Bulk ferromagnetism in cleavable van der Waals telluride NbFeTe2

A van der Waals telluride, NbFeTe2, has been synthesized using chemical vapor transport reactions. The optimized synthetic conditions yield high-quality single crystals with a novel monoclinic crystal structure. Monoclinic NbFeTe2 demonstrates a (100) cleavage plane, bulk ferromagnetism below 87 K, and a metallic ground state-the necessary prerequisites for needed spintronics technologies.

Understanding Complex Interplay among Different Instabilities in Multiferroic BiMn7O12 Using 57Fe Probe Mössbauer Spectroscopy

Here, we report the results of a Mössbauer study on hyperfine electrical and magnetic interactions in quadruple perovskite BiMn7O12 doped with 57Fe probes. Measurements were performed in the temperature range of 10 K < T < 670 K, wherein BiMn6.9657Fe0.04O12 undergoes a cascade of structural (T1 ≈ 590 K, T2 ≈ 442 K, and T3 ≈ 240 K) and magnetic (TN1 ≈ 57 K, TN2 ≈ 50 K, and TN3 ≈ 24 K) phase transitions. The analysis of the electric field gradient (EFG) parameters, including the dipole contribution from Bi3+ ions, confirmed the presence of the local dipole moments pBi, which are randomly oriented in the paraelectric cubic phase (T > T1). The unusual behavior of the parameters of hyperfine interactions between T1 and T2 was attributed to the dynamic Jahn-Teller effect that leads to the softening of the orbital mode of Mn3+ ions. The parameters of the hyperfine interactions of 57Fe in the phases with non-zero spontaneous electrical polarization (Ps), including the P1 ↔ Im transition at T3, were analyzed. On the basis of the structural data and the quadrupole splitting Δ(T) derived from the 57Fe Mössbauer spectra, the algorithm, based on the Born effective charge model, is proposed to describe Ps(T) dependence. The Ps(T) dependence around the Im ↔ I2/m phase transition at T2 is analyzed using the effective field approach. Possible reasons for the complex relaxation behavior of the spectra in the magnetically ordered states (T < TN1) are also discussed.

Layered van der Waals Chalcogenides FeAl2Se4, MnAl2S4, and MnAl2Se4: Atomically Thin Triangular Arrangement of Transition-Metal Atoms

Layered van der Waals (vdW) chalcogenides of 3d transition metals are a rich source of two-dimensional (2D) nanomaterials, in which atomically thin layers with the terminating chalcogen atoms exhibit promising functionality for novel spintronic devices. Here, we report on the synthesis, crystal growth, and magnetic properties of FeAl₂Se₄, MnAl₂S₄, and MnAl₂Se₄ ternary chalcogenides. Crystal structures are probed by powder X-ray diffraction, Mössbauer spectroscopy, and high-resolution transmission electron microscopy. We improve the structural models of FeAl₂Se₄ and MnAl₂S₄ and show that isostructural MnAl₂S₄ and MnAl₂Se₄ crystallize in the centrosymmetric R3̅̅m space group. In the crystal structure, transition metal and Al atoms mutually occupy the octahedral and tetrahedral voids of four close-packing chalcogen layers terminated by vdW gaps. The transition-metal atoms form a triangular arrangement inside the close-packing layers. As a result, FeAl₂Se₄ and MnAl₂S₄ show no long-range magnetic order in the studied temperature range. In the paramagnetic state, Fe and Mn possess effective magnetic moments of 4.99(2) and 5.405(6) μ_B, respectively. Furthermore, FeAl₂Se₄ enters a frozen spin-disordered state below 12 K.

Controlled Reduction of Sn4+ in the Complex Iodide Cs2SnI6 with Metallic Gallium

Metal gallium as a low-melting solid was applied in a mixture with elemental iodine to substitute tin(IV) in a promising light-harvesting phase of Cs₂SnI₆ by a reactive sintering method. The reducing power of gallium was applied to influence the optoelectronic properties of the Cs₂SnI₆ phase via partial reduction of tin(IV) and, very likely, substitute partially Sn⁴⁺ by Ga³⁺. The reduction of Sn⁴⁺ to Sn²⁺ in the Cs₂SnI₆ phase contributes to the switching from p-type conductivity to n-type, thereby improving the total concentration and mobility of negative-charge carriers. The phase composition of the samples obtained was studied by X-ray diffraction (XRD) and ¹¹⁹Sn Mössbauer spectroscopy (MS). It is shown that the excess of metal gallium in a reaction melt leads to the two-phase product containing Cs₂SnI₆ with Sn⁴⁺ and β-CsSnI₃ with Sn²⁺. UV-visible absorption spectroscopy shows a high absorption coefficient of the composite material.

[Realization of medical and medical psychological rehabilitation in sanatorium-resort organizations of Ministry of Defence of the Russian Federation]

Current conditions of military service demand higher standards of servicemen health status, whose professional activity in extreme combat conditions is accompanied by the impact of many adverse environmental factors on the body. One of the priority tasks of medical service of Armed Forces of the Russian Federation in 2023 yr. is to improve the system of curative and preventive measures in medical and medical psychological rehabilitation to recover health and increase working capacity of servicemen. The article includes an overview of measures given to servicemen for medical and medical psychological rehabilitation in sanatorium-resort organizations of Ministry of Defence in the Russian Federation for the period from 2013 to 2022 yrs.

Correction: High-coercivity hexaferrite ceramics featuring sub-terahertz ferromagnetic resonance

Correction for 'High-coercivity hexaferrite ceramics featuring sub-terahertz ferromagnetic resonance' by Evgeny A. Gorbachev et al., Mater. Horiz., 2022, 9, 1264-1272, DOI: https://doi.org/10.1039/D1MH01797G.

