Cardiac troponin for the diagnosis of acute myocardial infarction in patients after out-of-hospital cardiac arrest

BACKGROUND: After out-of-hospital cardiac arrest (OHCA), global ischemia may cause cardiac troponin (cTn) elevation and false-positive diagnoses of acute myocardial infarction (AMI). We determined the diagnostic value of cTn to diagnose AMI in OHCA patients. METHODS: OHCA patients who survived to discharge were included. Hospital records were assessed, blinded to cTn, to determine the diagnosis AMI. High-sensitivity troponin T (hs-TnT) and troponin I (TnI) were analysed. RESULTS: Of 618 patients, ST-elevation MI (STEMI) was diagnosed in 179 patients (29 %), non-ST elevation MI (NSTEMI) in 77 patients (13 %) and 362 patients (59 %) had no AMI. There was a significant difference in first hs-TnT between STEMI and NSTEMI patients (p ≤ 0.001) and between NSTEMI patients and patients without AMI (p = 0.013). To rule in any AMI (exceeding 4 × upper reference limit of normal (URL), specificity was 74 % (95 % CI 69-79) and positive predictive value 60 % (95 % CI 53-68). To rule out any AMI (not exceeding 1× URL), sensitivity was 95 % (95 % CI 92-98) and negative predictive value 83 % (95 % CI 72-94). AUC of the ROC curves of STEMI and NSTEMI, vs. no AMI were 0.772(95 % CI 0.721-0.824), 0.657(95 % CI 0.575-0.740) respectively and STEMI vs. NSTEMI 0.649(95 % CI 0.561-0.738). Number of shocks (p < 0.001) and time until return of spontaneous circulation (p < 0.001) were significantly correlated to peak hs-TnT in patients without AMI. CONCLUSIONS: cTn has insufficient diagnostic value for AMI in OHCA patients. Use of cTn to establish the cause of OHCA results in overdiagnosis of AMI.