Carotid endarterectomy in asymptomatic patients--is contrast angiography necessary? A morbidity analysis

Quantitative assessment of retinal vessel density and thickness changes in internal carotid artery stenosis patients using optical coherence tomography angiography

OBJECTIVE

To quantitatively assess the retinal features of patients with different degrees of internal carotid artery stenosis (ICAS), particularly mild ICAS patients, utilizing optical coherence tomography angiography (OCTA).

METHODS

Thirty-two mild ICAS patients (mild ICAS group), 34 moderate to severe ICAS patients (nonmild ICAS group), and 40 controls were enrolled in this study. Retinal vessel density was quantitatively measured by OCTA, including radial peripapillary capillary vessel density (RPC-VD), superficial and deep capillary plexus vessel density (SCP/DCP-VD). Structural parameters were collected from optical coherence tomography (OCT), including retinal thickness and subfoveal choroidal thickness (SFCT). Furthermore, LASSO-penalized logistic regression was used to construct the diagnostic model based on retinal parameters. ROC curves and nomogram plots were used to assess the diagnostic ability of this model for ICAS.

RESULTS

The macular SCP-VD of mild ICAS patients was significantly lower than that of controls and lower than that of nonmild ICAS patients (all p < 0.05). However, there was no difference among the three groups in terms of DCP-VD (p > 0.05). RPC-VD could effectively discriminate between the mild ICAS group and the nonmild ICAS group (p = 0.005). For structural OCT, only the SFCT decreased as the ICAS degree increased (p < 0.05). Diagnostic scores based on retinal parameters showed a strong diagnostic capability for mild ICAS (AUC = 0.8656).

CONCLUSION

Mild ICAS patients exhibited distinct retinal features compared to nonmild ICAS patients and control subjects. OCTA potentially represents a promising method for the early detection of ICAS patients and the noninvasive surveillance of haemodynamic changes in those patients.

Imaging modalities to diagnose carotid artery stenosis: progress and prospect

In the past few decades, imaging has been developed to a high level of sophistication. Improvements from one-dimension (1D) to 2D images, and from 2D images to 3D models, have revolutionized the field of imaging. This not only helps in diagnosing various critical and fatal diseases in the early stages but also contributes to making informed clinical decisions on the follow-up treatment profile. Carotid artery stenosis (CAS) may potentially cause debilitating stroke, and its accurate early detection is therefore important. In this paper, the technical development of various CAS diagnosis imaging modalities and its impact on the clinical efficacy is thoroughly reviewed. These imaging modalities include duplex ultrasound (DUS), computed tomography angiography (CTA) and magnetic resonance angiography (MRA). For each of the imaging modalities considered, imaging methodology (principle), critical imaging parameters, and the extent of imaging the vulnerable plaque are discussed. DUS is usually the initial recommended CAS diagnostic examination. However, for the therapeutic intervention, either MRA or CTA is recommended for confirmation, and for added information on intracranial cerebral circulation and aortic arch condition for procedural planning. Over the past few decades, the focus of CAS diagnosis has also shifted from pure stenosis quantification to plaque characterization. This has led to further advancement in the existing imaging tools and development of other potential imaging tools like Optical coherence tomography (OCT), photoacoustic tomography (PAT), and infrared (IR) thermography.

Carotid Endarterectomy Based on Duplex Ultrasonography: A Safe Approach Associated with Long-term Stroke Prevention

To evaluate the short-term and long-term safety of carotid endarterectomy (CEA) based on duplex ultrasound without confirmatory diagnostic arteriography.

A 4-year retrospective review of CEA based on duplex ultrasound alone (n = 653) or with confirmatory arteriography (n = 118) was performed in 244 women and 458 men whose ages ranged from 39 to 92 years (mean, 70 years). Practice patterns, perioperative morbidity, and stroke rate (life-table analysis) of a community-based and university- based vascular surgical practice were analyzed and compared.

Surgical intervention based on duplex ultrasound was judged possible in 85% of the patients (community, 93%; university, 55%). Indications for arteriography included: testing completed prior to surgical consultation (44%), nonfocal extracranial carotid stenosis (23%), nonhemispheric symptoms (13%), and prior stroke (9%). This approach was safe (with a combined operative mortality and neurologic morbidity of 1.8%), asso ciated with long-term stroke prevention (a 95% stroke-free survival at 4 years), and yielded results similar to CEA with arteriography (operative morbidity, 2.6%; 91% stroke- free survival). The incidence and nature of late neurologic deficits were similar after CEA with and without arteriography. Twenty-three (4%) of the patients who underwent CEA based on duplex ultrasound developed late neurologic symptoms including 9 contralat eral and 4 ipsilateral strokes; and 4 ipsilateral and 4 contralateral transient ischemic attacks (TIAs). Cardiac embolism from atrial fibrillation accounted for 6 strokes, lacunar infarct associated with hypertension (3 strokes), intracranial atherosclerosis (3 strokes), and contralateral internal carotid artery (ICA) occlusion (1 stroke). Forty patients (6.8%) died predominantly from cardiac events. After CEA with arteriography 6 (5%) of the patients died. Six late strokes (4 contralateral, and 2 ipsilateral hemisphere) occurred as a result of progressive, untreated ICA stenosis (n = 3), and lacunar infarct (n = 3). Overall, 11% of the patients underwent contralateral CEA for progressive ICA stenosis.

CEA, based on duplex scanning, is safe and applicable for the majority of patients undergoing surgical evaluation. Short-term and long-term outcomes were similar to outcomes in patients having CEA based on diagnostic arteriography.

