Prognosis after transient monocular blindness associated with carotid-artery stenosis

BACKGROUND

Transient monocular blindness associated with internal-carotid-artery stenosis is a risk factor for stroke. The effect of carotid endarterectomy in patients who present with transient monocular blindness has not been determined.

METHODS

We compared the risk of stroke among patients presenting with transient monocular blindness with the risk among patients presenting with hemispheric transient ischemic attack. The effect of endarterectomy was assessed in patients with transient monocular blindness. The analyses were based on data from the North American Symptomatic Carotid Endarterectomy Trial.

RESULTS

A total of 198 medically treated patients with transient monocular blindness had a three-year risk of ipsilateral stroke that was approximately half of that among 417 medically treated patients with hemispheric transient ischemic attack (adjusted hazard ratio, 0.53; 95 percent confidence interval, 0.30 to 0.94). Six factors were associated with a higher risk of stroke in patients with monocular blindness--an age of 75 years or more, male sex, a history of hemispheric transient ischemic attack or stroke, a history of intermittent claudication, stenosis of 80 to 94 percent of the luminal diameter, and the absence of collateral circulation. The three-year risk of stroke with medical treatment for patients with zero or one risk factor was 1.8 percent, with two risk factors 12.3 percent, and with three or more risk factors 24.2 percent (P=0.003). The three-year absolute reduction in the risk of stroke associated with endarterectomy was -2.2 percent (i.e., a 2.2 percent increase in risk) among patients with zero or one risk factor, 4.9 percent among those with two risk factors, and 14.3 percent among those with three or more risk factors (P=0.23 by a test for interaction).

CONCLUSIONS

Among patients with internal-carotidartery stenosis, the prognosis was better for those presenting with transient monocular blindness than for those presenting with hemispheric transient ischemic attack. Among patients with transient monocular blindness, carotid endarterectomy may be beneficial when other risk factors for stroke are also present.

Endarterectomy for carotid stenosis: new approaches in patient selection

Results of randomized trials on carotid endarterectomy make it mandatory that therapeutic decisions for patients with carotid stenosis consider the degree of stenosis, presence of symptoms, skill of surgeon and time since the last ischemic event. Patients with severe (>70% by angiogram) stenosis should receive carotid endarterectomy, provided the operative risk is <6% and symptoms have recurred within 6 months. With moderate stenosis (50--69% by angiogram), and with similar low operative risk and time limit, males with hemispheric, nondisabling stroke and appropriate CT lesion will benefit from carotid endarterectomy. Patients with TIA only, retinal symptoms alone and who are women are not going to benefit in this range of stenosis. Particularly at risk with medical care alone are symptomatic patients with coexistent intracranial stenosis, widespread white-matter lesions, intraluminal thrombi, contralateral occlusion and absence of good collateral circulation. The same high-risk patients, enjoy good long-term results from endarterectomy. Lacunar syndromes at presentation respond to endarterectomy, but with less benefit. Symptomatic patients do as well, regardless of age, provided patients with serious cardiac disorders and with organ failure are avoided. Serious doubt exists about indications for endarterectomy in asymptomatic subjects. Even if the upper limit of 3% perioperative risk is exceeded (and in large institutional databases and other studies, it usually is), the risk of large-artery strokes from the asymptomatic lesion is only slightly above the risk facing these subjects from lacunar and cardioembolic stroke. To prevent 1 large-artery stroke in 5 years in asymptomatic subjects requires that 111 subjects be submitted to endarterectomy.

Risk, causes, and prevention of ischaemic stroke in elderly patients with symptomatic internal-carotid-artery stenosis

BACKGROUND

Carotid endarterectomy benefits patients with symptomatic stenosis of 70-99% in the internal carotid artery, with smaller benefit for 50-69% stenosis. The benefit of carotid endarterectomy in patients of 75 years and older remains unclear.

METHODS

Patients aged 75 years or older from the North American Symptomatic Carotid Endarterectomy Trial were compared with those aged 65-74 years and less than 65 years for baseline characteristics and risk of ipsilateral ischaemic stroke at 2 years by degree of stenosis and treatment group.

FINDINGS

Among patients with 70-99% stenosis, the absolute risk reduction of ipsilateral ischaemic stroke with carotid endarterectomy was 28.9% (95% CI 12.9-44.9) for patients aged 75 years or older (n=71), 15.1% (7.2-23.0) for those aged 65-74 years (n=285), and 9.7% (1.5-17.9) for the youngest group (n=303). Among patients with 50-69% stenosis, the absolute risk reduction was significant only in those of 75 years and older (n=145; 17.3% [6.6-28.0]). The perioperative risk of stroke and death at any degree of stenosis was 5.2% for the oldest group, 5.5% for 65-74 years, and 7.9% for less than 65 years. The number of patients aged 75 years or older needed to treat to prevent one ipsilateral stroke within 2 years was three with 70-99% stenosis and six with 50-69% stenosis.

INTERPRETATION

In the prevention of ipsilateral ischaemic stroke, elderly patients with 50-99% symptomatic carotid stenosis benefited more from carotid endarterectomy than younger patients did. To achieve this treatment benefit, surgeons must be skilled and patients with other life-threatening illnesses must be excluded.

Appropriate use of carotid endarterectomy

When stroke-threatening symptoms derive from the extracranial portion of a carotid artery, endarterectomy becomes a consideration. The available evidence indicates clear benefit for patients with a severe symptomatic stenosis. For asymptomatic carotid disease, the risk of a surgical complication may contraindicate the procedure.

Effect of contralateral carotid artery stenosis on carotid ultrasound velocity measurements

BACKGROUND AND PURPOSE

Carotid ultrasonography is being increasingly performed as the sole investigation to assess internal carotid artery (ICA) stenosis. A potential source of error in using ultrasound peak systolic velocity (PSV) measurements is that the redistribution of blood flow due to severe stenosis in a contralateral carotid artery may lead to artificially elevated values.

METHODS

Ultrasonography was performed before and after carotid endarterectomy in symptomatic patients who participated in the North American Symptomatic Carotid Endarterectomy Trial (NASCET). The mean change in PSV in the unoperated artery was assessed across all degrees of angiographically defined stenosis. A simple theoretical resistance model of the cerebral circulation was also derived.

RESULTS

Complete bilateral ultrasound examinations were performed within 90 days of the initial scan in 386 patients. In the presence of a contralateral severe (70% to 99%) ICA stenosis, the PSV in the unoperated artery was artificially elevated by a mean of 84 cm/s (P:=0.03; 95% CI, 10 to 159 cm/s). The mean elevation was less pronounced for lesser degrees of stenosis (11 to 21 cm/s). Small elevations (3 to 12 cm/s) were observed when the contralateral artery had <70% stenosis. The patterns of observed results were congruent with those from the theoretical model.

