## PEA vs. Ventricular Fibrillation: The Critical Distinction ### ECG Morphology as the Key Discriminator **Key Point:** The defining difference between PEA and VF lies in the **electrocardiographic pattern**, not the clinical outcome (both are pulseless and require CPR). | Feature | PEA | VF | |---------|-----|----| | **ECG pattern** | Organized QRS complexes, P waves, or both | Chaotic, coarse or fine fibrillatory waves | | **Electrical organization** | Present | Absent | | **Mechanical output** | None (dissociation) | None | | **Pulse** | Absent | Absent | | **Shockability** | Non-shockable | Shockable | ### Why This Matters for Management **High-Yield:** VF is the **only non-shockable rhythm that becomes shockable** if defibrillation is attempted early. PEA, by contrast, is **never shockable** and requires continuous CPR plus epinephrine and investigation of reversible causes. **Clinical Pearl:** In this case, the organized electrical activity (QRS complexes visible at 80 bpm) with absent pulse = **PEA**. If the monitor showed coarse or fine fibrillatory waves instead, it would be VF, and defibrillation would be indicated. **Mnemonic:** **ACLS Shockable Rhythms** = VF and pulseless VT. **Non-shockable** = Asystole and PEA. The **presence of organized electrical activity** separates PEA from asystole; the **absence of fibrillatory waves** separates PEA from VF. ### Clinical Algorithm ```mermaid flowchart TD A[Cardiac arrest - Check monitor]:::outcome A --> B{What do you see?}:::decision B -->|Coarse/fine fibrillatory waves| C[VF]:::outcome B -->|Organized QRS, P waves| D[PEA or organized rhythm]:::outcome B -->|Flat line| E[Asystole]:::outcome C --> F[Defibrillate + CPR + Epi]:::action D --> G[CPR + Epi + Search reversibles]:::action E --> H[CPR + Epi + Search reversibles]:::action ``` [cite:AHA ACLS Guidelines 2020]
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