Cardiovascular diseases are the leading cause of mortality both worldwide and in Russia. Each year, more people die from cardiovascular diseases than from any other illness. According to the World Health Organization, 17.5 million people die annually from cardiovascular diseases. There is an annual increase in mortality from this pathology, and by 2030, it is projected to increase by approximately 1.5 times, potentially reaching around 25 million people.

Today, the main cause of heart and vascular damage is atherosclerosis – a condition where the blood vessels supplying vital organs become partially or completely blocked by atherosclerotic plaques. When the coronary vessels of the heart are affected, angina (chest pain) or more severe consequences such as myocardial infarction (death or necrosis of part of the heart muscle), circulatory failure (acute or chronic heart failure) can develop. This ultimately leads to a significant reduction in exercise tolerance, prolonged hospitalizations, disability, and death.

Atherosclerosis of the cerebral vessels also leads to severe consequences: premature decline of brain functions and the development of acute cerebrovascular accidents (stroke), where, as in myocardial infarction, necrosis of a part of the brain occurs. The development of a stroke can result in various neurological disorders – motor, sensory, speech, cognitive, which can lead to complete social withdrawal, disability, and death.

Equally life-threatening is atherosclerotic damage to the vessels supplying blood to another important organ – the kidneys. The kidneys are a multifunctional organ responsible not only for the excretion of waste from the human body but also for maintaining other vital functions, such as blood pressure regulation and maintaining optimal water-salt balance. The clinical consequences of atherosclerosis in the renal arteries (narrowing or complete closure of the vessel) are diverse. Impairment of the excretory function of the kidneys leads to the development of so-called primary contracted kidney and the progression of renal failure. Narrowing of the renal arteries inevitably leads to the release of stress substances into the bloodstream (activation of the sympathetic-adrenal and renin-angiotensin systems, etc.), resulting in a significant increase in blood pressure. Hypertension caused by atherosclerotic narrowing of the renal arteries has a malignant course, is poorly responsive to medication, and is accompanied by a significant frequency of complications – hemorrhagic stroke (bleeding in the brain), development of chronic heart failure, vision impairment, and more.

Another common manifestation of atherosclerosis is the damage to the arteries of the lower extremities. Narrowing (stenosis) or complete closure (occlusion) of the major blood vessels supplying the lower extremities by an atherosclerotic plaque clinically manifests as so-called "intermittent claudication" or Leriche syndrome. Initially, such localization of atherosclerosis may slightly limit the patient's physical activity, which is why these symptoms may not receive due attention from either doctors or the patients themselves. However, the presence of an atherosclerotic plaque in the vessel itself poses the danger of a thrombus forming on its surface. Thrombus formation is an extremely unfavorable complication of atherosclerosis, which suddenly blocks blood flow, leading to severe pain and gangrene (necrosis or death) of the muscle tissues of the lower extremities. In this case, the only life-saving intervention remains the amputation of the lower limb, inevitably resulting in disability and loss of work capacity, as well as physical inactivity and significant stress impact on the human body, which collectively contributes to the further progression of atherosclerosis. Thus, the widespread prevalence of this disease and its severe clinical consequences require modern medicine to closely study the mechanisms of its development, as well as the prevention and treatment of atherosclerosis.

Atherosclerosis belongs to the category of pathologies whose development is caused by both hereditary and social factors (stress, environmental conditions, improper nutrition, smoking, physical inactivity, etc.). It is a widely accepted axiom that quitting smoking and foods rich in cholesterol and carbohydrates significantly reduces the likelihood of atherosclerosis progression in any location, including the most adverse forms (coronary atherosclerosis, atherosclerosis of the cerebral vessels). The risk of developing atherosclerosis can be reduced with medications – statins, which lower blood cholesterol levels. The negative impact of physical inactivity and the absence of regular physical exercise is well studied. According to a report by WHO experts in 2014, smoking increases the risk of developing atherosclerosis and coronary artery disease by 5 times, and physical inactivity by 3.5 times.

Thus, various preventive measures (both medicinal and non-medicinal) can reduce the likelihood of developing atherosclerosis. However, when the disease has already formed and atherosclerotic plaques have narrowed the lumen of the vessels, medicinal remedies become ineffective. Mechanical restoration of blood flow to the affected organ and finding the most effective method for this has been a priority in medicine for the last 50-60 years.

Approximately as many years are counted in the history of modern medicine's fight against the most unfavorable consequences of atherosclerosis – damage to the arteries of vital organs.

A modern cardiovascular clinic must have the necessary arsenal of technical means and trained personnel to provide qualified assistance to a patient with atherosclerosis. Restoring normal artery patency is currently the main pathogenetic method for treating ischemic heart disease (coronary artery disease), ischemic brain disease (carotid artery disease), and renal and lower limb artery disease. Mechanical restoration of blood flow is the method that effectively improves the patient's quality of life and long-term disease prognosis (long-term survival).