CONCLUSIONS

The present study showed that a severely stenosed contralateral ICA can artificially elevate ultrasound PSV. Since the effect was greatest when bilaterally severe stenoses were present, caution must be exercised when assessing the degree of ICA stenosis on the basis of ultrasonography PSV measurements alone.

Long-term clinical and angiographic outcomes in symptomatic patients with 70% to 99% carotid artery stenosis

BACKGROUND AND PURPOSE

In 1991, the North American Symptomatic Carotid Endarterectomy Trial (NASCET) reported the benefit of carotid endarterectomy for 659 patients with 70% to 99% stenosis. Follow-up continued until 1997.

METHODS

The present study examined the risks and causes of ipsilateral stroke in the randomized groups and in those who had delayed endarterectomy or continued on medical therapy and also examined the evolution of carotid disease on follow-up imaging.

RESULTS

By on-treatment (efficacy) analysis, the risk of any ipsilateral stroke at 3 years was 28.3% for medically randomized and 8.9% for surgically randomized patients (19.4% absolute risk reduction, P:<0.001). For combined disabling or fatal ipsilateral stroke, the risks were 14.0% and 3.4%, respectively (10. 6% absolute risk reduction). In medical patients, >80% of the first strokes at 3 years were of large-artery origin. After February 1991, 116 suitable medical patients underwent endarterectomy within 6 months, and 115 continued on medical therapy. The 3-year risk of any ipsilateral stroke in the groups of 116 and 115 patients was 7.9% and 15.0%, respectively (7.1% absolute risk reduction). During follow-up, 81 patients had angiograms comparable to the baseline images. Progression by >/=10% occurred in 7 patients; regression, in 8; no change, in 39; and occlusion, in 27. By use of both angiography and ultrasound, 63 (25.5%) of the 247 medically treated patients progressed to occlusion, of whom 31.7% had an ipsilateral stroke before or on the day of occlusion.

CONCLUSIONS

Endarterectomy for patients with 70% to 99% stenosis and recent symptoms was efficacious in the long term. Compared with patients who continued on medical therapy, medical patients with delayed endarterectomy experienced a moderate benefit. Medically treated patients experienced a high risk of occlusion.

Small, unruptured intracranial aneurysms and management of symptomatic carotid artery stenosis. North American Symptomatic Carotid Endarterectomy Trial Group

Of the 2885 patients participating in the North American Symptomatic Carotid Endarterectomy Trial, 90 (3.1%) had unruptured intracranial aneurysms (UIA), of which 96% had a diameter of less than 10 mm. During an average 5-year follow-up, only one patient had subarachnoid hemorrhage 6 days after carotid endarterectomy (CE). For patients with unrepaired UIA, the 5-year stroke risk was 10% after CE and 22.7% with best medical care. Both risks are similar to those of patients without UIA. The decision regarding CE probably should not be influenced by the presence of a small UIA.

The causes and risk of stroke in patients with asymptomatic internal-carotid-artery stenosis. North American Symptomatic Carotid Endarterectomy Trial Collaborators

BACKGROUND

The causes of stroke in patients with asymptomatic carotid-artery stenosis have not been carefully studied. Information about causes might influence decisions about the use of carotid endarterectomy in such patients.

METHODS

We studied patients with unilateral symptomatic carotid-artery stenosis and asymptomatic contralateral stenosis from 1988 to 1997. The causes, severity, risk, and predictors of stroke in the territory of the asymptomatic artery were examined and quantified.

RESULTS

The risk of stroke at five years after study entry in a total of 1820 patients increased with the severity of stenosis. Among 1604 patients with stenosis of less than 60 percent of the luminal diameter, the risk of a first stroke was 8.0 percent (1.6 percent annually), as compared with 16.2 percent (3.2 percent annually) among 216 patients with 60 to 99 percent stenosis. In the group with 60 to 99 percent stenosis, the five-year risk of stroke in the territory of a large artery was 9.9 percent, that of lacunar stroke was 6.0 percent, and that of cardioembolic stroke 2.1 percent. Some patients had more than one stroke of more than one cause. In the territory of an asymptomatic occluded artery (as was identified in 86 patients), the annualized risk of stroke was 1.9 percent. Strokes with different causes had different risk factors. The risk factors for large-artery stroke were silent brain infarction, a history of diabetes, and a higher degree of stenosis; for cardioembolic stroke, a history of myocardial infarction or angina and hypertension; for lacunar stroke, age of 75 years or older, hypertension, diabetes, and a higher degree of stenosis.

CONCLUSIONS

The risk of stroke among patients with asymptomatic carotid-artery stenosis is relatively low. Forty-five percent of strokes in patients with asymptomatic stenosis of 60 to 99 percent are attributable to lacunes or cardioembolism. These observations have implications for the use of endarterectomy in asymptomatic patients. Without analysis of the risk of stroke according to cause, the absolute benefit associated with endarterectomy may be overestimated.

Causes and severity of ischemic stroke in patients with internal carotid artery stenosis

CONTEXT

Therapeutic trials generally have not distinguished outcomes of stroke according to cause.

OBJECTIVE

To determine whether stroke and subsequent disability was of large-artery, lacunar, or cardioembolic origin in patients with different degrees of symptomatic and asymptomatic carotid stenosis.

DESIGN

Observational study of prospective data collected from the North American Symptomatic Carotid Endarterectomy Trial between 1987 and 1997.

SETTING AND PATIENTS

A total of 2885 patients from 106 sites in the United States and abroad (median age, 67 years; 70% male) who had symptomatic internal carotid artery stenosis.

MAIN OUTCOME MEASURE

Risk of stroke from each of the 3 causes at 5 years by territory and degree of stenosis.

RESULTS

During an average follow-up of 5 years, 749 patients had 1039 strokes, including 112 of cardioembolic, 211 of lacunar, 698 of large-artery, 17 of primary intracerebral hemorrhage, and 1 of subarachnoid hemorrhage origin. The 5-year risk of first stroke after entry into the trial in any territory was 2.6% of cardioembolic cause, 6.9% of lacunar cause, and 19.7% of large-artery cause. The proportion of cardioembolic strokes in the territory of the symptomatic artery was 12.0% and 6.9% in 60% to 69% and 70% to 99% arterial stenosis, respectively; large-artery strokes predominated (78.4%) at 70% to 99% arterial stenosis. With 70% to 99% arterial stenosis, the proportion of strokes of cardioembolic and lacunar origin was 43.5% and 21.6% in asymptomatic and symptomatic arteries, respectively. A total of 67.6% of cardioembolic, 16.7% of lacunar, and 33.0% of large-artery strokes in the territory of the asymptomatic artery were disabling or fatal.

CONCLUSIONS

Our data suggest that approximately 20% and 45% of strokes in the territory of symptomatic and asymptomatic carotid arteries with 70% to 99% stenosis, respectively, are unrelated to carotid stenosis. The cause of subsequent strokes in similar types of patients should be considered when making treatment decisions involving carotid endarterectomy for patients with asymptomatic carotid stenosis, since lacunar and cardioembolic strokes cannot be prevented by endarterectomy.

