[Comparative assessment of the state of the cornea after YAG-laser interventions on anterior segment structures]. / Sravnitel'naya otsenka sostoyaniya rogovitsy posle YAG-lazernykh vmeshatel'stv na strukturakh perednego segmenta glaza.

YAG-laser interventions are associated with the risk of complications, including in the cornea. PURPOSE: This study evaluates the condition of the cornea after laser discission (LD) of secondary cataracts (SC) and laser iridectomy (LI) using corneal confocal microscopy (CCM). MATERIAL AND METHODS: Group 1 included patients with the diagnosis "Pseudophakia, secondary cataract", they underwent LD of SC. Patients of group 1 were divided into 2 subgroups depending on the initial state of the cornea: group 1A included patients with unaltered corneas; group 1B - with changes in the corneas. Group 2 included patients diagnosed with angle-closure glaucoma (ACG) or suspected ACG, they underwent LI. CCM was performed on the Heidelberg HRT-III system. Laser treatment was performed using the Nd:YAG-laser LPULSA SYL-9000, λ=1.064 µm. RESULTS: Immediately after treatment, subgroup 1A exhibited singular hyperreflective deposits and negligible endothelial cell loss (ECL). After 1 month, CMM findings revealed no changes in this subgroup. In subgroup 1B, a post-LD reduction in endothelial cell density led to increased polymegathism, decreased pleomorphism, heightened endothelial cell nucleus reflectivity, and moderate hyperreflective deposits after 1 month. In the second group, significant hyperreflective deposits of various sizes, increased nucleus reflectivity, and notable endothelial cell density reduction were observed immediately and 1 month after LI. CONCLUSION: The results of this study show that the possibility of developing corneal complications after photo destructive laser interventions is to a certain extent related to the initial state of the cornea. The risk of developing corneal damage increases with decreasing distance between the cornea and the irradiated structure. An increase in the level of laser radiation energy and its total values also contributes to damage to the cornea, which is possible with dense secondary cataracts and thick irises.

[Comparative evaluation of transscleral laser exposure in anatomical experiment]. / Sravnitel'naya otsenka lazernogo transskleral'nogo vozdeistviya v usloviyakh anatomicheskogo eksperimenta.

PURPOSE: This study comparatively analyzed the morphology of eye tissues after laser exposure using the latest generation of transscleral laser techniques - micropulse transscleral cyclophotocoagulation (MP-TSCPC) and laser activation of scleral hydropermeability (LASH) - in an anatomical experiment. MATERIAL AND METHODS: The study used pulsed-periodic radiation of an Er-glass fiber laser (λ=1.56 µm) and radiation of a diode laser (λ=0.81 µm) in the micropulse mode. A comparative morphological evaluation of histological preparations of target scleral and ciliary body (CB) tissues was performed with the study of laser-induced changes occurring after LASH and MP-TSCPC. RESULTS: The study of histological preparations obtained after MP-TSCPC and LASH did not reveal any noticeable signs of an inflammatory reaction or significant destructive changes. There were no signs of pronounced coagulative changes in the form of disorganization of connective and muscle tissue in the exposure area. At the same time, MP-TSCPC was accompanied by thinning and discontinuity of the CB pigment epithelium in the projection of its flat part and expansion of the gaps between the anterior connective tissue fibers fixing the CB to the sclera, which is likely a factor contributing to uveoscleral outflow. After LASH, in the irradiated areas at the level of the outer layers of the sclera (¾ of its thickness) located in the projection of the flat part of the ciliary body, multiple slit-like cavities and enlargements (stretching) of interfiber spaces were revealed with simultaneous compaction of the inner part of the sclera (» of its thickness). CONCLUSION: The identified morphological changes may indicate certain differences in the mechanisms of intraocular pressure (IOP) reduction after MP-TSCPC and LASH. The results of this study suggest that the enhancement of uveoscleral outflow of intraocular fluid and the hypotensive effect after MP-TSCPC may be associated with laser-induced expansion of the interspaces between the anterior connective tissue fibers of the CB in the suprachoroidal space. With LASH, the possible mechanism of lowering IOP may be related rather to an increase in transscleral filtration due to the appearance of slit-like interfiber spaces in the sclera, caused by local contraction of scleral fibers in the area of laser exposure. The absence of pronounced destructive changes at the histological level indicates the gentle nature of both laser techniques and the possibility of expanding the indications for the use of LASH in the treatment of glaucoma, including at its earlier stages.

