Plasma Amyloid β42 and Amyloid β40 Levels Are Associated With Early Cognitive Dysfunction After Cardiac Surgery

Background. Decreased cognitive function associated with coronary artery bypass graft surgery is common. These deficits may be similar to the cognitive dysfunction seen in the spectrum of mild cognitive impairment to Alzheimer's disease, which are believed to result from the accumulation of amyloid beta (A beta) peptide in the brain. We measured cognition both before and after coronary artery bypass graft surgery and assayed A beta levels to investigate whether the cognitive dysfunction of cardiac surgery was associated with A beta levels. Methods. The plasma of 332 patients, who had undergone neuropsychological testing before and 3 and 12 months after coronary artery bypass graft surgery, was analyzed for A beta(42) and A beta(40). Patients were classified as having preexisting cognitive impairment if cognitive function was decreased in two or more tests compared with a healthy control group, and postoperative cognitive dysfunction was defined as a decline in two or more tests compared with the group mean baseline score. Results. Preexisting cognitive impairment was present in 117 patients (35.2%), and postoperative cognitive dysfunction was present in 40 (12%) at 3 months and 41 (13%) at 12 months after surgery. Both plasma A beta(42) and A beta(40) levels assessed before the surgery were significantly lower in patients who later had postoperative cognitive dysfunction at 3 months. Conclusions. Decreased preoperative plasma levels of A beta(42) and A beta(40) in patients who exhibit postoperative cognitive dysfunction at 3 months suggest that postoperative cognitive dysfunction at this time may share a common mechanism with mild cognitive impairment and Alzheimer's disease. This process may be exacerbated by anesthesia. (Ann Thorac Surg 2009;88:1426-32) (C) 2009 by The Society of Thoracic Surgeons