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

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1 Abnormalities in the Brain Before Elective Cardiac Surgery Detected by Diffusion-Weighted Magnetic Resonance Imaging Kengo Maekawa, MD, Tomoko Goto, MD, Tomoko Baba, MD, Atsushi Yoshitake, MD, Shoji Morishita, MD, and Takaaki Koshiji, MD Departments of Anesthesiology, Radiology, and Cardiovascular Surgery, Kumamoto Chuo Hospital, Kumamoto, Japan Background. Diffusion-weighted magnetic resonance imaging () has found ischemic lesions in the brain after cardiac surgery. However, preoperative cerebral injury has not been studied closely. In this study, we used to assess the prevalence of abnormalities in patients scheduled for cardiac surgery. Methods. We used conventional magnetic resonance imaging and 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. Results. Eleven of the 247 patients (4.5%) had cerebral ischemic lesions on before surgery. Compared with patients who had normal findings on, patients who had abnormalities had significantly higher rates of history of cerebrovascular disease (64% versus 12%), cardiac catheterization within 14 days before (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 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. 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 without obvious neurologic defects. Further studies are required to determine whether the lesions are associated with postoperative cognitive dysfunction or stroke. (Ann Thorac Surg 2008;86:1563 9) 2008 by The Society of Thoracic Surgeons Neurologic dysfunction after cardiac surgery is a devastating complication that is associated with increased mortality and prolonged hospitalization [1]. Several studies have suggested that the etiology of cerebral injury during cardiopulmonary bypass (CPB) is related to several risk factors [2, 3]. In a previous study, we found that presurgical cerebral ischemic disorders, such as small infarctions, predicted postoperative stroke [4], although most patients with numerous small infarctions were asymptomatic and manifested no clinical signs. Recently, advances in neuroimaging techniques, including cerebral magnetic resonance imaging (MRI) with diffusion-weighted imaging () sequences, have found new ischemic lesions in a substantial number of patients after coronary artery bypass grafting [5 7]. Moreover, has revealed that asymptomatic embolic cerebral infarctions may occur at an unexpectedly high rate after cardiac catheterization [8 10]. Although diagnostic and therapeutic cardiac catheterization is the most common endovascular procedure before cardiac surgery, Accepted for publication July 8, Address correspondence to Dr Maekawa, Department of Anesthesiology, Kumamoto Chuo Hospital, Tainoshima, Kumamoto, , Japan; kenchom@par.odn.ne.jp. presurgical of the brain rarely has been included to evaluate patients, despite its superiority in imaging abnormalities. Preoperative determination of existing cerebral ischemic lesions may help to assess the likelihood and etiology of postoperative neurologic complications. We performed cerebral on consecutive patients before cardiac surgery to prospectively evaluate the incidence of ischemic lesions and to determine their relationship to postoperative neurocognitive function, stroke, and associated risk factors. Material and Methods Patients We prospectively studied a series of consecutive patients who underwent elective cardiac surgery in Kumamoto Chuo Hospital from September 2004 to July Surgery included coronary artery grafting () with CPB (on pump) or without CPB (off pump), mitral valve repair or replacement, or aortic valve replacement. Exclusion criteria were a contraindication to MRI or inability to evaluate cognitive dysfunction and stroke. Contraindications for MRI were claustrophobia, an implanted pacemaker, and some metal prostheses. Demographic and preoperative data recorded in an institutional database 2008 by The Society of Thoracic Surgeons /08/$34.00 Published by Elsevier Inc doi: /j.athoracsur

2 1564 MAEKAWA ET AL Ann Thorac Surg DW-MRI ABNORMALITIES BEFORE CARDIAC SURGERY 2008;86: included age, sex, hypertension, diabetes mellitus, hyperlipidemia, renal insufficiency (creatinine 1.9 mg/ dl), peripheral vascular disease, abdominal aortic aneurysm, and history of atrial fibrillation, smoking, stroke, or transient ischemic attack. The hospital Institutional Review Board approved the present study, and all patients provided their informed consent to participate. MRI Scans We evaluated existing brain abnormalities and the presence of lesions on preoperative scans. Magnetic resonance imaging and magnetic resonance angiography (MRA) were performed on all patients 1 to 7 days before cardiac surgery. The MRI