Alterations of neuropsychological function and cerebral glucose metabolism after cardiac surgery are not related only to intraoperative microembolic events

Clinical Impact of the Microembolic Signal Burden During Catheter Ablation for Atrial Fibrillation: Just a Lot of Noise?

OBJECTIVES

Microembolic signal detection by transcranial Doppler ultrasonography may be considered a surrogate for cerebral events during invasive cardiac procedures. However, the impact of the microembolic signal count during pulmonary vein isolation on the clinical outcome is not well evaluated. We investigated the effect of the microembolic signal count on the occurrence of new silent cerebral embolism measured by diffusion-weighted imaging (DWI)-magnetic resonance imaging (MRI), changes in neuropsychological testing, and the occurrence of clinical events during long-term follow-up after pulmonary vein isolation.

METHODS

Pulmonary vein isolation was performed in 41 patients. The total microembolic signal burden (classified into "solid," "gaseous," and "equivocal") and sustained thromboembolic showers of greater than 30 seconds were recorded. Diffusion-weighted imaging-MRI and neuropsychological testing were performed before and after pulmonary vein isolation to assess for silent cerebral embolism and neuropsychological sequelae. Long-term follow-up was performed by telephone to assess for stroke/transient ischemic attack.

RESULTS

A total of 68,729 microembolic signals (14,893 solid, 11,909 gaseous, and 41,927 equivocal) with an average of 1676 signals per patient and 42 thromboembolic showers were recorded. No correlation between the microembolic signal/thromboembolic shower count and the occurrence of new DWI lesions or neuropsychological capability was found. After a mean follow-up ± SD of 49 ± 4 months, 1 patient had an overt transient ischemic event, which was not associated with a high microembolic signal count.

CONCLUSIONS

In this multicenter study, we found no impact of the intraprocedural microembolic symbol/thromboembolic shower count on the occurrence of new DWI lesions, neuropsychological capability, or overt neurologic deficits after pulmonary vein isolation. Thus, not only the microembolic signal count but also procedural/individual factors may contribute to commensurable clinical damage, which may challenge this method as a valid biomarker during pulmonary vein isolation.

Intra-arterial oxidative stress correlates negatively with cognitive function and positively with postoperative ischemic lesions in carotid artery stenosis stenting

BACKGROUND AND PURPOSE

Carotid plaque contains biologically active substances released into the blood during carotid artery stenting (CAS). The main purpose of this prospective study was to analyse sequential changes in oxidative stress during CAS and their relationship to clinical factors.

METHODS

Twenty-two consecutive CAS procedures were performed between May 2014 and April 2016. Arterial blood was collected four times: (1) after the sheath insertion without edaravone; (2) pre-angioplasty with edaravone from the carotid artery; (3) after post-stenting angioplasty from an occluded carotid artery; and (4) before sheath removal. Derivatives of reactive oxygen metabolites (d-ROMs) and biological antioxidant potential (BAP) were measured photometrically. The relationship between d-ROMs or BAP and preoperatively investigated biochemical parameters, cognitive function, and number of diffusion-weighted image (DWI) high spot lesions was analysed using one-way ANOVA and the Tukey-Kramer HSD test.

RESULTS

The d-ROM values for CAS were 355±58.8 Carratelli Units at sheath insertion, 315±57.2 after edaravone infusion, 328±56.8 after post-stenting angioplasty, and 315±53.0 just before sheath removal. The d-ROM values were reduced significantly after edaravone infusion (P<0.05). The BAP at sheath insertion was reduced significantly according to age (P<0.05). The d-ROMs at sheath insertion correlated negatively with the dementia scale and positively with the post-CAS DWI high spots (1.00±1.07; P<0.05). Other biochemical parameters did not correlate with the d-ROM values or BAP.

CONCLUSION

Oxidative stress is correlated negatively with cognitive function and positively with postoperative ischemic lesions. Antioxidant potential decreases with ageing.

Intraoperative Embolization and Cognitive Decline After Cardiac Surgery

Since the advent of cardiac surgery, complications have existed in many forms. Recent work has focused on the safety of current cardiac surgery with particular emphasis on cognitive outcomes. Cardiopulmonary bypass has improved the safety of operative practice; however, increasing concern surrounds the measurable and immeasurable impact embolization has on the brain. New ischemic lesions have been associated with distant emboli, which intraoperatively enter the cardiovascular system. This has prompted better characterization of the nature of emboli manifesting as cognitive impairment postoperatively. The difficulty in attributing causation relates to the subclinical damage that does not necessarily manifest as clinical stroke. Transcranial Doppler has become an important tool in documenting cerebral emboli during surgery. The purpose of this systematic review is to focus on the current literature to improve our understanding of the impact embolization has on the brain. We also aim to investigate which cardiac interventions hold the greatest burden of embolic load and how previous literature has investigated the impact of emboli on cognition by monitoring emboli during specific cardiac interventions. Significant intraoperative factors such as the cardiopulmonary bypass machine and surgical interventions have been highlighted to summarize the current literature associating cerebral embolization with these factors and postoperative cognitive outcomes. The findings of this review report that the current literature is divided as to whether the impact of embolization during cardiac surgery has any adverse impact on cognition. This review highlights that the ultimate goal of improving cognitive safety will involve further careful consideration of multifactorial events.

Relationship between exercise-induced heart rate increase and the formation of microbubbles and high-intensity transient signals in mechanical heart valve implanted patients

INTRODUCTION

The formation and collapse of vapor-filled bubbles near a mechanical heart valve is called cavitation. Microbubbles can be detected in vivo by doppler ultrasonography (USG) as HITS (high intensity transient signals) in cranial circulation. We investigated the relationship between exercise induced heart rate increase and HITS formation in cranial circulation.