Internal borderzone infarction: a marker for severe stenosis in patients with symptomatic internal carotid artery disease. For the North American Symptomatic Carotid Endarterectomy (NASCET) Group

BACKGROUND AND PURPOSE

Among subcortical infarctions, internal borderzone infarcts (IBI) are considered to be separate entities from perforating artery infarcts (PAI). The purpose of the present study is to examine the relationship between the presence of IBI and the degree of angiographically defined internal carotid artery (ICA) stenosis in symptomatic patients.

METHODS

A review of 1253 brain CTs from patients recruited by the North American Symptomatic Carotid Endarterectomy Trial was performed, using templates for the identification of subcortical and cortical vascular territories.

RESULTS

A total of 413 patients had visible ischemic lesions on the side ipsilateral to their symptomatic ICA. Of these, 138 had PAI, 108 had IBI, 122 had cortical infarcts, and 45 had a combination of different lesions. Mean (+/-SD) lesion diameter was larger for IBI (11.0+/-5.9 mm) than for PAI (7.1+/-4.7 mm) (P<0.001 for comparing 2 means). IBI was associated with higher degrees of ICA stenosis (P<0. 001). Sixty-three percent of the patients with IBI had severe (70% to 99%) ICA stenosis compared with 42% of patients with PAI; 18% of the IBI patients had stenosis of 90% or more compared with 8% of the patients with PAI. Multiple logistic regression did not identify any patient characteristics as confounders.

CONCLUSIONS

Among subcortical infarctions, IBI are associated with higher degrees of ICA stenosis in symptomatic patients. Differentiating between internal borderzone and perforating artery infarcts is important, because each may arise from different mechanisms, namely, carotid disease and small-vessel disease, respectively.

Risk factors and outcome of patients with carotid artery stenosis presenting with lacunar stroke. North American Symptomatic Carotid Endarterectomy Trial Group

OBJECTIVE

To examine the relationship between carotid artery stenosis, other risk factors, and lacunar stroke.

BACKGROUND

Carotid artery stenosis in patients presenting with lacune stroke may be coincidental or causal. The distinction by risk factor profile is uncertain. The risk and cause of subsequent stroke, and benefit of carotid endarterectomy (CE) is unknown.

METHODS

Stroke in patients entering the North American Symptomatic Carotid Endarterectomy Trial were classified as nonlacunar, possible lacune (symptoms without CT lacunae), or probable lacune (symptoms with CT lacunae).

RESULTS

Of 1,158 patients with hemispheric stroke, 493 had features of lacunar stroke (283 possible and 210 probable). Lacunar stroke presented more commonly in patients with milder (<50%) degrees of internal carotid artery (ICA) stenosis (p = 0.003). History of diabetes and hyperlipidemia, not hypertension, were associated independently even after accounting for the degree of stenosis. Medically treated patients presenting with nonlacunar stroke had a low risk of subsequent lacunar events of 2.9% at 3 years in comparison with 9.2% for probable lacunar presentation (p = 0.03). For patients with 50 to 99% ICA stenosis, the relative risk reductions (RRRs) in stroke from CE were 35% when the presenting stroke was probable lacunar versus 61% when the stroke was nonlacunar. Patients presenting with a possible lacunar stroke had a 53% RRR.

CONCLUSIONS

History of diabetes and hyperlipidemia were more important than arterial hypertension as risk factors for patients with lacunar stroke. Patients presenting with lacunar stroke more often had milder ICA stenosis. Although CE reduced the risk of stroke in all patients with 50 to 99% ICA stenosis, lesser benefits were observed in patients presenting with lacunar stroke.

Angiographically defined collateral circulation and risk of stroke in patients with severe carotid artery stenosis. North American Symptomatic Carotid Endarterectomy Trial (NASCET) Group

BACKGROUND AND PURPOSE

Blood supply through collateral pathways improves regional cerebral blood flow and may protect against ischemic events. The effect of collaterals on the risk of stroke and transient ischemic attack (TIA), in the presence of angiographic severe internal carotid artery (ICA) stenosis, was assessed.

METHODS

Angiographic collateral filling through anterior communicating and posterior communicating arteries and retrograde filling through ophthalmic arteries were determined in all patients at entry into the North American Symptomatic Carotid Endarterectomy Trial. Kaplan-Meier event-free survival analyses were performed on 339 medically treated and 342 surgically treated patients.

RESULTS

The presence of collaterals supplying the symptomatic ICA increased with severity of stenosis. Two-year risk of hemispheric stroke in medically treated patients with severe ICA stenosis was reduced in the presence of collaterals: 27.8% to 11.3% (P=0.005). Similar reductions were observed for hemispheric TIA (36.1% versus 19.1%; P=0.008) and disabling or fatal strokes (13.3% versus 6.3%; P=0.11). For surgically treated patients, the perioperative risk of hemispheric stroke was 1.1% in the presence of collaterals versus 4. 9% when absent. The 2-year stroke risks for surgical patients with and without collaterals were 5.9% versus 8.4%, respectively. Neither comparison in the surgical group was statistically significant. The observed reductions were independent of the degree of ICA stenosis and other vascular risk factors.

CONCLUSIONS

Collaterals are associated with a lower risk of hemispheric stroke and TIA, both long term and perioperatively. Angiographic identification of collaterals assists in identifying patients with severe ICA stenosis at lower risk of stroke and TIA.

Medical complications associated with carotid endarterectomy. North American Symptomatic Carotid Endarterectomy Trial (NASCET)

BACKGROUND AND PURPOSE

Carotid endarterectomy (CE) has been shown to be beneficial in patients with symptomatic high-grade (70% to 99%) internal carotid artery stenosis. To achieve this benefit, complications must be kept to a minimum. Complications not associated with the procedure itself, but related to medical conditions, have received little attention.

METHODS

Medical complications that occurred within 30 days after CE were recorded in 1415 patients with symptomatic stenosis (30% to 99%) of the internal carotid artery. They were compared with 1433 patients who received medical care alone. All patients were in the North American Symptomatic Carotid Endarterectomy Trial (NASCET).

RESULTS

One hundred fifteen patients (8.1%) had 142 medical complications: 14 (1%) myocardial infarctions, 101 (7.1%) other cardiovascular disorders, 11 (0.8%) respiratory complications, 6 (0.4%) transient confusions, and 10 (0.7%) other complications. Of the 142 complications, 69.7% were of short duration, and only 26.8% prolonged hospitalization. Five patients died: 3 from myocardial infarction and 2 suddenly. Medically treated patients experienced similar complications with one third the frequency. Endarterectomy was approximately 1.5 times more likely to trigger medical complications in patients with a history of myocardial infarction, angina, or hypertension (P<0.05).

