BACKGROUND: Ischemic heart disease is a pathological chronic and acute condition, which is provoked by insufficient blood supply or its complete cessation. To reduce the number of patients, all approaches and studies that can positively affect the prevention and treatment of the disease are important. This is very important in monitoring and treating diseases of all systems and organs, especially in diseases of the cardiovascular system. The aim of our work was to elucidate the relationship between the rheological status of blood, vascular changes and intracardiac hemodynamics in heart failure in coronary artery disease patients with different functional classes. OBJECTIVES: The aim of our work was to elucidate the relationship between the rheological status of blood, vascular changes and intracardiac hemodynamics in heart failure in coronary artery disease patients with different functionalclasses. METHODS: We examined 76 men and women patients with coronary artery disease - I–IV functional class (by New York Heart Association Functional Classification NYHA)), mean age - 59.2±4 years. The control group consisted of 20 apparently healthy volunteers (Woman: Man –1:1), whose average age was 52±3 years. Representatives of the control group did not take any medication during the study period and were apparently healthy. The electrocardiogram of the subjects in the control group corresponded to the norm. All subjects underwent clinical and laboratory studies in a standard way: to describe the rheological status of blood, the erythrocyte aggregability index (EAI), erythrocyte deformability index (EDI), and plasma viscosity were determined; to assess vascular changes - resistance index of resistive arteries (RIRA); to study intracardiac hemodynamics, echocardiology was performed according to the recommendations proposed by the American Association of Physicians. RESULTS: Rheological changes are present from the very beginning of the disease and progress along with the severity of the disease. Therefore, it is possible to assess the severity of the disease based on rheological disorders, which can precede the onset of ischemic heart disease. The vascular status resistance index increases in the early stages of the disease, with I functional class - RIRA increased by 46%. The cardiac index, which determines the adequacy of the global perfusion pressure, is the main indicator of hemodynamics and is negatively related to the increase in erythrocyte aggregation, although this indicator turned out to be statistically unreliable. CONCLUSION: The interpretation of our data will allow us to better understand the pathogenesis of heart failure, as well as recommend a list of tests, and methods that were discussed in the article to assess the clinical condition of patients. Continuing research in the same direction, we believe that we will be able to make adjustments to research methods and to the algorithm for drug therapy