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The model of acute pulmonary embolism in rabbits demonstrated reduced pulmonary blood flow, cardiac output, left atrial pressure, and blood flow in venae cavae against the background of elevated left pulmonary artery pressure and increased pulmonary vascular resistance. Simultaneously, the blood flow in the superior vena cava decreased to a lesser extent than that in the inferior vena cava, which was a characteristic feature of the model of pulmonary pathology. In contrast, when histamine was infused into the left jugular vein to equally elevate pressure in pulmonary artery as in the above model, the blood flow in the superior vena cava decreased to a greater extent than that in inferior vena cava. During stenosis of inferior vena cava that decreased the cardiac output to the level observed during modeled pulmonary embolism, the blood flows in both venae cavae dropped equally.

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In this literature review, the analysis of the studies of venous blood flow pathology in the inferior Vena cava system using magnetic resonance imaging (MRI) is carried out. Special attention is paid to the attempts made to use this method in the diagnosis of chronic lower limb vein disorders (CVD) through magnetic resonance venography (MRV). Historically and methodically, the gradual introduction of MRV methods in the diagnosis of lower limb vein thrombosis (LEDVT) and venous thromboembolism (VTE) has been shown.Methods of non-contrast MRV based on the effect of blood flow, as in the case of MR-Angiography, are divided into two principal groups: methods based on the amplitude effects of Time-of-Flight (TOF) and methods based on Phase Contrast effects (PC). Techniques for conducting contrast-free MRV are described in detail. Attention is paid to pulse sequences used in the world for visualization of veins in contrast-free MRV in TOF and PC mode (FR-FBI, SPADE, SSFP) and post-processing methods: 2D-TOF MRV FLASH, 2D-TOF MRV CRASS, FIPS, VED, VENS.Contrast-enhanced MRV (CE MRV) is based on the use of “blood pool” contrast agents, which feature the ability to form stable compounds with blood plasma proteins. Worldwidesubstances with magnetic and supermagnetic properties based on gadolinium or iron oxide are used as contrast agents for CE MRV. The result of using these contrast agents is an increase in the quality of visualization due to a better signal to noise ratio (SNR) using 3D image processing (3D CE MRV) using fast sequences: GRE, TFLAS, VESPA, CAT, in conditions of direct and indirect CE MRV.It is noted that in recent years, certain restrictions have been imposed on certain linear contrast agents containing gadolinium in their further use. Therefore, for the purpose of CE MRV, it is efficientl to use only cyclic contrast agents to avoid unnecessary risks.Contrast-free MRV has again received intensive development in recent years, due to the restrictions imposed, one of these methods is direct thrombus imaging (Direct Thrombus Imaging – DTI or Magnetic Resonance Direct Thrombus Imaging - MRDTI) using fast pulse sequences: bSSFP, BBTI, DANTE. The latest research on this LEDVT diagnostic method was published in 2019 and has shown high diagnostic value.For all the most commonly used methods of MRV, specificity and sensitivity are shown.Further MRV in patients with CVD and DVT is a promising diagnostic task in modern phlebology. MRV should be introduced into clinical practice more actively than it is today.