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

Extra-Cranial Carotid Artery Stenosis: An Objective Analysis of the Available Evidence

Background and Purpose

Carotid stenosis is arterial disease narrowing of the origin of the internal carotid artery (main brain artery). Knowing how to best manage this is imperative because it is common in older people and an important cause of stroke. Inappropriately high expectations have grown regarding the value of carotid artery procedures, such as surgery (endarterectomy) and stenting, for lowering the stroke risk associated with carotid stenosis. Meanwhile, the improving and predominant value of medical intervention (lifestyle coaching and medication) continues to be underappreciated.

Methods and Results

This article aims to be an objective presentation and discussion of the scientific literature critical for decision making when the primary goal is to optimize patient outcome. This compilation follows from many years of author scrutiny to separate fact from fiction. Common sense conclusions are drawn from factual statements backed by original citations. Detailed research methodology is given in cited papers. This article has been written in plain language given the importance of the general public understanding this topic. Issues covered include key terminology and the economic impact of carotid stenosis. There is a summary of the evidence-base regarding the efficacy and safety of procedural and medical (non-invasive) interventions for both asymptomatic and symptomatic patients. Conclusions are drawn with respect to current best management and research priorities. Several "furphies" (misconceptions) are exposed that are commonly used to make carotid stenting and endarterectomy outcomes appear similar. Ongoing randomized trials are mentioned and why they are unlikely to identify a routine practice indication for carotid artery procedures. There is a discussion of relevant worldwide guidelines regarding carotid artery procedures, including how they should be improved. There is an outline of systematic changes that are resulting in better application of the evidence-base.

Conclusion

The cornerstone of stroke prevention is medical intervention given it is non-invasive and protects against all arterial disease complications in all at risk. The "big" question is, does a carotid artery procedure add patient benefit in the modern era and, if so, for whom?

Older age and duration of exposure to type 2 diabetes in selective screening of asymptomatic carotid artery stenosis for primary stroke prevention-A single institution experience

AIMS

To evaluate the incidence and risk factors for carotid artery stenosis amongst asymptomatic type 2 diabetes from a single Malaysian tertiary institution.

METHODS

This is a prospective cross-sectional study of asymptomatic type 2 diabetics selected from the outpatient ophthalmology and endocrine clinics for carotid duplex ultrasound scanning performed by a single radiologist. The duplex ultrasound criteria were based on the North American Symptomatic Carotid Endarterectomy Trial (NASCET) classification of carotid artery stenosis. Univariate and multivariate analysis was performed to identify possible risk factors of carotid artery stenosis.

RESULTS

Amongst the 200 patients, the majority were males (56%) and Malay predominance (58.5%). There were 12/200 patients (6%) with mean age of 69.2 years identified to have carotid artery stenosis. Univariate analysis of patients with asymptomatic carotid artery stenosis identified older age of 69.2 years (p=0.027) and duration of exposure to diabetes of 17.9 years (p=0.024) as significant risk factors.

CONCLUSION

Patients with longer exposure of diabetes and older age were risk factors of carotid artery stenosis in asymptomatic type 2 diabetics. These patients should be considered for selective screening of carotid artery stenosis during primary care visit for early identification and closer surveillance for stroke prevention.

Validation of Risk Prediction Models to Detect Asymptomatic Carotid Stenosis

Background Significant asymptomatic carotid stenosis (ACS) is associated with higher risk of strokes. While the prevalence of moderate and severe ACS is low in the general population, prediction models may allow identification of individuals at increased risk, thereby enabling targeted screening. We identified established prediction models for ACS and externally validated them in a large screening population. Methods and Results Prediction models for prevalent cases with ≥50% ACS were identified in a systematic review (975 studies reviewed and 6 prediction models identified [3 for moderate and 3 for severe ACS]) and then validated using data from 596 469 individuals who attended commercial vascular screening clinics in the United States and United Kingdom. We assessed discrimination and calibration. In the validation cohort, 11 178 (1.87%) participants had ≥50% ACS and 2033 (0.34%) had ≥70% ACS. The best model included age, sex, smoking, hypertension, hypercholesterolemia, diabetes mellitus, vascular and cerebrovascular disease, measured blood pressure, and blood lipids. The area under the receiver operating characteristic curve for this model was 0.75 (95% CI, 0.74-0.75) for ≥50% ACS and 0.78 (95% CI, 0.77-0.79) for ≥70% ACS. The prevalence of ≥50% ACS in the highest decile of risk was 6.51%, and 1.42% for ≥70% ACS. Targeted screening of the 10% highest risk identified 35% of cases with ≥50% ACS and 42% of cases with ≥70% ACS. Conclusions Individuals at high risk of significant ACS can be selected reliably using a prediction model. The best-performing prediction models identified over one third of all cases by targeted screening of individuals in the highest decile of risk only.

