What is the incidence of major adverse cardiac events in emergency department chest pain patients with a normal ECG, thrombolysis in myocardial infarction score of zero and initial troponin <=99th centile: an observational study?

Objective To determine the rate of major adverse cardiac events (MACE) in patients assessed in an emergency department (ED) for chest pain with a non- ischaemic ECG, Thrombolysis in Myocardial Infarction (TIMI) score of 0 and initial troponin I (TnI) <= 99th centile. Methods This was a sub-study of a prospective observational study of adult patients with potentially cardiac chest pain who underwent evaluation for acute coronary syndrome in an urban teaching hospital. Adult patients with non-traumatic chest pain were eligible for inclusion. Those with ECG evidence of acute ischaemia or an alternative diagnosis were excluded. Data collected included demographic, clinical, ECG, biomarker and outcome data. Low risk was defined as a TIMI risk score of 0 and initial TnI <= 99th centile. Primary outcome of interest was defined as MACE within 7 days. MACE included death, cardiac arrest, revascularisation, cardiogenic shock, arrhythmia, and prevalent (cause of presentation) and incident (occurring within the follow-up period) myocardial infarction (MI). Analysis was by descriptive and clinical performance analyses. Results 651 patients were studied of whom 215 met the low risk criteria. There was one MACE in this group (0.47%, 95% CI 0.08% to 2.6%)-a revascularisation within 7 days without prevalent MI. Negative predictive value of low risk classification was 99.5% (95% CI 97% to 100%) at both 7 and 30 days. Negative likelihood ratio, weighted by prevalence, was 0.005 at both intervals. Conclusion Risk stratification for early discharge based on ECG, TIMI score of 0 and presentation TnI <= 99th centile appears to identify a group at very low risk of MACE. Research to prospectively validate this is warranted.