Implementing an early rule-out pathway for acute myocardial infarction in clinical practice

### Learning objectives Chest pain is a common presentation to the emergency department and can be caused by a range of conditions including acute myocardial infarction. However, only 1 in 10 patients with symptoms suggestive of acute coronary syndrome are ultimately diagnosed with myocardial infarction.1 As such, effective pathways are required to enable the prompt and safe rule-out of the majority of patients with non-cardiac presentations and the rapid identification of those with myocardial infarction. Recently published guidelines from the National Institute for Health and Care Excellence (NICE) and the European Society of Cardiology (ESC) have recommended the use of early rule-out pathways for myocardial infarction,2 3 enabled by the increased analytical precision of high-sensitivity cardiac troponin (hs-cTn) testing.4 These guideline recommendations are supported by recent randomised trials that have provided new insights into the safety and effectiveness of these pathways in clinical practice.5–7 Multiple pathways have been proposed that vary according to the thresholds used for decision-making and timing of sampling. Implementing a validated pathway could save healthcare resources and improve the safe delivery of patient care. Here we describe these early rule-out pathways, review their supporting evidence and provide practical advice for their adoption in clinical practice. Cardiac troponin is a highly specific marker of cardiomyocyte injury, which can be detected in the circulation within an hour of the onset of myocardial ischaemia.8 High-sensitivity assays have sufficient analytical precision to quantify very low concentrations of cardiac troponin in the majority of healthy people.9 The …