Anisotropic conduction in the myocardium due to fibrosis: the effect of texture on wave propagation

Cardiac fibrosis occurs in many forms of heart disease. It is well established that the spatial pattern of fibrosis, its texture, substantially affects the onset of arrhythmia. However, in most modelling studies fibrosis is represented by multiple randomly distributed short obstacles that mimic only one possible texture, diffuse fibrosis. An important characteristic feature of other fibrosis textures, such as interstitial and patchy textures, is that fibrotic inclusions have substantial length, which is suggested to have a pronounced effect on wave propagation. In this paper, we study the effect of the elongation of inexcitable inclusions (obstacles) on wave propagation in a 2D model of cardiac tissue described by the TP06 model for human ventricular cells. We study in detail how the elongation of obstacles affects various characteristics of the waves. We quantify the anisotropy induced by the textures, its dependency on the obstacle length and the effects of the texture on the shape of the propagating wave. Because such anisotropy is a result of zig-zag propagation we show, for the first time, quantification of the effects of geometry and source-sink relationship, on the zig-zag nature of the pathway of electrical conduction. We also study the effect of fibrosis in the case of pre-existing anisotropy and introduce a procedure for scaling of the fibrosis texture. We show that fibrosis can decrease or increase the preexisting anisotropy depending on its scaled texture. © 2020, The Author(s).Rochester Academy of Science, RASThis work was supported by Program of RAS Presidium #2, UrFU Competitiveness Enhancement Program (agreement 02.A03.21.0006) and RFBR (No. 18-29-13008). A.P. would like to thank Dr. Rupamanjari Majumder for an advice

Classification Model of Heart Transplant Outcomes Based on Features of Left Ventricular Functional Geometry

The function of the transplanted heart can be significantly affected by acute allograft rejection, chronic rejection, high blood pressure. These factors may induce cardiac remodelling with further adverse consequences for the patients. Dynamic change in the configuration of the left ventricle (LV) from end diastole to end systole (LV functional geometry) is an important factor of the heart pump function. The objective of this study is to evaluate the time dependent changes in parameters of LV functional geometry in the transplanted heart and to assess relations between the changes and adverse outcomes of the heart transplantation (HT). We used linear discriminant analysis (LDA) to build classification models based on either the standard echocardiographic parameters of LV systolic function and global longitudinal strain (GLS) or LV function geometry indexes. The training set for model building included data from patients with different degrees of systolic dysfunction. Using the models, we retrospectively classified data from 31 patients after orthotropic HT. In contrast to the LDA models based on the standard echocardiographic characteristics and GLS, the model based on the LV functional geometry data showed high accuracy in predicting allograft rejection and development of the heart failure in the HT patients. © 2018 Creative Commons Attribution

Impact of inter-ventricular lead distance on cardiac resynchronization therapy outcomes

Cardiac resynchronization therapy (CRT) has been shown as an essential treatment of patients with heart failure, leading to improvements in symptoms, left ventricular (LV) function, and survival. However, up to 30% of appropriately selected patients remain non-responders to CRT. The aim of our study was to test a hypothesis on the impact of lead positioning in the ventricular walls on CRT response in patients with advanced chronic heart failure with and without pre-operative inter and intra-ventricular myocardial dyssynchrony. We examined 53 guideline-selected CRT candidates. Response to CRT was defined in 6 months after implantation of CRT devices. All patients underwent standard and Doppler echocardiography for assessment of LV function and mechanical dyssynchrony. Individual right ventricular (RV) and LV lead tip position, inter-lead distance, and the horizontal and vertical components were measured on the radiograph images with using an automated custom made software Our results showed that the RLV inter-lead distance is an essential parameter correlated with the CRT outcomes. A logistic model comprising the RLV inter-lead distance with parameters of dyssynchrony demonstrated a high predictive power for odds of CRT success. © 2017 IEEE Computer Society. All rights reserved.Research was supported by Act 211 Government of the Russian Federation, agreement № 02.A03.21.0006 and Program of the RAS Presidium #I.33П

Influence of sanatorium treatment with thermotherapy on the adaptive capacity of hard-working people

