Kengo Maekawa

Cerebral dysfunction after coronary artery bypass surgery

Cerebral dysfunction after cardiac surgery remains a devastating complication and is growing in importance with our aging populations. Neurological complications following cardiac surgery can be classified broadly as stroke, encephalopathy (including delirium), or postoperative cognitive dysfunction (POCD). These etiologies are caused primary by cerebral emboli, hypoperfusion, or inflammation that has largely been attributed to the use of cardiopulmonary bypass. Preventative operative strategies, such as off-pump coronary artery bypass grafting (CABG), can potentially reduce the incidence of postoperative neurological complications by avoiding manipulation of the ascending aorta. Although off-pump CABG is associated with reduced risk of stroke, there are no convincing differences in POCD between off-pump and on-pump CABG. Recently, the focus of postoperative neurological research has shifted from managing cardiopulmonary bypass to patient-related factors. Identifying changes in brains of aged individuals undergoing cardiac surgery may improve strategies for preventing cerebral dysfunction. Advanced age is associated with more undiagnosed cerebrovascular disease and is a major risk factor for stroke and POCD following cardiac surgery. Preoperative cerebrovascular evaluation and adaptation of surgical strategies will provide preventative approaches for cerebral dysfunction after CABG. This review focuses on recent findings of the relationship between perioperative stress and underlying fragility of the brain in cardiac surgical patients.

Pre-existing cerebral infarcts as a risk factor for delirium after coronary artery bypass graft surgery

OBJECTIVES Delirium is a common and critical clinical syndrome in older patients. We examined whether abnormalities in the brain that could be assessed by magnetic resonance imaging predisposed patients to develop delirium after coronary artery bypass graft surgery. We also analysed the association between delirium and cognitive dysfunction after coronary artery bypass graft surgery. METHODS Data were collected prospectively on 153 patients aged 60 years or older who consecutively underwent elective isolated coronary artery bypass graft surgery. All patients were assessed for prior cerebral infarctions and craniocervical artery stenosis by magnetic resonance imaging (MRI) and angiography of their brains. Atherosclerosis of the ascending aorta was examined by epiaortic ultrasound at the time of surgery. Individual cognitive status was measured using four tests in all the patients before surgery and on the seventh postoperative day. A single psychiatrist diagnosed delirium using the Diagnostic and Statistical Manual of Mental Disorders 4th edition IV criteria. RESULTS Postoperative delirium occurred in 16 patients (10.5%). Compared with patients who did not develop postoperative delirium, delirious patients had significantly higher rates of peripheral artery disease, preoperative decline in global cognitive function and pre-existing multiple cerebral infarctions on MRI. In addition, 9 (56%) of the delirious patients suffered postoperative cognitive dysfunction. Stepwise logistic regression analysis found significant independent predictors of postoperative delirium to be preoperative cerebral infarcts on MRI (odds ratio [OR], 2.26; 95% confidence interval [CI] 1.10-4.78), preoperative decline in global cognitive function (OR 4.54; 95% CI 1.21-16.51) and atherosclerosis of the ascending aorta (OR 2.44; 95% CI 1.03-5.62). CONCLUSIONS Our findings suggested that postoperative delirium was associated with pre-existing multiple cerebral infarctions on MRI, preoperative decline in global cognitive function and ascending aortic atherosclerosis in elderly patients undergoing coronary artery bypass graft surgery and increased risk of postoperative cognitive dysfunction.

Abnormalities in the Brain Before Elective Cardiac Surgery Detected by Diffusion-Weighted Magnetic Resonance Imaging

BACKGROUND Diffusion-weighted magnetic resonance imaging (DWI) has found ischemic lesions in the brain after cardiac surgery. However, preoperative cerebral injury has not been studied closely. In this study, we used DWI to assess the prevalence of abnormalities in patients scheduled for cardiac surgery. METHODS We used conventional magnetic resonance imaging and DWI to study 247 consecutive patients scheduled for elective cardiac surgery. Clinical characteristics, neuropsychological test performance, and radiographic data were collected and compared with a group of patients who had normal findings on DWI. RESULTS Eleven of the 247 patients (4.5%) had cerebral ischemic lesions on DWI before surgery. Compared with patients who had normal findings on DWI, patients who had abnormalities had significantly higher rates of history of cerebrovascular disease (64% versus 12%), cardiac catheterization within 14 days before DWI (91% versus 54%), preoperative cerebral infarctions (45% versus 5%), carotid artery stenosis (36% versus 5%), and preoperative cognitive impairment (55% versus 9%). Of the 11 patients with DWI abnormalities, 5 had delayed elective surgery and follow-up image studies; of these 5, 4 showed no relevant ischemic lesion on preoperative follow-up imaging. Among the other 6 patients, 1 had an infarction due to expansion of the same lesion that was detected on the preoperative DWI. There was no significant difference with regard to the incidence of postoperative stroke and cognitive dysfunction. CONCLUSIONS In all, 4.5% of cardiac surgery patients had existing cerebral ischemic lesions on DWI without obvious neurologic defects. Further studies are required to determine whether the lesions are associated with postoperative cognitive dysfunction or stroke.