High-coercivity hexaferrite ceramics featuring sub-terahertz ferromagnetic resonance

Herein, we demonstrate for the first time compact ferrite ceramics with giant coercivity. The materials are manufactured via sintering single-domain Sr_0.67Ca_0.33Fe₈Al₄O₁₉ particles synthesized by a citrate-nitrate auto-combustion method. The obtained ceramics show coercivities up to 22.5 kOe and natural ferromagnetic resonance frequencies (NFMR) in a sub-THz range of 160-282 GHz. At a maximum density of 95%, the sample displays coercivity of 18.5 kOe, which is the highest value among dense ferrite materials reported so far. In addition, we report an unusual blueshift of the NFMR frequency from 160 to 200 GHz, which occurs during material sintering.

Magnetic structures of Fe32+δGe33As2 and Fe32+δ'Ge35-xPx intermetallic compounds: a neutron diffraction and 57Fe Mössbauer spectroscopy study

Fe_32+δGe₃₃As₂ and Fe_32+δ'Ge_35-xP_x are quasi-binary intermetallic compounds that possess a rare variant of intergrowth-type crystal structure, which is a combination of the column shaped Co₂Al₅ and MgFe₆Ge₆ structure type blocks. The compounds are antiferromagnets with the Néel temperatures around 125 K. Neutron powder diffraction experiments on the samples with δ≈ 0.1, δ'≈ 0.5 and x≈ 3 reveal commensurate magnetic ordering of low symmetry in both compounds and a non-monotonic change in the intensities of magnetic reflections. On the other hand, temperature dependence of the hyperfine fields obtained from ⁵⁷Fe Mössbauer spectroscopy indicates a gradual, monotonic increase in local magnetic fields upon cooling. We interpret these results as a spin reorientation within the Co₂Al₅-type block of the crystal structure, with the possible formation of a non-collinear magnetic order at low temperatures. Between the compounds, the reorientation occurs at significantly different temperatures, however the resulting magnetic structures themselves are similar as well as the average values of the magnetic moments and the hyperfine fields.

Endohedral Cluster Superconductors in the Mo-Ga-Sn System Explored by the Joint Flux Technique

Endohedral Ga cluster compounds feature nontrivial superconducting states including the two-gap superconductivity similar in nature to MgB₂. We use the joint flux synthetic technique to introduce Sn into the Ga matrix and tune the valence electron count in the two new endohedral cluster superconductors Mo₈Ga_41-xSn_x and Mo₄Ga_21-x-δSn_x with critical temperatures of T_c = 8.7 and 5.85 K, respectively. While the former compound is a derivative of the previously known Mo₈Ga₄₁ superconductor, where Sn atoms are enclosed inside the Sn@Ga₆ octahedral clusters, the latter is a new architecture built upon Mo@Ga₉Sn clusters, Ga@Ga₁₂ cuboctahedra, and Sn₄ squares. We show that this novel Mo₄Ga_21-x-δSn_x superconductor features strong electron-phonon coupling with the large ratio of 2Δ(0)/(k_BT_c) = 4.1 similar to that of the Mo₈Ga₄₁ superconductor with the closely related crystal structure.

[The role of the vascular surgeon in improvement of organization of dialysis help]

Analysed herein are one-year results of formation of arteriovenous fistulas in 109 patients with end-stage chronic renal failure, as well as therapeutic decision-making after angiosurgical counselling of 144 patients presenting with 'problem' permanent vascular accesses. The counselling and formation of arteriovenous fistulas were carried out in conditions of interdepartmental collaboration between outpatient centres dealing with haemodialysis and vascular surgeons specialized in ultrasound mapping of peripheral vessels and performing different variants of arteriovenous fistulas. The angiosurgical care was as close to the patient as possible. Of the 109 operated patients, primary arteriovenous fistulas were made in 46 (42.2%) cases, secondary AVF - in 27 (24.8%) cases, and reconstruction of AVF - in 36 (33.0%) cases. Of the 144 patients with 'problem' permanent vascular assesses, correction of arteriovenous fistulas turned out impossible in 13 (9.1%). In the remaining 131 (90.9%) patients there was a possibility of different variants of open reconstruction of arteriovenous fistulas or performing angioplasty. Active policy of vascular surgeons in interdepartmental collaboration with nephrologists made it possible to bridge over the difficulties of patients routing which resulted in reduction of the terms of formation of arteriovenous fistulas by 2 months. Preventive arteriovenous fistulas were carried out in 17.4% of cases of primary permanent vascular assesses. During a year after formation of permanent vascular accesses, the number of patients with vascular catheters in ambulatory centres decreased from 22 to 17%. These positive changes in organization of the dialysis treatment made it possible to reduce the risks of infectious complications, to obtain adequate blood flow characteristics for haemodialysis procedures, as well as to decrease financial expenses and labour costs for AVF care.

Pre-treatment condition effects on blood pressure and heart rate variability change in patients with arterial hypertension on therapy

AIM

To study the relationship of the initial clinical and functional state of patients with arterial hypertension (AH) with the dynamics of daily indices of blood pressure (BP) and sinus rhythm on antihypertensive therapy.

MATERIALS AND METHODS

38 patients were examined (general clinical examination, electrocardiography, echocardiography, daily bifunctional monitoring with the determination of weighted average rhythmogram variations - WARV, clinical and biochemical analysis of blood, glycated hemoglobin, thyroid hormones) and distribyted according to the use of hypotensive drugs of main classes and combined therapy AH. Dynamic monitoring of the effectiveness of treatment was carried out (after 2-4 weeks, then every 1-2 months), clinically and with bifunctional monitoring, correction of therapy. The observation period was 8 months.

RESULTS

By the end of the study, 27 patients had target blood pressure, significant decrease in systolic / diastolic blood pressure (10/5 mm Hg and more) occurred in 30 patients. A correlation was found between the effectiveness of antihypertensive treatment and the initial clinical and instrumental parameters of patients: age, heart size (including left ventricular hypertrophy - LVH), thyroid stimulating blood hormone (TSH) level and fasting blood glucose (within normal limits). The level of WARV also correlated with these indicators and was significantly higher in patients who achieved a significant reduction in blood pressure. No significant dynamics of WARV was detected. No relationship between baseline blood pressure with WARV and their changes were identified. The connection of the myocardial mass index with the level of TSH and glycated hemoglobin was demostrated.

