[Quo vadimus? Fundamental problems of developing hybrid prostheses of thoracic aorta]. / Quo vadimus? Fundamental'nye problemy razrabotki gibridnykh protezov grudnoi aorty.

This article is a review briefly characterizing the state of the art of hybrid surgery of the thoracic aorta using the frozen elephant trunk technique worldwide and in Russia, also discussing unsolved problems of fundamental science, being key issues in creation of new models of hybrid prostheses of the thoracic aorta. The main attention is paid to the problem of radial stiffness of the stent-graft portion of the prosthesis. Performed is a detailed analysis of the factors influencing this characteristic of the sent graft: shape, size and number of cells of the stent element, thickness of the nitinol wire it is made of, method of edge connection, nitinol properties depending on the alloy grade and methods of thermoforming. It is shown that excessive stiffness leads to the development of d-SINE syndrome. This is followed by discussing the problem of optimal stiffness of stent grafts, based on the design of stent graft elements and elastic properties of the wall of the true channel of a dissecting aortic aneurysm. Also proposed is an approach to solving the problem of d-SINE, consisting in creation of conical stent grafts and/or a gradual decrease of radial stiffness of stent elements in the direction of the distal portion. Comprehensively addressed are disadvantages of the graft portion of the prosthesis, in 95% of items made of polyethylene terephthalate fiber: susceptibility to degradation associated with manufacturing defects and intraoperative microdamages, abrasive effect in the zone of contact with stent elements, partial postoperative hydrolysis and an inflammatory reaction to a foreign body, often being clinically pronounced. Also touched upon are certain aspects of creating hermetic coatings of the graft portion, with the use of vancomycin possessing low cytotoxicity as part of an antibacterial component being promising. As a whole, it is demonstrated that advances in creating a novel generation of hybrid prostheses should be associated with new approaches and materials, to be obtained at the junction of medicine and fundamental sciences.

[Metabolic and genetic predictors of restenosis and thrombosis of arterial bioprostheses in the femoropopliteal position].

The present study was aimed at analysing the role of certain cytokines in the development of restenosis and thrombosis of biological prostheses "KemAngioprosthesis", as well as assessing the effect of polymorphic variants of genes on expression of pro- and anti-inflammatory interleukins. Group One (n=52) was composed of patients with an unfavourable outcome (prosthesis restenosis, accompanied by thrombosis in 35 patients). Group Two (n=59) comprised patients with functioning and unaltered prostheses. Group One patients were found to have a significantly higher level of the marker of chronic inflammation IgG and IL-8, amounting respectively to 22.43±0.75 mg/ml and to 6.34±1.008 pg/ml and 16.35±0.84 mg/ml (p=0.01) and 3.96±0.399 pg/ml (p=0.01) in Group Two patients. Analysing the effect of polymorphic variants of genes on expression of pro- and anti-inflammatory interleukins showed that polymorphism of genes of proinflammatory cytokines (TNFα, IL-8 and IL-6) is high producing and polymorphism of the gene of anti-inflammatory cytokine IL-10 is low producing. Besides, we noted a clear-cut tendency toward higher incidence of polymorphic alleles of genes of proinflammatory cytokines in Group One patients.

[Effect of an educational program on effectiveness and safety of anticoagulant therapy in patients with prostheses of cardiac valves].

We analyzed effectiveness and safety of anticoagulant therapy in patients with prostheses of cardiac valves at the background of educational program and without special training. We revealed positive effect of educational program during participation in which in 80 cases (67.8%) patients determined international normalized ratio every month and in 50 of them (62,5%) level of hypocoagulation corresponded to target range (p=0.001). At the background of educational program rate of thrombotic complications was 2.73% per patient year, at the background of no educational program - 4.90% per patient year (p=0.040) while rates of hemorrhagic complications were 2.73 and 7.20% per patient year, respectively (p=0.002).

[Comparative analysis of arterial bioprostheses with various antithrombotic modification].

The present study was aimed at comparing the results of remote patency ol arterial bioprosthcses «KemAngioprosthesis¼ in infrainguinal position with various antithromhotic modifi cation. We analyzed the outcomes in a total of 133 patients who were subdivided into two groups: Group I (n=91) underwent implantation of hioprostheses with antithrombotic modifi calion by non-fractionated heparin. and Group II (n=42) received prostheses treated with low-molecular-weight heparin «Clexane¼. Patients of the both groups underwent comprehensive analysis of the haemostatic system, blood plasma lipid spectrum, as well as duplex scanning of the prosthesis. 39 (42.9%) Group I patients and 6 (13.6%) Group II patients were found to have developed thromboses. Besides, 14 (I5.4%) Group I patients were diagnosed as hawing restenosis of the anastomosis site, with this complication observed in 3 (7.3%) Group II patients. The results of the analysis demonstrated better remote patency of bioprostheses with antithromhotic modifi cation by low-molecular-weight heparin «Clexane¼. Dynamic follow up of the patients made it possible to carry out timely correction of medicamentous therapy, as well as at early stages to reveal restenosis of anastomoses followed by endovascular correction.

