The article presents new insights into the mechanisms underlying bioprosthetic heart valve dysfunctions based on the medical literature analysis. We highlighted the main pathogenetic mechanisms causing dysfunctions of bioprosthetic heart valves among the well-known and recently studied ones. In addition to the process of natural “aging” of the valve tissue that develops during continuous cyclic mechanical loads and is accompanied by the formation of calcification foci (passive and active calcification process), the negative impact of prosthesis- and recipientrelated factors has been evaluated. The prosthesis-related factors contributing to the development of dysfunctions include technological and technical factors, which may produce negative effects on bioprosthetic heart valves during the preimplantation preparation and implantation itself. Main dysmetabolic, immune, hemostasis and hyperproliferative (hyperplastic) mechanisms have been reviewed from the standpoint of the recipient-related factors that may shorten the lifespan of bioprostheses. Therefore, we propose a classification of bioprosthetic heart valve dysfunctions based on the underlying pathogenetic mechanisms and specific morphological patterns.

Background Currently, the search for the bioactive molecules capable of promoting formation of the vascular tissue is still ongoing. We have previously demonstrated that incorporation of the growth factors and chemoattractant molecules into the biodegradable tubular scaffolds can increase their primary patency upon the implantation into rat abdominal aorta. However, further studies are required to investigate tissue remodeling using functionalized vascular grafts with the same diameter as a replaced native vessel. Aim To investigate the specific aspects of de novo vascular tissue formation and calcification employing rat abdominal aorta interposition model and vascular grafts with 1.5 mm diameter with incorporated vascular endothelial growth factor (VEGF), basic fibroblast growth factor (bFGF), and stromal cell-derived factor (SDF)-1α. Methods Tubular grafts with a diameter of 1.5 mm were blended of poly(3-hydroxybutyrateco-3-hydroxyvalerate) and poly(ε-caprolactone) (PHBV/PCL). Grafts without growth factors were fabricated using standard electrospinning technique whilst grafts with incorporated growth factors were prepared utilizing emulsion electrospinning. VEGF was incorporated into the inner third, whereas bFGF and SDF-1α were incorporated into the outer two-thirds of the graft. Grafts were implanted into the abdominal aortas of Wistar rats for 1, 3, 6, and 12 months following scanning electron microscopy along with histological and immunofluorescent examination. Results Primary patency of the grafts with VEGF, bFGF, and SDF-1α reached 93% indicative of structural integrity of the vascular tissue. Neither signs of inflammation nor severe calcification was detected. Conclusion As in 2 mm diameter vascular grafts, incorporation of bioactive factors into 1.5 mm diameter grafts increased their long-term primary patency and improved vascular tissue formation in comparison with non-modified grafts.

 

 

Aim. To assess the immediate and long-term outcomes after bioprosthetic mitral valve replacement with the preservation of the subvalvular apparatus. Methods. 304 patients who underwent primary bioprosthetic mitral valve replacement in the period from 2001 to 2009 were included in the study. Patients were enrolled into two groups with either preserved subvalvular structures (Group 1. n = 142, 47%) or resected structures (Group 2, n = 162) during bioprosthetic mitral valve replacement. For the unbiased assessment of the efficiency of valve-preserving approach, randomly selected patients from Group 1 (n = 75) and Group 2 (n = 40) underwent preoperative and postoperative invasive monitoring of the central hemodynamics using the Swan-Ganz thermodilution catheter. Results In-hospital mortality was 1.4% (n = 2) in Group 1 and 4.3% in Group 2. The most common cause of death was acute left ventricular failure. We found that the preservation of subvalvular structures allows ensuring the optimal linear and volumetric echocardiography parameters in the immediate postoperative period, despite the hemodynamic profile of the defect. However, the positive effects were more pronounced in patients with more severe mitral regurgitation. Patients with preserved subvalvular structures had more durable surgical mitral valve replacement according to the echocardiographic findings in the long-term period. The invasive monitoring of central hemodynamics allowed determining that total subvalvular apparatus preservation was associated with more significant pressure decline in the pulmonary circulation (mean pulmonary arterial pressure and pulmonary capillary wedge pressure) and improved cardiac index and output. Posterior leaflet preservation was associated with less pronounced changes and patients who underwent routine mitral valve replacement had the worst intermediate outcomes. Conclusion The results of the presented study suggest that the preservation of subvalvular apparatus, unless otherwise indicated, is associated with improved immediate and long-term outcomes after mitral valve replacement.

