Management of carotid artery stenosis

Abstract

OBJECTIVE

To clarify the definition of carotid artery diseases, the appropriateness of screening for disease, investigation and management of patients presenting with transient ischemic attacks, and management of asymptomatic carotid bruits.

SOURCES OF INFORMATION

MEDLINE was searched using the terms carotid endarterectomy, carotid disease, and carotid stenosis. Most studies offer level II or III evidence. Consensus statements and guidelines from various neurovascular societies were also consulted.

MAIN MESSAGE

Patients with symptoms of hemispheric transient ischemic attacks associated with >70% stenosis of the internal carotid artery are at highest risk of major stroke or death. Risk is greatest within 48 hours of symptom onset; patients should have urgent evaluation by a vascular surgeon for consideration of carotid endarterectomy (CEA). Patients with 50% to 69% stenosis might benefit from urgent surgical intervention depending on clinical features and associated comorbidity. Patients with <50% stenosis do not benefit from surgery. Asymptomatic patients with >60% stenosis should be considered for elective CEA.

CONCLUSION

Symptomatic carotid artery syndromes need urgent carotid duplex evaluation to determine the need for urgent surgery. Those with the greatest degree of stenosis derive the greatest benefit from timely CEA.

EDITOR’S KEY POINTS.

• Two recent randomized controlled trials support a more aggressive approach to referral for carotid endarterectomy in patients with transient ischemic attacks (TIAs).

• Those with symptoms of hemispheric TIA with >70% stenosis of the internal carotid artery are at highest risk of major stroke or death, especially within the first 48 hours. They should be urgently evaluated by a vascular surgeon.

• Patients with TIAs and 50% to 69% stenosis might benefit from surgery. Those older than 75 years, men, and people with more severe disease are at greatest risk of stroke. Those with <50% stenosis do not benefit from surgery.

• Medical management to prevent stroke should be aggressive because combined therapy can reduce strokes by up to 80%. Management includes controlling hypertension; stopping smoking; and using antiplatelet medications, lipid-lowering agents, and angiotensin-converting enzyme inhibitors.

POINTS DE REPÈRE DU RÉDACTEUR.

• Deux essais randomisés récents recommandent d’intervenir de façon plus agressive devant un épisode d’ischémie transitoire (ÉIT) en demandant une consultation pour endartériectomie éventuelle.

• Ceux qui ont des symptômes d’ÉIT hémisphérique avec une sténose de la carotide interne de >70% sont les plus à risque d’accident vasculaire cérébral (AVC) ou de mort, particulièrement durant les 48 premières heures. Ils devraient être évalués sans retard par un chirurgien vasculaire.

• Les sténoses entre 50 et 69% pourraient bénéficier d’une intervention. Les plus de 75 ans, les hommes et les personnes qui souffrent de maladies plus graves ont un plus fort risque d’AVC. Les sténoses de <50% n’ont pas avantage à être opérées.

• La prévention des AVC exige une prise en charge agressive; en effet, le traitement combiné prévient jusqu’à 80% de ces accidents. Ce traitement comprend un contrôle de l’hypertension, l’arrêt du tabac, une médication anti-plaquettaire, des agents hypocholestérolémiants et des inhibiteurs de l’enzyme de conversion de l’angiotensine.

Stroke is the third most common cause of death worldwide after ischemic heart disease and cancer. Approximately 30% of patients die within the first year of having a stroke and another 50% are left disabled. The morbidity of a stroke is devastating. We hope a more aggressive approach to management will improve outcomes. Common causes of stroke are listed in Table 1.¹

Table 1.

Common causes of stroke

Extracranial carotid disease (carotid stenosis) accounts for at least 50% of ischemic strokes and should be managed efficiently to minimize the incidence of stroke. Unfortunately, only about 15% of strokes are preceded by transient ischemic attacks (TIAs).² Until recently, North American guidelines recommended that assessment and investigation be completed within 1 week of a TIA,^3,4 and British guidelines recommended assessment within 2 weeks.^5,6 New evidence now suggests that earlier evaluation is needed.

Once an acute TIA is clinically diagnosed, carotid imaging should be performed immediately, and if indicated, patients should be referred for urgent carotid endarterectomy (CEA). Two major randomized trials have confirmed that symptomatic patients benefit from CEA (level I evidence).^7,8 Risk of stroke following a TIA is 5.5% at 48 hours, 8.0% to 10.3% at 7 days, 11.5% to 14.3% at 30 days, and 17.3% to 20.1% at 90 days (level II).^9-13

Current data also confirm that asymptomatic patients aged 75 years or younger with >60% carotid stenosis are likely to benefit from CEA (level I).¹⁴ Family physicians and emergency room physicians can greatly affect the outcomes of these patients, as they are often the first to evaluate them.

