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Section 4. Medical science
DOI: http://dx.doi.org/10.20534/ESR-17-5.6-16-18
Babadzhanov Sandzhar Abdumuratovich, senior scientific worker of the Department of X-ray endovascular surgery and cardiac rhythm disturbances, Stock Company "Republican Specialized Surgery Center named after academician V. Vakhidov",
candidate of medical sciences E-mail: doctorsanjar@mail.ru Makhkamov Nadzhmitdin Kazimovich, junior research worker of the Department of X-ray endovascular surgery and cardiac rhythm disturbances, Stock Company "Republican Specialized Surgery Center named after academician V. Vakhidov"
Im Vadim Mukhasanovich, junior research worker of the Department of X-ray endovascular surgery and cardiac rhythm disturbances, Stock Company "Republican Specialized Surgery Center named after academician V. Vakhidov"
RISK ASSESSMENT AND FORECASTING OF COMPLICATIONS OF CORONARY ENDOVASCULAR INTERVENTIONS IN PATIENTS WITH ISCHEMIC HEART DISEASE
Abstract: The article examines the issues of research and development of prognostic criteria for complications of coronary endovascular intervention, which is the most common and highly effective method for treatment of ischemic heart disease.
Keywords: myocardial revascularization, forecasting of outcomes, stents, risk assessment, restenosis, endovascular interventions.
Ischemic heart disease (IHD) is characterized by a wide preva- against smoking, reduction of average values of blood pressure and
lence and high mortality among the population. According to the cholesterol), as well as with wide introduction of new effective meth-
World Health Organization (WHO), 5 million 825 thousand peo- ods for diagnostics and treatment of IHD. Despite the improvement
ple died from IHD in 2002 in the world. The maximum number of survival indexes in the US, about 4 million people suffer from isch-
of deaths from IHD accounted for India (1 531 534 people), China emic heart disease in this country and more than 650,000 people die
(702 925 people) and Russia (674 881 people). According to the every year. According to the forecasts ofAmerican scientists, about
latest data, 3.8 million men and 3.4 million women, i. e. 7.2 million 36% deaths will account for cardiovascular diseases by 2020 [3].
people in total, die from ischemic heart disease every year in the According to the National Institute of Health, the cost for treatment
world. According to WHO forecasts, this figure can reach 11 million of coronary atherosclerosis is about $60 billion a year.
by 2020. It is expected that 82% of the global increase in mortality In connection with the abovementioned, the fight against IHD
from IHD will account for developing countries. has a great social and economic importance. This is one of the top-
The main social factors, which predispose to the massive spread priority tasks that face the medicine of the XXI century.
of cardiovascular diseases in these countries, include urbanization, One of the most important achievements of cardiology in the
industrialization, economic backwardness and medical illiteracy of last century was Andreas Grunzig's development of the transluminal
the population. balloon coronary angioplasty (TBCA), which allows to eliminate
In most cases additional risk factors are malnutrition, sedentary the constrictive lesion of coronary artery by endovascular interven-
lifestyle, smoking [1; 2; 7]. tion with minimal surgical trauma.
In recent years the trend towards the decrease in mortality from Primarily, the use of balloon angioplasty was quite often ac-
coronary heart disease has been observed in some developed coun- companied by development of cardiac complications. According to
tries. This is connected with improvement of preventive measures different authors, the incidence of AMI (acute myocardial infarc-
(increase in the level of medical literacy of the population, fight tion) during the procedure and immediate postoperative period was
RISK ASSESSMENT AND FORECASTING OF COMPLICATIONS OF CORONARY ENDOVASCULAR INTERVENTIONS IN PATIENTS WITH ISCHEMIC HEART DISEASE
2-10% [2]. It was possible to forecast the success of endovascular procedure with a high probability ratio only with a local concentric lesion of the coronary artery [1, 5]. The low probability of success, as well as the high incidence of TBCA complications in the case of more complex types of lesion could not help but affect the scale of its use in clinical practice. By the end of the 1980s the indications for TBCA were limited by isolated stenosis of one coronary artery. In the presence of multivessel lesions of the coronary bed, the preference was given, as a rule, to cardiac surgeons.
Practical interest in interventional cardiology increased significantly with the appearance of coronary prostheses or stents. Application of the stenting method in the case of unsatisfactory angiographic results of TBCA (residual stenosis or coronary artery dissection) significantly reduced the incidence of complications of endovascular treatment of IHD. In the course of stent implantation a solid enthetic frame of coronary artery is formed, which squeeze the fragments of the atherosclerotic plaque and intimas to its wall [4; 6]. With the appearance of stents experts in the field of invasive cardiology got the opportunity to eliminate constrictive lesions of different morphology, including a complicated one, which led to the expansion of indications for medical endovascular procedures. So, in the United States 32 300 coronary angioplasty procedures were performed in 1983, and in 1994 — already about 400 000.
Today stenting has a dominant position among other endovascular methods for treatment of IHD. The proportion of stenting procedure from all cardiac interventions is on average 70% [2; 5; 7; 9]. At the same time the incidence of serious hospital cardiac complications when using stents in most centers does not exceed 1% [2; 3; 5].
Introduction of the stenting procedure significantly improved not only immediate but also medium long-term (half-year) results of endovascular treatment of IHD in comparison with balloon angioplasty. Thus, the incidence of the coronary artery restenosis development decreased on average by 50% and now according to the data of different authors it amounts to 10-20% [2; 6; 7; 12; 15]. Nevertheless, the incidence of repeated revascularizations with regard to restenosis remained high and was associated with excessive proliferation of vascular endothelium.
