A systematic comparison of the risks of stroke and death due to carotid endarterectomy for symptomatic and asymptomatic stenosis

Local versus general anaesthesia for carotid endarterectomy

BACKGROUND

Carotid endarterectomy reduces the risk of stroke in people with recently symptomatic, severe carotid artery stenosis. However, there are significant perioperative risks which may be lessened by performing the operation under local rather than general anaesthetic.

OBJECTIVES

The aim of this review was to assess the risks of endarterectomy under local compared with general anaesthetic.

SEARCH STRATEGY

We searched the Stroke Group trials register (April 2003), MEDLINE (1966 to April 2003), EMBASE (1980 to 2002), and Index to Scientific and Technical Proceedings (1980 to 1994). We handsearched 13 relevant journals up to 2002, and searched the reference lists of articles identified. We also advertised the review in Vascular News (a newspaper for European vascular specialists) in August 2001.

SELECTION CRITERIA

Randomised trials and non-randomised studies comparing carotid endarterectomy under local versus general anaesthetic.

DATA COLLECTION AND ANALYSIS

One reviewer selected studies for inclusion and another independently checked the decisions. Two reviewers assessed trial quality and independently extracted the data.

MAIN RESULTS

Seven randomised trials involving 554 operations, and 41 non-randomised studies involving 25622 operations were included. The methodological quality of the non-randomised trials was questionable. Eleven of the non-randomised studies were prospective and 29 reported on a consecutive series of patients. In nine non-randomised studies the number of arteries, as opposed to the number of patients, was unclear. Meta-analysis of the non-randomised studies showed that the use of local anaesthetic was associated with significant reductions in the odds of death (35 studies), stroke (31 studies), stroke or death (26 studies), myocardial infarction (22 studies), and pulmonary complications (7 studies), within 30 days of the operation. Meta-analysis of the randomised studies showed that the use of local anaesthetic was associated with a significant reduction in local haemorrhage (OR = 0.31, 95% CI = 0.12 to 0.79) within 30 days of the operation, but there was no evidence of a reduction in the odds of operative stroke. However, the trials were too small to allow reliable conclusions to be drawn, and in some studies intention-to-treat analyses were not possible because of exclusions.

REVIEWERS' CONCLUSIONS

There is insufficient evidence from randomised trials comparing carotid endarterectomy performed under local and general anaesthetic. Non-randomised studies suggest potential benefits with the use of local anaesthetic, but these studies may be biased. More randomised studies are needed.

Carotid artery revascularization through a radiated field

OBJECTIVE

Extracranial carotid stenosis is a complication of external head and neck irradiation. The safety and durability of carotid artery revascularization through a radiated field has been debated. We describe the immediate and long-term results in a series of 27 consecutive patients who received treatment over 12 years.

METHODS

From May 1990 to May 2002, 27 consecutive patients underwent 30 primary carotid artery revascularization procedures. All patients had received previous radiation therapy within a mean interval of 10 years (range, 1-26 years), with average radiation dose of 62 Gy (range, 50-70 Gy). Moderate to severe scarring of the skin or radiation fibrosis was present in three fourths of patients. Thirteen patients (48%) had undergone radical neck dissection, and 2 patients had a permanent tracheotomy. The indications for carotid surgery included high-grade (>70%) symptomatic stenosis in 18 patients (60%) and high-grade asymptomatic stenosis in 12 patients (40%). General anesthesia with systematic shunting was used in 18 patients (60%), and regional anesthesia with selective shunting was used in 12 patients (40%). Operations included standard carotid endarterectomy (n = 20), with patch angioplasty (n = 12) or direct closure (n = 8); carotid interposition bypass grafting (n = 7); and subclavian to carotid bypass grafting (n = 3). Primary closure of the surgical wound was performed in all procedures without any special muscular or skin flaps. All patients were followed up for a mean of 40 months (range, 3-99 months).

RESULTS

There was one (3.3%) perioperative death, from massive intracerebral hemorrhage; and 1 patient had a transient ischemic attack. In-hospital complications included neck hematoma in 2 patients, which required surgical drainage in 1 patient. There was neither delayed wound healing nor infection. Twelve patients died during follow-up, of causes not related to treatment. None of the surviving patients had further stroke, and all remained asymptomatic. Follow-up duplex scans showed asymptomatic recurrent stenosis greater than 60% in 3 patients, 2 of whom with stenosis greater than 80% underwent repeat operation. Risk for recurrent stenosis greater than 60% at 18 months was 16.6%. Recurrent stenosis occurred in 2 of these patients after saphenous vein bypass, and in 1 patient after endarterectomy with vein patch angioplasty.

CONCLUSION

The clinical results and sustained freedom from symptoms and stroke over 40-month follow-up suggests that carotid revascularization through a radiated field is a safe and durable procedure in patients at high surgical risk, despite a marked incidence of recurrent stenosis.

Noninvasive analysis of conjunctival microcirculation during carotid artery surgery reveals microvascular evidence of collateral compensation and stenosis-dependent adaptation

OBJECTIVE

Hemodynamically relevant internal carotid artery (ICA) stenosis is a major cause of ischemic stroke. Despite its long-term benefit, carotid endarterectomy may also be associated with severe neurologic deficits. Intraoperative and early recognition of ischemia in the region of the ICA may reduce this risk. To date, direct imaging and quantitative analysis of microvascular structures and function in the human ICA region have not been possible. We purposed to visualize and quantify ischemia/reperfusion-induced microcirculatory changes in the terminal vascular bed of the ICA in patients undergoing unilateral ICA endarterectomy.

