Atherosclerosis is the most common cause of carotid artery stenosis, accounting for more than 90% of cases. In addition, there are rare causes such as aortitis, trauma and radiation injury. Carotid artery stenosis due to different causes varies greatly in terms of clinical manifestations, diagnostic methods, treatment and relationship with stroke. Atherosclerotic carotid stenosis, especially at the bifurcation of the common carotid artery, is directly related to ischemic stroke, and its treatment is important in stroke prevention.
Carotid artery stenosis due to atherosclerosis is most commonly seen in middle-aged and elderly people and is often associated with multiple cardiovascular risk factors. Carotid artery stenosis due to cephalothoracic aortitis is more common in adolescents, especially in young women. Carotid artery stenosis due to injury or radiation has a history of corresponding injury or radiation exposure prior to the onset of the disease.
Clinically, carotid stenosis is classified into two categories: symptomatic and asymptomatic, depending on whether the stenosis produces symptoms of cerebral ischemia.
Symptomatic carotid stenosis
Cerebral ischemic symptoms: tinnitus, vertigo, blackness, blurred vision, dizziness, headache, insomnia, memory loss, drowsiness, and dreaminess may be present. Ocular ischemia manifests as vision loss, hemianopia, diplopia, etc.
TIA localized by transient loss of neurological function, clinical manifestations are transient impairment of sensory or motor function of one limb, transient monocular blindness or aphasia, etc., usually lasting only a few minutes, with complete recovery within 24h after onset. There are no focal lesions on imaging.
Ischemic stroke: common clinical symptoms include sensory impairment of one limb, hemiparesis, aphasia, cerebral nerve damage, and in severe cases, coma, with corresponding neurological signs and imaging features.
Asymptomatic carotid stenosis Many patients with carotid stenosis do not have any clinical signs and symptoms of the nervous system. Sometimes, only a weakened or absent carotid pulsation is detected during physical examination, and a vascular murmur is heard at the root of the neck or at the carotid line. Asymptomatic carotid stenosis, especially severe stenosis or plaque ulceration, is recognized as a “high-risk lesion” and is receiving increasing attention.
Laboratory tests
No relevant data are available.
Other ancillary tests
Doppler-ultrasound Doppler-ultrasound is the preferred non-invasive carotid artery examination that combines Doppler flowmetry and ultrasound imaging in real time, and is simple, safe and inexpensive. It can not only display the anatomical image of carotid artery and perform morphological examination of plaque, such as distinguishing intraplaque bleeding from plaque ulceration, but also display the arterial blood flow, flow rate, flow direction and intra-arterial thrombus. With an accuracy of over 95% in diagnosing the degree of carotid stenosis, Doppler-ultrasound has been widely used in the screening and follow-up of carotid stenotic lesions.
The shortcomings of ultrasonography include the inability to examine lesions in the intracranial internal carotid arteries; the results are easily influenced by the skill level of the operator.
Magnetic resonance angiography Magnetic resonance angiography (MRA) is a noninvasive vascular imaging technique that clearly shows the three-dimensional morphology and structure of the carotid arteries and their branches, and can reconstruct intracranial arterial images. The carotid vessels have a linear profile and are particularly suitable for MRA, which can accurately visualize thrombotic plaques, the presence or absence of clotted aneurysms and intracranial arteries, and is extremely helpful for diagnosis and protocol determination.
The prominent disadvantage of MRA is that slow or complex flow often results in signal loss and exaggerated stenosis. It also has limitations in showing sclerotic plaques. MRA is contraindicated in patients with metal retention (e.g., metal stents, pacemakers, or metal prostheses).”
CT angiography CT angiography (CTA) is a non-invasive angiographic technique developed on the basis of spiral CT. It is performed by injecting contrast into the blood vessels and performing a volumetric scan when the concentration of contrast in the circulating blood or target vessel is at its peak, followed by processing to obtain a digital stereoscopic image. CTA is suitable for carotid arteries in the extracranial segment, mainly because the carotid artery course is perpendicular to the CT section, thus avoiding the disadvantage of relatively insufficient resolution for vessels with horizontal course during spiral CT scanning. the advantage of CTA can directly show calcified plaques. At present, the surface shaded display (SSD) and the maximum intensity projection (MIP) are generally used for 3D revascularization. However, SDD cannot directly show the density difference CTA technique has been used more often in the diagnosis of carotid artery stenosis, but the technique is not mature enough and needs to be improved by further accumulation of experience.