Initially, surgical treatment became widespread in cardiovascular clinics. The first bypass surgery in humans (where vessels are routed around the affected section of the artery) was performed in the 1950s. Various types of coronary artery bypass grafting (CABG), differing in the type of autografts (arteries, veins), the principle of forming anastomoses, etc., are used to this day. When using the patient's own venous system (usually the veins of the lower extremities), the operation is called coronary artery bypass grafting (CABG); when using the patient's own arterial system (internal mammary artery, radial artery), the operation is called mammary coronary artery bypass grafting. Such operations are performed quite frequently both in international practice and in various cardio centers in our country. Although the volume of such operations has significantly decreased due to the development of high technologies, a significant number are still performed in our country. For example, the leading cardiology center in Russia – the National Medical Research Center for Cardiology (formerly the Russian Cardiology Research and Production Complex) performs an average of about 200 open-heart operations annually. In the case of cerebral artery disease, a procedure called endarterectomy is performed, where the atherosclerotic plaque is removed directly from the vessel (temporarily clamped to stop blood flow) through a skin incision in the neck area. For lower limb artery disease (intermittent claudication, Leriche syndrome), various types of autografts (mainly veins from other vascular pools) and synthetic material prostheses (e.g., for atherosclerotic iliac artery disease) are used. What unites these interventions? In most cases, they allow restoring blood flow to the affected organ (bypassing the affected section in the case of bypass operations for ischemic heart disease or lower limb artery atherosclerosis, or directly surgically removing the plaque from the vessel lumen in carotid artery atherosclerosis – surgical endarterectomy). What are the disadvantages of such interventions? The techniques and tactics of such interventions have not undergone radical changes since their first performance. For bypass and similar operations, general anesthesia and mechanical ventilation are used, for heart surgery – a sternum incision and temporary circulation stop (auxiliary or artificial circulation). General anesthesia and mechanical ventilation are often challenging in elderly patients, especially with chronic lung diseases (asthma, chronic obstructive pulmonary disease, chronic pulmonary thromboembolism, etc.), as well as in patients with chronic brain diseases. In this case, using mechanical ventilation and artificial circulation is fraught with postoperative complications in the affected organs, significantly prolonging the patient's hospital stay, delaying recovery of work capacity, and in some cases leading to complete disability. Even with a normal and standard CABG operation, full recovery and healing of the sternum incision can take 3 to 6 months. Some surgical interventions are technically very complex due to anatomical features and are associated with a high risk of blood loss, such as surgery on renal and iliac arteries in the retroperitoneal space and subclavian artery surgery for their atherosclerotic disease.

As mentioned earlier, restoring normal blood flow to the affected organ is currently the logical final link in most cases of treating a patient with atherosclerotic plaques in various vascular pools. This pathogenetic nature of treatment (addressing the disease cause, not its symptoms) determines the main advantage of invasive interventions over conservative medication therapy – the ability to more effectively restore work capacity, improve the patient's quality of life, and long-term survival.

The 21st century is a time of high technology, and its development has not bypassed modern medicine. Alongside surgical methods, endovascular revascularization methods (angioplasty and stenting) are actively used in treating atherosclerosis. The term "endovascular" means delivering the necessary instruments to the affected site through the vessel via peripheral artery puncture (femoral in the lower limb or radial in the upper limb). This method does not require a surgical incision, general anesthesia with mechanical ventilation, or artificial circulation. Accordingly, the entire procedure is performed under local anesthesia. The trauma of the intervention is radically reduced, which in turn significantly reduces the patient's hospital stay.

Currently, endovascular methods of treating atherosclerosis are not inferior in clinical effectiveness to surgical treatment methods and surpass them in socio-economic effectiveness. Moreover, in treating acute forms of atherosclerotic disease (when thrombosis occurs on the atherosclerotic plaque), endovascular methods significantly outperform surgical interventions in clinical effectiveness and clinical outcomes due to their minimal invasiveness, rapid deployment, and use of advanced high technologies.

The progenitor of this direction is rightly considered balloon angioplasty, first performed in the 1970s. The method of balloon angioplasty involved expanding the narrowed section inside the artery by inflating a balloon. Despite the fact that the narrowing often returned to its previous state after such exposure, the method proved that atherosclerotic plaque could be influenced from inside the vessel without the risk of serious complications. The appearance of coronary stents in clinical practice was, without exaggeration, a revolutionary breakthrough in endovascular technology. The widespread use of stents has significantly reduced the frequency of acute complications after angioplasty and provided reliable control over the immediate results of the procedure. An important milestone in the development of endovascular technology was the appearance of drug-coated stents. The concept of local drug delivery is one of the most promising areas of modern medicine. Thus, the widespread introduction of next-generation stents into clinical practice has radically improved long-term treatment outcomes and significantly increased the total number of endovascular procedures.

Thus, endovascular methods of myocardial revascularization, due to their minimal invasiveness and advanced technology, have become widely used in modern cardiology clinics, and as they are technically refined and experience accumulates, they have taken a leading position in treating ischemic heart disease and atherosclerosis of various localizations.

As already mentioned, the concept of local targeted drug delivery using various carriers is one of the most promising directions in endovascular treatment. Thanks to the appearance of drug-coated coronary stents, endovascular technologies have taken a leading position in treating ischemic heart disease. The drug coating on the stent surface has antiproliferative properties (i.e., prevents scar tissue growth in response to the implantation of a foreign body). The widespread introduction of drug-coated stents into clinical practice has radically improved treatment outcomes and allowed this high-tech intervention method to be used in patients with various, including complicated anatomical and morphological forms of atherosclerosis.

Chronic Occlusions of the Coronary Arteries

One of the most challenging categories of patients for endovascular interventions are those with chronic occlusions of the coronary arteries. A chronic occlusion of a coronary artery represents a complete blockage (closure) of the coronary artery with no lumen. In chronic occlusion, there is a slow growth of an atherosclerotic plaque followed by complete obstruction of the coronary artery lumen. This triggers a compensatory mechanism for the development of collaterals from adjacent vascular pools. The formation of collateral blood flow ensures the preservation of a certain volume of viable myocardium. Nevertheless, this myocardium is at risk of developing a large myocardial infarction, and the presence of chronic occlusion of the coronary artery is associated with the development of adverse coronary events, despite the presence of a pronounced collateral network and the absence of scar (post-infarction or post-necrotic) lesions of the myocardium.

In the 1990s, the "open artery hypothesis" was formulated, according to which an attempt to recanalize (open the vessel and place a stent) a chronic occlusion should be made in all cases regardless of the occlusion's duration to improve the long-term prognosis of patients. In patients with scarred myocardium after an infarction and recanalization of the affected vessel, the difference in survival rates is most significant compared to patients without recanalization. Many international and domestic studies have proven that interventions performed as early as possible after an infarction have a high probability of technical success and better long-term effectiveness. Delayed interventions are generally associated with greater technical difficulties and have lower chances of immediate success. Currently, performing invasive coronary angiography in patients with a history of myocardial infarction is mandatory regardless of the presence of angina symptoms.

Thanks to the rapid development of endovascular technologies and the sharp increase in the number of therapeutic invasive procedures, significant clinical experience in the field of chronic occlusion recanalization has been accumulated. Today, there is a variety of endovascular technical approaches for opening chronic occlusions (antegrade, retrograde through collaterals, etc.), mastered by leading specialists in endovascular treatment. As a result, the technical success rate for opening occlusions reaches nearly 100% (unlike the experience from 10 years ago, when the technical success rate was on average 60-70%).

