[Medinzh artificial cardiac valves].

The method of photochromic imaging was used to study the flow structure behind MEDINZh artificial cardiac valves. The flow structure behind three models of MEDINZh artificial cardiac valves (basic bicuspid model and two models under development) was studied experimentally under conditions of model physiological flow. Momentary flow rate profiles demonstrating the dynamics of the flow structure behind the valves were determined at various stages of the valve operation. The flow structure behind the artificial cardiac valves was studied in two perpendicular planes. The flow structure in front of the valves at the closing stage was also studied. The hemolysis level was experimentally determined under conditions of model physiological flow for the following six models of artificial cardiac valves: bicuspid valves CARBOMEDICS (USA), MEDINZh (Russia), MEDINZh N (Russia), and ROSCARDICS (Russia); disk valve MIKS (Russia); and a tricuspid valve (Germany).

[Experimental study of the hydrodynamics of polyurethane tricuspid heart valves].

Photochromic imaging, a new experimental hydrodynamic method, was used to study the flow structure behind polyurethane cardiac valve implants. The method is based on the sensitivity of model physiological medium to laser radiation. Color labels appear in 10-6 sec in the flow behind the valve under exposure to laser radiation. The motion of color labels in the flow is recorded with a high-speed camera. This makes it possible to determine the flow structure behind the valve. The flow structure behind three types of polyurethane cardiac valve implants was experimentally studied under conditions of model physiological flow. A polyurethane tricuspid valve with inner diameter 24 mm, a polyurethane tricuspid valve installed in a polyurethane tube, and a polyurethane tricuspid valve installed in a housing with Valsalva sinuses were studied. Complex flow structure was observed behind the cardiac valves. The complexity of its structure is explained by specific properties of valve construction. Flow rate profiles were determined for each moment of valve operation. These profiles show the dynamics of flow structure behind the valves.

[Study of functional parameters of prosthetic cardiac valves]. / Issledovaniia funktsional'nykh kharakteristik iskusstvennykh klapanov serdtsa.

A set of methods is offered, which enables to examine, with more details, the functional characteristics of the valves and to analyze them comparatively. The thus obtained functional characteristics make it possible to compare the valves and to select the best one prior to implantation. The results of a clinical study of the functioning of a valve, implanted by a new method involving a high-sensitivity solid sensor, are described.

[Experimental study of the hydrodynamics of modern artificial heart valves]. / Eksperimental'noe issledovanie gidrodinamiki sovremennykh iskusstvennykh klapanov serdtsa.

The paper presents the results of experimental studies of the hydrodynamics of currently available artificial cardiac valves (ACV). Photo chromatographic visualization was used to study the hydrodynamics of ACV. The hydrodynamic characteristics of a MIX discal valve (Russia) and a St. Jude two-leaflet one (USA), which have been clinically applied for more than 15 years, are presented.

[Experimental study of the relationship of the level of blood hemolysis and the design of artificial heart valves]. / Eksperimental'noe issledovanie zavisimosti urovnia gemoliza krovi ot konstruktsii iskusstvennykh klapanov serdtsa.

The paper deals with experimental studies into the level of hemolysis that accompanies the performance of artificial cardiac valves (ACV). The studies were conducted by two ways. The first study determined the level of hemolysis when artificial cardiac valves worked and donor blood performed. The second one was that a polymer was added to the model physiological fluid, the degree of hemolysis was determined by the changes occurring in the time of relaxation of elastic stress in the model fluid samples taken during tests. The experiments showed polyethylene oxide break-down to be the most accurately modelling process of hemolysis.

[An experimental study of acoustic noise of heart valve prostheses]. / Eksperimental'noe issledovanie akusticheskogo shuma iskusstvennykh klapanov serdtsa.

The paper deals with the acoustic noise that accompanies the work of artificial cardiac valves (ACV). The generation of a noise signal is a substantial disadvantage of ACV work after implantation. A highly sensitive solid-state probe was used to measure the noise signal. The disc ACVs Bjork-Shiley (USA), Omniscience" (Italy), MIKS, a basic (Russia), MIKS with an acoustic gap (Russia), and MIKS-3 were tested. The valves worked under model physiological flow. The disc valves of the MIKS series with an acoustic gap manufactured by ROSINVEST (Russia) were found to have the least noise.

[Experimental study of artificial disk heart valves]. / Eksperimental'noe issledovanie diskovykh iskusstvennykh klapanov serdtsa.