examinations were made with a 1.5 Tesla system (Gyroscan Intera Achieva Nova Dual; Philips Medical Systems, Best, Netherlands). The imaging protocol included a diffusion-weighted, single-shot, spin echo echoplanar sequence (diffusion gradient b values of 0 and 1000 s/mm 2, repetition time [TR] 3000 ms, echo time [TE] 51 ms, slice thickness 5 mm with a 1-mm intersection gap, matrix pixels, 230-mm field of view), turbo fluid attenuated inversion recovery, and T2-weighted turbo spin echo sequences. For, the diffusion gradients for total acquisition were successively and separately applied in three orthogonal directions for a total acquisition time of 30 s. Trace images were then generated and apparent diffusion coefficient maps calculated with a dedicated software tool. Magnetic resonance angiography included intracranial and neck vessels and was performed using a three-dimensional time-of-flight technique. The MRI findings (fluid attenuated inversion recovery and T2) were classified as almost normal or leukoaraiosis; some small infarctions with a diameter of less than 15 mm; or multiple small infarctions or large infarctions greater than 15 mm or those that included the cortical area. The degree of stenosis of intracranial arteries was graded bilaterally by MRA as almost normal; moderate narrowing greater than 50%; or occluded [11]. The degree of stenosis in the carotid arteries was graded based on MRA as normal or mild narrowing of less than 50%; moderate narrowing of 50% to 75%; or severe narrowing greater than 75% or obstruction [12, 13]. The scan results were considered abnormal if the scan revealed an area of hyperintensity on and hypointensity on apparent diffusion coefficient maps relative to the normal brain, signifying cerebral ischemia. The lesions on MRI and MRA findings and the number, size, and location of recent ischemic lesions on were evaluated by two experienced neuroradiologists masked to the clinical and neuropsychological data. Neurologic Evaluation Cognitive status was assessed by four tests administered preoperatively and 1 week after surgery to all patients when they were free of the effects of sedatives. The tests included the Hasegawa dementia score (HDS), the Kana pick-out test, the digit symbol substitution test, and the digit span test (forward and backward). The HDS is a modification of the Mini-Mental State Examination scored from 0 to 30, with higher scores representing a better cognitive state [14]. Preoperative cognitive impairment was defined as HDS less than 24 (equivalent to 24 on the Mini-Mental State Examination). The Kana pickout test measures ability in the executive function of prefrontal lobe. These tests were performed preoperatively by one of three trained investigators (T.B., T.G., or A.Y.) who were assigned randomly to patients. All tests were performed postoperatively by the same investigator (T.B), who was masked to treatment allocation. Postoperative cognitive dysfunction was defined as a decrease of least 20% from baseline in an individual s performance in more than two tests. Postoperative brain MRI or CT was performed only on patients with neurologic deficits lasting more than 24 hours. Stroke was defined as new postoperative neurologic deficits that were confirmed by postoperative MRI or CT of the brain that were verified by neurologists. Patient Management and Evaluation of Arteriosclerosis in the Aorta Diazepam and fentanyl were used to induce and maintain anesthesia, supplemented with isoflurane or sevoflurane during surgery. Surgery with CPB was performed using a membrane oxygenator and roller pump under alpha-stat ph management and moderate hypothermia (28 to 34 C), as described previously [4]. Patients with prior cerebral infarction or severe carotid stenosis were maintained at a mean arterial pressure greater than 70 mm Hg during CPB and rewarmed to maintain no more than a 3 C difference between rectal and CPB perfusion Table 1. Patient Characteristics With Imaging Results Characteristic Present n 11 Absent n 236 p Value a Age (years) b Sex (male/female) 5/6 151/ Hypertension 9 (82) 165 (70) Diabetes mellitus 3 (27) 75 (32) Hyperlipidemia 2 (18) 117 (50) Renal insufficiency 1 (9) 24 (10) Peripheral vascular disease 2 (18) 20 (8) Abdominal aortic aneurysm 0 9 (4) Atrial fibrillation 2 (18) 39 (17) Smoking history 5 (45) 125 (53) History of cerebrovascular 7 (64) 28 (12) disease Cardiac catheterization 10 (91) 127 (57) within 14 days, n 222 Cardiac surgery 6 (55) 101 (43) Off-pump/on-pump 6/0 39/62 /valvular 1 (9) 27 (11) Valvular 4 (36) 108 (46) Values inside parentheses represent percentages within groups. a The p values refer to comparisons between groups. b Expressed as mean SD. coronary artery bypass grafting; diffusion-weighted magnetic resonance imaging.

