Performance of a high-sensitivity troponin-based early rule-out pathway for suspected myocardial infarction

INTRODUCTION: High-sensitivity cardiac troponins enable early rule-out of myocardial infarction (MI), but their effect on diagnostic specificity remains uncertain. We evaluated rates of type I MI and obstructive coronary artery disease (CAD) among patients triaged using the Suspected Acute Myocardial Infarction in Emergency (SAMIE) pathway. METHODS: A retrospective cohort study was conducted on patients presenting with chest pain to an Australian Health Service Emergency Department between February 2023 and December 2024. Patients were classified as low-risk (troponin <5 ng/L), intermediate-risk (troponin ≥5 ng/L and Δ troponin <3 ng/L), or high-risk (troponin ≥5 ng/L and Δ troponin ≥3 ng/L or above sex-specific thresholds). All patients underwent expedited outpatient review through a rapid-access cardiac clinic. The primary outcome was type I MI within 30 days. Secondary outcomes included positive stress echocardiography and obstructive CAD on invasive coronary angiography. RESULTS: Among 355 patients (mean age 59.4 ± 17.5 years), 64 (18.0%) were low-risk, 121 (34.1%) intermediate-risk, and 170 (47.9%) high-risk. The 30-day type I MI rate was 0.6% (two events), both occurring in the SAMIE high-risk group. Rates of obstructive CAD and positive stress echocardiography were similar across risk categories. CONCLUSIONS: Among a selected cohort managed through a structured rapid-access chest pain outpatient service, 30-day type I MI rates were low across all SAMIE risk categories. Both events occurred in the SAMIE high-risk group. Given the small number of events, these findings should be considered hypothesis-generating and require validation in larger prospective studies.