Stenting of Bifurcation Lesions of the Coronary Arteries

Bifurcation lesions are one of the most challenging categories for endovascular treatment, requiring certain practical experience and mastery of advanced technologies. In this type of lesion, it is necessary to restore the lumen of both the main vessel and the side branch and maintain this effect in the long term. In the long term after the intervention, there is a risk of restenosis formation in the main vessel and at the ostium of the side branch, which naturally increases the risk of recurrent ischemic heart disease (IHD) symptoms.

When using bare-metal stents, the invasive cardiologist was limited in the choice of bifurcation stenting strategy because the additional metal load in the intervention area when using more than one endoprosthesis was a risk factor for restenosis formation. The experience of using bare-metal stents in the treatment of bifurcation lesions indicates a high rate of restenosis in the long term – from 25 to 45%.

The introduction of drug-eluting stents into clinical practice changed the strategy for interventions in this type of atherosclerotic lesion. The use of two or more drug-eluting endoprostheses within the affected segment for stenting the main vessel and the side branch has become widely adopted in angiographic laboratories. Nevertheless, achieving an optimal immediate result and ensuring its preservation in the long term depends on adhering to the intervention technology, which has its peculiarities in various lesion scenarios. It should be noted that in all lesion scenarios, an essential condition for performing a safe intervention is the protection of the side branch with a guidewire. In the vast majority of cases, this technique allows avoiding acute occlusion of the side vessel and the development of focal myocardial changes. To achieve an optimal result and complete restoration of the lumens of the main and side vessels, various bifurcation stenting techniques have been developed and tested worldwide. The variety of bifurcation techniques can be divided into two main categories: implantation of a stent in the main vessel with balloon dilation of the side branch, and implantation of two stents in various modifications (T-stenting, V-stenting, Crush-stenting).

In modern approaches to treating bifurcation lesions with covered endoprostheses, there is a trend towards using a single stent for implantation in the main coronary vessel with balloon dilation of the side branch. This trend, currently supported by most leading specialists, is explained by accumulated long-term observations, which indicate that the patency of the side branch in the long term and the frequency of its restenosis are the same when using either one stent in the main vessel or the complex bifurcation constructions mentioned earlier. According to the latest scientific data endorsed at European and American scientific symposia, the use of more than one stent for stenting both the main vessel and the side branch is justified in the case of an unsatisfactory immediate result of side branch balloon dilation or the threat of its acute occlusion. Table 1 presents the results of major studies examining the long-term outcomes of the two main intervention strategies for bifurcation lesions – implantation of one stent and implantation of two stents.

As seen from the data presented, the implantation of an additional stent in the side branch does not improve long-term treatment effectiveness. On the contrary, in the study by Colombo et al, a significant increase in side branch restenosis was noted in the group with the implantation of two stents. In the study by Pan et al, the use of two stents was accompanied by an increase in restenosis rates in both the side and main vessels. Nevertheless, in the latest large randomized study by Steigen (n = 413), the long-term outcomes of different treatment strategies for bifurcation stenoses were almost indistinguishable from each other. These results support the routine use of a single stent in interventions for bifurcation lesions. This method is technically less complex and more economical in terms of cost and radiation exposure compared to the two-stent method. As mentioned earlier, it is currently widely accepted that the implantation of two stents is justified only in the presence of specific indications. Typically, such indications include a high probability of acute occlusion or the development of hemodynamically significant stenosis at the branch ostium. It should be noted that stenting the branch ostium is justified only with a sufficiently large vessel diameter (usually more than 2 mm).

When using two stents to treat bifurcation lesions, it is essential to strictly follow established and approved global standards, as ignoring these standards can nullify the effectiveness of an expensive and technically complex intervention. In the case of stenting the main vessel and the side branch, it is mandatory to complete the procedure with simultaneous dilation of both vessels (kissing balloons), which allows forming a bifurcation segment with the correct geometry. Failure to comply with this requirement leads to incomplete stent expansion and, consequently, an increased risk of restenosis. The increase in restenosis frequency in the absence of final kissing dilation has been noted with both crush stenting and T-stenting. The highest restenosis rate of the side branch (40%) was observed with crush stenting without post-dilation, emphasizing the necessity of completing the procedure with kissing dilation in this case. It is essential to reiterate that initial protection of the side branch with a guidewire is mandatory in all cases, as this preventive measure always ensures the patency of the side vessel and allows changing the intervention strategy if closure is threatened. Table 2 presents the comparative results of different bifurcation stenting techniques (with and without final kissing dilation) in studies involving the implantation of two stents.

The obtained results indicate the necessity of completing the procedure with kissing balloon post-dilation in bifurcation constructs using two stents, as the absence of this final stage leads to a significant increase in the risk of restenosis in both the main vessel and the side branch. The application of this technique, as mentioned earlier, contributes to the formation of the correct geometry of the implanted stents, the tight adhesion of the stent struts to the walls of the main and side vessels, and the even distribution of the drug. All these factors together are essential conditions necessary for the prevention of restenosis at the stent implantation site. Failure to comply with any of these conditions leads to an increased risk of restenosis with this type of intervention.

Step 1
Place a guidewire in the main vessel, then place a second guidewire in the side branch. If necessary, pre-dilate the main vessel and side branch (Diagram 1a, Figure 1a).

Step 2
Implant the stent in the main vessel. The guidewire in the side branch remains under the implanted stent (jailed) (Diagram 1b, Figure 1b).

Step 3
If the patency of the side branch ostium worsens, the guidewire is advanced from under the stent into the main vessel, and the guidewire from the main vessel is passed through the stent cell into the side branch (Diagram 1c, Figure 1c).

Step 4
Dilate the side branch ostium with a balloon through the stent cell (Diagram 1d, Figure 1d and Figure 1e).

Advantages:
Relative technical simplicity, savings on consumables and intervention time, the ability to use a 6 Fr guide catheter.

Disadvantages:
Possible difficulties in placing the guidewire in the side branch after stent implantation and passing the balloon through the stent cell, the need to use stent designs with a wide side cell.