CONCLUSIONS

Perioperative medical complications were observed in slightly fewer than 1 of every 10 patients who underwent CE. The majority of these complications completely resolved. Most complications were cardiovascular and occurred in patients with 1 or more cardiovascular risk factors. In this selected population, the occurrence of perioperative myocardial infarction was uncommon.

The North American Symptomatic Carotid Endarterectomy Trial : surgical results in 1415 patients

BACKGROUND AND PURPOSE

This study reports the surgical results in those patients who underwent carotid endarterectomy in the North American Symptomatic Carotid Endarterectomy Trial (NASCET).

METHODS

The rates of perioperative stroke and death at 30 days and the final assessment of stroke severity at 90 days were calculated. Regression modeling was used to identify variables that increased or decreased perioperative risk. Nonoutcome surgical complications were summarized. The durability of carotid endarterectomy was examined.

RESULTS

In 1415 patients there were 92 perioperative outcome events, for an overall rate of 6.5%. At 30 days the results were as follows: death, 1.1%; disabling stroke, 1.8%; and nondisabling stroke, 3.7%. At 90 days, because of improvement in the neurological status of patients judged to have been disabled at 30 days, the results were as follows: death, 1.1%; disabling stroke, 0.9%; and nondisabling stroke, 4.5%. Thirty events occurred intraoperatively; 62 were delayed. Most strokes resulted from thromboembolism. Five baseline variables were predictive of increased surgical risk: hemispheric versus retinal transient ischemic attack as the qualifying event, left-sided procedure, contralateral carotid occlusion, ipsilateral ischemic lesion on CT scan, and irregular or ulcerated ipsilateral plaque. History of coronary artery disease with prior cardiac procedure was associated with reduced risk. The risk of perioperative wound complications was 9.3%, and that of cranial nerve injuries was 8.6%; most were of mild severity. At 8 years, the risk of disabling ipsilateral stroke was 5.7%, and that of any ipsilateral stroke was 17.1%.

CONCLUSIONS

The overall rate of perioperative stroke and death was 6.5%, but the rate of permanently disabling stroke and death was only 2.0%. Other surgical complications were rarely clinically important. Carotid endarterectomy is a durable procedure.

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

BACKGROUND

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

METHODS

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

FINDINGS

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

INTERPRETATION

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

Importance of intracranial atherosclerotic disease in patients with symptomatic stenosis of the internal carotid artery. The North American Symptomatic Carotid Endarterectomy Trail

BACKGROUND AND PURPOSE

The estimated prevalence of intracranial atherosclerotic disease (IAD) in patients with stenosis of the extracranial internal carotid artery (ICA) varies between 20% and 50%. The benefits of carotid endarterectomy (CE) in patients with both IAD and symptomatic extracranial ICA stenosis are uncertain.

METHODS

The association between IAD and other vascular risk factors and with the risk of stroke at 3 years were studied in patients with symptomatic extracranial ICA stenosis who participated in the North American Symptomatic Carotid Endarterectomy Trial (NASCET). Since the NASCET protocol excluded severe IAD, only a modest number of patients in this category could be studied.

RESULTS

IAD was observed in one third of the patients. In medically treated patients, the relative risk of stroke associated with IAD varied from 1.3 (95% CI, 0.9 to 1.9) with extracranial ICA stenosis of <50% to 1.8 (95% CI, 1.1 to 3.2) with 85% to 99% ICA stenosis. In contrast, IAD did not affect the risk of stroke among surgically treated patients. To prevent 1 stroke ipsilateral to the symptomatic ICA stenosis over 3 years in patients who have also IAD, 12 patients with 50% to 69%, 5 patients with 70% to 84%, and 3 patients with 85% to 99% ICA stenosis have to undergo CE. In patients without IAD these numbers are 26, 7, and 6, respectively.

CONCLUSIONS

IAD is an independent risk factor for subsequent stroke in medically treated patients with symptomatic ICA stenosis. CE reduces this risk. The additional risk imposed by IAD in medically treated patients enhances the value of CE in patients with moderate symptomatic extracranial ICA stenosis. Detection of IAD, requiring angiography, is an important prelude to planning CE in symptomatic patients with moderate extracranial ICA stenosis.

Benefit of carotid endarterectomy in patients with symptomatic moderate or severe stenosis. North American Symptomatic Carotid Endarterectomy Trial Collaborators

BACKGROUND

Previous studies have shown that carotid endarterectomy in patients with symptomatic severe carotid stenosis (defined as stenosis of 70 to 99 percent of the luminal diameter) is beneficial up to two years after the procedure. In this clinical trial, we assessed the benefit of carotid endarterectomy in patients with symptomatic moderate stenosis, defined as stenosis of less than 70 percent. We also studied the durability of the benefit of endarterectomy in patients with severe stenosis over eight years of follow-up.

METHODS

Patients who had moderate carotid stenosis and transient ischemic attacks or nondisabling strokes on the same side as the stenosis (ipsilateral) within 180 days before study entry were stratified according to the degree of stenosis (50 to 69 percent or <50 percent) and randomly assigned either to undergo carotid endarterectomy (1108 patients) or to receive medical care alone (1118 patients). The average follow-up was five years, and complete data on outcome events were available for 99.7 percent of the patients. The primary outcome event was any fatal or nonfatal stroke ipsilateral to the stenosis for which the patient underwent randomization.

RESULTS

Among patients with stenosis of 50 to 69 percent, the five-year rate of any ipsilateral stroke (failure rate) was 15.7 percent among patients treated surgically and 22.2 percent among those treated medically (P=0.045); to prevent one ipsilateral stroke during the five-year period, 15 patients would have to be treated with carotid endarterectomy. Among patients with less than 50 percent stenosis, the failure rate was not significantly lower in the group treated with endarterectomy (14.9 percent) than in the medically treated group (18.7 percent, P=0.16). Among the patients with severe stenosis who underwent endarterectomy, the 30-day rate of death or disabling ipsilateral stroke persisting at 90 days was 2.1 percent; this rate increased to only 6.7 percent at 8 years. Benefit was greatest among men, patients with recent stroke as the qualifying event, and patients with hemispheric symptoms.

CONCLUSIONS

Endarterectomy in patients with symptomatic moderate carotid stenosis of 50 to 69 percent yielded only a moderate reduction in the risk of stroke. Decisions about treatment for patients in this category must take into account recognized risk factors, and exceptional surgical skill is obligatory if carotid endarterectomy is to be performed. Patients with stenosis of less than 50 percent did not benefit from surgery. Patients with severe stenosis (> or =70 percent) had a durable benefit from endarterectomy at eight years of follow-up.

