Dephosphorylation of connexin 43 ratio in forensic autopsy cases of sudden cardiac death without coronary artery involvement: a marker of early ischemic injury in cardiomyocytes.

Lethal arrhythmia is a common cause of sudden cardiac death. However, no identifiable histological abnormalities were found. This study aimed to clarify whether ischemia-induced changes in myocardial cells caused by a sudden decrease in coronary blood flow are observed in cases of sudden cardiac death without coronary artery involvement. The autopsy cases included sudden cardiac death without coronary artery involvement, acute coronary syndrome, or other sudden deaths. We performed double fluorescent immunostaining for connexin 43 (Cx43) and its dephosphorylated form (npCx43) and calculated the npCx43 rate. Additionally, immunohistochemical analysis was performed on the complement system activation in cardiomyocytes using an anti-C5b-9 antibody, and mRNA expression of hypoxia-inducible factor-1 (HIF-1) was assessed. The results showed a significant increase in npCx43 rate, whereas C5b-9 or HIF-1 mRNA expression did not significantly change. These findings suggest that the npCx43 expression rate may be a useful indicator of rapid ischemic changes induced in the myocardium of patients who die of sudden cardiac death without coronary artery involvement.