3 Table 2. Clinical and Radiologic Characteristics of 11 Patients With Abnormalities on Diffusion-Weighted Magnetic Resonance Imaging () Pt. No. Sex/Age (Years) Cardiac Surgery HT/DM CVD/Afib MRI Grade MRA Interval From Catheterization to (Days) Size (mm); Location Preop HDS Preop Symptoms 1 F/79 AVR Yes/No Yes/No ; L caudate 29 No 2 M/64 Off-pump Yes/Yes Yes/No 2 L ICA 50% 2 6, 10; L frontal 22 Right hemiparesis 3 F/77 No/Yes No/No ; L middle cerebellar 19 Vertigo MVR peduncle 4 F/82 AVR Yes/No Yes/No 3 4 6; L frontal 23 No 5 M/67 Off-pump Yes/No Yes/No 3 L ICA 75%; MCA, PCA 50% 5 3; L posterior limb of internal capsule 17 No 6 F/73 MVR Yes/No No/Yes ; R frontal 26 No 7 F/65 Off-pump Yes/No Yes/No , 5, 7; L corona radiata 30 No 8 M/81 Off-pump Yes/No No/No 2 R ICA 90% 12 5; L cerebellum 27 No 9 M/78 Off-pump Yes/Yes Yes/No 3 R ICA 75% 14 4; L frontal 27 No 10 M/77 Off-pump Yes/No No/No 3 R ICA 75% 14 7; L cortical temporal 22 No 11 F/73 MVR No/No Yes/Yes ; L temporal 23 Right hemiparesis Afib atrial fibrillation; AVR aortic valve replacement; coronary artery bypass graft surgery; CVD cerebrovascular disease; DM diabetes mellitus; F female; HDS Hasegawa dementia score; HT hypertension; ICA internal carotid artery; L left; M male; MCA middle cerebral artery; MRA magnetic resonance angiography; MRI magnetic resonance imaging; MVR mitral valve replacement or repair; PCA posterior cerebral artery; R right. Ann Thorac Surg MAEKAWA ET AL 2008;86: DW-MRI ABNORMALITIES BEFORE CARDIAC SURGERY 1565

4 1566 MAEKAWA ET AL Ann Thorac Surg DW-MRI ABNORMALITIES BEFORE CARDIAC SURGERY 2008;86: temperatures. In other patients, mean arterial pressure was maintained between 50 and 70 mm Hg, and the difference between rectal and CPB perfuse temperature was restricted to 5 to 6 C during rewarming. Off-pump surgery was performed with a Medtronic Octopus IV (Medtronic Inc, Minneapolis, MN). A deep pericardial traction suture was applied for cardiac displacement. A cell-saving device was used to conserve intraoperative blood. All patients underwent epiaortic ultrasonography scans at the time of surgery to screen for atherosclerosis of the ascending aorta. We divided the ascending aorta from the aortic valve to the innominate artery into three segments and assessed intimal thickening off-line on videotape records, as described previously [15]. The degree of atherosclerosis in the ascending aorta was graded as almost normal or mild ( 3mm intimal thickening); moderate ( 3 mm intimal thickening involving one segment of the ascending aorta); or severe ( 3 mm intimal thickening involving 2 or all 3 segments, often with protruding surface ulcerations or mobile components). All patients were assessed by one echocardiography technician. Based on the findings from real-time imaging, the need to modify cannulation, clamping, proximal graft anastomotic sites, or cardioplegia cannulation sites was determined by the cardiac surgeons. Statistical Analysis Patients were divided into two groups according to their degree of preoperative abnormality: absent (no abnormalities) and present (with abnormalities). From the results of previous studies [8 10], we postulated that early cardiac catheterization