Chapter 2-5: Carotid Artery Stenosis (CAS) Screening

What is the burden of disease?

1. The estimated prevalence of significant CAS (70–99%) in the general population is about 0.5–1%.

2. The contribution of significant CAS to morbidity or mortality from stroke is not known, nor is the natural progression of asymptomatic CAS.

Is it possible to identify a high-risk group that might especially benefit from screening?

1. Risk factors for CAS include hypertension, heart disease, smoking, older age, male sex, hypercholesterolemia, and diabetes mellitus.

2. There are no validated, reliable risk assessment tools that reliably identify patients with clinically important CAS.

What is the quality of the screening test?

1. For the detection of > 70% stenosis, carotid duplex ultrasonography has a sensitivity of 90% and a specificity of 94%.

2. For the detection of > 50% stenosis, the sensitivity is 98% and the specificity is 88%.

3. There can be wide variation in measurements done in different laboratories.

4. Screening for bruits on physical exam has poor reliability and sensitivity.

Does screening reduce morbidity or mortality?

1. There are no studies on the benefits and harms of screening for asymptomatic CAS.

2. There have been 3 randomized controlled trials of carotid endarterectomy versus medical therapy for treating asymptomatic CAS (Asymptomatic Carotid Atherosclerosis Study, Veterans Affairs Cooperative Study, and Asymptomatic Carotid Surgery Trial).

   1. Pooling the results of all 3 trials demonstrates that the surgical group had a 2% absolute reduction in perioperative stroke or death and subsequent ipsilateral stroke and a 3.5% reduction in death, perioperative stroke, or any subsequent stroke.

   2. These results may not be generalizable due to the highly selected participants and surgeons.

   3. The medical treatment was not well defined or standardized.

   4. These data are from the 1980s and 1990s and do not reflect current standard care such as aggressive control of BP and lipids.

   5. The Carotid Revascularization and Medical Management for Asymptomatic Carotid Stenosis Trial (CREST-2) in which patients are randomized to carotid endarterectomy versus medical therapy, or carotid artery stenting versus medical therapy, is underway and will provide more current data.

3. All abnormal ultrasounds need to be confirmed by digital subtraction angiography, which has a stroke rate of 1%, or by magnetic resonance angiography or CT angiography, both of which are < 100% accurate.

4. 30-day perioperative stroke or death rates in asymptomatic patients range from 2.4% to 3.3%, with rates for women at the higher end of the range; in some states, rates are over 5%.

5. The perioperative myocardial infarction rate is 0.8–2.2%.

6. The 30-day stroke or mortality rate after carotid artery stenting is 3.1–3.8%

What are the current guidelines?

1. USPSTF (2014)

   1. Recommends against screening for asymptomatic CAS in the general adult population

   2. Grade D recommendation, based on moderate certainty that the benefits of screening do not outweigh the harms.

2. The American Heart Association (2010), the American Stroke Association (2011), and the Society for Vascular Surgery (2011) do not recommend population-based screening.

3. Other societies, including the American College of Cardiology and the American College of Radiology do not recommend routine screening, although do recommend screening patients with bruits and to consider screening in ...