Misconceptions regarding the adequacy of best medical intervention alone for asymptomatic carotid stenosis

BACKGROUND

Medical intervention (risk factor identification, lifestyle coaching, and medication) for stroke prevention has improved significantly. It is likely that no more than 5.5% of persons with advanced asymptomatic carotid stenosis (ACS) will now benefit from a carotid procedure during their lifetime. However, some question the adequacy of medical intervention alone for such persons and propose using markers of high stroke risk to intervene with carotid endarterectomy (CEA) and/or carotid angioplasty/stenting (CAS). Our aim was to examine the scientific validity and implications of this proposal.

METHODS

We reviewed the evidence for using medical intervention alone or with additional CEA or CAS in persons with ACS. We also reviewed the evidence regarding the validity of using commonly cited makers of high stroke risk to select such persons for CEA or CAS, including markers proposed by the European Society for Vascular Surgery in 2017.

RESULTS

Randomized trials of medical intervention alone versus additional CEA showed a definite statistically significant CEA stroke prevention benefit for ACS only for selected average surgical risk men aged less than 75 to 80 years with 60% or greater stenosis using the North American Symptomatic Carotid Endarterectomy Trial criteria. However, the most recent measurements of stroke rate with ACS using medical intervention alone are overall lower than for those who had CEA or CAS in randomized trials. Randomized trials of CEA versus CAS in persons with ACS were underpowered. However, the trend was for higher stroke and death rates with CAS. There are no randomized trial results related to comparing current optimal medical intervention with CEA or CAS. Commonly cited markers of high stroke risk in relation to ACS lack specificity, have not been assessed in conjunction with current optimal medical intervention, and have not been shown in randomized trials to identify those who benefit from a carotid procedure in addition to current optimal medical intervention.

CONCLUSIONS

Medical intervention has an established role in the current routine management of persons with ACS. Stroke risk stratification studies using current optimal medical intervention alone are the highest research priority for identifying persons likely to benefit from adding a carotid procedure.

Type-2 diabetes and carotid stenosis: a proposal for a screening strategy in asymptomatic patients

The objective of this prospective observational study was to establish the prevalence of carotid atherosclerosis in an asymptomatic diabetic population and to determine predictive factors for a screening optimization. A total of 300 consecutive type-2 diabetic subjects (166 males, 134 females) underwent a physical examination and duplex carotid scanning. Patients with a recent cerebrovascular event (±6 weeks) or previous carotid surgery were excluded. The prevalence of carotid stenosis ≥60% or occlusion was 4.7%; the prevalence of carotid atherosclerosis was 68.3%. Risk factors for stenosis ≤60% or occlusion were the presence of diabetic retinopathy (OR: 3.62; 95% CI: 1.12-11.73), ankle-brachial index (ABI) <0.85 (OR: 3.94; 95% CI: 1.21-12.84) and a personal history of neurological disorders (OR: 4.54; 95% CI: 1.16-17.81). Being female was a protective factor (OR: 0.09; 95% CI: 0.01-0.78). The two factors in the analysis limited to the male population were an ABI < 0.85 (OR: 3.66; 95% CI: 1.04-12.84) and a personal history of coronary heart disease (OR: 3.34; 95% CI: 1.01-11.01). If male diabetics without either of these two factors are excluded, the negative predictive value for carotid stenosis is 96.6%. In conclusion, the prevalence of atherosclerotic carotid disease in diabetic patients is high. In these patients, the probability of finding >60% stenosis is highest among men with a history of coronary heart disease or an ABI <0.85.

Attitudes of Canadian and U.S. Neurologists Regarding Carotid Endarterectomy for Asymptomatic Stenosis

Background:

The American Heart Association carotid endarterectomy (CE) guidelines endorse CE for asymptomatic carotid stenosis if the procedure can be performed with low morbidity. However, the Canadian Stroke Consortium has published a consensus against CE for asymptomatic stenosis. The views of practicing neurologists in the two countries on this subject are unclear.

