Properties Of Cardiac Tissue Research Articles

A Time-varying Equivalent Circuit Modeling and Measuring Approach for Intracardiac Communication in Leadless Pacemakers.

Intracardiac wireless communication is crucial for the development of multi-chamber leadless cardiac pacemakers (LCP). However, the time-varying characteristics of intracardiac channel pose major challenges. As such, mastering the dynamic conduction properties of the intracardiac channel and modeling the equivalent time-varying channel are imperative for realizing LCP multi-chamber pacing. In this paper, we present a limiting volume variational approach based on the electrical properties of cardiac tissues and trends in chamber volume variation. This approach was used to establish a quasi-static and a continuous time-varying equivalent circuit model of an intracardiac channel. An equivalence analysis was conducted on the model, and a discrete time-varying equivalent circuit phantom grounded on the cardiac cycle was subsequently established. Moreover, an ex vivo cardiac experimental platform was developed for verification. Results indicate that in the frequency domain, the congruence between phantom and ex vivo experimental outcomes is as high as 94.3%, affirming the reliability of the equivalent circuit model. In the time domain, the correlation is up to 75.3%, corroborating its effectiveness. The proposed time-varying equivalent circuit model exhibits stable and standardized dynamic attributes, serving as a powerful tool for addressing time-varying challenges and simplifying in vivo or ex vivo experiments.

Composite patch with negative Poisson's ratio mimicking cardiac mechanical properties: Design, experiment and simulation

Developing patches that effectively merge intrinsic deformation characteristics of cardiac with superior tunable mechanical properties remains a crucial biomedical pursuit. Currently used traditional block-shaped or mesh patches, typically incorporating a positive Poisson's ratio, often fall short of matching the deformation characteristics of cardiac tissue satisfactorily, thus often diminishing their repairing capability. By introducing auxeticity into the cardiac patches, this study is trying to present a beneficial approach to address these shortcomings of the traditional patches. The patches, featuring the auxetic effect, offer unparalleled conformity to the cardiac complex mechanical challenges. Initially, scaffolds demonstrating the auxetic effect were designed by merging chiral rotation and concave angle units, followed by integrating scaffolds with a composite hydrogel through thermally triggering, ensuring excellent biocompatibility closely mirroring heart tissue. Tensile tests revealed that auxetic patches possessed superior elasticity and strain capacity exceeding cardiac tissue's physiological activity. Notably, Model III showed an equivalent modulus ratio and Poisson's ratio closely toward cardiac tissue, underscoring its outstanding mechanical potential as cardiac patches. Cyclic tensile loading tests demonstrated that Model III withstood continuous heartbeats, showcasing outstanding cyclic loading and recovery capabilities. Numerical simulations further elucidated the deformation and failure mechanisms of these patches, leading to an exploration of influence on mechanical properties with alternative design parameters, which enabled the customization of mechanical strength and Poisson's ratio. Therefore, this research presents substantial potential for designing cardiac auxetic patches that can emulate the deformation properties of cardiac tissue and possess adjustable mechanical parameters.

Heart-on-a-Chip Model of Epicardial-Myocardial Interaction in Ischemia Reperfusion Injury.

Epicardial cells (EPIs) form the outer layer of the heart and play an important role in development and disease. Current heart-on-a-chip platforms still do not fully mimic the native cardiac environment due to the absence of relevant cell types, such as EPIs. Here, using the Biowire II platform, engineered cardiac tissues with an epicardial outer layer and inner myocardial structure are constructed, and an image analysis approach is developed to track the EPI cell migration in a beating myocardial environment. Functional properties of EPI cardiac tissues improve over two weeks in culture. In conditions mimicking ischemia reperfusion injury (IRI), the EPI cardiac tissues experience less cell death and a lower impact on functional properties. EPI cell coverage is significantly reduced and more diffuse under normoxic conditions compared to the post-IRI conditions. Upon IRI, migration of EPI cells into the cardiac tissue interior is observed, with contributions to alpha smooth muscle actin positive cell population. Altogether, a novel heart-on-a-chip model is designed toincorporate EPIs through a formation process that mimics cardiac development, and this work demonstrates that EPI cardiac tissues respond to injury differently than epicardium-free controls, highlighting the importance of including EPIs in heart-on-a-chip constructs that aim to accurately mimic the cardiac environment.

