Abstract 15825: Inter-reader Concordance and Variations in Interpretation of Post Resuscitation ECG in Abnormal vs Normal Metabolic Milieus Following Out-of-hospital Cardiac Arrest

Abstract

Background: Among survivors of out of hospital cardiac arrest (OHCA), the post resuscitation 12-lead electrocardiogram (ECG) is a widely used tool to identify acute thrombotic coronary occlusion (ACTO) and for appropriate triage to the catheterization laboratory. It is unknown how a post-resuscitation abnormal metabolic milieu impacts ECG accuracy. We studied inter-reader concordance in ECG interpretation as well as same-patient variation in interpretation between abnormal (A) and normal (N) metabolic milieus (MM). Methods: We performed a retrospective analysis of 125 consecutive patients with OHCA with a shockable rhythm undergoing coronary angiography in a single institution. Patients with AMM were defined as pH <7.1, K <2.8 or >6 mEq/L, vasoactive drug use or lactate >2 ng/ml. All post resuscitation ECGs recorded in both AMM and NMM for each patient prior to any invasive intervention were blindly interpreted by 2 experienced readers, classified into two categories: diagnostic for ATCO (ATCO +) and not diagnostic for ATCO (ATCO -) and compared to angiographic ATCO. The Cohen’s kappa scale was used to measure concordance. Results: Concordance between readers was 0.69 (95% CI 0.56-0.84) in AMM and 0.82 (95% CI 0.64-0.99) in NMM. Of 35 ECGs interpreted as diagnostic for ATCO (+) in AMM, 27 (77%) were reclassified as ATCO (-) after metabolic correction. Among 90 ECGs initially diagnosed as ATCO (-) in AMM, 2 (2%) were reclassified as ATCO (+) whereas 88 (98%) remained as ATCO (-) in NMM. Most ATCO (-) ECGs were in the setting of angiographic ATCO; see table. Conclusions: Despite acceptable inter-reader concordance (moderate in AMM, high in NMM) between experienced ECG readers, a significant proportion of angiographic ATCO was missed on post resuscitation ECGs. A high percentage of patients with angiographic ATCO were reclassified on ECG from ATCO (+) in AMM to ATCO (-) in NMM, suggesting possible interim blunting/resolution of typical diagnostic ECG changes in NMM.