CONCLUSION

The WARV reflects the severity of organic heart changes associated with age, disease duration, metabolic profile, LVH - heart damage as a target organ in AH, but is not suitable for analyzing its functional changes within one stage of the disease.

New Fe-based layered telluride Fe3-δAs1-yTe2: synthesis, crystal structure and physical properties

A new ternary telluride, Fe_3-δAs_1-yTe₂, was synthesized from elements at 600 °C. It crystallizes in the hexagonal P6₃/mmc space group with the unit cell parameters a = 3.85091(9) Å and c = 17.1367(4) Å for δ = 0.3 and y = 0.04. Its layered crystal structure contains partially occupied intralayer and interlayer Fe positions, which give rise to significant nonstoichiometry: Fe_3-δAs_1-yTe₂ was found to possess the homogeneity range of 0.25 < δ < 0.45 and y = 0.04. Regions of local vacancy ordering alternate with regions of randomly distributed vacancies, so that the ordering of Fe atoms and vacancies is not complete in the average structure. Clear evidence of the magnetic phase transition is obtained by thermodynamic measurements, Mössbauer spectroscopy, and neutron powder diffraction. Magnetic susceptibility measurements reveal weak ferromagnetism below T_C = 123 K with a net moment of M_S∼ 0.1μ_B/Fe at T = 2 K. This transition is confirmed by differential scanning calorimetry. Additionally, neutron powder diffraction indicates the onset of a complex AFM-like magnetic ordering below 100 K.

Spin-Driven Multiferroic Properties of PbMn7O12 Perovskite

We synthesize PbMn7O12 perovskite under high-pressure (6 GPa) and high-temperature (1373 K) conditions and investigate its structural, magnetic, dielectric, and ferroelectric properties. We find that PbMn7O12 exhibits rich physical properties from interplay among charge, orbital, and spin degrees of freedom and rich structural properties. PbMn7O12 crystallizes in space group R3̅ near room temperature and shows a structural phase transition at TCO = 397 K to a cubic structure in space group Im3̅; the Im3̅-to-R3̅ transition is associated with charge ordering. Below TOO = 294 K, a structural modulation transition associated with orbital ordering takes place. There are two magnetic transitions with Néel temperatures of TN1 = 83 K and TN2 = 77 K and probably a lock-in transition at TN3 = 43 K (on cooling). There is huge hysteresis on specific heat (between ∼37 and 65 K at 0 Oe), dielectric constant (between ∼20 and 70 K at 0 Oe), and dc and ac magnetic susceptibilities around the lock-in transition. Sharp dielectric constant, dielectric loss, and pyroelectric current anomalies are observed at TN2, indicating that electric polarization is developed at this magnetic transition, and PbMn7O12 perovskite is a spin-driven multiferroic. Polarization of PbMn7O12 is measured to be ∼4 μC/m(2). Field-induced transitions are detected at ∼63 and ∼170 kOe at 1.6-2 K; similar high-magnetic field properties are also found for CdMn7O12, CaMn7O12, and SrMn7O12. PbMn7O12 exhibits a quite small magnetodielectric effect, reaching approximately -1.3 to -1.7% at 10 K and 90 kOe.

High-pressure synthesis, crystal structure and magnetic properties of TlCrO3 perovskite

TlMO(3) perovskites (M(3+) = transition metals) are exceptional members of trivalent perovskite families because of the strong covalency of Tl(3+)-O bonds. Here we report on the synthesis, crystal structure and properties of TlCrO(3) investigated by Mössbauer spectroscopy, specific heat, dc/ac magnetization and dielectric measurements. TlCrO(3) perovskite is prepared under high pressure (6 GPa) and high temperature (1500 K) conditions. The crystal structure of TlCrO(3) is refined using synchrotron X-ray powder diffraction data: space group Pnma (no. 62), Z = 4 and lattice parameters a = 5.40318(1) Å, b = 7.64699(1) Å and c = 5.30196(1) Å at 293 K. No structural phase transitions are found between 5 and 300 K. TlCrO(3) crystallizes in the GdFeO(3)-type structure similar to other members of the perovskite chromite family, ACrO(3) (A(3+) = Sc, In, Y and La-Lu). The unit cell volume and Cr-O-Cr bond angles of TlCrO(3) are close to those of DyCrO(3); however, the Néel temperature of TlCrO(3) (TN≈ 89 K) is much smaller than that of DyCrO(3) and close to that of InCrO(3). Isothermal magnetization studies show that TlCrO(3) is a fully compensated antiferromagnet similar to ScCrO(3) and InCrO(3), but different from RCrO(3) (R(3+) = Y and La-Lu). Ac and dc magnetization measurements with a fine step of 0.2 K reveal the existence of two Néel temperatures with very close values at T(N2) = 87.0 K and T(N1) = 89.3 K. Magnetic anomalies near T(N2 )are suppressed by static magnetic fields and by 5% iron doping.

Structure and cation distribution in perovskites with small cations at the A site: the case of ScCoO3

We synthesize ScCoO3 perovskite and its solid solutions, ScCo1-x Fe x O3 and ScCo1-x Cr x O3, under high pressure (6 GPa) and high temperature (1570 K) conditions. We find noticeable shifts from the stoichiometric compositions, expressed as (Sc1-xMx )MO3 with x = 0.05-0.11 and M = Co, (Co, Fe) and (Co, Cr). The crystal structure of (Sc0.95Co0.05)CoO3 is refined using synchrotron x-ray powder diffraction data: space group Pnma (No. 62), Z = 4 and lattice parameters a = 5.26766(1) Å, b = 7.14027(2) Å and c = 4.92231(1) Å. (Sc0.95Co0.05)CoO3 crystallizes in the GdFeO3-type structure similar to other members of the perovskite cobaltite family, ACoO3 (A3+ = Y and Pr-Lu). There is evidence that (Sc0.95Co0.05)CoO3 has non-magnetic low-spin Co3+ ions at the B site and paramagnetic high-spin Co3+ ions at the A site. In the iron-doped samples (Sc1-xMx )MO3 with M = (Co, Fe), Fe3+ ions have a strong preference to occupy the A site of such perovskites at small doping levels.