[Morphological evaluation of the results of laser activation of scleral hydropermeability in the treatment of glaucoma]. / Morfologicheskaya otsenka rezul'tatov operatsii lazernoi aktivatsii gidropronitsaemosti sklery v lechenii glaukomy.

PURPOSE: The study attempted to experimentally substantiate the possibility of using the laser activation of scleral hydropermeability (LASH) technique in glaucoma treatment by morphological evaluation of treatment outcomes. MATERIAL AND METHODS: The pulsed-periodic radiation from an Er-glass fiber laser (λ=1.56 µm) was used. The model experiment consisted of evaluating ultrafiltration of fluid through the tissues of human sclera autopsy specimen according to the original technique using neodymium chloride-based labeling agent and scanning electron microscopy. The clinical part of the study consisted of optical coherence tomography (OCT) and laser confocal microscopy of the sclera and conjunctiva (CMSC) performed in vivo immediately after laser treatment in the laser application sites in 5 patients (5 eyes) aged 57 to 68 years with uncompensated advanced (IIIb-c) stage of glaucoma who had previously underwent LASH surgery. RESULTS: Results of morphological evaluation after LASH revealed structural changes indicating increased transscleral ultrafiltration: increased intrastromal hyporeflective areas in the sclera, thinning of collagen fibers, formation of porous structures. Using an original technique involving neodymium chloride-based labeling agent and scanning electron microscopy, we were able to prove the enhancement of transscleral ultrafiltration. The results of the experiment were confirmed by in vivo OCT images of the sclera and CMSC performed in 5 patients with advanced glaucoma after LASH surgery, in which tissue decompaction in the laser-exposed areas was clearly visualized. CONCLUSION: The revealed structural changes indicate the possibility of reducing intraocular pressure after LASH by the means of forming scleral porous structures and increasing transscleral ultrafiltration. Experimentally selected optimal mode of laser exposure (0.66 W with total exposure time of 6 seconds) during LASH helps avoid gross destructive changes in the eye tissues, making the proposed intervention a sparing approach to the treatment of glaucoma.

[Clinical outcomes of laser activation of hydraulic permeability of the sclera in the treatment of advanced glaucoma]. / Klinicheskie rezul'taty lazernoi aktivatsii gidropronitsaemosti sklery v lechenii patsientov s dalekozashedshei stadiei glaukomy.

PURPOSE: This study evaluates the hypotensive effect and the outcomes of intravital morphological changes in the intervention site after laser activation of scleral hydro-permeability (LASH) by pulsed-periodic radiation from an Er-glass fiber laser (λ=1.56 µm) in patients with advanced glaucoma. MATERIAL AND METHODS: LASH surgery was performed in 19 patients (19 eyes) aged 48 to 73 years with uncompensated advanced stage (IIIb-c) glaucoma. In addition to standard methods of investigation, all patients were examined with optical coherence tomography (OCT) and laser confocal microscopy of sclera and conjunctiva (CMSC) at the laser treatment sites, and electronic tonography. RESULTS: The hypotensive effect after LASH in patients with advanced glaucoma was observed in 94.7% (n=18) of cases. The decrease in intraocular pressure (IOP) averaged 24.4% from baseline one month after intervention and 32.96% after six months of follow-up. In 15.7% (n=3) of cases, the recorded IOP decrease was insufficient as its target values were not achieved. However, in the vast majority of patients (n=16), the recorded IOP decrease corresponded to the target values and indicated compensation of the process. Results of complex morphological evaluation after LASH revealed structural changes indirectly indicating possible laser-induced influence on the processes of increased transscleral filtration and uveoscleral outflow. A high positive correlation dependence (r=0.848) was also revealed between the degree of IOP lowering and the increase in the coefficient of ease of aqueous humor outflow, attesting to the fact that IOP lowering was mainly due to the improvement of intraocular fluid outflow. CONCLUSION: The demonstrated efficacy of LASH technology indicates the possibility of its successful application as an independent method of IOP reduction in patients with advanced glaucoma.