Carotid endarterectomy does not affect long-term blood pressure: observations from the NASCET. North American Symptomatic Carotid Endarterectomy Trial

The aim of the study was to examine how blood pressure is affected by carotid endarterectomy over a 2-year period. We analyzed the data from 997 patients who received best medical care alone and 999 patients who received best medical care plus carotid endarterectomy (CE). All patients were recruited by the North American Symptomatic Carotid Endarterectomy Trial and were followed at regular clinic visits. The mean blood pressure at baseline was 145.2/81.2 mm Hg for medically treated patients and 146.2/81.9 mm Hg for surgically treated patients. The mean systolic and diastolic pressures increased by approximately 2.5% in the first month following randomization, then decreased over the next year and then remained relatively uniform. Throughout follow-up, surgical patients had slightly higher blood pressures than medically treated patients. At the end of 2 years, the mean systolic pressures in the two treatment groups converged to 147.6 mm Hg. The mean diastolic pressure in the medical patients returned to its baseline value, whereas the surgical patients' blood pressure remained slightly elevated by 0.5 mm Hg. The percentage of patients on antihypertensive medications mirrored the rise and fall in blood pressures. A sharp decrease in medication (from 56 to 43%) was observed in both treatment groups at 1 month. The percentage of patients on medication increased subsequently, with approximately 63% taking medication at the end of 2 years. CE does not affect long-term blood pressure. The use of antihypertensive medications appears to be the key component in blood pressure management. As hypertension is related to neurologic morbidity and mortality, strict regulation of blood pressure is extremely important in patients with cerebrovascular disease.

Carotid artery stenosis: external validity of the North American Symptomatic Carotid Endarterectomy Trial measurement method

PURPOSE

To assess the generalizability of the North American Symptomatic Carotid Endarterectomy Trial method for determining the degree of stenosis on angiograms.

MATERIALS AND METHODS

Six good-quality, baseline angiograms of carotid arteries that were less than 70% stenosed were reviewed by 14 experienced neuroradiologists at different academic institutions. All reviewers determined the degree of stenosis by calculating the ratio of the diameter of the artery at the point of maximal narrowing to the normal diameter distal to the stenosis (well beyond the carotid artery bulb). The reviewers marked the location of their measurements on the angiogram. Comparisons were performed among the reviewers' results and with the reference measurements.

RESULTS

Interobserver agreement was 0.84 (95% confidence interval = 0.65, 0.97). The average interobserver disagreement of +/-7% was comparable with that reported in the literature. The overall bias was 6%, which indicated a tendency of the reviewers to overestimate the degree of stenosis in comparison with the reference determination.

CONCLUSION

The North American Symptomatic Carotid Endarterectomy Trial reference measurements can be generalized beyond the bounds of this clinical trial, provided that attention is paid to details of the measurement method.

The risks and benefits of carotid endarterectomy in patients with near occlusion of the carotid artery. North American Symptomatic Carotid Endarterectomy Trial (NASCET) Group

Some believe that carotid endarterectomy (CEA) for carotid near occlusion is a necessary emergency procedure while others call it dangerous. We used the North American Symptomatic Carotid Endarterectomy Trial (NASCET) data to perform an observational study to examine the safety and benefit of CEA for carotid near occlusion. We divided the data of 659 patients into stenosis groups: 70 to 79%, 80 to 89%, 90 to 94%, and near occlusion. The 106 carotid-near-occlusion patients were subdivided into those with a string-like lumen (n = 29) and those without a string-like lumen (n = 77). Of the 48 patients with near occlusion treated with CEA, 3 (6.3%) had perioperative strokes, similar to the 70-94% stenosis group. Only 1 of 58 patients (1.7%) with near occlusion treated medically had a stroke in the first month, suggesting that CEA is not needed on an emergency basis in this circumstance. For medically treated patients, the 1-year risk of stroke increases with escalating degrees of carotid stenosis, where the risk is 35.1% for patients with 90-94% stenosis. For patients with near occlusion, the 1-year stroke risk diminishes to 11.1%, which approximates the risk for patients with 70-89% stenosis. A comparison of treatment differences indicates that surgery reduces the risk of stroke at 1 year by approximately one-half (p < 0.001), regardless of the degree of stenosis or the subcategory of carotid near occlusion (p = 0.89). Our data suggest that CEA is beneficial for near occlusion and not more dangerous than in patients with 70-94% stenosis, provided that the procedure is performed by an experienced surgeon with a low complication rate.

Long-term prognosis and the effect of carotid endarterectomy in patients with recurrent ipsilateral ischemic events. North American Symptomatic Carotid Endarterectomy Trial Group

BACKGROUND AND PURPOSE

The present study examines how the prognosis of patients who present with an ischemic event (TIA or nondisabling stroke) referable to a 70 to 99% carotid artery stenosis is modified by the pattern of their ischemic history. We also examined the benefits of performing carotid endarterectomy on the recently symptomatic artery.

METHODS

A total of 608 patients was divided into two groups. The recent group (N = 444) consisted of patients who became newly symptomatic within the previous 6 months of their presenting event. Prior to this, they were asymptomatic. The recurrent group (N = 164) consisted of patients who had one or more ischemic events within the previous 6 months of their presenting event, as well as one or more within the previous 7 to 12 months. All events were ipsilateral to the presenting event.

RESULTS

Kaplan-Meier risk estimates of ipsilateral stroke at 2 years for medically treated patients were 18.6 +/- 3.3% in the recent group and 41.2 +/- 6.9% in the recurrent group (p = 0.0002, logrank test). For patients who underwent carotid endarterectomy, the risks were 7.8 +/- 2.0% and 10.8 +/- 3.4% (p = 0.36, logrank test). Multivariate analyses did not identify any baseline patients characteristics as confounders nor any statistical interactions.

CONCLUSIONS

There is a need for urgency in considering carotid endarterectomy for patients with 70 to 99% carotid artery stenosis who have had recurrent ipsilateral ischemic events extending back more than 6 months. These patients are at more than twice the risk of stroke as those who are newly symptomatic.

Do the facts and figures warrant a 10-fold increase in the performance of carotid endarterectomy on asymptomatic patients?

The detailed results of the Asymptomatic Carotid Atherosclerosis Study (ACAS) have been published. Electrifying reports in the media suggested that 53% fewer strokes would occur if individuals with 60% or greater stenosis were submitted to endarterectomy. The burning question is whether the evidence from this trial, and those preceding it, is sufficiently compelling to persuade any or all individuals with carotid stenosis, but free of any hemisphere and retinal symptoms, to have carotid endarterectomy. Based on a variety of population samplings, it is reasonable to estimate that approximately two million people are living in North America and Europe with asymptomatic lesions comparable with those studied in the ACAS.

The dilemma of surgical treatment for patients with asymptomatic carotid disease

Several case series have suggested that endarterectomy is beneficial in asymptomatic carotid artery disease. Four randomized trials have been done in this area, the most recent of which is the Asymptomatic Carotid Atherosclerosis Study (ACAS). Results of the first three trials were negative, and ACAS produced a tantalizing, statistically significant finding that does not translate into clinical importance. Disabling strokes have not been reduced by surgical therapy, and the benefit for women has not been shown. It is unclear from this study whether persons with the greatest stenosis and the highest vascular risk profiles are appropriate candidates for endarterectomy. In patients in whom carotid artery disease is incidentally discovered, the benefits of the prophylactic addition of carotid endarterectomy to coronary bypass grafting or other major surgical procedure in patients are still unknown. Excellent surgical skill is of paramount importance for the future use of this procedure. Mass population screening to detect asymptomatic carotid disease will only be justified when and if future studies identify patients in whom the risk for disabling stroke after the procedure is clearly reduced.

