Objective: There is a clinical need for early and accurate diagnosis of acute myocardial infarction (AMI). Current European Society of Cardiology (ESC) guidelines recommend diagnosis of non-ST-elevation AMI based on serial troponin measurements. We aimed to challenge the ESC guidelines using 1) a high-sensitivity troponin I (hs-TnI) baseline cutoff, 2) an absolute hs-TnI change after 1 hour and 3) additional application of an ischemic ECG.
Methods: 1,516 patients with suspected AMI presenting to the emergency department were included. Hs-TnI was measured directly at admission, after 1 and 3 hours. We investigated baseline concentrations, absolute changes of hs-TnI and additional application of an ischemic ECG to diagnose AMI. A positive predictive value (PPV) of more than 85% was targeted.
Results: The median age of the study population was 65 years; 291 patients were diagnosed with AMI. The PPV of the 3-hours ESC algorithm was 85.5% (CI 79.7, 90.1) and 65.8% (CI 60.5,70.8) for the 1-hour algorithm. Using a high baseline hs-TnI concentration of 150 ng/L resulted in a PPV of 87.8% (CI 80.9,92.9). Alternatively, a hs-TnI change of 20 ng/L after 1 hour, resulted in a PPV of 86.5% (80.9,91.0), respectively for the diagnosis of AMI. Additional use of an ischemic ECG increased the PPV to 90.5% (CI 83.2,95.3), while reducing the efficacy.
Conclusion: The diagnosis of AMI based on hs-TnI is challenging. The application of absolute hs-TnI changes after 1 hour may facilitate rapid rule-in of patients.
Trial registration: www.clinicaltrials.gov (NCT02355457).