Postmortem cardiac troponin I and creatine kinase MB levels in the blood and pericardial fluid as markers of myocardial damage in medicolegal autopsy

The present study investigated cardiac troponin I (cTnI) and creatine kinase MB (CK-MB) in the blood and pericardial fluid from medicolegal autopsy cases (n=234, within 48h postmortem) with regard to the cause of death. The cTnI and CK-MB levels in cardiac, peripheral blood and pericardial fluid generally showed a mild and gradual postmortem time-dependent elevation (r=0.231-0.449, P<0.05-0.001). However, postmortem elevation of cTnI was larger for specific causes of death including acute myocardial infarction (AMI), cerebrovascular diseases (CVD), hyperthermia, fatal methamphetamine (MA) abuse and carbon monoxide (CO) intoxication and insignificant for recurrent myocardial infarction (RMI), chronic congestive heart diseases (CHD) and drowning, while that of CK-MB was greater for CO intoxication and insignificant for drowning. Cardiac blood and pericardial cTnI levels were relatively high for AMI, RMI, hyperthermia, MA abuse and CO intoxication, and was low for drowning. Elevated CK-MB level was observed for cardiac blood in asphyxiation and MA abuse cases and for peripheral blood in hyperthermia and MA abuse cases. When the cTnI/CK-MB ratio was estimated, it was independent of postmortem time, and the ratios for cardiac blood and pericardial fluid were significantly higher in cases of AMI, RMI, hyperthermia and CO intoxication but lower in cases of drowning. Elevations of cTnI levels in cardiac blood and pericardial fluid were related to the morphological severity of myocardial damage. These findings suggest that elevated cTnI and CK-MB levels in blood and pericardial fluid are related to ischemic, hypoxic and/or cytotoxic myocardial damage, which are characteristic of the cause of death, although the levels increase after death depending on myocardial damage at the time of death.