[On studying the mechanisms and assessing the safety of Nd:YAG laser irradiation of the posterior lens capsule (experimental and clinical study)]. / K voprosu ob izuchenii mekhanizmov i otsenke bezopasnosti Nd:YAG-lazernoi destruktsii zadnei kapsuly khrustalika (eksperimental'no-klinicheskoe issledovanie).

YAG laser interventions are associated with the risk of complications, including corneal. PURPOSE: To study the mechanisms of laser destruction in exposing the posterior lens capsule (PLC) tissue to Nd:YAG laser irradiation, and to evaluate its side effects on the cornea. MATERIAL AND METHODS: The experiment involved 6 autopsy samples of human posterior lens capsule with different optical and mechanical properties, which were exposed to laser irradiation. We used the Nd:YAG ophthalmic laser LPULSA SYL-9000 Premio manufactured by «LightMed¼ (Taiwan/USA) and an experimental Nd:YAG laser system (1.064 µm). The following parameters were compared: the power of the incident radiation and radiation transmitted through the PLC, the mechanical stresses in the PLC tissue, the kinetic energy of the laser ablation products, and the pressure of gas bubbles during laser exposure in capsule samples of different densities. In the clinical part of the work, the negative effects of Nd:YAG laser on the cornea at different PLC densities were assessed using the endothelial microscope SP 3000P («Topcon¼, Japan). RESULTS: The experiment showed that in hard samples of PLC there are star-shaped point perforations with a diameter of 50±20 µm with partial rarefaction around the point defects. Damage to soft PLC samples in the form of large complete perforations was up to 200 µm in size. The temperature of laser irradiation necessary to achieve breakdown in soft PLC samples was 90 °C, in hard samples - 120 °C. The results of the experiment indicate that the final outcome - destruction of the PLC tissue - is safer to achieve not by increasing the energy, but by increasing the number of laser pulses. Clinical study results confirm a significant effect of the density of PLC on the values of laser energy and on the state of the cornea after laser intervention. CONCLUSION: The experimental data on the mechanisms of laser destruction of the lens capsule should contribute to the development of new and improvement of already known technologies aimed at reducing the risks associated with laser surgeries.

[Methods of studying deformation properties of ocular structures]. / Metody issledovaniya deformatsionnykh svoistv glaznykh struktur.

Studying ocular biomechanics presents apparent interest because of certain clinical situations when in vivo evaluation of mechanical properties can help with both diagnosis and treatment. This literature review considers the approaches to studying deformation properties of various ocular structures: dynamometric methods, elastotonometry, ophthalmic mechanography, photoelasticity method, ultrasound methods, analysis of pneumatic applanation of the cornea, atomic force microscopy, holographic interferometry, optical coherence elastography. Knowledge of the particularities of tissue deformation during examination with various methods can expand our understanding of the mechanisms of pathological changes in different structures of the organ of vision, which can help develop new methods of diagnosis and treatment.

[Transscleral laser therapy in the treatment of glaucoma]. / Lazernye transskleral'nye tekhnologii v lechenii glaukomy.

Nowadays glaucoma is one of the leading causes of irreversible blindness worldwide. The main goal in preservation of vision in glaucoma patients is reducing intraocular pressure (IOP), which is considered the main controlled risk factor for progression of glaucomatous optic neuropathy. The article discusses the effectiveness and safety of various transscleral laser technologies in the treatment of glaucoma. Modern transscleral laser technologies that affect the uveoscleral drainage and scleral hydro-permeability are less traumatic and more gentle making them promising in the treatment of patients with early stages of glaucoma, and not only in terminal glaucoma with pain syndrome resistant to conventional treatment ("last resort surgery").

[New biophotonics methods for improving efficiency and safety of laser modification of the fibrous tunic of the eye]. / Novye metody biofotoniki dlia povysheniia éffektivnosti i bezopasnosti lazernykh tekhnologii modifikatsii fibroznoi obolochki glaza.

