Abstract 221: Heart Rhythm Analysis During Chest Compressions in Case of Out-of-Hospital Cardiac Arrest: Are Confirmation Analysis a Safety Issue?

Purpose: During out-of-hospital cardiac arrest (OHCA), automated external defibrillators (AEDs) can analyze the patient's cardiac rhythm using a Shock Advisory System (SAS) that runs during chest compressions (CC). We aimed to evaluate the safety of a SAS that enables analysis during CC, referred to as Analyze Whilst Compressing (AWC). AWC classifies the cardiac rhythm as shockable (Sh) or non-shockable (NSh) in the presence of CC. If shockable, the rescuer backs off while the AED confirms the rhythm in the absence of CC with a confirmation analysis (CoA). We aimed to verify the safety of AWC when patients present NSh rhythm during CC.

Method: In this retrospective study, we utilized data from the Paris Fire Brigade collected between 01/01/2021 and 31/01/2022. The inclusion criteria were adult OHCA patients with initial Ventricular Fibrillation analyzed by the AWC algorithm. We analyzed patients' safety by assessing false positive cases in the presence of chest compressions: ill-advised CoA compared to appropriate CoA within the first 10 minutes of intervention. The main outcome was the rate of patients presenting ill-advised CoA.

Results: We analyzed 285 consecutive OHCA patients, corresponding to 2011 rhythm analyses ; 205 patients had at least 1 CoA, which led to a confirmation rate of 27.7% over 557 analyses; 175 patients had at least one appropriate CoA; 76 patients (26.6%) had at least one ill-advised CoA: 48 (16.8%) had one ill-advised CoA, 19 (6.7%) had two ill-advised CoA, six patients (2.1%) had three ill-advised CoA, two patients (0.7%) had four ill-advised CoA, and one (0.35%) had six ill-advised CoA. The global amount of ill-advised CoA was 118, which leads to an ill-advised confirmation rate of 5.9%. The rhythm distribution implied with ill-advised CoA was: 72 (61%) asystole, 45 (38%) other non-shockable, one (0.85%) transition from Sh to NSh. The hands-off time that each ill-advised CoA generated was 10 [8-18] (median [IQR]) seconds.

Conclusion: AWC presents comparable results to other methods of analysis during chest compressions in detecting some non-shockable rhythms as false positives. In a majority of patients, CoA was appropriate. Only one patient (0.35%) had up to six ill-advised CoA, making his impact negligible over the cohort.