Abstract Body: Introduction - Survival following out-of-hospital cardiac arrest (OHCA) is greatest in patients with appropriately defibrillated ventricular fibrillation (VF). Some VF may not be accurately identified by electrocardiography (ECG) alone. Our group and others have described echocardiographic (echo) VF in patients presenting to the Emergency Department (ED) following OHCA.
Research Question - We hypothesize survival following OHCA is no different for patients with echo VF compared to ECG VF.
Methods - We performed a prospective, observational, 27-site study of adult atraumatic OHCA. Patients were enrolled as a convenience sample with simultaneous ECG and echo time-stamped and digitally recorded. Experienced ED physicians and cardiologists independently reviewed ECG and echo images, blinded to patient and provider information, with adjudication by a third clinician when there was a disagreement. ECG were interpreted as PEA, asystole, VF, or ventricular tachycardia. Echo were interpreted as organized contractions, myocardial fibrillation, or cardiac standstill. Only ECG and echo from the initial three pauses in CPR are included in this analysis. Patients were followed to survival to hospital admission and survival to hospital discharge. Comparison between groups was performed using 95% confidence intervals (95%CI).
Results - A total of 914 OHCA patients were included in the analysis, with 21.1% of patients with ECG VF, and 9.4% with echo VF. There was no difference in survival to hospital discharge for patients with echo VF compared to ECG VF, 8.1% (4.0-15.9) vs 5.1% (2.7-9.3) respectively. Survival to hospital admission was greater for patients with echo VF compared to ECG VF, 33.7% (24.6-44.2) vs 17.6% (12.9-23.6) respectively. Occult VF, defined as echo VF with a non-shockable ECG, was identified in 44 of 914 patients (4.8%). There was no difference in survival for patients with occult VF compared to those with ECG VF, for survival to hospital admission, 27.3% (16.2-42.0) vs 17.0% (12.3-23.6) and survival to hospital discharge, 6.8% (2.3-18.2) vs 5.1% (2.7-9.3). Clinicians were no more likely to defibrillate ECG VF, 55.0% (47.9-61.9) compared to echo VF, 58.3% (47.6-68.3), but were less likely to defibrillate occult VF, 22.7% (12.8-37.0).
Conclusion - Patients demonstrate VF by both ECG and echo, with some patients demonstrating occult VF visualized only by echo. Survival to hospital discharge was no different for patients with ECG VF compared to echo VF.