Chapman AR, Adamson PD, Shah ASV, et al. - Given the recommendation by the Universal Definition of Myocardial Infarction for undertaking high-sensitivity cardiac troponin (hs-cTn) testing and classifying patients with myocardial injury based on etiology, researchers sought to determine the clinical implications of implementing this guideline. A hs-cTn assay and the recommendations of the Universal Definition were implemented in 48,282 consecutive patients with the suspected acute coronary syndrome in this stepped-wedge cluster randomized controlled trial. The diagnosis of type 1 myocardial infarction increased by 11% (510/4,471), type 2 myocardial infarction increased by 22% (205/916), and acute and chronic myocardial injury by increased by 36% (443/1,233) and 43% (389/898), respectively, following implementation. Findings suggest that patients at high risk of cardiovascular and non-cardiovascular events could be identified with the implementation of high-sensitivity cardiac troponin and the recommendations of the Universal Definition of Myocardial Infarction. However, the implementation seemed not associated with consistent increases in treatment or improved outcomes.