Carotid arteries laboratory studies
For the investigation of patients with auscultatory noise over the carotid artery, or a history of stroke and transient ischemic attack (TIA) in the carotid system, there are many diagnostic techniques. Reveal evidence of the damage of the common carotid artery bifurcation, and its nature can auscultatory detection of noise on the bifurcation of the common carotid artery in the neck or over the eyeball, and palpation of the arteries in the neck, on the surface of the face and forehead with compression of the artery prootic (dynamic palpation person).
High-sounding noises on auscultation, decaying during diastole, may point to stenosis (narrowing) the beginning of the internal carotid artery. Meanwhile, only certain clinical experience will allow the doctor to assess the duration and height of the noise or subtle variations in the voltage pulse palpation during a dynamic entity. For a more reliable determination of the expression and localization of atherosclerosis in the carotid artery thrombosis developed several noninvasive tests (without the introduction of a tool in the tissue the patient).
Carotid arteries non-invasive studies
Determine the pressure in the internal carotid artery can oftalmodinamometriya, okulopletizmografiya and directed supraorbital Doppler examination. These tests are especially efficacious in cases where the remainder of the lumen diameter at the site of his damage in the early atherosclerosis of internal carotid artery is more than 2 mm. This gives the normal levels during the study, and when the remaining lumen diameter is less than 1 mm, which makes blood pressure higher (distal) the affected area is sharply reduced.
Investigate the bifurcation of the common carotid artery allows non-invasive methods such as ultrasound and quantitative spectral fotoangiografiya.
Ultrasonic methods of investigation include the B-scan real-time frequency analysis and signal the return echoes from flowing blood. It should be remembered that ultrasonic visualization of vessels has limited resolving power, as calcification of plaque prevents penetration of the ultrasound signal, and the density of soft thrombus is approximately the same as current levels. However, with the help of this study can reliably identify lesions atherosclerotic vessel wall at the bifurcation of the common carotid artery.
The nature of arterial flow through the site of stenosis (narrowing of the lumen of the artery ) in lesions of atherosclerosis varies from laminar with constant speed on the current in the direction of flow obstacles at high speed and then on the turbulent current with wide fluctuations in flow velocity immediately distal to stenosis. These changes in blood flow can be detected by Doppler techniques such as continuous-wave (HB) or echo-pulse with a variable wavelength. They appear as a spectral expansion of the return echo pulses from the Doppler signal. Duplex scanning of neck vessels and the brain combines the study of blood in the echo and the analysis of arterial blood flow in each area studied by echo-pulsation with variable wavelength.
Quantitative spectral analysis of the available fonoangiografiya allows listening to the frequency- noise power components of the turbulent flow of blood in the bloodstream. With the help of calculated residual lumen diameter of the internal carotid artery and distinguish between noise arising in the carotid bifurcation, and the noise that spreads from the base of the heart. Meanwhile, a noise from the external carotid artery may be mistaken more serious noise from the internal carotid artery. This test is different in that it gives more accurate results if the noise comes from the constriction of the vessel (artery stenosis area) with the value of the remainder of the lumen diameter of 0.9-2.5 mm. Consequently, it is most advisable to apply for such values stenosis (narrowing of the lumen of blood vessels), when other noninvasive tests are less informative.
The clinical practice of patients with atherosclerosis and thrombosis, carotid artery in the basin showed that the optimal set of non-invasive methods should include a direct investigation of the bifurcation of the common carotid artery by duplex scanning in combination with spectral analysis of frequencies obtained with the Doppler signal. In identifying sound we recommend holding fonoangiografii. Oculopletizmografy used in most laboratories for the indirect measurement of pressure in the internal carotid artery and a more precise assessment of hemodynamic consequences of the damage of its lumen. These tests are most informative in the following clinical situations:
- Study the bifurcation of the common carotid artery in cases where an ischemic stroke or transient ischemic attack (TIA) of unknown origin developed in the internal carotid artery;
- Control over the progression of established stenosis (narrowing of the lumen), the carotid artery;
- Examination in the presence of disease-free sound.
Please note that all non-invasive vascular studies carotid or vertebral artery, characterized by a certain measurement error (10% in the hands of an experienced researcher). In addition, with their help, you can not differentiate carotid occlusion complete (occlusion of the lumen of the vessel) from a pronounced stenosis (narrowing) of the initial section of the internal carotid artery. Therefore, they are less informative in situations where a patient, who suffered a small stroke or transient ischemic attack (TIA), is an urgent need to conduct the appropriate treatment to prevent recurrent acute disorders of cerebral circulation. It is usually impossible to do without angiography.
