Use of polycaprolactone grafts for small-diameter blood vessels.

Current trends are toward actively developing approaches of tissue engineering, aimed at creating vascular grafts of small diameter. This is due to the existing in cardiovascular surgery demand for prostheses to be used in coronary artery bypass grafting. The present work was undertaken in order to assess possibilities of using smalldiameter vascular grafts made of biodegradable polymer polycaprolactone by means of electrospinning. The authors studied physico-mechanical properties and structure of polycaprolactone grafts, as well as their thromboresistance and patency after implantation into the vascular bed of rats. The obtained results demonstrated optimal physicomechanical properties of the vascular grafts, their biocompatibility, endothelialisation of the internal surface, and infiltration of the graft's wall by cells with the formation of new tissue, accompanied and followed by the development of an extensive intimal layer in the zones of the anastomoses. Hence, the study showed possibilities of using polycaprolactone grafts as vascular prostheses, however requiring their further modification which would promote and contribute to a decrease in hyperplasia of connective tissue in the graft's lumen.

[Effect of polyoxyalkanoate -based cover on properties of suture material].

The results of a surgical intervention and, in particular, reconstructive operations on arteries are largely influenced by suture material. Despite a wide range of choice, the market concerned lacks suture material which would make it possible to decrease the risk of thrombosis in the area of the vascular anastomosis. In order to increase bio- and haemocompatibility, the surface of a polypropylene thread was covered with a layer based on polyoxyalkanoates - polyhydroxybutyrate and copolymer polyhydroxybutyrate-oxyvaleriate (PHBV). The strongest and most uniformly distributed coating of the polypropylene thread was provided by PHBV. We assessed the bio- and haemocompatibility properties of suture material modified by PHBV, revealing that this modification does not exert negative effect on the main components of blood - thrombocytes and erythrocytes. Treatment of the thread's surface with PHBV promoted a significant (p<0.05) decrease in the amount of absorbed proteins in the area of the vascular anastomosis in experiment: the amount of IgM decreased by 26%, that of fibrinogen by 29%, and that of D-Dimer by 281%, being on the whole indicative of bio- and haemocompatibility of the modified suture material.

[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.

[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.

[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.