Quality of evidence

MEDLINE was searched using the terms carotid endarterectomy, carotid disease, and carotid stenosis. Consensus statements and guidelines from various neurovascular societies were also sought. Most of the evidence is level I or II.

Definitions

Stroke is defined by the World Health Organization as the clinical syndrome of rapid onset of a focal (or global, as in subarachnoid hemorrhage) cerebral deficit that lasts more than 24 hours or leads to death, with no apparent cause other than a vascular one. Transient ischemic attack is a sudden, focal neurologic deficit that lasts less than 24 hours. Most symptoms of TIA last from a few seconds to 5 to 10 minutes, and 75% of symptoms resolve within 1 hour.^1,15,16

The proposed new definition of TIA is a brief episode of neurologic dysfunction caused by focal brain or retinal ischemia, with clinical symptoms typically lasting less than 1 hour and no evidence of acute infarction. The corollary is that persistent clinical signs or characteristic imaging abnormalities of infarction detected by computerized tomography (CT) or magnetic resonance imaging (MRI) constitute a stroke.¹⁷

Screening

The prevalence of >50% carotid artery stenosis in the general population is too low to justify widespread screening for this condition (level I).¹⁸ About 35% of patients with a carotid bruit have >50% stenosis. Therefore, carotid arteries should be auscultated as part of routine physical examinations in the general adult population. Those found to have carotid bruits should be further evaluated by duplex scans. Patients with symptomatic coronary artery disease have a 22% incidence of carotid stenosis >50% and an 8% to 12% incidence of carotid stenosis >70%.¹⁹

Patients with peripheral arterial disease have a 14% incidence of carotid artery stenosis >50% (level II).²⁰ Given the relatively limited access to duplex scanning, however, we cannot advocate screening these patients for asymptomatic carotid disease. This is based on the idea that these patients are likely already receiving medical therapy for atherosclerosis and, given their underlying disease, are not in a low-risk category for carotid artery surgery.

Carotid artery disease presentations

Symptomatic disease.

Classic symptoms of TIA are contrasted with vertebrobasilar symptoms in Table 2. Although not always possible, it is important to distinguish between these two types of symptoms because patients with transient ischemia of the vertebrobasilar system do not benefit from CEA.

Table 2.

Carotid symptoms compared with vertebrobasilar symptoms

*Imperfect articulation of speech due to disturbance of muscular control.

†Speech impairment from lack of coordination and failure to arrange words in proper order.

Patients presenting with motor weakness, speech deficit, hemispatial deficit, or hemianopia, alone or in combination, are at high risk (5%) of having a stroke within 48 hours even with medical management (level II).^9,10,12,13 Patients who present with sensory deficits and amaurosis fugax are at low risk (0%) of stroke within 48 hours (level II).¹⁰ Risk of stroke at 90 days in symptomatic patients is between 8% and 20.1% (level II).^9,11-13

Asymptomatic carotid bruit.

Asymptomatic carotid artery stenosis is usually detected by a physician auscultating a patient’s carotid arteries and hearing a bruit or coincidentally during ultrasound examination of the neck. Among patients with carotid bruit, only 35% have hemodynamically significant lesions (70% to 90% stenosis). Among patients with significant hemodynamic carotid stenosis, only 50% have a bruit noted during physical examination. The annual incidence of stroke among those with asymptomatic bruits but no prior TIA is 1% to 3% (level II).^21-23

Management

An approach to managing carotid artery stenosis is shown in Figure 1 .

Figure 1. Management of carotid artery stenosis.

High-risk patients present with symptoms of motor weakness, speech deficit, hemispatial deficit, and hemianopia; low-risk patients present with only sensory deficit or amaurosis fugax.

Symptomatic disease.

Patients presenting to their family physicians with a TIA should immediately be given acetylsalicylic acid (80 to 325 mg). Patients who have a TIA while taking ASA should be given clopidogrel. High-risk patients presenting within a few hours of onset of symptoms of a TIA should undergo urgent duplex scanning. If a >70% stenosis is detected in the carotid artery contralateral to the side of somatic symptoms, patients should immediately be evaluated by a vascular surgeon with a view to having CEA within 48 hours of presentation.

High-risk patients who present after 48 hours but within 7 days should have CEA within 7 days of onset of symptoms. Patients presenting between 7 days and 30 days after a TIA should have surgery within 30 days; patients presenting between 30 and 90 days after symptom onset should have surgery within 90 days. Recent studies have shown that high-risk patients are likely to benefit from CEA as early as possible up to 90 days after an initial TIA (level II).^9-13 Patients presenting 90 days or more after onset of symptoms could be offered elective CEA.

