Pulseless electrical activity
The diagnosis of pulseless electrical activity (PEA), also known as electromechanical dissociation (EMD), refers to the presence during cardiac arrest of electrical activity of the heart, in the absence of a ventricular tachyarrhythmia, but no measurable cardiac output . PEA is one of the non-shockable rhythms, the other being asystole.
Pulseless electrical activity is one of the possible states found in an unconscious patient who has had a cardiac arrest. It is characterized by the presence of cardiac electrical activity, which may be organized or disorganized, in the absence of a ventricular tachyarrhythmia (i.e. ventricular tachycardia/fibrillation), but no measurable cardiac output. Lack of output may be recognized by the absence of any arterial pulse or systolic blood pressure .
Classically the etiologies have been described as the 4 Hs and 4 Ts :
- hypoxia (commonest)
- tamponade (cardiac)
- toxins: includes carbon monoxide, opioids, methadone, benzodiazepines
- tension pneumothorax
A recent large retrospective Swiss study reviewing 1,866 out-of-hospital cardiac arrests (over a 10-year-period) demonstrated that the most frequent cause of pulseless electrical activity was hypoxia, accounting for almost 25% of all cases. Acute coronary syndrome was cited as the primary cause in 12.5% cases. Other cardiac dysrhythmias, such as long QT syndrome, were also common etiologies. Most interestingly was the discovery that intracranial hemorrhage, in 80% of cases subarachnoid hemorrhage, was the underlying precipitant of PEA in almost 7% of all cases .