Early diagnosis of acute myocardial infarction in patients with mild elevations of cardiac troponin.

BACKGROUND: The early diagnosis of acute myocardial infarction (AMI) in patients with mild elevations of high-sensitivity cardiac troponin (hs-cTn) is a challenge. It is unclear whether copeptin, a marker of endogenous stress, or 1h-hs-cTn changes are better suited to address this important unmet clinical need.
METHODS: We prospectively enrolled patients presenting with symptoms suggestive of AMI to the emergency department (ED). Two independent cardiologists adjudicated the final diagnosis. Mild hs-cTn elevations were defined as 26.2 ng/L (99th percentile) to 75 ng/L for hs-cTnI, and 14 ng/L (99th percentile) to 50 ng/L (biological-equivalent to 75 ng/L for hs-cTnI) for hs-cTnT.
RESULTS: Among 1356 patients, 80 (6%) had mild hs-cTnI elevations at presentation. Within this group, AMI was the final diagnosis in 39 patients (49%). The diagnostic accuracy for the diagnosis of AMI as quantified by the area under the receiver operating characteristic curve (AUC) was 0.51 (95% CI 0.39-0.64) for hs-cTnI at presentation, 0.58 (95% CI 0.45-0.71) for copeptin at presentation, and 0.78 (95% CI 0.68-0.88) for 1h-hs-cTnI changes, which was significantly higher as compared to copeptin (p = 0.02) or hs-cTnI alone (p < 0.001). The additional use of 1h-hs-cTnI changes, but not of copeptin, improved diagnostic accuracy of hs-cTnI at presentation (AUC 0.80, 95% CI 0.70-0.90; p = 0.002 for comparison). Similar findings regarding copeptin and 1h-hs-cTnT/I changes were obtained for mild hs-cTnT elevations.
CONCLUSIONS: About 6-22% of patients presenting with suggestive AMI to the ED have mild hs-cTnT/I elevations at presentation. In contrast to copeptin, the addition of 1h-hs-cTn changes substantially improves the early diagnosis of AMI.