Carotid intervention (endarterectomy or stenting, depending on the clinical setting) is recommended generally in symptomatic patients with stenosis of more than 70% and in selected asymptomatic low-risk patients and symptomatic patients with stenosis of 50 to 69%. The latest article in our Clinical Practice series comes from Dr. James C. Grotta of the University of Texas Medical School at Houston.
Carotid artery disease causes approximately 10 to 20% of strokes, and appropriate intervention is important for secondary and possibly primary stroke prevention. The degree of carotid artery stenosis is the strongest determinant of stroke risk.
• When carotid artery stenosis causes symptoms, what is the usual mechanism and typical presentation?
Atherosclerotic plaques produce symptoms most often by distal embolism to branches of the retinal or cerebral arteries; hemodynamically significant luminal stenosis may also result in critical reduction of perfusion. Most emboli result from activation of platelets on the plaque surface, and less frequently cholesterol particles. An “unstable plaque” with cap rupture may be the culprit. Emboli to retinal arterioles lead to transient monocular blindness (amaurosis fugax). Emboli to the cerebral circulation most often lodge in middle cerebral artery branches but can also end up in anterior or posterior cerebral branches depending on the anatomy of the circle of Willis. If patients who have had a stroke attributed to carotid disease are questioned closely, at least 50% report preceding symptoms consistent with transient ischemic attack. Stroke syndromes related to carotid disease involve some combination of motor or sensory symptoms involving the contralateral face, arm or leg, and speech, language or visual symptoms.
• What is the sensitivity and specificity of a carotid bruit in detecting internal artery carotid disease?
A carotid bruit may signal the presence of clinically significant internal carotid artery disease; this finding is present in 70 to 89% of patients with 2-mm luminal narrowing. However, it is nonspecific, as is heard in 5% of patients ages 45 to 80 years in the absence of significant internal carotid disease.
Morning Report Questions
Q: What are the principles of medical management of carotid artery stenosis?
A: Aggressive treatment of modifiable risk factors for carotid atherosclerosis — especially smoking, hypertension, and hyperlipidemia — is central to stroke prevention. In patients with severe carotid artery stenosis with hypertension, treatment goals must take into account the risk of reduced cerebral perfusion with overly aggressive treatment, pending correction of stenosis. Statin drugs are effective for both primary and secondary stroke prevention, and may produce stabilization and even regression of intimal-media thickness of the carotid artery wall. For long-term secondary stroke prevention, current guidelines recommend aspirin, clopidogrel, or the combination of aspirin and dipyridimole. The combination of aspirin and clopidogrel is not recommended due to increased bleeding risk, but this combination is routinely used transiently (e.g., 1 to 3 months) after carotid-artery stenting, based on data extrapolated from coronary stenting.
Q: What are the indications for surgical or interventional management of carotid artery stenosis?
A: In aggregate, the available data support carotid endarterectomy or carotid stenting in most patients with symptomatic stenosis greater than 70% (number needed to treat to prevent one stroke at 24 months, 6), in selected patients with symptomatic stenosis of 50 to 69% (number needed to treat to prevent one stroke at 5 years, 15), and in a selected subset of asymptomatic patients with low periprocedural risk (e.g., no significant cardiopulmonary or other severe comorbidity at an age younger than 70 years) (number needed to treat to prevent one stroke at 5 years, 17). Carotid endarterectomy is currently considered the preferable intervention for most patients, although selected patients (e.g., less than age 70 with favorable anatomy or symptomatic patients with severe stenosis at high risk for carotid endarterectomy) may benefit more from carotid stenting.