MATERIAL AND METHODS

Thirty-nine mechanical heart valve implanted (8 aortic valve replacement (AVR) + mitral valve replacement (MVR), 9 AVR, 22 MVR) patients aged 18-80 years old were included in our study. Microbubbles were counted in the left ventricular cavity via transthoracic echocardiography at rest per cardiac cycle. Afterwards transcranial Doppler USG was performed and HITS were counted in each patient's middle cerebral artery at 5 min duration. Subsequently an exercise test according to the Bruce protocol was performed. After achieving maximal heart rate, microbubbles in the left ventricle and HITS were counted again.

RESULTS

Microbubbles in the left ventricle and transcranial HITS increased after exercise significantly compared to resting values (15.79 ±10.91 microbubbles/beat vs. 26.51 ±18.00 microbubbles/beat, p < 0.001; 6.13 ±8.07 HITS/5 min vs. 13.15 ±15.87 HITS/5 min, p = 0.001). There was a significant correlation between microbubbles and HITS counts after peak exercise (r = 0.55, p < 0.001).

CONCLUSIONS

In our study, we found that the microbubbles were increasing as the heart rate increased and more HITS were propelled to the cerebral circulation. As previously shown, HITS can alter cognitive functions. Therefore heart rate control is essential in mechanical heart valve patients to protect neurocognitive functions.

Cognitive dysfunction after on-pump operations: neuropsychological characteristics and optimal core battery of tests

Postoperative cognitive dysfunction (POCD) is a mild form of perioperative ischemic brain injury, which emerges as memory decline, decreased attention, and decreased concentration during several months, or even years, after surgery. Here we present results of our three neuropsychological studies, which overall included 145 patients after on-pump operations. We found that the auditory memory span test (digit span) was more effective as a tool for registration of POCD, in comparison with the word-list learning and story-learning tests. Nonverbal memory or visuoconstruction tests were sensitive to POCD in patients after intraoperative opening of cardiac chambers with increased cerebral air embolism. Psychomotor speed tests (digit symbol, or TMT A) registered POCD, which was characteristic for elderly atherosclerotic patients. Finally, we observed that there were significant effects of the order of position of a test on the performance on this test. For example, the postoperative performance on the core tests (digit span and digit symbol) showed minimal impairment when either of these tests was administered at the beginning of testing. Overall, our data shows that the selection of tests, and the order of which these tests are administered, may considerably influence the results of studies of POCD.

A pilot study evaluating presurgery neuroanatomical biomarkers for postoperative cognitive decline after total knee arthroplasty in older adults

BACKGROUND

Total knee arthroplasty improves quality of life but is associated with postoperative cognitive dysfunction in older adults. This prospective longitudinal pilot study with a parallel control group tested the hypotheses that (1) nondemented adults would exhibit primary memory and executive difficulties after total knee arthroplasty, and (2) reduced preoperative hippocampus/entorhinal volume would predict postoperative memory change, whereas preoperative leukoaraiosis and lacunae volumes would predict postoperative executive dysfunction.

METHODS

Surgery (n = 40) and age-education-matched controls with osteoarthritis (n = 15) completed pre- and postoperative (3 weeks, 3 months, and 1 yr) memory and cognitive testing. Hypothesized brain regions of interest were measured in patients completing preoperative magnetic resonance scans (surgery, n = 31; control, n = 12). Analyses used reliable change methods to identify the frequency of cognitive change at each time point.

RESULTS

The incidence of postoperative memory difficulties was shown with delay test indices (i.e., story memory test: 3 weeks = 17%, 3 months = 25%, 1 yr = 9%). Postoperative executive difficulty with measures of inhibitory function (i.e., Stroop Color Word: 3 weeks = 21%, 3 months = 22%, 1 yr = 9%). Hierarchical regression analysis assessing the predictive interaction of group (surgery, control) and preoperative neuroanatomical structures on decline showed that greater preoperative volumes of leukoaraiosis/lacunae were significantly contributed to postoperative executive (inhibitory) declines.

CONCLUSIONS

This pilot study suggests that executive and memory declines occur in nondemented adults undergoing orthopedic surgery. Severity of preoperative cerebrovascular disease may be relevant for understanding executive decline, in particular.

Sizing gaseous emboli using Doppler embolic signal intensity

Extension of transcranial Doppler embolus detection to estimation of bubble size has historically been hindered by difficulties in applying scattering theory to the interpretation of clinical data. This article presents a simplified approach to the sizing of air emboli based on analysis of Doppler embolic signal intensity, by using an approximation to the full scattering theory that can be solved to estimate embolus size. Tests using simulated emboli show that our algorithm is theoretically capable of sizing 90% of "emboli" to within 10% of their true radius. In vitro tests show that 69% of emboli can be sized to within 20% of their true value under ideal conditions, which reduces to 30% of emboli if the beam and vessel are severely misaligned. Our results demonstrate that estimation of bubble size during clinical monitoring could be used to distinguish benign microbubbles from potentially harmful macrobubbles during intraoperative clinical monitoring.

The role of asymmetry and the nature of microembolization in cognitive decline after heart valve surgery: a pilot study

Our objective was to determine the role of asymmetry and the nature of microembolization on postoperative cognitive decline in patients who had undergone heart valve surgery. Continuous transcranial Doppler ultrasound was intraoperatively used for both middle cerebral arteries in 13 right-handed heart valve surgery patients to detect microembolization. The Trail Making Test A and B, Memory with 10/30 s interference, the Digit Span Test and Phonemic Fluency were performed preoperatively, at discharge and three months after surgery. Our data suggest that early and late postoperative psychomotor and executive functions may be sensitive to microemboli in the left, but not in the right middle cerebral artery. Moreover, solid and gaseous microemboli are both similarly associated with early postoperative cognitive decline while, surprisingly, late postoperative cognitive decline is more likely to be associated with gaseous than solid microemboli.