Digital subtraction angiography At present, although non-invasive imaging methods have been more and more widely used for the diagnosis of carotid artery lesions, each method has definite advantages and disadvantages. High-resolution MRA, CTA, and Doppler-ultrasound imaging are of great value for primary diagnosis and follow-up. Although angiography is no longer used for screening, primary diagnosis and follow-up, digital subtraction angiography (DSA) remains the “gold standard” for the diagnosis of carotid artery stenosis in terms of accurate evaluation of lesions and determination of treatment options. DSA can provide detailed information about the location, extent and degree of the lesion and the formation of side branches; help determine the nature of the lesion such as ulcers, calcified lesions and thrombosis; and understand coexisting vascular lesions such as aneurysms and vascular malformations. Aneurysms, vascular malformations, etc. Arteriography can provide the most valuable imaging basis for surgical and interventional treatment.
Arteriography is an invasive and expensive test, and the literature reports a complication rate of 0.3% to 7%. The main complications are cerebral vasospasm, dislodgement of plaque causing stroke, cerebral embolism and contrast allergy. Renal impairment, vascular injury and hematoma at the puncture site, and pseudoaneurysm.
Methods of measuring carotid stenosis Although noninvasive tests such as ultrasound, computerized tomography (CT), and magnetic resonance imaging (MRI) are increasingly useful in the diagnosis of carotid stenosis, arteriography is still the However, arteriography is still the “gold standard” for the diagnosis of carotid stenosis. The determination of the degree of carotid artery stenosis is based on arteriography results. Different research departments have used different measurement methods, and there are 2 commonly used international measurement methods, namely the North American Symptomatic Carotid Endarterectomy Trial Collaborators (NASCET) criteria and the European Carotid European Carotid Surgery Trial collaborators Group (ECST) criteria (Figure 1).
NASCET stenosis = (1 – narrowest internal carotid artery flow width / normal internal carotid artery diameter distal to the stenotic lesion) × 100%
ECST stenosis = (1 – narrowest flow width of the internal carotid artery / simulated internal diameter of the dilated internal carotid artery) × 100%
Both of the above methods classify the degree of internal carotid artery stenosis into 4 grades.
Mild stenosis with <30% narrowing of the internal diameter of the artery
Moderate stenosis, where the internal diameter of the artery is reduced by 30% to 69%.
Severe stenosis, where the internal diameter of the artery is reduced by 70% to 99%.
Complete occlusion.
The treatment of carotid stenosis is aimed at improving cerebral blood supply, correcting or relieving the symptoms of cerebral ischemia; preventing TIA and ischemic stroke. Treatment is based on the degree of carotid stenosis and the patient’s symptoms and includes medical treatment, surgical treatment and interventional treatment.
Conservative medical treatment is aimed at reducing the symptoms of cerebral ischemia, reducing the risk of stroke, and controlling existing diseases such as hypertension, diabetes, hyperlipidemia and coronary heart disease. Internal conservative treatment includes the following.
Reducing body weight.
Quit smoking.
Limiting alcohol consumption.
Anti-platelet aggregation therapy: Many large randomized, prospective multicenter clinical trials have confirmed that anti-platelet aggregation drugs can significantly reduce the incidence of cerebral ischemic disease, commonly used in clinical practice are aspirin, ticlopidine (trade name RENKELA), etc.
Improve the symptoms of cerebral ischemia.
Regular ultrasound examination to monitor the changes of the disease dynamically.
Surgical treatment The aim of surgical treatment of carotid stenosis is to prevent the occurrence of stroke and, to a lesser extent, to prevent and slow down the onset of TIA. The standard surgical procedure is carotid endarterectomy (CE).
Carotid endarterectomy was introduced in 1954, with some initial attempts showing poor results, but as the technique continued to improve, its complications became less frequent, and by the mid-1980s approximately 100,000 people were undergoing CE each year in the U.S. In the early 1990s, several large-scale, multicenter clinical trials were reported, objectively evaluating the effectiveness and safety of CE, of which The three most influential trials were the ECST, NASCET, and the Asymptomatic Carotid Atherosclerosis Study (ACAS). both ECST and NASCET were conducted in patients with symptomatic severe carotid stenosis, and the findings of both trials were consistent.
CE treatment was more effective than medical drug therapy for symptomatic carotid stenosis, with patients significantly benefiting from CE performed in carotid stenosis of 70% to 99%.
Patients with stenosis of 0% to 29% had a low likelihood of stroke within 3 years, and the risks of CE far outweighed the benefits and CE was contraindicated.
Patients with stenosis of 30% to 69% were tentatively considered inappropriate for CE, but further validation is needed. ACAS randomized groups of patients with asymptomatic carotid atherosclerosis to CE and drug therapy showed that the cumulative stroke and mortality rates for the two groups were 5.1% and 11.0%, respectively, for patients with carotid stenosis ≥60%, and that the effect of CE was much better than that of drug therapy. CE is generally considered feasible in asymptomatic carotid stenosis ≥60%, and some scholars believe that surgery can be performed when the stenosis is ≥80% due to the low incidence of cerebrovascular events in asymptomatic patients.
