Surgical management of biatrial myxoma: case report

<p>Heart tumours account for approximately 0.2 % of all tumours: of these, approximately 75 % of all primary heart tumours are benign and 50 % of them are myxomas. Further, myxomas make up 0.0017 % of the general population of patients with cardiovascular disease. Biatrial myxomas, i.e. tumours in both the left and right atria, can be in the form of a ‘butterfly’ or a ‘dumbbell’, and account for &lt; 1 % of all cardiac myxomas. Here we describe the successful surgical management of a rare case of a large biatrial myxoma and concomitant atrioventricular valve insufficiency. Briefly, 2D transthoracic echocardiography findings included an end-diastolic volume of 90 ml, an end-systolic volume of 40 ml and a left ventricular ejection fraction of 55 % (according to Simpson). The fibrous ring of the mitral valve measured 36 mm with a regurgitation degree of 2 while the fibrous ring of the tricuspid valve was 42 mm in size and the regurgitation grade was 3. Lesion size in the cavity of the left and right atrium were 73 × 38 mm and 80 × 42 mm, respectively. These neoplasia were surgically removed under peripheral cardiopulmonary bypass, hypothermia and cold cardioplegia (Custodiol). The myxomas were accessed through the right atrium, according to Giradon and were resected without defragmentation. Next, mitral valve plasty using a soft support ring and annuloplasty of the tricuspid valve were performed according to de Vega. The duration of artificial circulation was 150 minutes and that of myocardial ischaemia was 100 minutes. The patient was extubated 11 hours after surgery, spent 22 hours in the intensive care unit and was discharged on the 14th day after surgery. Surgical resection of biatrial myxomas before the development of serious irreversible or life-threatening complications can provide rapid symptomatic relief in congestive heart failure.</p><p>Received 30 May 2021. Revised 22 August 2021. Accepted 23 August 2021.</p><p><strong>Funding: </strong>The study did not have sponsorship.</p><p><strong>Conflict of interest:</strong> Authors declare no conflict of interest.</p><p><strong>Contribution of the authors<br /> </strong>Literature review: T.A. Simonyan<br /> Drafting the article: T.A. Simonyan, I.M. Tsiskaridze<br /> Critical revision of the article: T.A. Simonyan, I.Yu. Farulova, E.A. Babajanyan<br /> Surgical treatment: I.I. Scopin, I.M. Tsiskaridze<br /> Final approval of the version to be published: T.A. Simonyan, I.I. Scopin, I.M. Tsiskaridze, I.Yu. Farulova, E.A. Babajanyan</p>

Immediate clinical results of the new biological support ring for correction of mitral insufficiency

Aim. To make the first clinical experience evaluation of the new biological closed support ring for mitral valve.Methods. 26 patients (16 men, 10 women, mean age 55 [49; 62] years) with dysplastic mitral insufficiency were implanted “NEORING” biological ring for the first time from March 2020 to June 2021. The etiological factor of the defect formation in all cases was the connective tissue dysplasia. The mean functional class of heart failure before surgery was 2 [2; 3] according to NYHA, the effective regurgitant orifice (ERO) was 0.4 [0.3; 0.5], vena contracta was 0.7 [0.6; 0.8]. Ten patients received rings of 28 mm diameter, ten patients – 30 mm, six patients – 32 mm.Results. No significant adverse events such as death from any causes, strokes, myocardial infarction, cardiac complications, bleeding, and return of regurgitation or failure of plastic surgery requiring reoperation, infective endocarditis after the intervention were observed. In two cases a permanent pacemaker was implanted due to sinus node dysfunction. At discharge all patients had no regurgitation (ERO 0), medium transvalvular gradient was 4.0 [3.0; 5.3] mm Hg. All the patients were assigned to NYHA functional class I heart failure after the surgery.Conclusion. New biological support ring “NEORING” (“NeoKor”, Kemerovo) use in the middle age group of patients showed high hemodynamic efficiency, the absence of specific complications in the early stages after the surgery. It is planned to expand the clinical material on the use of the biological ring, as well as to evaluate the long-term results in the format of a prospective, randomized trial and compare the new device with the existing ones.