Methods:

A survey was undertaken of 270 neurologists from either Florida or Indiana and 180 neurologists from either Ontario or Quebec.

Results:

The survey was returned by 36% of neurologists. Both Florida (65%) and Indiana neurologists (35%) were significantly more likely than Canadian neurologists (11%) to sometimes/often refer patients for surgery(p<0.001). Neurologists from Florida relied more on noninvasive methods of carotid stenosis assessment (36%) than Canadian neurologists (12%, p=0.003), who preferred angiography. Neurologists from Florida more often cited medicolegal concerns as a reason for referring patients for surgery (27%), compared to Canadian neurologists (3%, p=0.0001).

Conclusions:

Practices pertaining to carotid stenosis evaluation and management differ both regionally and by country. Canadian neurologists refer fewer asymptomatic patients for CE and rely more on angiography as a preoperative diagnostic tool. The potential of medicolegal liability is a greater force in clinical decision-making for certain U.S. neurologists, compared to their Canadian counterparts. These differences may partly explain the variations in CE utilization in the two countries.

What Should We Do with Asymptomatic Carotid Stenosis?

The benefit of prophylactic carotid endarterectomy (CEA) for patients with asymptomatic severe carotid stenosis in the major randomised surgical studies was small, expensive and may now be absorbed by improvements in best practice medical intervention. Strategies to identify patients with high stroke risk are needed. If surgical intervention is to be considered the complication rates of individual surgeons should be available. Clinicians will differ in their interpretation of the same published data. Maintaining professional relationships with clinicians from different disciplines often involves compromise. As such, the management of a patient will, in part, depend on what kind of specialist the patient is referred to. The clinician's discussion with patients about this complex issue must be flexible to accommodate differing patient expectations. Ideally, patients prepared to undergo surgical procedures should be monitored in a trial setting or as part of an audited review process to increase our understanding of current practice outcomes.

Frequency and Risk Factors for Cerebral Arterial Disease in a HIV/AIDS Neuroimaging Cohort

BACKGROUND

Infection with HIV predisposes patients to a myriad of neurologic disorders, including cerebrovascular disease. The pathophysiology is likely multifactorial, with proposed mechanisms including infectious vasculitis, HIV-induced endothelial dysfunction and adverse effects of combination antiretroviral therapy (cART). Epidemiologic data on clinically evident cerebral vasculopathy in HIV-infected adults is scarce, even though stroke hospitalizations are rising in this patient population.

METHODS

A total of 6,298 HIV-infected adults (San Francisco General Hospital, 2000-2013) were screened to generate a cohort of patients with dedicated neuroimaging of the intra- and extracranial cerebral vasculature. We extracted information regarding the extent of HIV disease (including serial viral load and CD4 counts), cardiovascular disease risk factors and exposure to cART (cross-referenced with pharmacy records) and performed multivariate logistic regression analysis to identify predictors of vasculopathy.

RESULTS

Of 144 patients, 55 patients (38.2%) had radiographic evidence of cerebral vasculopathy. Twenty (13.9%) had a vasculopathy characterized by vessel dolichoectasia and intracranial aneurysm formation. Thirty-five patients (24.3%) had intra- and or extracranial stenosis/occlusion. cART use (OR 2.27, 95% CI 1.03-5) and tobacco abuse (OR 2.35, 95% CI 1.04-5.25) were independently associated with the development of any vasculopathy, whereas cART use was also an independent risk factor for the stenosis/occlusion subtype specifically (OR 2.87, 95% CI 1.11-7.45).

CONCLUSIONS

There was a high frequency of cerebral arterial disease in this neuroimaging cohort of HIV/AIDS patients. A history of cART use and a history of tobacco abuse were independent risk factors for vasculopathy, though these findings should be confirmed with large-scale prospective studies.

Management of extracranial carotid artery disease

Stroke is the third leading cause of death in developed nations. Up to 88% of strokes are ischemic in nature. Extracranial carotid artery atherosclerotic disease is the third leading cause of ischemic stroke in the general population and the second most common nontraumatic cause among adults younger than 45 years. This article provides comprehensive, evidence-based recommendations for the management of extracranial atherosclerotic disease, including imaging for screening and diagnosis, medical management, and interventional management.