Perovskite-structure TlMnO₃: a new manganite with new properties

We synthesize a new member of the AMnO3 perovskite manganite family (where A is a trivalent cation)--thallium manganite, TlMnO3--under high-pressure (6 GPa) and high-temperature (1500 K) conditions and show that the structural and magnetic properties are distinct from those of all other AMnO3 manganites. The crystal structure of TlMnO3 is solved and refined using single-crystal X-ray diffraction data. We obtain a triclinically distorted structure with space group P1̅ (No. 2), Z = 4, and lattice parameters a = 5.4248(2) Å, b = 7.9403(2) Å, c = 5.28650(10) Å, α = 87.8200(10)°, β = 86.9440(10)°, and γ = 89.3130(10)° at 293 K. There are four crystallographic Mn sites in TlMnO3 forming two groups based on the degree of their Jahn-Teller distortions. Physical properties of insulating TlMnO3 are investigated with Mössbauer spectroscopy and resistivity, specific heat, and magnetization measurements. The orbital ordering, which persists to the decomposition temperature of 820 K, suggests A-type antiferromagnetic ordering with the ferromagnetic planes along the [-101] direction, consistent with the measured collinear antiferromagnetism below the Néel temperature of 92 K. Hybrid density functional calculations are consistent with the experimentally identified structure, insulating ground state, and suggested magnetism, and show that the low symmetry originates from the strongly Jahn-Teller distorted Mn(3+) ions combined with the strong covalency of the Tl(3+)-O bonds.

[Diagnosis and treatment of allergic rhinitis aggravated by respiratory tract infection]

The objective of the present paper was to propose an optimal scope of diagnostic studies for the patients complaining of rhinitis symptoms for the early detection of allergic rhinitis, including a differential diagnosis with associated respiratory tract infections. A comprehensive treatment is offered including the use of vasoconstrictors and antihistamines, eliminationand immunocorrectivetherapy with Ribomunyl.

[Changes in ST segment on ECG of hypertensive patients]

AIM

To evaluate ST depression in hypertensive patients with electrocardiographic signs of left ventricular hypertrophy (LVH), correlation of ST segment changes with heart rate (HR) and blood pressure (BP) during Holter monitoring (HM) and bi-functional ECG and BP monitoring (BFM), and to compare ST depression and local left ventricular contractility during stress-echocardiography in hypertensive patients with unaffected coronary arteries according to the data of coronary angiography.

MATERIAL AND METHODS

We examined 344 hypertensive patients without clinical signs of ischemic heart disease. Correlation between ST segment depression and ECG signs of LVH was evaluated in 192 patients. 180 patients underwent HM, 122--BFM and 30 hypertensive patients with normal coronary arteries according to the data of coronary angiography underwent stress-echocardiography.

RESULTS

According to the data of 12 lead ECG 40 cases of ST depression were found, with LVH signs in 26 (65%) of these patients. During HM in 34 of 180 patients 2 types of ST depression were found: type 1--short periods of transient ST depression without persistent ST depression was fond in 8 patients; type 2--persistent ST depression more than 1 mm during the whole time of recording--in 26 patients. In 7 of 8 cases of type 1 and in 5 of 26 cases of type 2 ST depression had rhythm-dependent character. During BFM in 9 cases ST depression during HR or BP increase was found. In 2 cases ST depression during BP increase was unrelated to HR increase which may be consequence of systolic myocardial strain syndrome. In 7 of 30 hypertensive patients with normal coronary arteries and without local myocardial contractility disturbances according to the data of stress-echocardiography positive criteria of ischemia were found.

CONCLUSION

The cause of ST segment depression in hypertensive patients more often are secondary disturbances of repolarizaion processes related with LVH development. In some cases such patients during HM show rhythm-dependent valuable ST depressions. In BFM cases of left ventricular myocardial strain syndrome are found, similar cases are also seen in stress-echocardiography. However, in some cases one fails to define the reason of ST changes even approximately. One of the factors leading to disturbances of repolarization processes in hypertensive patients may be disturbances of microcirculation at the level of prearteriols and capillaries.

[Heart rate variability dynamics during treatment of arterial hypertension]

Investigation of the dynamics of heart rate variability (HRV) in anti-hypertension therapy can facilitate the evaluation of the effectiveness of treatment.

AIM OF INVESTIGATION

to compare anti-hypertension effect of monotherapy with nebivolol and dilatrend with dynamics of HRV and the estimation of the state of patients with mild arterial hypertension (AH) and metabolic syndrome (MS).

MATERIAL AND METHODS

HRV was studied in 42 patients with mild AH and MS at the age of 32-60. Eighteen of them were treated with 5 mg of nebivolol during 24 weeks, and twenty-four with 25-50 mg of dilatrend during 16 weeks. All the patients were subjected to 24-hour ECG monitoring with analysis of HRV and arterial pressure (AP) before and after treatment. The main feature of HRV analysis was investigation of dependence of sinus arrhythmia on the mean value of heart rate (HR) RESULTS: With nebivolol treatment AP decreased in 11 patients, HRV became better in 9 patients. 7 cases manifested coincidence of AP reduction and HRV improvement. In 6 cases out of 7 when AP did not decrease, HRV did not change. Worsened HRV was observed in 3 cases: in one case with growing AP and in 2 cases with decreasing AP. All the patients, except one, regarded their state as improved. With dilatrend treatment AP lowered in 16 cases. In 9 cases HRV became better, in 11 cases it remained the same, and in 4 cases it became worse. Positive HRV dynamics in 7 cases out of 9 was accompanied by lowering of AP, while negative dynamics was observed in one case with rise of AP and in three cases with very low AP or in the absence of AP dynamics. 14 patients felt better, 6 of them manifested better level both of AP and HRV.

