Study Identifies Incidence and Origin of PEA

Abstract & Commentary

By John P. DiMarco, MD, PhD,Professor of Medicine, Division of Cardiology, University of Virginia, Charlottesville. Dr. DiMarco receives grant/research support from Medtronic, is a consultant for Medtronic, Novartis, and St. Jude, and is a speaker for Boston Scientific.

Source: Teodorescu C, et al. Factors associated with pulseless electric activity versus ventricular fibrillation. The Oregon Sudden Unexpected Death Study. Circulation. 2010; 122:2116-2122.

Over the last twenty years, the proportion of cardiac-arrest victims in whom pulseless electric activity (PEA) is identified rather than asystole or ventricular fibrillation as the initial ECG finding has been increasing. In this report from The Oregon Sudden Unexpected Death Study, the clinical characteristics and risk factors for out-of-hospital PEA are reported. The Oregon Sudden Unexpected Death Study is an ongoing prospective, epidemiologic study of out-of-hospital cardiac arrest in Portland, OR. Factors from each sudden cardiac-arrest (SCA) case are systematically recorded. These data include any known information about the patient's prior cardiac history. This report includes data from 1,277 cases of adult SCA in whom resuscitation was attempted. The mean age was 65 years and 67% of the victims were male. The cardiac arrest had been witnessed by laypersons in 61% of patients, by first responders in 6% of patients, and was not witnessed in 33%. The mean response time from discovery of the SCA victim to arrival of the first responder was relatively short, 6.8 + 3.2 minutes. However, the response time was greater than 4 minutes in 73% of cases. The initial rhythm documented was PEA in 24.9% of cases, ventricular fibrillation or ventricular tachycardia (VT/VF) in 47.8%, asystole in 25.5%, and other rhythms in 1.8%. SCA victims with PEA as their presenting arrhythmia were older than VT/VF cases by five years, and PEA was more common among women (37%) vs. men (26%). Blacks also were more likely to have PEA than whites or Asians. More patients with VT /VF had a witnessed cardiac arrest (72.2.%) compared to those with PEA (59.7%) or those with asystole (41.5%). Interestingly, there was no difference in response time between the PEA , VT/VF, and asystole groups.

Several variables in the cardiac history were examined in the study group. Documented coronary artery disease and hyperlipidemia were more common in the VT/VF group than in the PEA or asystole groups. Pulmonary disease and syncope were considerably more common in the PEA group. Multivariate regression models identified age, black race, history of syncope, and female gender as independent predictors of PEA vs. VT/VF. When patients with PEA were compared to those with asystole, a history of syncope again appeared to be more common.

The authors concluded that age, black race, female gender, pulmonary disease, and syncope are risk factors for PEA in a cardiac arrest population. The reason for this pattern remains unexplained.

Commentary

This paper presents important epidemiological data about the electrical mechanisms responsible for a cardiac arrest. The major new finding is that a history of syncope is linked to PEA. As noted by the authors, PEA is now seen as the presenting arrhythmia in one-quarter of SCA victims. These patients have a much worse prognosis compared to patients found to be in VT/VF. The authors identified a history of syncope as an independent predictor for PEA as the initial finding during cardiac arrest. The reason for this is unclear. However, one might speculate that patients with PEA are more likely to have vascular collapse associated with cardiac arrest. Whether this is due to changes in autonomic nervous system function or to some other etiology is, at present, uncertain. There is some experimental evidence that PEA, like syncope, may be related to parasympathetic overactivity, and atropine is part of the regimen recommended for PEA in the current ACLS guidelines. Further data from prospective epidemiologic surveys and possibly clinical trials will hopefully clarify these issues in the coming years.