High Resolution Contrast-Enhanced MR Angiography in the Evaluation of Rabbit Carotid Artery

This study compared a high resolution contrast-enhanced MR angiography (MRA) sequence to conventional contrast-enhanced MRA sequence for imaging of rabbit carotid artery. Fifteen rabbits underwent an evaluation using both high resolution contrast-enhanced MRA sequence and conventional contrast-enhanced MRA sequence. Siemens 1.5 Tesla Magnetom Vision system was utilized. The parameters of high resolution sequence were: TR/TE= 6.2/2.0 msec, flip angle 25°, matrix 130×512, pixel size 0.96×0.49 mm, partition thickness 1.58 mm, acquisition time 24 sec. The parameters of conventional sequence were: TR/TE=3.8/1.4 msec, flip angle 35°, matrix 110×256, pixel size 1.48×1.02 mm, partition thickness 2mm, acquisition time 10 sec. Maximum intensity projection (MIP) images were created. Both original single slices and MIP images were used for image quality evaluation. Contrast-to-noise ratio (CNR), signal-to-noise ratio (SNR), distinctness of artery edge, and venous contamination were analyzed for both techniques. Higher average CNR and SNR were obtained with high resolution contrast-enhanced MRA, compared to average CNR and SNR with conventional contrast-enhanced MRA. The differences were statistically significant (P<0.01). The artery edge with high resolution method was more distinct than conventional method. Jugular venous contamination was found in five of 15 cases with high resolution contrast-enhanced MRA and in four of 15 cases with conventional contrast-enhanced MRA. High resolution contrast-enhanced MRA has significant potential for high quality noninvasive vascular imaging. The image quality with high resolution contrast-enhanced MRA sequence is better than conventional contrast-enhanced MRA sequence.

Gadolinium-Enhanced Versus Time-of-Flight Magnetic Resonance Angiography: What Is the Benefit of Contrast Enhancement in Evaluating Carotid Stenosis?

Accurate patient selection based on preoperative imaging is imperative to good risk reduction in patients undergoing carotid endarterectomy (CEA). The goal of this study was to assess the accuracy of gadolinium-enhanced magnetic resonance angiography (GE MRA) versus time-of-flight (TOF) MRA in the work-up of patients undergoing CEA. Patients undergoing CEA between 1999 and 2001 were identified from a prospectively maintained institutional database. GE or TOF MRA was obtained on extracranial carotid arteries (n = 319) in patients undergoing CEA. Stenosis on MRA images was graded as moderate (n = 76) or severe (n = 243) by an attending radiologist who was blind to duplex results. Duplex imaging was performed in an Intersocietal Commission for the Accreditation of Vascular Labs (ICAVL) accredited lab, and stenosis was stratified as moderate (50-79%, n = 76) or high (80-99%, n = 243) grade using University of Washington criteria. For each patient, the degree of stenosis as determined by MRA (GE versus TOF) was compared to percent stenosis on duplex. For moderate-grade lesions, GE MRA concurred with duplex in 11.1% (4/36), underestimated in 2.8% (1/36), and overestimated in 86.1% (31/36) of carotid arteries imaged. TOF MRA concurred with duplex in 35% (14/40), underestimated in 0% (0/40), and overestimated in 65% (26/40) of carotid arteries. High-grade lesions demonstrated improved concordance between MRA and duplex. For these lesions, GE MRA concurred with duplex in 95.6% (130/136) of carotid arteries imaged, never overestimated stenosis (0/136), and underestimated in 4.4% (6/136). TOF MRA concurred with duplex 96.3% (103/107), overestimated stenosis as an occlusion in 0.9% (1/107), and underestimated in 2.8% (3/107). In addition to neck visualization, the GE technique allowed simultaneous aortic arch imaging. This was accomplished in 79.1% (136/172) of all GE MRAs. Simultaneous aortic arch imaging was not technically feasible with TOF MRA. For moderate-grade lesions, both MR techniques are inaccurate predictors of degree of carotid stenosis and result in a significant overestimation of stenosis. Each technique demonstrates improved concordance with duplex ultrasound in the setting of severe carotid artery stenoses. The ability of GE MRA to simultaneously image the aortic arch and the neck may allow for detection of occult tandem lesions and other anatomic variations, which may be particularly important in preoperative planning for carotid artery stenting.

Evaluation of Classic 2D Time-of-Flight MR Angiography in the Depiction of Severe Carotid Stenosis

OBJECTIVE

The purpose of this study is to determine the sensitivity, specificity, and clinical utility of classic 2D time-of-flight MR angiography (acquired with derated gradients) as an aid to predicting severe carotid stenosis.

SUBJECTS AND METHODS

Our study population was composed of 68 patients, yielding 133 carotid bifurcations for analysis. A 2D time-of-flight MR angiography pulse sequence was modified to provide greater sensitivity for carotid stenosis, which resulted in visualization of a carotid stenosis with a 70% or greater diameter as a signal void. Contrast-enhanced MR angiography was performed with the elliptical centric view order. Multiple overlapping thin-slab acquisition (MOTSA) MR angiography was performed in select patients. Digital subtraction angiography was performed in 51 patients, and the findings were used as the gold standard. In the remaining patients, findings on carotid duplex Doppler sonography and at surgery and clinical follow-up were used as the gold standard.

RESULTS

In 51 patients for whom a digital subtraction angiogram was available, we found that the sensitivity of classic 2D time-of-flight MR angiography for prediction of carotid stenosis with a 70% or greater diameter was 94%, and the specificity of the technique was 97%. In three patients with severe carotid stenosis, the stenoses that appeared as signal voids on the classic 2D time-of-flight MR angiography were underestimated on contrast-enhanced MR angiography. Severe stenosis was confirmed by subsequent digital subtraction angiography, surgical results, or both. Discrepancies between findings on MOTSA MR angiography and contrast-enhanced MR angiography were resolved with classic 2D time-of-flight MR angiography. Classic 2D time-of-flight MR angiography increased diagnostic confidence of a severe stenosis in three patients with focal internal carotid artery stenosis.

CONCLUSION

Classic 2D time-of-flight MR angiography has a high sensitivity and specificity for predicting carotid bifurcation stenosis of 70% or greater diameter. These probability measures allowed the detection of three significant stenoses that would have been missed on contrast-enhanced MR angiography and provided greater diagnostic confidence than contrast-enhanced or MOTSA MR angiography alone.

[Correlation of diagnostic procedure with surgical findings in carotid stenosis]

Authors are discussing dilemma about necessary diagnostic procedure in making decision for surgical treatment of the carotid disease. Attitudes are changing and the old opinion of the necessity for angiogram of extra cranial blood vessels is substituted by the opinion that CDS (Color Duplex Scan) is satisfactory in the majority of cases to indicate of the surgical treatment. Comparing the invasive and noninvasive diagnostic's with operative findings, authors empirically confirm the given hypotheses, looking back to the cases where angiogram is necessary. The following issues were discussed: Estimate of the locaton of maximal shrinking, degree of shrinking, length of shrinking and characteristics of plaque as the most important parameters for indication and operative tactics. Diagnostics with CDS is shown as reliable with high degree of matching with operative findings.

