Contributor: Aaron Lessen, MD
Educational Pearls:
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Big question in cardiac arrest: is the rhythm shockable?
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Shockable: ventricular fibrillation (VF) and pulseless ventricular tachycardia
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Non-shockable: asystole and pulseless electrical activity (PEA)
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Rhythm classification is typically based on ECG, but echocardiography can directly visualize myocardial fibrillation
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Occult VF: a rhythm that appears non-shockable on ECG but demonstrates VF on echocardiography
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A 2025 multicenter prospective study looked at 811 patients with out-of-hospital cardiac arrest
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5.3% had occult VF detected by echocardiography
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Of the patients with occult VF:
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81.4% had PEA on ECG
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18.6% had asystole on ECG
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Patients with occult VF were less likely to receive defibrillation because their ECG suggested a nonshockable rhythm
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Clinical takeaway: echocardiography during cardiac arrest may reveal a potentially shockable rhythm hiding behind an apparently nonshockable ECG
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This identifies a subset of cardiac arrest patients who would otherwise be managed as PEA or asystole based on ECG
References
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Gaspari R, Adhikari S, Gleeson T, Kapoor M, Lindsay R, Noble V, Nomura JT, Weekes A, Theodoro D. Occult Ventricular Fibrillation Visualized by Echocardiogram During Cardiac Arrest: A Retrospective Observational Study From the Real-Time Evaluation and Assessment for Sonography-Outcomes Network (REASON). J Am Coll Emerg Physicians Open. 2025 Jan 13;6(1):100028. doi: 10.1016/j.acepjo.2024.100028. PMID: 40012664; PMCID: PMC11853361.
Summarized by Meg Joyce, MS3 | Edited by Meg Joyce & Ahmed Abdel-Hafiz, NREMT-P
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