scholarly journals Pacemaker Created in Human Ventricle by Depressing Inward-Rectifier K+Current: A Simulation Study

2016 ◽  
Vol 2016 ◽  
pp. 1-9 ◽  
Author(s):  
Yue Zhang ◽  
Kuanquan Wang ◽  
Qince Li ◽  
Henggui Zhang
Keyword(s):  
Spatial Distribution ◽  
Ventricular Myocytes ◽  
Stable State ◽  
Inward Rectifier ◽  
Cardiac Conduction ◽  
Pacemaker Activity ◽  
Battery Life ◽  
Conduction Disorders ◽  
Slow Heart Rate ◽  
The Stability

Cardiac conduction disorders are common diseases which cause slow heart rate and syncope. The best way to treat these diseases by now is to implant electronic pacemakers, which, yet, have many disadvantages, such as the limited battery life and infection. Biopacemaker has been expected to replace the electronic devices. Automatic ventricular myocytes (VMs) could show pacemaker activity, which was induced by depressing inward-rectifier K+current (IK1). In this study, a 2D model of human biopacemaker was created from the ventricular endocardial myocytes. We examined the stability of the created biopacemaker and investigated its driving capability by finding the suitable size and spatial distribution of the pacemaker for robust pacing and driving the surrounding quiescent cardiomyocytes. Our results suggest that the rhythm of the pacemaker is similar to that of the single cell at final stable state. The driving force of the biopacemaker is closely related to the pattern of spatial distribution of the pacemaker.

LANDSLIDE RISK MANAGEMENT IN THE COASTAL ZONE OF THE KUIBYSHEV RESERVOIR DUE THE DESIGN OF HIGH-SPEED LINE "MOSCOW-KAZAN"

2017 ◽  
Author(s):  
Nikolai Petrov ◽  
Nikolai Petrov ◽  
Inna Nikonorova ◽  
Inna Nikonorova ◽  
Vladimir Mashin ◽  
...  
Keyword(s):  
High Speed ◽  
Computational Models ◽  
Stable State ◽  
Landslide Risk ◽  
Kuibyshev Reservoir ◽  
Stepped Surface ◽  
The Stability ◽  
Landslide Slope ◽  
The Village

High-speed railway "Moscow-Kazan" by the draft crosses the Volga (Kuibyshev reservoir) in Chuvashia region 500 m below the village of New Kushnikovo. The crossing plot is a right-bank landslide slope with a stepped surface. Its height is 80 m; the slope steepness -15-16o. The authors should assess the risk of landslides and recommend anti-landslide measures to ensure the safety of the future bridge. For this landslide factors have been analyzed, slope stability assessment has been performed and recommendations have been suggested. The role of the following factors have been analyzed: 1) hydrologic - erosion and abrasion reservoir and runoff role; 2) lithologyc (the presence of Urzhum and Northern Dvina horizons of plastically deformable rocks, displacement areas); 3) hydrogeological (the role of perched, ground and interstratal water); 4) geomorphological (presence of the elemental composition of sliding systems and their structure in the relief); 5) exogeodynamic (cycles and stages of landslide systems development, mechanisms and relationship between landslide tiers of different generations and blocks contained in tiers). As a result 6-7 computational models at each of the three engineering-geological sections were made. The stability was evaluated by the method “of the leaning slope”. It is proved that the slope is in a very stable state and requires the following measures: 1) unloading (truncation) of active heads blocks of landslide tiers) and the edge of the plateau, 2) regulation of the surface and groundwater flow, 3) concrete dam, if necessary.

scholarly journals Study on instability failure mode and monitoring early warning standard of surrounding rock in fully weathered argillaceous sandstone section of large section tunnel

2019 ◽  
Vol 136 ◽  
pp. 04023
Author(s):  
Ming Zhao ◽  
Ke Li ◽  
Hong Yan Guo ◽  
KaiCheng Hua
Keyword(s):  
Limit State ◽  
Stable State ◽  
Simulation Software ◽  
Surrounding Rock ◽  
Large Section ◽  
Rock Stability ◽  
Geological Conditions ◽  
Construction Step ◽  
The Face ◽  
The Stability

