How to Identify PEA on an ECG: Patterns & Rhythms

Pulseless electrical activity, or PEA, is not a single rhythm you can point to on a monitor strip. It is any organized electrical activity on the ECG that occurs without a detectable pulse. That makes identification fundamentally different from recognizing, say, ventricular fibrillation or a third-degree heart block. You see a rhythm that looks like it should be generating a heartbeat, but when you check the patient, there is no pulse. The ECG alone cannot diagnose PEA; it takes the combination of what is on the screen and what is absent at the bedside.

What PEA Looks Like on the Monitor

The tracing can look strikingly normal or dramatically abnormal. In some cases, the ECG shows sinus rhythm with clear P waves, narrow QRS complexes, and a reasonable rate. In others, you see wide, bizarre-looking complexes creeping along at 30 beats per minute. Everything in between is possible. The defining feature is organized electrical depolarization of the heart without synchronous mechanical contraction, meaning the electrical signal fires but the muscle does not squeeze hard enough to produce a pulse.

A study of in-hospital cardiac arrest episodes found that roughly 90% of initial PEA tracings showed widened QRS complexes, about two-thirds had what the authors called “wide-slow” patterns (wide QRS with bradycardia), and only around 6% were categorized as normal-looking ECGs.¹ So while PEA can technically present with any organized rhythm, in practice most patients arrive with wide, slow complexes rather than a reassuring-looking tracing. When you see that pattern in a pulseless patient, PEA should be at the top of your mind.

Narrow QRS Versus Wide QRS and What Each Suggests

One of the most useful things you can do when you recognize PEA is look at the QRS width. A structured approach based on dividing PEA into narrow-complex and wide-complex categories helps simplify the differential diagnosis and guide initial treatment.² The reasoning is straightforward: the width of the QRS complex reflects how the ventricles are depolarizing, and different causes of PEA tend to disrupt the conduction system in characteristic ways.

Narrow QRS PEA (complexes under about 120 milliseconds) suggests the heart’s electrical conduction system is still intact. The problem is more likely mechanical: something is preventing the heart from filling or ejecting blood despite a normal electrical signal. Think of conditions that physically obstruct blood flow or starve the heart of volume. Cardiac tamponade, tension pneumothorax, and massive pulmonary embolism all tend to produce narrow-complex PEA because the conduction pathways themselves are fine; it is the plumbing that has failed. Severe hypovolemia fits here too.

Wide QRS PEA (complexes at or above 120 milliseconds) points more toward metabolic or myocardial problems. The conduction system itself is impaired. Hyperkalemia is a classic culprit, as elevated potassium slows conduction through the ventricles and progressively widens the QRS. Severe acidosis, drug toxicity (especially sodium-channel blockers), and profound myocardial ischemia also widen the complexes. When you see wide QRS PEA, your treatment priorities shift toward correcting metabolic derangements rather than relieving a mechanical obstruction.

How Hyperkalemia Shapes the PEA Tracing

Hyperkalemia deserves special attention because it is one of the most treatable causes of PEA, and the ECG gives strong clues. A study comparing wide and narrow QRS PEA found that about half of wide QRS PEA patients had hyperkalemia, compared to roughly a quarter of those with narrow complexes. After adjusting for other variables, wide QRS PEA was nearly three times as likely to be associated with hyperkalemia.³

The classic progression of hyperkalemia on the ECG follows a recognizable sequence even before the patient arrests. Early on, you see tall, peaked T waves. As potassium climbs, the PR interval lengthens, P waves flatten and eventually disappear, and the QRS widens. In severe cases the QRS becomes so wide it blurs into a sinusoidal wave pattern, and then PEA or asystole follows. If you encounter a pulseless patient with wide, sluggish complexes and no obvious P waves, empiric treatment with calcium and other potassium-lowering strategies is reasonable even before lab results come back.

True PEA Versus Pseudo-PEA

Not all PEA is created equal. The term “pseudo-PEA” describes patients who have no palpable pulse but do have some degree of cardiac mechanical activity visible on bedside ultrasound.⁴ In other words, the heart is contracting, just not forcefully enough to generate a pulse you can feel. True PEA, by contrast, involves electrical activity with essentially no mechanical wall motion at all.

This distinction matters because pseudo-PEA patients have a much better chance of being resuscitated. Their hearts are still trying to work. The practical challenge is that the ECG alone cannot tell you which type you are dealing with. The tracing might look identical in both cases. You need an ultrasound probe on the chest to see whether the walls are moving. One small study of out-of-hospital cardiac arrest patients found that when PEA patients had stable end-tidal CO2 values during compression pauses and ultrasound confirmed cardiac wall motion, a modified treatment approach led to return of spontaneous circulation in nearly all of them, with half achieving a good neurological outcome.⁵ Those numbers come from a very small sample and should be interpreted cautiously, but they illustrate why distinguishing pseudo-PEA from true PEA is clinically meaningful.