Gender Differences in Stroke Risk Among the Elderly After Coronary Artery Surgery

BACKGROUND: Previous studies have shown that women are at higher risk than men for stroke after coronary artery bypass graft (CABG) surgery, but gender differences in systemic atherosclerosis have not been studied adequately. We investigated gender differences in the incidence of craniocervical and ascending aortic atherosclerosis and other risk factors for stroke in elderly patients (age ≥60 yr) undergoing CABG surgery. METHODS: Data were prospectively collected on 720 patients (31.8% women) undergoing CABG surgery. All patients underwent preoperative brain magnetic resonance imaging and angiography to assess for prior cerebral infarctions, carotid artery stenosis, and intracranial arterial stenosis. Epiaortic ultrasound was performed at the time of surgery to assess for atherosclerosis of the ascending aorta. Cognitive status was measured using the Hasegawa-dementia score in all patients before surgery and on the seventh postoperative day. RESULTS: Women were older and had more hypertension and intracranial arterial stenosis than did men. Men had significantly higher rates of hyperlipidemia, peripheral vascular disease, abdominal aortic aneurysm, smoking history, severe carotid artery stenosis, and severe aortic atherosclerosis than did women. Although there were no differences in prior cerebral infarction or preoperative cognitive impairment, the rate of perioperative stroke was marginally higher in men than in women (3.9% vs 1.3%, P = 0.066). Univariate predictors of perioperative stroke were prior cerebral infarctions, ascending aortic atherosclerosis, preexisting cognitive impairment, and peripheral vascular disease. Stepwise logistic regression analysis demonstrated that significant independent predictors of perioperative stroke were prior cerebral infarctions and aortic atherosclerosis. CONCLUSIONS: These data suggest that men are more likely than women to have risk factors for stroke, including severe carotid artery stenosis, severe aortic atherosclerosis, and peripheral vascular disease. The rates of prior cerebral infarction and preoperative cognitive impairment were similar between genders.

Early neuropsychological dysfunction in elderly high-risk patients after on-pump and off-pump coronary bypass surgery

PurposeAdvanced age is associated with systemic atherosclerosis and is a risk factor for neurological dysfunction after coronary artery bypass grafting (CABG). However, few studies have investigated early neurological dysfunction after off-pump CABG in elderly patients.MethodsData were collected prospectively on 218 patients (≥60 years) who underwent elective off-pump (n = 89) or on-pump CABG (n = 129). Four cognitive tests were performed preoperatively and 1 week postoperatively. Neuropsychological (NP) dysfunction was defined as a decrease in an individuals performance in more than two tests of at least 20% from baseline. We compared the incidence of NP dysfunction, stroke, graft patency grading, and systemic atherosclerosis between patients who underwent off-pump and on-pump CABG.ResultsOff-pump patients were more likely to have a history of cerebrovascular disease, peripheral vascular disease, smoking, multiple cerebral infarctions, and severe aortic atherosclerosis. None of the off-pump and three on-pump patients suffered intraoperative strokes (P = 0.27). The incidence of NP dysfunction was 11.2% in the off-pump group and 22.5% in the on-pump group, (P = 0.02). Multivariate analysis revealed that NP dysfunction was associated with cardiopulmonary bypass (CPB) and multiple cerebral infarctions. The off-pump group had fewer vessels grafted (2.4 vs 3.4; P < 0.01), and a higher rate of stenosis (>50%) and occlusion of the grafted vessels (13.0% vs 7.4%; P = 0.01) than the on-pump group.ConclusionOff-pump CABG reduced postoperative NP dysfunction in elderly patients with severe systemic atherosclerosis compared to on-pump CABG.

Low Pre-Existing Gray Matter Volume in the Medial Temporal Lobe and White Matter Lesions Are Associated with Postoperative Cognitive Dysfunction after Cardiac Surgery

Objectives Postoperative cognitive dysfunction (POCD) is recognized as a complication in the elderly after cardiac surgery. Imaging of the brain provides evidence of neurodegeneration in elderly patients; however, abnormalities in brain structure and their relation to POCD are uncertain. This pilot study investigated whether loss of gray matter in the bilateral medial temporal lobe (MTL), seen in preoperative MRI, was associated with POCD. Methods Data were collected prospectively on 28 elderly patients scheduled for elective cardiac surgery. MRI of the brains of all patients were assessed for prior cerebral infarctions, and carotid and intracranial arterial stenosis. Patients also completed six neuropsychological tests of memory, attention and executive function before and after surgery. POCD was defined as an individual decrease in more than two tests of at least 1 standard deviation from the group baseline mean for that test. The degree of gray matter loss in the MTL of each patient was calculated using voxel-based morphometry with three-dimensional, T1-weighted MRI. This represented the degree of gray matter change as a Z score. Results Postoperative cognitive dysfunction was identified in 8 of the 28 patients (29%). Patients with POCD had significantly more white matter lesions on MRI, and greater loss of gray matter in the bilateral MTL (average Z score 2.0±0.9) than patients without POCD. An analysis by stepwise logistic regression identified gray matter loss in the MTL and cerebral infarctions on MRI as independent predictors of POCD. Conclusions These preliminary findings suggested that reduced gray matter in the bilateral MTL and white matter lesions existed in brains of elderly cardiac surgery patients who experienced POCD. Additional studies with larger sample sizes are needed to confirm these findings.