Geographic variation and trends in carotid imaging among medicare beneficiaries, 2001 to 2006

BACKGROUND

Diagnostic imaging among Medicare beneficiaries is an important contributor to rising health care costs. We examined temporal trends and geographic variation in the use of carotid ultrasound, carotid magnetic resonance angiography (MRA), and carotid x-ray angiography.

METHODS AND RESULTS

Analysis of a 5% national sample of claims from the Centers for Medicare and Medicaid Services for 1999 through 2006. Patients were 65 years or older and underwent carotid ultrasound, carotid MRA, carotid x-ray angiography, or a carotid intervention. The main outcome measures were annual age-adjusted rates of carotid imaging and interventions and factors associated with the use of carotid imaging. Rates of imaging increased by 27%, from 98.2 per 1000 person-years in 2001 to 124.3 per 1000 in 2006. Rates of carotid ultrasound increased by 23%, and rates of MRA increased by 66%. Carotid intervention rates decreased from 3.6 per 1000 person-years in 2001 to 3.1 per 1000 person-years in 2006. In 2006, rates of carotid ultrasound were lowest in the New England, Mountain, and West North Central regions and highest in the Middle Atlantic and South Atlantic regions. Regional differences persisted after adjustment for patient demographic characteristics, history of vascular disease and other comorbid conditions, and study year.

CONCLUSIONS

From 2001 through 2006, there was substantial growth and variation in the use of carotid imaging, including a marked increase in the use of MRA, and a decrease in the overall rate of carotid intervention.

Analysis of recently identified dyslipidemia alleles reveals two loci that contribute to risk for carotid artery disease

Background

Genome-wide association studies have identified numerous single nucleotide polymorphisms (SNPs) affecting high density lipoprotein (HDL) or low density lipoprotein (LDL) cholesterol levels; these SNPs may contribute to the genetic basis of vascular diseases.

Results

We assessed the impact of 34 SNPs at 23 loci on dyslipidemia, key lipid sub-phenotypes, and severe carotid artery disease (CAAD) in a case-control cohort. The effects of these SNPs on HDL and LDL were consistent with those previously reported, and we provide unbiased estimates of the percent variance in HDL (3.9%) and LDL (3.3%) explained by genetic risk scores. We assessed the effects of these SNPs on HDL subfractions, apolipoprotein A-1, LDL buoyancy, apolipoprotein B, and lipoprotein (a) and found that rs646776 predicts apolipoprotein B level while rs2075650 predicts LDL buoyancy. Finally, we tested the role of these SNPs in conferring risk for ultrasonographically documented CAAD stenosis status. We found that two loci, chromosome 1p13.3 near CELSR2 and PSRC1 which contains rs646776, and 19q13.2 near TOMM40 and APOE which contains rs2075650, harbor risk alleles for CAAD.

Conclusion

Our analysis of 34 SNPs contributing to dyslipidemia at 23 loci suggests that genetic variation in the 1p13.3 region may increase risk of CAAD by increasing LDL particle number, whereas variation in the 19q13.2 region may increase CAAD risk by promoting formation of smaller, denser LDL particles.

Development, validation, and application of a microsimulation model to predict stroke and mortality in medically managed asymptomatic patients with significant carotid artery stenosis

OBJECTIVE

To develop a model to predict stroke-free survival and mortality over a multiyear time frame for a trial-excluded population of medically managed asymptomatic patients with significant carotid artery stenosis.

METHODS

We calibrated, validated, and applied a Monte Carlo microsimulation model. For calibration we adjusted general-population mortality and stroke risks to capture these risks specific to asymptomatic carotid stenosis patients. For validation, we compared model-predicted and actual stroke-free survival curves and stroke counts from a population of comparable patients. For application, the validated model predicted stroke-free survival for a hypothetical medically managed arm of a recent single-arm carotid revascularization trial.

RESULTS

For each month in the 60-month time frame, the model-predicted and actual calibration trial stroke-free survival curves were not statistically different (P > 0.62). In validation, the calibrated model's stroke-free survival curvematched the actual curve from an independent population; beyond 24 months, the model-predicted and actual curves were not statistically different (P > 0.32). We also compared model-predicted and actual number of strokes from the independent trial. The model predicted 187.25 strokes (95% confidence interval 161.49-213.01), while the actual number was 171.6, within 1.22 standard deviations of the simulated mean.

