which included CPR and defibrillation by citizen responders and random bystanders.


Citizen responders were alerted in 819 suspected OHCAs, of which 438 (54%) were confirmed cardiac arrests eligible for inclusion. Citizen responders arrived before EMS in 42% of all OHCAs. When citizen responders arrived before EMS, the odds for bystander CPR increased 1.76 times (p = 0.027) and the odds for bystander defibrillation increased 3.73 times (p < 0.001) compared with OHCAs in which citizen responders arrived after EMS.


Arrival of app-dispatched citizen responders before EMS was associated with increased odds for bystander CPR and a >3-fold increase in odds for bystander defibrillation.


Bystander CPR and early defibrillation are critical to survival of patients with OHCA. The authors showed that dispatching citizen responders through a smartphone app is associated with increased bystander CPR and defibrillation and is safe for the citizen responder. The study was not designed to show how many minutes before EMS arrival the citizen responders performed CPR or defibrillation, and no survival data are presented in this paper, although a randomized clinical trial is pending (the HeartRunner trial). The present study was conducted in Copenhagen, Denmark. A large number of registered citizen responders were health care workers (about 25%) and 99% had completed CPR training, raising doubts about the generalizability of the findings to more remote areas with different economic and social milieu.

Clinical Topics: Acute Coronary Syndromes, Arrhythmias and Clinical EP, Heart Failure and Cardiomyopathies, Prevention, Implantable Devices, EP Basic Science, SCD/Ventricular Arrhythmias, Atrial Fibrillation/Supraventricular Arrhythmias, Acute Heart Failure

Keywords: Acute Coronary Syndrome, Arrhythmias, Cardiac, Cardiopulmonary Resuscitation, Defibrillators, Electric Countershock, Emergency Medical Services, Emergency Responders, Heart Arrest, Heart Failure, Mobile Applications, Out-of-Hospital Cardiac Arrest, Secondary Prevention, Survival

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