 

Aim. To assess clinical and hemodynamic outcomes of aortic valve replacement with xenoaortic biological prosthesis “Aspire Vascutek” and xenopericardial biological prosthesis “UniLine”. Methods. 130 patients who underwent aortic valve replacement with bioprostheses in the period from October 2012 to March 2016 were included in the study. All patients were enrolled into two groups according to the model of the implanted device. 65 recipients of xenoaortic bioprostheses “Aspire Vascutek” were included in Group 1, whereas patients (n = 65) xenopericardial bioprostheses “UniLine” were assigned in Group 2. Males prevailed in Group 1 (63%, the mean age - 66.4±5.5 years). 85% of Group 1 patients had heart failure Strazhesko-Vasilenko IIA grade and 94% of patients had chronic heart failure NYHA III. Similarly, male patients (58%) prevailed in Group 2. The mean age of Group 2 patients was 66.5±3.65 years. All patients in Group 2 II had heart failure Strazhesko-Vasilenko IIA grade and chronic heart failure NYHA III. Results Two patients in Group 1 died in the early postoperative period (the overall mortality was 1.5%). All patients had chronic heart failure NYHA I-II at discharge. Peak transvalvular pressure gradient significantly decreased in the in-hospital period, particularly in Group 2 patients (82,3±22,7 mm Hg vs. 28.8±7.6 mm Hg). 88% of Group 1 patients underwent the 60-month follow-up, and 96% of Group 2 patients - the 48-month follow-up. Transvalvular pressure gradients decreased progressively in both study groups within 60 months follow-up. This decrease was more pronounced in recipients of xenopericardial biological prostheses. Conclusion. Aortic valve replacement with xenopericardial bioprostheses “UniLine” and xenoaortic bioprostheses “Aspire Vascutek” for aortic valvular disease allows treating intracardiac hemodynamic derangements and achieving good clinical and hemodynamic outcomes.

Background Heart valve replacement with mechanical prostheses in elderly patients is associated with increased risk of bleeding due to the need of lifelong indirect anticoagulant therapy. Therefore, biological heart valve prosthesis is an option of choice. Aim To estimate long-term results of aortic and mitral valve replacement with xenopericardial prosthesis «BioLAB». Methods 150 stented biological prostheses «BioLAB» were implanted into the aortic and mitral position in the Department of Emergency Surgery for Acquired Heart Disease in the period from January 1993 to December 2008. 50 stentless biological prostheses «BioLAB» were implanted in the aortic position in the period from January 2008 to December 2012. Results 1-, 5- and 10-years survival in the recipients of stented xenopericardial prostheses «BioLAB» implanted in aortic position was 91.1±2.9%, 85.3±6.1% and 85.3±6.1%, respectively. 5-, 10- and 15-years survival among those who received mitral valve replacement was 72.31%±5.56%, 55.18%±6.61%, and 22.77%±12.13%, respectively. There were no cases of redo surgeries for valve tissue degeneration among the recipients of stented and stentless aortic valve prostheses within the follow-up. 10-, 12- and 15-years freedom from mitral valve degeneration was 61.08±7.32%, 50.21±9.56%, and 43.6±10.65%. Conclusion Stented xenopericardial bioprostheses «BioLAB» implanted in the aortic position provide good and encouraging hemodynamic results in the long-term period time. There were no signs of tissue degeneration of the stented heart valves within the 10-years follow-up. Similar results were obtained for the stentless bioprosthesis within the 7-years follow-up. The period of 8.5 years after mitral valve replacement with «BioLAB» is critical for tissue degeneration of bioprosthesis.