CONCLUSIONS

Given the absence of medically managed populations in recent carotid stenosis trials, our model can estimate stroke-free survival and mortality data for these patients. The model may also estimate the effectiveness of novel medical and procedural therapies for stroke prevention. These effectiveness estimates can inform the development of policies, guidelines, or cost-effectiveness analyses when only single-arm trial data exist.

Guidelines for Screening of Extracranial Carotid Artery Disease: A Statement for Healthcare Professionals from the Multidisciplinary Practice Guidelines Committee of the American Society of Neuroimaging; Cosponsored by the Society of Vascular and Interventional Neurology

The aim of this new statement is to provide comprehensive and timely evidence-based recommendations on the screening for asymptomatic carotid artery stenosis in the general population and selected subsets of patients. Recommendations are included for high-risk persons in the general population; patients undergoing open heart surgery including coronary artery bypass surgery; patients with peripheral vascular diseases, abdominal aortic aneurysms, and renal artery stenosis; patients after radiotherapy for head and neck malignancies; patients following carotid endarterectomy, or carotid artery stent placement; patients with retinal ischemic syndromes; patients with syncope, dizziness, vertigo or tinnitus; and patients with a family history of vascular diseases and hyperhomocysteinemia. The recommendations are based on prevalence of disease, anticipated benefit, and concurrent guidelines from other professional organizations in selected populations.

When should ultrasonography be used to detect asymptomatic carotid atheroma in diabetic patients?

INTRODUCTION

While guidelines for detection of silent myocardial and lower limb ischemia are established, data on screening asymptomatic carotid lesions remain scarce. However, such screening would be costly. Since the prevalence of diabetes increases constantly, it is necessary to keep screening costs low by setting up criteria for the selection of patients at risk of ischemic cerebral attack and those who will need medical or surgical attention. Diabetic patients, particularly type 2, often have many reasons to take anti-platelet agents and lipid-lowering therapy. Therefore, carotid ultrasonography screening would have little effect on treatment modification or on glycaemia and blood pressure objectives, but could improve the prognosis of operable lesions.

IN THE GENERAL POPULATION

A one-time screening program was considered worthwhile if the prevalence of severe asymptomatic stenosis was over 20%. The presence of another arterial occlusive disease or other cardio-vascular risk factors could be a major argument for screening.

IN DIABETIC PATIENTS

Carotid intima-media thickness (IMT) was recognized as a reliable prognostic indicator of heart attack and stroke. It worsens with duration of diabetes, renal failure, cardiac neuropathy and poor long term glycaemic control.

CONCLUSION

Our review suggests that a one-time carotid ultrasonography screening could be recommended for diabetic patients with coronary disease or lower limb atherosclerosis (secondary prevention), all diabetic patients above 60 years of age, smokers, hypertensive and with hypercholesterolemia; type 1 diabetic patients with poor long term glycaemic control; all type 2 diabetic patients with renal failure, a long duration of ill-controlled diabetes or with a carotid bruit. This literature review should be analyzed with caution. It would be helpful to organize a prospective long term study on all types of diabetic patients, including a carotid ultrasonography screening program by experienced radiologists.

Primary Prevention of Ischemic Stroke

Background and Purpose— This guideline provides an overview of the evidence on various established and potential stroke risk factors and provides recommendations for the reduction of stroke risk.

Methods— Writing group members were nominated by the committee chair on the basis of each writer’s previous work in relevant topic areas and were approved by the American Heart Association Stroke Council’s Scientific Statement Oversight Committee. The writers used systematic literature reviews (covering the time period since the last review published in 2001 up to January 2005), reference to previously published guidelines, personal files, and expert opinion to summarize existing evidence, indicate gaps in current knowledge, and when appropriate, formulate recommendations based on standard American Heart Association criteria. All members of the writing group had numerous opportunities to comment in writing on the recommendations and approved the final version of this document. The guideline underwent extensive peer review before consideration and approval by the AHA Science Advisory and Coordinating Committee.