CONCLUSION

The method of 24-hour HRV analysis based on assessment of dependence of the value of sinus arrhythmia on HR is useful in evaluating the effectiveness of anti-hypertension therapy. As a rule, an effective decrease in AP is accompanied with improvement of HRV. The absence of improvement of deterioration of HRV in anti-hypertension therapy is a factor which should be taken into consideration when choosing the mode of therapy.

[Trends in heart rate variability in patients with ischemic heart disease and depression treated with antidepressant tianeptine]

AIM

To study heart rate variability (HRV) according to 24-h Holter monitoring of ECG in patients with ischemic heart disease (IHD) and to examine effects of tianeptine on HRV.

MATERIAL AND METHODS

Twenty eight patients with IHD (17 males and 11 females aged 40-70 years) with a verified IHD diagnosis and atherosclerosis of the coronary arteries participated in the trial. Severity of depressive syndrome was assessed by CES-D questionnaire. HR V was assessed by weighted mean variation of the rhythmogram (WMVR) for 24 hours.

RESULTS

Initial WMVR (m +/- sigma) in the study group (IHD with depression, n = 15) was 670 +/- 260 ms, in the control group (IHD without depression, n = 13) - 625 +/- 191 ms (the difference was insignificant (p = 0.72). Initial (m +/- sigma) WMVR in men of the study group (n = 6) before therapy was 460 +/- 139 ms that was less than in the control group (633 +/- 183 ms, n = 11).

CONCLUSION

In men HRV depends on duration of the disease. There was a negative correlation between WMVR difference before and after treatment with tianeptine and difference of relevant depression indices with high correlation coefficient (-0.74, p = 0.03).

[Urgent surgical correction of ventricular septal defects in children of first months of life]

The article presents the results of urgent surgical correction of ventricular septal defects (VSDs) and a range of associated congenital heart diseases (CHDs) in 123 children of the first 6 months of life, hospitalized between 1988 and 2002 in a severe or critical condition. In 102 patients the progression of clinical symptoms was caused by a big single VSD and in 21 patients--by multiple VSDs. 70 patients had significant associated CHDs. Significant extracardiac anomalies were revealed in 75 patients. The condition of 55.3% of children had deteriorated due to pneumonia. Correction of defects with cardiopulmonary bypass was performed after urgent examination and intensive therapy. Hemodynamically significant VSD were closed in 117 (95.2%) patients. Two patients were reoperatied due to the presence of residual VSD. Partial or full simultaneous correction of associated CHDs was performed in 68 patients. 93.5% of patients with isolated VSDs survived the operation. The survival rate of patients with associated CHDs and extracardiac anomalies was 81.5%. Postoperative mortality risk factors were found to be critical condition at hospitalization and preoperative activity of infectious process (P < 0.01 and < 0.05, respectively). Accumulation of experience and introduction of a special approach allowed an 8-time decrease of the hospital mortality, which has not exceeded 3.4% within last 3 years. Good and excellent follow-up results were obtained in 98% of the survived patients within 10 to 67 months after operation. Precise diagnostics of associated CHDs and extracardiac anomalies, intensive preoperative treatment and weighed estimation of indications and risk factors allow significant improvement in the results of primary correction of VSD and accompanying cardiovascular anomalies in children of the first months of life in a heavy and critical condition upon admission.

[Circulating immune complexes in the diagnosis of allergic reactions of the immune-complex type]

The content of intermediate and small circulating immune complexes (iCIC and sCIC), the classical path of compliment activation (CCA), the concentration of C4 and C3 compliment components as well as the levels of IgM, IgG1, IgG2 and IgG3 in blood serum were examined in patients with atopic rhinitis and rhinoconjunctivitis concomitant with hypersensitivity to the Candida albicans allergen of the immediate and mixed (immediate and delayed) types. A significantly reduced concentration of sCIC, sCIC/iCIC(sCIC/iCIC), CCA and of the C4 content as well as a pronouncedly increased IgM concentration was typical of the patients with the mixed allergic reaction, which made them markedly different from the virtually healthy subjects and from patients with the immediate type of hypersensitivity. The most pronounced differences (p < 0.001) between the group of patients with the mixed type of allergic reaction and two other groups were those related with the sCIC/iCIC ratio index. Considering the study results, it can be assumed that the determination of the sCIC/iCIC could be used as an extra criterion in the laboratory diagnosis of the 3d (immunocomplex) types of allergic reaction as made in patients with atopic rhinitis and rhinoconjunctivitis with hypersensitivity to the C. albicans allergen.

[Heart rate variability before and after coronary artery bypass surgery in patients with ischemic heart disease]

Short term heart rate variability (HRV) was studied in 44 patients before, in 2 weeks and 2 months after coronary artery bypass grafting (CABG). Prior to surgery the patients were divided into 2 groups: with normal and substantially lowered HRV parameters. In 2 weeks after CABG lowering of HRV was registered in all patients. In 2 months parameters of HRV returned to preoperative level almost in all patients but did not exceed it despite restoration of coronary blood flow and improvement of myocardial contractility. Intergroup differences of characteristics of HRV remained the same as before CABG.

[Dynamics of heart rate variability in ischemic heart disease patients after coronary artery bypass grafting]

AIM

To study dynamics of 24-hour heart rate variability (HRV) after coronary artery bypass grafting (CABG) and to elucidate relationship between HRV dynamics and clinical course of the disease.

METHODS AND MATERIAL

A novel methodological approach to evaluation of HRV based on measurement of mean weighted rhythmogram variation (MWRV) was implemented. Ninety patients were studied before CABG. Then HRV was assessed in 2 weeks (61 patients), 2 (45 patients), 6 (24 patients)and 12 (33 patients) months after surgery.