Long-term prognosis and effect of endarterectomy in patients with symptomatic severe carotid stenosis and contralateral carotid stenosis or occlusion: results from NASCET. North American Symptomatic Carotid Endarterectomy Trial (NASCET) Group

The purpose of this study was to examine how the prognosis of patients who presented with a recent ischemic event referable to a 70% to 99% stenosis of one carotid artery (ipsilateral) was altered by stenosis and occlusion of the contralateral carotid artery. The benefit of performing carotid endarterectomy on the recently symptomatic artery, in the presence of contralateral artery disease, was also examined. A total of 659 patients were grouped into one of three categories according to the extent of stenosis in the contralateral carotid artery: less than 70% (559 patients), 70% to 99% (57 patients), and occlusion (43 patients). Strokes that occurred during the follow-up period were designated as ipsilateral if they arose from the same carotid artery as the symptom for which the patient had been entered into the study. Medically treated patients with an occluded contralateral artery were more than twice as likely to have had an ipsilateral stroke at 2 years than patients with either severe (hazard ratio: 2.36; 95% confidence interval (CI): 1.00-5.62) or mild-to-moderate (hazard ratio: 2.65; 95% CI: 1.43-4.90) contralateral artery stenosis. The perioperative risk of stroke and death was higher in patients with an occluded contralateral artery (4.0% risk) or mild-to-moderate (5.1% risk) contralateral stenosis. Regression analyses indicated that the results were not affected by other risk factors. An occluded contralateral carotid artery significantly increased the risk of stroke associated with a severely stenosed ipsilateral carotid artery. Despite higher perioperative morbidity in the presence of an occluded contralateral artery, the longer-term outlook for patients who had endarterectomy performed on the recently symptomatic, severely stenosed ipsilateral carotid artery was considerably better than for medically treated patients.

Accuracy and prognostic consequences of ultrasonography in identifying severe carotid artery stenosis. North American Symptomatic Carotid Endarterectomy Trial (NASCET) Group

BACKGROUND AND PURPOSE

The accuracy of routine ultrasonography in detecting severe carotid artery stenosis was evaluated in comparison with cerebral angiography. The precision of ultrasonographic criteria in predicting the risk of stroke was also assessed.

METHODS

A total of 1011 symptomatic carotid bifurcations were studied in patients from the North American Symptomatic Carotid Endarterectomy Trial (NASCET). Given that all patients were considered for entry into the trial, the chance of a verification bias affecting the analyses was minimized. The ultrasonographic data consisted of peak systolic velocities and frequency changes from both the internal and common carotid arteries. Angiographic stenosis was calculated as in NASCET. Receiver operating characteristic (ROC) curves were constructed from the ultrasonographic data for the detection of 70% or greater stenosis on the basis of an angiographic assessment. Kaplan-Meier stroke-free survival curves were used to predict the risk of stroke.

RESULTS

The areas under the ROC curves ranged from 0.74 to 0.75 (95% confidence interval [CI], 0.69 to 0.79). The sensitivities and specificities ranged from 0.65 to 0.71. The risk of stroke at 18 months declined sharply as the degree of angiographically defined stenosis declined from 99% to 70%. No pattern of decline was apparent on the basis of the ultrasonographic data.

CONCLUSIONS

The results indicate that the accuracy of ultrasonography is moderate when flow parameters are used to assess the degree of stenosis. Ultrasonography should be used as a screening tool to exclude patients with no carotid artery disease from further testing. Conventional angiography remains an essential investigation before assigning the risk of stroke and deciding appropriate treatment for extracranial carotid artery disease.

Update on carotid endarterectomy

Progress in therapeutic decision-making for patients with carotid artery disease has come from evaluations made by several major randomized clinical trials. For patients who are symptomatic and have arteriographically proven stenoses of 70% or more, endarterectomy is clearly established as the treatment of choice. Symptomatic patients with stenoses of less than 70% remain the subject of ongoing study. Asymptomatic patients are at low risk of stroke save for those with the highest (80% to 90%) degrees of stenosis, and even for these subjects the annual stroke rate is close to the operative risk. Four trials have been reported but the practicing physician is still without clear guidelines. The appropriateness of endarterectomy remains unsettled for any group of patients with narrowing of the carotid artery in the absence of symptoms. The decision to apply endarterectomy to symptomatic and to asymptomatic patients must attend to not only the prognostic importance of the degree of stenosis, but also to the vascular risk profile of the individual patient.

Carotid endarterectomy: emerging indications

Several randomized trials have recently reported on the benefit of carotid endarterectomy for symptomatic or asymptomatic patients. A positive benefit has been found for symptomatic patients with > or = 70% stenosis measured by angiogram with a particular formula and performed with high surgical skill. Symptomatic patients with < 70% stenosis continue to be randomized and followed. The answer for this group is expected in the next two years. The randomized trials of asymptomatic patients have not established the benefit for carotid endarterectomy clearly. The most recent trial shows the absolute risk reduction at 5 years is only 5.9% or less than 1.5% risk reduction per year. A fifth trial continues in Europe.

Prognosis for patients following a transient ischemic attack with and without a cerebral infarction on brain CT. North American Symptomatic Carotid Endarterectomy Trial (NASCET) Group

BACKGROUND

Although cerebral infarctions are commonly observed on brain CTs of patients with TIAs, their prognostic importance is unknown.

METHOD

The association between appropriately sited brain infarctions (ie, lesions located in the anterior circulation of the brain and ipsilateral to the symptomatic stenosed carotid artery) visualized on CT and the risk of subsequent stroke was assessed by Cox proportional hazards regression in 164 patients presenting with TIA (and no history of previous stroke) and severe angiographically defined carotid stenosis (70 to 99%) from the North American Symptomatic Carotid Endarterectomy Trial.

RESULTS

Patients with a TIA and CT-verified brain lesions were older and were more likely to have higher degrees of carotid stenosis and carotid plaque ulceration, a longer duration of symptoms, and a history of hypertension. With regard to prognosis, after adjusting for all known risk factors (patient characteristics) in a regression analysis, the presence of ischemic lesions observed on CT was not associated with an increased risk of ipsilateral stroke at 2 years (adjusted hazard ratio = 1.00; 95% CI: 0.39 to 2.58; p value = 0.99).

CONCLUSION

Considered in combination with other patient characteristics, the mere presence of an appropriately sited cerebral infarction on CT does not alter the prognosis (risk of ipsilateral strokes) of severely stenosed patients with TIA. Therefore, there is no clinical rationale in differentiating patients with TIA on the basis of CT findings alone.