[Metabolic and surgical predictors of restenoses and thromboses of biological grafts in the infrainguinal position].

The present study was aimed at revealing metabolic and surgical predictors of restenoses and thromboses of biological grafts "KemAngioprosthesis" in the infrainguinal position in the remote postoperative period. A total of 65patients (54.2% of the whole group) with primarily functioning bioprostheses underwent dispensary follow-up (consisting of comprehensive analysis of the haemostasis system, blood plasma lipid spectrum, findings of duplex scanning of the prosthesis and anastomosis zones). Based on the laboratory findings (fibrinogen, index of atherogenicity, cholesterol), the patients were subdivided into two groups: Group One (n=27) consisted ofpatients with normal values, and Group Two (n=38) was composed of those with one or more parameters exceeding the norm. Fifteen Group Two patients were found to have stenoses of the anastomosis zones. Based on the results ofthe study we determined a clear relationship between the development of complications and impairments in the system of haemostasis and lipid metabolism. All patients from Group Two whose the remote postoperative period was complicated by stenoses of anastomoses showed hypercholesterolemia, dyslipidemia, and platelet hyperaggregation, regardless of the terms of the development of the complication. Once stenoses developed within 3-to-18 months postoperatively, the levels offibrinogen and soluble fibrin monomeric complexes were elevated. Analysing surgical predictors of restenoses showed that the technique of establishing either an "end-to-end-" or "end-to-side" anastomosis exerted no influence on the incidence rate of restenoses in the remote postoperative period.

[Sorption and contact-activating properties of the <> anastomosis zone: effect of suture material (communication II)].

The authors have carried out a comparative analysis of the interaction between two types of suture material with blood components, as well as studied the effect of heparin-mediated modification on the sorption and contact-activating processes in the zone of the anastomosis. The blood-compatible properties of the latter was assesses in vitro. It was determined that by minute 120 of the contact with blood, the largest amount of protein is had been absorbed by the anastomoses performed using the Prolene thread - 112 microg/cm2. Heparin-mediated modification made it possible to dramatically decrease the amount of the absorbed proteins. On the anastomoses performed with TiNi, additional treatment with heparin lead to an inconsiderable decrease in the protein amount. When identifying the absorbed proteins, we revealed dependence on the type of the suture material and modification with heparin. After a 60-minute contact with blood in the area of the anastomosis made with TiNi, absorbed were: albumin, immunoglobulins A, G, and transferrin. When using the Prolene thread, fibrinogen was noted to join. Additional heparinization exerted a favourable effect on the sorption processes in the area of the anastomosis wherein predominantly albumin and immunoglobulins A and G are predominantly absorbed. The parameters of the peak values and the rate of blood platelet aggregation were minimal in the area of the anastomoses done with TiNi with an additional treatment with heparin.

[Development of a venous-valve biological prosthetic graft for treatment of valvular insufficiency].

The present study was undertaken to experimentally assess a possibility of creating a xenogeneic biological venous-valve prosthetic graft using the vv. saphena medialis of the cattle. The findings obtained in the amino-acid analysis demonstrated that diglycidyl ether ofethylene glycol (DEEG) is an efficient suturing agent for xenoveins. Suturing collagen with DEEG by qualitative and quantitative characteristics appeared superior to treatment with glutaric aldehyde (GA); the content of hydroxylysine was by 30%, and that of lysine by 360% less than in the samples treated with GA. Besides, DEEG reacts with histidine, tyrosine and methionine. The strength characteristics of the DEEG-preserved xenoveins tended to decrease, while elasticity tended to increase, as compared with the GA-treated ones. Treatment with DEEG makes it possible for the material to preserve plasticity, which is of major importance for the appropriate performance of the leaflet apparatus of the xenovein. The amount of the immobilised heparin was determined by means of H34 labelling. It was found that the amount of non-fractionated heparin of "Belmedpreparations", bound to the DEEG-treated surface of xenoveins equalled 6.21 microy/mg. While the amount of immobilized low-molecular-weight heparin "Clexan" was 3.9 microg/mg, with that of non-fractionated heparin "Biochemie" equalling 3.41 microg/mg. For the preserved xenoveins, we used the method of layer-by-layer modification, i.e., "heparin-albumin-heparin". The surface modified by means of low-molecular-weight heparin "Clexan" was noted to have the smoothest relief. This approach appears to show promise in rendering venous-valve prosthetic grafts highly resistant to thrombogenesis.

[Transformation of bioprosthesis-artery anastomotic area after blood exposure: the effect of suture material].

Vascular graft implantation is accompanied with tissue reaction which is determined partially by the nature of suture material. In experiments in vitro edges of arterial diepoxid-preserved bioprostheses were sutured with Prolene filament, nickelide-titanium wire (TiNi) or absorbable polydioxanone monofilament (PDS). Morphological changes in anastomotic area after blood exposure were assessed with scanning electronic microscope. Protein deposits in anastomotic area were detected 5 min after blood exposure, being more loose and bulky around Prolene sutures. The protein layer became more compact 120 min since blood exposure. Most homogeneous protein sorption was over TiNi-sutured anastomoses. Suture material affected blood cells as well - some red cells have transformed into echinocytes. Heparin-modified samples demonstrated less negative impact of suture material in anastomotic area. The worst results after 120 min of blood exposure were obtained for PDS filaments.

