Derivation and Validation of a Novel 3-Hour Pathway for the Observe-Zone of the ESC 0/1H-Algorithm

Abstract Background The latest non-ST elevation myocardial infarction (NSTEMI) guidelines from the European Society of Cardiology (ESC) recommend a 3h cardiac troponin determination in patients triaged to the observe-zone of the ESC 0/1h-algorithm; however, no specific cut-off for further triage is endorsed. Purpose To derive and internally, as well as externally, validate a novel 3-hour pathway for the observe-zone of the ESC 0/1h-algorithm. Methods In an ongoing multicentre international diagnostic study, we prospectively enrolled unselected patients presenting to the emergency department with symptoms suggestive of myocardial infarction (MI). Final diagnoses were centrally adjudicated by two independent cardiologists applying the 4th universal definition of MI, based on complete cardiac work-up including cardiac imaging, serial high sensitivity cardiac troponin T (hs-cTnT) sampling and 90-day follow-up information. High sensitivity-cTnT concentrations were measured at presentation and after 1 and 3 hours. The primary outcome was safety, quantified by the sensitivity and NPV for early rule out of NSTEMI. External validation was performed in an independent multicentre international study. Results Among 2076 eligible patients, application of the ESC 0/1h-algorithm triaged 1512 patients (72.8%) to either rule-out or rule-in of NSTEMI, remaining 564 patients (27.2%) in the observe-zone (adjudicated NSTEMI prevalence 120/564 patients, 21.3%). The novel derived 3h-pathway for the observe-zone patients ruled-out NSTEMI with a 3h hs-cTnT concentration <15 ng/L and a 0/3h-hs-cTnT absolute change <4 ng/L, triaging 138 patients (25%) towards rule-out, resulting in a sensitivity of 99.2% (95% CI 96.0–99.9) and a NPV of 99.3% (95% CI 95.4–99.9). A 0/3h-hs-cTnT absolute change ≥6 ng/L ruled-in 63 patients (11.2%), resulting in a specificity of 98% (95% CI 96.2–98.9) and a PPV of 85.7% (95% CI75.0–92.3). The novel 3h-pathway reduced the number of patients in the observe zone by 36%, and the number of T1MI by 50% (Figure 1). Findings were confirmed in both internal and external validation. Conclusions A novel derived pathway combining a 3h hs-cTnT concentration <15 ng/L and a 0/3h absolute change <4 ng/L allowed to very safely rule-out NSTEMI in patients remaining in the observe-zone of the ESC 0/1h-algorithm. Funding Acknowledgement Type of funding sources: Public grant(s) – National budget only. Main funding source(s): The Swiss Heart FoundationThe Swiss National Science Foundation Figure 1