METHODS

Sequential analysis of the ipsilateral and contralateral conjunctival microcirculation was performed with orthogonal polarized spectral imaging in 33 patients undergoing unilateral ICA endarterectomy because of moderate or severe ICA stenosis (North American Symptomatic Carotid Endarterectomy Trial score, 75% +/- 13%), before clamping the ICA (baseline), during clamping of the external carotid artery and ICA, during reperfusion of the ICA (intraluminal shunt), during the second clamping of the ICA (shunt removal), after declamping (reperfusion) of the external carotid artery and ICA, and 15 to 20 minutes after the second ICA reperfusion.

RESULTS

During ICA clamping for shunt placement, ipsilateral and contralateral conjunctival capillary perfusion was significantly decreased, but it was completely restored after reperfusion with carotid shunting. Reclamping of the ICA for shunt removal caused microvascular dysfunction, which was significantly less pronounced than that observed during the first clamping. The individual degree of ICA stenosis was inversely correlated with the ipsilateral and contralateral decrease in conjunctival functional capillary density during the first ICA clamping.

CONCLUSIONS

These results suggest adaptive mechanisms of capillary perfusion with increasing stenosis and development of collateral compensatory circulation in the vascular region of the human ICA. Conjunctival orthogonal polarized spectral imaging during unilateral ICA reconstruction enables continuous noninvasive analysis of bilateral conjunctival microcirculation in the terminal region of the ICA and enables monitoring for efficient carotid shunt perfusion during and after endarterectomy.

Initial multicenter experience with a novel distal protection filter during carotid artery stent implantation

Atheroembolization resulting in transient or permanent neurologic impairment is the most common complication of catheter-based percutaneous carotid artery intervention. Protection of the distal cerebral vasculature during carotid stent implantation may enhance procedural safety. Carotid stent implantation with distal cerebral protection using the FilterWire EX was performed in 35 consecutive patients undergoing 36 procedures at six centers. The FilterWire was delivered and deployed successfully in all 36 cases, and embolic material was retrieved from 74% of procedures. The 30-day rate of major adverse events (death, major or minor stroke) was 0%. Transient ipsilateral periprocedural neurologic ischemia developed in two patients (5.7%), both resolving within 30 min. Distal cerebral protection with the FilterWire during carotid stenting is feasible and safe, results in capture and extraction of atheroembolic debris in the majority of patients while affording uninterrupted cerebral perfusion, and in this initial multicenter experience was associated with a high rate of procedural success without major complications.

Determining patient preference for treatment of extracranial carotid artery stenosis: carotid angioplasty and stenting versus carotid endarterectomy

Revascularization of extracranial carotid artery stenosis (ECAS) continues to be the subject of spirited academic debate. Conflicting studies in the literature have fostered uncertainty among patients choosing between CEA and CAS. We obtained preference-based utilities from prospective patients being evaluated for ECAS and incorporated them into a decision analytic model. Patients being evaluated for ECAS in an outpatient setting were interviewed prior to their initial visit with a vascular surgeon. Patient preference data were elicited using probability trade-off (PTO) assessment and time trade-off (TTO) method. Decision analysis was performed to compare CEA with CAS. Morbidity and mortality rates were obtained from recent literature reports from the same institution. Our results showed that when patients are informed, they prefer and will more often choose CEA over CAS for revascularization of ECAS. Among patients preferring CAS, they expect no more than a 46% increase in the rate of stroke and/or death. Future clinical studies on true stroke rates for CAS will be required to further refine this analysis.

New brain lesions at MR imaging after carotid angioplasty and stent placement

PURPOSE

To assess, with magnetic resonance (MR) imaging, the number and size of new brain lesions after carotid angioplasty and stent placement (CAS) and to evaluate the association of these new lesions with neurologic deficits and transcranial Doppler ultrasonographic (US) data.

MATERIALS AND METHODS

Seventy-two consecutive CAS procedures were performed in 72 patients. Patients underwent neurologic examination before, during, immediately after, and 1 day, 3 months, and 1 year after CAS. MR imaging was used before and after CAS to assess the number of symptomatic and silent new infarctions. Two radiologists reviewed all pre- and postintervention MR images. The radiologists were blinded to the clinical data.

RESULTS

Postprocedural MR images showed new lesions on the side of stent placement in 11 patients. In six patients, the new lesions were clinically silent. Two patients had a major stroke, one had a minor stroke, and two had transient ischemic attack. In patients who had had transient ischemic attack or stroke before CAS, the frequency of new lesions at postprocedural MR imaging was higher (23%) than in asymptomatic patients (12%); this difference was not statistically significant (P =.29). There was no statistically significant correlation between embolic load as detected with transcranial Doppler US monitoring and the occurrence of either clinical symptoms or new lesions seen at MR imaging.

CONCLUSION

CAS is associated with embolic events. The majority of new lesions seen on postintervention MR images are not detected at neurologic examination.

Asymptomatic carotid stenosis in patients on medical treatment alone

OBJECTIVE

the aim of this study was to investigate the effect of currently recommended medical treatment (MT) on changes in carotid stenosis in a group of asymptomatic patients taken from the Asymptomatic Carotid Surgery Trial (ACST).