Step 1
Place a guidewire in the main vessel, then place a second guidewire in the side branch. If necessary, pre-dilate the main vessel and side branch (Diagram 2a).

Step 2
Implant the stent in the side branch, positioning the proximal end of the stent strictly at the ostium of the branch.

Step 3
Remove the guidewire and balloon from the side branch (Diagram 2b).

Step 4
Implant the stent in the main vessel (Diagram 2c).

Advantages:
No need for secondary placement of the guidewire in the side branch through the stent cell, the possibility of using a 6 Fr guide catheter due to the sequential stent implantation.

Disadvantages:
Limited application of the technique only when the side branch departs at a 90° angle, as in other cases, the proximal end of the stent may prolapse from the side branch into the main vessel, causing difficulties in passing the stent into the main artery; the need for precise positioning of the stent at the ostium of the side branch, as distal placement may result in an uncovered segment at the ostium of the daughter vessel.

Step 1
Place a guidewire in the main vessel, then place a second guidewire in the side branch. If necessary, pre-dilate the main vessel and side branch (Diagram 3a, Figure 3a).

Step 2
Simultaneous implantation of stents in the side branch and the main vessel, creating an artificial bifurcation (Diagram 3b, Figures 3b and 3c).

Advantages:
No need for secondary placement of the guidewire in the side branch through the stent cell, and the proximal ends of the stents are positioned in the main vessel.

Disadvantages:
The technique can only be applied if there is no lesion in the main vessel above the bifurcation and its diameter is more than 3 mm. It requires the use of a guide catheter of at least 7 Fr. V-stenting is not recommended if the branch departs at an angle greater than 45º due to the pronounced bend of the stent at the ostium of the side branch.

Step 1
Place a guidewire in the main vessel, then place a second guidewire in the side branch. If necessary, pre-dilate the main vessel and side branch (Diagram 4a, Figure 4a).

Step 2
Position the stent in the side branch so that the proximal end of the stent is in the main vessel.

Step 3
Position the stent in the main vessel so that the proximal end of the stent in the main vessel is above the proximal end of the stent in the side branch (Diagram 4b, Figure 4b).

Step 4
Implant the stent in the side branch. Remove the guidewire and balloon from the side branch (Diagram 4c, Figure 4c).

Step 5
Implant the stent in the main vessel, pressing the protruding edge of the side branch stent against the vessel wall (Diagram 4d, Figures 4d, 4e).

Step 6
If necessary, place the guidewire in the side branch and perform post-dilation of the branch ostium.

Advantages:
The ability to use crush stenting in cases where V-stenting is not feasible.

Disadvantages:
Possible difficulties in placing the guidewire in the side branch for post-dilation of the side branch ostium, the need for a guide catheter of 7 Fr or more.

Step 1
Place a guidewire in the main vessel, then place a second guidewire in the side branch. If necessary, pre-dilate the main vessel and side branch.

Step 2
Position the stent in the main vessel so that the proximal end of the stent is slightly above the bifurcation.

Step 3
Position the stent in the side branch so that the distal end of the stent is in the side branch and the proximal end is above the proximal end of the stent in the main vessel (Diagram 5a).

Step 4
Implant the stent in the main vessel. Remove the guidewire and balloon from the main vessel (Diagram 5b).

Step 5
Implant the stent in the side branch, pressing the protruding edge of the main vessel stent against the vessel wall (Diagram 5c).

Step 6
If necessary, place the guidewire in the main vessel and perform post-dilation of the ostium.

Advantages:
The ability to use internal crush stenting in cases where V-stenting is not feasible; the ability to use the technique when the side branch has high functional significance; in cases where secondary catheterization of the side branch is problematic (branch departure angle greater than 45º). The main advantage is the ability to use the technique when it is necessary to cover an extensive affected area of the main vessel (most of the stent in the main vessel is implanted below the bifurcation, most of the stent from the side branch is in the proximal segment above the bifurcation).

Disadvantages:
Possible difficulties in placing the guidewire in the main vessel for post-dilation, the need for a guide catheter of 7 Fr or more.

Step 1
Place a guidewire in the main vessel; if necessary, pre-dilate the main vessel.

Step 2
Implant the stent in the main vessel (Diagram 6a).

Step 3
If the condition of the ostium worsens, place a guidewire in the side branch, and lower the balloon from the stent in the main vessel along the guidewire below the bifurcation (Diagram 6b).

Step 4
Perform pre-dilation of the branch ostium to facilitate stent passage through the cell of the previously implanted endoprosthesis, then position the stent in the side branch so that the proximal end of the stent is in the main vessel.

Step 5
Position the remaining balloon in the main vessel so that the proximal end of the balloon is above the proximal end of the stent in the side branch (Diagram 6c).

Step 6
Implant the stent in the side branch (Diagram 6d), remove the guidewire and balloon from the side branch (Diagram 6e).

Step 7
Dilate the balloon in the main vessel, pressing the protruding proximal end of the side branch stent against the vessel wall (Diagram 6f).

Step 8
If necessary, place the guidewire in the side branch and perform post-dilation of the ostium.

Advantages:
The ability to change the strategy and course of the operation – if the ostium of the side branch is normal, a single stent may suffice; if stenosis increases, stenting the branch can be performed.
The ability to use a 6 Fr guide catheter due to the sequential stent implantation makes the technique applicable for radial access.

Disadvantages:
Possible difficulties in placing the guidewire in the side branch and passing the stent through the cell of the previously placed stent, relative technical complexity of the method, longer procedure time, greater amount of consumables, and contrast agent required.

If the branch diameter is greater than 2 mm, and there is a threat of acute occlusion or the development of hemodynamically significant ostial lesions, one of the bifurcation stenting methods (implantation of two stents) is recommended, depending on the morphological features of the lesion and coronary anatomy.

Place guidewires in the main and side branches. If necessary, pre-dilate the side branch and main vessel.

Branch departure angle less than 45° - V-stenting (if there is an unaffected segment of the main vessel above the bifurcation and the main vessel diameter is more than 3 mm). If V-stenting is not feasible, use crush stenting.

