Elevated Biochemical Markers of Myocardial Injury are not Associated with Postoperative Cognitive Dysfunction after Coronary Artery Surgery

Background: The systemic inflammatory response to cardiopulmonary bypass (CPB) and organ hypoperfusion during CPB contribute to cerebral and myocardial dysfunction in patients undergoing cardiac surgery. We hypothesized that biochemical markers of myocardial injury [creatine kinase - myocardial band (CK-MB), troponin-I] may be independently associated with postoperative cognitive dysfunction (POCD; an indicator of cerebral dysfunction) in patients undergoing coronary artery bypass graft (CABG) surgery using CPB. Methods: Eighty-eight age- and education-balanced patients=55 years of age undergoing elective CABG with CPB and 28 nonsurgical controls with coronary artery disease were enrolled. Recent verbal and nonverbal memory and executive functions were assessed before surgery, 1 week, and 3 months after surgery using a standard psychometric test battery. Plasma CK-MB and troponin-I concentrations were determined before and at the end of surgery. Plasma troponin-I concentrations were also measured 24 hours after surgery. Results: Performance on two cognitive tests decreased at least two standard deviations (SD) from baseline and performance on five additional tests decreased 1 SD 1 week after surgery. After 3 months, performance on six tests was at least a 1 SD below baseline. CK-MB and troponin-I concentrations were significantly (p<0.00001) elevated after surgery. There was no correlation between overall cognitive function (measured by average z-score) and postoperative CK-MB or troponin-I concentrations 1 week or 3 months after surgery. Conclusion: The results suggest that elevated postoperative CK-MB or troponin-I concentration alone is not associated with the subsequent development of short- and medium-term impairment of cognitive functions after CABG.