Statistics-based approach for aneurysm volume measurements

PURPOSE

To evaluate the ability of high-resolution MRA to monitor changes in intracranial aneurysm volume, and devise a highly reliable technique for obtaining these measurements.

MATERIALS AND METHODS

To obtain a baseline estimate of the repeatability of MRA scans and validate the statistics-based technique for aneurysm volume measurement, multiple scans were obtained on individual subjects over a period of up to 1 year. These 3D MRA data sets were coregistered and then analyzed using the volumetric analysis of segmented data and the proposed statistical method.

RESULTS

It was shown that high-resolution MRA provides highly repeatable data sets. Both methods used for the aneurysm volume measurements showed consistent results. However, the proposed statistical method had lower error and was much less sensitive to the choice of segmentation parameter than the volumetric analysis of segmented data. A change of 1 mm in the average radius of the aneurysm was detectable with the statistics-based technique.

CONCLUSIONS

This study demonstrates that the statistical method of aneurysm volume measurement in high-resolution MRA allows reliable and accurate assessments of aneurysm volume changes.

Carotid endarterectomy then and now: outcome and cost-effectiveness of modern practice

BACKGROUND

During the past decade, our practice of performing carotid endarterectomy (CEA) has changed dramatically, most notably by an abrupt shift from routine to selective preoperative angiography, reliance on defined care plans with full-time nurse practitioner oversight, and increasing reliance on eversion endarterectomy and cervical block anesthesia. This study was designed to determine whether these shifts in policy have been associated with lower costs without sacrificing clinical outcome.

METHODS

All patients undergoing CEA from July 1993 to December 2000 were identified, and inpatient and outpatient charts were reviewed. Cost data were obtained from the central hospital accounting system and converted to 2001 dollars. Thirty-day outcomes and costs were quantified each year and compared between each of 2 temporally well-defined groups: those undergoing "routine" versus "selective" angiography and those cared for before and after defined patient care protocols were instituted.

RESULTS

A total of 1168 CEAs were analyzed. Thirty-day combined stroke and death rate was 3.1%, and no trends or significant differences over time were seen. From 1993 to 2000 the cost of CEA fell from $9302 to $6216 (P<.0002), and length of stay was reduced 1 full day (P=.005). Institution of "selective" angiography was associated with an immediate cost savings of approximately $2000 per case (P<.0001), and nurse practitioner oversight along with institution of defined clinical protocols with a $530 (P<.05) decline in nonoperating room-related costs.

CONCLUSIONS

Changes in policy from routine to selective angiography, reliance on defined postoperative care pathways, eversion endarterectomy, and cervical block anesthesia have been associated with significant cost savings, with no compromise in clinical outcome at our institution.

Improvement in accuracy of diagnosis of carotid artery stenosis with duplex ultrasound scanning with combined use of linear array 7.5 MHz and convex array 3.5 MHz probes: validation versus 489 arteriographic procedures

OBJECTIVE

Validity of a method to improve the accuracy of carotid artery duplex scanning was tested in comparison with arteriography.

STUDY DESIGN

In 489 patients who had not previously undergone arteriography, 978 carotid arteries were examined with duplex ultrasound scanning. In method A, a linear array 7.5 MHz transducer with pulsed-wave 4.7 MHz Doppler scanning was used. For the diagnosis and grading of carotid stenosis, peak systolic and end-diastolic velocity of the Doppler waves were recorded. Method B consisted of complete ultrasound imaging and color-flow mapping with a convex array 3.5 MHz transducer with pulsed-wave 2.8 MHz Doppler scanning in all patients who had previously undergone method A. Further velocity measurements were performed at the sites of stenosis. The results of methods A and B were compared with data from neurologic assessment and arteriographic studies.

RESULTS

Method B showed significantly higher diagnostic agreement with arteriography than did method A (K 95% confidence interval [CI], 0.87-0.93 vs 0.79-0.85; P <.05), and the number of mistakes in grading stenosis was significantly lower (primarily because of decreased overestimation) in patients with internal carotid kinking (>60 degrees of angulation) (P <.05), distal stenosis (>20 mm from bifurcation) (P <.01), or wide acoustic shadowing (>1 cm) (P <.01) and in those without these conditions (P <.05). Compared with arteriography, diagnostic accuracy with the new method proved higher for carotid stenoses 50% or greater, 60% or greater, 70% or greater, and 80% or greater; no statistically significant difference was found for carotid stenosis 96% or greater or for carotid occlusion. Compared with data from neurologic assessment and arteriography, method B proved more accurate than method A in designating patients for carotid endarterectomy (P =.014).

CONCLUSIONS

The new method significantly improved diagnostic reliability of duplex ultrasound scanning, especially in carotid arteries with kinking, distal stenosis, or wide acoustic shadowing (32.2% of all arteries studied). In clinical practice, we suggest additional use of a lower frequency transducer in cases in which these three conditions are found or suspected at first scanning.

Contrast-enhanced three-dimensional magnetic resonance angiography of atherosclerotic internal carotid stenosis as the noninvasive imaging modality in revascularization decision making

BACKGROUND AND PURPOSE

In patients with severe internal carotid artery stenoses, thromboendarterectomy significantly reduces both ischemic stroke and the risk of more ischemic attacks. Digital subtraction angiography (DSA) is the accepted preoperative test to determine whether a high-grade stenosis is present and requires surgical therapy. However, DSA has a procedural risk of stroke between 0.7% and 1%. An accurate, noninvasive imaging protocol with no risk of severe complications would significantly increase the benefit of surgical treatment. The aims of the study were (1) to evaluate the diagnostic accuracy of contrast-enhanced magnetic resonance angiography (CEMRA) in detecting and grading internal carotid artery stenoses and (2) to assess the misclassification rate of vessels suitable for revascularization by CEMRA.

METHODS

Ninety-two patients with sonographic evidence of neck vessel stenosis were enrolled in the study. All patients were submitted to CEMRA and DSA. CEMRA images were evaluated for the presence of mild, moderate, or severe stenosis and occlusion.

RESULTS

Sensitivity, specificity, and diagnostic accuracy were 97%, 82%, and 92.5%, respectively. Agreement with DSA was optimal at kappa=0.87. The misclassification rate of CEMRA was 3.1% because of its tendency to overestimate the stenosis.

