Role of cardiac troponin in the diagnosis of acute myocardial infarction in comatose patients resuscitated from out-of-hospital cardiac arrest

BackgroundTroponin is a major diagnostic criterion of acute myocardial infarction (AMI) but in out-of-hospital cardiac arrest (OHCA) patients, its diagnostic value may be altered by cardiopulmonary resuscitation.MethodsSingle-centre study assessing the diagnostic characteristics of troponin for AMI diagnosis in consecutive patients resuscitated from OHCA between 2002 and 2008 with coronary angiogram (CA) performed on admission. Patients with obvious non-cardiac cause of OHCA, unsustained or absent return of spontaneous circulation were excluded. AMI was defined on CA by the presence of acute occlusion or critical stenosis with intracoronary fresh thrombus easily crossed by an angioplasty wire. Troponin concentration was recorded once on admission and once 6–12 h after the OHCA.ResultsA total of 163 patients aged 56 (median) years (interquartile range (IQR) 48–65) was included, all comatose. Most prevalent initial OHCA rhythms were ventricular fibrillation (49%) and asystole (41%). AMI was diagnosed on coronary angiogram in 37% of the patients.Median troponin concentration on admission was 1.7 (0.3–10) ng ml−1 and sensitivity for AMI diagnosis was 72% and specificity 75% for a 2.5 ng ml−1 cut-off. A combined criterion comprising ST elevation and troponin >2.5 ng ml−1 had a sensitivity of 93% and specificity of 64%.Six to twelve hours after the OHCA, median troponin concentration was 7.6 ng ml−1 (1.4–47.5), sensitivity was 84% and specificity 84% for a 14.5 ng ml−1 cut-off.ConclusionTroponin I has a good diagnostic value for AMI diagnosis in OHCA patients. In combination with ST elevation, troponin I on admission achieves a very high sensitivity.