• Lisa Brichko, Hans G Schneider, William Chan, Jarrel Seah, Smit De Villiers V Emergency and Trauma Centre, The Alfred Hospital, Melbourne, Victoria, Australia. Nat, Anthony Dart, Jeremy P Stevens, and Biswadev Mitra.
• Emergency and Trauma Centre, The Alfred Hospital, Melbourne, Victoria, Australia.
• Emerg Med Australas. 2018 Aug 1; 30 (4): 486-493.

ObjectiveTo determine variables that could facilitate safe discharge from the ED following a single high-sensitivity troponin I (HsTnI) result to exclude acute myocardial infarction (AMI).MethodsA retrospective cohort study was performed at a tertiary hospital of all patients that had serial HsTnI performed within 12 h of arrival to the ED over a 3 year period. The primary exposure variable of interest was a very low troponin initial result (HsTnI <5 ng/L). Medical record review and risk stratification score calculations were undertaken for all patients with the exposure variable of interest and an abnormal second troponin measurement (HsTnI ≥16 ng/L in women and HsTnI ≥26 ng/L in men).ResultsThere were 11 970 patients who presented between 1 July 2013 and 30 June 2016 that had serial HsTnI measurements performed. Of these, 4172 (34.9%) patients had an initial HsTnI measurement <5 ng/L. Of the patients with an initial HsTnI <5 ng/L that met inclusion criteria, 56 (1.3%) had a second troponin result above the 99th percentile and 32 (0.8%) cases of non-ST elevation myocardial infarction were diagnosed as well as 15 (0.4%) cases of ST elevation myocardial infarction. There were 44 (93.6%) of all AMI cases that met criteria for high-risk presentations under the National Heart Foundation of Australia guidelines. The negative predictive value of an initial HsTnI <5 ng/L to exclude AMI was 98.9% (95% confidence interval 98.5-99.1).ConclusionsThis supports the utilisation of a rapid rule out strategy to exclude AMI for patients that have an initial HsTnI measurement <5 ng/L in conjunction with a robust risk assessment.© 2017 Australasian College for Emergency Medicine and Australasian Society for Emergency Medicine.

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