Non-fibrillatory cardiac arrest is a term used to encompass the defined cardiac arrest rhythms, pulseless electrical activity (PEA) and asystole, arrest rhythms that are distinct from ventricular fibrillation or pulseless ventricular tachycardia. Until recently, the term electromechanical dissociation (EMD) was used in place of PEA. EMD was defined as the presence of electrical complexes without accompanying mechanical contractions of the heart. Several studies have demonstrated that often during EMD arrest there actually is mechanical cardiac activity associated with the electrical complexes seen on a cardiac monitor. PEA, defined as organized electrical activity with the absence of clinically detectable pulses, is thus a physiologically more appropriate terminology. Patients in asystole, by definition, have no discernible ventricular activity by electrocardiography or ultrasonography, and no associated perfusion. This chapter will focus on the diagnosis and treatment of PEA subsets.

The incidence of PEA during cardiac arrest appears to be changing. Prior to 1990, PEA was reported to be the initial presenting rhythm in approximately 20% of hospitalized patients who are monitored at the onset of cardiac arrest and 16.5% of patients who present to a prehospital system in cardiac arrest. Several recent studies have reported the incidence of PEA to be 35%–40% of all in-hospital resuscitation events. Data from the Ontario province advanced life support (OPALS) study found over a 4-year study period an increasing PEA incidence of 19.9% to 24.5%, with a coexisting shortened EMS system response time.8 The OPALS group further demonstrated a 50.1% incidence of PEA arrests in the subgroup of patients that arrested after the arrival of EMS.