Predicting ventricular tachycardia circuits in patients with arrhythmogenic right ventricular cardiomyopathy using genotype-specific heart digital twins.

Arrhythmogenic right ventricular cardiomyopathy (ARVC) is a genetic cardiac disease that leads to ventricular tachycardia (VT), a life-threatening heart rhythm disorder. Treating ARVC remains challenging due to the complex underlying arrhythmogenic mechanisms, which involve structural and electrophysiological (EP) remodeling. Here, we developed a novel genotype-specific heart digital twin (Geno-DT) approach to investigate the role of pathophysiological remodeling in sustaining VT reentrant circuits and to predict the VT circuits in ARVC patients of different genotypes. This approach integrates the patient's disease-induced structural remodeling reconstructed from contrast-enhanced magnetic-resonance imaging and genotype-specific cellular EP properties. In our retrospective study of 16 ARVC patients with two genotypes: plakophilin-2 (PKP2, n = 8) and gene-elusive (GE, n = 8), we found that Geno-DT accurately and non-invasively predicted the VT circuit locations for both genotypes (with 100%, 94%, 96% sensitivity, specificity, and accuracy for GE patient group, and 86%, 90%, 89% sensitivity, specificity, and accuracy for PKP2 patient group), when compared to VT circuit locations identified during clinical EP studies. Moreover, our results revealed that the underlying VT mechanisms differ among ARVC genotypes. We determined that in GE patients, fibrotic remodeling is the primary contributor to VT circuits, while in PKP2 patients, slowed conduction velocity and altered restitution properties of cardiac tissue, in addition to the structural substrate, are directly responsible for the formation of VT circuits. Our novel Geno-DT approach has the potential to augment therapeutic precision in the clinical setting and lead to more personalized treatment strategies in ARVC.

Predicting ventricular tachycardia circuits in patients with arrhythmogenic right ventricular cardiomyopathy using genotype-specific heart digital twins

Arrhythmogenic right ventricular cardiomyopathy (ARVC) is a genetic cardiac disease that leads to ventricular tachycardia (VT), a life-threatening heart rhythm disorder. Treating ARVC remains challenging due to the complex underlying arrhythmogenic mechanisms, which involve structural and electrophysiological (EP) remodeling. Here, we developed a novel genotype-specific heart digital twin (Geno-DT) approach to investigate the role of pathophysiological remodeling in sustaining VT reentrant circuits and to predict the VT circuits in ARVC patients of different genotypes. This approach integrates the patient’s disease-induced structural remodeling reconstructed from contrast-enhanced magnetic-resonance imaging and genotype-specific cellular EP properties. In our retrospective study of 16 ARVC patients with two genotypes: plakophilin-2 (PKP2, n = 8) and gene-elusive (GE, n = 8), we found that Geno-DT accurately and non-invasively predicted the VT circuit locations for both genotypes (with 100%, 94%, 96% sensitivity, specificity, and accuracy for GE patient group, and 86%, 90%, 89% sensitivity, specificity, and accuracy for PKP2 patient group), when compared to VT circuit locations identified during clinical EP studies. Moreover, our results revealed that the underlying VT mechanisms differ among ARVC genotypes. We determined that in GE patients, fibrotic remodeling is the primary contributor to VT circuits, while in PKP2 patients, slowed conduction velocity and altered restitution properties of cardiac tissue, in addition to the structural substrate, are directly responsible for the formation of VT circuits. Our novel Geno-DT approach has the potential to augment therapeutic precision in the clinical setting and lead to more personalized treatment strategies in ARVC.

Design and Validation of a Soft Robotic Simulator for Transseptal Puncture Training.