Electroencephalography as a tool for assessment of brain ischemic alterations after open heart operations

Cardiac surgery is commonly associated with brain ischemia. Few studies addressed brain electric activity changes after on-pump operations. Eyes closed EEG was performed in 22 patients (mean age: 45.2 ± 11.2) before and two weeks after valve replacement. Spouses of patients were invited to participate as controls. Generalized increase of beta power most prominent in beta-1 band was an unambiguous pathological sign of postoperative cortex dysfunction, probably, manifesting due to gamma-activity slowing (“beta buzz” symptom). Generalized postoperative increase of delta-1 mean frequency along with increase of slow-wave activity in right posterior region may be hypothesized to be a consequence of intraoperative ischemia as well. At the same time, significant changes of alpha activity were observed in both patient and control groups, and, therefore, may be considered as physiological. Unexpectedly, controls showed prominent increase of electric activity in left temporal region whereas patients were deficient in left hemisphere activity in comparison with controls at postoperative followup. Further research is needed in order to determine the true neurological meaning of the EEG findings after on-pump operations.

The effect of carbon dioxide insufflation on cognitive function during cardiac surgery

The use of carbon dioxide (CO(2)) insufflation into the pericardial well has become widespread, and in some units routine. The rationale behind this practice is the fact that CO(2) is more soluble than air leading to fewer gaseous microemboli entering the bloodstream and being transferred to the brain or heart. However, the evidence that this reduces postoperative neurocognitive decline is scant. Although CO(2) insufflation is generally a safe procedure there are case reports of significant complications. The aim of this systematic review is to analyze the current evidence for this practice.

Antithrombin-heparin covalent complex reduces microemboli during cardiopulmonary bypass in a pig model

Transcranial Doppler-detected high-intensity transient signals (HITS) during cardiopulmonary bypass (CPB) surgery have been associated with postoperative neurocognitive dysfunction, suggesting microemboli in the brain could be a contributing factor. HITS occur despite administration of unfractionated heparin (UFH). This study was done to determine whether antithrombin-heparin covalent complex (ATH), a more potent anticoagulant than heparin, can reduce HITS during CPB. In a pig CPB model, ATH, UFH, or UFH + antithrombin (AT) was intravenously administered to female Yorkshire pigs after sternotomy. Twenty minutes later, hypothermic CPB was initiated and continued for 1.25 hours, then normothermia was re-established for 45 minutes. Protamine sulfate was given to neutralize the anticoagulants, and pigs were allowed to recover. HITS were monitored using an arterial flow probe placed over the carotid artery. Compared with UFH (300 or 1000 U/kg), ATH reduced the number of HITS during CPB in a dose-dependent manner. AT (3 mg/kg) + UFH (300 U/kg) resulted in an intermediate HITS rate between UFH and ATH (2 mg/kg in terms of AT). Examination of brain sections for emboli formation confirmed that, similar to HITS, number of thrombi decreased in direct proportion to ATH dosage. These results support the hypotheses that the majority of HITS represent thromboemboli and that ATH reduces emboli formation during CPB.

Intraoperative cerebral high-intensity transient signals and postoperative cognitive function: a systematic review

BACKGROUND

Much attention in the literature has focused on the relationship between perioperative microemboli during cardiac and vascular surgery and postoperative cognitive decline. Transcranial Doppler ultrasonography (TCD) has been used to measure high-intensity transient signals (HITS), which represent microemboli during cardiac, vascular, and orthopedic surgery. The purpose of this study was to systematically examine the literature with respect to HITS and postoperative cognitive function.

METHODS

Systematic PubMed searches identified articles related to the use of TCD and cognitive function in the surgical setting.

RESULTS

The literature remains largely undecided on the role of HITS and cognitive impairment after surgery, with most studies being underpowered to show a relationship. Although the cognitive effects of HITS may be difficult to detect, subclinical microemboli present potential harm, which may be modifiable.

CONCLUSIONS

TCD represents a tool for intraoperative cerebral monitoring to reduce the number of HITS during surgery.

Cerebral dysfunction after cardiac surgery--are we moving forward?

This review focuses on the effects of cardiac surgery and cardiopulmonary bypass on the brain, with special emphasis on the results of recently conducted studies. The incidence of postoperative neurological and neuropsychological deficits and risk factors for cerebral injury are reviewed. The relationships between cerebral embolic load, release of biochemical markers of brain injury and cognitive dysfunction after cardiac surgery are also reviewed. Finally, recently gained information on the management of cardiopulmonary bypass is discussed, along with the results of recent pharmacological neuroprotective trials in patients undergoing cardiac surgery.

Reversal of flow during carotid artery stenting: use of the Parodi antiembolism system

INTRODUCTION

To evaluate the flow reversal efficacy of the Parodi antiembolism system (PAES) in the prevention of distal emboli during carotid stenting.

METHODS

A total of 90 patients were treated for internal carotid artery (ICA) stenosis with a stent device. A PAES device was used in 31 symptomatic and 5 asymptomatic patients (total 36 patients) with ICA stenosis, and 54 patients were stented without any protection device. Diffusion-weighted (DW) imaging was performed before and after stenting.

RESULTS

In the group without PAES protection, 23 out of 54 patients showed new lesions on DW images after stenting. Of the lesions seen, 147 (2.72 lesions/patient) were in the vessel-dependent area. In the group with protection, 19 out of 36 patients had new lesions, and only 34 (0.94 lesions/patient) were noted in the vessel-dependent area. The number of new lesions in the nondependent vessel area did not differ if a protection system was used (P = 0.671). The use of PAES led to a significant reduction (P = 0.024) in the incidence of the most frequently seen lesions (size <2 mm). The stroke death rate was 3.3% overall, 3.7% in the group without protection device, and 2.7% in the PAES group. There were no permanent neurological deficits after 3 months.

