ACLS Advanced cardiac life support (Latest 2020 AHA)

0 of 17 lessons complete (0%)

Heart rhythms

Asystole and Pulseless Electrical Activity (PEA)

These two rhythms are non-shockable forms of cardiac arrest. A shock (defibrillation) is not indicated in such cases.


Systole is the “squeezing period” of the heart that helps in pumping the blood out of the heart to various body parts. Diastole is the filling period. A’systole’ means there is no contraction = No systole.

Asystole, flat line. Img courtesy – D Dinneen~commonswiki CC BY-SA 3.0

The ECG wave form appears on ECG monitor only when there is a contraction of heart muscle. As there is no contraction of muscle in asystole, all you see on the monitor is a flat line. (Differentiate from Fine VF explained in VF lesson)

Flatline protocol

When the monitor seems to show a flat line, you have to make sure (quickly) if it’s an asystole or some error.

  1. Check the leads – Check if they are properly attached on the body/chest.
  2. Change the lead – Normally, the cardiac monitor shows lead 2 by default. Try switching to another lead – Lead 1 or 3.
  3. Increase the amplitude – Each monitor has a way to increase or decrease the gain/amplitude. Increase the gain to see if it’s still a flat line.

Once you have confirmed it’s a flatline, start CPR as described in the Cardiac arrest algorithm (Under rhythm management module).

Pulseless electrical activity (PEA)

Sometimes, the heart will not be pumping effectively but you might see some organized rhythm on the monitor. The rhythms don’t fit into shockable rhythms. This was previously called as electromechanical dissociation (EMD). This is lack of a palpable pulse in the presence of organized cardiac electrical activity on the monitor.

This is Sinus tachycardia ECG. But if there’s no pulse, we call it pulseless electrical activity (PEA). An organized rhythm with no pulse.

What is the difference between Asystole and Pulseless electrical activity (PEA)

In asystole, there is no electrical activity from pace maker, but in PEA, there is an electrical activity but that is not generating an effective cardiac muscle contraction and we will not feel a palpable pulse

The management is similar to asystole management. Check Cardiac arrest algorithm (Under rhythm management module).