Early markers for myocardial ischemia and sudden cardiac death

Abstract

The post-mortem diagnosis of acute myocardial ischemia remains a challenge for both clinical and forensic pathologists. We performed an experimental study (ligation of left anterior descending coronary artery in rats) in order to identify early markers of myocardial ischemia, to further apply to forensic and clinical pathology in cases of sudden cardiac death. Using immunohistochemistry, Western blots, and gene expression analyses, we investigated a number of markers, selected among those which are currently used in emergency departments to diagnose myocardial infarction and those which are under investigation in basic research and autopsy pathology studies on cardiovascular diseases. The study was performed on 44 adult male Lewis rats, assigned to three experimental groups: control, sham-operated, and operated. The durations of ischemia ranged between 5 min and 24 h. The investigated markers were troponins I and T, myoglobin, fibronectin, C5b-9, connexin 43 (dephosphorylated), JunB, cytochrome c, and TUNEL staining. The earliest expressions (≤30 min) were observed for connexin 43, JunB, and cytochrome c, followed by fibronectin (≤1 h), myoglobin (≤1 h), troponins I and T (≤1 h), TUNEL (≤1 h), and C5b-9 (≤2 h). By this investigation, we identified a panel of true early markers of myocardial ischemia and delineated their temporal evolution in expression by employing new technologies for gene expression analysis, in addition to traditional and routine methods (such as histology and immunohistochemistry). Moreover, for the first time in the autopsy pathology field, we identified, by immunohistochemistry, two very early markers of myocardial ischemia: dephosphorylated connexin 43 and JunB.

Diagnosis of myocardial infarction at autopsy: AECVP reappraisal in the light of the current clinical classification

“…Several immunohistochemical markers have been investigated for the diagnosis of early MI, mostly markers for proteins that accumulate (such as fibronectin and C5b-9) or leak out of (such as troponins, myoglobin, S100A1) cardiomyocytes following ischemia. Other protein markers have been shown to undergo early changes in their phosphorylation state, as is demonstrated for connexin 43 [54,55]. Markers/mediators of early inflammation (CD15, IL-6, TNF-α, IL-15, IL-8, CD18 and tryptase) have also been proposed [56].…”

“…Markers/mediators of early inflammation (CD15, IL-6, TNF-α, IL-15, IL-8, CD18 and tryptase) have also been proposed [56]. Some of them are promising in terms of early expression and specificity (dephosphorylated connexin 43), but they have been mainly investigated in experimental models [55]. When tested in human post-mortem samples, these markers keep their early expression profile, but lose their specificity [4].…”

“…Therefore, further investigations are needed before their eventual introduction in routine. Moreover, several pathologic or iatrogenic states such as CPR (including injection of catecholamines), autolysis, pre-existing ischemic events and medical treatments [4,55] may influence the staining pattern and can interfere with a diagnosis of ischemic injury. Currently, a diagnosis of early myocardial injury in absence of changes in H&E stains could be based on a combination of fibronectin and C5b-9 immune stains (Fig.…”

“…6). C5b-9 staining is more sensitive and specific than fibronectin staining, but fibronectin positivity starts earlier than C5b-9 [55]. In most cardiac transplant centres, C4d immunostaining is used routinely to detect myocardial injury on paraffin sections but the exact timing is unknown ( Fig.…”

Strategy for postmortem diagnosis of myocardial infarction

“…Necrosis of cardiomyocytes is a crucial finding at MI autopsy, but earliest findings of myocardial injury including contraction band necrosis may be subtle and/or nonspecific before evident neutrophilic infiltration occurring 6 to 12 h after the onset of the ischemic attack [4]. Immunohistochemical markers may serve as early detection, but it takes at least 1 h after the onset of the attack [4].…”