METHOD

collaborators in ACST were given information on MT for stroke prevention (including antiplatelet agents, lipid-lowering drugs, diabetic and hypertension control). Patients underwent clinical examination and duplex scanning at entry, 4 months following randomisation and annually thereafter. The cohort of patients studied were those randomised to MT with complete follow up duplex datasets at four years (n=219). None had undergone carotid endarterectomy (CEA) or developed ipsilateral carotid symptoms.

RESULTS

there was no change in median carotid stenosis over four years (baseline 79% (IQR 10%) and 4 year median 79% (IQR 10%)) a median difference of 0 with Q1=-5 and Q3=+5 (p=0.98 Wilcoxon one sample test), whilst in many patients' stenoses progressed and regressed during this time. No individual MT variable correlated with stenosis progression or regression.

CONCLUSION

in this group of ACST patients on MT, mean carotid stenosis was unchanged over 4 years. Individual patients' stenoses progressed (and regressed) without symptoms occurring. An increase in stenosis should not be the sole basis for deciding to operate on an asymptomatic patient.

Variation in surgical and anaesthetic technique and associations with operative risk in the European carotid surgery trial: implications for trials of ancillary techniques

OBJECTIVES

several ancillary surgical techniques, such as shunting and patching, are used in association with carotid endarterectomy. However, the balance of risks and benefits of these techniques is uncertain because of the lack of large randomised controlled trials (RCTs). To assess the potential for further trials, we studied the variation in use of these techniques by surgeon and by country in the European Carotid Surgery Trial (ECST).

METHODS

use of each ancillary technique was assessed by surgeon and by country. For each technique, the relationships between the use of the technique and baseline patient characteristics, use of other techniques, and the 30-day operative risk of stroke and death were determined.

RESULTS

there was considerable variation between surgeons in the use of ancillary operative techniques both within (p<0.001 for shunting and patching), and between countries (p<0.001 for shunting and patching). Some surgeons used techniques selectively, and so the characteristics of patients differed depending on which techniques were used. Use of each technique was also significantly associated with the use of other techniques. Multiple regression analysis, taking into account all these factors, found no statistically significant associations between operative risk and the use of shunting, patching, intra-operative EEG monitoring, or type of anaesthetic. The only surgical technique significantly associated with an increased operative risk was not using intra-operative anticoagulation (hazard ratio=2.33, 95% CI=1.4-4.2). Other factors associated with an increased risk were an operation time of less than 1 h, or greater than 1.5 h, and the surgeons' subjective assessment that the operation was difficult.

CONCLUSIONS

in the ECST, operative risk was more closely related to patient characteristics, length of surgery, and the surgeons' perception of the difficulty of the operation, than to the use of particular ancillary operative techniques. The considerable variation between surgeons, and between countries, in the use of ancillary techniques is in keeping with the lack of convincing data from RCTs, and suggests that there should be sufficient uncertainty to make large pragmatic trials possible.

Clinical and radiographic risk factors for operative stroke and death in the European carotid surgery trial

OBJECTIVES

carotid endarterectomy is associated with significant morbidity and mortality. A better understanding of the relationships between baseline characteristics and outcome may help to reduce the risks of surgery. In order to make accurate and unbiased estimates of surgical risk it is important to study cohorts of patients that were established prospectively, where independent physicians assessed outcome, and where the decision to analyse and report the results was not data-dependent. The surgical arm of the European Carotid Surgery Trial (ECST) is such a cohort.

METHODS

the 30-day outcome of carotid endarterectomy was analysed in ECST surgery patients in relation to their baseline clinical and angiographic characteristics. The severity of operative strokes was compared with that of strokes that occurred in the medical group.

RESULTS

1729 patients underwent trial surgery. There were 17 deaths (1.0%, 95% CI=0.6-1.6) and 105 non-fatal major strokes (6.1%, 95% CI=5.0-7.3) within 30 days of surgery. The risk of major stroke or death was 7.1% (95% CI=5.9-8.4). The risk of disabling or fatal stroke was 3.0% (95% CI=2.1-3.8). The ratio of disabling to non-disabling operative strokes was similar to that in the medical group. Several baseline characteristics predicted the operative risk of stroke and death in univariate analyses, but only four were independent risk factors in a multiple regression analysis: presentation with cerebral TIA vs ocular ischaemic events only (HR=2.99, 95% CI=1.33-6.69, p=0.008); female sex (HR=2.04, 95% CI=1.37--3.06, p=0.001); systolic hypertension (HR=1.01 per 10 mmHg, 95% CI=1.00-1.02, p=0.03) and peripheral vascular disease (HR=2.17, 95% CI=1.17-2.89, p=0.001).

CONCLUSIONS

the operative risk of stroke and death in the ECST was comparable with other prospective studies and trials in which patients were assessed postoperatively by both a physician and a surgeon. Case fatality and disability after operative stroke are similar to strokes that occur on medical treatment only. Several baseline patient characteristics predict surgical risk and it may be possible to use these characteristics to aid patient selection and surgical audit.

Risk modelling study for carotid endarterectomy

BACKGROUND

The aims of this study were to identify factors that influence the risk of stroke or death following carotid endarterectomy (CEA) and to develop a model to aid in comparative audit of vascular surgeons and units.

