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Pulseless Electrical Activity Asystole

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Pulseless electrical activity (PEA) and asystole are related cardiac rhythms in that they are both life-threatening and unshockable. Asystole is a flat-line ECG (Figure 27). There may be 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 patches have good contact with the individual, leads are connected, 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.

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 return of spontaneous circulation (ROSC), proceed to post-cardiac arrest care. Atropine is no longer recommended in cases of PEA or asystole.

Rules for PEA and Asystole

ACLS Pulseless Asystole Rythm

Figure 27

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.

Reversible Causes

ACLS Reversible Causes Rythm

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 patches 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.


Although there is no evidence that atropine has a detrimental effect during bradycardia or asystolic cardiac arrest, routine use of atropine during PEA or asystole has not been shown to have a therapeutic benefit. Therefore, the ILCOR has removed atropine from the cardiac arrest guidelines.


Preliminary research suggested that epinephrine in higher doses may produce improved results in resuscitation. However, research conducted after the 2010 guidelines publication failed to show any benefit over a standard dose of 1 mg epinephrine. Likewise, the 2010 ILCOR guidelines offered an alternative vasopressor, called vasopressin, which could be used instead of or after the first dose of epinephrine. Subsequent research showed that vasopressin offered no benefit over standard-dose epinephrine. Without a demonstration of superiority, both high-dose epinephrine and vasopressin have been removed, simplifying the ACLS algorithm.

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