CONCLUSIONS

The high diagnostic accuracy and limited misclassification rate suggest that CEMRA can be considered a powerful tool for the preoperative, noninvasive evaluation of atherosclerotic pathology of carotid arteries.

Utility of noninvasive studies in the evaluation of patients with carotid artery disease

Endarterectomy reduces the risk of stroke in selected patients with carotid artery stenosis, and the benefit is related to the degree of stenosis. Although the randomized trials demonstrating this benefit measured the degree of stenosis with conventional catheter angiography, many physicians are relying on noninvasive tests to select patients for surgery. Technologic advancement in this area is outpacing the availability of quality data supporting the clinical utility of the newer noninvasive tests.

Carotid artery endarterectomy solely based on duplex scan findings

The purpose of this study was to review experience with carotid artery surgery based on findings obtained solely from duplex scanning with special regard to unexpected findings during surgery and the early outcome. From January 1993 through December 1999, 271 consecutive patients underwent 287 carotid endarterectomies (CEAs), 229 (80%) of which were performed solely based on duplex scan findings. During the study period 5,932 carotid artery duplex scans were performed in 4,466 patients. Of 589 patients with internal carotid artery (ICA) stenosis 70%, 246 underwent CEA compared to 25 of 156 with 50-69% ICA stenosis. The indications for CEA were transient ischemic attack (TIA) in 88 (30.7%), amaurosis fugax in 60 (20.9%), previous stroke in 91 (31.7%) and asymptomatic disease in 48 (16.7%) cases. There were no statistically significant differences between the groups operated on with and without preoperative angiography with respect to the indications for surgery, associated risk factors, or the degree of stenosis on the contralateral side. In patients undergoing surgery without angiography, there were no unexpected findings that influenced the performance of surgery, in all except 1. There were no significant differences in perioperative morbidity and mortality in patients undergoing surgery with and without conventional angiography. The combined mortality and major stroke rates were 3.4% and 2.2%, respectively. It is concluded that CEA can safely be performed without preoperative angiography in cases with conclusive duplex scan findings.

Avaliação carotídea em doentes submetidos a revascularização miocárdica

OBJETIVO: Como a doença carotídea é a principal causa isolada de acidente vascular cerebral de origem tromboembólica, acredita-se ser imprescindível o seu diagnóstico precoce. O presente estudo tem por objetivo realizá-lo, mantendo os conceitos de praticidade e viabilidade econômica, adequando-se às condições socioeconômicas desfavoráveis locais. MÉTODO: No período de 18 meses foram avaliados 50 doentes, sendo 35 homens e 15 mulheres, com média de idade de 67,2 anos. Todos apresentavam indicação de revascularização miocárdica, considerados coronariopatas graves. Avaliou-se a incidência e o grau de estenose carotídea com base no mapeamento dúplex. Da mesma forma, foi avaliada a relação com possíveis fatores de risco: diabetes melito, hipertensão arterial sistêmica, tabagismo, sintomatologia neurológica focal prévia, doença arterial troncular dos membros inferiores e presença de sopro carotídeo. RESULTADOS: A incidência de estenose carotídea hemodinamicamente significativa (>50%) foi de 48%, e crítica (>70%) de 32%. Mostraram-se fatores de risco estatisticamente significativos, antecedentes de diabetes melito, sintomatologia neurológica focal prévia, presença de sopro carotídeo e presença de alterações arteriais tronculares dos membros inferiores. CONCLUSÃO: Concluiu-se que no grupo estudado houve aumento significativo de risco para estenose carotídea hemodinamicamente significativa e crítica, em relação à população geral. Desta forma, justifica-se o rastreamento ultra-sonográfico para doença carotídea em doentes coronariopatas, principalmente quando os fatores de risco significativos se fizerem presentes.

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.

Colour flow Doppler ultrasound of the carotid bifurcation: can it replace routine angiography before carotid endarterectomy?

The objective of this study was to assess the diagnostic accuracy of colour flow Doppler ultrasound (CFD) and its potential to replace digital subtraction angiography (DSA) before carotid endarterectomy (CEA). All patients undergoing CFD of the carotid bifurcation in our department over a period of 1-1/2 years for whom both CFD and DSA results were available were included in the study. We evaluated the feasibility of CFD, its diagnostic accuracy and its potential to diagnose clinically significant stenosis (50%, 70% and 90% NASCET type diameter stenosis) compared with DSA. 225 carotid bifurcations in 116 patients met the criteria for evaluation (biplane arterial DSA without superimposition). Data analysis yielded the following diagnostic performance of CFD: sensitivity for a 50% stenosis 91.4% (95% confidence interval (CI) 83.3--96.2%), specificity 93.2% (95% CI 87.1--96.8%) and accuracy 92.4% (95% CI 88.4--95.4%); sensitivity for a 70% stenosis 89.2% (95% CI 81.9--94.1%), specificity 96.2% (95% CI 90.5--98.6%) and accuracy 92.4% (95% CI 88.4--95.4%). In 9 of 116 cases, carotid angiography was used to evaluate inconclusive CFD results. DSA disclosed relevant information not suspected by CFD in only 1 of the 116 cases. Thus, 91% (106/116) of the angiographies could have been dispensed with without loss of information. One major stroke occurred during diagnostic DSA. We conclude that DSA of the carotid arteries is unnecessary when CFD is unequivocal. The diagnostic gain of DSA must be counterweighted against its potential risks.

Carotid arteriography impacts carotid stenosis management

Recent literature advocates carotid endarterectomy on duplex alone. The authors hypothesized that carotid angiography adds information that alters clinical management in a substantial number of patients compared to the use of carotid duplex examination alone. The records of 182 consecutive patients who underwent carotid artery duplex and subsequent carotid/cerebral angiography for suspected carotid artery stenosis between January 1998 and April 1999 were reviewed retrospectively. Carotid artery duplex examinations were stratified based on stenosis: < or =39%, 40% to 59%, 60% to 79% (moderate), 80% to 99% (severe), 100%. Carotid stenosis on angiograms was determined by NASCET criteria. New information found at angiography included vertebral, subclavian, or arch atherosclerosis, intracranial pathosis, or a change in duplex stenosis category to a degree of stenosis not requiring surgery. Clinical importance was attributed to angiograms that altered the patients' management plan. Angiography provided additional information in 53% (97/182) of patients. Vertebral disease was found in 25.1%, subclavian disease in 16.4%, intracranial disease in 15.3%, aortic arch disease in 3.3%. Patient treatment was altered in 30% (55/182). Angiographic findings downgraded the stenosis to medical therapy in 20.9% (38/182). The surgical plan was influenced in 5.5% (10/182). Nine intracranial aneurysms were discovered. Carotid angiography was essential for vascular bypass surgery planning in 3.3% (6/182). Angioplasty was performed in 2.2% (4/182). The accurate determination of stenosis is critical in determining optimal treatment of patients with carotid artery stenosis. Routine carotid angiography remains valuable in the clinical treatment of these patients.

