Neurocognitive impairment and driving performance after coronary artery bypass surgery

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1 European Journal of Cardio-thoracic Surgery 23 (2003) Neurocognitive impairment and driving performance after coronary artery bypass surgery Ewa Ahlgren*, Anna Lundqvist, Anders Nordlund, Claes Aren, Hans Rutberg Heart Center, Department of Rehabilitation Medicine and Department of Health and Society, Faculty of Health Sciences, Linköping University Hospital, Linköping, Sweden Received 9 April 2002; received in revised form 16 September 2002; accepted 2 December 2002 Abstract Objective: Neurocognitive impairment is common after cardiac surgery but few studies have examined the relationship between postoperative neuropsychological test performance and everyday behavior. The influence of postoperative cognitive impairment on car driving has previously not been investigated. The purpose of this study was to evaluate neurocognitive function and driving performance after coronary artery bypass grafting (CABG). Methods: Twenty-seven patients who underwent coronary artery bypass grafting with standard cardiopulmonary bypass technique and 20 patients scheduled for percutaneous coronary intervention (PCI) under local anesthesia (control group) were enrolled in this prospective study conducted from April 1999 to September Complete data were obtained in 23 and 19 patients, respectively. The patients underwent neuropsychological examination with a test battery including 12 tests, a standardized on-road driving test and a test in an advanced driving simulator before and 4 6 weeks after intervention. Results: More patients in the coronary artery bypass grafting group (n ¼ 11, 48%) than in the percutaneous coronary intervention group (n ¼ 2, 10%) showed a cognitive decline after intervention (P ¼ 0:01). In the on-road driving test, patients who underwent coronary artery bypass grafting deteriorated after surgery in the cognitive demanding parts like traffic behavior (P ¼ 0:01) and attention (P ¼ 0:04). Patients who underwent percutaneous intervention deteriorated in maneuvering of the vehicle (P ¼ 0:04). No deterioration was detected in the simulator in any of the groups after intervention. Patients with a cognitive decline after intervention also tended to drop in the on-road driving scores to a larger extent than did patients without a cognitive decline. Conclusion: This study indicates that cognitive functions important for safe driving may be influenced after cardiac surgery. q 2002 Elsevier Science B.V. All rights reserved. Keywords: Cardiac surgery; Cerebral complications; Cognitive decline; Driving performance 1. Introduction Severe cerebral complications after cardiac surgery including total cerebral infarction, nonfatal stroke and transient ischemic attack are seen in about 3% of patients undergoing coronary artery bypass grafting (CABG) [1,2]. Furthermore, a decline in mental abilities such as concentration, attention, short-term memory and speed of cognitive processing occurs in 40-80% of patients after CABG. Many of these cognitive impairments are transient and resolve within months but may persist, in up to 35% of the patients, one year after surgery [3,4]. The large variation in the reported incidence of postoperative cognitive dysfunction can be attributed to the cognitive test battery chosen, the different criteria used for definition of cognitive impairment, patient selection and when in the postoperative period * Corresponding author. Tel.: ; fax: address: ewa.ahlgren@lio.se (E. Ahlgren). the patients are evaluated [5]. Older patients, above 70 years of age, are more at risk and have a higher incidence of adverse cerebral outcome [1,3]. The mechanisms responsible for cerebral complications are multifactorial and include cerebral embolization originating from the surgical field, the ascending aorta and the cardiopulmonary bypass (CPB) circuit. Hypotension and a low blood flow state during the heart operation may also play a role in the mechanisms of cerebral injury in patients with a reduced cerebrovascular collateral reserve (for review see Ref. [6]). Anesthesia and nonspecific effects of surgery are also discussed as causes of postoperative cognitive impairment in the elderly. Previous findings suggest that postoperative cognitive dysfunction may persist in about 10% of patients three months after non-cardiac surgery [7]. Despite the substantial number of studies reporting cognitive impairment after cardiac surgery, the short- and long-term effects of this impairment on everyday /02/$ - see front matter q 2002 Elsevier Science B.V. All rights reserved. doi: /s (02)