[Three-dimensional visualization of medical tomographic data using a modern personal computer].

The authors review experience of three-dimensional tomographic reconstructions performed by means of a modern personal computer. Basic algorithms of volume reconstruction, their implementation on Windows platform, and their comparison are discussed from radiological point of view. A hardware configuration of a Pentium class workstation for medical volume visualization is proposed; its productivity in fulfilling real tasks is evaluated.

[Twelve-year experience of bioprosthesis implantation into infrainguinal arteries].

The study presents the results of 315 infrainguinal artery reconstructions with bioprostheses from bovine internal mammary artery treated with 5% solution of diepoxide (trade name "KemAngioprosthesis"). Primary patency of KemAngioprostheses was 37.5% (n=239) in above-knee and 7.4% (n=52) in below-knee femoropopliteal bypasses in 8-year period, as well as 14.9% (n=24) in femorotibial bypass in 4.5-year period. Primary patency was significantly worse in cases of poor outflow from legs, lower limb critical ischemia, in cases of "end-to-side" anastomosis type, as well as in patients with concomitant ischemic heart disease and hypertension. KemAngioprostheses demonstrated no new or unknown complications. The most common complication was thrombosis (45.1%); infections occurred in 4.1%, hemorrhage - in 1% and biodegradation manifested by aneurysms and ectasia - in 1.9% cases. Indications for KemAngioprosthesis implantations include severe, limb-threatening ischemia with unavailable autologous vein or simultaneous two-segment arterial reconstructions in grade III-IV acute or chronic ischemia. Besides, KemAngioprostheses can be successfully used in above-knee femoropopliteal reconstructions.

[Three-dimensional visualization of low-field MRI data using personal computer]. / Trekhmernaia vizualizatsiia dannykh nizkopol'noi MRT s pomoshch'iu personal'nogo komp'iutera.

An experience of three-dimensional reconstruction of low-field MRI data using a modern personal computer and Windows software is presented. A value of volume visualization in routine diagnostics and areas of its effective use are shown. Pulse sequences best suitable for volume reconstruction are selected. Performance of high-end PC in visualization of medical data is evaluated.

[Study of heart valve xenobioprostheses by ESR]. / Izuchenie ksenobioprotezov klapanov serdtsa metodom EPR.

Copper (II) ions were used as paramagnetic labels to study the role of functional groups of structural proteins (SP) of xenobioprosthetic valves in the process of transition metal ions coordination as well as for investigation of changes in complexing properties of these proteins under influence of the recipient media. The dependence of Cu(II) coordination sphere composition in complexes with SP on the pH-value has been determined. Research of influence of the valves' calcification process on the coordination properties of the SP are in progress.

[10 years' experience of heart valve bioprostheses. Present status and future development]. / 10-letnii opyt bioprotezirovaniia klapanov serdtsa. Sovremennoe sostoianie i perespektivy razvitiia.

Long-term results of mitral valve replacement with bioprostheses of three original designs are overviewed. Refinement of the supporting framework design, and of modelling and conservation methodologies has made it possible to improve the survival rates and provided for the absence of specific complications in two groups of patients. Experimental evidence allows for anticipating an increase in the terms of bioprostheses performance.

[A new approach to the creation of heart valve xenograft bioprostheses resistant to calcification]. / Novyi podkhod k sozdaniiu ksenobioprotezov klapanov serdtsa, rezistentnykh k kal'tsifikatsii.

The calcium binding activity of xenograft tissue in stages of modification with papain, diphosphonates, and heparin was studied on a model of accelerated calcification in subcutaneous implantation of cusps of pig's aortic bioprostheses to 42 rats. In immobilization of 3-amino-1-oxypropylidendiphosphonic acid and xydiphon the amount of calcium in the implants reduced 50 times as compared to the control. The first stage of ion-covalent heparin immobilization--treatment with albumin--increased the calcium-binding activity of the biomaterial, but subsequent heparinization reduced again the calcium content in the cusp tissue to the level attained in the stage of diphosphonate immobilization. The results of the chemical analysis correlated with the findings of morphological examination. Besides, the new method of treatment made it possible to increase the strength of the biological tissue by 20%. This method of storage of bioprostheses is promising for clinical approbation.

[Ways to prevent the calcification of heart valve bioprostheses]. / Puti profilaktiki kal'tsifikatsii bioprotezov klapanov serdtsa.

The influence of the method of preservation and application of medicinal preparation xydiphone on the process of calcification of xenograft bioprostheses in a classic model of subcutaneous implantation of bioprosthesis cusps in rats has been studied. It is estimated that fermentative processing does not influence the intensity of calcification, while the immobilization of heparin to tissue decreases the amount of calcium in implants 4.5 times. Combination of heparin immobilization with peroral administration of xydiphone results in summing up of the effects, decreasing the amount of calcium in experimental set of cusps up to the level of nonimplanted ones.