Tools That Complement the ECG

The ECG tells you there is organized electrical activity. Whether that translates to any mechanical heart function, and what is causing the disconnect, requires additional bedside tools.

Point-of-Care Ultrasound

A focused cardiac ultrasound during a brief pause in chest compressions can reveal wall motion (pseudo-PEA versus true PEA), pericardial fluid suggesting tamponade, a massively dilated right ventricle suggesting pulmonary embolism, or an empty-looking left ventricle suggesting severe hypovolemia. A narrative review of the evidence found that point-of-care ultrasound during cardiac arrest can identify the cause in patients with nonshockable rhythms, assess compression quality, and help estimate prognosis.⁶ The key caveat is that ultrasound imaging must not interrupt chest compressions for more than a few seconds. Teams typically coordinate a brief pause at the pulse-check window, grab a subxiphoid or apical view, and resume compressions immediately.

End-Tidal CO2 Monitoring

Capnography, which measures exhaled carbon dioxide, provides real-time feedback during resuscitation. In PEA arrest specifically, rising end-tidal CO2 values are encouraging. A study of out-of-hospital PEA arrests found a positive linear relationship between the change in end-tidal CO2 over time and the likelihood of return of spontaneous circulation, with increases above 20 mmHg being highly specific for a successful outcome.⁷ Conversely, a systematic review found that very low initial end-tidal CO2 values (below about 10 mmHg) strongly predicted death, though the exact threshold was not perfectly consistent across all studies reviewed.⁸

The practical takeaway: if you are managing a PEA arrest and the capnography tracing is trending upward, keep going. The heart may be generating more forward flow than you realize, and you might be looking at pseudo-PEA heading toward recovery.

Common Pitfalls and Mimics

Identifying PEA requires confidence that what you are seeing on the monitor is real and that the patient is truly pulseless. Both assumptions can fail.

ECG artifacts from loose leads, patient movement, or external devices can mimic serious arrhythmias.⁹ During active resuscitation, chest compressions create rhythmic motion artifact that can obscure or simulate organized electrical activity. When compressions stop for a rhythm check, you may see a few seconds of artifact before the baseline settles. Reading the rhythm too quickly during this transition can lead to a mistaken call.

On the other side of the coin, true ventricular fibrillation can occasionally masquerade as asystole on a monitor, especially if the electrical axis of the fibrillation is perpendicular to the lead being displayed. A case report documented ventricular fibrillation identified by ultrasound in a patient whose ECG monitor showed what appeared to be a flat line.¹⁰ If you are calling a rhythm asystole or PEA and it does not fit the clinical picture, checking additional leads or grabbing an ultrasound can prevent missing a shockable rhythm.

Pulse detection itself is fallible, especially under stress. Studies of healthcare providers checking for a carotid pulse show that even experienced clinicians sometimes cannot reliably detect one within the recommended 10-second window. In a profoundly hypotensive patient with very weak cardiac output, a provider might miss the pulse entirely and treat the situation as PEA when the heart is actually generating some circulation. This is another reason bedside ultrasound and capnography are so valuable: they give you independent confirmation of what the heart is actually doing.

The Reversible Causes Framework

PEA accounts for up to about a quarter of sudden cardiac arrests, and managing it effectively depends almost entirely on finding and treating the underlying cause.¹¹ Unlike ventricular fibrillation, which has a specific definitive treatment (defibrillation), PEA has no single fix. The traditional mnemonic taught in resuscitation courses groups reversible causes into the “Hs and Ts”: hypovolemia, hypoxia, hydrogen ion (acidosis), hypo/hyperkalemia, hypothermia, tension pneumothorax, tamponade, toxins, thrombosis (pulmonary or coronary). The ECG pattern, combined with clinical context, narrows this list.

For example, a previously healthy young trauma patient in PEA arrest with narrow QRS complexes and a distended neck vein on one side likely has a tension pneumothorax or tamponade. A dialysis patient found down with wide, slow complexes almost certainly has hyperkalemia until proven otherwise. A postoperative patient who suddenly loses their pulse after complaining of chest pain and shortness of breath, with narrow QRS PEA and a dilated right ventricle on ultrasound, should trigger consideration of massive pulmonary embolism. The ECG pattern is one data point in a rapid bedside puzzle.