2 E. Ahlgren et al. / European Journal of Cardio-thoracic Surgery 23 (2003) behavior have not received much attention. An activity of daily life not previously studied, in this particular patient population, is the ability to drive safely after heart surgery. Driving is a complex skill that largely relies on automated motor performance and flexibility learned through continual practice, but also involves attention, rapid cognitive processing and fast judgment [8,9]. Persons above 60 years of age are the fastest growing segment of the driver population and results from a recent study indicate that patients with coronary artery disease are to a large extent active car drivers and continue to drive despite old age [10]. It is not known whether decline in cognitive function after cardiac surgery influences driving performance. Considering the fact that about patients worldwide undergo CABG every year [11], this is a topic of great importance. The aim of this prospective study was to evaluate cognitive function and driving performance, both in real traffic and in an advanced driving simulator before and 4 6 weeks after elective CABG. 2. Materials and methods The study group consisted of 27 patients with stable angina pectoris scheduled for CABG, and 20 patients who underwent percutaneous coronary intervention (PCI) served as a control group. All patients were consecutively recruited from the hospital s waiting lists of patients with coronary artery disease scheduled for either CABG or PCI. Treatment choice (CABG or PCI) was based on type and localization of the coronary artery stenosis with the less invasive PCI method as first choice if suitable. Recruitment pace was governed by the times available for testing procedures. In brief, during the first 6 months of the study all 11 patients recruited were selected from the CABG group. Thereafter, CABG and PCI patients were selected contemporaneously with PCI patients selected to match as far as possible the previously recruited CABG patients on age, gender, education and extent of driving during the 12-month preceding the intervention. The patients underwent neuropsychological testing, a driving test in an advanced driving simulator and, a practical on-road driving test in real traffic with a certified driving inspector 1 3 days before and 4 6 weeks (study group: 36 ^ 4 days and control group: 35 ^ 6 days) after intervention. All participants had had their driving licenses for more than 30 years. No one had a history of alcohol abuse or a documented neurological or psychiatric disorder or cerebral lesion that might interfere with the recovery process. In the study group one patient had a postoperative stroke, one patient refused postoperative testing and two patients could not be tested due to scheduling problems. In the control group one patient planned for PCI was converted to surgery with CABG. A final sample of 23 study patients and 19 control patients with complete pre- and post-intervention data was evaluated. A further six patients in the study group and two patients in the control group dropped out due to nausea in the simulator. Seventeen patients from each group were thus evaluated in the driving simulator. There were no differences in mean age, driving experience, or education level between the dropouts and the patients who completed the tests. The study period was from April 1999 to September The study was approved by the Ethics Committee of the University Hospital, Linköping, Sweden Interventions In the study group standard non-pulsative cardiopulmonary bypass (CPB) technique with membrane oxygenators, roller pumps, moderate hypothermia ( C) and normocapnia was used. General anesthesia was administered using fentanyl, thiopental or midazolam and isoflurane [1]. In the control patients coronary intervention was performed using standard angiography and PCI procedures [12]. The procedure was carried out under local anesthesia without sedation Neuropsychological examination (Table 1) The neuropsychological test battery consisted of tests covering cognitive domains that have shown to be affected after cardiac surgery such as verbal and visual memory, psychomotor speed, attention and concentration [13]. In addition a set of computerized tests considered important when assessing the ability to drive was included [14]. Testing and scoring were performed by two research nurses, blinded to the results of the driving tests, with special training in cognitive function measurements and supervised by an experienced neuropsychologist (A.L.). The test conditions were standardized and external distraction avoided. Any patient showing a drop of more than one (pre-intervention) standard deviation after intervention was considered to have deterioration for that test variable. A cognitive decline after intervention was defined as deterioration in at least two test variables in the neuropsychological test battery [15]. The evaluation of neuropsychological test results was done in collaboration with the neuropsychologist (A.L.) On-road driving The on-road evaluation was based on standard procedures used by the Swedish National Road Administration (SNRA) [17]. The route (25 km) was selected to involve a variety of driving situations and driving was done in actual traffic in a rented car. A certified driving inspector blinded to patient group, driving simulator results and results of the cognitive tests, performed the evaluation, which covered five specific areas: Speed, maneuvering, lateral position, traffic behavior and attention. Speed was evaluated in relation to requirements at that time. Maneuvering involved the handling and control of the vehicle, for example steering and braking. Lateral position examined car positioning in the road lane, roundabouts, and intersections. Attention concerned traffic