Transseptal puncture (TP) is the technique used to access the left atrium of the heart from the right atrium during cardiac catheterization procedures. Through repetition, electrophysiologists and interventional cardiologists experienced in TP develop manual skills to navigate the transseptal catheter assembly to their target on the fossa ovalis (FO). Cardiology fellows and cardiologists that are new to TP currently train on patients to develop this skill, resulting in increased risk of complications. The goal of this work was to create low-risk training opportunities for new TP operators. We developed a Soft Active Transseptal Puncture Simulator (SATPS), designed to match the dynamics, static response, and visualization of the heart during TP. The SATPS includes three subsystems: (i) A soft robotic right atrium with pneumatic actuators mimics the dynamics of a beating heart. (ii) A fossa ovalis insert simulates cardiac tissue properties. (iii) A simulated intracardiac echocardiography environment provides live visual feedback. Subsystem performance was verified with benchtop tests. Face and content validity were evaluated by experienced clinicians. Subsystems accurately represented atrial volume displacement, tenting and puncture force, and FO deformation. Passive and active actuation states were deemed suitable for simulating different cardiac conditions. Participants rated the SATPS as realistic and useful for training cardiology fellows in TP. The SATPS can help improve catheterization skills of novice TP operators. The SATPS could provide novice TP operators the opportunity to improve their TP skills before operating on a patient for the first time, reducing the likelihood of complications.

Multifunctional Silk Fibroin/Carbon Nanofiber Scaffolds for In Vitro Cardiomyogenic Differentiation of Induced Pluripotent Stem Cells and Energy Harvesting from Simulated Cardiac Motion.

In this proof-of-concept study, cardiomyogenic differentiation of induced pluripotent stem cells (iPSCs) is combined with energy harvesting from simulated cardiac motion in vitro. To achieve this, silk fibroin (SF)-based porous scaffolds are designed to mimic the mechanical and physical properties of cardiac tissue and used as triboelectric nanogenerator (TENG) electrodes. The load-carrying mechanism, β-sheet content, degradation characteristics, and iPSC interactions of the scaffolds are observed to be interrelated and regulated by their pore architecture. The SF scaffolds with a pore size of 379 ± 34 μm, a porosity of 79 ± 1%, and a pore interconnectivity of 67 ± 1% upregulated the expression of cardiac-specific gene markers TNNT2 and NKX2.5 from iPSCs. Incorporating carbon nanofibers (CNFs) enhances the elastic modulus of the scaffolds to 45 ± 3 kPa and results in an electrical conductivity of 0.021 ± 0.006 S/cm. The SF and SF/CNF scaffolds are used as conjugate TENG electrodes and generate a maximum power output of 0.37 × 10-3 mW/m2, with an open-circuit voltage and a short circuit current of 0.46 V and 4.5 nA, respectively, under simulated cardiac motion. A novel approach is demonstrated for fabricating scaffold-based cardiac patches that can serve as tissue scaffolds and simultaneously allow energy harvesting.

New Mechanical Markers for Tracking the Progression of Myocardial Infarction.

The mechanical properties of soft tissues can often be strongly correlated with the progression of various diseases, such as myocardial infarction (MI). However, the dynamic mechanical properties of cardiac tissues during MI progression remain poorly understood. Herein, we investigate the rheological responses of cardiac tissues at different stages of MI (i.e., early-stage, mid-stage, and late-stage) with atomic force microscopy-based microrheology. Surprisingly, we discover that all cardiac tissues exhibit a universal two-stage power-law rheological behavior at different time scales. The experimentally found power-law exponents can capture an inconspicuous initial rheological change, making them particularly suitable as markers for early-stage MI diagnosis. We further develop a self-similar hierarchical model to characterize the progressive mechanical changes from subcellular to tissue scales. The theoretically calculated mechanical indexes are found to markedly vary among different stages of MI. These new mechanical markers are applicable for tracking the subtle changes of cardiac tissues during MI progression.

Characterization of the Optical and Thermal Properties of Cardiac Tissue as a Function of Temperature.