METHODS

A series of 839 CEAs performed by four vascular surgeons between 1992 and 1999 was analysed. Multiple logistic regression analysis was used to model the effect of 15 possible risk factors on the 30-day risk of stroke or death. Outcome was compared for four surgeons and two units after adjustment for the significant risk factors.

RESULTS

The overall 30-day stroke or death rate was 3.9 per cent (29 of 741). Heart disease, diabetes and stroke were significant risk factors. The 30-day predicted stroke or death rates increased with increasing risk scores. The observed 30-day stroke or death rate was 3.9 per cent for both vascular units and varied from 3.0 to 4.2 per cent for the four vascular surgeons. Differences in the outcomes between the surgeons and vascular units did not reach statistical significance after risk adjustment.

CONCLUSION

Diabetes, heart disease and stroke are significant risk factors for stroke or death following CEA. The risk score model identified patients at higher risk and aided in comparative audit.

In search of tools to aid logical thinking and communicating about medical decision making

To have real-time impact on medical decision making, decision analysts need a wide variety of tools to aid logical thinking and communication. Decision models provide a formal framework to integrate evidence and values, but they are commonly perceived as complex and difficult to understand by those unfamiliar with the methods, especially in the context of clinical decision making. The theory of constraints, introduced by Eliyahu Goldratt in the business world, provides a set of tools for logical thinking and communication that could potentially be useful in medical decision making. The author used the concept of a conflict resolution diagram to analyze the decision to perform carotid endarterectomy prior to coronary artery bypass grafting in a patient with both symptomatic coronary and asymptomatic carotid artery disease. The method enabled clinicians to visualize and analyze the issues, identify and discuss the underlying assumptions, search for the best available evidence, and use the evidence to make a well-founded decision. The method also facilitated communication among those involved in the care of the patient. Techniques from fields other than decision analysis can potentially expand the repertoire of tools available to support medical decision making and to facilitate communication in decision consults.

Database Conference January 27-30, 2000, Washington D.C.--Do existing databases answer clinical questions about geriatric cardiovascular disease and stroke?

EXECUTIVE SUMMARY: Most randomized, controlled trials evaluating the effectiveness of pharmaceutical, surgical, and device interventions for the prevention and treatment of cardiovascular disease have excluded patients over 75 years of age. Consequently, the use of these therapies in the older population is based on extrapolation of safety and effectiveness data obtained from younger patients. However, there are many registries and observational databases that contain large amounts of data on patients 75 years of age and older, as well as on younger patients. Although conclusions from such data are limited, it is possible to define the characteristics of patients who did well and those who did poorly. The goal of this conference was to convene the principal investigators of these databases, and others in the field of geriatric cardiology, to address questions relating to the safety and effectiveness of treatment interventions for several cardiovascular conditions in the elderly. Seven committees discussed the following topics: (I) Risk Factor Modification in the Elderly; (II) Chronic Heart Failure; (III) Chronic Coronary Artery Disease: Role of Revascularization; (IV) Acute Myocardial Infarction; (V) Valve Surgery in the Elderly; (VI) Electrophysiology, Pacemaker, and Automatic Internal Cardioverter Defibrillators Databases; (VII) Carotid Endarterectomy in the Elderly. The chairs of these committees were asked to invite principal investigators of key databases in each of these areas to discuss and prepare a written statement concerning the available safety and efficacy data regarding interventions for these conditions and to identify and prioritize areas for future study. The ultimate goal is to stimulate further collaborative outcomes research in the elderly so as to place the treatment of cardiovascular disease on a more scientific basis.

Value of intraoperative duplex imaging during supervised carotid endarterectomy

BACKGROUND

For overall benefit, carotid endarterectomy requires low perioperative morbidity and mortality rates. Carotid thrombosis is usually secondary to technical error, which may be related to the experience of the operator. In this retrospective study the clinical and technical outcome of carotid endarterectomies performed by one consultant and five trainees were compared.

METHODS

Some 149 patients underwent carotid endarterectomy; 89 were operated on by the consultant and 60 by trainees. Intraoperative duplex imaging of the carotid repair was performed before wound closure, and re-exploration was carried out when there was a residual severe stenosis associated with an intimal flap.

RESULTS

There was no significant difference in clinical outcome between operations done by consultant or trainees. There was a significant increase in the number of stenoses, kinks and flaps in carotid endarterectomies performed by trainees compared with those of the consultant both before (chi2 = 12.0, 1 d.f., P < 0.001) and after (chi2 = 10.1, 1 d.f., P < 0.001) correction.

CONCLUSION

Intraoperative duplex imaging may facilitate training by providing an objective assessment of the quality of the operation.

Interventional advances in long-term stroke prevention

Endovascular angioplasty and stent placement are rapidly emerging therapeutic modalities for selected patients with carotid arterial occlusive disease. Prospective analyses of several large studies have shown that although carotid endarterectomy is the standard of care for most patients, it is associated with significant morbidity and mortality in high-risk patients. When carotid endarterectomy is not feasible in patients with conditions such as contralateral occlusions, recurrent stenosis, and pre-existing cranial palsies, carotid stenting is the treatment of choice. Adjunctive administration of potent antiplatelet agents such as clopidogrel and aspirin appears to reduce the risk of stroke. Currently available embolization-prevention devices and nitinol stents greatly reduce the mortality and morbidity because of embolization during carotid stenting. The spectrum of carotid diseases that can be safely treated with endovascular intervention will increase as new and safer options become available.