The risk of stroke in patients with first-ever retinal vs hemispheric transient ischemic attacks and high-grade carotid stenosis. North American Symptomatic Carotid Endarterectomy Trial

BACKGROUND

The prognosis of amaurosis fugax has been considered to be favorable compared with that of hemispheric transient ischemic attacks. However, this has remained uncertain for patients with significant carotid stenosis as the assessment of progression of the disease has been confounded when patients undergo carotid endarterectomy. In the North American Symptomatic Carotid Endarterectomy Trial, patients with high-grade (70% to 99%) carotid stenosis were randomized to receive either medical or surgical treatment, thus making an unconfounded analysis possible.

METHOD

We identified 129 medically treated patients with high-grade carotid stenosis who had their first-ever transient ischemic attack as the entry event into the trial. Fifty-nine patients with retinal transient ischemic attacks (RTIAs) were compared with 70 patients with hemispheric transient ischemic attacks (HTIAs).

RESULTS

Patients with HTIAs were older, with a higher prevalence of most risk factors for stroke. Average time of delay from the onset of transient ischemic attacks to medical treatment was longer for patients with RTIAs than for patients with HTIAs (48.5 vs 15.2 days). Kaplan-Meier estimates of the risk of ipsilateral stroke at 2 years were 16.6% +/- 5.6% for patients with RTIAs and 43.5% +/- 6.7% for patients with HTIAs (P = .002 for the difference in risk between RTIAs and HTIAs). From corresponding Cox's proportional hazards regression analyses, the risk of ipsilateral stroke ranged from 11.2% to 28.9% for patients with RTIAs and from 37.4% to 96.3% for patients with HTIAs across stenoses, spanning 75% to 95%. Overall, the relative risk of ipsilateral stroke (HTIAs compared with RTIAs) was 3.23 (95% confidence interval, 1.47 to 7.12), regardless of the degree of high-grade stenosis.

CONCLUSION

To our knowledge, this study is the first report on the expected outcome for medically treated patients with high-grade (70% to 99%) carotid stenosis in whom the first-ever event was either an RTIA or HTIA. The presence of RTIAs carries a considerable risk of ipsilateral strokes, particularly at higher degrees of stenosis. However, in comparison with HTIAs, patients with RTIAs still have a better prognosis.

Drugs and surgery in the prevention of ischemic stroke

Randomized clinical trials have proved that warfarin therapy decreases the risk of stroke in patients with nonvalvular atrial fibrillation and in those who have had a myocardial infarction. In patients who are not candidates for long-term anticoagulant therapy, aspirin is beneficial, but the reduction in risk is smaller with aspirin than with warfarin. In patients with cerebral ischemic symptoms of noncardiac origin, aspirin and ticlopidine reduce the risk of stroke, but the benefit is modest. Given alone, neither dipyridamole nor sulfinpyrazone prevents stroke. The question remains whether either of these drugs plus aspirin is better than aspirin alone. The optimal dose of aspirin for stroke prevention has not been established. Carotid endarterectomy reduces the risk of stroke in symptomatic patients with at least 70 percent stenosis, as determined by arteriography. Current trials are addressing the question of whether endarterectomy is beneficial for patients with moderate degrees of carotid stenosis. The benefit of endarterectomy for patients with asymptomatic carotid lesions remains unclear.

Guidelines for carotid endarterectomy. A multidisciplinary consensus statement from the Ad Hoc Committee, American Heart Association

BACKGROUND AND PURPOSE

Indications for carotid endarterectomy have engendered considerable debate among experts and have resulted in publication of retrospective reviews, natural history studies, audits of community practice, position papers, expert opinion statements, and finally prospective randomized trials. The American Heart Association assembled a group of experts in a multidisciplinary consensus conference to develop this statement.

METHODS

A conference was held July 16-18, 1993, in Park City, Utah, that included recognized experts in neurology, neurosurgery, vascular surgery, and healthcare planning. A program of critical topics was developed, and each expert presented a talk and provided the chairman with a summary statement. From these summary statements a document was developed and edited onsite to achieve consensus before final revision.

RESULTS

The first section of this document reviews the natural history, methods of patient evaluation, options for medical management, results of surgical management, data from position statements, and results to date of prospective randomized trials for symptomatic and asymptomatic patients with carotid artery disease. The second section divides 96 potential indications for carotid endarterectomy, based on surgical risk, into four categories: (1) Proven: This is the strongest indication for carotid endarterectomy; data are supported by results of prospective contemporary randomized trials. (2) Acceptable but not proven: a good indication for operation; supported by promising but not scientifically certain data. (3) Uncertain: Data are insufficient to define the risk/benefit ratio. (4) Proven inappropriate: Current data are adequate to show that the risk of surgery outweighs any benefit.

CONCLUSIONS

Indications for carotid endarterectomy in symptomatic good-risk patients with a surgeon whose surgical morbidity and mortality rate is less than 6% are as follows. (1) Proven: one or more TIAs in the past 6 months and carotid stenosis > or = 70% or mild stroke within 6 months and a carotid stenosis > or = 70%; (2) acceptable but not proven: TIAs within the past 6 months and a stenosis 50% to 69%, progressive stroke and a stenosis > or = 70%, mild or moderate stroke in the past 6 months and a stenosis 50% to 69%, or carotid endarterectomy ipsilateral to TIAs and a stenosis > or = 70% combined with required coronary artery bypass grafting; (3) uncertain: TIAs with a stenosis < 50%, mild stroke and stenosis < 50%, TIAs with a stenosis < 70% combined with coronary artery bypass grafting, or symptomatic, acute carotid thrombosis; (4) proven inappropriate: moderate stroke with stenosis < 50%, not on aspirin; single TIA, < 50% stenosis, not on aspirin; high-risk patient with multiple TIAs, not on aspirin, stenosis < 50%; high-risk patient, mild or moderate stroke, stenosis < 50%, not on aspirin; global ischemic symptoms with stenosis < 50%; acute dissection, asymptomatic on heparin. Indications for carotid endarterectomy in asymptomatic good-risk patients performed by a surgeon whose surgical morbidity and mortality rate is less than 3% are as follows. (1) Proven: none. As this statement went to press, the National Institute of Neurological Disorders and Stroke issued a clinical advisory stating that the Institute has halted the Asymptomatic Carotid Atherosclerosis Study (ACAS) because of a clear benefit in favor of surgery for patients with carotid stenosis > or = 60% as measured by diameter reduction. When the ACAS report is published, this indication will be recategorized as proven. (2) acceptable but not proven: stenosis > 75% by linear diameter; (3) uncertain: stenosis > 75% in a high-risk patient/surgeon (surgical morbidity and mortality rate > 3%), combined carotid/coronary operations, or ulcerative lesions without hemodynamically significant stenosis; (4) proven inappropriate: operations with a combined stroke morbidity and mortality > 5%.

