Characterization of the observe zone of the ESC 2015 high-sensitivity cardiac troponin 0 h/1 h-algorithm for the early diagnosis of acute myocardial infarction

Objective: The novel high-sensitivity cardiac troponin (hs-cTn) 0 h/1 h-algorithm substantially improves the early triage of patient's assigned rule-out or rule-in of acute myocardial infarction (AMI), while diagnostic uncertainty remains in that 25-30% of patients assigned to observe. We aimed to better characterize these patients. Methods: In a prospective multicenter diagnostic study, we applied the hs-cTnT 0 h/1 h-algorithmin 2213 unselected patients presenting with symptoms suggestive of AMI to the emergency department. The final diagnosis was adjudicated by two independent cardiologists using all available information. Survival at 720-days was the prognostic endpoint. Findings were validated using a hs-cTnI 0 h/1 h-algorithm. Results: Twenty-four percent (n = 523) of patientswere assigned to observe by the hs-cTnT 0 h/1 h-algorithm. These patients differed significantly in multiple characteristics from rule-out and rule-in patients: they were older, in 75% male, and very often (57%) had pre-existing coronary artery disease (CAD). Diagnostic uncertainty for the presence of an AMI/UA was high. Only 39% of patients were suitable for coronary computed tomography angiography (CCTA). The most common final adjudicated diagnoses were non-cardiac disease (38%), noncoronary cardiac disease (24%), unstable angina (UA, 21%), and AMI (15%). Absolute hs-cTnT-changes within 3 h had the highest diagnostic accuracy for AMI (AUC 0.86). Cumulative 720-day survival rate was 86%, which was significantly lower as compared to rule-out (p < 0.001) and comparable to rule-in (p = ns). Findings were similar for the hs-cTnI observe zone. Conclusion: Observe patients are typically elderly men with pre-existing CAD and high long-term mortality. Absolute hs-cTn-changes within 3 h, functional stress imaging and coronary angiography are the key diagnostic modalities. (C) 2016 Elsevier Ireland Ltd. All rights reserved.