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Management of Asymptomatic Carotid Stenosis

Technology Assessment Report

Gowri Raman, MD, MS, Georgios D Kitsios, MD, PhD, Denish Moorthy, MBBS, MS, Nira Hadar, MS, Issa J Dahabreh, MD, MS, Thomas F O'Donnell, MD, David E Thaler, MD, PhD, FAHA, Edward Feldmann, MD, and Joseph Lau, MD.

Tufts Evidence-based Practice Center
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Excerpt

Stroke is a leading cause of death in the United States. Although the number of deaths from stroke has declined in recent years, it continues to be a major public health problem in the United States, with an estimated $34.3 billion in direct cost and indirect cost of stroke in the year 2008. Carotid artery stenosis represents an important risk factor for ischemic stroke, which accounts for nearly 90 percent of all strokes among U.S. men and women. Carotid artery stenosis is increasingly prevalent from the fifth decade of life onward. Patients with vascular disease and multiple risk factors (e.g., diabetes, hypertension, hyperlipidemia, and smoking) have a higher probability of having asymptomatic carotid stenosis. Since carotid artery atherosclerosis can largely proceed silently and unpredictably, the first manifestation can be a debilitating or fatal stroke. Asymptomatic carotid artery stenosis affects approximately 7 percent of women and over 12 percent of men, older than 70 years of age. Clinically important stenosis, at which the risk of stroke is increased, is defined as stenosis of over 50 or 60 percent. Natural history studies have reported that patients with asymptomatic carotid stenosis are at an increased risk of ipsilateral carotid territory ischemic stroke ranging from 5 to 17 percent.

The goal of management of asymptomatic carotid stenosis is to decrease the risk of stroke and stroke-related deaths. However, screening asymptomatic patients for carotid stenosis is not part of common clinical practice as noted in a review by the U.S. Preventive Services Task Force from 1996, which concluded that evidence was insufficient to recommend either for or against screening. As the general U.S. population ages, and with the availability of noninvasive imaging studies, asymptomatic carotid artery stenosis may be more frequently detected in the course of patient management. Auscultation of the carotid arteries to listen for bruits is by convention an initial means of clinical assessment of high-risk patients, but the presence of bruits is not necessarily indicative of significant stenosis. Since carotid auscultation has limited sensitivity in detecting significant carotid stenosis, additional imaging modalities including digital subtraction angiography (DSA), Doppler ultrasound (DUS), computed tomography angiography (CTA), and magnetic resonance angiography (MRA) are being increasingly utilized.

The most commonly used measurement method of carotid stenosis used in clinical trials or most common angiographic method was introduced in the North American Symptomatic Carotid Endarterectomy Trial (NASCET). In the NASCET method, the stenosis is measured as the ratio of the linear luminal diameter of the narrowest portion of the artery's diseased segment divided by the diameter of the healthy distal carotid artery (above the post-stenotic dilation). An alternative method was used in the European Carotid Surgery Trial (ECST), which utilized the estimated carotid bulb at the site of maximal stenosis as the denominator. The ECST method tends to yield higher degrees of stenosis, but measurements made by each method can be converted to those of the other using a simple arithmetic equation. According to the 2003 Society of Radiologists in Ultrasound consensus criteria, a carotid stenosis is not quantified as an exact percentage of luminal stenosis but can be classified by range of stenoses that represent clinically relevant categories (normal, < 50 percent, 50-69 percent, ≥ 70 percent but less than near occlusion, near occlusion, or total occlusion).

Therapeutic options in asymptomatic carotid stenosis include medical therapy alone, carotid endarterectomy (CEA) and medical therapy, or carotid angioplasty and stenting (CAS) and medical therapy. However, the optimal therapeutic management strategy for patients with asymptomatic carotid stenosis is unclear. The Centers for Medicare and Medicaid Services (CMS) is interested in a systematic review of the literature on these three treatment strategies in patients with asymptomatic carotid stenosis. The Coverage and Analysis Group at the CMS requested the present report from the Technology Assessment Program (TAP) at the Agency for Healthcare Research and Quality (AHRQ). AHRQ assigned this report to the Tufts Evidence-based Practice Center (Tufts EPC) (Contract number, HSSA 290 2007 10055 I).

This report is based on research conducted by the Tufts Evidence-based Practice Center under contract to the Agency for Healthcare Research and Quality (AHRQ), Rockville, MD (Contract No. 290 2007 10055 1). The findings and conclusions in this document are those of the author(s) who are responsible for its contents; the findings and conclusions do not necessarily represent the views of AHRQ. No statement in this article should be construed as an official position of the Agency for Healthcare Research and Quality or of the U.S. Department of Health and Human Services.

The information in this report is intended to help health care decision-makers; patients and clinicians, health system leaders, and policymakers, make well-informed decisions and thereby improve the quality of health care services. This report is not intended to be a substitute for the application of clinical judgment. Decisions concerning the provision of clinical care should consider this report in the same way as any medical reference and in conjunction with all other pertinent information, i.e., in the context of available resources and circumstances presented by individual patients.

This report may be used, in whole or in part, as the basis for development of clinical practice guidelines and other quality enhancement tools, or as a basis for reimbursement and coverage policies. AHRQ or U.S. Department of Health and Human Services endorsement of such derivative products may not be stated or implied.

Disclosure: None of the investigators has any affiliations or financial involvement related to the material presented in this report.

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