The article describes a newly developed and tested diffractive optical element (DOE) that converts non-uniform radiation of the laser output into a homogeneous ring. The Gerchberg-Saxton algorithm is shown to be well suited for achieving annular intensity distribution. Testing this ring transducer on threshold-plasticity cornea demonstrated the reversibility of axisymmetric changes in the cornea. Atomic-Force microscopy of the area of maximum stresses in the corneal periphery showed no significant changes in the structure of the cornea when irradiated in the selected mode. Measurement of Young's modulus of the corneal surface areas after their irradiation also revealed no changes in the elastic properties, while examination of the corneal structure demonstrated the absence of significant structural changes in irradiated samples compared with intact ones.

Morphometry of skeletal muscle capillaries: the relationship between capillary ultrastructure and ageing in humans.

AIM: To determine whether the ultrastructure of the capillary system in human skeletal muscle changes during advancing senescence, we evaluated the compartmental and subcompartmental organization of capillaries from vastus lateralis muscle (VL) biopsies of 41 non-diseased persons aged 23-75 years. METHODS: From each VL biopsy, 38-40 randomly selected capillaries were assessed by transmission electron microscopy and subsequent morphometry with a newly established tablet-based image analysis technique. RESULTS: Quantification of the compartmental organization revealed most indicators of the capillary ultrastructure to be only non-significantly altered (P > 0.05) over age. However, the peri-capillary basement membrane (BM) was thicker in the older participants than in the younger ones (P ≤ 0.05). Regression analysis revealed a bipartite relationship between the two parameters: a homogenous slight increase in BM thickness up to the age of approximately 50 years was followed by a second phase with more scattered BM thickness values. In 44.5% of the capillary profiles, projections/filopodia of the pericytes (PCs) traversed the BM and invaded endothelial cells (ECs) visible as PC pegs in pale cytoplasm holes (EC sockets). Strikingly, PC pegs were often in proximity to the EC nucleus. In PC profiles, sockets were likewise detected in 14.2% of the capillaries. Within these PC sockets, cellular profiles were frequently seen, which could be assigned to EC filopodia, internal PC curling or PC-PC interactions. Quantification of the occurrence of peg-socket junctions revealed the proportions of empty EC sockets and empty PC sockets to increase (P ≤ 0.05) during ageing. CONCLUSION: Our investigation demonstrates advancing senescence to be associated with increase in BM thickness and loss of EC and PC filopodia length in skeletal muscle capillaries.

Capillary growth, ultrastructure remodelling and exercise training in skeletal muscle of essential hypertensive patients.

AIM: The aim was to elucidate whether essential hypertension is associated with altered capillary morphology and density and to what extent exercise training can normalize these parameters. METHODS: To investigate angiogenesis and capillary morphology in essential hypertension, muscle biopsies were obtained from m. vastus lateralis in subjects with essential hypertension (n = 10) and normotensive controls (n = 11) before and after 8 weeks of aerobic exercise training. Morphometry was performed after transmission electron microscopy, and protein levels of several angioregulatory factors were determined. RESULTS: At baseline, capillary density and capillary-to-fibre ratio were not different between the two groups. However, the hypertensive subjects had 9% lower capillary area (12.7 ± 0.4 vs. 13.9 ± 0.2 µm(2)) and tended to have thicker capillary basement membranes (399 ± 16 vs. 358 ± 13 nm; P = 0.094) than controls. Protein expression of vascular endothelial growth factor (VEGF), VEGF receptor-2 and thrombospondin-1 were similar in normotensive and hypertensive subjects, but tissue inhibitor of matrix metalloproteinase was 69% lower in the hypertensive group. After training, angiogenesis was evident by 15% increased capillary-to-fibre ratio in the hypertensive subjects only. Capillary area and capillary lumen area were increased by 7 and 15% in the hypertensive patients, whereas capillary basement membrane thickness was decreased by 17% (P < 0.05). VEGF expression after training was increased in both groups, whereas VEGF receptor-2 was decreased by 25% in the hypertensive patients(P < 0.05). CONCLUSION: Essential hypertension is associated with decreased lumen area and a tendency for increased basement membrane thickening in capillaries of skeletal muscle. Exercise training may improve the diffusion conditions in essential hypertension by altering capillary structure and capillary number.

Endogenous α-calcitonin-gene-related peptide promotes exercise-induced, physiological heart hypertrophy in mice.

