Pulseless electrical activity (PEA) is one of the trickiest cardiac arrest rhythms to identify because the ECG alone can look almost normal. Unlike ventricular fibrillation, which produces a chaotic, unmistakable tracing, PEA shows organized electrical activity on the monitor while the heart fails to produce a pulse you can feel. That combination of electrical activity plus no pulse is the defining feature, and it means PEA is never diagnosed from the ECG strip alone.
What PEA Actually Looks Like on a Monitor
PEA has no single signature pattern. The rhythm on the screen can range from something that resembles a normal sinus rhythm to slow, wide, bizarre-looking complexes. What makes it PEA is the clinical context: organized electrical complexes are visible, but when you check for a pulse (within 10 seconds, per AHA guidelines), there is none.
This is the critical distinction from the two other cardiac arrest rhythms you need to differentiate it from. Asystole shows a flat or nearly flat line with no organized electrical activity. Ventricular fibrillation shows a chaotic, irregular waveform with no identifiable QRS complexes. PEA sits between these extremes: the monitor displays recognizable waveforms, yet the heart isn’t pumping blood effectively.
Common ECG Patterns in PEA
Although PEA doesn’t have one unique look, research on in-hospital cardiac arrests has identified patterns that appear frequently. In one study of 51 PEA episodes, 90% showed widened QRS complexes (120 milliseconds or greater), and 63% showed both a wide QRS and a slow heart rate, a combination described as “wide-slow.” Only 6% of PEA episodes had a completely normal-looking ECG pattern.
So while PEA can technically present with any organized rhythm, the most common presentation is a slow rhythm with wide, stretched-out QRS complexes. If you see a bradycardic, wide-complex rhythm on the monitor and the patient has no pulse, PEA should be your immediate working diagnosis.
Why QRS Width Matters
The width of the QRS complex in PEA isn’t just a visual feature. It provides a clue about what’s causing the arrest. Wide QRS PEA (120 ms or greater) is strongly associated with dangerously high potassium levels. In a study comparing wide and narrow QRS PEA, nearly 50% of patients with wide QRS complexes had elevated potassium, compared to about 27% in the narrow QRS group. After adjusting for other factors, wide QRS PEA carried roughly three times the odds of high potassium being the underlying cause.
Narrow QRS PEA, on the other hand, suggests the heart’s electrical conduction system is still functioning relatively normally, but something else is preventing effective pumping. This points toward mechanical causes like cardiac tamponade (fluid compressing the heart), massive blood loss, or a large blood clot in the lungs.
Thinking about QRS width as a fork in the road helps narrow down the reversible cause faster, which is the whole point of recognizing the rhythm in the first place.
How PEA Differs From a Normal Rhythm
This is where many learners get confused. A PEA tracing can have P waves, QRS complexes, and even T waves that look organized and familiar. The rhythm might run at 70 beats per minute and appear textbook-normal. The only way to distinguish this from a perfusing rhythm is to check the patient. No pulse means PEA, regardless of how reassuring the monitor looks.
This is why experienced clinicians say “treat the patient, not the monitor.” A rhythm check during cardiac arrest always pairs the ECG with a pulse check lasting no more than 10 seconds. If you see organized electrical activity and feel no pulse, you have PEA and should continue CPR immediately.
Pseudo-PEA: When the Heart Is Still Trying
Not all PEA is the same. Some patients have no cardiac motion at all (true PEA), while others have a heart that is weakly contracting but not generating enough pressure to produce a palpable pulse. This second category is called pseudo-PEA.
Pseudo-PEA is defined as having organized electrical activity on the monitor, no palpable pulse, but visible cardiac motion on bedside ultrasound. Some definitions describe it as having a measurable blood pressure below 40 mmHg, too low to feel by hand but not zero. Point-of-care ultrasound has become an important tool for making this distinction, because detecting even weak cardiac contractions changes the treatment approach and generally signals a better chance of recovery. Studies have shown that even brief ultrasound training (as little as 15 minutes) improves the ability to detect these faint signs of cardiac output compared to manual pulse checks alone.
The Reversible Causes to Consider
Identifying PEA on the monitor is only step one. The real clinical challenge is figuring out why the heart has electrical activity but isn’t pumping. The standard framework uses the “H’s and T’s” mnemonic:
- Hypoxia: not enough oxygen reaching the heart
- Hypovolemia: severe blood or fluid loss
- Hypothermia: dangerously low body temperature
- Hyperkalemia or hypokalemia: potassium levels too high or too low
- Hydrogen ion excess (acidosis): blood becomes too acidic
- Tension pneumothorax: air trapped in the chest compressing the heart
- Tamponade: fluid around the heart preventing it from filling
- Toxins: drug overdose or poisoning
- Thrombosis, pulmonary: massive blood clot in the lungs
- Thrombosis, coronary: heart attack blocking blood flow
The ECG pattern helps prioritize this list. Wide, slow complexes push hyperkalemia and toxins higher on the differential. Narrow complexes at a reasonable rate point more toward tamponade, pulmonary embolism, or hypovolemia. No single ECG pattern maps perfectly to one cause, but the QRS width and heart rate serve as useful starting points.
How PEA Compares to Other Arrest Rhythms
PEA and asystole are both classified as non-shockable rhythms, meaning a defibrillator will not help. They are managed with CPR and medication rather than electrical shocks. Ventricular fibrillation and pulseless ventricular tachycardia, by contrast, are shockable rhythms with a distinctly chaotic or rapid pattern on the monitor.
PEA carries a somewhat better initial prognosis than asystole. In a study of nearly 2,800 in-hospital cardiac arrest patients, those presenting with PEA were about 21% more likely to regain a pulse compared to those in asystole. However, when researchers adjusted for patient characteristics, the 30-day and one-year survival rates were not significantly different between the two groups. The initial advantage of PEA likely reflects the fact that some of these patients have pseudo-PEA with residual cardiac function, giving treatment a head start.
Putting It Together: A Step-by-Step Approach
When you encounter a patient in cardiac arrest, the identification process follows a logical sequence. First, look at the monitor. If you see a flat line, that’s asystole. If you see a chaotic, disorganized waveform, that’s ventricular fibrillation. If you see any organized rhythm, from a near-normal sinus pattern to a slow, wide-complex bradycardia, check for a pulse.
If there is no pulse within 10 seconds, you are looking at PEA. Start CPR, then assess the ECG features more closely. Note the QRS width: wide (120 ms or more) or narrow. Note the heart rate: fast, normal, or slow. Use these features alongside the clinical picture to work through the H’s and T’s and identify what’s causing the arrest. If bedside ultrasound is available, use it during rhythm checks to determine whether the heart is contracting at all, which distinguishes true PEA from pseudo-PEA and helps guide the next steps.