CONCLUSION

The PAES is a safe and effective tool to reduce the incidence of embolic complications during carotid stenting. Older patients and patients with higher grade stenosis seem to profit more.

Prevention of Ischemic Neurologic Injury With Intraoperative Monitoring of Selected Cardiovascular and Cerebrovascular Procedures: Roles of Electroencephalography, Somatosensory Evoked Potentials, Transcranial Doppler, and Near-Infrared Spectroscopy

All neuromonitoring techniques, although imperfect, provide useful information for monitoring cardiothoracic and carotid vascular operations. They may be viewed as providing complementary information, which may help surgical technique and, as a result, possibly improve clinical outcomes. As of this writing, the efficacy of TCD and NIRS monitoring during cardiothoracic and vascular surgery cannot be considered established. Well designed, prospective, adequately powered, double-blind, and randomized outcome studies are needed to determine the optimal neurologic monitoring modality (or modalities), in specific surgical settings.

The influence of cranioplasty on postural blood flow regulation, cerebrovascular reserve capacity, and cerebral glucose metabolism

The indications for cranioplasty after decompressive craniectomy are cosmetic repair and, mainly, restoration of cerebral protection. Although neurological improvement after cranioplasty is repeatedly noted, the reasons for this still remain unclear. Few observations concerning the impact of CSF hydrodynamic and/or atmospheric pressure were published during the last decades. Relevant data concerning the cerebrovascular reserve capacity and cerebral glucose metabolism before and after cranioplasty have been lacking until now. To gain further insight, the present study was undertaken to investigate the impact of cranioplasty on indices of cerebral blood flow regulation and metabolism. Thirteen patients in whom extensive craniectomies had been performed underwent a meticulous study of blood flow velocities in the middle cerebral artery (MCA) and extracranial internal carotid artery (ICA), as assessed by transcranial Doppler (TCD) ultrasonography during postural maneuvers (supine and sitting positions) and during stimulation with 1 g of acetazolamide for the interpretation of cerebrovascular reserve (CVR) capacity. Twelve patients underwent 18-fluorodesoxyglucose positron emission tomography. These measurements were made before and 7 days after cranioplasty. Cranioplasty improved preoperative differences in MCA blood flow velocities when comparing the injured with the noninjured hemisphere. Similarly, cranioplasty resolved decreases in extracranial ICA blood flow in the injured hemisphere that were induced by postural changes, which was a constant finding prior to this procedure. More strikingly, however, the CVR capacity, which was severely impaired in both hemispheres, significantly increased after the procedure. Metabolic deficits, which were observed in the injured as compared with the noninjured hemisphere, were found to improve after reimplantation of the skull bone flap. Cranioplasty appears to affect postural blood flow regulation, CVR capacity, and cerebral glucose metabolism markedly. Thus, early cranioplasty is warranted to facilitate rehabilitation in patients after decompressive craniectomy.

Asymmetric Cerebral Embolic Load and Postoperative Cognitive Dysfunction in Cardiac Surgery

BACKGROUND

The aim of the study was to determine the effects of asymmetric cerebral embolic load on cognitive functions.

METHODS

Thirty-six open heart surgery (OH) and 26 coronary artery bypass grafting (CABG) patients were evaluated by neuropsychological and transcranial Doppler tests.

RESULTS

OH was associated with a significantly larger microembolic load in comparison to CABG. In OH patients, the microembolic load at the left middle cerebral artery correlated with a verbal memory decline, whereas the microembolic load at the right middle cerebral artery correlated with a nonverbal memory deficit. CABG patients also showed a postoperative verbal memory decline which correlated with cardiopulmonary bypass length but not with microembolic load.

CONCLUSION

Massive microembolic load during OH induces specific cognitive impairment in accordance to the brain region to which they are delivered. In atherosclerotic patients, the left temporal region is especially prone to perioperative ischemia.

Cognitive changes after carotid artery stenting

INTRODUCTION

We aimed to test changes in cognitive performance after carotid artery stenting (CAS).

METHOD

Ten patients were neuropsychologically tested at least 24 h before and 48 h after CAS. To diminish thromboembolic events, we used a proximal protection device. The following neuropsychological tests were selected: The Mini Mental State Examination (MMSE), symbol digit test and subtests of the Consortium to Establish a Registry for Alzheimer's Disease (CERAD) battery (verbal fluency, constructional practice, word list memory and delayed recall). Affective state was determined by the Beck Depression Score (BDS).

RESULTS

No patient suffered from depression (BDS <1) or dementia (MMSE 29.9+/-1.5). Nine of the ten patients (P=0.12) showed increased speed in the Number Connection Test (NCT) (corresponding to trail making test). Most patients showed better or similar results concerning delayed recall (P=0.31). No change was observed in the symbol digit test, word list memory, verbal fluency or constructional practice. Better results concerning NCT and delayed recall after carotid stenting might be due to improved brain perfusion.

CONCLUSION

After CAS, cognitive and memory performance seem to improve. Further studies with different time intervals and more refined testing, as well as perfusion-weighted imaging, are needed.

Sources of Variability in the Detection of Cerebral Emboli with Transcranial Doppler During Cardiac Surgery

OBJECTIVE

The application of intensity thresholds for embolus detection with transcranial Doppler (TCD) can exclude from analysis an unrecognized proportion of high-intensity transient signals (HITS))whose intensities are below the threshold. The lack of consistent threshold criteria between clinical trials may explain part of the discrepancy in the reported HITS counts. We investigated the effect of choosing different thresholds on the sensitivity and specificity of detecting HITS during cardiopulmonary bypass (CPB).