Causes of perioperative stroke after carotid endarterectomy: special considerations in symptomatic patients

In order to maximize the efficacy of carotid endarterectomy (CEA), the rate of perioperative stroke must be kept to a minimum. A recent analysis of carotid surgery at our institution found that most perioperative strokes were due to technical errors resulting in thrombosis or embolization. From 1992 through 1997 we have performed nearly 1200 additional CEAs; the purpose of this study was to examine recent trends in the causes of perioperative stroke, with specific attention to differences in symptomatic and asymptomatic patients. The records of 1041 patients undergoing 1165 CEAs were reviewed from a prospectively compiled database. Analysis of these data showed that a history of preoperative stroke appears to increase the risk of perioperative stroke after CEA. Surgical factors associated with perioperative stroke include an inability to tolerate clamping, use of an intraarterial shunt, and having surgery performed under general anesthesia; these factors are clearly interrelated and only the use of intraarterial shunting remains a risk factor by multivariate analysis. Over half of all perioperative strokes (54%) appear to be caused by intraoperative or postoperative thrombosis and embolization. The patient requiring use of intraarterial shunting and/or with a preoperative stroke most likely has a significant watershed area of brain at increased risk of infarction. However, technical errors are still the most common cause of perioperative stroke in these high-risk patients. Such high-risk patients may manifest clinical stroke from small emboli that may be tolerated by asymptomatic clamp-tolerant patients. Technical precision and appropriate cerebral protection are particularly critical for successful outcomes in high-risk patients.

Carotid artery stent placement for atherosclerotic disease: rationale, technique, and current status

Carotid arterial endarterectomy is considered to be the standard for the treatment of atherosclerotic carotid arterial occlusive disease. This has been validated with results of several randomized controlled trials in which its effectiveness has been demonstrated over that of the best nonsurgical therapy. In the past several years, however, carotid angioplasty with stent placement has emerged as a potential alternative to carotid endarterectomy. This article represents a critical examination of the rationale for carotid revascularization; the history of endovascular techniques for the treatment of carotid atherosclerosis, beginning with balloon angioplasty and evolving to the use of stents; and the evidence supporting the effectiveness of the endovascular approach. A brief description of the current technical aspects of carotid artery stent placement is presented. The future status of the endovascular approach will be determined with randomized trials in which carotid artery stent placement is directly compared with endarterectomy, as well as by the potential for further innovation and improvement in endovascular devices, technique, and safety.

Surgeon characteristics associated with mortality and morbidity following carotid endarterectomy

PURPOSE

To identify surgeon characteristics associated with mortality or morbidity, following carotid endarterectomy (CEA).

METHODS

Data on all inpatient discharges from the 284 nonfederal Pennsylvania hospitals were obtained from the Pennsylvania Health Care Cost Containment Council for the period from 1994 to 1995. Physician data were obtained from the Physicians List of the American Medical Association, including name, gender, specialty, year of birth, board certified, and year of licensure. Cases were selected if any of six procedures codes were ICD-9-CM rubric 38.12, indicating CEA.

RESULTS

Among the 12,725 cases studied, in-hospital mortality was 0.7%, nonfatal morbidity was 3.0%, and the total bad outcome rate was 3.7%. Surgeons who performed 1 to 2 CEAs over 2 years had the highest mortality (2.0%) and total bad outcome (9.2%) rates. For surgeons performing three or more cases in 2 years, increased volume was not associated with better outcomes. A greater number of years since the surgeon was licensed was associated with greater mortality (p = 0.001), but not with morbidity or bad outcome rates. In regression analyses that adjusted for patient risk, both years since licensure and specialty predicted surgical mortality rate, but only volume predicted surgical bad outcome rate.

CONCLUSIONS

More years since licensure and very low patient volume are associated with worse patient outcomes following CEA.

Carotid angioplasty and stenting: new horizons

Advances in technology have made it possible for lesions that affect the carotid artery, both extra-and intracranially, to be treated by endovascular means. Depending upon the type and location of the pathology, as well as the existing comorbidities in any given patient, angioplasty and stenting may be considered an alternative to traditional methods of revascularization. In fact, in some instances, endovascular therapy may be the procedure of choice. For patients whose lesions can be treated either surgically or endovascularly, future randomized trials will help define the role of each type of procedure.

Risk factors and significance of finding asymptomatic retinal emboli

PURPOSE

To assess the prevalence rates for asymptomatic retinal emboli among both younger and older individuals, with single and multiple potential risk factors, in order to alert clinicians to the probability of finding retinal emboli in patients with varying characteristics.

METHODS

In all, 3654 people aged 49-97 attending the Blue Mountains Eye Study had a detailed eye examination which included retinal photographs of the central and peripheral retinal fields. Retinal emboli were identified during masked photographic grading and definite cases were adjudicated.

RESULTS

Retinal emboli were found in 51 subjects (1.4% of the population); these included 1.1% of people aged 49-69 years (middle-aged subjects) and 2.0% of people aged more than 70 years (older subjects). Risk factors identified were male sex, increasing age, hypertension, current smoking, history of any vascular event (angina, myocardial infarct, stroke) or history of vascular surgery. Among middle-aged subjects, current smoking and history of hypertension or a vascular event were significantly associated with emboli (odds ratios (OR) 2.3-3.1), while in older subjects, history of vascular surgery was related (OR 4.7). The highest prevalence of emboli (5.5%) was found in people who reported a history of hypertension and also smoked (OR 6.0). Among hypertensive men who smoked, emboli were present in 7.6%.

