Short-Term and Long-Term Cognitive Outcomes in Adults After Cardiac Surgery: Domain-Specific Cognitive Changes, EEG and Neurovascular Unit Markers

Coronary artery bypass grafting (CABG) is one of the most effective ways to surgically correct coronary atherosclerosis. However, the postoperative cognitive decline often develops in patients who undergo CABG. According to various studies, the frequency of postoperative cognitive dysfunction (POCD) after cardiac surgery is 50-80% at the time of hospital discharge and remains present in 20-50% of patients in long-term period after surgery. The presence of POCD is associated with a decrease in surgery effectiveness and impairments in daily functioning, and is a reliable marker of unfavourable long-term prognosis (e.g., dementia and death). This prospective randomized study will be included the adult patients with stable coronary artery disease aged 45-75 years who admitted for planned CABG at the Federal State Budgetary Scientific Institution of Research Institute of Complex Issues of Cardiovascular Diseases. The study complies with the Good Clinical Practice standards and the principles of the Declaration of Helsinki. The study protocol was approved by the institutional Ethics Committee (01/2011-2520). Prior to inclusion in the study, all participants will be provided written informed consent and underwent basic cognitive screening using the Mini-Mental State Examination (MMSE) scale. The exclusion criteria are as follows: life-threatening rhythm disturbances, chronic heart failure (NYHA functional class III and higher), chronic obstructive pulmonary disease, malignant pathology, drug addiction, stroke, and other brain injuries. All the patients will be underwent general medical, neurological, instrumental examinations and extended neuropsychological assessment using the software Status PF as well as electroencephalographical examination 3-5 days before CABG, at 7-10 days after surgery and 5-7 years after CABG. POCD is determined by a 20% decrease in the cognitive indicator compared to that at baseline on 20% of the tests included in the Status PF battery. The serum concentrations of markers of the neurovascular unit (S100b, NSE, and BDNF) will be measured 3-5 days before CABG, within the first 24 h after surgery, and at 7-10 days after CABG.

In summary, the long-term neurophysiological effects following cardiac surgery are poorly understood. Moreover, little is known about the structure of cognitive impairment during the long-term postoperative period and the corresponding functional activity of the brain. The detection of minimal or subclinical signs of brain dysfunction following CABG is still under debate. Prior studies have shown the relationship between EEG abnormalities and cognitive impairment. However, little is known about EEG changes and concentrations of markers of the neurovascular unit in patients after on-pump CABG. To facilitate and improve the diagnostic accuracy, detailed neuropsychological examination using the multichannel digital EEG, serum concentrations of markers of the neurovascular unit and psychometric tests may be used to detect the long-term brain changes associated with postoperative cognitive impairment. Therefore, the study aims to evaluate the neurophysiological outcomes of patients 5-7 years after CABG.