Branch departure angle greater than 45° - crush stenting. If there is an extensive affected area of the main vessel proximal and distal to the bifurcation, as well as high functional significance of the side branch, reverse crush stenting is preferable.

Branch departure angle of 90° - T-stenting.

When using a 6 Fr catheter (radial access) – sequential stent implantation using the internal crush stenting method.

When discussing the achievements of endovascular treatment in recent years, it is impossible to ignore the application of endovascular methods for the treatment of left main coronary artery (LMCA) lesions. This area can be considered the last bastion of cardiovascular surgery that has fallen under the onslaught of invasive cardiology and endovascular methods for treating ischemic heart disease. It is well-known and scientifically proven that the condition of the left main coronary artery, along with the contractile function of the left ventricle, are the main factors determining the survival rate in patients with ischemic heart disease. Therefore, the effectiveness of interventions on the LMCA affects not only the degree of relief from angina symptoms but also significantly influences the long-term prognosis.

The necessity of complete myocardial revascularization (restoring blood flow in narrowed or occluded coronary arteries) in LMCA lesions is now unquestioned. Modern scientific literature has demonstrated a significant increase in life expectancy after revascularization in patients with LMCA lesions compared to medical therapy. Before the advent of drug-eluting stents, endovascular interventions on the LMCA were not widely performed due to unfavorable immediate and long-term treatment outcomes. The expansion of indications for endovascular treatment following the introduction of drug-eluting stents has led to endovascular interventions on the LMCA becoming routine procedures. Undoubtedly, the main success of the widespread introduction of drug-eluting stents for LMCA lesions was the reduction in the frequency of restenosis (re-narrowing) in the long term. With bare-metal stents, stenting the LMCA was associated with the highest incidence of restenosis compared to other locations of coronary atherosclerosis. The use of drug-eluting technology significantly reduced this rate and, consequently, greatly improved long-term clinical outcomes. The reduction in the frequency of adverse clinical events led to an improvement in an important clinical indicator – long-term patient survival. Here, it is necessary to note the main achievement of modern endovascular technologies, as traditionally, endovascular treatment was considered a method that alleviated symptoms of ischemic heart disease but did not affect the long-term prognosis.

An essential aspect is developing an optimal technical strategy for stenting LMCA lesions. The vast majority of atherosclerotic LMCA lesions are located in the terminal segment and usually extend to the ostium of one or both main coronary vessels (left anterior descending artery or circumflex artery). It should be noted that when treating such lesions with drug-eluting stents, it is advisable to consider the rules and recent scientific data on interventions at coronary bifurcations.

As with all bifurcation interventions, an essential condition for safe intervention on the LMCA is the protection of both vessels (LAD and LCx) with guidewires. In the vast majority of cases, this technique allows avoiding acute vessel occlusion and changing the intervention strategy if complications develop. The initial experience of using covered stents for LMCA lesions was replete with various two-stent constructs described in the section on bifurcation treatment. The large diameter of the vessels technically allowed extensive use of different bifurcation stenting modifications (T-stenting, V-stenting, Crush-stenting).

Subsequent experience has led to more restrained use of two endoprostheses in LMCA treatment and a revision of the stenting strategy for this type of coronary atherosclerosis. Firstly, the presence of two-stent constructs, especially after V-stenting, significantly complicates and sometimes makes repeat endovascular intervention impossible in case of restenosis formation. With V-stenting in the LMCA, two artificial lumens are formed from the implanted endoprostheses (two-barrels). As repeat endovascular procedures have shown, maintaining normal stent patency with secondary intervention is practically impossible in such constructs. In this case, the only technical option may often be converting the existing construct to crush stenting.

Secondly, using two endoprostheses for LMCA lesions increases the risk of restenosis. The frequency of restenosis with two stents in the LMCA is higher than the same indicator for two stents in other bifurcations. Undoubtedly, the clinical significance of restenosis development in the LMCA is much higher compared to other coronary atherosclerosis locations.

Thirdly, failing to perform final "kissing" dilation when implanting two stents in the LMCA significantly increases the risk of late thrombosis, which can have catastrophic consequences.

Recent studies have shown certain advantages of the single-stent implantation strategy for LMCA lesions. Single-stent implantation was accompanied by restenosis development in 5% of cases, while two-stent implantation saw a 24% restenosis rate. Single drug-eluting stent implantation resulted in 100% event-free survival after one year, compared to 86% in the two-stent group.

In our view, using a second stent for LMCA bifurcation reconstruction should align with modern principles of bifurcation endovascular interventions. Generally, two-stent implantation is justified with a high probability of acute occlusion or the development of hemodynamically significant stenosis at the LAD and LCx ostia. It is essential to note that in all cases (one stent or two stents), an essential condition is completing the procedure with simultaneous dilation of both vessels (LAD and LCx) (kissing balloons), which allows forming the correct geometry of the LMCA bifurcation segment. Adhering to this condition significantly reduces the risk of late complications (late thrombosis and restenosis).

Calcified lesions are one of the most technically challenging and prognostically unfavorable categories for endovascular treatment. For a long time, in the presence of coronary atherosclerosis with calcium inclusions, the treatment of choice was conservative therapy, and in cases resistant to medical treatment, calcified lesions were an indisputable indication for coronary artery bypass graft surgery.

Balloon dilation of rigid calcified stenoses is traditionally associated with a high risk of acute periprocedural complications. The presence of calcified areas and the extremely uneven distribution of vessel wall elasticity in the lesion area disrupts the normal mechanism of balloon dilation. During balloon inflation, the uneven distribution of force leads to excessive localized impact and is accompanied by a high risk of dissection formation.

On one hand, low pressure during balloon dilation does not effectively impact rigid lesions and leads to the procedure ending with significant residual stenosis. On the other hand, excessive pressure to achieve an optimal result often leads to the development of threatening complications. Balloon dilation of calcified stenoses is associated with occlusive dissections in 10-15% of cases, which on average is 5-6 times higher than the rate of similar complications during the dilation of uncomplicated forms of coronary atherosclerosis.

