Carotid artery stenosis
|Carotid artery stenosis|
|Other names||TIA - carotid artery|
|Carotid Artery Disease|
Signs and symptoms
The common carotid artery is the large artery whose pulse can be felt on both sides of the neck under the jaw. On the right side it starts from the brachiocephalic artery (a branch of the aorta), and on the left side the artery comes directly off the aortic arch. At the throat it forks into the internal carotid artery and the external carotid artery. The internal carotid artery supplies the brain, and the external carotid artery supplies the face. This fork is a common site for atherosclerosis, an inflammatory build-up of atheromatous plaque inside the common carotid artery, or the internal carotid arteries that causes them to narrow.
The plaque can be stable and asymptomatic, or it can be a source of embolization. Emboli break off from the plaque and travel through the circulation to blood vessels in the brain. As the vessels get smaller, an embolus can lodge in the vessel wall and restrict the blood flow to parts of the brain. This ischemia can either be temporary, yielding a transient ischemic attack, or permanent resulting in a thromboembolic stroke.
Clinically, risk of stroke from carotid artery stenosis is evaluated by the presence or absence of symptoms and the degree of stenosis on imaging.
Transient ischemic attacks (TIAs) are a warning sign, and may be followed by severe permanent strokes, particularly within the first two days. TIAs by definition last less than 24 hours and frequently take the form of a weakness or loss of sensation of a limb or the trunk on one side of the body, or the loss of sight (amaurosis fugax) in one eye. Less common symptoms are artery sounds (bruits), or ringing in the ears (tinnitus).
The common carotid artery is the large vertical artery in red. The blood supply to the carotid artery starts at the arch of the aorta (bottom). The carotid artery divides into the internal carotid artery and the external carotid artery. The internal carotid artery supplies the brain. Plaque often builds up at that division, and causes a narrowing (stenosis). Pieces of plaque can break off and block the small arteries above in the brain, which causes a stroke. Plaque can also build up at the origin of the carotid artery at the aorta.
Carotid artery stenosis is usually diagnosed by color flow duplex ultrasound scan of the carotid arteries in the neck. This involves no radiation, no needles and no contrast agents that may cause allergic reactions. This test has good sensitivity and specificity.
Typically duplex ultrasound scan is the only investigation required for decision making in carotid stenosis as it is widely available and rapidly performed. However, further imaging can be required if the stenosis is not near the bifurcation of the carotid artery.
One of several different imaging modalities, such as a computed tomography angiogram (CTA) or magnetic resonance angiogram (MRA) may be useful. Each imaging modality has its advantages and disadvantages - Magnetic resonance angiography and CT angiography with contrast is contraindicated in patients with chronic kidney disease, catheter angiography has a 0.5% to 1.0% risk of stroke, MI, arterial injury or retroperitoneal bleeding. The investigation chosen will depend on the clinical question and the imaging expertise, experience and equipment available.
The need for screening for carotid artery stenosis depends on whether someone is experiencing symptoms arising from the stenosis or has risk factors for the development of carotid artery disease.
While routine population screening is not advised, the American Heart Association recommends screening for people who don’t have symptoms of carotid stenosis but have been diagnosed with related medical conditions or have risk factors for carotid artery disease. Screening is recommended for people who have:
- Vascular disease elsewhere in the body, including:
- Two or more of the following risk factors:
The American Heart Association also recommends screening if a physician detects a carotid bruit, or murmur, over the carotid artery by listening through a stethoscope during a physical exam.
For people with symptoms, the American Heart Association recommends initial screening using ultrasound (see diagnosis below).
The goal of treating carotid artery stenosis is to reduce the risk of stroke. The type of treatment depends on the severity of the disease and includes:
- Lifestyle modifications including smoking cessation, eating a healthy diet and reducing sodium intake, losing weight, and exercising regularly.
- Medications to control high blood pressure and high levels of lipids in the blood.
- Surgical intervention for carotid artery revascularization.
Clinical guidelines (such as those of the American Heart Association (AHA) and National Institute for Clinical Excellence (NICE)) recommend that all patients with carotid stenosis be given medication, usually blood pressure lowering medications, anti-clotting medications, anti-platelet medications (such as aspirin or clopidogrel), and especially statins (which were originally prescribed for their cholesterol-lowering effects but were also found to reduce inflammation and stabilize plaque).
According to the American Heart Association, surgical intervention beyond medical management is based upon whether patients have symptoms:
- Asymptomatic patients: assessment of other medical conditions, life expectancy, and other individual factors; evaluation of the risks versus benefits; and patient preference are considered when determining whether surgical intervention should be performed.
- Symptomatic patients: it is recommended that patients who have experienced a transient ischemic attack or non-severely disabling acute ischemic stroke undergo surgical intervention.
