Ultrasound signs of diseases of peripheral arteries

Color duplex sonography in the diagnosis of diseases of peripheral arteries

Occlusion disease of peripheral arteries (OBPA)

Occlusion disease of peripheral arteries, caused by atherosclerosis, is the most common arterial disease of the extremities (95%). Colored duplex sonography can be used for screening patients with clinical suspicion of peripheral arterial occlusive disease and for monitoring after surgical treatment. About 10% of the population have disorders of peripheral circulation, 10% of them have arteries of the upper extremity, and 90% have lower extremities (35% - pelvis, 55% shin). Often there are lesions at several levels and a bilateral disease. The earliest ultrasound sign of clinically latent atherosclerosis is the thickening of the intima and media. Occlusive disease is also manifested by changes in the wall in B-mode (narrowing of the lumen, soft or hard plaques) and turbulence and changes in blood flow in color. The primary tools for the quantitative assessment of stenosis are spectral analysis and the determination of the ratio of peak systolic velocities.

Stages of chronic occlusive disease of peripheral arteries

• Stage I: stenosis or occlusion by the absence of clinical symptoms
• Stage II a: intermittent claudication, length of painless distance more than 200 m
• Stage II b: intermittent claudication, length of painless distance less than 200 m
• Stage III: pain at rest
• Stage IV a: ischemia with trophic disorders and necrosis
• Stage IV b: ischemia, gangrene

Lerish syndrome

A specific form of occlusive disease of peripheral arteries is Lerish syndrome, which is a chronic thrombosis of aortic bifurcation with a bilateral absence of pulsation on the femoral arteries. To compensate for occlusion, a wide collateral network develops, which is usually detected randomly in patients examined for intermittent claudication or erectile dysfunction. Note that a decrease in peripheral resistance leads to the appearance of biphasic waves in the lower epigastric artery, which serves as collateral.

True aneurysms, pseudoaneurysms, exfoliating aneurysms

The key aspects in the diagnosis of an aneurysm are the definition; prevalence of lesion, evaluation of perfused lumen (thrombi are potential sources of emiolia) and identification of vascular walling. True aneurysm is an extension of all layers of the vascular wall. It is more common in the popliteal artery and can be single or multiple.

False aneurysm or pseudoaneurysm often arises from the iatrogenic cause of artery puncture, in this case, in the distal segment of the external iliac artery. It can also develop in places of sutures after vascular surgeries. The main complications of pseudoaneurysms are ruptures and compression of nearby nerves. Aneurysmal formation contains a perivascular hematoma that communicates with the lumen of the vessel. With the help of color duplex sonography, uniform unilateral flow in the neck of the aneurysm is usually detected. As a type of treatment, a specialist can cause thrombosis of perfused hematoma by compression under the control of color duplex sonography. Contraindication is the presence of aneurysms along the umbilical ligament, aneurysms more than 7 cm in diameter and limb ischemia. Similar results can be obtained with vascular compression by pneumatic equipment (FempStop). The incidence of spontaneous thrombosis of pseudoaneurysms is about 30-58%.

Arteriovenous malformations (AVM)

AVMs can be congenital or acquired, for example, as a result of puncture (arteriovenous fistula) or vessel injury (0.7% cardiac catheterization). AVM is an abnormal connection between high-pressure arterial system and low-pressure venous system. This leads to characteristic disorders of blood flow and spectral changes in the arteries, both proximal and distal to the fistula, and also from its venous side. With a decrease in peripheral resistance due to the shunting of blood, the spectrum becomes biphasic proximal to the fistula and three-phase more detailed than it. Arterial inflow into the venous part causes turbulence and arterial pulsation, which can be visualized. Significant shunting potentially creates a risk of heart overload volume.

Syndromes of arterial compression

Arterial compression syndromes arise as a result of persistent or transient (for example, changes in body position) narrowing of neurovascular structures due to many reasons, which leads to a deficit of perfusion of the distal vascular bed. Compression of the vascular segment leads to intimal lesions, predisposing to stenosis, thrombosis and embolism. The main syndromes of arterial compression of the upper limb are syndromes of the entrance and exit openings of the thorax. The main manifestation on the lower limb is popliteal latching syndrome. The contraction of the calf muscles disrupts the connection between the popliteal artery and the middle head of the gastrocnemius muscle, which causes artery compression. This causes about 40 % of cases of intermittent claudication occurring before the age of 30 years. With the help of color duplex sonography, it is possible to determine the changes in blood flow during exercise and the anatomical interrelationships of blood vessels and muscles.

Control after overlap anastomosis

Color duplex sonography can evaluate the success of overlapping anastomosis and identify possible complications, such as repeated stenosis and occlusion of the bypass vessel at an early stage. It is necessary to evaluate the proximal and distal anastomoses of the vessel to detect blood flow disturbances. The peak blood flow velocity should be measured at three points. Echogenic walls of the vascular prosthesis or stent and acoustic shading caused by the stent material. It should not be mistakenly perceived as plaques or repeated stenosis.

The junction of the vessel with the stent and the lines of the anastomotic sutures are zones. Predisposed to repeated stenosis.

If the spectrum reveals a low amplitude, pronounced pulsation and a sharp component of the reverse blood flow, it is very likely that there is an occlusion. The occlusion of the common femoral artery is manifested by the breakage of the color blood flow and the absence of spectral signals from it just before the bypass anastomosis.