Attempts to improve endovascular technologies led to the creation of so-called noncompliant balloons made of durable materials, allowing the balloon to maintain its nominal diameter at significant pressure increases. The essence of this technology lies in the even distribution of force across the balloon's surface during inflation. Even pressure distribution prevents excessive balloon overstretching in areas of lower vessel wall resistance.

However, the wider application of this technology revealed its drawbacks. During dilation, the rigidity of noncompliant balloons often led to the so-called "watermelon seed" phenomenon – the balloon slipping off the stenosis during inflation. Inadequate predilation of the stenosis before stent placement can lead to technical difficulties in delivering the endoprosthesis to the intended implantation site. Cases of the stent firmly anchoring in the calcified segment are common, making it impossible to position it correctly. In these situations, the operating physician is usually forced to implant the stent where it is fixed. Attempts to reposition the stent often lead to stent dislodgement from the balloon, which can have catastrophic consequences.

Ineffective predilation of the stenosis creates a risk of incomplete stent expansion. It is a well-established and scientifically proven fact in modern invasive cardiology that incomplete stent expansion is a powerful independent predictor of complications in the postoperative period. The most severe of these is subacute stent thrombosis within the first month after implantation, which is prognostically unfavorable and accompanied by high mortality. The formation of hemodynamically significant restenosis and the recurrence of angina symptoms within the first six months is also a typical consequence of incomplete stent expansion. In some clinical situations, a vicious cycle arises: high pressure is used for optimal predilation, resulting in dissection and necessitating stent implantation. If full expansion is not achieved, the subsequent likelihood of thrombotic complications is very high, and the risk of these complications can only be reduced with aggressive anticoagulant regimens.

Increasing the effectiveness of endovascular treatment for calcified stenoses mainly involved creating effective predilation mechanisms necessary for the safe implantation of endoprostheses. Currently, the search for new technologies for this type of coronary atherosclerosis involves developing effective methods to prepare the stenotic segment for stenting.

As experience in stenting calcified lesions accumulated, researchers formulated the main rule to follow in preparing the lesion for stent implantation. The primary principle of pretreating a structurally heterogeneous calcified stenosis is to achieve maximum homogeneity to ensure the even expansion of the endoprosthesis.

The main endovascular technologies currently used for this purpose are cutting balloons and rotational atherectomy. It is important to note that these technologies are not considered isolated treatment methods for calcified stenoses. The use of these methods is only possible as part of a combined endovascular intervention with coronary stent implantation.

The advent of drug-eluting stents expanded the capabilities of invasive cardiologists in treating calcified lesions and spurred the improvement of debulking technologies – cutting balloons and rotational atherectomy. The use of cutting balloons is a relatively simple technical method similar to traditional balloon angioplasty and does not require special skills. The cutting endovascular balloon is made of noncompliant materials, with longitudinal microblades (usually three) located on the balloon's surface. During predilation of calcified lesions with a cutting balloon, the rigidity of the stenosis is reduced by creating microdissections in the intervention area.

The most effective technology for treating calcified lesions to date is rotational atherectomy. The homogeneity and reduced rigidity of calcified lesions using rotational atherectomy are achieved differently. The high-frequency rotation of a burr (about 60,000 rpm) mechanically fragments the atherosclerotic plaque. The fragment size resulting from high-frequency rotation is minuscule (5 to 15 µm), allowing their removal by the reticuloendothelial system after entering the microcirculatory bed. Mechanical rotation is performed with a rotational atherectomy catheter, which has a diamond-coated burr at its tip, ensuring minimal plaque fragmentation. The high-frequency rotation of the burr allows the fragmentation of hard elements (atherosclerotic plaque) and the deviation of the burr from the normal vessel wall tissue, facilitating safe advancement through the vascular bed.

Rotational atherectomy is a more technically complex method, requiring specific practical skills. Therefore, its use is only possible by high-level specialists with experience in conducting at least 100 endovascular procedures. Nevertheless, its use helps achieve optimal results even in cases of severe rigid lesions, where endovascular treatment was previously not considered.

Venous autografts have less resistance to pathological changes under arterial blood flow conditions compared to the internal thoracic artery. According to various studies, the patency rate of autovenous grafts from the saphenous vein one year after surgery is 80%. Ten years after surgery, only 45% of autovenous grafts remain patent, and more than half of these have hemodynamically significant stenoses.

Most studies on the patency of venous grafts after surgery indicate that in cases of graft failure within the first year, thrombotic occlusion occurs. Since most autovenous grafts fail within the first year post-surgery, this mechanism can be recognized as the leading cause of coronary graft failure of this type. The reasons for the high frequency of thrombosis lie in the specific structure of the venous wall. Its lower elasticity compared to the arterial wall does not allow adaptation to the conditions of increased arterial pressure and ensures optimal blood flow speed through the graft, creating a tendency for blood flow slowing and increased thrombosis. Much research has been devoted to studying the causes of the high frequency of thrombosis in the first year after surgery. As major studies on this topic suggest, the main cause of early venous graft failure is the inability in many cases to maintain optimal blood flow speed through the graft. The middle layer of the venous wall, representing a smooth muscle shell, is poorly developed compared to the arterial wall, which, under arterial blood supply conditions, plays an important role in regulating blood pressure by changing the tone of the vessels and, thus, peripheral resistance. When placed in the arterial bed, the venous vessel experiences increased load, which under high pressure and lack of regulatory mechanisms, can lead to tone disruption, pathological dilation, and ultimately blood flow slowing and thrombosis.

In cases of thrombotic occlusion, the entire graft is usually filled with thrombotic masses. This type of lesion represents a less promising area for endovascular treatment. Firstly, the likelihood of recanalization of a long occlusion is extremely low, and secondly, even with successful recanalization, the large volume of thrombotic masses poses a risk for distal embolization during balloon angioplasty. As time progresses after surgery, the so-called "arterialization" of the venous graft and intimal hyperplasia occur. The graft acquires the necessary adaptive mechanisms for proper blood flow, but as long-term observations show, it becomes susceptible to atherosclerotic lesions no less than the native arterial bed. According to autopsy data, typical atherosclerotic changes of varying degrees are observed in 73% of autovenous grafts three years post-surgery.