In this work, we devised the first characterization of the optical and thermal properties of ex vivo cardiac tissue as a function of different selected temperatures, ranging from room temperature to hyperthermic and ablative temperatures. The broadband (i.e., from 650 nm to 1100 nm) estimation of the optical properties, i.e., absorption coefficient (μa) and reduced scattering coefficient $({\mu ^{\prime}}_s)$, was performed by means of time-domain diffuse optics. Besides, the measurement of the thermal properties was based on the transient hot-wire technique, employing a dual-needle probe to estimate the tissue thermal conductivity (k), thermal diffusivity (α), and volumetric heat capacity (Cv). Increasing the tissue temperature led to variations in the spectral characteristics of μa (e.g., the redshift of the 780 nm peak, the rise of a new peak at 840 nm, and the formation of a valley at 900 nm). Moreover, an increase in the values of ${\mu ^{\prime}}_s$ was assessed as tissue temperature raised (e.g., for 800 nm, at 25 °C ${\mu ^{\prime}}_s = 9.8{\text{ c}}{{\text{m}}^{{\text{ - 1}}}}$, while at 77 °C ${\mu ^{\prime}}_s = 29.1{\text{ c}}{{\text{m}}^{{\text{ - 1}}}}$). Concerning the thermal properties characterization, k was almost constant in the selected temperature interval. Conversely, α and Cv were subjected to an increase and a decrease with temperature, respectively; thus, they registered values of 0.190 mm2/s and 3.03 MJ/(m3•K) at the maximum investigated temperature (79 °C), accordingly.Clinical Relevance- The experimentally obtained optical and thermal properties of cardiac tissue are useful to improve the accuracy of simulation-based tools for thermal therapy planning. Furthermore, the measured properties can serve as a reference for the realization of tissue-mimicking phantoms for medical training and testing of medical instruments.

Conductive polymers for cardiac tissue engineering and regeneration.

Cardiovascular diseases, such as myocardial infarction, are considered a significant global burden and the leading cause of death. Given the inability of damaged cardiac tissue to self-repair, cell-based tissue engineering and regeneration may be the only viable option for restoring normal heart function. To maintain the normal excitation-contraction coupling function of cardiac tissue, uniform electronic and ionic conductance properties are required. To transport cells to damaged cardiac tissues, several techniques, including the incorporation of cells into conductive polymers (CPs) and biomaterials, have been utilized. Due to the complexity of cardiac tissues, the success of tissue engineering for the damaged heart is highly dependent on several variables, such as the cell source, growth factors, and scaffolds. In this review, we sought to provide a comprehensive overview of the electro CPs and biomaterials used in the engineering and regeneration of heart tissue.

P12: Mechanical Characterization of Synthetic Tissues for Cardiac Surgical Training

Background: Synthetic heart models are commonly used for surgical training, especially for complex procedures. However, current models are expensive and poorly mimic heart tissue mechanics and anatomy. 3D printing unconventional materials can produce more realistic models at a more affordable price; therefore, this study investigates the potential of several 3D printed materials as a synthetic tissue for surgical heart models. Methods: Three synthetic cardiac tissues were fabricated: hydrogel samples (3Dresyn SAE1) on a Form2 laser printer, soft polymer samples (3Dresyn SEA10) on a Form2 laser printer, and silicone samples (Dragon Skin Fast 10A) on an Eazao Zero liquid deposition printer. Synthetic tissues were compared to fresh bovine cardiac tissues in terms of puncture resistance, suture retention, and tensile strength using an AEL universal testing machine and 20N PCE Instruments force gauge. Results: There are no significant differences between the mechanical properties of cardiac tissue and the hydrogel-printed SAE1 samples according to ANOVA with a Tukey’s HSD test (Fig1A). There are significant differences between the SEA10 soft polymer sample and cardiac tissue for the puncture and tension tests, but not for the suture retention test (Fig1A). All mechanical test results are significantly different between the 10A silicone and cardiac samples (Fig1A). An example heart is printed with the hydrogel material to demonstrate usability (Fig1B). Conclusion: The 3D printed hydrogel samples better matched the mechanical properties of cardiac tissue than the other printed samples. Although the hydrogel material proved adequate for surgical simulation, other synthetic tissues should be explored to reduce the cost and time of printing, and to better mimic cardiac tissue.

3D-bioprinted cardiac tissues and their potential for disease modeling.

Heart diseases cause over 17.9 million total deaths globally, making them the leading source of mortality. The aim of this review is to describe the characteristic mechanical, chemical and cellular properties of human cardiac tissue and how these properties can be mimicked in 3D bioprinted tissues. Furthermore, the authors review how current healthy cardiac models are being 3D bioprinted using extrusion-, laser- and inkjet-based printers. The review then discusses the pathologies of cardiac diseases and how bioprinting could be used to fabricate models to study these diseases and potentially find new drug targets for such diseases. Finally, the challenges and future directions of cardiac disease modeling using 3D bioprinting techniques are explored.