METHODS

Two observers independently analyzed TCD recordings from 8 patients under CPB. Doppler signals were classified as true HITS, equivocal HITS, artifacts, and Doppler speckles according to preestablished criteria. The relative intensity of Doppler signals was measured by two different methods (TCD software vs manual). Receiver Operating Characteristic curves determined the optimal threshold for each of the two intensity methods.

RESULTS

Reviewers achieved agreement in 96% of 2190 Doppler signals (kappa = 0.90). Relative intensities calculated with the TCD-software method were 3 dB (95% CI: 3.0-3.4) higher than the manual method. The optimal threshold was found at 10 dB (sensitivity: 99%; specificity: 90.8%) with the software method and at 7 dB with the manual method (sensitivity: 96%; specificity: 83%). The use of an intensity threshold 2 dB higher than the optimal increased the rejection of true HITS by 8% and 14%, respectively.

CONCLUSIONS

Using intensity thresholds higher than the optimal for embolus detection decreases HITS counts. Choosing a threshold depends on the type of method used for measuring the signal intensity. Uniform threshold criteria and comparative studies between different Doppler devices are necessary for making clinical trials more comparable.

Predictive value of asymptomatic cervical bruit for carotid artery disease in coronary artery surgery revisited

OBJECTIVE

To investigate the predictive value of asymptomatic cervical bruit for detecting internal carotid artery disease in consecutive patients undergoing coronary artery bypass grafting (CABG).

DESIGN

A prospective cohort study.

SETTING

Tertiary referral university hospitals.

PATIENTS

153 consecutive patients (mean age 57 years) undergoing CABG, without previous history of cerebrovascular events.

INTERVENTIONS

Patients underwent detailed pre-operative work-up, including coronary angiography and carotid artery duplex scanning. Internal carotid artery diameter stenosis was graded as A: normal; B: < 15%; C: 15%-50%; D: 50-80%; D+: > 80-99% and E=complete occlusion.

RESULTS

72 patients (47.1%) (95% CI: 39%, 55%) had no evidence of internal carotid artery stenosis; 81 (52.9%) (95% CI: 44.9%, 60.9%) had varying grades of disease, unilateral or bilateral. Cervical bruit was detected in 12/153 patients (7.8%) (95% CI: 3.5%, 12.1%) of whom all but one (0.7%) had varying grades of internal carotid artery disease; of these, 4 patients had bilateral cervical bruit (2.6%) (95% CI: 0.06%, 5.2%). The sensitivity, specificity, positive and negative predictive values and overall accuracy of cervical bruit for detection of > or = 50% internal carotid artery stenosis were 23.5%, 95.8%, 25%, 95.5% and 91.8%, respectively. The relative risk of > or = 50% stenosis ipsilateral to cervical bruit in 306 sides was 5.58 (95% CI: 2.0, 15.0) and the odds ratio 7.1 (95% CI: 2.0, 25.0).

CONCLUSIONS

Asymptomatic cervical bruit proved a highly specific clinical sign for detection of internal carotid artery stenosis, whether haemodynamically significant (> or = 50%) or otherwise, in patients undergoing myocardial revascularisation. This was matched by a high negative predictive value and overall accuracy for flow limiting atheroma (> or = 50% stenosis). Yet, steering carotid investigations on the basis of cervical bruit alone would result in > or = 80% internal carotid artery stenosis remaining undetected in 3% of overall patients, in whom cervical bruit is absent.

Neural correlates of cognitive dysfunction after cardiac surgery

Patients who underwent cardiac surgery and their relatives often complain on postoperative memory impairment. Most prospective neuropsychological studies also found postoperative cognitive decline early after surgery. Nevertheless, recently several reports questioned the existence of long-term brain alterations in these patient cohorts. The present review was aimed to clear up the true cardiac surgery effects on brain and cognitive functions. The reviewed data evidence that cardiac surgery interventions induce persistent localized brain ischemic lesions along with rapidly reversing global brain swelling and decreased metabolism. A range of studies showed that left temporal region was especially prone to perioperative ischemic injury, and these findings might explain persistent verbal short-term memory decline in a considerable proportion of cardiac surgery patient cohorts. Speed/time of cognitive performance is commonly decreased early after on-pump surgery either. Nevertheless, no association between psychomotor speed slowing and intraoperative embolic load was found. The rapid recovery of the latter cognitive domain might be better explained by surgery related acute global brain metabolism changes rather than ischemic injury effects. Hence, analyses of performance on separate cognitive tests rather than summarized cognitive indexes are strongly recommended for future neuropsychological studies of cardiac surgery outcomes.

Neurologic Injury Associated with CABG Surgery: Outcomes, Mechanisms, and Opportunities for Improvement

Neurologic injuries, whether subtle or overt, are a major source of morbidity secondary to coronary artery bypass graft (CABG) surgery. A comprehensive review of research in the area of neurologic injury is provided. We conclude this article by providing insight regarding areas requiring further investigation in order to reduce sustainably the risk of these iatrogenic events among patient undergoing CABG surgery.

Epidemiology of comorbid coronary artery disease and depression

This article reviews the epidemiology of comorbid coronary artery disease and unipolar depression. Both major depression and subsyndromal depressive symptoms will be considered; unless otherwise specified, the term depression will be used to designate all depressive states, including major depressive disorder, minor depression, dysthymia, and other subsyndromal forms of depression. While 17% to 27% of patients with coronary artery disease have major depression, a significantly larger percentage has subsyndromal symptoms of depression. Patients with coronary artery disease and depression have a twofold to threefold increased risk of future cardiac events compared to patients without depression, independent of baseline cardiac dysfunction. The relative risk for the development of coronary artery disease conferred by depression in patients initially free of clinical cardiac disease is approximately 1.5, independent of other known risk factors for coronary disease. In the discussion, special attention will be paid to the interactions of both gender and age with depression and coronary artery disease risk. Scrutiny of the role of confounding risk factors is presented, such as global burden of comorbid medical illness and modification of traditional risk factors, which may, in part, mediate the effect of depression on coronary artery disease.