Complications of CE include perioperative stroke and death; and cerebral nerve injury, wound hematoma infection, postoperative hypertension, and postoperative hyperperfusion syndrome; the incidence of myocardial infarction and hypotension is low.
Interventional treatment
Carotid percutaneous transluminal angioplasty (PTA) is a relatively mature technique for revascularization, which is mainly performed by filling a balloon and squeezing the stenosed vessel from the inside out, causing fracture and damage to the vessel wall to achieve dilation. This technique has been widely used in various vascular diseases throughout the body, such as renal artery, iliac artery, coronary artery, etc. Compared with other vascular diseases, the application of PTA in carotid artery stenosis has progressed slowly because of technical reasons such as the complexity of the operation route of PTA, and the fear of complications such as vessel rupture and cerebral infarction caused by embolus dislodgement. Since the late 1980s, when carotid PTA was introduced into clinical practice, PTA is gradually becoming an alternative therapy to CE.
The main complication of PTA is postoperative restenosis, which has not been reported in the literature, but the incidence of restenosis is 5.0%-16.0%. PTA can be repeated after restenosis.
Although carotid stenting implantation PTA for stenosis has achieved some results, there are still problems with intraoperative intimal tears, postoperative vascular elastic retraction and restenosis due to
(a) For eccentric plaques, balloon support is only in the arterial wall contralateral to the eccentric plaque, so the filling balloon cannot tear the eccentric plaque, with the result that elastic retraction occurs in the dilated segment of the vessel after removal of the filling balloon.
high restenosis rate in balloon dilatation alone, which is caused by elastic retraction in early stages and further development of atherosclerosis in later stages.
In severe circumferential calcified plaques, dilation requires higher pressure and predisposes to the formation of arterial coarctation. In contrast, the implantation of a carotid stent can cover and tighten the vessel wall of the treated segment, close the entrapment caused by balloon dilation, and limit the contact between the artery and the material within the circulating blood that causes intimal hyperplasia, thus improving the efficacy and reducing the incidence of restenosis.
Indications for carotid stentingThe American College of Cardiology in 1998 proposed the following principles for the management of carotid stenosis, which can be used as a reference for carotid stenting.
Carotid artery stenosis (70% to 99%) with ipsilateral symptoms of stenosis, with indications for CE.
carotid stenosis (30% to 69%) with symptoms of cerebral ischemia ipsilateral to the stenosis, for which CE treatment may be considered but has not yet proven beneficial
For carotid stenosis (0% to 29%) with symptoms ipsilateral to the stenosis, CE treatment is not beneficial; ④ For asymptomatic carotid stenosis (60% to 99%), CE is beneficial.
Currently, the technical success rate of carotid artery stenting is greater than 98%, the complication rate is 2% to 6%, and the mortality rate is <1%, indicating that carotid artery stenting may be safe and effective in the treatment of carotid stenosis. However, the clinical efficacy of internal carotid artery stenting depends not only on the immediate efficacy and complication rate, but also on the long-term efficacy to determine the value of stenting in the treatment of carotid artery disease. Several multicenter, randomized, prospective, controlled clinical trials of carotid stenting versus CE for carotid artery stenosis are currently underway, and more definitive conclusions are expected soon.
Complications of carotid stenting: postoperative restenosis rate <5%; low incidence of stent deformation, collapse, and displacement; other complications such as vasospasm, stroke, and hematoma formation are similar to those of PTA. In addition, in recent years, in order to reduce the incidence of TIA and cerebral embolism caused by embolus dislodgement during carotid stenting and to improve the safety of the operation, intraoperative cerebral protection devices have been used in clinical practice. The device can prevent the debris dislodged from the vessel wall during the operation from entering the skull with the blood flow and reduce the incidence of intraoperative cerebral embolism, and its long-term efficacy needs further confirmation.
Comparison of PTA, carotid stenting, and CE The effectiveness of CE has been demonstrated in several large clinical trials, but it has some limitations.
The need for general anesthesia in some patients and the inability of many patients to tolerate the procedure
the procedure is only indicated for lesions limited to the extracranial segment of the carotid artery
The procedure has certain complications.
PTA and carotid stenting have the following advantages over CE: no general anesthesia is required, and some patients with severe co-morbidities can tolerate the procedure; the lesion may not be limited to the extracranial carotid artery; the procedure is less invasive and shorter; and the carotid, vertebral, and coronary arteries can be treated simultaneously.
PTA and carotid stenting also have some problems: although they improve stenosis, they do not eliminate potential sources of emboli; most reports of carotid PTA and stenting are small, follow-up is short, and long-term results need to be further validated in randomized, large-scale clinical trials.
In conclusion, each of the three treatment approaches has advantages and disadvantages and should be further investigated to enrich the treatment of carotid artery stenosis disease.