All surgical interventions for carotid revascularization (carotid endarterectomy, carotid stenting, and transcarotid artery revascularization) carry some risk of stroke; however, where the risk of stroke from medical management alone is high, intervention may be beneficial.
Carotid Endarterectomy (CEA)
In selected trial participants with asymptomatic severe carotid artery stenosis, carotid endarterectomy reduces the risk of stroke in the next 5 years by 50%, though this represents a reduction in absolute incidence of all strokes or perioperative death of approximately 6%. In most centres, carotid endarterectomy is associated with a 30-day stroke or mortality rate of < 3%; some areas have higher rates.
NICE and other guidelines also recommend that patients with symptomatic carotid stenosis be given carotid endarterectomy urgently, since the greatest risk of stroke is within days. Carotid endarterectomy reduces the risk of stroke or death from carotid emboli by about half.
For people with stenosis but no symptoms, the interventional recommendations are less clear. Such patients have a historical risk of stroke of about 1–2% per year. Carotid endarterectomy has a surgical risk of stroke or death of about 2–4% in most institutions. In the large Asymptomatic Carotid Surgery Trial (ACST) endarterectomy reduced major stroke and death by about half, even after surgical death and stroke was taken into account. According to the Cochrane Collaboration the absolute benefit of surgery is small. For intervention using stents, there is insufficient evidence to support stenting rather than open surgery, and several trials, including the ACST-2, are comparing these 2 procedures.
Carotid Artery Stenting (CAS)
The largest clinical trial performed, CREST (The Carotid Revascularization Endarterectomy versus Stenting Trial), randomized patients at risk for a stroke from carotid artery blockage to either open surgery (carotid endarterectomy) or carotid artery stenting. This trial followed patients for 4 years and found no overall difference in the primary end point of both treatment arms (myocardial infarctions, any perioperative strokes or ipsilateral strokes within 4 years, or death during procedure). Patients assigned to the surgical arm experienced more perioperative myocardial infarctions compared to the stenting group; however, the difference was not statistically significant (6.8% vs or 7.2% HR for stenting is 1.1 CI 0.81–1.51 P value 0.51) whereas patients assigned to the carotid stent arm experienced more periprocedural strokes compared to endarteretomy (6.4% vs 4.7% HR for stenting 1.5 P-0.03). There was no mortality difference and no difference for major (disabling) strokes between surgery and stenting. It was noted that there did seem to exist an age cutoff where below 75 years old endarterectomy and stenting showed equivalent results, while in patients over 75 endarterectomy offered a better risk profile. The CREST trial was not designed for subgroup analysis and thus not powered enough to draw any statistically significant conclusions. A later study published in 2013 evaluated how these perioperative complications affect long-term survival. This study showed that experiencing a stroke within the first year conferred a two-fold lower survival rate (Hazard Ratio(HR) 6.6 [CI 3.7–12]) than those who experienced a perioperative myocardial infarction at two years post intervention (HR 3.6 [CI 2–6.8]). This difference in mortality, however, converges and becomes negligible at 5 years (HR 2.7 [CI 1.7–4.3] vs HR 2.8 [CI 1.8–4.3]). A 2010 study found benefits (reduced strokes) from carotid endarterectomy in those without symptoms who are under 75.
Transcarotid Artery Revascularization (TCAR)
Transcarotid artery revascularization (TCAR) is a new procedure for carotid revascularization. It is currently approved in the U.S. for people with carotid artery disease who are at risk for open surgery, such as those who have undergone a previous CEA and the elderly. The procedure involves temporarily reversing blood flow, which prevents stroke-causing debris from reaching the brain, and implanting a stent into the carotid artery to stabilize the plaque and prevent a future stroke. An added advantage of TCAR is that is performed in less than half the time of CEA, limiting stress on the heart and significantly cutting the risk of stroke or heart attack during the procedure. As of May 2019, it has been reported that more than 10,000 TCAR procedures have been performed worldwide. TCAR has been studied in numerous clinical trials, including ROADSTER 1 and 2. In the ROADSTER 1 trial, the 30-day stroke rate was 1.4 percent – the lowest stroke rate at the time for any prospective trial of carotid stenting. In the real-world ROADSTER-2 trial, the stroke rate was 0.6% and the combined stroke and death rate was 0.8 percent for patients with 30-day follow-up. An additional study using data from the Society for Vascular Surgery’s TCAR Surveillance Project evaluated 5,716 patients receiving TCAR compared to 44,442 patients receiving CEA between 2015 and 2018, finding no statistical differences between TCAR and CEA for in-hospital stroke or in-hospital stroke and death. An additional analysis 5,160 patients in each group using propensity score matching based on comorbidities and demographics found patients treated with TCAR had significantly lower odds of composite in-hospital stroke, death, and myocardial infarction compared to CEA.
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