Occult Ventricular Fibrillation Visualized by Echocardiogram During Cardiac Arrest: A Retrospective Observational...

Cardiac arrest patients with a shockable rhythm are more likely to survive an out-of-hospital cardiac arrest (OHCA) compared with a nonshockable rhythm. An electrocardiogram (ECG) is the most common way to identify a shockable rhythm, but it can miss patients with clinically significant ventricular fibrillation (vfib). We sought to determine the percentage of nonshockable OHCA patients that demonstrated vfib on echo.

Secondary analysis of echo images recorded from a prior study from our group, Real-Time Evaluation and Assessment for Sonography-Outcomes Network (REASON), a multicenter, observational study of OHCA patients presenting to the emergency department with nonshockable rhythms. Using ECG and echocardiogram images recorded during the initial cardiopulmonary resuscitation (CPR) pause, 2 independent emergency physicians determined the presence of vfib. Two experienced emergency physicians (R.G. and T.G.) reviewed echo images with adjudication by a third if necessary. ECG interpretation was unblinded to patient information. The primary outcome was the proportion of patients in occult vfib.

During the first CPR pause, reviewers noted occult vfib in 22/685 (3.2%; 95% CI, 2.1%-4.8%) subjects. Patients with ECG vfib (n = 55) were defibrillated immediately during the first pause in CPR, but no patients with occult vfib during the first pause in CPR were defibrillated. Subsequently, 50% (11 of 22) of occult vfib patients were defibrillated when ECG vfib was recognized during an ensuing pause in CPR.

One in 33 OHCAs with a nonshockable ECG rhythm exhibits VF on echocardiogram. Patients presenting to the emergency department in a presumed nonshockable rhythm following OHCA may benefit from prompt defibrillation if personnel recognize occult vfib on echo.