Based on the special geological conditions of a tunnel in Qingyuan section of Huizhou-Zhanzhou Expressway, FLAC3d numerical simulation software is used to simulate the rheological properties and instability of surrounding rock in large-section fully weathered sandstone section, and the stability and loss of surrounding rock are analyzed. The deformation of the dome and the face at steady state is analyzed. It is found that: 1) when the surrounding rock is in a stable state, the deformation curve of the dome is smooth. When the surrounding rock of the face is unstable, the front of the face appears ahead. Deformation should be first strengthened on the surrounding rock in front of the face. 2) The arched foot is an important part of the instability of the surrounding rock. In order to prevent the expansion of the collapsed part, the arched part should be reinforced. 3) In order to obtain the limit state of surrounding rock stability, the strength of surrounding rock is reduced, and the strength reduction coefficient corresponding to the displacement sudden point is taken as the safety factor of rock stability around the hole, and the stability safety coefficients of surrounding rock of each construction step are greater than 1.2. 4) The dynamic standard values of deformation control in the whole construction stage are obtained by analyzing the deformation curves of each data monitoring point with time in the corresponding time period of each construction step.

Cellular regeneration as a potential strategy to treat cardiac conduction disorders

2021 ◽  
Vol 131 (19) ◽  
Author(s):  
Satadru K. Lahiri ◽  
Mohit M. Hulsurkar ◽  
Xander H.T. Wehrens
Keyword(s):  
Cardiac Conduction ◽  
Conduction Disorders ◽  
Cellular Regeneration ◽  
Potential Strategy

scholarly journals Heart arrhythmias and conduction disorders in patients with acromegaly: the role of cardiac magnetic resonance imaging

2020 ◽  
Vol 92 (10) ◽  
pp. 70-77
Author(s):  
K. V. Melkozerov ◽  
E. G. Przhiyalkovskaya ◽  
N. V. Tarbaeva ◽  
A. A. Almaskhanova ◽  
M. D. Kuklina ◽  
...  
Keyword(s):  
Magnetic Resonance Imaging ◽  
Magnetic Resonance ◽  
Myocardial Fibrosis ◽  
Cardiac Mri ◽  
Somatostatin Analogs ◽  
Cardiac Conduction ◽  
Resonance Imaging ◽  
Functional Changes ◽  
Conduction Disorders

Cardiovascular complications including arrhythmias and cardiac conduction disorders are one of the main reasons of high mortality rate in acromegaly, while they have not been well explored. Aim.To estimate arrhythmias frequency in acromegaly, identify risk factors leading to the development of arrhythmia and cardiac conduction disorder, to determine the role of cardiac MRI in detecting structural and functional changes. Materials and methods.A single-center prospective cohort study, which included 461 patients (151 men and 310 women) with acromegaly, was conducted. All the patients underwent a standard medical examination, including hormonal blood test, electrocardiogram, echocardiography, electrocardiogram daily monitoring. 18 patients with arrhythmias (11 men and 7 women) had cardiac MRI with gadolinium-based contrast. Results.The results of our research show high frequency of arrhythmias and cardiac conduction disorders in patients with acromegaly 42%. Most frequent kinds of arrhythmias and cardiac conduction disorders were sinus bradycardia 19.1% of the cases and conduction disorders of bundle branch blocks 14.5%. Men were more likely to suffer from arrhythmias and cardiac conduction disorders than women (54.2% and 37.4%, respectively,p=0.0005). Not acromegaly activity but duration of the disease was a main risk factor of arrhythmias and cardiac conduction disorders. Patients with arrhythmias had a long anamnesis of acromegaly (10 and 7 years, respectively, p=0.04). Meanwhile, cardiac conduction disorders were commonly observed in the patients who were treated with somatostatin analogs comparing to the patients who didnt undergo this therapy (50% and 38.6% respectively,p=0.004). We showed that 61% of patients with acromegaly and cardiac conduction disorders who underwent magnetic resonance imaging (MRI) had the signs of myocardial fibrosis. The value of the ejection fraction of the left ventricle according to MRI was higher than with echocardiography (p=0.04). Conclusion.Arrhythmias and cardiac conduction disorders are often observed in patients with acromegaly even with remission of the disease. High risk group need careful diagnostic and monitoring approaches. Cardiac MRI is the gold standard for visualization of structural and morphological changes in the heart. Use of cardiac MRI in acromegalic patients expands our understanding of arrhythmias and cardiac conduction disorders in this disease. There are no specific laboratory markers of diffuse myocardial fibrosis, and the role of myocardial fibrosis in the occurrence of cardiac arrhythmias and conduction disorders needs further studying.

scholarly journals A closed audit reviewing the electrocardiograms of patients presenting to the memory assessment team