CONCLUSIONS

This study indicates that although asymptomatic retinal emboli are relatively infrequent in the general older population, these lesions are surprisingly common in people (particularly men) with multiple risk factors. Ophthalmologists could routinely screen for emboli and consider alerting the patients' general practitioners to review vascular risk factors.

Evaluation of carotid endarterectomy with sequential MR perfusion imaging: a preliminary 12-month follow up

AIM

The clinical benefit of carotid endarterectomy is partially determined by peri-operative mortality and morbidity. Post-operative abnormalities in cerebral perfusion may be a risk factor for cerebral haemorrhage, and may be estimated from Bolus Arrival Time (BAT) as demonstrated by MR perfusion imaging. We aimed to use MR perfusion imaging to determine the temporal extent of these changes.

MATERIALS AND METHODS

A single slice gradient recalled echo sequence was employed in five patients who underwent carotid endarterectomy. Sequential studies were undertaken pre-operatively, 3-5 days post carotid endarterectomy, and additionally at 3, 6 and 12 months.

RESULTS

Asymmetric BATs were demonstrated in 3/5 patients, changes occurring as late as 6 to 12 months after carotid endarterectomy. These changes were not associated with either clinical or conventional MR morphological complications.

CONCLUSIONS

MR perfusion imaging is able to demonstrate changes in BAT characteristics for up to 12 months after carotid endarterectomy. The clinical significance and underlying cause of these changes, including any association with post carotid endarterectomy hyperaemia, remains unknown.

Refining the indications for carotid endarterectomy in patients with symptomatic carotid stenosis: A systematic review

OBJECTIVE

The purpose of this study was to summarize the existing literature on the efficacy of carotid endarterectomy in patients with ipsilateral symptomatic carotid stenosis.

METHODS

Database searching, relevance assessment, methodologic quality assessments, and data extraction were all performed in duplicate with prespecified criteria.

RESULTS

Twenty-three publications were identified from the North American Symptomatic Carotid Endarterectomy Trial, the European Carotid Surgery Trial, and the Veterans Affairs Cooperative Studies Program. Stenosis was reported as measured in the North American Symptomatic Carotid Endarterectomy Trial. In patients with >70% stenosis, carotid endarterectomy was associated with a pooled relative risk reduction of 48% (95% confidence interval [CI], 27% to 73%) and an absolute risk reduction of 6.7% (95% CI, 3.2% to 10%) for the outcome of death or major disability from stroke. This translates into a number needed to treat of 15 (95% CI, 10 to 31). For patients with 50% to 69% stenosis, the benefit of surgery was less and the confidence intervals were wider. A relative risk reduction of 27% (95% CI, 5% to 44%), an absolute risk reduction of 4.7% (95% CI, 0.8% to 8.7%), and a number needed to treat of 21 (95% CI, 11 to 125) were observed in this group. The patients with the lowest degrees of stenosis (<50%) were harmed by the intervention (number needed to harm, 45). Increasing degree of stenosis, increasing age, male sex, the presence of other medical risk factors, and the presence of hemispheric rather than retinal antecedent events were factors that increased the benefits from surgery.

CONCLUSION

Carotid endarterectomy reduced death or major disability from stroke in patients with >50% symptomatic stenosis. To maximize the benefits of surgery, careful preoperative risk assessment and the maintenance of low rates of major perioperative complications are mandatory.

Cerebral ischemic disease and morphometric analyses of carotid plaques

Atherosclerotic carotid plaque morphology and especially, intraplaque hemorrhage are assumed to be related to neurological symptoms. Most researchers have only investigated the incidence of intraplaque hemorrhage in symptomatic and asymptomatic patients. In the present study, the amount of intraplaque hemorrhage is determined in carotid endarterectomy specimens from 33 symptomatic and 14 asymptomatic patients that caused >70% luminal stenosis. The plaque components (fibrosis, lipids, intraplaque hemorrhage, calcification, and intraluminal thrombosis) were quantified as a percentage of the total plaque volume. A high incidence of intraplaque hemorrhage was found in both the symptomatic (94%, 31/33) and asymptomatic (71%, 10/14) patients. The amount of intraplaque hemorrhage was very small within the plaques of the symptomatic (0.39% +/- 0.70%) and asymptomatic (0.37% +/- 1.12%) patients. The plaques of the symptomatic patients contained more fibrosis than lipids (45.62% +/- 14.99% and 20.45% +/- 21.45%, respectively), as did the plaques of the asymptomatic patients (42. 51% +/- 15.28% and 15.46% +/- 15.22%, respectively). Finally, intraluminal thrombosis and calcification were rare. We conclude that the amount of intraplaque hemorrhage was very small and therefore question its direct role in the development of neurological symptoms. In general, the "unstable" plaque contained more fibrosis than lipids.

Low-dose and high-dose acetylsalicylic acid for patients undergoing carotid endarterectomy: a randomised controlled trial. ASA and Carotid Endarterectomy (ACE) Trial Collaborators

BACKGROUND

Endarterectomy benefits certain patients with carotid stenosis, but benefits are lessened by perioperative surgical risk. Acetylsalicylic acid lowers the risk of stroke in patients who have experienced transient ischaemic attack and stroke. We investigated appropriate doses and the role of acetylsalicylic acid in patients undergoing carotid endarterectomy.