Mathematical model of a ferromagnetic lubricant in the presence of a porous coating in the bearing structure

Based on the flow equation of a ferromagnetic liquid lubricant for a “thin layer”, the continuity equation and Darcy’s equation describing the flow of a lubricant in a porous body, an exact self-similar solution of wedge-shaped sliding support with a porous coating of the surface of the support ring is found, taking into account the dependence of the viscosity of the ferromagnetic lubricant and the permeability of the porous coating with the incomplete filling of the working gap. Analytical dependencies for the velocity and pressure fields in the lubricating and porous layer are obtained. Also, the main operating characteristics are determined load-bearing capacity and friction force. The numerical analysis of the theoretical results showed that the bearing capacity of the bearings can be increased by 8-12% in the range of the studied load-speed modes. At the same time, the coefficient of friction is reduced by 14-16%. To verify and confirm the effectiveness of the obtained theoretical models, an experimental study of a modified wedge-shaped sliding support on TP-22C, MS-20 oil and their mixture with various additives was carried out. As a result of theoretical and experimental studies, tribotechnical characteristics were determined that allow us to judge the presence of a long-term friction mode.

Design and Research of Double-Layered Cemented Carbide Novel High-Pressure Die

To improve the pressure-bearing capacity, a novel high-pressure die with cemented carbide as the first layer of supporting ring was designed. The novel high-pressure die increases the ultimate load-bearing capacity of the high-pressure die by increasing the pretension of the tungsten carbide cylinder. As the volume of the cemented carbide increases, the difficulty of manufacturing increases, therefore, to reduce the manufacturing difficulty of the cemented carbide supporting ring and reduce the shear stress of the supporting ring, the cemented carbide supporting ring is splited. And through reasonable derivation calculations, the calculation formula suitable for the optimal interference amount of the high-pressure die is obtained. The numerical analysis results show that: when a pressure of 6.2 GPa is applied on the inner wall of the tungsten carbide cylinder, high-pressure die mold that uses cemented carbide as the first layer of support ring (hereinafter referred to as double-layered cemented carbide novel high-pressure die) is lower than the ordinary high-pressure die in term of circumferential stress by 93.34%. In terms of von Mises stress by 21.4%, and term of maximum shear stress by 21.37%. The three principal stress images of the two molds are drawn, which proved that the double-layered hard alloy novel high-pressure die can fully exert the performance of the material and can withstand greater pressure.

HYDRODYNAMIC CALCULATION OF A WEDGE-SHAPED SYSTEM «SLIDER – GUIDE» OPERATING ON A COMPRESSIBLE LUBRICANT IN THE PRESENCE OF MELT ON THE SURFACE OF THE GUIDE

Recently, various methods have been used to ensure the hydrodynamic mode of lubrication, one of the methods is devoted to this scientific article. In the article, on the basis of the equation of motion of a compressible, truly viscous liquid for a "thin layer", the equations of state, the continuity equation, as well as the equations describing the profile of the molten contour of the surface of the support ring, an asymptotic and self-similar solution is found for the zero (without taking into account the melt) and the first (taking into account the melt) approximation, for determining the velocity field and pressure in the lubricating layer. For the profile of the molten contour and the pressure, the solution is found by the method of sequential approximation, for the extreme and non-extreme case. As a result, a refined mathematical calculation model of a wedge-shaped sliding support with a low-melting metal coating on the movable contact surface is developed, which compensates for the emergency lack of lubricant and provides a stable hydrodynamic lubrication mode, which allows determining the bearing capacity and friction force. As a result of numerical analysis, the obtained refined mathematical calculation model of a wedge-shaped sliding support with a low-melting metal coating on the surface of the support ring, taking into account the compressibility of the liquid lubricant and the coating melt, and experimental research, the effectiveness of the obtained complex of refined models that allow performing both pre-design evaluation and design engineering calculations, in a wide range of operational load-speed modes, as well as the mechanism and stages of transition to lubrication with metal sprays is established, providing an increase in the level of the main tribotechnical parameters and the resource of tribosystems.

