Mathematical modeling in assessing the risk of restenosis after carotid endarterectomy.

Carotid endarterectomy is the main way to combat atherosclerosis of the carotid arteries, which disrupts cerebral circulation. The generally accepted marker of atherogenesis risk are hemodynamic indices associated with near-wall shear stress. The purpose of the work is to conduct a comparative analysis of hemodynamic indices in various carotid bifurcation models. The influence of a virtual change in the geometric shape of the model in order to optimize hemodynamic indices is also being studied. On the basis of computed angiography data, carotid bifurcation models are constructed, in which critical zones of hemodynamic indices are built using computational fluid dynamics. A comparative analysis of the critical zones for different classes of models is carried out. Comparison of averaged indices for critical zones between 'normal' and post-operative groups gave more than 5-x worse results for the latter. The same results for the near-bifurcation parts of the zones give a 25% better result for postoperative models. Virtual 'removal' of insignificant plaques leads to a deterioration of the indices of up to 40% in the places of the plaque's former location. The described method makes it possible to build the indices critical zones and compare them for various types of models. A technique for virtual changing the shape of a vessel (virtual surgery) is proposed. The novelty of the approach lies in the use for comparative analysis both real vessel models and hypothetical 'improved' virtual ones, as well in the proposed division of post-operative model's critical zones into subzones of different genesis.

[Computer modeling of the area of carotid endarterectomy with patches of various forms]. / Sposob komp'yuternogo modelirovaniya zony klassicheskoi karotidnoi endarterektomii s primeneniem zaplat razlichnoi formy.

OBJECTIVE: To describe geometric models of carotid artery bifurcation and computer modeling of carotid endarterectomy (CEA) with patches of various configurations. MATERIAL AND METHODS: The method was demonstrated on a reconstructed model of intact vessel based on preoperative CT of the affected vessel in a certain patient. Blood flow is modeled by computational fluid dynamics using Doppler ultrasound data. Risk factors were assessed considering hemodynamic parameters of vascular wall associated with WSS. RESULTS: We studied hemodynamic results of 10 virtual CEA with patches of various shapes on the example of a reconstructed intact artery in a particular patient. Patch implantation is aimed at prevention of carotid artery narrowing since simple suture without a patch can reduce circumference of the artery by 4-5 mm. This result adversely affects blood flow. On the other hand, too wide a patch creates aneurysm-like deformation of internal carotid artery bulb. It is not optimal due to a large recirculation zone. It was found that patch width approximately equal to 3 mm ensures an optimal hemodynamic result. Deviations from this median value, both upward and downward, impair hemodynamics while the absence of a patch results the worst result. CONCLUSION: The proposed computer modeling technique is able to provide a personalized patch selection for CEA with low risk of restenosis in long-term follow-up period.

[Personalized brain revascularization: computer modeling of the reconstruction zone for carotid endarterectomy]. / Personifitsirovannaya revaskulyarizatsiya golovnogo mozga: metod komp'yuternogo modelirovaniya zony rekonstruktsii dlya provedeniya karotidnoi endarterektomii.

OBJECTIVE: To develop a technique of computer modeling of hemodynamics before conventional CEE. MATERIAL AND METHODS: Classical CEE is performed according to conventional patch technique. Duplex parameters of stenosis and blood flow velocity in the carotid arteries were analyzed by using of a linear transducer 7-7.5 MG (Acuson 128XP scanner, Acuson, USA). Multispiral computed tomography with angiography and subsequent processing of data using the Clear canvas software were performed to visualize the main geometric characteristics of the carotid arteries and features of atherosclerotic plaque. RESULTS: Blood flow hemodynamics is essential in the occurrence of postoperative restenosis. Therefore, computer simulation of blood flow using CFD (Computational Fluid Dynamics) methods based on particular patient's data makes it possible to assess localization of zones with high risk of restenosis. CFD approach implies construction of blood flow parameters at absolutely every point of the vessel considering geometric shape of the vessel and flow characteristics at the entrance and exit from the vessel. Pressure curves at the inlet and outlet are constructed using blood flow velocity curves. Pressure curves are subsequently used in the CFD model. The result of blood flow CFD modeling is non-stationary three-dimensional fields of pressure and velocity in the investigated area. Visual analysis of blood flow dynamics in these fields makes it possible to judge possible problem areas along the blood flow and on the inner wall of the vessel. DISCUSSION: Patch technique of classical CEE is characterized by great risk of parietal thrombosis and hyperproliferation of neointima that explains more frequent development of restenosis. Computer modeling is valuable to consider some important technical aspects in implementation of various surgical techniques for carotid artery reconstruction. CONCLUSION: This result demonstrates an importance of achieving the optimal ratio of the diameter of common, internal and external carotid arteries. Modification of patch based on computer simulation is required for these purposes.

[Computer-assisted simulation of haemodynamic parameters of carotid artery bifurcation after carotid endarterectomy]. / Komp'iuternoe modelirovanie gemodinamicheskikh pokazatelei v bifurkatsii sonnykh arterii posle karotidnoi éndarteréktomii.

Computer-aided simulation appropriately using the method of computational fluid dynamics (CFD) makes it possible to determine the elevated-risk zones of most probable formation of restenosis. The main idea of the method described in our article consists in a possibility of creating by the model of the geometrical shape of the vessel and characteristics of the flow at inlets and outlets the parameters of flow in each point of a vessel. The curves of velocity are used to create the curves of pressure at inlets and outlets, which are used in a CFD model. The resulting from CFD simulation of blood flow are nonstationary three-dimensional fields of pressure and velocity in the area under study. Visual examination of the dynamics of these fields makes it possible to judge about possible problem zones inside the area of flow and on the internal wall of the vessel. This article also presents a clinical case report illustrating the use of this technique.