Aim The aim of this study was to compare the results of right ventricular outflow tract reconstruction during the Ross procedure with pulmonary allografts versus diepoxide-treated pericardial xenografts. Methods Between 1998 and 2015, 793 adult patients underwent the Ross procedure. The right ventricular outflow tract reconstruction was performed with pulmonary allografts in 185 patients, diepoxide-treated pericardial xenografts in 402 patients. Two groups of patients (122 patients in each group) were allocated using «propensity score matching»: the allograft group (pulmonary allograft) and the xenograft group (xenograft). Surgical results in two groups were assessed. Results The overall early mortality rate in both groups was 2.5%. The mean follow-up was 5,1±2,6 years in the allograft group and 5,2±2,8 years in xenograft group (p = 0,692). The 5-year survival rate did not differ between the study groups (93,7±2,6% in the allograft group versus 94,02±2,4% in the xenograft group, p = 0.748). The peak pressure gradients across the right ventricular outflow tract in early and mid-term follow-up were significantly higher in the xenograft group. Two patients in the xenograft group underwent redo surgeries due to the graft failure. There were no reoperations in the allograft group (p = 0,176). The freedom from right ventricular outflow tract reoperations was 96,3±2,7% for the xenograft group. Conclusion The diepoxide-treated pericardial xenografts demonstrates acceptable haemodynamic results at the mid-term follow-up and could be considered as an alternative to allografts for right ventricular outflow tract reconstruction during the Ross procedure in adults. Further study focused on the assessment of the longterm results are required.

Background The current study highlights potential benefits of using ePTFE, a polymeric material, as the main component suitable for fabrication of prosthetic heart valves. Novel polymeric materials seem to be promising for replacing biological elements commonly used in medical products for cardiovascular surgery. High biocompatibility and mechanical properties prolong their lifespan during direct blood contact. Nevertheless, it is necessary to conduct a series of specific tests to determine their properties and benefits of their application. Despite well-known biological properties of ePTFE, there are few studies assessing it as a material for heart valve leaflets. Aim To evaluate the mechanical properties of the commercially available sample of ePTFE and to conduct a numerical experiment assessing its potential for the application. Methods The polymer properties (Gore & Associates Inc., USA) were evaluated under uniaxial tension in two mutually perpendicular directions to determine the degree of anisotropy of the material. A xenopericardial patch (ZAO “NeoCor”, Russia), routinely used for the fabrication of bioprosthetic leaflets, was taken as the control sample. The spatial model of the investigated material was carried out in CAD SolidWorks 2016 (Dassault Systemes, USA). Numerical modeling of the samples was performed with the finite element method using the orthotropic material model in the Abaqus/CAE (Dassault Systemes, USA). Results There are significant difference found in the mechanical properties of the studied materials: the tension at stretching of ePTFE in the longitudinal and transverse directions differed from xenopericardium by 1.9 and 7.5 times, respectively (p<0.05). The elongation before rupture of ePTFE in direction I and direction II was greater than that of xenopericardium (2.39 vs. 1.9 times, respectively). Numerical modeling demonstrated insignificant qualitative differences in the valve opening while applying pressure equal to normal physiological pressure>< 0.05). The elongation before rupture of ePTFE in direction I and direction II was greater than that of xenopericardium (2.39 vs. 1.9 times, respectively). Numerical modeling demonstrated insignificant qualitative differences in the valve opening while applying pressure equal to normal physiological pressure and low pressure. In addition, the zones of high stress in commissural racks, which are critical zones for fatigue resistance, have been identified, albeit require additional in vitro research. Conclusion Mechanical properties of ePTFE suggests it to be a promising polymeric material suitable for fabrication of flexible leaflets of the heart valve prosthesis. It has similar leaflet functioning, compared with the xenopericardium sample, routinely used in manufacturing. ePTFE is more resistant to rupture, which confirms its greater fatigue strength. However, it requires further study by advanced methods.