METHODS

In a randomised, double-blind, controlled trial, 2849 patients scheduled for endarterectomy were randomly assigned 81 mg (n=709), 325 mg (n=708), 650 mg (n=715), or 1300 mg (n=717) acetylsalicylic acid daily, started before surgery and continued for 3 months. We recorded occurrences of stroke, myocardial infarction, and death. We compared patients on the two higher doses of acetylsalicylic acid with patients on the two lower doses.

FINDINGS

Surgery was cancelled in 45 patients, none were lost to follow-up by 30 days, and two were lost by 3 months. The combined rate of stroke, myocardial infarction, and death was lower in the low-dose groups than in the high-dose groups at 30 days (5.4 vs 7.0%, p=0.07) and at 3 months (6.2 vs 8.4%, p=0.03). In an efficacy analysis, which excluded patients taking 650 mg or more acetylsalicylic acid before randomisation, and patients randomised within 1 day of surgery, combined rates were 3.7% and 8.2%, respectively, at 30 days (p=0.002) and 4.2% and 10.0% at 3 months (p=0.0002).

INTERPRETATION

The risk of stroke, myocardial infarction, and death within 30 days and 3 months of endarterectomy is lower for patients taking 81 mg or 325 mg acetylsalicylic acid daily than for those taking 650 mg or 1300 mg.

Investigating individual subjects and screening populations for asymptomatic carotid stenosis can be harmful

OBJECTIVES

Trials suggesting that carotid endarterectomy in individual subjects with asymptomatic carotid stenosis reduces stroke risk have led to calls for screening. This study aimed to determine which groups might be harmed and which might benefit from a screening programme, and also to identify which individual subjects identified as positive for severe asymptomatic stenosis by carotid ultrasound are appropriate to put forward for further tests or procedures.

METHODS

A probability model was used to estimate the outcomes of three screening strategies: carotid ultrasound followed by catheter angiography, or by magnetic resonance angiography (MRA), or ultrasound alone, followed by carotid endarterectomy if severe stenosis is detected. Information from the current literature was used to estimate sensitivity and specificity of ultrasound and MRA, risks of angiography and endarterectomy, and risk reduction after surgery for severe stenosis. For each strategy over a range of possible prevalences of severe asymptomatic stenosis, overall benefit to harm ratio was calculated, and number of strokes or deaths prevented or caused per 10,000 subjects screened.

RESULTS

At the prevalence of carotid stenosis found in the general population (<1%) screening will cause more strokes than it prevents, even using the most optimistic published figures. Only at prevalences of over 20% are significant benefits seen, and then only in centres with high test sensitivity and specificity and very low angiographic and surgical risk. Groups with such a high prevalence have not yet been reliably identified. Screening individual subjects from high prevalence groups would have limited public health impact, with at best about 100 strokes prevented for every 10,000 screened at 20% prevalence.

CONCLUSIONS

Investigating asymptomatic individual subjects for carotid stenosis may be harmful except in high prevalence groups. There is insufficient information about which these groups are, and at present screening cannot be recommended. Acting on a positive carotid ultrasound test in individual subjects

Microembolic signals and intraoperative stroke in carotid endarterectomy

OBJECTIVES

Microembolic signals (high-intensity transient signals, HITS) detected by means of transcranial Doppler sonography (TCD) may be relevant for intraoperative strokes in carotid endarterectomy (CEA).

MATERIAL AND METHODS

An intraoperative HITS detection study was performed on 77 patients (63 men, 14 women, mean age+/-SD, 64+/-8 years) with a total of 81 CEAs. Using the Scandinavian Stroke Scale the patients were clinically examined by a neurologist preoperatively and postoperatively within 6 h. A deterioration of the Scandinavian Stroke Scale was considered an intraoperative stroke if persisting longer than 24 h. Cranial computed tomography (CT scan) was performed preoperatively and 3 to 5 days postoperatively. By means of TCD total HITS count and mean blood velocity changes, for shunting, were recorded sufficiently in the middle cerebral artery in 79 CEAs.

RESULTS

HITS were significantly more frequent in symptomatic [n = 53; HITS: median, 15 (range 1-159)] than in asymptomatic stenoses [n = 26; HITS: 6.5 (0-41); P < 0.001]. An intraoperative stroke in the hemisphere ipsilateral to the operation occurred in eight of the 81 CEAs. On postoperative CT scans, five of the eight strokes showed new corresponding territorial infarctions. In the three strokes without new CT lesions, the mean blood velocity changes after clamping indicated normal cerebral perfusion. Total HITS count was significantly higher in procedures with intraoperative strokes [n = 8; HITS: 33 (11-159)] than in the uncomplicated [n = 71; HITS: 10 (0-62); P = 0.002]. No stroke occurred in 37 CEAs with 10 or less HITS, but eight in 42 CEAs with 11 or more HITS [P = 0.006; relative risk 1.23 (95% confidence interval: 1.06 to 1.43)].

CONCLUSION

Microembolism seems clinically relevant in carotid endarterectomy. Asymptomatic patients may run a lower risk of intraoperative embolization.

Local versus general anaesthesia in carotid endarterectomy: a systematic review of the evidence

OBJECTIVE

To determine whether carotid endarterectomy under local anaesthesia is safer and as effective as under general anaesthesia.