AIM: It is unknown how the heart distinguishes various overloads, such as exercise or hypertension, causing either physiological or pathological hypertrophy. We hypothesize that alpha-calcitonin-gene-related peptide (αCGRP), known to be released from contracting skeletal muscles, is key at this remodelling. METHODS: The hypertrophic effect of αCGRP was measured in vitro (cultured cardiac myocytes) and in vivo (magnetic resonance imaging) in mice. Exercise performance was assessed by determination of maximum oxygen consumption and time to exhaustion. Cardiac phenotype was defined by transcriptional analysis, cardiac histology and morphometry. Finally, we measured spontaneous activity, body fat content, blood volume, haemoglobin mass and skeletal muscle capillarization and fibre composition. RESULTS: While αCGRP exposure yielded larger cultured cardiac myocytes, exercise-induced heart hypertrophy was completely abrogated by treatment with the peptide antagonist CGRP(8-37). Exercise performance was attenuated in αCGRP(-/-) mice or CGRP(8-37) treated wild-type mice but improved in animals with higher density of cardiac CGRP receptors (CLR-tg). Spontaneous activity, body fat content, blood volume, haemoglobin mass, muscle capillarization and fibre composition were unaffected, whereas heart index and ventricular myocyte volume were reduced in αCGRP(-/-) mice and elevated in CLR-tg. Transcriptional changes seen in αCGRP(-/-) (but not CLR-tg) hearts resembled maladaptive cardiac phenotype. CONCLUSIONS: Alpha-calcitonin-gene-related peptide released by skeletal muscles during exercise is a hitherto unrecognized effector directing the strained heart into physiological instead of pathological adaptation. Thus, αCGRP agonists might be beneficial in heart failure patients.

[Parameters of cardiac muscle repolarization on the electrocardiogram when changing anatomical and electric position of the heart].

While discussing the diagnostic value of the single channel electrocardiogram a set of theoretical considerations emerges inevitably, one of the most important among them is the question about dependence of the electrocardiogram parameters from the direction of electrical axis of heart. In other words, changes in what of electrocardiogram parameters are in fact liable to reflect pathological processes in myocardium, and what ones are determined by extracardiac factors, primarily by anatomic characteristics of patients. It is arguable that while analyzing electrocardiogram it is necessary to orient to such physiologically based informative indexes as ST segment displacement. Also, symmetry of the T wave shape is an important parameter which is independent of patients anatomic features. The results obtained are of interest for theoretical and applied aspects of the biophysics of the cardiac electric field.

[Computer simulation for localization and extensiveness of myocardial ischemia].

Features of genesis of the electrocardiosignal in conditions of the myocardial ischemia under changing localization and extensiveness of the ischemia foci, as well as an impact of this process on the repolarization parameters of the electrocardiosignal were investigated using a system for 3D simulation of the heart electrical activity. The model of the ventricles of the heart is a cellular automaton with the matrix about of 10(5) elements of the "Myocardium", "His", and "Purkinje" types and with prescribed rules of their interaction. In process of the study a developed earlier method of segmentation of the modeled ventricles was used. For estimating the contribution of the "ischemic" segments to the total signal of different leads of the electrocardiograms the previously suggested method of the partial curves was used. The ischemia foci were simulated by changing the characteristics of the transmembrane action potential in selected areas of the ventricles, such as the resting potential, transmembrane action potential amplitude, duration of the plateau phase, and the steepness of the final phase of rapid repolarization in accordance with literature data. Electrocardiosignals generated by the model were processed to obtain previously selected parameters, characterizing repolarization process. The influence of size and localization of the myocardial ischemia on the parameters obtained are examined, as well-as some hypotheses about their relation with an electrophysiological state of the heart muscle are discussed.

[The study of opportunity of aqueous humor filtration increase after nondestructive laser exposure of sclera in the site of pars plana projection (experimental study)].

Increase of scleral water permeability due to formation of porous structure after exposure of pulsed periodic radiation of erbium-glass optical fiber laser with wave length 1,56 pm was demonstrated in experimental study of cadaver human eyes in vitro and eyes of experimental animals (rabbits) in vivo. Simultaneous complex laser exposure of pars plana and ciliary processes results in summation of morphological changes that provide decrease of aqueous humor secretion, uveal drainage and extension of suprachoroid space. A base for new noninvasive technology of nondestructive laser exposure in glaucoma treatment is established.