3 336 E. Ahlgren et al. / European Journal of Cardio-thoracic Surgery 23 (2003) Table 1 Neuropsychological tests Paper and pen tests Visual memory, psychomotor speed, attention and concentration. Standard procedures and scoring were followed Lezak [16] Trail making part A and B Psychomotor function, attention and mental flexibility. The time to complete the test is measured (s). A short time reflecting a better result Rey Complex Figure Test Visual memory. Reproduction and positioning of geometrical figures, recall after 10 min. Score ranges from 0 (worst) to 36 (best) Rey Auditory Verbal Learning Verbal learning and short-term memory. Standard procedures and scoring were followed Lezak [16] Test Total learning The sum of words recalled from a read list of 15 words repeated five times Early recall The number of words recalled immediately after distraction by another list of words Delayed recall The number of words recalled after 30 min Recognition The number of words recognized from the original list of 15 words among another read list of 50 words Computerized tests (T-scores) a Tests considered important assessing the ability to drive. Procedures and scoring were followed Levander [14] K-test Focused attention. Decision as quickly as possible and with a minimum of errors whether the letter k is present or not among a set of distracters on the screen Simple reaction time Push a colored key on the keyboard as soon as a visual stimulus appears on the computer screen Reaction time on two choice Push a colored key on the keyboard on the same side as the stimulus visual stimuli Complex reaction time Push a colored key on the keyboard on the same side as the stimulus but do not push the key if a concurrent auditory signal is present Simultaneous capacity Divided attention. Identify three consecutive odd digits in a continuous stream of digits presented one by one in the center of the screen and simultaneously respond to messages in the upper part of the screen a T-score is an overall performance measure based on speed and accuracy in K-test and Reaction time tests. In Simultaneous capacity the T-score was calculated from the mean of the results of the two simultaneously occurring tasks. A high T-score reflects a better result. signs, directions and other road users. Traffic behavior included looking ahead and adjusting to traffic rules and traffic conditions. The driving inspector rated the patients performance in each area using a rating scale ranging from 1 to 5, with steps of 0.5. A rating of 3 or above is generally considered a pass. Immediately after the driving task, the patients also rated themselves, for each of these areas using the same scale Simulator driving The Swedish Road and Transport Research Institute (VTI) advanced driving simulator, previously used in studies concerning driving behavior and cognitive demands, consists of a moving-base system, a wide-angle (1208) visual screen, a vibration-generating system, a sound-regulating system, and a temperature-regulating system [18,19]. These five systems can be controlled to operate in a way that gives the driver a realistic dynamic impression of traffic scenes. The interior of the driving simulator was a standard Volvo 850. The test route was 80 km but before the actual test the participants had a 20-km training session. The participants were instructed to drive normally. The test route, mimicking a two-lane tarmac road, consisted of long sequences of uncomplicated driving conditions combined with complex situations such as junctions, road works and unpredictable situations like a moose suddenly running out in front of the car. During the drive a mobile telephone rang and the participants answered by pushing a button on the instrument panel. The two test routes, before and after the coronary intervention, had the same degree of difficulty but the sequences of complex situations and distracting tasks were different. The moose situations were not exactly alike. The dependent measurements from the simulator driving were: Speed (km/h), lateral position (meter), reaction time (s) and time to collision (TTC) (s). TTC is the time before a following vehicle collides with a leading vehicle if the speed of the vehicles remain constant. TTC reflects safety margin in time Statistical analysis All statistical analyses were performed using SPSS for Windows version Results are given as mean values with one standard deviation (^1SD). To evaluate differences between groups and within groups Mann Whitney U and Wilcoxon signed rank tests were used, since a number of measurements were made on the ordinal scale, and few of the continuous variables met normality assumptions. Differences in absolute frequencies between groups of patients were analyzed using Pearson s chi-square test. P-values less than 0.05 were considered statistically significant. 3. Results Apart from the CABG patient with postoperative stroke, the clinical course for the patients in both the study group and control group was without any major complication. As seen in Table 2, the study and control groups were comparable as regards to baseline characteristics, except