Why PEA Has Better Survival Than Asystole

Among the nonshockable arrest rhythms, PEA carries a meaningfully better prognosis than asystole. A meta-analysis found that PEA was about twice as survivable as asystole overall, with the advantage holding in both in-hospital and out-of-hospital settings. Neurological outcomes were also more favorable in PEA patients.¹² The proportion of cardiac arrests presenting as PEA has been increasing over time, possibly because earlier detection and improved pre-hospital care catch some patients before they deteriorate from PEA into asystole.¹³

When comparing PEA and asystole as initial in-hospital rhythms, PEA was strongly associated with a higher rate of return of spontaneous circulation in both unadjusted and adjusted analyses. The relationship with longer-term survival was more complex and depended on which confounders were accounted for.¹⁴ The general message, though, is that PEA is not a hopeless rhythm. It represents a heart that still has some electrical organization, and in many cases a reversible cause is driving the arrest.

Epinephrine Timing Matters

In PEA and other nonshockable rhythms, epinephrine is the primary pharmacological intervention. Timing appears to be significant. A study of out-of-hospital PEA arrests found that early epinephrine administration more than doubled the rate of return of spontaneous circulation compared to later dosing.¹⁵ A larger analysis showed that each minute of delay from EMS arrival to epinephrine was associated with a 4% decrease in odds of survival, and the majority of patients were not receiving the drug within the first 10 minutes.¹⁶

This is worth knowing because it affects system-level decisions: how quickly can paramedics establish IV access, how protocols are structured, and whether intraosseous access should be used early to avoid delays. For the individual clinician reading an ECG and managing PEA, the practical point is that once you have confirmed organized electrical activity without a pulse, epinephrine should go in as soon as vascular access allows. Do not wait for additional rhythm analysis or multiple compression cycles if access is already available.

PEA in Children and Adolescents

Pediatric PEA arrests share the same fundamental definition as adult PEA but differ in their causes and dynamics. Respiratory failure and sepsis are more common precipitants in children than primary cardiac disease, which means the ECG pattern often reflects a heart that was structurally normal before the arrest. A study of pediatric cardiac arrest found that PEA frequently transitioned to other rhythms during resuscitation: in 67 resuscitation episodes, there were 52 transitions from PEA to return of spontaneous circulation, 22 transitions from PEA to ventricular fibrillation or pulseless ventricular tachycardia, and 23 recurrences of PEA after initial return of pulses.¹⁷ The transitions from PEA to a shockable rhythm are particularly important to recognize, because they change management: a patient who started in PEA may need defibrillation minutes later.

The study also found that dynamic factors evolving during CPR, not just the initial rhythm, predicted whether PEA would transition to return of circulation. Compression depth beyond a certain threshold showed a near-significant effect. For clinicians managing pediatric PEA, this reinforces the importance of high-quality compressions and frequent rhythm reassessment, since the rhythm landscape can shift rapidly.

Can Automated Defibrillators Detect PEA?

Standard automated external defibrillators analyze the rhythm to determine whether a shock is advised. They will correctly identify PEA as a nonshockable rhythm in the sense that they will not deliver a shock. However, they do not typically distinguish PEA from asystole or tell the rescuer what kind of organized rhythm is present. More advanced circulation-detection algorithms have been developed that can differentiate between pulsatile and pulseless rhythms during CPR. One such algorithm achieved a sensitivity of about 98% for detecting pulsatile rhythms and a specificity of about 98% for identifying PEA.¹⁸

These algorithms are not yet standard in consumer or most professional defibrillators, but they represent a promising direction. If a device could reliably flag pseudo-PEA during resuscitation, it might prompt rescuers to consider specific interventions rather than continuing generic CPR. For now, though, identifying PEA and distinguishing its subtypes remains a human task requiring pulse checks, ultrasound, and capnography alongside the ECG.

How the Concept of PEA Has Shifted Over Time

PEA was not always called PEA. The older term was electromechanical dissociation, or EMD, which described organized electrical depolarization without mechanical contraction. Experimentally, EMD could be produced by inducing ventricular fibrillation, waiting a few minutes without CPR, and then delivering a defibrillating shock. The result was often restoration of electrical activity on the monitor, but because of diffuse ischemia in the heart muscle, no mechanical contraction followed.¹⁹

The shift to the term “pulseless electrical activity” reflected a recognition that the category is broader than true electromechanical dissociation. Many patients labeled PEA do have some cardiac mechanical activity; they are just not generating enough output for a palpable pulse. The terminology change was not cosmetic. It prompted clinicians to think of PEA as a spectrum rather than a single entity, which in turn supported the development of the narrow-versus-wide and true-versus-pseudo frameworks that now guide resuscitation. Understanding that PEA encompasses everything from a nearly normal heart in tamponade to a globally ischemic myocardium barely twitching changes how aggressively and specifically you search for a treatable cause.