Ruling-In Myocardial Injury and Ruling-Out Myocardial Infarction With the European Society of Cardiology 1-Hour Algorithm

igh-sensitivity cardiac troponin (hscTn) assays are used everywhere in the world except in the United States. 1 One potential advantage of these assays is their ability to triage patients with possible ischemia more rapidly, and there is an understandable desire to find easy, facile algorithms to do this.This approach was taken with hscTn in the evaluation of patients with possible acute myocardial infarction (AMI) with an algorithm developed by the APACE trial (Advantageous Predictors of Acute Coronary Syndromes Evaluation). 2 Intrinsic to it is the concept that ruling-out and ruling-in AMI rapidly (within 1 hour) can be accomplished based on initially low concentrations (<2 ng/L for hscTnI Abbott and <5 ng/L hscTnT Roche) or small changes over the first hour (<2 ng/L hscTnI and <3 ng/L hscTnT) for ruling-out and the use of larger changes (6 ng/L hscTnI and 5 ng/L hscTnT) and fixed cut-off concentrations for ruling-in (see Figure 1 of the article by Pickering et al in this issue of Circulation).3 Unfortunately, validation of this algorithm has often left a good deal to be desired.Nevertheless, it was incorporated into the European Society of Cardiology guidelines.4 In this issue of Circulation, Pickering and colleagues 3 compare the hscTnI assay from Abbott and the hscTnT assay from Roche in terms of their sensitivity and specificity for ruling-in and ruling-out AMI with this algorithm.The pooled analysis included 5 prospective cohort studies from Australia, New Zealand, and Canada involving 2222 patients (mean 59.7 years of age: 53.5% male) who presented to the emergency department (ED) with chest pain suggestive of acute coronary syndrome.Of these patients, 240 (9.7%) were diagnosed as having an AMI.Troponins were measured at 0 and 90 minutes in 1 study and 0 and 2 hours in the others (ie, no study repeated the troponin measurement at 1 hour, as recommended in the European Society of Cardiology algorithm).The overall time from symptom onset to the first troponin measurement was 5.2 hours.Their retrospective observational evaluation followed the guidelines as written.The authors indicate that hscTnI did not perform as well as hscTnT, and the early rule-out sensitivity was less than ED physicians want to ensure patient safety, which is a 1% event rate of adverse events at 30 days.5 From our perspective, the values calculated by the authors are better than we would suggest the data indicate.To understand the data and their ramifications, readers need to understand the problems associated with the approach, some of which were addressed by the authors and some of which were not.First, in the rule-out arm, low values or small changes are used to exclude AMI.These criteria may fail in patients with AMI who present early after the onset of symptoms before hscTn values can rise, as suggested in other studies. 2,6,7 Only 53 patients with AMIs presented in <3 hours, similar to other validation studies, 2,6,7 and it is unclear how many presented in 1 to 2 hours.Perhaps recognition of this limitation led to the addition of a caveat 8 into the guidelines after initial publication that the use of values below the limit of detection should be confined to patients ruling-in Myocardial injury and ruling-out Myocardial infarction With the European Society of Cardiology 1-Hour algorithm