before cardiac surgery might significantly increase the incidence of abnormalities. To determine whether there was a trend in relation to timing cardiac catheterization, we examined the rates of cardiac catheterization within 14 days before MRI scans. The choice of a cut-off at 14 days was based on a gradual increase in apparent diffusion coefficient to at or above normal, usually by 14 days [16]. Continuous variables are expressed as mean SD. Comparisons between the two groups were made with Student s t test for continuous variables and with the 2 or Fisher s exact test for categorical variables. A p value less than 0.05 was considered significant. Results From September 2004 to July 2007, 299 consecutive patients underwent elective cardiac surgery. From this total, 52 patients were excluded from the study, including 38 patients who were contraindicated for MRI; 8 patients who because of physical or mental status could not participate in neurologic testing; and 6 who had prolonged tracheal intubation ( 7 days) for pulmonary complications. All of the remaining 247 patients (82.6%) agreed to participate. There were 91 women and 156 men who ranged in age from 31 to 89 years (mean, 70 9). The was performed an average of 4 2 days before cardiac surgery. Fourteen patients underwent before cardiac catheterization; we excluded these 14 patients from the assessment of timing of cardiac catheterization. Abnormalities were detected by before cardiac surgery in 11 of the 247 patients (4.5%). The present group had a more frequent history of cerebrovascular disease and a significant higher rate of cardiac catheterization within the 14 days before MRI scans (Table 1). Table 2 summarizes the lesion characteristics for the 11 patients in the present group. Nine patients had a single lesion, and the other patients had 3 and 2 lesions. Lesions were small, averaging less than 7 mm, with a maximum diameter of 11 mm. There were 14 cerebral ischemic lesions, 13 in the left hemisphere and 1 in the right, with 86% found supratentorially. Most lesions (71%) were located in the white matter (corona radiate, internal capsule, subcortical frontal and temporal lobes). Three of the 11 patients (27%) had clinically apparent neurologic abnormalities before their cardiac surgery. One of these patients (patient 11, Table 2) with right hemiparesis had atrial fibrillation. Another 2 patients (patients 2 and 3; Table 2) had symptoms within a few minutes after cardiac catherization. Of the 11 patients with abnormalities, 5 had elective surgery delayed by 2 to 4 weeks (24 7 days) and follow-up imaging studies. Of these 5 patients (patients 1 through 4 and 6; Table 2), 1 (patient 2; Table 2) demon- Fig 1. Diffusion-weighted magnetic resonance imaging (MRI) of a 67-year-old man (patient 5, Table 2) without any demonstrable neurologic deficits before off-pump coronary artery bypass graft surgery. (A) The preoperative MRI scan revealed a small diffusion abnormality on the left posterior limb of the internal capsule. (B) Another scan performed 5 days after surgery demonstrated that the size of the diffusion restriction lesion had increased; the patient had dysarthria and right hemiparesis.