Histological studies show that about a month after surgery, grafts begin to undergo significant structural remodeling. Intimal and smooth muscle element hyperplasia is observed within the first two years. These transformations allow the graft to provide the necessary tone levels under arterial pressure conditions and maintain the blood flow speed required for quality perfusion through the graft. Starting from the second year post-surgery, smooth muscle cells are gradually replaced by fibrous tissue, after which atherosclerotic changes may develop, leading to stenosis or occlusion of the graft.

More aggressive atherosclerosis progression in autovenous grafts compared to native coronary arteries is noted in many studies. Autovenous grafts that have maintained proper patency in the first year post-surgery undergo "arterialization" and may become sites for atherosclerosis development. The most frequent location of lesions in these grafts is at the anastomoses with the arterial bed, where the degree of "arterialization" is greatest and blood flow turbulence is high. Several studies on the results of surgical treatment of coronary artery disease have shown that atherosclerosis in venous grafts has pronounced specific features compared to native coronary arteries. It is noted that atherosclerotic plaques in autovenous grafts are larger in mass and volume, and the atherosclerosis process is more aggressive compared to native coronary arteries. It is also mentioned that atherosclerotic plaques in grafts more often have ulcerated surfaces, mural thrombi, and are more prone to rupture and fragmentation. The inflammatory component plays an active role in the development of atherosclerosis in venous grafts, which can lead to thinning of the plaque’s fibrous cap or even its disappearance. Thinning of the fibrous cap of the atherosclerotic plaque, along with the larger diameter of the graft compared to the native coronary artery, contributes to a larger volume of atherosclerotic masses and the diffuse spread of the pathological process in venous grafts.

During the first year after surgery, factors affecting the speed of blood flow through the graft (the condition of the distal bed, the quality of the anastomosis with the coronary artery, and the diameter of the grafted artery) play an extremely important role. These factors significantly influence the quality of outflow and thus determine the speed of blood flow through the graft. In this regard, the work of Koyama J et al is of interest, which evaluates the influence of distal anastomosis defects on blood flow speed in mammary and venous grafts. It was found that pathology of the distal anastomosis of a mammary graft practically does not alter the flow speed characteristics compared to a graft without an anastomosis defect. Meanwhile, a defect in the distal anastomosis of an autovenous graft significantly slows blood flow, explained by the venous wall's inadequate ability to change tone under increased resistance, which in this case is caused by the anastomosis pathology.

Reports on the first results of endovascular treatment in grafts indicate that balloon dilation of atherosclerotically altered aortocoronary grafts was accompanied by low primary success rates and high rates of restenosis development. Unsatisfactory results of balloon dilation in grafts, which are significantly inferior to the results of similar treatment in the native coronary bed, led researchers to focus on studying the morphology of venous graft lesions. The pioneer of balloon angioplasty, Gruentzig, attempted seven angioplasties on grafts in 1979, five of which were successful. However, in three of the five successfully dilated grafts, hemodynamically significant restenosis was observed in the long term, leading Gruentzig to suggest that grafts exhibit a "different kind of disease," which explains the unsatisfactory treatment results.

Many researchers note that during the dilation of atherosclerotic lesions in venous grafts, a significant portion of the atheromatous masses does not move into the deeper layers of the wall but fragments, which can be a source of distal bed microembolization. This is considered by many specialists as the main cause of the no-reflow phenomenon after endovascular interventions. The no-reflow phenomenon refers to a condition where, despite restored artery patency and no residual stenosis or dissection, inadequate coronary perfusion is observed – TIMI (Thrombolysis In Myocardial Infarction) flow grade 0-II. The occurrence of this phenomenon is prognostically extremely unfavorable and is accompanied by myocardial infarction development in 31% and fatal outcomes in 15% of cases.

Unsatisfactory results of aortocoronary graft stenting and the relatively high rate of acute complications have driven the development and implementation of new endovascular technologies aimed at optimizing the results of endovascular treatment. Promising results have been obtained with the use of stenting in combination with the temporary placement of endovascular traps distal to the stent in clinical practice. During stent implantation, when fragmentation of atherosclerotic plaque elements occurs, a microfilter basket is deployed in the distal vessel to capture microemboli carried by the blood flow. After the implantation is complete, the microfilter is collapsed with a special device for atraumatic removal from the coronary bed. This simple but effective method of preventing microembolization is gaining increasing support.

It is also important to note that such procedures (endovascular treatment of aortocoronary grafts) are recommended to be performed only by experienced endovascular surgeons who have completed more than 100 endovascular interventions due to the technical complexities of the procedure. Additionally, the technical features of endovascular treatment of aortocoronary grafts post-coronary artery bypass grafting (CABG) dictate the necessity of equipping the radiology operating room with additional instrumentation to ensure the immediate and long-term safety and effectiveness of endovascular treatment.

All the aforementioned procedures and advancements in minimally invasive endovascular treatments (angioplasty and stenting) represent significant achievements over the past 30-40 years in the treatment of coronary artery disease (atherosclerosis of the coronary arteries). Due to the significant progress in endovascular instrumentation and the accumulated experience of the operating personnel, the number of minimally invasive endovascular procedures in developed countries averages between 80 to 90% of all non-drug treatments for coronary artery disease.

The major breakthrough in endovascular technologies over the past 10 years has been observed in the treatment of so-called peripheral atherosclerosis – atherosclerosis of the brachiocephalic (carotid) arteries and atherosclerosis of the lower limb arteries.

Since the early 1990s, the method of angioplasty and stenting of the carotid arteries has developed rapidly, becoming a real alternative to surgical intervention for atherosclerosis of the cerebral vessels. Despite the invasiveness, need for surgical access, and general anesthesia, surgical endarterectomy long remained the only treatment method for such patients. Angioplasty and stenting were rarely used due to the high risk of distal embolization and ischemic stroke development. The situation fundamentally changed with the advent of endovascular microfilters, which are placed distal to the stenosis during the intervention and block particles larger than the formed elements of blood.

