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

Abstract

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. 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. 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. cTn has insufficient diagnostic value for AMI in OHCA patients. Use of cTn to establish the cause of OHCA results in overdiagnosis of AMI.