4 E. Ahlgren et al. / European Journal of Cardio-thoracic Surgery 23 (2003) Table 2 Baseline characteristics of CABG (n ¼ 23) and PCI (n ¼ 19) patients CABG, n (%) PCI, n (%) Age Mean ^ SD 65.7 ^ ^ 4.5 Median (min max) 66.0 (61 72) 64.0 (57 73) Older than 65 years 12 (52) 7 (37) Hypertension on medication 9 (39) 7 (37) Normal or only slightly reduced 22 (96) 17 (89) left ventricular function Diabetes (oral medication or 4 (17) 4 (21) insulin) Peripheral vascular disease 1 (4) 2 (10) 3-Vessel coronary artery disease 14 (61)* 3 (16) Male 21 (91) 17 (89) Elementary school 11 (48) 11 (58) Senior high school 9 (39) 6 (32) Academic level 3 (13) 2 (10) Professional driver 4 (17) 3 (16) Driving every day 16 (69) 10 (53) Driving less than once a week 2 (9) 0 (0) Driving long distances (100 km 14 (61) 10 (53) or more) Driving less than 20 km 2 (9) 2 (10) Dependence on driving 19 (82) 15 (79) *Statistically significant differences (P, 0:05) between groups. that three-vessel coronary artery disease was more common in CABG patients than in PCI patients (P, 0:05) Neuropsychological examination before and 4 6 weeks after coronary artery intervention (Table 3) Prior to intervention there were no statistically significant differences in neuropsychological test scores between patients in the study group and those in the control group. However, the control patients tended to score better in TMTA, K-test and Complex reaction time and the study patients tended to score better in Rey AVLT recognition. With a few exceptions, both groups improved in the neuropsychological tests after intervention. Most notable among these improvements were the higher average post-intervention scores on Rey AVLT and Rey CFT in both the CABG and PCI group, and the higher average post-intervention scores in Complex reaction time and Simultaneous capacity in the PCI group. After intervention PCI patients scored better in TMTA and Complex reaction time than CABG patients. There were no differences in the test results related to education level. More patients in the CABG group (n ¼ 11, 48%) than in the PCI group (n ¼ 2, 10%) showed a cognitive decline after intervention (P, 0:01). Deterioration in test scores was most frequently seen in TMTA, TMTB, Rey AVLT (recognition), K-test, Simple reaction time and Reaction time on two choice visual stimuli On-road driving before and 4 6 weeks after coronary artery intervention (Table 4) Before intervention there were no statistically significant differences in driving scores between patients in the study and control group. After intervention CABG patients tended to deteriorate in traffic behavior (P ¼ 0:01) and in attention (P ¼ 0:04), while PCI patients tended to deteriorated in maneuvering (P ¼ 0:04). There were no differences in driving scores related to education level. Patients in both groups rated themselves about one point higher (range: ) than did the driving inspector in all five areas, both before and after the intervention (P, 0:001). Further analysis revealed that patients with a cognitive decline after intervention deteriorated in on-road driving to a greater extent than did patients without a cognitive decline (Table 5). Table 3 Neuropsychological test scores. Mean (SD) before and 4 6 weeks after CABG (n ¼ 23) and PCI (n ¼ 19) Tests a Before intervention After intervention CABG PCI P CABG PCI P TMTA (s) 47.3 (17.8) 38.8 (14.6) (23.7) 41.0 (19.7) TMTB (s) (56.7) (57.0) (60.1) (62.0) Rey CFT (0 36) 20.4 (5.9) 19.7 (6.2) (6.0) 22.1 (6.5) Rey AVLT (TL) 36.4 (9.8) 37.7 (10.0) (11.6) 42.1 (9.9) Rey AVLT (Early recall) 6.6 (2.6) 7.7 (2.2) (3.5) 7.9 (2.7) Rey AVLT (Late recall) 6.8 (3.3) 7.1 (2.0) (3.5) 7.5 (2.6) Rey AVLT (Recognition) 13.1 (2.1) 11.8 (3.0) (1.7) 13.7 (1.4) K-test, T-score 45.2 (6.3) 48.7 (6.9) (8.7) 48.1 (9.6) Reaction time, Simple, T-score 50.1 (11.7) 49.0 (16.8) (12.9) 46.5 (12.1) Reaction time, Two-choice, 39.1 (15.6) 42.7 (11.3) (11.5) 43.4 (7.8) T-score Reaction time, complex, T-score 28.4 (17.0) 38.7 (14.0) (14.0) 45.2 (8.8) Simultaneous capacity, T-score 32.4 (15.4) 33.8 (15.2) (16.4) 43.7 (12.5) a TMTA, TMTB (s): A short time reflects a better result. T-score in the computerized tests is an overall performance measure. A high score reflects a better result.