Recently developed technique of pulse - echo studies with variable wavelength, which is used to determine blood flow in the vertebral arteries and intracranial arteries, the major, including the trunk of the middle cerebral artery, anterior and posterior cerebral arteries. The effectiveness of this method in documenting impairments of the blood flow in patients with lesions that lead to a narrowing of blood vessels, yet to be confirmed.
The most reliable method for studying the vascular network of the brain is cerebral angiography. The procedure carried out by selective angiography of the administration of contrast material after femoral artery catheterization. Selective angiography can detect ulcerative lesions of the arterial wall, expressed its narrowing (stenosis), clot burden formation in the wall of carotid bifurcation. The same selective angiography allows you to directly see stratification carotid wall and damage its siphon and other vessels (arteries), atherosclerosis, cerebral thrombosis. Using selective angiography can detect collateral blood flow in the circle of Willis and the cortical surface, embolic occlusion of branches of the brain.
By angiography is impossible to determine blood flow, but it captures some of the changes, evidence of its impairment in the internal carotid artery. For example, intracerebral arterial tree can be filled more slowly than the external carotid artery. Thus, cerebral angiography allows your doctor to evaluate the many factors relevant to understanding the nature of pathological physiology of stroke (cerebral infarction).
Considering the advantages of selective cerebral angiography should not forget about the dual risks of this procedure. According to available statistics, the incidence of complications during selective angiography ranges from 1.3 to 12%. Especially frequently discussed complications such as likelihood of the bundle of aortic wall and embolic stroke. Some authors believe that the diagnostic procedure of selective angiography is a special risk for patients with severe carotid bifurcation stenosing lesion, while others believe that in the hands of experienced angiografistov this study is relatively safe for all testimony to it. Moreover, large doses of contrast medium can provoke angina, congestive heart failure and renal failure.
Simple preventive measures in the form of dehydration (dehydration) and hypotension during and after selective angiography can prevent complications associated with cerebral ischemia. Patients with recurrent headaches or migraine history before selective angiography prescribe corticosteroids, but their efficacy in preventing ischemic complications has not been proved. In some cases, use a more secure method of angiography with the introduction of contrast medium into the brachial artery, providing as complete information as selective intracranial angiography with catheterization of the femoral.
Arterial administration of contrast agent used in angiography offers several advantages compared with the method of intravenous contrast, but is associated with the same risk as traditional angiography. Usually, the safest choice for the patient procedure carried out in accordance with the clinical experience gained in a particular institution, where the survey is conducted.
Imaging studies (CT, MRI)
Improvement of methods for the study of brain infarcts, their size and location due to the development of axial computed tomography (CT), positron emission tomography (PET) and nuclear magnetic resonance (MRI). The last two methods currently in use during angiography, with the only difference is that CT requires intravenous administration of contrast material, MRI and angiography of the injection of contrast into the patient's bloodstream is not required.
CT of the brain plus angiography with intravenous contrast to evaluate the size and location of infarcts of the brain, located supratentorial (above the snaring of the cerebellum), including lacunar infarcts with a diameter less than 0.5 cm In addition, CT of the brain reveals the perifocal edema (swelling around the area of stroke in the parenchyma of the brain) and with less regularity - a hemorrhagic stroke (heart attack). Meanwhile, in the early period of development of cerebral infarction during the CT scan can not distinguish brain tissue from ischemia of normal. In most cases, CT can not detect infarcts of the brain, at least in the first 48 hours of the disease. Less reliable results CT of the brain allows for localization in the brain stem infarction, ie, in vertebro-basilar circulatory system, in connection with the artifacts that occur when moving, and bone artifacts, as well as the small size of many foci of infarcts.
Measurement of cerebral blood flow with radioactive xenon and positron emission tomography (PET) using labeled carbon dioxide and oxygen provide a qualitative and quantitative determination of cerebral blood flow tomography. Application of these methods do not apply to routine clinical practice, and they are not used for the purpose of therapeutic monitoring. The method of proton MRI of the brain are used to uniquely identify the prevalence and location of infarct within the first hours after its development. With the introduction into clinical practice magnets vysokosilovymi fields (1.5-4 Tesla) imaging has become possible for patients of regional MRI spectrum of high-energy phosphate compounds, followed by the conclusion about the viability of brain tissue. This technology allows you to quickly assess the response of brain tissue to treatment.