[Electrocardiographic image of myocardial ischemia: real measurements and biophysical models. Part II].

By means of biophysical models of the heart electrical activity some alterations of the ST-T interval of an electrocardiogram were considered under changes of electrophysiological parameters of the cardiac muscle, characteristic for ischemia development. A computer program "The model of electrical activity of ischemic heart" developed in our Lab was used as a "Generator" for selection of model electrocardiosignals (ECS) when changing parameters of the transmembrane action potential (TAP) in "ischemic" area which was characterized in the model terms by its location and extent. The obvious development of ischemia was triggered by the deflection of TAP parameters from the reference values accepted for "conventional norm". For trapezoidal approximation of the TAP form chosen at the first stage of the work the following changed TAP parameters were used: (a) modification of duration of the horizontal plateau phase at the constant phase 3 slope; (b) a change in the amplitude of the plateau phase at the constant duration of this phase and all TAP; (c) modification in the slope of the fast repolarization phase at the constant duration of the plateau phase (in this case, the total duration of TAP also changes); (d) reduction in the duration of phase 2 at constant TAP duration, that, naturally, entails modification of the slope for the fast repolarization phase. We studied (out-of-scenarios developed before) separate effects of these parameters on changes of the T wave shape and the ST segment level. A number of new parameters for description of the changes observed in the ST-T interval pattern are offered and investigated. Computer experiments were performed using a system for 3D-modeling of the cardiac electrical activity. With the selected real and simulated ECSs a comparative study for diagnostic possibilities of some electrocardiographic criteria for detecting myocardial ischemia is carried out. The results obtained at this stage of work are of interest for identification and prediction of an electrophysiological state of the heart.

Terahertz and far-infrared synchrotron spectroscopy and global modeling of methyl mercaptan, CH3(32)SH.

In this work, terahertz and Fourier transform far-infrared (FTFIR) synchrotron spectra of methyl mercaptan, CH(3)SH, have been investigated in order to provide new laboratory information for enhanced observations of this species in interstellar molecular clouds and star-forming regions. Like its methanol cousin, methyl mercaptan has particularly rich spectra associated with its large-amplitude internal rotation that extend throughout the THz and FIR regions. We have recorded new spectra for CH(3)SH from 1.1-1.5 and 1.790-1.808 THz at the University of Cologne as well as high-resolution FTFIR synchrotron spectra from 50-550 cm(-1) at 0.001 cm(-1) resolution on the far-IR beam-line at the Canadian Light Source. Assignments are reported for rotational quantum numbers up to J ≈ 40 and K ≈ 15, and torsional states up to v(t) = 2 for the THz measurements and v(t) = 3 for the FTFIR observations. The THz and FTFIR measurements together with literature results have been combined in a global analysis of a dataset comprising a total of 1725 microwave and THz frequencies together with ~18000 FTFIR transitions, ranging up to v(t) = 2 and J(max) = 30 for MW∕THz and 40 for FTFIR. The global fit employs 78 torsion-rotation parameters and has achieved a weighted standard deviation of ~1.1. A prediction list (v(t) ≤ 2, J ≤ 45 and K ≤ 20) has been generated from the model giving essentially complete coverage of observable CH(3)(32)SH transitions within the bandwidths of major new astronomical facilities such as HIFI (Heterodyne Instrument for the Far Infrared) on the Herschel Space Observatory, ALMA (Atacama Large Millimeter Array), SOFIA (Stratospheric Observatory For Infrared Astronomy) and APEX (Atacama Pathfinder Experiment) to close to spectroscopic accuracy.

[Electrocardiographic image of myocardial ischemia: real measurements and biophysical models].