RESULTS

At all study points HRV was lower in CHD patients than in healthy persons. Substantial lowering of average MWRV 2 weeks after surgery was followed by return to preoperative level by the end of 2 months, leveling off until 6 months and some decline by the end of a year. Individual changes of MWRV were assessed in 29 patients in whom HRV was evaluated at 5 or 4 study points. Three types of MWRV changes were distinguished: type 1 - "normal" dynamics (9 patients) - elevation of MWRV 2, 6 and 12 months; type 2 (10 patients) - elevation of MWRV after 2 and 6 months with subsequent lowering by the end of 1 year; type 3 (10 patients) - lowering of MWRV In 2 and/or 6 months. The following relationships between MWRV changes and clinical course after surgery were observed: there were no complications among patients with type 1 MWRV dynamics; 8 of 10 type 2 patients had signs of heart failure, or blood pressure elevation, or recurrence of angina by the end of 1 year: among 10 type 3 patients 6 experienced various complications. Recurrence of angina at various intervals after CABG occurred in 5 patients and in all it was associated with MWRV decrease.

CONCLUSION

Pronounced decrease of MWRV between 2 and 12 months after CABG is associated with worse clinical course and its detection should trigger additional investigation and care of a patient.

[A novel approach to assessment of individual 24-hour heart rate variability]

A novel approach to assessment of individual 24-hour heart rate variability (HRV) has been suggested. This approach allows to compare sequences of RR intervals with knowingly nonstationary rhythm and to obtain valuable information on direction (increase or decrease) of HRV changes. The latter was not achievable by existing techniques. Main feature of the novel approach is consideration of dependence of sinus arrhythmia on heart rate on a given time interval (rhythmogram fragment). This became possible due to use of implementation of a new characteristic of 24-hour HRV - mean weighted variation of rhythmogram (MWVR). This parameter repesented a generalization of a previously introduced variation of short rhythmogram fragment (VSRF) and was formed in the following way. Rhythmogram was divided into short fragments and within each fragment VSRF was calculated. Then average variations were averaged for different ranges of HR changes. Each averaged variation was multiplied by weight coefficient which depended on corresponding range of HR changes, and by portion (expressed in percent) of overall number of short rhythmogram fragments belonging to this range. MWVR was determined as sum of resulting multiples. Analysis of rhythmograms from 58 healthy persons showed that MWVR declined with age. In patients with heart failure (n=80) mean MWVR was lower than in healthy persons and decreased with increase of NYHA class of heart failure. Eight patients were restudied while they were classified to a different heart failure class. Transition to a higher class was associated with lowering of MWVR and vice versa. Thus MWVR adequately reflected dynamics of functional state of an individual patient.

[Biochemical diagnosis of hereditary hyperlipoproteinemias]

AIM

To specify characteristics of lipoproteins (LPs) metabolism in patients with diverse forms of hereditary hyperlipoproteinemia (HLP) and determine biochemical tests for their differential diagnosis.

MATERIALS AND METHODS

According to the criteria of polygenic hypercholesterolemia (PHCE), family combined hyperlipidemia (FCHL), family hypertriglyceridemia (FHTG) and family hypercholesterolemia (FHCE), 157 patients were selected aged 7 to 70 years of 192 examinees (76 patients with primary HLP and 116 their close relatives). Lipids were measured by enzyme methods, apoproteins (apo)--by immunoturbidimetry and immune diffusion.

RESULTS

Compared to healthy subjects, PHCE patients were characterized by higher apoB level and proportion cholesterol (CS)/apoB in very low and low density lipoproteins (VLDL and LDL). In unchanged level of high density lipoprotein (HDL) CS and proportion HDLP CS/apoA1 there were reduced quantities of free HDLP CS, HDLP2 CS and apoA1. In FHCE and FCHL there were also low levels of HDL CS in elevated ones of apoE in (VLDL + LDL). However, in FCHL, contrary to FHCE, the proportion SC (VLDP + LDL)/apoB was as in control group. FHTG patients differed from healthy subjects by diminished HDL parameters: lower HDL CS due to free CS and its esters, apoA1 and proportion HDL Cs/apoA. There were no differences with controls by content of apoB and proportion CS (VLDL + LDL)/apoB, apoE levels in different class lipoproteins.

CONCLUSION

Biochemical parameters are proposed which can differentiate various forms of hereditary hyperlipoproteinemia.

[Leukocyte index for the assessment of an allergic process]

The authors discuss the diagnostic significance of the blood formula and of indexes derived from the formula, used in clinical practice, for assessing the allergic reaction. The counts of eosinophils and lymphocytes increase in 56-86% of cases in allergic reactions. Analysis of the blood formula enabled the authors derive a new index for detection of allergic reaction: the allergization index (AI). AI fluctuations in normal subjects are from 0.68 to 1.08, whereas in the patients with various forms of allergic reactions it increases to 2.37-2.97. Allergic reactions were detected by AI in 82-91% of cases.

[The effect of different factors on cardiac rhythm variability in patients with arterial hypertension]

The purpose of this study was to evaluate the influence of different factors, among them left ventricular hypertrophy (LVH) on long-term heart rate variability (HRV) in patients with hypertension. 38 patients with arterial hypertension of different genesis were included in the study. Ischemia was excluded in all the patients by the data of clinical and instrumental methods of investigation. LVH data obtained from HRV of 20 healthy subjects was used as control. HRV was evaluated by estimating variations for short intervals of a rhythmogram (VSI). A HRV decrease did not depend on sex, but essentially depended on patients'a age, disease duration and the form of hypertension. A marked tendency leading to the rate variability decrease was observed only in moderate LVH. In cases of original LVH variability data did not differ from those in patients without signs of LVH. Low or marginal HRV was more often observed in patients with essential hypertension and in those with hypertension of endocrine genesis. As far as renal hypertension is concerned low variability was less frequent. There were a lot of factors which affect the change of HRV. The more significant of them were the patients' age, hypertension genesis and form of hypertension. Factors leading to the rate variability decrease were the following age above 40, endocrine or essential hypertension and moderate form of hypertension.

