Pulseless electrical activity (PEA) is a form of cardiac arrest in which the heart shows organised electrical activity on an ECG monitor, but is not producing a detectable pulse or effective cardiac output. Because the electrical signals appear relatively normal, PEA can be mistaken for a functioning heart rhythm, but the heart muscle is not responding with effective contractions.
**Why it occurs**
PEA occurs when there is a disconnect between the electrical system and the mechanical pumping function of the heart. Underlying causes are typically grouped using the “4 Hs and 4 Ts” framework used in resuscitation training:
– **4 Hs:** Hypoxia, Hypovolaemia (severe blood loss), Hyper/Hypokalaemia (potassium imbalance), Hypothermia
– **4 Ts:** Tension pneumothorax, Tamponade (fluid around the heart), Toxins/overdose, Thrombosis (pulmonary embolism or coronary occlusion)
**Treatment**
Defibrillation is not effective in PEA because the underlying problem is not a shockable arrhythmia. Treatment focuses on CPR to maintain circulation while identifying and reversing the underlying cause. The specific treatment depends on the cause: for example, needle decompression for tension pneumothorax, pericardiocentesis for tamponade, or fluids for severe hypovolaemia.
**Prognosis**
PEA has a poorer prognosis than ventricular fibrillation, partly because the underlying cause is often a severe physiological problem that is harder to reverse, and partly because the absence of a shockable rhythm means the standard defibrillation pathway does not apply.
**Distinction from asystole**
Both PEA and asystole are non-shockable cardiac arrest rhythms. The difference is that asystole shows no electrical activity at all on the ECG (a flat line), whereas PEA shows organised electrical signals without corresponding mechanical output.
« Back to Glossary Index