Semi-automatic external defibrillation and implanted cardiac pacemakers: understanding the interactions during resuscitation

Many emergency medical service (EMS) systems are currently implementing semi-automatic external defibrillation (AED) by emergency medical technicians. Surprisingly little information is available on the possible interactions between AEDs and implanted cardiac pacemakers. Therefore, at present there are no clear guidelines for the use of AEDs on patients having a cardiac pacemaker. During resuscitation, multiple interactions between pacemakers and AEDs are possible. External defibrillation can cause damage to several functions of the pacemaker. On the other hand, the presence of pacemaker spikes during cardiac arrest might prohibit recognition of the ventricular fibrillation by the AED. We report on two resuscitation attempts in which the interaction between the ventricular fibrillation, an implanted dual chamber pacemaker and the AED was decisive for the defibrillation success. A clear understanding of these possible interactions is necessary for the further refining of diagnostic algorithms and clinical strategies of prehospital defibrillation.