5 338 E. Ahlgren et al. / European Journal of Cardio-thoracic Surgery 23 (2003) Table 4 On-road driving scores before and 4 6 weeks after CABG (n ¼ 23) and PCI (n ¼ 19), mean (SD) Before intervention After intervention CABG PCI P CABG PCI P Speed 3.0 (0.9) 3.2 (0.7) (0.8) 3.0 (0.8) Maneuvering 3.3 (0.8) 3.4 (0.5) (0.9) 3.2 (0.8)* Lateral position 2.9 (0.6) 3.0 (0.7) (0.9) 2.7 (0.8) Traffic behavior 3.0 (0.9) 2.9 (0.8) (0.9)* 2.9 (0.9) Attention 2.9 (0.8) 3.1 (0.8) (0.9)* 3.0 (0.8) *Statistically significant differences (P, 0:05) within groups before and after intervention Simulator driving before and 4 6 weeks after coronary artery intervention (Table 6) Before the intervention, control patients drove faster than study patients in both uncomplicated sections as well as unpredictable situations. After surgery the study patients had increased their speed and there were no longer any differences between the groups. Furthermore, no differences in reaction times were seen between and/or within the groups before and/or after coronary artery intervention. 4. Discussion Table 5 Number of patients with a drop in on-road driving score among patients with and without a cognitive decline after intervention Patients with a cognitive decline (n ¼ 13), n (%) Patients without a cognitive decline (n ¼ 29), n (%) Speed 11 (85) 9 (31) Maneuvering 6 (46) 11 (38) Lateral position 11 (85) 11 (38) Traffic behavior 11 (85) 14 (48) Attention 9 (69) 11 (38) P The incidence of postoperative cognitive decline after cardiac surgery in this study is similar or somewhat higher than in previous studies [3,15]. The main findings of this investigation were that CABG patients showed a cognitive decline after intervention to a greater extent than did PCI patients, 48 versus 10%, and that the patients with a cognitive decline after intervention deteriorated in their driving performance to a greater extent than the patients without a cognitive decline. Newman and coworkers reported in a recent study that there appears to be a biphasic course in cognitive change after cardiac surgery. After an immediate postoperative decline in cognitive function in 53% of the patients at discharge, the patients improved and after 6 weeks and 6 months 36 and 24%, respectively, still had cognitive impairment. However, after 5 years 42% of the patients performed below their baseline levels [3]. In the present study, neuropsychological test scores at group level showed unchanged or improved test results after surgery. This is a common finding and is explained by the pronounced effect of practice in testing which caused the overall group performance to improve after the operation [20]. Accordingly, when the postoperative mean is compared with the preoperative mean the decline in cognitive function of some individuals is overshadowed by the improvements in others. In contrast, PCI patients improved more than CABG patients in Complex reaction time and in Simultaneous capacity after intervention and this finding may indicate a cognitive deterioration in reaction time and divided attention after CABG. Since the ability to drive a car requires a set of cognitive complex skills and the fact that even subtle neuropsychological deficits are of importance for driving performance, several studies have investigated driving performance in patients with medical conditions affecting cognitive function [18,19]. To our knowledge driving performance after cardiac surgery has not previously been studied. In a review Blumenthal et al. emphasized the importance of further research in this particular field [21]. In the present study patients in both groups tended to deteriorate in all areas of the on-road driving test after intervention. The major changes in the CABG group were in traffic behavior and attention, and in the PCI group in maneuvering. We have no obvious explanation of these results but it is noteworthy that CABG patients deteriorated in more complex and more cognitive demanding areas of the on-road driving test. Also, the deterioration in driving performance appeared to be mostly confined to the patients older than 65 although due to the small numbers of patients this finding must be regarded as tentative. Previous studies have shown that elderly drivers have difficulties at intersections and in roundabouts and are also more often than younger drivers involved in traffic accidents in these complex traffic situations [22]. Different models of driving behavior have been used to describe the driving process and one of the most cited is Michon s three-level hierarchic model [23]. Decisions on the strategic level concerns planning safe driving, taking into account weather, time and the personal condition and is generally made before actual driving. In real traffic, cognitive processing and decisions are made at the tactical level such as judgment of traffic situations and adaptation of