Magnetic resonance angiography and evaluation of cervical arteries

Multiple clinical trials have demonstrated the efficacy of endarterectomy in selected groups of patients based primarily on percent diameter stenosis. Although measurement of stenosis in the clinical trials was established by conventional angiography, there is considerable interest in noninvasive alternatives. Magnetic resonance angiography, performed using time-of-flight methods or with contrast enhancement, is one of several alternatives for noninvasive carotid evaluation. Screening examinations are routinely performed for carotid stenosis. Preoperative evaluations based on one or a combination of noninvasive tests have been proposed, although these proposals are the subject of ongoing controversy. Evaluation of the vertebral arteries is more difficult and less well studied: however, the increasing availability of therapies for posterior circulation atherosclerotic narrowing is resulting in increased interest in this problem.

Carotid ultrasound

This article provides an overview of basic diagnostic carotid ultrasound applications, and emphasizes practical aspects of this examination. Areas currently being investigated include carotid plaque characterization and applications relative to IMT measurements. Contrast-enhanced ultrasound imaging also offers promise to improve plaque characterization, which in turn may link these evaluations to outcome studies.

Results of carotid endarterectomy performed with preoperative duplex ultrasound assessment alone

Contrast injection cerebral angiography has been considered for several decades the "gold-standard" technique for diagnosis and operative planning of carotid disease. More recently, however, an increasing number of institutions are using duplex ultrasound as the single independent preoperative test. The objective of this investigation was to evaluate the impact of the utilization of duplex ultrasonography as the only preoperative test on the outcome of the procedure. Between 1993 and 1996, the authors performed 1,149 carotid procedures. Duplex ultrasound as the only preoperative test was employed with increasing frequency in a total of 728 cases. In 1995 and 1996, a cerebral arteriogram was performed only if duplex ultrasound was technically inadequate or questionable or showed an atypical pattern of disease. During the 4 years analyzed in this study, the number of the procedures increased from 165 in 1993 to 412 in 1996. The thirty-day mortality rate was 0.43%, and neurologic morbidity was 1.65%. According to the year in which the procedure was performed, the mortality/morbidity rates were 1.2/2.4 in 1993, 0.52/2.08 in 1994, 0.26/1.57 in 1995, and 0.24/1.21 in 1996. Indication to perform an arteriogram became very selective in 1995. Regardless of these changes in the diagnostic work-up, some degree of reduction in both 30-day mortality and neurologic morbidity was recorded. Considering a cost of 724 European Currency Units (ECU) per arteriogram, 527,072 ECU were saved in this period. In the last 4 years, duplex ultrasound has replaced arteriography as the first-choice technique for preoperative assessment of carotid disease at the authors' institution. There was definitely no detrimental effect on the clinical results that, on the contrary, improved during the same period. This policy has allowed a significant reduction in the cost of the procedure and has most likely prevented several arteriography-related complications. The authors recommend this policy to all institutions in which accurate duplex ultrasound is available.

Validity of duplex ultrasound as a diagnostic modality for internal carotid artery disease

There is an increasing trend to rely on duplex ultrasound rather than angiography to measure an internal carotid artery stenosis. The aim of this study was to determine the validity of ultrasound assessment of carotid stenosis performed in community based vascular laboratories. We compared ultrasound with angiography in 225 patients referred to us for carotid intervention. Mild lesions were diagnosed by ultrasound with a sensitivity of 54%, specificity of 89%, and a positive predictive value of 89% compared with angiography. Severe lesions had a sensitivity of 93%, a specificity of 67%, and a positive predictive value of 45%. Receiver operator characteristic curves demonstrated the optimal ultrasound cut-off value of 66% stenosis as a predictor of >60% stenosis measured angiographically, is associated with a false positive rate of 38%, and a false negative rate of 9%. Similarly, if a cut-off of 76% on ultrasound is used to predict >70% stenosis measured angiographically, it would be associated with a 29% false positive rate and a false negative rate of 11%. Despite the value of non-invasive testing for carotid disease, duplex ultrasonography performed in non-accredited and some accredited laboratories may produce highly variable results. Using ultrasound as the sole diagnostic test to determine the severity of a carotid stenosis may result in a high number of inappropriate operations and a large proportion of patients who may not be offered treatment due to false negative diagnoses.

Power Doppler imaging: initial evaluation as a screening examination for carotid artery stenosis

PURPOSE

To evaluate power Doppler imaging as a possible screening examination for carotid artery stenosis.

MATERIALS AND METHODS

In the principal pilot study, a prospective, blinded comparison of power Doppler imaging with duplex Doppler imaging, the reference-standard method, was conducted in 100 consecutive patients routinely referred for carotid artery imaging at a large, private multispecialty clinic. In the validation pilot study, a prospective, blinded comparison of power Doppler imaging with digital subtraction angiography, the reference-standard method, was conducted in 20 consecutive patients routinely referred at a teaching hospital. Using conservative assumptions, the authors performed cost-effectiveness analysis.

RESULTS

Power Doppler imaging produced diagnostic-quality images in 89% of patients. When the images of the patients with nondiagnostic examinations were regarded as positive, power Doppler imaging had an area under the receiver operating characteristic curve, A(z), of 0.87, sensitivity of 70%, and specificity of 91%. The validation study results were very similar. The cost-effectiveness of screening and, as indicated, duplex Doppler imaging as the definitive diagnostic examination and endarterectomy was $47,000 per quality-adjusted life-year.