370 apparently healthy men aged 27 to 35 with considerable mental and physical burden were examined at the sanatorium. They were divided into two groups depending on the duration of rehabilitation. Group 1 consisted of 226 men with rehabilitation period from 18 to 21 days. Group 2 comprised 144 men with rehabilitation period from 10 to 14 days. Each group was subdivided into three subgroups: A, B and C. Patients of Group 1 subgroup A visited cryochamber, patients of Group 1 subgroup B visited infrared sauna, and patients of Group 1 subgroup C visited vibration sauna every second day. Patients of Group 2 subgroups A, B and C had the same procedures every day. Dynamic indicators of nonspecific adaptive response, hemodynamics, vascular adrenergic reactivity of skin, blood coagulation system, lipid and carbohydrate metabolism of all patients were studied. The results allowed us to conclude that all therapeutic complexes could be used in the restoration of adaptive capacity of hard-working people. Cryotherapy performed every second day was the most effective

Влияние механических колебаний на формирование микроструктуры монокристаллов и керамических композитов при выращивании с расплава

Досліджено вплив механічних коливань частотою 50 Гц на процес формування мікроструктури та хімічного складу монокристалів із гексабориду лантану й армованих керамічних композитів системи LaB₆—ZrB₂ під час кристалізації із розплаву та подальшої термообробки. Встановлено, що механічні коливання впливають на процес кристалізації і призводять до вирівнювання концентраційного профілю розподілу атомів перед фронтом росту кристала, змінюють форму та розміри зони розплаву, а також підсилюють структурну неоднорідність. Методами оптичної мікроскопії, рентгенівської текстурдифрактометрії, мікрорентгеноспектральним і рентгенофазовим аналізами показано, що внаслідок дії механічних коливань змінюється кількість, розмір і форма волокон дибориду перехідного металу в процесі спрямованої кристалізації евтектичного сплаву LaB₆—ZrB₂. З’являється розорієнтація матричної і армуючої фаз відносно кристалографічного напрямку росту, що задається кристалом-затравкою, яка призводить до погіршення монокристалічності зразка. Підвищується дефектність структури, що своєю призводить до зменшення періоду ґратки і густини гексабориду лантану та керамічного композиту системи LaB₆—ZrB₂.The effect of mechanical vibration with 50 Hz frequency on the formation of microstructure and chemical composition of single crystals of lanthanum hexaboride and reinforced ceramic composites of LaB₆—ZrB₂ during crystallization from the melt and subsequent heat treatment was investigated. It was found that the mechanical vibrations affect the crystallization and lead to the equalization of the concentration profile of the distribution of atoms in front of the crystal growth, alter the shape and size of the melt zone and increase structural heterogeneity. Methods of optical microscopy, X-ray texture diffractometry, microanalysis and X-ray analysis show that as a result of mechanical vibrations changing the number, size and shape of the transition metal diboride fibers during directional solidification of eutectic alloy LaB₆—ZrB₂ occurs. Disorientation matrix and reinforcing phases relative to crystallographic growth direction, given by the seed crystal, which leads to poor monocrystallinity sample, appear. Increasing of the defect structure reduces the lattice period and density of lanthanum hexaboride and ceramic composite system LaB₆—ZrB₂.Исследовано влияние механических колебаний частотой 50 Гц на процесс формирования микроструктуры и химического состава монокристаллов с гексаборида лантана и армированных керамических композитов системы LaB₆—ZrB₂ при кристаллизации из расплава и последующей термообработке. Установлено, что механические колебания влияют на процесс кристаллизации и приводят к выравниванию концентрационного профиля распределения атомов перед фронтом роста кристалла, изменяют форму и размеры зоны расплава, а также усиливают структурную неоднородность. Методами оптической микроскопии, рентгеновской текстурдифрактометрии, микрорентгеноспектральным и рентгенофазовым анализами показано, что в результате действия механических колебаний изменяются количество, размер и форма волокон диборида переходного металла в процессе направленной кристаллизации эвтектического сплава LaB₆—ZrB₂. Появляется разориентация матричной и армирующей фаз относительно кристаллографического направления роста, задающегося кристаллом-затравкой, которая приводит к ухудшению монокристалличности образца. Повышается дефектность структуры, что в свою очередь приводит к уменьшению периода решетки, а также плотности гексаборида лантана и керамического композита системы LaB₆—ZrB₂

