UMEM Educational Pearls

Title: How much ventricular fibrillation are we missing?

Keywords: OCHA, VF, ventricular fibrillation, cardiac arrest, shockable, Occult VF (PubMed Search)

Posted: 1/28/2026 by Kami Windsor, MD
Click here to contact Kami Windsor, MD

A crucial part of cardiac arrest management is identification of the underlying rhythm, with key aspects of management diverging depending whether shockable (pulseless ventricular tachycardia/pVT or ventricular fibrillation/VF) or unshockable (pulseless electrical activity/PEA or asystole).

A recent study prospectively evaluated adult atraumatic out-of-hospital-cardiac-arrests (OHCAs) presenting to the ED, to determine what percentage of cases had “Occult VF” – VF found point-of-care echocardiogram but not by ECG. The researchers only included cases with simultaneous ECG and echo assessments for the initial 3 pulse checks. Echo and ECG determinations for the study were adjudicated by research team members.

They found that:

5.3% of patients had occult VF (43/811), with ECG reading PEA in 81.4% (35/43) and asystole in 18.6% (8/43)
Of the 202/811 patients with VF on ECG, only 23.3% had echo VF
Interestingly, patients with ECG VF but no VF on echo had a lower rate of ROSC and successful defibrillation than those with Occult VF
There was no statistically significant difference in survival to hospital discharge between the two
A higher percentage of patients evaluated by TEE compared to TTE were found to have occult VF (12.5% vs 4.9%)

Major limitations:

Only have the cases with simultaneous ECG + echo for the first 3 pauses
Only have the recorded echo clips, which are not the same as in-the-moment viewing during the arrests
No comparison to how research team interpreted ECGs to how the treating team managed

Bottom Line: Point-of-care echocardiogram continues to have value in the management of cardiac arrest, potentially changing management and affecting post-ROSC decisions. Ensuring high-quality CPR, with appropriate defibrillation and anti-arrhythmic strategies, remains paramount in management of shockable OHCA.

References

Gaspari R, Adhikari S, Gleeson T, et al. 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;6(1):100028. doi: 10.1016/j.acepjo.2024.100028.