Results— Schemes for assessing a person’s risk of a first stroke were evaluated. Risk factors or risk markers for a first stroke were classified according to their potential for modification (nonmodifiable, modifiable, or potentially modifiable) and strength of evidence (well documented or less well documented). Nonmodifiable risk factors include age, sex, low birth weight, race/ethnicity, and genetic factors. Well-documented and modifiable risk factors include hypertension, exposure to cigarette smoke, diabetes, atrial fibrillation and certain other cardiac conditions, dyslipidemia, carotid artery stenosis, sickle cell disease, postmenopausal hormone therapy, poor diet, physical inactivity, and obesity and body fat distribution. Less well-documented or potentially modifiable risk factors include the metabolic syndrome, alcohol abuse, drug abuse, oral contraceptive use, sleep-disordered breathing, migraine headache, hyperhomocysteinemia, elevated lipoprotein(a), elevated lipoprotein-associated phospholipase, hypercoagulability, inflammation, and infection. Data on the use of aspirin for primary stroke prevention are reviewed.

Conclusion— Extensive evidence is available identifying a variety of specific factors that increase the risk of a first stroke and providing strategies for reducing that risk.

A New Approach for the Screening of Carotid Lesions: A ‘Fast-track’ Method with the Use of New Generation Hand-held Ultrasound Devices

OBJECTIVES

We assessed the usefulness of fast-track neck sonography with a new-generation hand-held ultrasound scanner in the detection of > or =60% carotid stenosis.

DESIGN

Patients with a past history of atherosclerotic disease or presence of risk factors were enrolled. All had fast-track carotid screening with a hand-held ultrasound scanner.

METHODS

Initial assessment was performed with our quick imaging protocol. A second examiner performed a conventional complete carotid duplex as gold-standard.

RESULTS

We enrolled 197 consecutive patients with a mean age of 67 years (range 35-94). A carotid stenosis >60% was detected in 13 cases (6%). The sensitivity, specificity, positive and negative predictive value of fast-track sonography was 100%, 64%, 17% and 100%, respectively. Concomitant power Doppler imaging during the fast-track method did not improve accuracy.

CONCLUSIONS

The use of a fast-track method with a hand-held ultrasound device can reduce the number of unnecessary carotid Duplex and enhance the screening efficiency without missing significant carotid stenoses.

Evaluation and management of asymptomatic carotid artery stenosis

Internal carotid artery stenosis (ICAS) is responsible for approximately 30% of ischemic strokes. Internal carotid artery stenosis of greater than 50% is present in about 4% to 8% of the population aged 50 to 79 years. Natural history studies and clinical trials have shown a small increase in stroke risk in patients with increasing degrees of ICAS, especially in those with greater than 80% reduction in carotid artery diameter. Randomized, prospective multicenter trials have revealed the superiority of carotid endarterectomy (CEA) over medical therapy in recently symptomatic patients with severe ICAS. However, the evidence from several randomized controlled trials of CEA in asymptomatic patients does not support the use of CEA in most of these patients; also, the role of noninvasive screening in this patient population remains uncertain and controversial. Furthermore, there is considerable uncertainty about whether the statistical benefit of avoiding a nondisabling stroke is worth the overall cost and risk of the procedure. Clinicians continue to struggle with treatment decisions for patients with asymptomatic ICAS. Carotid endarterectomy for asymptomatic ICAS should be considered only for medically stable patients with 80% or greater stenosis who are expected to live at least 5 years, and only in centers with surgeons who have a demonstrated low (<3%) perioperative complication rate. We outline the prevalence and natural history of ICAS, the evidence for CEA in patients with asymptomatic ICAS, the roles of screening and monitoring for ICAS, the methods of evaluating ICAS, and the implications for practicing clinicians.

Focused screening for occult carotid artery disease: patients with known heart disease are at high risk

OBJECTIVES

Stroke puts a major financial burden on our healthcare system. However, carotid duplex scanning performed as a screening test for occult carotid artery stenosis (CAS) currently is not reimbursed by Medicare. The goals of this study were to develop a cost-effective stroke screening program, to determine the prevalence of potential causes of stroke in this population, and to define a population at high risk in which screening would be most effective.

METHODS

In a community-based stroke screening program, patients were eligible if they were older than 60 years and had a history of either hypertension, heart disease, or cigarette smoking, or a family history of stroke. Screening included blood pressure determination, an electrocardiographic rhythm strip, and a previously validated modified carotid duplex ultrasound examination to detect CAS 50% or greater. The relationships between standard demographic risk factors and screening outcomes were analyzed.

