In this study, we investigated whether cTn elevation was associated with mortality and MACEs in patient admitted to neurosurgical ICU. Major findings of this study were as follows. First, elevated cTnI level was shown in about one-tenth of neurosurgical patients in the overall population. Second, rates of in-hospital mortality and ICU mortality were higher in patients with cTnI elevation than in those without cTnI elevation in the overall study population and the propensity score-matched population. The length of hospitalization was also prolonged in patients with cTnI elevation than in those without cTnI elevation in both populations Finally, multivariable analysis revealed that cTnI elevation were associated with in-hospital mortality and MACE in overall and propensity score-matched population.
cTn is a regulatory protein that can lead to myocardial contraction by controlling calcium-mediated interaction with actin and myosin [5, 20]. Destroyed cardiomyocytes can release cTn into the blood which can be detected using a commercially available immunoassay [5]. Postoperative myocardial injury is an independent predictor of cardiovascular complications and mortality within 30 days and one year in patients undergoing orthopedic or abdominal surgeries [1]. Especially, cTn elevation is associated with worse cardiac outcomes after major surgeries [21]. In addition, elevated cTn measurements among critically ill patients are associated with increased mortality and ICU length of stay [5].
In patients with subarachnoid hemorrhage, electrocardiographic abnormalities, including prolongation of QT interval and repolarization abnormalities, are commonly detected [9, 12]. Especially, cTn elevation has been found in one-third of patients with subarachnoid hemorrhage known to be associated with increased mortality [9, 13]. cTn elevation is also associated with mortality in patients with surgically treated intracerebral hemorrhage and traumatic brain injury [9, 22]. Under stressful conditions such as acute brain injury, stimulation of the hypothalamic paraventricular nucleus as the main control center of the hypothalamic-pituitary-adrenal axis can activate sympathetic output and lead to electrocardiographic abnormalities, arrhythmia, and myocardial injury [23]. In addition, activation of this axis after acute brain injury can cause a significant increase in catecholamines. The catecholamine surge hypothesis is the most widely accepted mechanism of brain-heart interaction [23]. Recent histological studies have shown that catecholamine-mediated myocardial injury may be a major pathophysiology of neurocritical illness [9–11, 24]. Therefore, cardiac injury could be accompanied by neurosurgical or neurocritical illness. It is known to be associated with clinical prognosis [9–11, 22, 24].
Neurosurgical patients with severe brain injury are more likely to develop cardiac injury and MACEs compared to those with benign diseases. Therefore, it is not easy to determine whether elevated cTn itself is associated with a poor prognosis or neurosurgical patients with elevated cTn will show poor prognosis because of their neurocritical illness. Therefore, a propensity score matching method was used to adjust for this confounder in this study. In brief, cTnI elevation was significantly associated with poor clinical outcomes of neurosurgical and neurocritically ill patients. Finally, the majority of morbidity and mortality could be arising from neurocritical illness, although other studies have suggested that cardiac injury might also be a contributing factor [9–11].
This study has several limitations. First, this was a retrospective review of medical records and data extracted from Clinical Data Warehouse. The nonrandomized nature of registry data might have resulted in a selection bias. Second, laboratory tests including cTnI levels were protocol-based for patients with perioperative neurosurgery. They were performed occasionally by non-protocol methods for neurocritically ill patients without neurosurgery. Third, the pathophysiology of acute coronary syndrome could not be determined for a few patients. Cardiac catheterization was not performed in these sick patients because intrahospital transport was impossible due to severe illness. Finally, the distribution of neurosurgical diseases differed from that of the general neurosurgical ICU and the proportion of patients with brain tumors was particularly high.