Can the detachment of carotid artery plaques lead to cerebral infarction? What are the advantages of using ultrasound to examine carotid artery plaques?

Author: Guo Fajin, chief physician of Beijing Hospital

Reviewer: Shen Chenyang, Chief Physician, Beijing Tiantan Hospital, Capital Medical University

According to a survey study on chronic diseases in China, among adults, the incidence of carotid atherosclerotic plaques is about 6% in those aged 40-49 years old; the incidence of carotid atherosclerotic plaques in those aged 50-59 years old is about 21%; the incidence of carotid atherosclerotic plaques in those aged 60-69 years old may increase to 41%; and the incidence of carotid atherosclerotic plaques in those over 70 years old is as high as 61%.

There are about 2 million new cerebral infarction (stroke) patients in my country every year, and carotid atherosclerotic plaques are an important factor causing cerebral infarction, especially when vulnerable plaques in the carotid artery fall off, they can flow into the cerebral blood vessels with the blood flow, causing cerebral blood vessels to become blocked. Therefore, the shedding of carotid plaques is a very important cause of cerebral infarction.

Figure 1 Original copyright image, no permission to reprint

For some high-risk groups, such as smokers, people with high blood pressure, diabetes, high blood lipids, immune system inflammation or/and a family history, it is necessary to screen for carotid artery plaques as early as possible. Carotid artery ultrasound examination is the preferred method for screening carotid artery plaques.

1. What are the advantages of ultrasound examination of carotid artery plaques?

In the systemic arterial system, the carotid artery is relatively superficial and thick. Ultrasound examination of the carotid artery is convenient, fast and effective, especially color Doppler ultrasound, which is known as non-invasive angiography. It is currently the preferred method for examining carotid artery plaques and is easily accepted by clinicians and patients.

Compared with other imaging examinations, such as CT angiography (CTA), digital subtraction angiography (DSA), and magnetic resonance imaging (MRI), the first advantage of carotid artery ultrasound examination is that it does not cause radiation damage and is relatively inexpensive.

Second, ultrasound examination is real-time and can display the morphological structure and hemodynamics of blood vessels in real time.

Third, ultrasound can be examined repeatedly from multiple sections and can reflect lesions in multiple different parts of the body.

Fourth, ultrasound examination is non-invasive, convenient, easy to operate, can obtain examination results in a timely manner, and can be repeated many times in a short period of time. In addition, ultrasound equipment is relatively light and easy to move, and can be used for bedside examination of some critically ill patients.

2. What problems can carotid artery ultrasound examination detect?

Carotid artery ultrasound is mainly used to evaluate the location, range and severity of carotid artery lesions. The most common ones are to determine whether the carotid artery has atherosclerosis, whether there are plaques on the carotid artery wall, and the shape, structure and presence of new blood vessels of the plaques. In addition, it can also evaluate whether the plaques cause arterial stenosis and the degree of stenosis, and determine whether the artery is occluded.

How does carotid ultrasound determine whether there are plaques in the carotid artery? The current standard is: if the thickness of the carotid intima-media is greater than or equal to 1mm, it is defined as intima-media thickening, which means that carotid atherosclerosis has occurred; if the thickness of the intima-media is greater than or equal to 1.5mm, it can be judged as plaque.

Ultrasound can observe the surface morphology and internal echo of the plaque, such as whether the surface is smooth or irregular, that is, whether there is ulcer; whether the internal echo is low, equal, mixed, or strong. It can also understand whether there are new blood vessels in the plaque and how many new blood vessels there are.

3. How does ultrasound examination assess the stability of carotid artery plaques?

The stability of carotid plaque mainly depends on two factors, one is internal and the other is external.

The internal cause refers to the condition of the plaque itself, such as the location, size, morphology, surface characteristics and internal structure of the plaque, whether the plaque has new blood vessels and the number of new blood vessels. By combining the above factors, the stability and vulnerability of the plaque can be evaluated.

The plaque has a base, a lipid core and a fibrous cap. The thinner the fibrous cap, the larger the lipid core. Even if the fibrous cap is incomplete or ruptured, it is considered an unstable plaque that can easily fall off and cause cerebral infarction.

Figure 2 Original copyright image, no permission to reprint

If there are new blood vessels in the plaque, the new blood vessels are relatively fragile and can easily cause the plaque to rupture and fall off, forming emboli and leading to infarction.

External factors include hemodynamics. The carotid artery has a trunk and bifurcations. The common carotid artery is divided into the internal carotid artery and the external carotid artery. If there are plaques at the bifurcation of the common carotid artery, especially at the beginning of the internal carotid artery, the artery that supplies blood to the brain has plaques. In addition, at the bifurcation of the artery, factors such as the direction and speed of blood flow and the shear stress on the blood vessel wall can cause significant changes in hemodynamics. In addition, there are fluctuations in blood pressure; mental state, such as severe stimulation or strong reactions; external environment, such as excessive cold or heat, etc. All of the above conditions will cause significant changes in hemodynamics. If these changes cause plaque rupture and detachment, it will lead to cerebral infarction.