RESULTS

Screening was performed in 610 patients. Unilateral or bilateral CAS was detected in 66 patients (10.8%). The finding of occult CAS was more prevalent than that of new hypertension (2.6%) or new atrial fibrillation (0.5%). Patients with known hypertension were significantly more likely to have CAS than were those without hypertension (12.7% vs 7.8%; P =.05). Patients with heart disease were significantly more likely to have CAS than were those without heart disease (18.2% vs 8%; P <.0001). Patients with both risk factors were significantly more likely to have occult carotid artery disease than were patients without either risk factor (22.1% vs 8.5%; P <.0001). Multivariate analysis with logistic regression revealed a history of heart disease as an independent predictor of occult carotid artery disease (odds ratio 95% confidence interval, 1.4-4.4). Type of heart disease was not a significant factor in predicting occult CAS. Direct cost of the screening, including community outreach, nurses, technicians, support staff, and miscellaneous expenses, was less than $75 per patient.

CONCLUSIONS

In a screening program for treatable causes of potential stroke, CAS was the most commonly diagnosed disease. More than one of every five patients with known hypertension and heart disease had occult CAS. Known heart disease of any type was a significant independent predictor of occult CAS. Screening for treatable causes of potential stroke can be cost-effective. This information could help to further target populations to screen for occult CAS and to justify reimbursement for screening carotid duplex scanning examinations.

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.

Value of the CT angiography in the diagnosis of common carotid artery bifurcation disease: CT angiography versus digital subtraction angiography and color flow Doppler

OBJECTIVE

assessment of the degree of stenosis is the central point in the treatment of carotid stenosis. The purpose of our study was to assess whether invasive CT angiography (CTA) is a feasible alternative to the current invasive gold standard carotid digital subtraction angiography (DSA) and the current non-invasive gold standard color flow doppler.

SUBJECTS AND METHODS

about 178 patients with cerebrovascular disease underwent digital subtraction angiography (DSA), CFD and CTA. CTA was performed on a Somatom plus 4 (Siemens, Erlangen Germany). CT was performed with 2/3/2 (collimation/table feed/reconstruction interval) or 2/3/1 mm, start delay 15-20 s, flow 2.5-3.0 ml/s, using 120 ml non-ionic contrast medium (300 mg J/ml). Quantification of degree of stenosis was based on the perfused area in the axial slices. Plaque morphology (soft and hard) and ulceration were evaluated.

RESULTS

CTA detected nine cases of significant stenosis, which had been underestimated by DSA. CTA failed in two cases of a membraneous stenosis, which were underestimated, and in two cases with teeth artifacts. Calcifications were more readily appreciated by CTA than in CFD. In this respect, both methods were superior to DSA. CFD, DSA and CTA had a sensitivity of 100% for occlusions, respectively.

CONCLUSION

CT angiography is useful in case of inconclusive CFD in the pre- and postoperative phase, and as a third modality in case of disagreement between DSA and CFD.

How does the degree of carotid stenosis affect the accuracy and interobserver variability of magnetic resonance angiography?

OBJECTIVES

The accuracy of magnetic resonance angiography (MRA) was determined in patients with recently symptomatic tight (80%-99%) carotid stenosis (on Doppler ultrasound), and the effect of stenosis severity on the accuracy and interobserver variability of MRA was studied.

METHODS

Forty four consecutive patients undergoing intra-arterial angiography (IAA) before carotid endarterectomy were prospectively studied, in two centres with identical MR scanners and sequences. All patients had undergone Doppler ultrasound, showing a 70% or worse carotid stenosis on the symptomatic side. MRA and IAA were done during the same admission. The MRA films were each independently and blindly read for percentage stenosis (signal gap if present) by four observers. The IA angiograms were read separately by one observer, blind to symptoms, and Doppler and MRA results.

RESULTS

Signal gaps on MRA were seen in stenoses ranging from 67% to 99% on intra-arterial angiography. Magnetic resonance angiograms consistently overestimated the percentage stenosis according to intra-arterial angiography. Clinically significant misclassification of stenosis occurred according to MRA in 7% of patients, and was more frequent as carotid stenosis increased.

CONCLUSION

Significant diagnostic errors occur with MRA in patients with tight carotid stenosis. Any morbidity occurring as a result of misclassification by MRA is likely to be offset by the avoidance of complications; however, this could only be determined with certainty in a randomised controlled trial.

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.