Low-risk patients (amaurosis fugax, sensory deficit only) should have an elective CEA within 90 days (level II).^24,25 Two randomized controlled trials confirmed the benefit of surgery over medical therapy for patients with symptoms and >70% carotid stenosis (level I).^7,8 Number needed to treat to prevent one stroke at 2 years is nine. Symptomatic patients with 50% to 69% carotid stenosis benefited marginally from surgery.

The patients who benefited from CEA had more severe stenosis, were 75 or older, were men, had had a stroke within the last 3 months, and had hemispheric symptoms. Patients who benefited from medical therapy were those with less severe stenosis, were younger than 75, were women, had had a stroke more than 3 months ago, and had visual symptoms. Number needed to treat to prevent one stroke at 5 years was 12 for men and 67 for women (level I).²⁶ Symptomatic patients with <50% stenosis did not benefit from surgical intervention (level I).²⁶

The main reason for routine brain CT scanning after a TIA is to exclude causes such as tumour, arteriovenous malformation, hydrocephalus, intracranial aneurysm, or sufficient hemorrhage to contraindicate surgical treatment. The yield of this test is <1%.²⁷ In fact, ipsilateral CT scan defects were found in 20% of patients who had asymptomatic carotid stenosis and in 33% of patients with a history of TIA. Defects seen were all infarcts. No tumours, arteriovenous malformations, or any other intracranial abnormalities were detected.²⁸ Management of patients with TIAs and corresponding carotid stenosis was not changed by knowing the results of preoperative CT brain scans, so routine scans are unnecessary for this population.²⁹

Asymptomatic carotid stenosis

Patients who have >60% carotid stenosis might benefit from CEA. Two randomized studies have confirmed this benefit (level I).^14,30 Surgeons who perform this surgery, however, must themselves have a perioperative stroke rate of <3%. Patients should be medically fit to undergo this surgery; their risk of adverse perioperative cardiovascular events should be low.

What is the best medical therapy?

Aggressive medical therapy has been shown to reduce atherosclerotic carotid artery stenosis and prevent symptoms.³¹ Antiplatelet therapy has been shown to reduce risk of fatal stroke by 16% and non-fatal stroke by 28%.³² Combined ASA and warfarin therapy at an international normalized ratio of 1.8 in patients with sinus rhythm proved no better than ASA alone.³³ Lipid-lowering therapy reduced risk of stroke by 25%.³⁴ Angiotensin-converting enzyme inhibitors decreased stroke rates by 32%^35-37 and were also shown to slow progression of atherosclerosis in general.³⁸

Effective management of hypertension decreases stroke rates by 28% to 40%.^39-41 Smoking cessation has been shown to decrease women’s risk of stroke by 48%.^42-46 Table 3 summarizes the benefits of aggressive risk-factor reduction. Any patient with carotid artery stenosis, whether symptomatic or asymptomatic, should be taking the therapies shown in Table 3. In fact, any patient with atherosclerotic disease (ie, carotid artery disease), peripheral arterial occlusive disease, or coronary artery disease should be taking these medications.

Table 3. Relative risk reduction for stroke.

Beneficial effects of preventive therapy.

Carotid intervention

The criterion standard intervention has been CEA. Indications for surgery should be correlated to a surgeon’s personal results. Acceptable results for stroke and death following CEA are shown in Table 4.⁴⁷ Carotid angioplasty and stenting are gaining popularity as treatments for carotid stenosis. Current results at 1 year are comparable to CEA as shown by the results of the SAPPHIRE (Stenting and angioplasty with protection in patients at high risk for endarterectomy) study presented at the 15th Annual Transcatheter Cardiovascular Therapeutics Symposium in September 2003.⁴⁸ Further results from randomized trials are awaited.

Table 4.

Acceptable risks associated with carotid endarterectomy

*Crescendo transient ischemic attacks, evolving stroke.

Conclusion

Because they often see patients with the first signs of cerebral ischemia, family doctors should be aware of the criteria for, and need for, early referral for surgery, where indicated. Careful selection of cases will help minimize the number of unnecessary referrals. Patients not requiring surgery could benefit from aggressive medical management.

Levels of evidence.

Level I: At least one properly conducted randomized controlled trial, systematic review, or meta-analysis

Level II: Other comparison trials, non-randomized, cohort, case-control, or epidemiologic studies, and preferably more than one study

Level III: Expert opinion or consensus statements

Biography

Dr Louridas is an Associate Professor and Section Head of Vascular Surgery, and Dr Junaid is an Assistant Professor and Head of Vascular Medicine, at the University of Manitoba Health Sciences Centre and at St Boniface General Hospital in Winnipeg.