DESIGN

Systematic review of the randomised and non-randomised studies.

MATERIALS

Studies were identified from the Cochrane Stroke Group's database plus additional handsearching and electronic searching.

METHODS

Two authors independently selected studies for inclusion and extracted details of trial quality and data on death, any stroke, myocardial infarction and other operative complications. Meta-analysis was performed using the Peto method.

RESULTS

There were 17 non-randomised studies (about 5970 patients) and only three randomised studies (143 patients). The non-randomised studies suggested that the use of local anaesthesia may be associated with clinically important reductions (approximately 50%) in the odds of stroke, stroke or death, myocardial infarction and pulmonary complications during the perioperative period, and with reductions in hospital stay. There were far too little data from the randomised trials to confirm or refute these findings: only one death and seven strokes were reported.

CONCLUSIONS

Non-randomised studies suggest potentially important benefits from performing carotid endarterectomy under local anaesthesia. However, these studies were seriously flawed and can only be hypothesis generating. The results must be confirmed in large well-designed randomised trials before any recommendations on the use of local anaesthetic can be made.

Hemodynamic ischemic stroke during carotid endarterectomy: an appraisal of risk and cerebral protection

PURPOSE

The purpose of this study was to validate the commonly accepted indicators of risk of ischemic stroke that indicate the necessity for cerebral protection during carotid endarterectomy (CEA), and to examine the efficacy of high-dose thiopentone sodium (thiopental) as a cerebral protection method in patients who are at high risk of intraoperative ischemic stroke.

METHOD

In a prospective study of 37 CEAs performed for symptomatic stenosis > 70%, functional and clinical indicators of risk of ischemic stroke during carotid cross-clamping were identified. Functional indicators of risk were the development of ischemic electro-encephalogram (EEG) changes and stump pressure < 25 mm Hg. Clinical indicators of risk were previous ischemic hemispheric stroke and severe bilateral disease. These indicators were correlated in all patients, some of whom had two or three coexisting indicators of risk. The EEG and stump pressure were monitored continuously during carotid occlusion in all operations. Carotid occlusion times were recorded. Intraluminal shunting was eliminated in favor of high-dose thiopental cerebral protection in all patients. Neurologic outcome was deemed to measure the efficacy of thiopental protection in patients who are identified to be at risk and, hence, in need of cerebral protection. The validity of the indicators used to identify risk of ischemic stroke during CEA was assessed.

RESULTS

The absolute stroke risk was found to be 29.7% for the whole group (37 patients) and 57.9% in 19 patients who had commonly accepted indications for protective shunting. The correlation of ischemic EEG changes with stump pressure < 25 mm Hg was only 27.3%, whereas the expected correlation based on well-documented reports in the literature was 100%. The lack of correlation may have been related to the prevention of ischemic EEG changes by thiopental. There were no neurologic deficits in the series.

CONCLUSIONS

The absence of neurologic deficit in the study indicated that thiopental protection was effective in preventing ischemic stroke in high-risk patients and safely replaced intraluminal shunting.

Causes of the increased stroke rate after carotid endarterectomy in patients with previous strokes

Patients who have sustained a preoperative stroke are at increased risk for perioperative stroke after carotid endarterectomy. At our institution this risk was recently shown to be increased two-to threefold. The purpose of this study was to investigate the reasons for the increased surgical risk in these patients. Records of 606 patients undergoing 704 consecutive carotid endarterectomies from 1988 through 1993 were reviewed. Patients who suffered preoperative strokes (n = 183) were compared to those who were either asymptomatic or experienced only transient ischemic attacks (TIAs) preoperatively (n = 423). Of the 183 patients who had suffered preoperative strokes, eight patients who experienced perioperative strokes after endarterectomy were compared with 175 who successfully underwent surgery. Patients with a prior stroke had an increased perioperative stroke rate (4.4% versus 1.2%, p = 0.01). They had a significantly higher incidence of hypertension (62.6% versus 47.9%, p < 0.001), cardiac disease (54.7% versus 40.7%, p = 0.001), and positive smoking history (52% versus 40.6%, p = 0.01) than did the asymptomatic/TIA patients. The presence of contralateral total occlusion was also significantly increased (22% versus 10.3%, p < 0.001). Although not statistically significant due to the overall small number of patients who sustained perioperative strokes, the preoperative stroke patients who sustained perioperative strokes had a higher incidence of hypertension (87.5% versus 61.5%) and contralateral total occlusion (37.5% versus 21.3%) than did those who successfully underwent surgery. Patients with both a prior stroke and contralateral total occlusion had a 7.5% perioperative stroke rate. Patients with both a prior stroke and hypertension had a 6.1% perioperative stroke rate. The perioperative strokes in patients with prior strokes were not related to the severity of the prior stroke, the interval between the stroke and surgery, the use of a shunt, or the type of anesthesia employed. Patients who have sustained preoperative strokes have a higher incidence of significant medical illnesses and overall cerebrovascular disease. Hypertension and total occlusion of the contralateral carotid artery appear to be particularly poor prognostic indicators of outcome after endarterectomy in these patients. Patients who have sustained preoperative strokes may be more likely to display clinical neurologic symptoms in response to any form of cerebral ischemia. In this higher risk subgroup, intraoperative and surgeon-dependent factors appear to play less of a role.