CONCLUSION

The A(z) value for power Doppler imaging compares well with that for mammography, a generally accepted screening examination, and with most other imaging examinations. Power Doppler imaging is likely to be a reasonably accurate and cost-effective screening examination for carotid artery stenosis in asymptomatic populations.

Carotid Artery Occlusive Disease

Stroke is the third most common cause of death and the leading cause of disability in the United States. Management of identifiable risk factors and careful selection of patients for operative intervention constitute the current approach to reducing the morbidity and mortality associated with stroke. A carefully performed carotid endarterectomy (CEA), which has a low periprocedural complication rate, is the only form of mechanical cerebral revascularization for which definitive evidence of clinical effectiveness has been reported. Recently, retrospective case reports and case series have demonstrated the feasibility of carotid angioplasty and stenting as a possible alternative to CEA. In the tradition of the two previous National Institutes of Health (NIH)-sponsored trials--the North American Symptomatic Carotid Endarterectomy Trial (NASCET) and Asymptomatic Carotid Atherosclerosis Study (ACAS)--the National Institutes of Health has sponsored a clinical trial (CREST: Carotid Revascularization-Endarterectomy vs Stent Trial) that is currently under way to determine the efficacy and risks of carotid angioplasty and stenting compared with CEA.

Carotid endarterectomy in octogenarians: comparison with patient characteristics and outcomes in younger patients

OBJECTIVES

Carotid endarterectomy has been shown to be of clear benefit to selected patients. However, recent trials of carotid endarterectomy versus best medical therapy have excluded octogenarians, and some authors have suggested that carotid endarterectomy would have an unfavorable cost-benefit relationship in octogenarians. We compared patients and results for carotid endarterectomy in octogenarians and younger patients.

METHODS

We reviewed the results for 582 primary carotid endarterectomies (90 in octogenarians and 492 in younger patients) performed in 528 patients between February 1, 1985, and January 31, 1998 (all data were collected prospectively for the most recent 301 carotid endarterectomies). Conventional surgical technique was used with general anesthesia, selective shunting, and selective patching. Main outcome measures were perioperative and late ipsilateral stroke and death.

RESULTS

The two groups were similar with respect to indications for carotid endarterectomy and patient characteristics, except that octogenarians were more likely to have histories of congestive heart failure or hypertension and less likely to have histories of smoking or chronic lung disease. Carotid endarterectomy was performed for asymptomatic disease in 27% of the octogenarians and 33% of the younger patients (P =.31). Stenosis was >/=80% in 90% of the octogenarians and 78% of the younger patients (P =.014). Perioperative strokes, all of which were ipsilateral, occurred in one octogenarian (1.1%) and eight younger patients (1.6%, P = 1.00). No octogenarians and two younger patients died within 30 days of surgery (P = 1.00). Length of stay and direct costs associated with carotid endarterectomy were similar for octogenarians and younger patients. Late strokes occurred in two octogenarians (one ipsilateral) and four younger patients (two ipsilateral). Life table estimates of freedom from ipsilateral stroke at 2 years were 98% and 97% for octogenarians and younger patients, respectively (log-rank P =.69), and life table estimates of patient survival at 4 years were 81% and 89% for octogenarians and younger patients, respectively (P =.11). Octogenarians represented an increasing fraction of the carotid endarterectomies performed during the study period.

CONCLUSIONS

Octogenarians selected for carotid endarterectomy were similar to younger patients with respect to indications for carotid endarterectomy and comorbidities. Early mortality, early and late neurologic outcome, complications, and resource utilization were similar for the two groups, and more than 75% of octogenarians survived 4 years after undergoing carotid endarterectomy. Cost-benefit analyses for carotid endarterectomy, which are highly sensitive to expected patient survival, might not be pertinent to individual patient situations. Intellectually intact octogenarians without unusually severe comorbidities are good candidates for and should be offered the benefits of carotid endarterectomy.

Surgical decision making for carotid endarterectomy and contemporary magnetic resonance angiography

BACKGROUND

Benefit from carotid endarterectomy (CEA) centers on patient selection and percent stenosis as determined by cerebral angiography. However, angiography remains expensive and poses risks. Validated carotid duplex ultrasonography has proven to be an accurate tool for selecting patients for CEA. However, the role of another noninvasive test-magnetic resonance angiography (MRA)-remains uncertain. Because of recent advances in MRA hardware and software, we hypothesized that clinically appropriate patients could be accurately selected for CEA based on MRA alone.

METHODS

Fifty-four carotid arteries in 29 patients (with and without symptoms) underwent both three-dimensional time-of-flight MRA (1.5 Tesla) with multiple overlapping thin slab acquisition and biplanar intra-arterial digital subtraction angiography. All patients undergoing both tests over a 24-month period were included. The majority of these patients did not undergo carotid duplex ultrasound owing to the clinical practice of the hospital's neurosurgery service. Staff radiologists interpreted each study. The accuracy of patient selection based on MRA was calculated using angiography as the standard (NASCET method). Since operative thresholds vary depending on clinical history, we considered four commonly used ranges of percent stenosis for CEA.

RESULTS

Patient selection accuracy of MRA alone was low, but increased as percent stenosis increased. Out of 10 occluded arteries by angiography, 5 were interpreted as patent with stenosis (70% to 99%) by MRA. One patent artery was misread as occluded on MRA.

CONCLUSION

Reliance solely on contemporary MRA for surgical decision making cannot be justified in view of low accuracy, which leads to high rates of error in patient selection for CEA.

New duplex ultrasound scan criteria for managing symptomatic 50% or greater carotid stenosis

PURPOSE

The North American Symptomatic Carotid Endarterectomy Trial (NASCET) showed that selected patients benefited from surgery when their carotid artery was 50% or more stenosed. This study assessed the accuracy of color-flow duplex ultrasound scanning (DUS) parameters to detect 50% or greater carotid artery stenosis and to determine the situations in which carotid endarterectomy (CEA) without angiography could be justified.

METHODS

From March 1, 1995, to December 1, 1995, all patients considered for CEA were studied with DUS and carotid angiography. Results of the two tests were blindly compared. DUS measurements of internal carotid artery (ICA) peak systolic velocity (PSV), end diastolic velocity, and ratio of the ICA to common carotid artery PSV (ICA/CCA) were subjected to receiver operator characteristic curve analysis to determine the most accurate criterion predicting 50% or greater angiographic stenosis. The criterion for identifying patients for CEA without angiography was selected from criteria with a high positive predictive value (PPV) and sensitivity.