Neurological and neuropsychological examination and outcome after use of an intra-aortic filter device during cardiac surgery

Cerebral embolization of particles after cardiac surgery is frequently associated with neurological deficits. Aortic crossclamp manipulation seems to be the most significant cause of emboli release during cardiac surgery. The goal of this study was to demonstrate whether the use of an intra-aortic filter device has an effect on the magnet resonance imaging (MRI) and functional neurological outcome. Twenty-four patients undergoing cardiosurgical procedures using cardiopulmonary bypass (CPB) were selected: coronary artery bypass graft (CABG) surgery (n = 17), aortic valve replacement (AVR) surgery (n = 4) or combined procedures (n = 3). Patients were evaluated by diffusion weighted MRI of the brain, neurological examination and neuropsychological assessment regarding alertness as well as divided and selective attention before and five to seven days after surgery. The patients were divided into two groups. In group I, 12 patients received a filter through a modified 24 F arterial cannula immediately before the aortic crossclamp was released. Filters remained in the aorta until CPB was discontinued. Intraoperatively, bilateral middle cerebral artery transcranial Doppler (TCD) was monitored at baseline, at the beginning of CPB, at a timepoint when the aorta was crossclamped, when the filter was inserted and while the crossclamp was switched to partial clamping until the CPB was discontinued. TCD was used for detection of microembolic signals (MES). The captured material in the filter was examined histologically. Twelve patients served as controls without aortic filtration (group II). The MRI of the brain did not show any diffusion alterations in either group before or after surgery. No patient developed a focal neurological deficit or stroke. Intraoperative quantitative MES detection revealed a four to tenfold increase in patients of group I compared with group II (5-6 versus 0.5-1 MES/min) during the filter dwell time. There was no consistent pattern regarding the neurobehavioural sequelae. Filters showed arteriosclerotic debris in 75% of the patients. The use of the intra-aortic filter device did not show a positive effect on neurological, neuroradiographical and neuropsychological outcomes. The increase of the MES rate in group I patients may be due to microbubbles generated as microcavitations by the filter or the aortic filter cannula. The intra-aortic filter was able to capture atheromatous material in 75% of the patients.

Vascular dementia may be the most common form of dementia in the elderly

Cerebrovascular lesions, mainly lacunes and white matter ischemia, are common in elderly patients with dementia. Vascular dementia (VaD) is the second most common cause of dementia, after Alzheimer's disease (AD). However, lacunar strokes have become an important factor in the clinical expression of AD. Also, population-based studies indicate that vascular risk factors increase the risk of developing AD. It is postulated here that the two main causes of VaD-stroke and ischemic heart disease (IHD)-may be responsible for the majority of cases of dementia in the elderly. STROKE RELATED VaD: Cerebrovascular disease (CVD) is the second leading cause of death worldwide. About 1/3 of stroke survivors [range: 25-41%] 65 years old and above develop VaD within 3 months following the ictus. In the USA alone, 125,000 new cases/year of VaD occur after ischemic stroke (about 1/3 of the 360,000 incident cases of AD). Therefore, more than 1 million elderly people are currently affected by poststroke VaD in the USA. Since current criteria identify "pure" cases of AD and VaD, it is likely that "AD plus CVD" ("mixed" dementia) could be responsible for a large number of cases currently diagnosed as probable AD. CARDIOGENIC VAD: By 2020, IHD leading to congestive heart failure (CHF) will become the leading cause of disability worldwide. Vascular cognitive impairment occurs in 26% of patients discharged from hospitals after treatment for CHF. Cognitive dysfunction correlates with left ventricular dysfunction and systolic blood pressure below 130 mm Hg. CHF is a leading cause of hospital admissions in Western nations (4.5 million cases in the USA alone) and is a growing problem in developing countries. Furthermore, over 800,000 patients/year undergo coronary artery bypass graft (CABG) surgery worldwide, including 300,000 patients in the USA. Measurable cognitive dysfunction occurs post-CABG in 80-90% of patients at hospital discharge. Long-term (5 years) incidence of cognitive defects is 42%. Finally, an international study found short-term postoperative cognitive dysfunction in 26% of patients (>60 years) after abdominal or orthopedic surgery; most of them may be instances of VaD. In conclusion, VaD may be the most underdiagnosed and undertreated form of dementia in the elderly.

Is there any impact of the shape of aortic end-hole cannula on stroke occurrence? clinical evaluation of straight and bent-tip aortic cannulae

OBJECTIVE

To compare the impact of straight and bent-tip aortic cannulae on stroke occurrence, location, and severity.

METHODS

Prospective data were collected on 8,129 patients (coronary artery bypass grafting (CABG) and/or valvular surgery). 'Bent-tip' aortic cannulae were used in 15.6% of cases and 'straight' end-hole cannulae in 84.4% of cases.

RESULTS

There were a total of 137 strokes: right anterior 52, left anterior 39, bilateral 23, posterior 18, and location not established 5. With the use of bent-tip cannulae, the incidence of strokes was 0.9% versus 1.8% with straight cannulae (chi2, p = 0.026). Bilateral and posterior strokes occurred more often with the use of straight cannulae (chi2, p = 0.015). Straight cannulae also related to the severity of strokes (chi2, p = 0.003).

CONCLUSIONS

There is an influence of the type of cannula on the occurrence, location, and severity of strokes. Straight cannulae cause significantly more often and more severe bilateral and posterior strokes than bent-tip cannulae.