Meshless electrophysiological modeling of cardiac resynchronization therapy—benchmark analysis with finite-element methods in experimental data

Computational models of cardiac electrophysiology are promising tools for reducing the rates of non-response patients suitable for cardiac resynchronization therapy (CRT) by optimizing electrode placement. The majority of computational models in the literature are mesh-based, primarily using the finite element method (FEM). The generation of patient-specific cardiac meshes has traditionally been a tedious task requiring manual intervention and hindering the modeling of a large number of cases. Meshless models can be a valid alternative due to their mesh quality independence. The organization of challenges such as the CRT-EPiggy19, providing unique experimental data as open access, enables benchmarking analysis of different cardiac computational modeling solutions with quantitative metrics. We present a benchmark analysis of a meshless-based method with finite-element methods for the prediction of cardiac electrical patterns in CRT, based on a subset of the CRT-EPiggy19 dataset. A data assimilation strategy was designed to personalize the most relevant parameters of the electrophysiological simulations and identify the optimal CRT lead configuration. The simulation results obtained with the meshless model were equivalent to FEM, with the most relevant aspect for accurate CRT predictions being the parameter personalization strategy (e.g., regional conduction velocity distribution, including the Purkinje system and CRT lead distribution). © 2022 by the authors. Licensee MDPI, Basel, Switzerland

Anatomical Model of Rat Ventricles to Study Cardiac Arrhythmias under Infarction Injury

Species-specific computer models of the heart are a novel powerful tool in studies of life-threatening cardiac arrhythmias. Here, we develop such a model aimed at studying infarction injury in a rat heart, the most common experimental system to investigate the effects of myocardial damage. We updated the Gattoni2016 cellular ionic model by fitting its parameters to experimental data using a population modeling approach. Using four selected cellular models, we studied 2D spiral wave dynamics and found that they include meandering and break-up. Then, using an anatomically realistic ventricular geometry and fiber orientation in the rat heart, we built a model with a postinfarction scar to study the electrophysiological effects of myocardial damage. A post-infarction scar was simulated as an inexcitable obstacle surrounded by a border zone with modified cardiomyocyte properties. For cellular models, we studied the rotation of scroll waves and found that, depending on the model, we can observe different types of dynamics: anchoring, self-termination or stable rotation of the scroll wave. The observed arrhythmia characteristics coincide with those measured in the experiment. The developed model can be used to study arrhythmia in rat hearts with myocardial damage from ischemia reperfusion and to examine the possible arrhythmogenic effects of various experimental interventions. © 2021 by the authors. Licensee MDPI, Basel, Switzerland.This study has been supported by a grant from the Ministry of Science and Higher Education of the Russian Federation (agreement № 075-15-2020-800)

Anatomical model of rat ventricles to study cardiac arrhythmias under infarction injury

Species-specific computer models of the heart are a novel powerful tool in studies of life-threatening cardiac arrhythmias. Here, we develop such a model aimed at studying infarction injury in a rat heart, the most common experimental system to investigate the effects of myocardial damage. We updated the Gattoni2016 cellular ionic model by fitting its parameters to experimental data using a population modeling approach. Using four selected cellular models, we studied 2D spiral wave dynamics and found that they include meandering and break-up. Then, using an anatomically realistic ventricular geometry and fiber orientation in the rat heart, we built a model with a post-infarction scar to study the electrophysiological effects of myocardial damage. A post-infarction scar was simulated as an inexcitable obstacle surrounded by a border zone with modified cardiomyocyte properties. For cellular models, we studied the rotation of scroll waves and found that, depending on the model, we can observe different types of dynamics: anchoring, self-termination or stable rotation of the scroll wave. The observed arrhythmia characteristics coincide with those measured in the experiment. The developed model can be used to study arrhythmia in rat hearts with myocardial damage from ischemia reperfusion and to examine the possible arrhythmogenic effects of various experimental interventions.Cardiolog