At the beginning of the century stents with an antiproliferative coating were developed and introduced into clinical practice. According to the results of numerous studies, the use of these stents significantly reduced the incidence of restenosis in comparison with the use of conventional coronary prosthesis (without coating), which led to a rapid growth of their popularity among interventional cardiologists [6; 8]. Appearance of drug-coated stents made it possible to significantly reduce the likelihood of restenosis in the previously stented segment and, as a consequence, the number of repeated interventions in the long-term postoperative period [1].
Few disadvantages of stents with antiproliferative coating include the hypersensitivity of some patients to drug components, the likelihood of late thrombosis development (due to disorder of neo-endothelization), the need for appointment of disaggregants for a long time, and high cost [6].
At present time the study of long-term effectiveness of endovascular treatment of IHD is of special interest, in particular the stenting of coronary arteries. Unfortunately, there are very few papers devoted
to this issue and most of them refer only to clinical results, whereas the study of angiographic results of endovascular procedures is given a secondary importance. In large-scale long-term studies scientists are limited usually by determination of incidence of adverse clinical events, such as fatal outcome, myocardial infarction, repeated myocardial revascularization [11; 12; 13]. At the same time there is no detailed analysis of morphological causes of these complications. In this regard, today specialists have diverse opinions regarding the long-term effectiveness of endovascular treatment of IHD.
The question of long-term clinical and angiographic results of repeated endovascular interventions remains to be not more clarified (therefore no less interesting). As most authors think, the disease prognosis is unfavorable in the case of endovascular treatment of coronary artery restenosis, i. e. in the future there is a high risk for renewal of angina and indications for repeated myocardial revascularization [9; 15].
Myocardial revascularization becomes reasonable if its potential positive impact on survival and progress of the disease (symptoms, functional status and/or quality of life) exceeds possible negative consequences of the procedure [2; 8]. Thus, risk assessment plays a significant role in modern clinical practice.
Modern cardiology in recent years has gained great momentum due to the advances of evidence-based medicine. Multicenter studies with tens of thousands of patients resulted in extensive experience that allowed on the evidence basis to develop modern standards for diagnostics and treatment ofvarious conditions in cardiology. When selecting operating tactics besides the estimation of probability of hospital operative mortality, it is necessary to forecast the risk of serious complications in the early postoperative period (perioperative infarction, low cardiac output syndrome, etc.) [5; 8].
The incidence of complications after myocardial revascularization is conditioned by concomitant prevalent atherosclerotic process in aorta and large vessels, which causes at least 2/3 of adverse outcomes of the intervention. It means that probability for development of ischemic episodes of the heart in postoperative period conditions the necessity of studying hemodynamic reserves of the myocardium.
An important practical aspect of the problem is to forecast the outcome of an operative intervention. Clinical problem solving with the help of mathematical modeling methods has its own history. Development and introduction of models focused on clinical application, for example in functional diagnosis and cardiac surgery, are becoming more urgent. The risk level assessment is a multiple-choice problem that cannot be accurately quantified with a simple table. The minimum requirement for the model is approximation of its reactions and properties to physiological and pathophysiological parameters of the organism and also the possibility of forecasting.
According to the literature, when forecasting hospital complications and the outcome of surgical revascularization, the predictors are parameters that characterize the surgical intervention itself (use of artificial circulation, duration of surgery, number of shunts, multivessel lesion, number of stents, etc.), as well as parameters that describe the heart hemodynamics (local and integral contractility, coronary blood flow and its reserve, determined during load testing, degree of coronary blood flow lesion according to coronary angiography data, etc.) [1; 2; 10; 14].
With long-term forecast, such parameters as patency of shunts or stents, level and ratio of blood lipoproteins, disturbance of throm-bocytic hemostasis and immune status play an important role.
International experts developed a number of scales for risk stratification of the myocardial revascularization.
EuroSCORE estimates the risk of surgical mortality. This scale is based on old data and often leads to the excess of death risk. Therefore, it is not recommended for use in the future.
The scale EuroSCORE II turned out to be most reliable in the assessment of the degree of death risk, which proved its effectiveness in researches carried out on the group of patients, who underwent coronary artery bypass surgery.
Today the method most commonly used in clinical practice is the forecast of disease developed by American experts of Agency For Health Care Policy And Research (AHCPR) National Heart, Lung and Blood Institute (NHLBI). It should be noted that the risk stratification proposed by the experts ofAHCPR and NHLBI was based on retrospective data. However, prospective studies, in which patients are divided into risk groups at the beginning ofthe study and then the outcomes are compared at the end of the study period, are more important.
The multiplicity of factors that influence the course of IHD and the complexity of the disease mechanisms explain the desire to increase the accuracy of forecasts via a combination of symptoms.
Various authors used in the course of risk model formulation such factors as age, heart rate, systolic blood pressure, ST-segment depression separately from angina attack, heart failure and markers of myocardial necrosis, etc.
However, we should not ignore anatomical features of the coronary artery lesion. Undoubtedly, when there is a diffuse lesion of proximal and middle sections of coronary bed, long-term results are associated with a higher risk of restenosis [1].
At the same time, rapid progress that is continuously lasting in endovascular surgery during the last 20 years has allowed coronary stenting to come as close as possible to modern results of coronary bypass in multivessel lesions.
Thus, the issues of forecasting the outcomes and probable complications in coronary angioplasty and stenting are an actual problem of modern cardiology. Development of effective methods for forecasting of these complications would improve the results of endovascular interventions.
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