Background We fabricated biodegradable, bioactive scaffolds to guide the differentiation of endothelial progenitor cells. Aim To study in vitro activity of the bioactive factors incorporated into the poly (3-hydroxubutyrate-co-3-hydroxyvalerate)/poly(ε-caprolactone) (PHBV/PCL) scaffolds. Methods Nonwoven scaffolds were blended of PHBV and PCL utilizing either separate or combined incorporation of vascular endothelial growth factor (VEGF), basic fibroblast growth factor (bFGF), and stromal cell-derived factor-1α (SDF-1α) by emulsion electrospinning. We further studied adhesion, viability, and proliferation of EA.hy 926 endothelial cells cultured on these scaffolds and evaluated vasculogenesis, cell index, and secretory profile in response to the addition of abovementioned bioactive factors. Results We showed that VEGF, bFGF, and SDF-1α retain their bioactivity upon the incorporation into the PHBV/PCL scaffolds. Scaffolds with all three bioactive factors incorporated demonstrated superior performance in comparison with those containing any of these factors alone. Diffusion of the bioactive factors into the culture medium stimulated the secretion of interleukin-10, and VE-cadherin by endothelial cells that indicated anti-inflammatory response and tight intercellular junctions. We also detected the low level of secreted VEGF-A from the scaffolds with VEGF suggestive of its physiological regulation. Conclusion Bioactive factors retain their bioactivity upon the incorporation into the PHBV/ PCL scaffolds. Combination of VEGF, bFGF, and SDF-1a improves cellular response compared to the incorporation of any of these factors alone.

Aim To determine optimal approaches of demineralized bone tissue processing after preservation to ensure efficient seeding of chondrocytes. Methods Demineralized bone matrix specimens sized 1 x 1 x 1 cm³ were used in the experiment. A purification method ensuring the removal of cytotoxic substances from the matrices has been developed. It consists of a multi-stage soaking of the specimens in H₂O, 0.1H NaOH, 1N NaOH, H₂O and DPBS until a neutral pH is reached. After chemical purification (a 3-stage process), all the specimens were subjected to sonication for 1 minute at 5W to improve cell adhesion. The water was changed after each exposure. Then, the water was replaced to DPBS and the specimens were sonicated for 1 minute at 5W. After it, the sample was placed in a neutral medium (pH 7.0). The matrices undergoing sonicated procession were seeded with cells. Hyaline cartilage of minipigs was used as a source of the cells. Chondrocytes were isolated using collagenase II digestion and cultured for 20 days in the culture flasks. Passage 1 chondrocytes were seeded on the matrices. DBM were pretreated with a 1% gelatin solution to improve the efficiency of cell seeding. The microtitration viability test estimating the impact of the extract obtained during sonation cycles on cell viability was performed to determine whether these matrices may be seeded with chondrocytes. The test was performed on the lag- and log-phase cells. The effect of the extract on the cells lasted around 3 days. Results Extract-treated chondrocytes during the lag-phase showed a direct dose-dependent cytotoxic effect, compared to extract-treated chondrocytes during the log-phase. Low efficiency of DBM was associated with both, the stringent requirements for the manufacturing process of DBM and the subsequent matrices processing, including the cell growth phases. The increased cell migration depth into the matrices resulted in the disturbances of the microcirculation, leading to the insufficient cell feeding and slowed down metabolic processes. Conclusion The efficiency of DBM cell seeding depends on the matrix processing, its cytotoxic effect and architectonics. The problem of slowing down the metabolism of cells in DMB may be solved by the application of the combined purification technique, i.e. chemical and ultrasonic purification methods. The obtained results prove the necessity of using mechanical and electrical stimuli for the normal functioning of bone and cartilage tissue cells within the matrix.

Background. Despite recent numerous studies, etiopathogenesis, treatment and rehabilitation of children with heart rhythm disorders haven’t been studied well. We paid attention to the significant impact of mineral nutrients on cardiac activity, while addressing to the viable solutions. Aim. To measure the levels of essential and conditionally essential mineral nutrients and to determine any relationships between their concentrations in hair and in the intraoperative biopsy specimens obtained from children with congenital heart disease and heart rhythm disorders. Methods 55 children (34 boys and 21 girls) aged 6 to 17 years with different heart rhythm disorders and congenital heart disease were included in the study. Levels of 15 essential mineral nutrients (calcium, potassium, magnesium, sodium, phosphorus, sulfur, chromium, copper, iron, iodine, cobalt, manganese, molybdenum, selenium, zinc) and 3 conditionally essential nutrients (boron, silicon, vanadium) were measured in hair and in the intraoperative biopsy specimens obtained from children with congenital heart disease using inductively coupled plasma atomic emission spectrometry and electrothermal atomization atomic absorption spectrometry. The results of the study were processed using variational and alternative statistic methods with the commercially available software “MedStat”. Results The lack of essential nutrients (K, Mn, Se, Cr, P, Co, S, Cu, Na, Mo) and conditionally essential mineral, Si, in the intraoperative biopsy specimens of the heart and great arteries has been found. The direct strong correlation between the levels of essential (K, Mn, Se, Cr, Co) and conditionally essential (Si) minerals in hair and heart tissues of children with congenital heart disease and heart rhythm disorders has been determined. Conclusion The deficit of essential (potassium, manganese, selenium, chromium, phosphorus, cobalt, sulfur, copper, sodium, molybdenum) and conditionally essential (silicon) mineral nutrients, and the direct strong correlation between their levels in hair and heart tissues of children with congenital heart disease and heart rhythm disorders allows using hair as a biosubstrate, which is highly informative for the measurement of nutrients in the human body.