RESULTS

A total of 188 carotid bifurcations were available for comparison. A PSV (ICA/CCA) of 2 or higher was the most accurate criterion for detection of 50% or greater stenosis, with an accuracy rate of 93% (sensitivity, 96%; specificity, 89%; PPV, 92%). A PSV (ICA/CCA) of 3.6 or higher was the best criterion for identifying candidates for CEA who had not undergone earlier angiography, with PPV, sensitivity, specificity, and accuracy rates of 98%, 77%, 98%, and 86%, respectively.

CONCLUSION

These redefined criteria detect the NASCET-defined threshold level of 50% or greater ICA stenosis, above which CEA results in stroke reduction. A management algorithm based on these criteria should help to minimize both angiography and unnecessary intervention.

Standardization of carotid ultrasound: a hemodynamic method to normalize for interindividual and interequipment variability

BACKGROUND AND PURPOSE

Accurate carotid Doppler examination is an important issue in the light of large endarterectomy trials, but recommended cutoff values for detection of >70% stenosis vary widely. Standardization of diagnostic criteria should consider patient variation and instrument variability.

METHODS

We prospectively analyzed various Doppler parameters in 44 patients undergoing carotid angiography to evaluate whether normalization through individual reference measurements from the common carotid artery or the distal internal carotid artery could improve accuracy. For assessment of interindividual and interequipment variability, we performed repeated measurements of 40 carotid arteries in 21 patients. Two color-coded duplex ultrasound systems were compared for machine variability estimation: Hewlett Packard SONOS 2500 and ATL Ultramark 9 HDI.

RESULTS

Intrastenotic divided by distally recorded mean blood flow velocity (mean velocity ratio) showed the closest correlation with angiography: R2=0.93. Mean velocity ratio >5 was 97% sensitive and 98% specific for detection of >70% carotid stenosis. Intrastenotic blood flow velocities were significantly different between the 2 duplex systems (0.22+/-0.16 versus 0.17+/-0. 11 m/s; P<0.001), whereas mean velocity ratio values did not differ significantly. Interobserver variation expressed as 95% CI for predicted stenosis between 2 observers was 13.6% (peak systolic velocity) and 15.4% (mean velocity ratio).

CONCLUSIONS

A mean velocity ratio using distal reference measurement in the internal carotid artery can normalize for interindividual and interequipment variability.

Colour-coded duplex sonography of preocclusive carotid stenoses

OBJECTIVE

The accuracy of colour-coded duplex sonography (CCDS) for differentiating preocclusive stenoses from occlusions of the internal carotid artery (ICA) is a crucial point in non-invasive quantification of atherosclerotic lesions prior to carotid endarterectomy.

METHODS

A total of 401 consecutive patients with CCDS followed by ICA arteriographies as gold standard was available for comparison. The entire number was divided into groups of <90%, 90-94%, preocclusive (95-99%) stenoses and occlusions. Sensitivity, specificity, and predictive value for distinguishing these groups were calculated using a contingency table.

RESULTS

With CCDS we found a sensitivity of 88% and a specificity of 99% in 43 preocclusive ?95% stenoses. Similar findings were seen in 31 occlusions of the ICA (SE 87%, SP 99%). CCDS accurately differentiates the subgroups of severe carotid obstructions (90-94%, ?95% and occluded) shown by a predictive accuracy of 97, 96 and 93%. Carotid endarterectomies were performed in two of three angiographically occluded but sonographically preocclusive arteries. Intraoperatively preocclusive ICAs were seen in both cases.

CONCLUSION

CCDS showed a high accuracy for differentiating preocclusive stenoses and occlusion of the ICA. Intraoperative findings indicated that angiography is not the absolute gold standard for preocclusive carotid disease in every case. Irregularities of the stenosis channel make it impossible to estimate the true area reduction in stenoses ?90%. The hemodynamic estimation of degree of stenosis by Doppler ultrasound may be closer to reality than angiographic measurement.

Spiral CT: vascular applications

Recent technical advances in CT have renewed interest in the development of CT angiography (CTA). CT angiography is a minimally invasive method of visualising the vascular system and is becoming an alternative to conventional arteriography in some situations. Spiral technology allows a volume of data to be obtained on a single breath-hold with no respiratory misregistration. Fast machines with second or subsecond acquisition times mean the images are obtained while there are high circulating levels of contrast medium giving peak vascular opacification from a peripheral intravenous injection. Accurate timing will ensure either the arterial or venous phase is imaged. Multiple overlapping axial images can be obtained from the data set with no increase in radiation dose to the patient and from these scans computer generated multiplanar and 3D images are obtained which can be viewed from numerous angles. CT angiography can be performed more quickly, less invasively and at reduced cost compared to conventional angiography.

Determination of 60% or greater carotid stenosis: a prospective comparison of magnetic resonance angiography and duplex ultrasound with conventional angiography

The morbidity and cost of conventional angiography (CA) have focused recent efforts in cerebrovascular imaging upon the exclusive use of noninvasive techniques. Our purpose was to prospectively evaluate carotid magnetic resonance angiography (MRA) and to compare its accuracy with color-flow duplex (CFD). Fifty patients were prospectively evaluated with CA and MRA after clinical and CFD findings indicated the need for carotid angiography. CFD measurements of peak systolic velocity (PSV) and end-diastolic velocity (EDV) were made. MRA results were categorized as 0%-39%, 40%-59%, 60%-79%, or 80%-99% stenosis or occluded. Determination of percent carotid stenosis by CA was made as in the North American Symptomatic Carotid Endarterectomy Trial (NASCET). Using receiver operating characteristic (ROC) curves, the probability of correctly predicting a > or =60% stenosis using various CFD thresholds and MRA was assessed. Sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV) in determining > or =60% stenosis were estimated. For MRA the sensitivity was 85% (95% Confidence Interval [CI] = 69%-94%), specificity 70% (CI = 56%-81 %), PPV 68% (CI = 53%-80%), and NPV 86% (CI = 72%-94%). For CFD the sensitivity was 89% (CI = 74%-96%), specificity 93% (CI = 82%-98%), PPV 89% (CI = 74%-96%), and NPV 93% (CI = 82%-98%). When MRA and CFD results were concordant (n = 64), the sensitivity was 100% (CI = 89%-100%), specificity 95% (CI = 81%-99%), PPV 94% (CI = 77%-99%), and the NPV was 100% (CI = 92%-100%). The area under the ROC curve for CFD was 95%, compared to 83% for MRA (p = 0.0005). We conclude that the low specificity of MRA precludes its use as the definitive imaging modality for carotid stenosis. The 93% specificity of CFD alone warrants its consideration as a definitive carotid imaging study. By ROC curve analysis, CFD offers superior accuracy to MRA. Our data support noninvasive preoperative carotid imaging for detecting a threshold stenosis of > or =60% whether CFD is used alone, or in combination with the selective use of MRA.