5 Ann Thorac Surg MAEKAWA ET AL 2008;86: DW-MRI ABNORMALITIES BEFORE CARDIAC SURGERY Table 3. Prevalence of Intracranial and Carotid Artery Stenosis, Atherosclerosis of the Ascending Aorta, and Perioperative Neurologic Complications Present (n 11) Absent (n 236) p Value a MRI (brain) Normal or leukoaraiosis 2 (18) 180 (76) Some small infarctions 4 (37) 45 (19) Multiple or broad 5 (45) 11 (5) infarctions MRA (carotid arteries) Normal or mild 6 (55) 211 (89) Moderate 1 (9) 13 (6) Severe or obstruction 4 (36) 12 (5) MRA (cerebral arteries) Normal or mild 10 (91) 229 (97) Moderate 1 (9) 5 (2) Occluded 0 2 (1) Aortic atherosclerosis Normal or mild 9 (82) 204 (86) Moderate 2 (18) 20 (9) Severe 0 12 (5) Preoperative cognitive 6 (55) 22 (9) impairment Postoperative cognitive 2 (18) 47 (20) dysfunction Perioperative stroke 1 (9.1) 4 (1.7) Values inside parentheses represent percentages within groups. a The p values refer to comparisons between groups. diffusion-weighted magnetic resonance imaging; MRA magnetic resonance angiography; MRI magnetic resonance imaging. strated subsequent abnormalities in the right corona radiate (2 lesions) whereas 4 showed no relevant ischemic lesions on preoperative follow-up studies. Postoperative CT or MRI was performed in 3 of 11 patients (27%; patients 2, 5, 9; Table 2). One patient (patient 5, Table 2) had a small area with a diffusion abnormality that was larger on the postoperative MRI sequence, and he had dysarthria and right hemiparesis (Fig 1). This case was a 67-year-old man with a history of stroke, and carotid and intracranial artery stenosis. He had a cardiac catherization 5 days before the preoperative MRI scan without clinical signs. On the other hand, in the absent group, postoperative CT or MRI was performed in 17 of 236 patients (7%). Of these 17 patients, postoperative performed on 11 and revealed acute cerebral infarctions in 4 (36%); 2 patients had right hemiparesis and 2 patients had left hemiparesis. Table 3 lists the prevalence of intracranial and carotid artery stenosis, atherosclerosis of the ascending aorta, preoperative cognitive impairment, postoperative cognitive dysfunction, and stroke. The present group had a significantly higher rate of cerebral infarction, carotid artery stenosis, and preoperative cognitive impairment before surgery. There was no statistical difference in postoperative cognitive dysfunction and stroke between the two groups. Comment 1567 This study demonstrated a 4.5% incidence of abnormalities identified by in patients before cardiac surgery. The findings suggested that patients with abnormalities had more history of cerebrovascular disease, early surgery after cardiac catheterization, cerebral infarction, carotid artery stenosis, and preoperative cognitive impairment. Recent studies with have shown that new cerebral infarctions occurred in 31% to 47% of patients after cardiac surgery that used CPB [5 7]. These findings were made in the presence of methodologic limitations, including a failure to assess the rate of cerebral ischemic lesions before surgery. The importance of evaluating for new cerebral ischemic lesions preoperatively was emphasized by 1 patient who experienced an enlarged lesion that was revealed on the postoperative scan and appeared with a neurologic abnormality. The pathogenesis of preexisting cerebral ischemic lesions is unknown. One possible mechanism is embolization. Recent studies suggest that asymptomatic embolic cerebral infarction may be detected in 2.2% to 22% of patients after left-side heart catheterization using [8 10]. Left-side heart catheterization with coronary angiography or catheterization of cardiac valves is a standard procedure to evaluate patients before cardiac surgery. Lund and coworkers [8] reported that cerebral embolisms were observed frequently by transcranial Doppler ultrasound during left heart catheterization. Omran and associates [9] found a highly significant correlation between fluoroscopy time and cerebral lesions. Total fluoroscopy time represented the overall influence of catheter manipulation, which serves as a potential embolic source because plaques may be dislodged from the ascending aorta or the aortic arch. In addition, is highly sensitive for detecting acute infracts within the first 14 days after they occur. Therefore, the apparent diffusion coefficient typically may remain depressed during the preoperative period. In fact, in the present study 10 of 11 patients (91%) with abnormalities had left heart catheterization within 2 weeks before their cardiac surgery. Other causes exist for embolism, transient ischemic attack, or minor ischemic stroke in the preoperative period. Recent studies of transient ischemic attack patients demonstrated that almost one half of patients had an abnormality