Guidelines for carotid endarterectomy. A multidisciplinary consensus statement from the ad hoc Committee, American Heart Association

BACKGROUND AND PURPOSE

Indications for carotid endarterectomy have engendered considerable debate among experts and have resulted in publication of retrospective reviews, natural history studies, audits of community practice, position papers, expert opinion statements, and finally prospective randomized trials. The American Heart Association assembled a group of experts in a multidisciplinary consensus conference to develop this statement.

METHODS

A conference was held July 16-18, 1993, in Park City, Utah, that included recognized experts in neurology, neurosurgery, vascular surgery, and healthcare planning. A program of critical topics was developed, and each expert presented a talk and provided the chairman with a summary statement. From these summary statements a document was developed and edited onsite to achieve consensus before final revision.

RESULTS

The first section of this document reviews the natural history, methods of patient evaluation, options for medical management, results of surgical management, data from position statements, and results to date of prospective randomized trials for symptomatic and asymptomatic patients with carotid artery disease. The second section divides 96 potential indications for carotid endarterectomy, based on surgical risk, into four categories: (1) Proven: This is the strongest indication for carotid endarterectomy; data are supported by results of prospective contemporary randomized trials. (2) Acceptable but not proven: a good indication for operation; supported by promising but not scientifically certain data. (3) Uncertain: Data are insufficient to define the risk/benefit ratio. (4) Proven inappropriate: Current data are adequate to show that the risk of surgery outweighs any benefit.

CONCLUSIONS

Indications for carotid endarterectomy in symptomatic good-risk patients with a surgeon whose surgical morbidity and mortality rate is less than 6% are as follows. (1) Proven: one or more TIAs in the past 6 months and carotid stenosis > or = 70% or mild stroke within 6 months and a carotid stenosis > or = 70%; (2) acceptable but not proven: TIAs within the past 6 months and a stenosis 50% to 69%, progressive stroke and a stenosis > or = 70%, mild or moderate stroke in the past 6 months and a stenosis 50% to 69%, or carotid endarterectomy ipsilateral to TIAs and a stenosis > or = 70% combined with required coronary artery bypass grafting; (3) uncertain: TIAs with a stenosis < 50%, mild stroke and stenosis < 50%, TIAs with a stenosis < 70% combined with coronary artery bypass grafting, or symptomatic, acute carotid thrombosis; (4) proven inappropriate: moderate stroke with stenosis < 50%, not on aspirin; single TIA, < 50% stenosis, not on aspirin; high-risk patient with multiple TIAs, not on aspirin, stenosis < 50%; high-risk patient, mild or moderate stroke, stenosis < 50%, not on aspirin; global ischemic symptoms with stenosis < 50%; acute dissection, asymptomatic on heparin. Indications for carotid endarterectomy in asymptomatic good-risk patients performed by a surgeon whose surgical morbidity and mortality rate is less than 3% are as follows. (1) Proven: none. (As this statement went to press, the National Institute of Neurological Disorders and Stroke issued a clinical advisory stating that the Institute has halted the Asymptomatic Carotid Atherosclerosis Study (ACAS) because of a clear benefit in favor of surgery for patients with carotid stenosis > or = 60% as measured by diameter reduction. When the ACAS report is published, this indication will be recategorized as proven. (2) acceptable but not proven: stenosis > 75% by linear diameter; (3) uncertain; stenosis > 75% in a high-risk patient/surgeon (surgical morbidity and mortality rate > 3%), combined carotid/coronary operations, or ulcerative lesions without hemodynamically significant stenosis; (4) proven inappropriate: operations with a combined stroke morbidity and mortality > 5%.

Lack of relationship between leukoaraiosis and carotid artery disease. The North American Symptomatic Carotid Endarterectomy Trial

OBJECTIVE

Leukoaraiosis (LA) (white matter changes) is frequently observed on computed tomographic scans of the brain of elderly patients at risk of stroke. A localized vascular-ischemic cause has been suggested for its underlying mechanism. Our aim was to assess whether high-grade carotid stenosis is associated with LA.

DESIGN/SETTING

Patients enrolled in the North American Symptomatic Carotid Endareterectomy Trial (also known as NASCET) were evaluated for LA using a recently proposed grading scale. Ordinal regression analysis was used to assess the association between the severity of carotid artery stenosis and the extent of LA observed on computed tomographic scans. The patients' brain hemisphere was selected as the unit of analysis.

RESULTS

Of the 2394 brain hemispheres contributed to the analyses, 352 (14.7%) had signs of LA. After controlling for known stroke risk factors in the ordinal regression analysis, only the history of stroke and increasing age were significantly related to LA. Severity of stenosis was observed to be unrelated (odds ratio [severe vs mild stenosis] = 1.08; 95% confidence interval, 0.73-1.62; P = .952) as were a history of hypertension and a history of myocardial infarction.

CONCLUSION

Leukoaraiosis is not associated with severe carotid artery stenosis.

Further comments on the measurement of carotid stenosis from angiograms. North American Symptomatic Carotid Endarterectomy Trial (NASCET) Group

BACKGROUND AND PURPOSE

Three different methods for estimating the percentage of reduction in the diameter of the internal carotid artery (ie, stenosis) have been proposed in the literature. Further comparisons of the methods were carried out with the intent of recommending a current standard for determining the percentage of stenosis from angiograms.

METHODS

Angiograms from 112 patients were obtained. For each angiogram, stenosis was estimated in the manner of the European Carotid Surgery Trial (ECST method), the North American Symptomatic Carotid Endarterectomy Trial (NASCET method), and by a method using the common carotid artery lumen diameter (CC method).

RESULTS

Although there is much discrepancy among the estimates of stenosis arising from the three different methods for any particular patient, it is possible to predict (on average) the percentage of stenosis from one method to another. The relationship between the NASCET and CC methods is linear, with a mean ratio of distal internal carotid artery to common carotid diameter of 0.62 (SD of 0.11). The variability in the diameter of the common carotid artery lumen stabilizes only beyond 2.5 common carotid diameter units (approximately 20 to 30 mm by conventional angiography) proximal to the bifurcation. Unexpectedly, the relationships between both the ECST and NASCET methods and ECST and CC methods were parabolic (P < .001). The reasons underlying these departures from linearity are uncertain.

CONCLUSIONS

The comparability of our results with those reported in the literature regarding the CC and NASCET methods provides further evidence of the reproducibility of methods measuring anatomic features that can be visualized on an angiogram. Disease of the internal carotid artery is one of the important causes of ischemic symptoms. Measuring the narrowest portion of the internal artery relative to the normal portion of the same artery, well beyond the bulb, is a logical method. Moreover, benefits of carotid endarterectomy for patients with 70% to 99% stenosis as determined by the NASCET method have been well established in a clinical trial. Converting from the NASCET method to the CC method, given that the CC method is neither superior nor easier to calculate, is not recommended.