 

Aim. To assess myocardial contractile function in dogs after clinical death following acute myocardial infarction and to determine its role in the development of hemodynamic derangements after cardiopulmonary resuscitation. Methods. 180 dogs included in the experiment received pentobarbital anesthesia to assess contractile function and systemic hemodynamics after a 5-min clinical death caused by myocardial infarction. Results Dogs had phase changes in the myocardial contractile function with its initial increase, subsequent depression and normalization in the early postresuscitation period after myocardial infarction. Depressed cardiac contractile function was accompanied by a decrease in the myocardial functional reserve. A similar tendency was found in the restoration of systemic hemocirculation. Conclusion. Similar phase alterations in the myocardial contractile function and systemic hemodynamics developed in the postresuscitation period of acute myocardial infarction. Immediately after recovery, the parameters of systemic hemoperfusion increased due to the activation of the cardiac contractile function. The subsequent initial (3 – 60 min) decrease in the volumetric perfusion parameters was mainly caused by the depressed cardiac contractile function. Rhythm disturbances affected on-going circulatory insufficiency 4 - 5 hours after the recovery. The subsequent progressive decrease in the volumetric perfusion was caused by the extracardiac factors.

The review provides the current state and benefits of the computational fluid dynamics (CFD) applications in cardiovascular surgery. The review covers the milestones of CFD and novel achievements in the development of both numerical algorithms and computational models. Basic methods of flow modeling, including immersed-boundary methods and finite-difference methods, allow solving most core tasks, even using commercially available software packages. Future research prospects of CFD are associated with detailed modeling of the pathological processes affecting functional properties of medical devices, namely thrombus formation and embolism. However, current computational and mathematical systems are limited to address fully all these processes.

The article presents new insights into the left atrial mechanical function, its main components and remodeling mechanisms after pulmonary vein antrum isolation. Left atrium is a cardiac chamber that transports blood. Being a complex «organ» both in anatomical and functional terms, it responds to hemodynamic derangements, the impact of humoral and vegetative factors. Structural, mechanical and electrical remodeling of the left atrium play a key role in the arrhythmogenesis of atrial fibrillation, as well as in the mechanism of arrhythmia maintenance. Left atrial mechanical dysfunction following catheter ablation of atrial fibrillation significantly affects intracardiac hemodynamics, worsens patients' well-being, and increases the risk of thromboembolic complications both in the immediate and long-term postoperative period.

The review provides the current state and benefits of the computational fluid dynamics (CFD) applications in cardiovascular surgery. The review covers the milestones of CFD and novel achievements in the development of both numerical algorithms and computational models. Basic methods of flow modeling, including immersed-boundary methods and finite-difference methods, allow solving most core tasks, even using commercially available software packages. Future research prospects of CFD are associated with detailed modeling of the pathological processes affecting functional properties of medical devices, namely thrombus formation and embolism. However, current computational and mathematical systems are limited to address fully all these processes.

Portal venous gas in adults is associated with the development of abdominal compartment syndrome and can be used as a probable ultrasound diagnostic criterion. The case presents a patient aged 46 years after orthotopic heart transplant who developer abdominal syndrome in the intensive care unit postoperatively. Portal venous gas was a random finding during routine abdominal cavity ultrasound examination. Portal venous gas is a prognostically unfavorable sign. The early diagnosis can reduce the associated risk of death. Routine use of bedside ultrasound allows timely and accurately determining the presence of portal venous gas.