Abstract 316: Cardiac Arrest Rhythm Transitions in Drug Overdose-Related Resuscitation

Abstract

Introduction: The prehospital electrocardiogram (ECG) may inform treatment of out-of-hospital cardiac arrest (OHCA) patients regardless of etiology. While drug overdose (OD)-OHCA is increasingly common, little is known about the characteristics and utility of the intra-resuscitation OD-OHCA ECG signal. In this study, we sought to investigate the evolving ECG rhythm state of OD-OHCA patients to identify potentially informative patterns or phenomena. Methods: Case data, including electronic defibrillator files, for emergency medical services treated OD-OHCA were obtained from the Resuscitation Outcomes Consortium, a multi-site clinical research network in the US and Canada. OD-OHCA case status was previously established by site-level data abstractors reviewing prehospital and in-hospital electronic medical records for evidence of drug involvement. Continuous ECG traces were extracted and chest compression-free ECG segments were parsed with custom MATLAB (vR2017a) software. Each ECG segment was manually rhythm-classified by a research specialist. Rhythm transitions were identified as changes in rhythm between sequential analyzable rhythm segments. Transitions were tabulated and summarized by their rhythms and timing. Results: Complete prehospital ECG data were available for 130 patients, comprising 1,112 ECG segments of which 771 (69.3%) were analyzable. The mean (SD) age was 33.6 (11.3) years and 68.3% were male. The most commonly observed rhythm at the segment level was low amplitude (“fine”) ventricular fibrillation (VF), accounting for 44.1% of all segments, although at the case level asystole was the most common rhythm, present in 47.7% of all cases. We recorded 292 rhythm transitions, with a mean (SD) 2.5 (1.5) transitions per case. Mean (SD) time to first transition was 11.1 (6.9) minutes and mean (SD) time to last transition was 19.8(8.8) minutes. The most frequently observed transition was from asystole to low amplitude ventricular fibrillation (17.1%). Conclusions: The OD-OHCA ECG is varied and dynamic, presenting in numerous rhythms and transitioning between rhythms throughout the course of resuscitation.