that was detectable on [17, 18]. Schulz and colleagues [19] reported that found clinically appropriate ischemic lesions in 57% of minor stroke patients and 14% of transient ischemic attack patients that presented more than 2 weeks after a symptomatic event. It is known that the early risks of stroke after transient ischemic attack are substantially higher. In this study, the present group had a significantly higher rate of preoperative cerebral infarctions and carotid artery stenosis. Additionally, cardiac procedures, particularly using CPB, are suspected to exacerbate neurologic deficits due to embolism, inflammatory response, and hypoperfusion. Cardiopulmonary bypass may aggravate existing neurologic ischemia and potentiate cerebral edema in areas where the blood brain barrier is

6 1568 MAEKAWA ET AL Ann Thorac Surg DW-MRI ABNORMALITIES BEFORE CARDIAC SURGERY 2008;86: disrupted. Patients with preoperative cerebral injury may be more vulnerable to the adverse effects of cardiac surgery. Therefore, we suggest that cardiac surgery is safer if it can be delayed for 2 to 3 weeks. Diffusionweighted imaging may provide useful clinical information to determine the optimal timing of strategies to use in cardiac surgery. Cognitive dysfunction after cardiac surgery has been the subject of many studies [20 22]. These studies have attempted to identify particular aspects of operative procedures that lead to dysfunction. In contrast, the preoperative cognitive status of patients experiencing dysfunction has been studied less well. Millar and coworkers [23] reported that 16% of patients performed poorly on the Stroop test, indicating impaired cognition before surgery. Hogue and colleagues [24] found cognitive impairment in 45% of female patients before their cardiac surgery. In the present study, the present group had a significant decline in cognitive function before surgery compared with the absent group. However, the correlation between the presence of abnormalities uncovered by and cognitive impairment still is uncertain. Restrepo and colleagues [5] studied 13 patients and found that 4 with postoperative defects on had a larger neurocognitive decline than did patients with normal. Barber and coworkers [25] also reported that 43% of patients with postoperative had new ischemic lesions, and cognitive decline was seen in all patients. In contrast, no such association was found in other studies of patients after cardiac surgery [6, 7, 26 28]. Further studies are needed to determine the relationship between lesions and cognitive dysfunction. There were several limitations to the present analysis. Our data were from a single institution. We can not exclude the possibility that our results were biased by institutional standards and patient population. In addition, postoperative was not assessed in our patients, so the correlation between the presence of preoperative abnormalities and postoperative new cerebral ischemic lesions is uncertain. In conclusion, this study demonstrated that, from among 247 consecutive patients scheduled for cardiac surgery, 11 (4.5%) were identified by to have existing abnormalities, including in patients without obvious neurologic deficits. These findings have important implications for our understanding of the etiology of postoperative neurologic complications and for protective strategies to reduce cerebral injury or improve cognitive dysfunction. The authors thank Dr Jon Moon for his editorial assistance. References 1. Roach GW, Kanchuger M, Mangano CM, et al. Adverse cerebral outcomes after coronary bypass surgery. Multicenter Study of Perioperative Ischemia Research Group and the Ischemia Research and Education Foundation Investigators. 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7 Ann Thorac Surg MAEKAWA ET AL 2008;86: DW-MRI ABNORMALITIES BEFORE CARDIAC SURGERY coronary artery bypass surgery. II. Neurologic and cognitive outcomes. J Thorac Cardiovasc Surg 1995;110: Newman MF, Kirchner JL, Phillips-Bute B, et al, for the Neurological Outcome Research Group and the Cardiothoracic Anesthesiology Research Endeavors Investigators. Longitudinal assessment of neurocognitive function after coronaryartery bypass surgery. N Engl J Med 2001;344: Millar K, Asbury AJ, Murray GD. Pre-existing cognitive impairment as a factor influencing outcome after cardiac surgery. Br J Anaesth 2001;86: Hogue CW Jr, Hershey T, Dixon D, et al. Preexisting cognitive impairment in women before cardiac surgery and its relationship with C-reactive protein concentrations. Anesth Analg 2006;102: Barber PA, Hach S, Tippett LJ, Ross L, Merry AF, Milsom P. Cerebral ischemic lesions on diffusion-weighted imaging are associated with neurocognitive decline after cardiac surgery. Stroke 2008;39: Bendszus M, Reents W, Franke D, et