Transcatheter methods of treatment of mitral valve pathology: current state of the problem

Во второй части обзора, посвященного транскатетерным методам лечения патологии митрального клапана (МК), рассматриваются вопросы транскатетерного протезирования МК (TMVI), в том числе: имплантация протеза в кальцинированное нативное фиброзное кольцо (valve-in-MAC), в ранее установленные хирургический биопротез (valve-in-valve) и опорное кольцо МК (valve-in-ring). Также кратко обсуждаются сравнительные преимущества и недостатки двух стратегий хирургического лечения - протезирования и пластической реконструкции – в контексте транскатетерной хирургии МК. Issues of transcatheter mitral valve (MV) implantation (TMVI) including implantation of a prosthesis into calcified native fibrous ring (valve-in- MAC), into previously implanted surgical bioprosthesis (valve-in-valve) and MV support ring (valve-in-ring) are considered in the second part of the review devoted to transcatheter methods of treatment of MV pathology. The comparative advantages and disadvantages of two surgical treatment strategies — prosthetics and plastic reconstruction — are also briefly discussed in the context of MV transcatheter surgery.

TRENDS FOR THE PROVISION OF SURVIVAL OF WHEELS OF MILITARY CAR EQUIPMENT

The article analyzes the viability of military vehicles from the effects of conventional damage (bullets, splinters), etc. When fired, a car that stops for a short time becomes an easy target and is destroyed. The presence of a tire pressure control system on the vehicles substantially increases the possibility of continued traffic. However, the opportunities of the mobility adjustment system is limited. The required survivability can only be ensured if special wheels are used. RunFlat (flat tire) is the common name for tireless tire technology. The RunFlat car wheel inserts allow you to continue driving after a tire has been punctured or descended, which can, for example, allow the machine to exit the firing zone. The essence of technology is to strengthen the sidewalls of tires. Hutchinson produces wheel inserts of two types - RODGARD and CRF. The RODGARD RunFlat (Rotary RunFlat) system is capable of providing deflated tires thanks to a special patented design. The CRF RunFlat (Static RunFlat) system is a wheel insert that is used as a single unit of the center of the wheel and tubeless tire. Сommon CSR (Conti Support Ring) system includes a metal ring that is fastened to the rim. The disadvantage of this system is that the support ring will only fit in the high profile wheels. The first cars wish RunFlat in the Armed Forces of Ukraine were KrAZ Cougar and Spartan cars. In turn, the main disadvantages of using wheels with RunFlat include, in addition to the much higher cost, the inability to use the tire after long distances. Airless tire (non-pneumatic) is an innovative development that is a one-piece wheel that can replace both the wheel disk and the pneumatic tire.The main advantage of this design is that the wheel does not require pumping, is not afraid of punctures, is resistant to damage and has a long service life. In this case, the weight of the wheel is almost twice as light, the life of such a wheel is two to three times longer, but the cost is more than twice the price of standard wheels. It is proved that the grip of the road surface in such tires is not inferior to traditional tires, and rolling resistance has decreased to hundreds. The Polaris Defense non-pneumatic wheels guarantee significantly better durability than standard tires and can withstand a 12.7mm bullet. The disadvantage of using non-pneumatic (airless) wheels is to create additional load on the suspension of the car due to their rigidity.

Determination of Stiffness Characteristics for WWER-1000 Support Components

Available approaches to computer justification of safe operation of reactor support components (RSC) are generally presented in the reports justifying RSC lifetime extension at Ukrainian NPPs. The experience of performing such calculations and analyzing the results indicates that there are issues to be improved. Thus, in particular, RSC stress-strain state is not analyzed for all force factors in the available calculations. It is typical for the reports on RSC lifetime extension justification that the strength assessment of the RSC is performed in an axisymmetric formulation (1/30). Meanwhile, a complex asymmetrical load from the main circulation pipelines is not considered, which affects RSC stress-strain state calculations as some stiffness characteristics (horizontal and torsional stiffness) cannot be determined correctly in a 1/30 axisymmetric formulation. The paper proposes a methodology for determining RSC stiffness in a complete formulation (without applying symmetry conditions), taking into account all geometric features and the interaction between individual structures and nodes of RSC. Thus, for each RSC (support ring, thrust ring, separating bellows), based on geometric features and types of connection to other components, stiffness to be determined to calculate the forces is defined (six for support ring and separating bellows and three for thrust ring respectively). Single loads in the form of forces and moments were imposed on the remote points connected to corresponding RSC surfaces to determine stiffness. This load made it possible to obtain the displacements and rotation angles of the corresponding remote points, which were used to calculate the stiffness characteristics. The described approach was first used in the calculations performed within justification of KhNPP Unit 1.