Pulseless electrical activity, or PEA, is a type of cardiac arrest where the heart’s electrical system continues producing organized signals, but the heart muscle fails to pump blood. On a monitor, the heart rhythm may look relatively normal, yet the person has no pulse and no blood pressure. This disconnect between electrical activity and mechanical pumping makes PEA one of the most dangerous cardiac emergencies, with only about 6% of patients surviving to hospital discharge.
How PEA Differs From Other Cardiac Arrests
Most people picture cardiac arrest as the heart going into a chaotic, quivering rhythm. That’s ventricular fibrillation, and it responds to defibrillation (the electric shock from paddles or an AED). PEA is fundamentally different. The electrical signals traveling through the heart are organized, sometimes even appearing as a normal-looking rhythm on a heart monitor. The problem isn’t electrical chaos. It’s that the heart muscle either can’t contract or is contracting too weakly to generate any meaningful blood flow.
This is why a defibrillator won’t help during PEA. A shock is designed to reset a disorganized electrical rhythm, but in PEA the electricity is already organized. There’s nothing to “reset.” The real problem lies somewhere else in the body, and finding that underlying cause is the key to treatment.
What Happens Inside the Body
The heart’s electrical system fires normally, sending signals that tell the muscle cells to contract. But something prevents those signals from producing effective pumping. The most common underlying mechanism is widespread lack of blood flow to the heart muscle itself. When the heart is starved of oxygen, the muscle becomes too weak to respond to its own electrical commands.
Three other distinct patterns can cause PEA. The heart may have too little blood to pump, as happens during massive bleeding or when fluid compresses the heart from outside (cardiac tamponade). The heart may face an overwhelming blockage it can’t push against, like a massive blood clot in the lungs. Or the heart muscle may simply be in the final stages of failure, too damaged or exhausted to contract.
The Electrical Patterns on a Monitor
PEA doesn’t produce a single, recognizable rhythm. It can show up as a slow heart rhythm, a rhythm with wide or narrow electrical waves, or even something that looks close to a normal heartbeat. The variety of possible patterns is part of what makes PEA tricky to recognize. Medical teams identify it not by the rhythm on the screen, but by the combination of organized electrical activity and the absence of a pulse.
The shape of the electrical waves does carry prognostic information. Wider, more abnormal-looking waves (particularly QRS complexes wider than 0.2 seconds) are associated with worse outcomes. Narrower, more normal-looking patterns suggest the heart muscle may still have some recoverable function.
True PEA vs. Pseudo-PEA
Not every case of PEA is identical. When an ultrasound probe is placed on the chest during resuscitation, some patients show absolutely no heart wall movement. This is true PEA: the muscle isn’t responding at all. Other patients show visible cardiac contractions on ultrasound, just not strong enough to produce a detectable pulse. This is called pseudo-PEA, and it represents a low-flow state rather than a completely silent heart.
The distinction matters because pseudo-PEA patients have residual heart function that may respond to treatment more readily. Bedside ultrasound during cardiac arrest has become an increasingly important tool for making this distinction in real time.
The 5 H’s and 5 T’s: Reversible Causes
Emergency teams use a memorized checklist of ten reversible causes, grouped as the “5 H’s and 5 T’s,” to rapidly identify why the heart stopped pumping. The entire treatment strategy for PEA revolves around finding and fixing one of these causes.
- Hypovolemia: severe blood or fluid loss, leaving the heart with nothing to pump
- Hypoxia: dangerously low oxygen levels
- Hydrogen ion (acidosis): the blood becomes too acidic for the heart to function
- Hypothermia: critically low body temperature
- Hypo- or hyperkalemia: potassium levels too low or too high, disrupting heart muscle contraction
- Tension pneumothorax: air trapped in the chest cavity compressing the heart
- Tamponade (cardiac): fluid around the heart preventing it from filling
- Toxins: drug overdoses or poisoning
- Thrombosis, pulmonary: a massive blood clot blocking the lungs
- Thrombosis, coronary: a heart attack blocking blood flow to the heart muscle
Physical examination during resuscitation provides critical clues. If PEA occurs after trauma, hemorrhage, tension pneumothorax, and cardiac tamponade jump to the top of the list. Absent breath sounds on one side of the chest point toward a collapsed lung. Normal breath sounds with distended neck veins suggest fluid is compressing the heart.
How PEA Is Treated
CPR begins immediately. Because defibrillation doesn’t work for PEA, the treatment pathway focuses on two things simultaneously: maintaining blood flow through chest compressions and identifying the reversible cause.
Epinephrine is given as soon as possible, then repeated every 3 to 5 minutes. This powerful stimulant constricts blood vessels and strengthens whatever cardiac contractions remain, buying time while the team searches for the underlying problem. Advanced airway management and continuous monitoring of exhaled carbon dioxide help assess whether CPR is generating meaningful circulation.
The critical step is treating the cause. If the problem is massive blood loss, the patient needs fluid and blood products. If a tension pneumothorax is compressing the heart, a needle or tube inserted into the chest can release the trapped air within seconds. If a pulmonary embolism is suspected, clot-dissolving medications may be considered. Without identifying and correcting the trigger, CPR and epinephrine alone are unlikely to restore a pulse.
Survival and Prognosis
PEA carries significantly worse outcomes than cardiac arrests caused by shockable rhythms. Patients who arrest in ventricular fibrillation or ventricular tachycardia survive to hospital discharge 20% to 30% of the time. For PEA, that number drops to roughly 6%.
Survival depends heavily on how quickly the underlying cause is identified and whether it’s correctable. A tension pneumothorax relieved within minutes, for example, can lead to rapid recovery. A massive heart attack with extensive muscle damage offers far less room for intervention. The electrical pattern on the monitor also offers clues: patients whose rhythm looks closer to normal have better odds than those with wide, sluggish electrical activity.
Pseudo-PEA, where ultrasound reveals the heart is still attempting to contract, generally carries a better prognosis than true PEA. This is one reason point-of-care ultrasound has become a standard part of cardiac arrest management, helping teams quickly gauge whether the heart has recoverable function and guiding decisions about how aggressively to pursue specific interventions.