Cost savings associated with the nonroutine use of carotid angiography

BACKGROUND

To evaluate the economic impact of performing carotid endarterectomy based only on a diagnosis of duplex scanning, we evaluated a cohort of patients treated at our institution during 1 calendar year.

METHODS

Ninety-seven patients were evaluated and divided into two groups: those with and without arteriogram prior to their operation. Duplex scan and arteriogram results were reviewed to determine their effect on the operative plan. Hospital charges and physician fees were assessed for each patient admission. Operative results, complications, and total charges were compared between the two groups.

RESULTS

There was one operative stroke in each group for a stroke rate of 2%. Angiographic complications included one stroke and one femoral artery thrombosis. Two arteriograms led to a change in the operative plan. The hospital charges for patients without an arteriogram was $10,292 verses $13,906 for patients with an arteriogram (P < 0.01). Physician charges for patients without an arteriogram were $3,882, with angiograms and $6,297. The total charges related to the endarterectomy were $14,174 and $20,203, respectively. Arteriograms accounted for an increase of 43% in total charges.

CONCLUSION

Nonroutine use of angiography does not increase operative risk or postoperative length of stay, and preoperative angiography increases total charges by 43% ($6,029) per patient.

Safe and cost-effective approach to carotid surgery

OBJECTIVE

To evaluate the safety and cost effectiveness of carotid surgery performed altering the perioperative protocol in an attempt to decrease resource utilisation.

SETTING

Department of vascular surgery in a large metropolitan teaching hospital in northern Italy.

DESIGN

Prospective, non-selective study.

MATERIALS AND METHODS

Three hundred and eighty carotid procedures were performed in 1995 on 343 patients (274 males, 69 females, mean age 68.2 years, range 47-86 years). The most important cost containment measures, were: (i) limiting the use of contrast arteriography to cases of dubious ultrasonographic diagnosis; (ii) routine use of loco-regional anaesthesia; (iii) postoperative admission to an intensive care unit (ICU) only in selected cases; (iv) early postoperative discharge where possible.

RESULTS

Mortality was 0.26% and neurological morbidity 1.58%. General anaesthesia was required in eight patients (2.1%), and only seven patients (1.8%) were admitted postoperatively to the ICU. Arteriography was performed in 56 cases (14.7%). The average hospital stay was 5 days with a global cost of 43,036 ECU, as compared with a cost of 6764 ECU for patients treated traditionally with routine arteriography, general anaesthesia and routine ICU admission.

CONCLUSIONS

Selective use of arteriography and ICU, routine use of loco-regional anaesthesia and reduced hospital stay make it possible to lower the cost of carotid surgery without sacrificing quality.

Does carotid duplex imaging render angiography redundant before carotid endarterectomy?

Carotid duplex imaging is now recognized as the best non-invasive screening test for carotid artery stenosis. The evidence for its use as the sole diagnostic imaging modality prior to carotid endarterectomy is examined. Providing it is carried out by experienced trained operators using validated duplex criteria, carotid duplex imaging is safe, highly sensitive and specific, and superior to angiography at plaque characterization and evaluation of flow disturbance. Cerebral CT or MRI should be performed if symptoms are atypical or if there is an evolved stroke. Angiography is required when duplex imaging is suboptimal or equivocal, in the presence of atypical symptoms or uncommon vascular abnormalities. In the majority of patients requiring endarterectomy for symptomatic high grade ICA stenosis, angiography seldom adds relevant information, and clinical assessment and carotid duplex imaging alone can be safely used in preoperative assessment.

Cost-effectiveness of carotid endarterectomy in asymptomatic patients

PURPOSE

The purpose of this study was to determine the cost-effectiveness of carotid endarterectomy for treating asymptomatic patients with > or = 60% internal carotid stenosis, based on outcomes reported in the Asymptomatic Carotid Atherosclerosis Study (ACAS).

METHODS

A cost-effectiveness analysis was performed using a Markov decision model in which the probabilities for base-case analysis (average age, 67 years; 66% male; perioperative stroke plus death rate, 2.3%; ipsilateral stroke rate during medical management, 2.3% per year) were based on ACAS. The model assumed that patients who had TIAs or minor strokes during medical management crossed over to surgical treatment, and used the NASCET data to model the outcome of these now-symptomatic patients. Average cost of surgery ($8500), major stroke ($34,000 plus $18,000 per year), and other costs were based on local cost determinations plus a review of the published literature. Cost-effectiveness was calculated as the incremental cost of surgery per quality-adjusted life year (QALY) saved when compared with medical treatment, discounting at 5% per year. Sensitivity analysis was performed to determine the impact of key variables on cost-effectiveness.

RESULTS

In the base-case analysis, surgical treatment improved quality-adjusted life expectancy from 7.87 to 8.12 QALYs, at an incremental lifetime cost of $2041. This yielded an incremental cost-effectiveness ratio of $8,000 per QALY saved by surgical compared with medical treatment. The high cost of care after major stroke during medical management largely offset the initial cost of endarterectomy in the surgical group. Furthermore, 26% of medically managed patients eventually underwent endarterectomy because of symptom development, which also decreased the cost differential. Sensitivity analysis demonstrated that the relative cost of surgical treatment increased substantially with increasing age, increasing perioperative stroke rate, and decreasing stroke rate during medical management.

CONCLUSION

For the typical asymptomatic patient in ACAS with > or = 60% carotid stenosis, our results indicate that carotid endarterectomy is cost-effective when compared with other commonly accepted health care practices. Surgery does not appear cost-effective in very elderly patients, in settings where the operative stroke risk is high, or in patients with very low stroke risk without surgery.