The paper provides the results of an experimental study of domestic artificial EMIKS disk cardiac valves during simulated pulsing flow. The operation valves was examined in the aortic position by photochromic visualization. The patterns of flow velocities beyond the valves during the whole operating cycle were obtained. The models of EMIKS valves at opening angles of 65 degrees and 80 degrees and the model with acoustic clearance in the design of a disk movement stopper were exploded. The findings may be useful for cardiac valves designers in evaluating the impact of designing features of a valve on its hydrodynamic characteristics.

[Two-leaflet artificial heart valve with the common turn axis for leaflets]. / Dvukhlepestkovyi iskusstvennyi klapan serdtsa s obshchei os'iu povorota lepestkov.

The paper describes the main results of calculations and studies of a basically new model of a two-leaflet valve which greatly differs from the St. Jude two-leaflet valves used in clinical setting. The main difference is that the two leaflets are fixed on one turn axis displaced from the axis of symmetry of the ring-carrying valve. The paper calculates the values of displacement (eccentricity) of the leaflet turn axis against the axis of symmetry of the ring-carrying valve. The new model of the valve is conventionally called Butterfly. The eccentricity of the new valve for the whole dimensional series is calculated by using experimental findings and the conditions for optimizing an effective valve opening. The strength of the axis of leaflet turning and attaching is also calculated. The results of experimental studies of the hydrodynamics of two models of the Butterfly valve by employing photochromic imaging are presented. The results of rapid filming were used to determine the time of closure and opening of the two models of valves.

[Experimental study of hydrodynamics of artificial heart valves]. / Eksperimental'noe issledovanie gidrodinamiki iskusstvennykh klapanov serdtsa.

The paper presents the results of examining the hydrodynamics of artificial heart valves (AHVs) manufactured in Russia and foreign countries. All the AHVs under study have been used in clinical practice for over 10 years and they are different in design. The hydrodynamics of AHVs was examined under static and pulsating flow through the valve. Photochromic imaging (PCI) was used for flow imaging. PCI is based on preparation of simulating blood (model physiological solution) in the medium, colour labels under laser radiation. The recording of colour label movement in the flow behind the valve using a speed camera makes it possible to follow flow hydrodynamics behind AHVs. The advantage of PCI over other methods is that the instant structure of flow behind the valve can be recorded just in the same section at any moment of an operating cycle. Based on the experimental data obtained by PCI, a procedure for comparative analysis of the hydrodynamic characteristics of AHVs was developed.

[Study of hydrodynamic characteristics of artificial heart valves by photochromic imaging]. / Issledovanie gidrodinamicheskikh kharakteristik iskusstvennykh klapanov serdtsa metodom fotokhromnoi vizualizatsii.

The paper deals with the hydrodynamics of artificial heart valves (AHVs) used in clinical practice. It reviews and analyzes the studies of AHV hydrodynamics, as well as the hydrodynamic beds which stimulate physiological flow through the valve. Photochronic imaging (PCI) is proposed for examination of AHV hydrodynamic characteristics under model physiological flow. The hydrodynamics of different AHVs was tested on the beds simulating blood flow through AHVs by employing PCI. PCI involved preparation of model photochronic solution that simulates blood, colour labels by using laser radiation. In the model photochronic solution, 10(-6)-10(-9)-sec laser radiation gave rise to linear colour labels whose movement was recorded by a speed camera in the flow behind the valve. The profiles of speed behind the valves, the dimensions of congestive areas, the positions of flow detachment and regurgitation flow were calculated by a speed shooting in different periods of valvular performance. PCI defined congestive areas behind the valves, the areas of closed circulations, the sizes of reversing flow areas and examined the time course of flow behind the valves as a whole. The paper is of interest for AHV designers and cardiac surgeons who apply various AHVs.

[A method of studying characteristics during modeling of blood flow in stenosed vessels]. / Metod issledovaniia kharakteristik pri modelirovanii techeniia krovi v stenozirovannykh sosudakh.

A new method of visualization employed in experimental hydrodynamics, namely a method of photochromic visualization (PCV), was used to examine the fluid flow in a tube with a diaphragm. The PCV is based on the design of colour markers in a model physiological solution exposed to laser radiation for 10(-6) to 10(-9) s. For the model flow in a tube with transitory Re numbers both qualitative and quantitative data were obtained. A round tube with a central hole in it and a diaphragm was chosen as an experimental stenosed vessel. The structure of the flow beyond the diaphragm was determined, with diameters of the central hole and Re numbers varying. It has been established that the level of tangential stresses increases as the diameter of the central hole in the diaphragm is diminished. It has been shown as well that the structure of the flow beyond the diaphragm undergoes alterations, provided medicamentous additions are introduced into the model physiological solution.