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Chapter Summary

This chapter discusses the epidemiology, natural history, diagnostic imaging modalities, and treatment options for atherosclerotic carotid artery disease as it relates to acute ischemic stroke. Significant atherosclerotic carotid artery disease (≥50% diameter stenosis) is common in Medicare patients (5%–10%); it is responsible for the vast majority of noncardioembolic acute strokes caused by plaque rupture with atheroembolization. Approximately 90% of the stroke risk is due to modifiable risk factors, such as hypertension, obesity, hyperglycemia, and hyperlipidemia, and 74% can be attributed to behavioral risk factors, such as tobacco smoking, sedentary lifestyle, and unhealthy diet. Doppler ultrasound (DUS) is the preferred noninvasive imaging tool for risk assessment of carotid disease, with cross-sectional multiplanar imaging [either computerized tomographic angiography (CTA) or magnetic resonance angiography (MRA)] reserved for specific cases. The cornerstone of therapy for stroke prevention in patients with carotid artery atherosclerotic disease is risk factor modification and guideline-directed medical therapy (GDMT), with revascularization (stent or surgery) indicated for selected symptomatic patients (see Fuster and Hurst’s Central Illustration). Current recommendations regarding revascularization in asymptomatic patients with significant carotid stenosis are uncertain and await the completion of an ongoing international randomized trial (CREST-2).

INTRODUCTION

Epidemiology and Natural History

Atherosclerotic carotid artery disease is responsible for 80% of new noncardioembolic strokes. Cerebrovascular events are most often caused by carotid plaque rupture with atheroembolization, rather than carotid artery occlusion (<20% of ischemic strokes) with thrombosis. Of all strokes, 87% are ischemic, 10% are due to intracranial hemorrhage, and 3% are due to subarachnoid hemorrhage.

Approximately 5% to 10% of patients over age 65 have >50% carotid artery stenosis, with 1% having a stenosis ≥75%. The natural history of patients with carotid artery stenosis is strongly influenced by the presence of focal neurologic symptoms, such as transient ischemic attack (TIA), stroke, and amaurosis fugax. Symptomatic patients have a 5- to 10-fold increased risk of stroke compared to asymptomatic patients, and a TIA is associated with a 20% increased risk of stroke within 90 days.1 Asymptomatic patients with significant carotid artery stenosis outnumber symptomatic patients by 4:1.

Approximately 90% of stroke risk is due to modifiable factors, such as hypertension, obesity, hyperglycemia, and hyperlipidemia, and 74% can be attributed to behavioral risk factors, such as tobacco smoking, sedentary lifestyle, and unhealthy diet.1 A small number of all strokes (approximately 12%) are heralded by a TIA, making guideline-directed medical therapy (GDMT) and risk factor modification the keys to stroke prevention in patients with carotid artery disease.

There are no randomized trials to support screening asymptomatic patients (primary prevention) for carotid stenosis to prevent stroke. In 2014, the US Preventive Services Task Force (USPSTF) determined that the potential harms associated with screening for asymptomatic carotid stenosis (leading to unnecessary surgery) far outweighed the potential benefit (stroke ...

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