Markers of Mitochondrial Injury and Neurological Outcomes of Comatose Patients after Cardiac Arrest

Background and Objectives: Most patients who are successfully resuscitated from cardiac arrest remain comatose, and only half regain consciousness 72 h after the arrest. Neuroprognostication methods can be complex and even inconclusive. As mitochondrial components have been identified as markers of post-cardiac-arrest injury and associated with survival, we aimed to investigate cytochrome c and mtDNA in comatose patients after cardiac arrest to compare neurological outcomes and to evaluate the markers' neuroprognostic value. Materials and Methods: This prospective observational study included 86 comatose post-cardiac-arrest patients and 10 healthy controls. Cytochrome c and mtDNA were determined at admission. Neuron-specific enolase (NSE) was measured after 72 h. Additional neuroprognostication methods were performed when patients remained unconscious. Cerebral performance category (CPC) was determined. Results: Cytochrome c was elevated in patients compared to healthy controls (2.029 [0.85-4.97] ng/mL vs. 0 [0.0-0.16], p < 0.001) but not mtDNA (95,228 [52,566-194,060] vs. 41,466 [28,199-104,708] copies/mu L, p = 0.074). Compared to patients with CPC 1-2, patients with CPC 3-5 had higher cytochrome c (1.735 [0.717-3.40] vs. 4.109 [1.149-8.457] ng/mL, p = 0.011), with no differences in mtDNA (87,855 [47,598-172,464] vs. 126,452 [69,447-260,334] copies/mu L, p = 0.208). Patients with CPC 1-2 and CPC 3-5 differed in all neuroprognostication methods. In patients with good vs. poor neurological outcome, ROC AUC was 0.664 (p = 0.011) for cytochrome c, 0.582 (p = 0.208) for mtDNA, and 0.860 (p < 0.001) for NSE. The correlation between NSE and cytochrome c was moderate, with a coefficient of 0.576 (p < 0.001). Conclusions: Cytochrome c was higher in comatose patients after cardiac arrest compared to healthy controls and higher in post-cardiac-arrest patients with poor neurological outcomes. Although cytochrome c correlated with NSE, its neuroprognostic value was poor. We found no differences in mtDNA.