6 E. Ahlgren et al. / European Journal of Cardio-thoracic Surgery 23 (2003) Table 6 Simulator driving data, mean (SD) before and after CABG (n ¼ 17) and PCI (n ¼ 17) a Before intervention After intervention CABG PCI P CABG PCI P Uncomplicated driving Speed (km/h) 77.8 (5.8) 82.1 (5.7) (7.9)* 83.4 (5.7) Lateral position (meter) 1.9 (1.1) 1.8 (0.1) (0.2)* 1.9 (0.1) Unpredictable situations Speed, distracting message 55.7 (7.6) 61.6 (5.4) (7.9)* 62.1 (5.2) Lateral position, distracting 1.5 (0.3) 1.4 (0.3) (0.3) 1.4 (0.2) message TTC (s) A parked car behind a curve 4.1 (1.4) 4.2 (1.5) (1.7) 3.9 (1.5) Unpredictable situations, reaction time (s) Telephone call, answer 2.7 (1.1) 2.3 (0.7) (0.8) 2.5 (0.7) Moose 1.0 (0.2) 1.0 (0.4) (0.2) 1.5 (0.2) Patients who manage to brake, n (%) 10 (59) 10 (59) 15 (88) 17 (100) a TTC, time to collision; lateral position, distance from the road central line; reaction time, the time from the first appearance of the moose to start braking and the time from the onset of the ring signal to pushing the button of the panel. Patients who manage to brake, those who manage to brake and avoid collision. Moose situation 1 was not exactly like moose situation 2. *Statistically significant differences (P, 0:05) within groups before and after intervention. speed and distance. Attention combined with speed of information processing makes it possible to select from several possible solutions. The operational level consists of elementary driving tasks based on automated, over-learned perceptual-motor functions such as steering, accelerating, shifting and braking. Nine of 11 CABG patients with a significant postoperative cognitive decline deteriorated in some areas of the on-road driving test such as speed adjustment to current traffic situations, positioning of the car in the road lane and in traffic behavior including looking ahead and adjusting to traffic rules and traffic conditions, i.e. tactical level. This may indicate that cognitive functions important for safe driving may be influenced after cardiac surgery, at a time when most of the patients probably resume driving after their heart operation. The finding that deterioration in maneuvering was seen in the control group was unexpected. Focal neurological deficits after PCI are rare and angioplasty has not been associated with short-term cognitive impairment but data are sparse [24]. The driving scores before intervention in both groups were unexpectedly low when compared with scores for a healthy control group of the same age in another study using the same test route and evaluation criteria [19]. This may indicate that widespread atherosclerotic disease itself has an impact on cognitive functions and driving ability. There was a great discrepancy between the self-rating of the patients in both groups and how the driving inspector evaluated their driving ability in the on-road driving test both before and after the intervention. Other studies have reported similar data and most people tend to overestimate their own driving skill and safety [25]. This may not be so important if driving performance is at a high level but in this case it seems that the patients were not fully aware of the deficits in their driving performance which may increase the risk for unsafe driving and motivation to take compensatory action. Driving performance in the simulator in both groups appeared largely unaffected after the intervention. The absence of postoperative deterioration in the driving simulator test may be explained by compensatory behavior with very careful driving in this new, insecure driving situation [8,18]. The design of the simulator test route was a country road with low-density traffic including complex sections as well as unpredictable situations in order to reveal changes in driving performance at the tactical level. The drawback of creating more complex situations in the simulator are the problem of nausea, which increases. Patients would also be expected to drive even more carefully to compensate for the increased complexity tending to make simulator driving less realistic [8]. The on-road driving test, which involves both urban and rural areas and contains more complex driving situations, seems sensitive in detecting changes in driving performance [18,19]. There may be a risk for judgment bias by the inspector but the driving route and evaluation criteria were standardized and used in previous studies of driving performance in other patient groups [17 19]. Anxiety and tiredness of the patient and variationintraffic density, weather and road conditions may also have affected performance but the conditions were similar for both groups.

7 340 E. Ahlgren et al. / European Journal of Cardio-thoracic Surgery 23 (2003) One limitation of the study is the small number of patients included. As the test procedures in this study were both extensive and costly, study size had to be limited. Treatments (CABG or PCI) were not randomly assigned and although care was taken to match the two groups with respect to age, gender, education and driving experience, a systematic difference between the two groups cannot be ruled out. More patients in the CABG group had threevessel coronary artery disease but the two groups were similar with respect to risk factors for cerebrovascular disease such as hypertension, diabetes, peripheral vascular disease as well as baseline neurocognitive test score and driving behavior. In conclusion, data from this study indicate that patients with coronary artery disease to a larger extent suffer a decline in cognitive function after surgery with cardiopulmonary bypass than after percutaneous coronary intervention in local anesthesia. Patients with a cognitive decline also tend to be the same patients who show deterioration in driving performance after intervention. Further research on the impact of cardiac surgery on neurocognitive function and driving performance seems warranted. Acknowledgements This work was supported by the Swedish National Road Administration (SNRA). References [1] Ahlgren E, Aren C. Cerebral complications after coronary artery bypass and heart valve surgery: risk factors and onset of symptoms. J Cardiothorac Vasc Anesth 1998;12: [2] Roach GW, Kanchuger M, Mangano CM, Newman M, Nussmeier N, Wolman R, Aggarwal A, Marschall K, Graham SH, Ley C. Adverse cerebral outcomes after coronary bypass surgery. 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