[Deep electrothermal burns]. / Elektrotermicheskie glubokie ozhogi.

Five-year experience in the treatment of patients with severe electrotrauma are analysed. They accounted for 3.1% of the total number of patients with burns. The treatment of such patients in of a long duration and expensive. This trauma nonetheless leads to irreversible affection of the organism and disability. The main success is determined by early surgical treatment before the development of pyo-inflammatory processes in the injured tissues.

[Potassium levels in the blood in burns]. / Kaliemiia pri ozhogovoi bolezni.

The authors summarize and describe 18-years' experience in the management of patients with burns and determination of the potassium ion content in blood plasma, urine, erythrocytes, and burn exudate. They established that the abnormal potassium content is most hazardous during shock and toxemia and that the changes must be immediately corrected, otherwise complications occur in the course of the burn disease which may prove irreparable and cause death of the patient. The main principles of blood potassium+ control consisted in preventing loss of potassium through the wound and the kidneys and restoring its level by infusion. Early closure of burn wounds is an important moment in the control of potassium blood level disorders]

[Treatment of patients with thermal lesions with ointments on water-soluble base]. / Lechenie bol'nykh s termicheskimi porazheniiami maziami na vodorastvoromoi osnove.

Treatment of patients with thermal burns by ointments prepared on a water-soluble base (Dioxidine and Dioxicol) makes it possible to reduce the bacterial dissemination within a short time and prepare the wound for autodermoplasty which, in turn, reduces the danger of the development of infectious complications. In addition to a marked antimicrobial effect, the ointment possess high hydrophobic and hydrophilic properties and do not induce allergic reactions and side effects.

[Comparative evaluation of the cardiotropic effect of broncholytic agents]. / Sravnitel'naia otsenka kardiotropnogo éffekta bronkholiticheskikh sredstv.

The cardiotropic effect of broncholytic agents of different groups used for treatment of bronchial asthma was analyzed by using the method of determination of isoenzyme of MB creatine phosphokinase (CPK) and total CPK in the blood of the patients. A total of 125 biochemical assays on determination of CPK in the blood of the patients were made. The cardiotropic effects of three agents (adrenaline, novodrin, Berodual) were studied. Adrenomimetics adrenaline and isodrin (novodrin) were shown to increase significantly CPK activity. A combined agent Berodual insignificantly increased the activity of MB isoenzyme of CPK.

[Effect of ildamen on the heart conduction system in ischemic heart disease patients]. / Vliianie il'damena na provodiashchuiu sistemu serdtsa u bol'nykh ishemicheskoi bolezn'iu serdtsa.

Thirty-four patients with ischemic heart disease (IHD) were studied: 18 IHD patients with latent forms of disturbances of conductivity in the atrioventricular junction and sinus node sickness syndrome revealed at frequency stimulation of the heart; 16 patients with acute myocardial infarction complicated with the atrioventricular junction blockade of II and III degrees. Ildamen solution (4 mg) was slowly intravenously infused to all patients under study. Exerting the beta-stimulating effect, ildamen positively influences restoration of the disordered function of the pacemaker and conduction system of the heart: through immediate action on these systems and an increase of the coronary blood flow contributing to improvement of nutrition of the condition system of the heart.

[Treatment of frostbite]. / Lechenie otmorozhenii.

The article shows that treatment of frostbites in a special medium with controlled temperature and humidity makes the time of treatment shorter and prevents complications characteristic of such a trauma. The main purpose of such exposures of the injured areas is to achieve mummification and to make the operation as early as possible. The mummification of the soft tissues began within 5-8 days after trauma. Chemical necrectomy was possible on the 7th-9th days, followed by autodermoplasty on the 2nd day.

[Nitroglycerin pharmacodynamics in myocardial infarct]. / Farmakodinamika nitroglitserina pri infarkte miokarda.

The experience of treating 2,500 patients with acute myocardial infarction enabled the authors to prove a diverse character of nitroglycerin effect: it exerts a positive inotropic action on the myocardium, improves elastic properties of the myocardium, normalizes energy balance of the myocardium, influences the system of the blood aggregate state through contractile elements of platelets producing a hypocoagulatory effect.

[Effectiveness of biological dressings made of porcine skin in the treatment of burns]. / Effektivnost' biologicheskoi poviazki iz svinoi kozhi pri lechenii ozhogov.

The observation and estimation of results of treatment of 145 patients with burns have shown high efficiency of a biological dressing of porcine skin treated with chemical anticeptics (formaldehyde).

[Thyroid state and thyrotropic function of the pituitary gland in sportsmen during veloergometric exercise]. / Sostoianie shchitovidnoi zhelezy i tireotropnoi funktsii gipofiza u sortsmenov pri veloérgometricheskoi nagruzke.

The total and aerobic productivity, the content of the thyroid hormones, thyrotropin, lactate, and acid-base balance in the blood of 52 highly skilled sportsmen were studied in the process of veloergometric exercises of different intensity. It was shown that thyroxin and thyrotropin content increased and triiodothyronine concentration decreased in the blood plasma under the action of veloergometric exercises. A rise in cell metabolism and changes in the internal medium of the organism influence the alteration of the blood thyroid hormone and thyrotropin levels. Thyroid and hypophyseal thyrotropic functions depend to a certain degree on the exercise intensity and functional preparedness of the sportsmen.