Influence of left ventricular hypertrophy on heart rate variability in hypertensive patients

Long-term heart rate variability (HRV) data were obtained from 38 patients with arterial hypertension and 20 healthy persons. New method of HRV analysis based on calculation and estimation of variations of short rhythmogram intervals (SRV) was applied. This method showed that HRV level depends on number of factors. The most significant of them are patient's age, arterial hypertension form and duration, and left ventricular hypertrophy degree. Patients with these risk factors may be highly predisposed to rate variability decrease. (Tab. 8, Ref. 8.)

Two-year dynamics of vectorcardiography parameters in patients with primary pulmonary hypertension

VCG data (McFee--Parungao system) were obtained from 12 patients with primary pulmonary hypertension (PPH). During 2 years, VCG investigations were repeated from 2 to 5 times. Various VCG-parameters were analyzed. Space and horizontal QRS areas, projection of integra QRS vector to axis y and the sum of Rx and Sx were diagnostically most significant. Their values proved abnormal at the beginning of survey. In the course of observation, states of the right heart chambers together with VCG-parameter dynamics were investigated in every patient. States of the right cardiac chambers improved in 4 patients. In all of them the parameter turned to normal values. In two patients, during the monitoring time monotonous increase of parameters was observed, with the state of the right heart chambers declining. In 6 patients, state of right heart chambers appeared relatively stable. In these patients, values of all the parameters were either stable or insignificantly changeable around some mean values. Thus, the dynamics of VCG-parameters makes it possible to estimate adequately the states of the right cardiac chambers in PPH patients. (Tab. 1, Fig. 4, Ref. 4)

[Significance of intravascular ultrasound studies in the evaluation of the vascular lumen and wall in interventional radiological procedures]

The paper analyzes the first experience with intravascular ultrasound study (IUSS) in 9 patients at the Cardiosurgery Center. It presents the potentialities of IUSS during interventional radiological procedures. It is concluded that there are benefits and trends of the technique in the exploration of various vascular beds.

[Digital subtraction angiography in the diagnosis of Fallot 's tetralogy]

The authors analyze the efficacy of digital subtraction angiography (DSA) in the diagnosis of Fallot's tetralogy (FT); this method helps simplify and cut down the scope of investigations but does not deteriorate their informative value. DSA findings in 120 patients with TF are analyzed. The study was confined to right ventriculography in the majority of cases, which permitted clear-cut imaging of the anatomical details of the defect due to computer processing of the image. Morphometrical parameters were used to make assessment of involvement of the pulmonary artery system more objective: the ratio of the width of various portions of the pulmonary artery system to the width of descending aorta and the pulmonary arterial index characterizing the area of section of both pulmonary arteries in relation to body surface. The quality of imaging the stenoses and hypoplasia in the pulmonary artery system was high, meeting the requirements of present-day surgery. Moreover, DSA helps diagnose other anatomical particulars of TF and the concomitant defects and abnormalities, left ventricular hypoplasia and the type of right aortic arch among other things. The advantages of DSA in the diagnosis of TF are a lesser volume of catheterization, reduced number of sessions and of the dose of contrast agent infused at each session, better imaging of the anatomical details of the defect and of concomitant defects and abnormalities. All this permit examinations on an outpatient basis.

[Catheter therapy of congenital cardiovascular defects]

The authors analyze the experience gained in catheter operations performed at their Department over the recent 28 years. A total of 500 balloon (Rashkind) and 35 knife (Park) atrioseptostomies were performed in critical patients with different "blue" congenital diseases over this period. An immediate hemodynamic effect at the operation table was attained in 95% of patients. Transluminal balloon valvuloplasty (TLBVP) was performed in 372 patients with valvular stenosis of the pulmonary artery. The results of this operation depend on the patient's age, anatomy of the defect, and correct choice of the diameter of balloon catheter. This intervention is particularly effective in patients aged under 1. In patients with combined valvular and infundibular stenosis the results of TLBVP depend on the severity of stenosis and age of patient. An attempt at TLBVP of congenital aortal stenosis was undertaken in 67 patients. Valvuloplasty was carried out in 57 patients. The operation was effective in 13 (62%) out of 21 patients aged under 1. The mortality in this group was 5.5%. Balloon valvuloplasty of the pulmonary artery was carried out in 71 patients with cyanotic congenital heart diseases. The intervention helped eliminate the critical state, rise the systolic pressure in the pulmonary artery, improve blood saturation with oxygen, and evade the operation for creation of a systemic-pulmonary anastomosis. Isolated and postoperative stenoses of pulmonary arteries were removed in 65 patients. Six Johnson and Johnson stents were effectively implanted to 3 patients with rigid postoperative stenoses; in 32 patients transluminal balloon angioplasty (TLBAP) for coarctation and recoarctation of the aorta brought about a satisfactory immediate hemodynamic effect. TLBAP of Blalock-Taussig's stenosed anastomosis were performed in 60 patients with various cyanotic congenital heart diseases. Its results were good in 39 (65%) patients, satisfactory in 19 (31.7%), and unsatisfactory in only 2 (3%) cases. Of the novel endocardial interventions, dilatation of the conduit following Rastrelli's operation, creation of a defect of the atrial septum after Fontain's operation, and embolization of the coronary-cardiac fistulas and of patent ductus arteriosus were carried out. This review demonstrates wide use of endocardial surgery methods in the treatment of some congenital heart diseases; in many cases such treatment may be an alternative to surgical interventions.

[The use of non-linear methods of statistical analysis in the differential electrocardiographic diagnosis of hypertrophic cardiomyopathy (data from precordial mapping)]

An algorithm was proposed to make a differential diagnosis of hypertrophic cardiomyopathy by precordial ECG mapping in 35 leads (PECG-35) of 82 patients with hypertrophic cardiomyopathy and 339 matched patients: those with isolated left and right ventricular hypertrophy, concurrent ventricular hypertrophy, those with coronary heart disease having scars of various sites and having no cicatricial myocardial changes, including those in the presence of left ventricular hypertrophy, as well as 98 healthy individuals. Computer-aided analysis of their mapping was used to calculate the area of Q, R, S, T waves and ST segment and the prolongation of QRS complex. ECG parameters were analyzed by using cluster and dispersion analyses and the kNN method. The cluster analysis of PECG-35 made it possible to divide all the data on hypertrophic cardiomyopathy into 2 groups. For each the complexes of PECG-35 parameters were identified, in whose range the kNN method differentiated hypertrophic cardiomyopathy with a broad spectrum of abnormalities at a high sensitivity of 67-75% and a specificity of 86-90%.