Thanks to the advent of microfilters, endovascular treatment of carotid artery atherosclerosis has become a safe and effective method, allowing for routine stenting in this type of lesion and significantly increasing the number of endovascular procedures performed. Nowadays, both neurologists and endovascular surgery specialists prefer carotid artery stenting for atherosclerotic lesions. The number of stenting procedures worldwide now exceeds the number of surgical endarterectomies. The high effectiveness of endovascular treatment of carotid artery atherosclerosis has been proven in large international studies such as SAPPHIRE, CREST, and others, which compare the effectiveness of endovascular and surgical revascularization for this type of atherosclerosis. These studies have shown significantly lower mortality and stroke rates following stenting compared to surgical endarterectomy. Furthermore, angioplasty and stenting are associated with fewer life-threatening coronary complications (acute myocardial infarction, acute supraventricular, and ventricular arrhythmias) due to their minimally invasive nature and applicability to various high-risk patient categories (patients with lung diseases, diabetes, renal failure, etc.). It is also worth noting that angioplasty and stenting currently hold the top spot over pharmacological prevention and surgical intervention in preventing ischemic stroke, as evidenced by the recent large ACST 2 study comparing the results of endovascular and surgical treatment. When a stent is implanted in a carotid artery affected by an atherosclerotic plaque, the stent material covers the plaque surface, preventing small pieces of the plaque from detaching and entering the brain's blood vessels (embolization), thereby drastically reducing the risk of ischemic stroke.

Carotid Artery Stenting

Carotid artery stenting is not the only area for peripheral endovascular interventions. Atherosclerosis of other locations, particularly renal arteries, the infrarenal section of the aorta, and lower limb arteries, is also traditionally managed with endovascular methods. Angioplasty and stenting in such patients effectively combat renovascular hypertension and prevent ischemic and thromboembolic complications. Endovascular intervention in this patient category helps avoid complex, traumatic surgeries associated with significant blood loss and prolonged rehabilitation.

Rapidly Developing Field of Endovascular Surgery

The rapidly developing field of endovascular surgery includes interventions on lower limb arteries. Because endovascular interventions have firmly established their leading position in treating all major vascular beds (coronary arteries, carotid arteries, renal arteries, lower limb arteries), a new specialty has emerged in modern Russian medicine based on high-tech treatment methods – X-ray endovascular diagnostics and treatment or X-ray surgical diagnostic and treatment methods. This new specialty's formation and rapid development received an additional boost from the widespread introduction of endovascular treatments for lower limb artery atherosclerosis, which, like many other medical fields, was long considered the exclusive domain of open surgical intervention.

For a long time, bypass surgeries were used for occlusive lesions of the lower limb arteries, involving removing a segment of the saphenous vein to use as a bypass graft through the occluded arterial segment. Such interventions, like other types of bypass surgeries on other vascular beds, naturally involved surgical incision, vein extraction, implantation into a new pathway, general anesthesia, and a long rehabilitation period for the patient after the traumatic treatment. Even today, effective treatment of atherosclerotic lower limb arteries is synonymous with surgical intervention.

Minimally Invasive Endovascular Technologies

However, minimally invasive endovascular technologies are gaining more supporters due to their high effectiveness, comparable to surgical treatment. One of the most unfavorable lesions in lower limb artery atherosclerosis is the involvement of the iliac arteries, where occlusion can lead to a more than 50% chance of lower limb amputation.

Many bypass surgeries for iliac artery lesions are associated not only with high trauma and perioperative mortality but also with severe postoperative scarring and adhesions, making further interventions in this area extremely difficult. Additionally, synthetic grafts are short-lived, with 50% becoming occluded within five years. Many experts in lower limb atherosclerosis no longer recommend using synthetic grafts for iliac artery atherosclerosis, which most often leads to lower limb amputation without blood flow restoration intervention. Atherosclerosis of the superficial femoral artery, a common location, also long remained the domain of open surgery. Such atherosclerosis rarely leads to lower limb amputation because the deep femoral artery runs parallel to the superficial femoral artery, providing collateral vessels to the leg arteries, preventing critical ischemia (lack of blood supply and oxygen) of the lower limbs. Long-term surgical intervention for occlusive superficial femoral artery lesions was also prioritized and involved applying a venous graft, typically extracted from the same or neighboring limb. Such interventions, like previous surgeries, carried certain trauma due to significant surgical incisions and general anesthesia. Moreover, the number of veins available in the human body for use as autografts (transplantation of one's tissues) is limited, a significant drawback of the method. Postoperative scars in the intervention area lead to adhesions, which, as atherosclerosis progresses and new lesions develop, complicate both surgical and invasive interventions.

Advanced Technologies

The anatomical structure of the superficial femoral artery (lack of large side branches) means that the vessel is completely thrombosed along its entire length when an atherosclerotic plaque is present. Traditional balloon angioplasty (endovascular treatment) is ineffective even with a stent, as it is challenging to penetrate through an extensive thrombosed arterial segment. However, in the last decade, advanced technologies have emerged, capable of achieving 100% vessel opening results even with complex, rigid, or calcified lesions. For example, one method involves passing occluded sections of the superficial femoral artery with a device generating high-frequency (20kHz) electromechanical vibrations transmitted to the tip of the recanalization catheter. The vibration effect selectively targets areas with higher resistance, ensuring intraluminal passage through the occlusion, including calcified or extremely rigid walls. Other technologies, such as Turbohawk and Jetstream, are intraluminal atherectomy devices that remove atherosclerotic plaque material from the body rather than displacing it into surrounding tissues. This significantly enhances the procedure's effectiveness by reducing the risk of re-stenosis (re-narrowing). To combat this drawback of endovascular treatment, a wide range of new technologies is available – drug-coated balloons and stents. The medication on these balloons and stents prevents the pathological response of the vessel wall to the foreign body and the formation of re-stenosis and inhibits the growth of atherosclerotic plaques.

Finally, one undeniable advantage of modern endovascular interventions is the ability to treat atherosclerotic lower leg arteries. Surgical bypass operations are highly ineffective due to the small vessel diameter and short-lived shunts. In this case, opening vessels endovascularly with drug-coated technologies is a real panacea for patients with diabetes and the so-called "diabetic foot," which affects small lower leg arteries and poses a high risk of trophic ulcers, necrosis, and lower limb amputation.