Brain microembolic counts during extracorporeal circulation depend on aortic cannula position

Thrombofibrinous and gaseous brain microemboli are commonly observed during extracorporeal circulation in patients undergoing cardiac surgery. Recent studies showed a preference of microemboli to the left hemisphere. We hypothesized that placement of the aortic cannula tip within the aorta descendens rather than in the aorta ascendens as commonly used reduces the number of microemboli to the brain and also reduces the side preference. Of 60 patients undergoing elective coronary artery bypass grafting primarily randomized to either a short aortic cannula (aorta ascendens) or an elongated one (aorta descendens), 29 (16 and 13) patients had complete and technically perfect continuous intraoperative transcranial Doppler sonography with embolus detection bilaterally. The number of high-intensity transient signals (HITS) was 994 +/- 2118 (mean +/- SD) for the short cannula group and was significantly lower with the elongated cannula (223 +/- 208; p < 0.02). HITS counts per min also differed significantly in favour of the aorta descendens group (p < 0.02), but there was an overlap. Thus, elongated cannulas can reduce, but not prevent microembolism to the brain. The side-to-side ratio of microemboli revealed more events in the left hemisphere, but this was similar in both groups. This suggests that individual anatomic factors may be responsible for this hemodynamically-mediated effect.

Evaluation of neurologic assessment and outcomes in cardiac surgical patients

It is well recognized that cardiac surgery with cardiopulmonary bypass can potentially induce a wide spectrum of central nervous system (CNS) sequelae. Our awareness of the prevalence of these CNS complications is dependent on the validity of the available diagnostic methods. Current assessment methods designed to detect both focal and diffuse cerebral ischemia include neurologic examination, imaging techniques, biochemical markers, neuropsychologic assessment, and patient perceived outcomes. These techniques vary in their sensitivity and specificity, as well as feasibility for use in everyday clinical practice. There are currently only limited standardized methodologic guidelines for the assessment of CNS complications after cardiac surgery, which has resulted in considerable interstudy variability in the identification and reporting of outcomes. The application of clearly definable endpoints for reporting of CNS outcomes would be beneficial. The wealth of available data suggests that the incidence of overt CNS injury such as stroke has declined since the 1980s and is now approximately 2%, whereas evidence suggests that up to one third of cardiac surgery patients experience postoperative cognitive deficits. One of the clear strengths of the current era is the recognition of CNS injury associated with cardiac surgery, and the quest to improve our understanding of these outcomes. The application of more uniform assessment and reporting practices is surely vital to the continued advancement of cardiac surgery.

Is the number of microembolic signals related to neurologic outcome in coronary bypass surgery?

Coronary artery bypass surgery (CABG) without cardiopulmonary bypass (CPB) may potentially reduce the number of microembolic signals (MES) associated with aortic manipulation or generated by the pump circuit, resulting in a better neurologic outcome after surgery. Our aim was to compare the frequency of MES and neurologic complications in CABG with and without CPB. Twenty patients eligible to routine CABG without CPB were randomized to surgery with CPB and without CPB and continuously monitored by transcranial Doppler. Neurologic examination was performed in all patients before and after surgery. The two groups were similar with respect to demographics, risk factors, grade of aortic atheromatous disease and number of grafts. The frequency of MES in the nonCPB group was considerably lower than in CPB patients, however, we did not observe any change in the neurologic examination during the early postoperative period. Neurologic complications after CABG may be related to the size and composition of MES rather than to their absolute numbers. A large prospective multicentric randomized trial may help to elucidate this complex issue.

Early neurobehavioral disorders after cardiac surgery: a comparative analysis of coronary artery bypass graft surgery and valve replacement

OBJECTIVE

To analyze neurobehavioral disorders in the early postoperative period after valve replacement and coronary artery bypass graft (CABG) surgery.

DESIGN

Prospective study.

SETTING

University hospital.

PARTICIPANTS

Patients undergoing elective cardiac surgery with cardiopulmonary bypass; 42 patients in the valve replacement surgery group and 42 patients in the CABG surgery group, with both groups matched post hoc for age, sex, and preoperative cognitive status.

MEASUREMENTS AND MAIN RESULTS

All subjects were investigated preoperatively as well as 2 and 7 days postoperatively with a comprehensive neuropsychologic and neuropsychiatric assessment. The groups did not significantly differ with respect to the incidence of postoperative neuropsychiatric disorders. Valve replacement surgery patients exhibited more severe neuropsychologic deficits and showed a slower recovery than patients who underwent CABG surgery. In both groups, postoperative neuropsychologic alterations were most marked in fluency, arithmetic, and memory performance.

CONCLUSION

These results indicate that patients after valve replacement surgery have a higher risk of postoperative neuropsychologic alterations mainly attributable to temporal lobe dysfunction. This finding corresponds to a specific vulnerability of hippocampal structures to transient hypoxia.

Coronary artery bypass performed without the use of cardiopulmonary bypass is associated with reduced cerebral microemboli and improved clinical results

STUDY OBJECTIVES

Strokes and neurocognitive dysfunction have been correlated with cerebral microemboli produced during cardiopulmonary bypass (CPB). The purpose of this study was to determine whether, and to what extent, off-pump coronary artery bypass (OPCAB) reduces the occurrence of cerebral microemboli compared with traditional coronary artery bypass grafting (CABG) with CPB and to compare clinical results.

DESIGN AND PATIENTS

A retrospective review of 137 patients undergoing elective CABG was performed, 70 of whom underwent traditional CABG and 67 of whom underwent OPCAB. Using transcranial Doppler ultrasonography, 40 patients (20 CABG, 20 OPCAB) were continuously monitored intraoperatively for the occurrence and pattern of cerebral microemboli.

SETTING

Private, university-affiliated tertiary care hospitals.

