Impaired cognition preceding cardiac surgery is related to cerebral ischemic lesions

Abstract

Cognitive dysfunction is more frequent after cardiac surgery. However, the preoperative cognitive state is seldom assessed when the effects of cardiac surgery on cognition are investigated. Postoperative cognitive dysfunction may be associated with the preoperative cognitive state and the existence of cerebral ischemic lesions in patients who undergo cardiac surgery. Data were collected prospectively on 362 consecutive patients scheduled to undergo elective cardiac surgery. The brains of all patients were imaged by magnetic resonance imaging (MRI) to assess prior cerebral infarctions, carotid artery stenosis and intracranial arterial stenosis, and diffusion-weighted imaging (DWI) was used to assess acute cerebral ischemia. Patients were classified with impaired cognitive function prior to surgery if their score on the Hasegawa dementia rating scale was <24. Postoperative cognitive dysfunction from baseline was determined using four neuropsychological tests. Prior to surgery 40 patients (11%) were assessed with impaired cognition. Relative to the other patients, these patients were older and less well educated, and they had significantly higher rates of peripheral vascular disease, white matter lesions, cerebral infarction on MRI, carotid artery stenosis and postoperative cognitive dysfunction. Of these 40 cognitively impaired patients, seven (18%) had cerebral ischemia, based on DWI images before surgery; in comparison, nine of the 322 patients (3%) without preoperative cognitive impairment were found to have abnormalities on the DWI images (P < 0.001). An analysis by stepwise logistic regression demonstrated that the significant risks for preoperative cognitive impairment were advanced age, lower attained level of education, peripheral artery disease, prior cerebral infarctions, and abnormalities on DWI images. These findings suggest that preoperative cognitive impairment associated with cerebral ischemic lesions and an increased risk of postoperative cognitive dysfunction existed in our patient cohort undergoing cardiac surgery.