Biopolymer-based composites for tissue engineering applications: A basis for future opportunities

Biomimetic scaffolds supporting tissue regeneration are complex materials with multifunctional characteristics. The unique biocompatibility and biodegradability of biopolymers make them excellent candidates for tissue engineering and regenerative medicine. Biopolymers, which have a wide range of properties, can be obtained from different natural sources. Depending on the target tissue, biopolymers can be engineered to meet a series of specific functions. We review different types of biopolymers and their composites, besides their interactions with specific cells and tissues. Specific cellular mechanisms in tissue regeneration are also considered to elucidate the effects of biopolymers on controlling cellular mechanisms given their advantages and challenging aspects. Furthermore, the modifications required to mimic the properties of neural, cardiac, bone, and skin tissues are discussed. Utilization of biopolymer-based composites in tissue engineering requires additional improvements, where several challenges should be overcome. This work is mainly focused on biopolymers used in tissue engineering, providing support for engineering of future biocomposites for the same purpose. Some examples of biocomposites are also provided, a general guide for selection of biopolymers and the secondary component (biopolymers as complements, additives, or nano-scale biomaterials) to develop biocomposites.

Abstract 12013: Nuclear Localization of PDGFRa Tyrosine Kinase Represents a Novel Mechanism Controlling the Fibrotic Response of Mesenchymal Stromal Cells to Myocardial Ischemia

Background: We discovered a time dependent dual role role for mesenchymal stromal cells expressing the platelet-derived growth factor alpha (PDGFRα + MSCs), which play essential functions in tissue revascularization and in fibro-adipogenic repair. Hypothesis: Based on our preliminary data, we hypothesized that specific and distinct stromal cells exist in the vertebrate heart, which retain regenerative capacities relevant to the extension of disease. Methods: All animal studies were performed in compliance with the regulations of the NIH and the local institutional animal care. Myocardial ischemia/reperfusion (MI/R) was induced in mice (n=10, FVB female mice) and pigs (n=10 female Yorkshire pigs) with standard procedures. Control animals were not operated (n=3 mice and n=4 pigs). Bulk RNA sequencing (n=4) was performed using a HiSeq2500 (Illumina). Results: Here, we showed that cardiac PDGFRα + MSCs have the potential to revascularize cardiac tissue and likely control cardiac electromechanical properties only earlier after MI/R. During the subacute phase, we discovered nuclear shuttling of the receptor from the plasma membrane before lineage specification into fibrotic cells (nuclear PDGFRα in non-ischemic 3±1 versus ischemic 7.7±2.5 hearts; p<0.05). Interestingly, a similar response was observed in the heart of large animals (i.e., pigs), suggesting a cross-species mechanism controlling PDGFRα + MSCs commitment via intracellular shuffling of the tyrosine kinase receptor. A roadblock to the clinical translation of these discoveries is that there is no mechanism to manipulate PDGFRα + MSCs dual function. To cover this gap, we compared the transcriptomics of murine cardiac and skeletal muscle PDGFRα + MSCs using bulk RNA sequencing in physiological conditions. We discovered that key pathways, likely a signature of non-regenerating stromal cells, are differentially regulated in cardiac PDGFRα + MSCs, including Notch mediators of mesenchymal lineages and IGF-1 signaling. Conclusions: These data suggest that by modulating PDGFRα intracellular shuttling or altering the expression of specific genes, it may be possible to therapeutically direct PDGFRα + MSCs duality to reduce fibrosis, while harnessing their beneficial properties.

MUSIC: Cardiac Imaging, Modelling and Visualisation Software for Diagnosis and Therapy

The tremendous advancement of cardiac imaging methods, the substantial progress in predictive modelling, along with the amount of new investigative multimodalities, challenge the current technologies in the cardiology field. Innovative, robust and multimodal tools need to be created in order to fuse imaging data (e.g., MR, CT) with mapped electrical activity and to integrate those into 3D biophysical models. In the past years, several cross-platform toolkits have been developed to provide image analysis tools to help build such software. The aim of this study is to introduce a novel multimodality software platform dedicated to cardiovascular diagnosis and therapy guidance: MUSIC. This platform was created to improve the image-guided cardiovascular interventional procedures and is a robust platform for AI/Deep Learning, image analysis and modelling in a newly created consortium with international hospitals. It also helps our researchers develop new techniques and have a better understanding of the cardiac tissue properties and physiological signals. Thus, this extraction of quantitative information from medical data leads to more repeatable and reliable medical diagnoses.