RESULTS

There was no statistical difference in the age, sex, or underlying comorbidities between those patients undergoing CABG and OPCAB. CABG patients did have a slightly lower preoperative ejection fraction (50.9% vs 55.5%, p = 0.03). Despite these similar preoperative characteristics, the OPCAB group experienced significant reductions in cerebral microemboli (27 vs 1,766, p = 0.003), transfusion requirements (29.9% vs 47.1%, p = 0.04), intubation time (3.3 vs 9.5 h, p < 0.001), ICU length of stay (1.5 vs 2.8 days, p = 0.02), and overall hospitalization (4.9 vs 6.6 days, p = 0.01) without an increase in mortality. Fewer strokes and deaths were observed in the OPCAB group, but these trends failed to reach statistical significance.

CONCLUSIONS

In similar patient populations, OPCAB was associated with significantly fewer cerebral microemboli and improved clinical results without an increase in mortality. We believe that these early results support OPCAB as a viable and potentially safer alternative to traditional CABG.

Issues associated with the identification of cognitive change following coronary artery bypass grafting

OBJECTIVE

Coronary artery bypass grafting (CABG) is a surgical procedure used to treat individuals with ischaemic heart disease and to relieve angina. Disruption to the central nervous system (CNS) has frequently been reported by patients who have undergone CABG.

METHOD

The following paper is a review of the literature that has examined the effects of CABG on the CNS.

RESULTS AND CONCLUSIONS

It becomes apparent that issues about the incidence and severity of post-CABG cognitive decline are still unresolved. First, the cause of post-CABG CNS change has not yet been established, although the presence of changes to brain microvasculature as a result of the presence of microemboli appears to be a likely factor. Second, while some studies have reported high rates of poor performance on neuropsychological tests postoperatively, these reports are often subject to confounds such as variability in postoperative testing intervals, the definition of decline and the neuropsychological test batteries used. Finally, improvements in surgical techniques and changes in patient characteristics may have changed the real nature and prevalence of post-CABG cognitive decline. The review finishes with a series of recommendations for the neuropsychological study of CABG.

Transcranial Doppler assessment of cerebral embolic disorders

Transcranial Doppler ultrasound allows noninvasive monitoring of the large intracranial vessels. Microembolic signals (MES) have been observed under a variety of circumstances, especially in symptomatic carotid stenosis, high-risk cardiac conditions, and surgical procedures (such as carotid endarterectomy and cardiopulmonary bypass surgery). Technical considerations have presented numerous challenges to the interpretation of these signals, many of which appear to represent small emboli traveling in the blood flow. The technical aspects of these MES are discussed and their significance in relation to cerebral ischemia and its prevention are examined in some detail.

Influence of cranioplasty on postural blood flow regulation, cerebrovascular reserve capacity, and cerebral glucose metabolism

OBJECT

The indications for cranioplasty after decompressive craniectomy are cosmetic repair and, mainly, restoration of cerebral protection. Although neurological improvement after cranioplasty is repeatedly noted, the reasons for this remain unclear. Few observations concerning the impact of cerebrospinal fluid hydrodynamic and/or atmospheric pressure have been published during the last decades. Relevant data concerning the cerebrovascular reserve (CVR) capacity and cerebral glucose metabolism before and after cranioplasty have been lacking until now. To gain further insight, this study was undertaken to investigate the impact of cranioplasty on indices of cerebral blood flow regulation and metabolism.

METHODS

Thirteen patients in whom extensive craniectomies had been performed underwent a meticulous study of blood flow velocities in the middle cerebral artery (MCA) and extracranial internal carotid artery (ICA), as assessed by transcranial Doppler ultrasonography during postural maneuvers (supine and sitting positions) and during stimulation with 1 g of acetazolamide for the interpretation of CVR capacity. Twelve patients underwent 18-fluorodeoxyglucose positron emission tomography. These measurements were obtained before and 7 days after cranioplasty. Cranioplasty improved preoperative differences in MCA blood flow velocities when comparing those in the injured with those in the uninjured hemisphere. Similarly, cranioplasty resolved decreases in extracranial ICA blood flow in the injured hemisphere that were induced by postural changes, which was a constant finding prior to this procedure. More strikingly, however, the CVR capacity, which was severely impaired in both hemispheres, increased significantly after the procedure. Metabolic deficits, which were observed in the injured hemisphere, were found to improve after reimplantation of the skull bone flap.

CONCLUSIONS

Cranioplasty appears to affect postural blood flow regulation, CVR capacity, and cerebral glucose metabolism markedly. Thus, early cranioplasty is warranted to facilitate rehabilitation in patients after decompressive craniectomy.

Cerebral oligaemia episode triggers free radical formation and late cognitive deficiencies

Sixty minutes of cerebral oligaemic hypoxia, induced by bilateral clamping of the carotid arteries (BCCA) in pentobarbital-anaesthetized normotensive rats, induces a late progressive cognitive decline when compared with sham-operated controls. Analysis at BCCA of hippocampal metabolism using microdialysis showed increased release of glutamate, aspartate and gamma-aminobutyric acid, followed by a progressive rise in the formation of hydroxyl free radicals measured as 2,3-dihydroxybenzoic acid (2,3-DHBA), their reaction product with salicylate, though only in the re-perfusion phase. In the striatum increased dopamine release occurred during BCCA, whereas glutamate and aspartate showed an increase only during the late re-perfusion phase. gamma-Aminobutyric acid (GABA) concentration increased during BCCA and early re-perfusion. An increase in 2,3-DHBA was seen during BCCA, and persisted over 2 h of re-perfusion. Six and 13 months after surgery, though not as early as 3 months, BCCA-treated rats perform worse than sham-operated controls in a water-maze, where decreased swimming speed reveals striatal dysfunction, while hippocampal dysfunction manifested as diminished spatial bias. These results show that cerebral oligaemia, similarly to cerebral ischaemia, leads to increased extracellular dopamine, aspartate and glutamate, and the production of hydroxyl radicals in structures associated with learning and memory processes. Unlike cerebral ischaemia, in cerebral oligaemia the appearance of spatial memory deficits is delayed.