When a patient goes into cardiac arrest, nurses must know exactly what they see on the monitor — and what it really means. Two of the most confusing heart rhythms during a code are PEA (Pulseless Electrical Activity) and Asystole.
They both mean no pulse, but only one shows electrical activity on the monitor. Let’s break down what makes them different, why it matters, and exactly what to do when you see each one.
❤️ What is PEA?
PEA means the heart’s electrical system is firing, but the heart muscle is not responding with a squeeze strong enough to create a pulse. So, there’s an EKG tracing, but no circulation.
👉 Key point: PEA is NOT a single rhythm — it’s a condition. You can see normal sinus rhythm, slow bradycardia, or any organized rhythm, but there’s no heartbeat strong enough to pump blood.
🔍 How PEA Looks on an EKG
- Any organized rhythm (can be normal, brady, or tachy).
- P waves and QRS may look normal.
- No pulse when you check the patient!
🔬 What Causes PEA?
PEA happens when there’s a mismatch: the heart’s electrical system works, but something blocks or weakens the muscle’s ability to pump.
Common causes are:
- Severe hypovolemia (low blood volume)
- Massive PE (pulmonary embolism)
- Cardiac tamponade (fluid compressing the heart)
- Tension pneumothorax
- Severe hypoxia
- Electrolyte imbalances (like extreme hyperkalemia)
- Acidosis
- Drug overdose
👉 Nurses learn these using the 5 H’s and 5 T’s:
- H’s: Hypovolemia, Hypoxia, Hydrogen ions (acidosis), Hypo/hyperkalemia, Hypothermia
- T’s: Tension pneumothorax, Tamponade, Toxins, Thrombosis (MI or PE), Trauma
❤️ What is Asystole?
Asystole means there is no electrical activity at all — the heart is electrically and mechanically silent. It is literally “flatline.”
👉 Key point: Asystole means the heart’s pacemaker cells have stopped working. There’s no impulse and no contraction.
🔍 How Asystole Looks on an EKG
- A flat, straight line.
- No P waves, no QRS, no electrical spikes.
- Always double-check: a loose lead can look like asystole!
🔬 What Causes Asystole?
Asystole usually means the patient’s heart muscle or electrical system has completely failed.
Common causes include:
- Prolonged cardiac arrest
- Untreated V-Fib or PEA
- Massive MI
- End-stage heart failure
- Severe trauma
- Terminal illness
💡 How to Tell the Difference: PEA vs. Asystole
| Feature | PEA | Asystole |
|---|---|---|
| EKG | Organized rhythm | Flat line |
| Pulse | None | None |
| Electrical Activity | Yes | No |
| Treatable Causes | Usually yes | Rare at end stage |
| Defibrillation? | No | No |
🩺 What Should Nurses Do for PEA?
Step 1: Check responsiveness and pulse. Confirm it’s truly pulseless.
Step 2: Call a Code Blue immediately.
Step 3: Start high-quality CPR right away.
Step 4: DO NOT shock PEA — it’s not a shockable rhythm.
Step 5: Give epinephrine every 3–5 minutes per ACLS.
Step 6: Find and treat the underlying cause (5 H’s and 5 T’s). This is the real fix for PEA.
Nurse’s Role:
- Run the code with the team.
- Draw labs quickly.
- Give IV fluids if hypovolemia is suspected.
- Prepare for possible needle decompression if tension pneumothorax is suspected.
- Support the team with medications and airway management.
🩺 What Should Nurses Do for Asystole?
Step 1: Check leads and connections — be 100% sure it’s real asystole.
Step 2: If confirmed and pulseless, call a Code Blue.
Step 3: Start high-quality CPR immediately.
Step 4: Give epinephrine every 3–5 minutes.
Step 5: Do NOT defibrillate — shocking a flatline won’t restart the heart.
Nurse’s Role:
- Provide compressions or manage the airway.
- Prepare meds on time.
- Document everything.
- Communicate with the code team.
👉 Important: Asystole usually has a very poor outcome, but high-quality CPR and addressing reversible causes gives the best chance.
🔑 Key Differences in Treatment
| Action | PEA | Asystole |
|---|---|---|
| Defibrillate? | ❌ No | ❌ No |
| CPR? | ✅ Yes | ✅ Yes |
| Epinephrine? | ✅ Yes | ✅ Yes |
| Find Cause? | ✅ Yes | ✅ Yes |
| Best chance? | Fix cause | Fix cause |
💬 Why Understanding PEA vs. Asystole Matters
Nurses are often first to recognize these rhythms. Mistaking PEA for a shockable rhythm can waste time. Missing PEA’s cause can cost a life.
👉 Remember:
- PEA = treat the cause.
- Asystole = keep CPR going, give epi, and confirm flatline.
This is why your quick assessment and teamwork in a code can change everything.
✅ Nursing Cheat Sheet
| Rhythm | EKG | Pulse | Shock? | Main Action |
|---|---|---|---|---|
| PEA | Organized rhythm | None | ❌ | CPR, epi, fix cause |
| Asystole | Flatline | None | ❌ | CPR, epi, confirm flatline |
🗝️ Conclusion
PEA and Asystole both mean cardiac arrest, but only PEA shows an organized rhythm on the monitor. Neither should be shocked. Both need fast CPR, epinephrine, and a search for what went wrong.
For nurses, knowing the difference saves time — and lives. Keep practicing your code skills and always stay calm under pressure. Your quick action can give your patient the best chance possible.