Insights into the intracardiac electrogram from analytical and numerical modelling

Abstract Funding Acknowledgements Type of funding sources: Foundation. Main funding source(s): FWO-Flanders, KU Leuven internal starting grant Introduction and Purpose Cardiac electrograms (EGMs) are one of the most important recordings obtained during electroanatomical voltage mapping and lie at the basis for planning most clinical electrophysiological interventions. Despite its widespread use, the relation of EGM shape and amplitude to the underlying excitation patterns and properties of cardiac tissue is not completely understood. Recent clinical studies [1] have provided important new guidelines on the relation between EGM amplitudes and the thickness of myocardial walls. The aim of this study is to quantify the effect of the wall thickness on EGM amplitudes and duration using analytical and in-silico approaches. Methods We study bipolar EGMs both in-silico and analytically in a homogeneous slab of cardiac tissue (70 x 70 x L mm), where L = 2, 5, or 10 mm, with parallel fiber direction. Simulations were performed using the cardiac electrophysiology simulator openCARP [2]. Cardiac cells were described by the ten Tusscher-Panfilov 2006 model (TP06) [4] with epicardial tissue parameters. A plane wave propagating along the fiber direction was initiated. The extracellular voltage at 147 points arranged in a hemisphere around a point was measured to study the effect of bipolar electrode orientation (see Fig. 1A [3]). In addition, we developed an analytical approach to obtain an EGM, using an equivalent dipole representation of the depolarization wavefront and analytical evaluation of the corresponding integrals. Results Fig. 1B and 1C show the dependency of the EGM properties on the electrode orientation, as represented by the angles α (incidence angle) and β (angle between electrode and propagation direction) [3]. Solid lines represent data from a state-of-the-art numerical methodology, the dashed lines show our analytical estimations. Both the peak-to-peak amplitude and EGM width are well approximated by our theory for all orientations of the electrodes. Fig. 2 shows how the EGM is influenced by the myocardial wall thickness L. Both the amplitude and the duration are in good agreement with our theory. We observe that the amplitude as well as the width increase with the slab thickness, confirming the result in [1] but also delivering an accurate analytical expression for this change. It may thus allow to discriminate effects of thickness and other factors affecting the EGMs, such as substrate abnormalities, for example. Conclusion We developed an analytical approach which can correctly describe the amplitude, duration, and shape of the depolarization part of the EGM. Our theory agrees with the previous in-silico and clinical studies on the influence of catheter orientation [3,5], and wall thickness [1,3]. Subsequent work in this direction is expected to provide better guidelines for clinical interpretation of EGMs, accounting for the effects of the thickness of myocardial wall in the characterization of the substrate of cardiac arrhythmias.

The features of atrial fibrillation occurrence in patients who have undergone COVID-19

Funding AcknowledgementsType of funding sources: None.COVID-19 pandemic has a rather negative effect on patients with cardiovascular pathology, also in patients without cardiovascular disease because its pathogenesis is based on generalized vascuities of the microvasculature with the development of multiple thrombosis and thromboembolism. Atrial fibrillation (AF) is one of the major cardiac arrhythmias and accounts for almost one third of all arrhythmias. Changes in electrical, structural, and contractile properties of cardiac tissue that are thought to underlie AF maintenance and progression are reviewed. The aim of this study is to identify the features and predictors that contribute to the onset or development of AF in patients who have had COVID -19.MethodsThis was a three-center prospective study, conducted in the coronary care unit during the period of February 2020 to June 2021. This study included 196 patients with AF who underwent COVID-19 at different times of this period (I group). For comparison, the data of similar 203 AF patients without COVID (II group) were analyzed in the period from February 2018 to February 2019 from the same centers... Medical history, clinical, instrumental and laboratory data, including troponin-1, tissue factor (TF), and hsCRP were studied in all patients. The data obtained was analyzed for statistical significance including multivariable logistic regression using analyses by SPSS 16.ResultsThe compared results showed that the first-onset AF in patients from first group was observed in 18.7% compared with 8.1% in second group. In intensive care units, AF were registered in 44.2% of patients in I group vs. 7.1% of patients in II group. In first group among patients with ACS, AF occurred in 12.7% of cases vs. similar patients in II group- 8.4%. In first group hypokalemia was observed in 67.8% of cases vs. 28.6% in II group... Multivariable logistic regression was shown that among tested biomarkers, hsCRP, troponin‐I and TF were more higher in patients undergoing COVID in compared patients with AF without COVID (odds ratio, 3.48; p<0.001, 2.36 p<0.017 and 2.48 p<0.01 accordingly).ConclusionsSome features of the onset or development of AF were identified in patients undergoing COVID. So, In these patients compared with AF patients without COVID, AF more often occurs in clinically severe patients, with ACS, as well as in patients with severe hypokalemia, higher hsCRP, TF and troponin values.