The peculiarities of the genesis of electrocardiosignal under myocardial ischemia in connection with an increase of its electrical inhomogeneity, as well as the electrophysiological mechanisms of morphological changes of the T wave of the electrocardiogram, including its "symmetrization" have been considered. A systemic approach to the problem has been used, which combines the mathematical, computer, and physiological modeling of the cardiac electrical activity with studies of the electric field of the human heart in terms of biophysical models. A database for the repolarization parameters of experimental electrocardiosignals ("Norm" and "Ischemia" samples) has been formed. The parameters of the ST-T interval and T wave, which could characterize the symmetry of the latter, and some additional properties of the repolarization process have been obtained. The methods of mathematical modeling were used also. Computer experiments were carried out on a system for 3-D modeling of the cardiac electrical activity at different structural levels of the object. By the results of preliminary analysis, the betaT index, which is calculated as the ratio of two maximum absolute values of the derivative of the cardiosignal at the left and right of the T wave apex, has been chosen as one of the main diagnostic markers of ischemia. There is reason to believe that the use of the betaT index allows one to recognize those deviations from the norm that are usually hidden from a physician in traditional ECG analysis. The ratios of repolarization intervals inside of the generalized QT interval have also appeared potentially informative. With the purpose to test and correct the hypotheses for conducting further investigations, some preliminary experiments on a low-resolution model for several alternatives of the degree, localization, and extensiveness of ischemia have been carried out. The results obtained at the first stage of the team-work are essential to the understanding of mechanisms of the genesis of an electrocardiographic image for myocardial ischemia and of interest for the biophysically sound development of new algorithms for computer cardiodiagnostics.

[Realization of biophysical models for the cardiac electrical activity].

Some principles for the realization of biophysical models of electrical activity of heart ventricles, presented by a double electrical layer along the surface of the electrically active myocardium and the boundary surfaces that divide model compartments with different electrophysiological properties, have been considered. The parameters of the model are the electrophysiological and anatomical characteristics of the heart, such as the geometry of ventricles and the His-Purkinje specialized conductive system, the velocity of depolarization propagation in the myocardium, the ratio of excitation velocities in "Myocardium", "His", and "Purkinje" model elements, the ,shape of transmembrane action potentials on boundary surfaces, the orientation of the own heart anatomical axes relative to the initial coordinate system, and others. The model has been included as a basic unit into a computer modeling system containing databases of simulated and real electrocardiosignals.

[Effect of sex on informative power of various electrocardiographical criteria of left ventricular hypertrophy in patients with excessive body mass].

Aim of the study was to analyze dependence of various voltage parameters of QRS complex on increase of left ventricular myocardial mass (LVMM) in samples of men and women with excessive body mass or obesity. We included data from 223 patients with excessive body mass and diagnosis of stage I - II arterial hypertension. ECG was registered in 12 standard leads. Left ventricular hypertrophy (LVH) was certified if according to echoCG data LVMM exceeded 125 g/m2 in men and 110 g/m2 in women. Depending on sex and presence of LVH all patients were divided into 4 groups: M1 (men with LVH, n=74), M2 (men without LVH, n=74), W1 (women with LVH, n=55), anb W2 (women without LVH, n=20). We analyzed amplitudes of all waves of the QRS complex as well as Sokolow-Lyons voltage parameters and the Cornell index. The following intergroup differences were most significant: between groups M1 and M2 - in amplitudes of S waves in chest leads V3, V4; between groups W1 and W2 - in amplitudes of R-waves in limb leads I and aVL, and amplitudes of S-waves in lead III. Increases of the Cornell voltage index were observed both in men and women with LVH. The following criteria had greatest sensitivity at 95% specificity: in men - SV4 > 1,1 mV (34%) and RaVL+SV3 > 2,3 mV (32%); in women - RaVL > 0,8 mV (56%) and RI+SIII > 1,5 mV (56%). Informative power of electrocardiographical diagnosis of LVH can be augmented by the use of different voltage criteria in groups of men and women. In men most informative are chest leads (SV1 - V3, RaVL) while in women - limb leads (RI, RaVL, and SIII). The use of combination parameters RaVL+SV3 > 2,3 mV (in men) and RI+SIII > 1,5 mV (in women) allows to augment sensitivity with unchanged specificity. In patients with excessive body mass voltage the Sokolow-Lyons criterion is not informative. Most significant component of the Cornell voltage criterion in groups of men with excessive body mass is amplitude of SV3, in groups of women - amplitude of RaVL.