Indeterminate zone high-sensitivity troponin levels in a rapid acute myocardial infarction assessment algorithm and patient dispositions
Nowak RM, Peacock F, Jacobsen G, Limkakeng AT, Christenson R, Singer AJ, McCord J, Apple FS, and DeFilippi C. Indeterminate zone high-sensitivity troponin levels in a rapid acute myocardial infarction assessment algorithm and patient dispositions. Academic Emergency Medicine 2021; 28(SUPPL 1):S206.
Academic emergency medicine
Background and Objectives: The multicenter High Sensitivity Cardiac Troponin I (hs-cTnI) in the United States (HIGH-US) study reported a 1-hour Emergency Department (ED) hs-cTnI algorithm for the assessment of acute myocardial infarction (AMI). However, 783 (37.1%) patients were placed in the algorithm's indeterminate zone, not meeting the rule-out or rule-in criteria. Our objectives were to describe the AMI and 30-day AMI/death rates and clinical characteristics of these patients placed in observation/inpatient beds (OBS/ADM) compared to having an ED discharge (EDD).
Methods: In this prospective cohort study 2113 consenting adults with any symptoms suspicious for AMI were enrolled from 2015-2016 in 29 US medical centers. There were no patient exclusion criteria. Baseline and 1-hour plasma samples were analyzed using the Siemens Atellica hs-cTnI assay (99th % = 47.0 ng/L), with results not available to the treating physician. AMI diagnosis was independently adjudicated using local contemporary troponin assays and all 30-day clinical data available. Patients were placed in OBS/ADM or had EDD according to each site's clinical practice. Stepwise logistic regression modeling was used to determine which of 25 clinical patient characteristics were associated with OBS/ADM disposition decisions.
Results: Of 763 (30.3%) of the intermediate zone placed patients with complete data available, 532 (69.7 %) were placed in OBS/ ADM and 231 (30.3%) had an EDD. Adjudicated AMI rates and 30-day AMI/death rates were different in these 2 groups (41 [7.7%], 2 [0.9%], p = 0.001 and 15 [2.8%], 1 [0.4%] respectively, p = 0.050). The clinical variables associated with OBS/ADM placement were age, hypertension, eGFR < 60, abnormal ECG, and previous revascularization (odds ratio estimates of 1.027, 1.764, 1.955, 1.700 and 1.620 respectively). The OBS/ADM to EDD ratios varied widely amongst the participating centers (100.0-50.0%).
Conclusion: The correct disposition decision for patients not ruling out or ruling in for AMI using a 1-hour hs-cTnI algorithm remains unclear. ED physicians, using contemporary troponin assays and clinical evaluations for 231 patients with EDD but who were placed in the hs-cTnI algorithm intermediate zone, missed 1 (0.4%) AMI, with 15 (2.8%) patients having 30-day AMI/death. The absence of our reported cardiac risk factors likely contributed to the EDD decision. Further studies are needed to validate our results.