al. Brain damage after coronary artery bypass grafting. Arch Neurol 2002; 59: Friday G, Sutter F, Curtin A, et al. Brain magnetic resonance imaging abnormalities following off-pump cardiac surgery. Heart Surg Forum 2005;8:E Cook DJ, Huston J III, Trenerry MR, Brown RD Jr, Zehr KJ, Sundt TM III. Postcardiac surgical cognitive impairment in the aged using diffusion-weighted magnetic resonance imaging. Ann Thorac Surg 2007;83: INVITED COMMENTARY Maekawa and colleagues [1] report the findings from a study of 247 patients who underwent brain diffusionweighted magnetic resonance imaging () prior to elective cardiac surgery. The method of is a sensitive way to detect acute brain ischemic injury and to distinguish new from chronic brain lesions. The findings of this study adds to a growing appreciation of the rising frequency of cerebral vascular disease and brain infarction in patients before cardiac surgery. Indeed multiple studies have shown the frequency of pre-existing cerebral infarcts to be as high as 45% in patients scheduled for cardiac surgery. In most instances, these lesions are clinically asymptomatic and thus they go undetected in the absence of brain imaging. The findings of this study have several implications for clinicians and researchers. First, these data support that with many patients who have widespread vascular disease, cardiac surgery is superimposed on a natural history of this disease; that is, affected patients will have a certain baseline frequency of ongoing brain injury that must be considered when investigating the effects of cardiac surgery on the brain. This is highlighted by the recent work of Selnes and colleagues [2] who found that the rate of cognitive decline for 6 years of follow-up in patients who had documented coronary artery disease was no different than that found in patients who had undergone coronary artery bypass grafting () surgery compared with patients undergoing medical treatment, including percutaneous coronary interventions. Thus, the performance of surgery with cardiopulmonary bypass did not alter the rates of cognitive decline compared with a control group of subjects with vascular disease. Thus, inclusion of a control group was necessary to distinguish what neurologic changes could be attributed to surgery and what could be accounted for by natural progression of pre-existing cerebral vascular disease. A second implication from this study relates to future research in this field, and that is, that due to cost and convenience, preoperative imaging is often skipped. Usually, any acute postoperative infarcts (by ) are believed to have occurred at the time of or soon after surgery; however, the frequency of acute preoperative lesions in 4.5% of this large sample of patients emphasizes that some of these apparent postoperative infarcts may truly be preoperative (if they occurred within a few days before surgery, they will still appear acute postoperatively). A final implication of the study by Maekawa and colleagues [1] is perhaps it is time to consider more widespread screening for cerebrovascular disease in patients scheduled for cardiac surgery. Identification of patients with recent cerebral injury might lead to a decision to delay surgery to avoid infarct expansion with the multiple perturbations from surgery. The authors advise this practice, but there is no clear evidence that the appropriate treatment plan should be in an individual with a preoperative acute infarction. The mechanism and recommendations may be quite different in an individual with an embolus related to cardiac catheterization, which was the likely cause in 10 of the authors 11 patients who had acute preoperative infarcts or preoperative atrial fibrillation, as opposed to an individual with a large-vessel stenosis who might be at higher risk for ongoing cerebral injury. Brain magnetic resonance imaging is expensive and time consuming and the costs versus benefits of this method versus other diagnostic approaches would require careful study. Regardless, the study by Maekawa and colleagues [1] underscores the importance of considering pre-existing and often new brain lesions in our assessments of patients undergoing cardiac surgery. Rebecca Gottesman, MD, PhD Charles W. Hogue, MD The Johns Hopkins Hospital 600 N Wolfe St, Tower 711 Baltimore, MD chogue2@jhmi.edu References 1. Maekawa K, Goto T, Baba T, Yoshitake A, Morishita S, Koshiji T. Abnormalities in the brain before elective cardiac surgery detected by diffusion-weighted magnetic resonance imaging. Ann Thorac Surg 2008;86: Selnes OA, Grega MA, Bailey MM, et al. Cognition 6 years after surgical or medical therapy for coronary artery disease. Ann Neurol 2008;63: by The Society of Thoracic Surgeons /08/$34.00 Published by Elsevier Inc doi: /j.athoracsur