Dr. John Doe is a 67-year-old vascular surgeon and is self-referred for evaluation of a carotid bruit found on a routine insurance physical examination. He has no focal neurologic symptoms and reports no history consistent with a stroke or transient ischemic attack (TIA). He has a history of hypertension, dyslipidemia, and non–insulin-dependent diabetes all well-controlled on medical therapy. Physical exam confirms a right-sided bruit in the neck, and the rest of the physical exam is unremarkable. His medications include a daily baby aspirin (81 mg), atorvastatin (20 mg), lisinopril (10 mg), hydrochlorothiazide (12.5 mg), and metformin (500 mg). Duplex ultrasound reveals an 80% to 89% stenosis of his right internal carotid artery and 20% to 49% stenosis of his left internal carotid artery. What are the consequences of Dr. Doe’s carotid artery disease? How should his case be approached?
EPIDEMIOLOGY AND NATURAL HISTORY
Nearly 800,000 strokes occur each year in the United States, and over 130,000 Americans die annually from stroke.1 Stroke is the third leading cause of mortality in the United States, and among survivors, 15% to 30% are permanently disabled.1,2 Atherosclerotic carotid artery disease is responsible for 80% of new noncardioembolic strokes.3-6 Carotid plaque most often causes cerebrovascular events due to plaque rupture with atheroembolization, rather than carotid artery occlusion (<20% of ischemic strokes) with thrombosis (Figure 31-1).4
Angiogram of patient with symptomatic carotid artery stenosis. Notice the ulcerated plaque in the internal carotid artery.
The natural history of carotid artery stenosis depends on the presence of symptoms (TIA, stroke, amaurosis fugax). Symptomatic patients have a 5- to 10-fold risk of stroke when compared to asymptomatic patients. Asymptomatic patients with carotid artery stenosis outnumber symptomatic patients by 4:1. Approximately 5% to 10% of patients over age 65 have a carotid stenosis >50%, with 1% having a stenosis ≥75%.7. Because the majority (≥80%) of ischemic strokes have no warning symptoms,4 the management of asymptomatic carotid atherosclerosis with revascularization or medical therapy is important.3,8
Transient focal neurologic symptoms are associated with a 30% risk of stroke within 6 months.9,10 TIA is currently defined as a transient episode of neurologic dysfunction caused by focal brain, spinal cord, or retinal ischemia, without acute infarction, based on pathologic, imaging, and other objective evidence and/or clinical evidence. Stroke, central nervous system (CNS) infarction, is defined by neuropathologic, neuroimaging, and/or clinical evidence of permanent injury. However, many of the initial studies that illustrated the natural history of this disease as well as our current standards of practice predated this updated definition and included only a clinical definition of infarction.11
In the 1990s, 2 larger randomized controlled trials (the Asymptomatic Carotid Atherosclerosis Study [ACAS] and the ...