[Use of integral indicators of precordial mapping in differential diagnosis of focal-cicatricial lesions of the myocardium]

The paper proposes new criteria for differential diagnosis of myocardial "focal scarring" and "++pseudo-scarring" changes in various cardiac abnormalities and homogeneous morphological alterations in the ventricular complex on ECG (the QS, Qr-type abnormalities of the R line) by using the findings of 35 lead ECG mapping (PM-35). ECG-12 and PM-35 were analysed in 427 patients, including those with coronary heart disease (n-122), arterial hypertension and aortic malformations (n-130), dilated cardiomyopathy, congenital cardiac disease (n-175). Electrocardiographic signs of focal scarring lesions were revealed in all the cases with coronary heart disease and 66 with myocardial hypertrophy. The total value of ST segment depression and the sum of Q wave squares in three to five vertical mapping columns were found to be the most significant differential and diagnostic criterion. When scars and ++pseudo-scars were differentiated, a sensitivity of 75% was obtained at a specificity of 87%.

[Computer visualization of three-dimensional vectorcardiographic loops in the diagnosis of the enlargement of cardiac segments]

A nontraditional method was proposed for computed visualization of three-dimensional vectorcardiographic loops in the projections on the two-dimensional planes the least departing from the appropriate loops in terms of root-mean-square deviation. The proposed visualization makes it possible to make a differential diagnosis of isolated forms of enlarged cardiac portions, including those of enlarged atria with high certainty.

[Diagnosis of ischemic heart disease based on the data of precordial mapping]

To improve the efficiency of electrocardiographic diagnosis of coronary heart disease, a search for new meaningful ECG parameters has been carried out, using precordial mapping and automated analysis of the maps. The study included 95 coronary patients, whose diagnosis was verified by visual techniques (coronaroangiography and left ventriculography). ECG-12 showed no signs of past focal/scarry lesions in any of the patients, and detected ischemic changes in 23% only. A group of 95 normal subjects was taken as controls. A classifying function was constructed, using mathematical procedures, stepwise discriminant analysis in particular. Used for the diagnosis of coronary disease, it yielded an 83% sensitivity and an 85% specificity.

[Automated selection of optimal parameters of precordial mapping in the diagnosis of right-ventricular hypertrophy]

New diagnostic parameters, improving the specificity and sensitivity of electrocardiographic diagnosis of right-ventricular hypertrophy, have been identified on the basis of an automated analysis of precordial maps in 56 patients with isolated right-ventricular hypertrophy and 71 normal subjects.

[Information value of different leads for precordial mapping in left ventricular hypertrophy]

New electrocardiographic criteria of left-ventricular hypertrophy (LVH) have been identified at automated analysis of ECG-35 cartograms (71 normal and 88 LVH recordings). Simultaneous application of 2 sums of S and R amplitudes (S32 + R14 and S30 + R19) obtained from the leads other than Wilsonian chest leads enabled a 1.5-fold increase in the sensitivity of electrocardiographic LVH diagnosis, as compared to the Sokolov-Lyon criteria, without loss of specificity. The use of summary R and S areas at the same points on the cartogram further improves the method's sensitivity.

[Integral indices of the automatically reproduced spatial QRS loop in the diagnosis of different forms of myocardial hypertrophy]

A total of 249 patients with arterial hypertension taking a variety of clinical forms, primary pulmonary hypertension, dilatation cardiomyopathy, congenital heart diseases with secondary pulmonary hypertension were examined and allocated to 3 groups: 125 patients with left-ventricular hypertrophy (LVH) (group 1); 44 patients with right-ventricular hypertrophy (RVH) (group 2), and 80 patients with combined hypertrophy of both ventricles (CH). Eighty-one normal subjects were taken as controls. New parameters of diagnostic significance were identified by automated reproduction of vectorcardiographic spatial QRSxyz loop (the Macfee-Parungao system) and computer analysis of vectorcardiographic parameters, that improve electrocardiographic diagnosis of cardiac hypertrophies, as compared to the conventional criteria, bringing its accuracy to 88.8% for LVH, 100% for RVH, and 45% for CH. Typical features of myocardial hypertrophy at large are increased area enclosed by the spatial loop (SQRS greater than 3.4 mV2) and/or increased mean vector (LQRSxyz greater than 0.76 mV), while Lx greater than 0.6 mV and/or Lz less than -0.4 mV were specific for LVH; Lx less than 0.05 mV was specific for RVH, and the H angle ranging from -70 degrees to -140 degrees or H of -60 degrees to -140 degrees at Lz less than 1.1 mV, or -50 degrees to -140 degrees at Lz less than 1.5 mV were specific for CH.

[Diagnostic significance of the vectorcardiogram spatial indices in combined atrial dilatation]

Eighty-two apparently normal subjects and 90 patients with combined atrial dilatation were investigated, using automated amplified-image atrial VCG reproduction with an output of spatial characteristics of the Macfee-Parungao P loop, a method developed at the All-Union Center for Cardiologic Research (USSR Academy of Medical Sciences). Area enclosed by spatial P loop (SPxyz greater than or equal to 0.017 mV2), mean vector size (MPxyz greater than or equal to 120.6 microV) and P loop duration (tPxyz greater than or equal to 0.116 sec) showed the highest diagnostic value. The use of these integral characteristics of the spatial P loop improved identification of two dilated atria, bringing the detection rate to 92%, as compared to 53.3% obtainable with ECG from 12 standard and orthogonal leads.