How viscous is the beating heart?: Insights from a computational study.

Understanding tissue rheology is critical to accurately model the human heart. While the elastic properties of cardiac tissue have been extensively studied, its viscous properties remain an issue of ongoing debate. Here we adopt a viscoelastic version of the classical Holzapfel Ogden model to study the viscous timescales of human cardiac tissue. We perform a series of simulations and explore stress-relaxation curves, pressure-volume loops, strain profiles, and ventricular wall strains for varying viscosity parameters. We show that the time window for model calibration strongly influences the parameter identification. Using a four-chamber human heart model, we observe that, during the physiologically relevant time scales of the cardiac cycle, viscous relaxation has a negligible effect on the overall behavior of the heart. While viscosity could have important consequences in pathological conditions with compromised contraction or relaxation properties, we conclude that, for simulations within the physiological range of a human heart beat, we can reasonably approximate the human heart as hyperelastic.

Toward the development of a polarimetric tool to diagnose the fibrotic human ventricular myocardium.

.SignificanceOptical polarimetry is an emerging modality that effectively quantifies the bulk optical properties that correlate with the anisotropic structural properties of cardiac tissues. We demonstrate the application of a polarimetric tool for characterizing healthy and fibrotic human myocardial tissues efficiently with a high degree of accuracy.AimThe study was aimed to characterize the myocardial tissues from the left ventricle and right ventricle of control and diseased subjects. The diseased subjects were composed of two groups: with rheumatic heart disease (RHD) and with myxomatous valve (MV) disease.ApproachA portable, affordable, and accurate linear polarization-based diagnostic tool is developed to measure the degree of linear polarization (DOLP) of the myocardial tissues while working at a wavelength of 850 nm.ResultsThe sensitivity, specificity, and accuracy of the polarimetric tool in distinguishing the control group from the RHD group were found to be 73.33%, 76.92%, and 75%, respectively, and from the MV group were 91.6%, 62.5%, and 80%, respectively, which demonstrates the efficacy of the polarimetric tool to distinguish the healthy myocardial tissues from diseased tissues.ConclusionsWe have successfully developed a polarimetric tool that can aid cardiologists in characterizing the myocardial tissues in conjunction with endomyocardial biopsy. This work should be followed up with experiments on a large cohort of control and diseased subjects. We intend to create and develop a probe to quantify the DOLP of in vivo heart tissue during surgery.

Scaffold-free 3D printing for fabrication of biomimetic branched multinucleated cardiac tissue construct: A promising ex vivo model for in situ detection of drug-induced sodium ion channel responses

3D bioprinted cardiac constructs have the potential to develop into functional native tissue. Although bioengineered cardiac constructs can be a promising tool for evaluating cardiac responses, the intrinsic limitation in reproducing the well-defined structural and functional properties of native cardiac tissue within the generated substitute restricts their applications. Herein, for the first time, we have introduced a sophisticated scaffold-free de novo three-dimensional (3D) printing model (SFP) to regenerate biomimetic cardiac tissue with a multinucleated branched cellular structure similar to native tissue–like phenotypes. Furthermore, the formation of tight intracellular junctions expressing connexin 43 certifies the maturation of the fabricated structure. In addition, in situ measurement of the bioengineered cardiac construct's physiologic sodium ion channel responses to known cardiac drugs was successfully performed. Hence, the proposed methodology recapitulates a significant milestone in developing biomimetic cardiac tissue structure and functionality in vitro and could be applied for regenerative therapies, disease modeling, and drug screening.