Pulseless electrical activity (PEA) refers to a medical condition in which the electrical activity or rhythm of a person's heart is relatively normal but the mechanical pumping action of the heart does not respond. This lack of response results in cardiac arrest. A patient who has PEA has no pulse, is unconscious, is in respiratory arrest and is, therefore, clinically dead.
PEA is one of the heart rhythms, along with asystole, that is not shockable with a defibrillator such as automated external defibrillator (AED), because defibrillation is of no use. The electrical activity is already intact with pulseless electrical activity, so there is no electrical chaos that can be remedied by defibrillators. This is why automatic AEDs will not deliver a shock to the patient and semi-automatic AEDs will not advise the delivery of a shock in such a case. Although normal electrical rhythm is vital to prevent cardiac arrest, the importance of the heart muscle cannot be overlooked. Electrical activity and the heart muscle must work together to produce normal heartbeats.
The causes of pulseless electrical activity almost always relate to the patient having a severely and terminally sick heart, which might be caused by a number of health problems, including cancer. Approximately four out of every 10 patients in cardiac arrest suffer from one of the nonshockable rhythms, either asystole or PEA. Although an AED is of no use and there is very little hope of resuscitating the patient, healthcare providers, particularly emergency medical technicians (EMTs) and paramedics, resort to cardiopulmonary resuscitation (CPR) on the way to a medical facility where care can be transferred to a doctor, who can pronounce death.
Performing CPR is also all that a layperson can do for someone suffering cardiac arrest caused by pulseless electrical activity until the arrival of emergency medical services (EMS). The only time that CPR should not be performed is if the person has a do-not-resuscitate (DNR) order, which is a legal document that must be honored by laypeople and healthcare providers. If an AED is not used or is not available to analyze the heart rhythm of someone in cardiac arrest, there is no way to know whether the arrest was caused by pulseless electrical activity or some other rhythm that might or might not be shockable. This is why it is important to perform CPR in the absence of a pulse.