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Pulseless Electrical Activity (PEA) & Asystole

Pulseless electrical activity (PEA) and asystole are related cardiac rhythms in that they are both life-threatening and unshockable cardiac rhythms. Asystole is a flat-line ECG (Figure 27). There may be a subtle movement away from baseline (drifting flat-line), but there is no perceptible cardiac electrical activity. Always ensure that a reading of asystole is not a user or technical error. Make sure pads have good contact with the individual, leads are connected, the gain is set appropriately, and the power is on. PEA is one of many waveforms by ECG (including sinus rhythm) without a detectable pulse. PEA may include any pulseless waveform with the exception of VF, VT, or asystole (Figure 28).

Hypovolemia and hypoxia are the two most common causes of PEA. They are also the most easily reversible and should be at the top of any differential diagnosis.

If the individual has a return of spontaneous circulation (ROSC), proceed to post-cardiac arrest care.

Rules for PEA and Asystole

A flatline ECG reveals no electrical activity and is reserved for asystole, whereas PEA reveals organized or semi-organized electrical activity in the absence of a palpable pulse.

Figure 27

ORGANIZED OR SEMI-ORGANIZED Any rhythm without a pulse.
Rate Any rate or no rate.
P Wave Possible P wave or none detectable.
PR Interval Possible PR wave or none detectable.
QRS Possible QRS complex or none detectable.


Asystole Regularity The rhythm will be a nearly flat line.
Rate There is no rate.
P Wave There are no P waves present.
PR Interval PR interval is unable to be measured due to no P waves being present.
QRS There are no QRS complexes present.

Table 8

Reversible Causes

Figure 28

Reversible Causes of Cardiac Arrest
The H’s The T’s
Hypovolemia Tension pneumothorax
Hypoxia Tamponade
H+ (acidosis) Toxins
Hypo/Hyperkalemia Thrombosis (coronary)
Hypoglycemia Thrombosis (pulmonary)
Hypothermia Trauma (unrecognized)

Table 9

Take Note
  • Always verify that a reading of asystole is not equipment failure. Make sure pads make good contact with the individual, all cables are connected, gain is set appropriately, and the power is on.
  • Hypovolemia and hypoxia are easily reversed and are the two most common causes of PEA.


Epinephrine is still the best choice according to 2020 guidelines. Of sixteen observational studies on timing in the recent systematic review, all found an association between earlier epinephrine and ROSC for patients with non-shockable rhythms, although improvements in survival were not universally seen.

For patients with a shockable rhythm, the literature supports prioritizing defibrillation and CPR initially and giving epinephrine if initial attempts with CPR and defibrillation are not successful.

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