Control after percutaneous angioplasty

Follow-up examination after successful percutaneous transluminal angioplasty shows a significant increase in peak systolic velocity with normal late diastolic blood flow. The filling of the spectral window results from the fact that the examination was performed shortly after the operation, and the time had not elapsed enough to smooth out the intima, which led to the persistence of turbulent blood flow.

Criteria for stenosis of bypass anastomosis

• Peak systolic velocity <45 cm / s
• Peak systolic velocity> 250 cm / s
• Changes in the ratio of peak systolic velocities more than 2.5 (the most reliable parameter for stenosis> 50%)

Causes of repeated stenosis

• Acute thrombosis
• Vascular dissection after angioplasty due to intima-median ruptures
• Insufficiently extended stent
• Unevenness of the connection of the bypass vessel or stent with the main
• Myointimal hyperplasia
• Progression of the underlying disease
• Infection

Evaluation of fistulas for hemodialysis

To assess arterio-venous fistulas for hemodialysis access, high-frequency linear sensors (7.5 MHz) are used. Due to the difficulty of correlating the data of color duplex sonography with anatomical structures, the study should be performed together with a doctor performing dialysis or a surgeon. Do not recommend the following protocol:

1. When examining the delivery artery, always begin the study from the brachial artery, which is usually visualized in the cross section. The spectrum should show an even picture of low resistance with a clear diastolic blood flow. If this does not happen, it should be suspected that the blood does not have free access to the fistula, and the blood flow is reduced by stenosis
2. In the arterial artery, several duplex volumes should be obtained (at least three, and preferably six). This is best done on the brachial artery a few centimeters above the elbow joint. These measurements are necessary for both monitoring and general evaluation. Blood flow volume less than 300 ml / min with Cimino fistula or less than 550 ml / min with Gore-Teh catheter indicates insufficiency. Accordingly, the lower values for "normal" fistulas are 600 and 800 ml / min
3. The artery is examined on its way for signs of stenosis (increased blood flow and turbulence). There are no speed limits that can confirm stenosis. Stenosis is determined by measuring the decrease in the cross-sectional area of the vessel relative to normal prestenotic and post-stenotic segments in the B-mode. This also applies to stenosis of the venous fistula. The vein should be examined by a "floating" sensor with very light pressure, since any compression causes significant artifacts. The access vein is examined, like the central veins, for stenosis, aneurysm, perivascular hematoma, or partial thrombosis. As with digital subtraction angiography, the quantitative evaluation of stenosis is hindered by the lack of data on the normal state of the width of the access lumen. Usually stenosis is located in the following areas:
   • area of anastomosis between artery and draining vein
   • area from which access normally takes place
   • central veins (for example, after placing a central venous catheter into the subclavian or internal jugular vein)
   • with Gore-Tex fistula: distal anastomosis between the fistula and the draining vein.

Critical Assessment

The clinical significance of non-invasive methods of color duplex sonography and MRA increased due to the absence of ionizing radiation, especially in frequent control studies, and due to their advantages in patients with allergies to contrast agents, renal insufficiency or thyroid adenomas.

While digital subtraction angiography is an invasive method used only for topographic mapping, color duplex sonography can provide additional diagnostic information about stenosing lesions, functional parameters and the response of surrounding tissues. It can also detect clots in aneurysms. In the hands of an experienced specialist, color duplex sonography is a high-quality, non-invasive technique for studying peripheral vessels.

The disadvantages of color duplex sonography, such as limited visualization of vessels located at depths or hidden by calcifications, have significantly decreased. This happened with the introduction of ultrasound contrast agents.

The SieScape panoramic visualization technique in combination with energy Doppler ultrasound significantly improves documentation of pathological changes affecting the long segment of the vessel. The combination of these techniques can give a topographic image of vascular changes up to 60 cm in length.

Color duplex sonography often plays a limited role in the study of vessels of the lower limb, especially of small caliber, with multiple plaques and slow blood flow due to multilevel lesions. Digital subtraction angiography in such cases remains the method of choice in the diagnosis of arterial diseases below the knee joint.

In addition to color duplex sonography, an alternative to digital subtraction angiography is MRI with contrast enhancement of gadolinium-containing drugs and a phase-contrast MRA of peripheral vessels. CT angiography does not play a big role in the examination of peripheral vessels due to artifacts due to calcified plaques, the need for high doses of contrast agents with intravenous administration and high radiation exposure with prolonged examination. It is better to use it to detect aneurysms in the central vessels.

Evaluation of fistulas for hemodialysis

Color duplex sonography surpasses angiography in many aspects. Due to the possibility of measuring the volume of blood flow, color duplex sonography can reveal an etiological cause, for example, narrowing of the lumen due to compression by hematoma. Colorful duplex sonography also makes it possible to carry out control studies. When the amount of blood flow is known, it is easier to evaluate the significance of stenosis than angiography. Therefore, observation and waiting tactics can be used for moderate to high stenosis if the blood flow in the fistula is assessed as satisfactory.

Initial prospective and randomized studies have shown that regular CDS studies with 6-month intervals with a prophylactic expansion of stenosis in excess of 50% significantly prolong the availability of hemodialysis access and reduce the cost