BJPsych Open ◽  
2021 ◽  
Vol 7 (S1) ◽  
pp. S30-S30
Author(s):  
Joseph Heath ◽  
Maroulla Anderson ◽  
Jonathan Miles-Stokes
Keyword(s):  
Side Effects ◽  
Acetylcholinesterase Inhibitors ◽  
Left Ventricular ◽  
Cardiac Conduction ◽  
North West ◽  
Cardiac Side Effects ◽  
Memory Assessment ◽  
The North ◽  
Conduction Disorders ◽  
Clinically Significant

AimsTo review the ECGs of all patients referred to MAT services over the preceding 5 year period.BackgroundNeurodegenerative conditions such as Alzheimer's Disease can be treated with Acetylcholinesterase Inhibitors (AChEI) to slow down cognitive decline. Side effects of AChEIs include bradycardia, syncope and cardiac conduction disorders. An electrocardiograms (ECG) is completed prior to memory assessment team (MAT) medical assessments to screen for those who may be at risk of the cardiac side effects of AChEIs. ECGs may be included in the initial referral to the service or completed by the MAT. Given the predominantly elderly population referred to the MATs service, other incidental abnormalities are to be expected. Not all MAT referrals that are screened by memory nurses reach the threshold to be reviewed by the medical team and therefore not all ECGs are routinely reviewed, potentially missing clinically significant abnormalities.ResultA total of 1795 patients were identified as being referred to a single mental health unit in the North West on England over a five-year period. 781 (44%) of the patients had an ECG completed by the MAT, of which 452 (58%) showed an abnormality. Significant abnormalities that were previously unknown to the patients’ primary care provider include eight cases of Atrial Fibrillation (AF), four cases of Trifasciular Block, and 19 cases of Left Ventricular Hypertrophy (LVH). 64 (8%) of patients who had an ECG by the MAT had a bradycardia.ConclusionIn addition to identifying abnormalities that could interfere with memory medication, this audit showed that over half of the ECGs completed by the MAT had an atypical trace. Cardiology was consulted to identify which abnormalities were considered clinically significant and if not already known, the general practitioner (GP) was informed. A change in the local service means that all ECGs completed by the MAT are now screened at point of filling into the notes, so any future abnormalities are identified and followed up immediately.

Anatomy and physiology of the atrioventricular node

ESC CardioMed ◽  
2018 ◽  
pp. 1957-1958
Author(s):  
M. J. Pekka Raatikainen
Keyword(s):  
Atrioventricular Node ◽  
Cardiac Conduction ◽  
Ventricular Rate ◽  
Pacemaker Activity ◽  
Av Block ◽  
Anatomy And Physiology ◽  
Specialized Tissue ◽  
Crucial Part ◽  
Decremental Conduction ◽  
Sinoatrial Node Dysfunction

The atrioventricular node (AVN) and the surrounding area is a crucial part of the cardiac conduction system. It consists of specialized tissue located at the base of the atrial septum within the triangle of Koch. The inherent physiological function of the AVN is to delay cardiac impulse propagation between the atria and the ventricles, and to function as a backup pacemaker in the setting of sinoatrial node dysfunction or advanced atrioventricular (AV) block. AV nodal conduction and pacemaker activity are under strict control by the autonomic nervous system. Due to the unique property of decremental conduction, the AVN protects the heart from an excessive ventricular rate during rapid atrial arrhythmias. On the other hand, the AVN is also an important source of brady- and tachyarrhythmias, and a target for various pharmacological and non-pharmacological arrhythmia therapies.

Characterization and functional consequences of delayed rectifier current transient in ventricular repolarization

2000 ◽  
Vol 278 (3) ◽  
pp. H806-H817 ◽  
Author(s):  
Gary A. Gintant
Keyword(s):  
Action Potential ◽  
Ventricular Myocytes ◽  
Outward Current ◽  
Inward Rectifier ◽  
Ventricular Repolarization ◽  
Delayed Rectifier ◽  
Voltage Range ◽  
Delayed Rectifier Current ◽  
Recovery From Inactivation ◽  
Voltage Dependent

Although inactivation of the rapidly activating delayed rectifier current ( I Kr) limits outward current on depolarization, the role of I Kr (and recovery from inactivation) during repolarization is uncertain. To characterize I Krduring ventricular repolarization (and compare with the inward rectifier current, I K1), voltage-clamp waveforms simulating the action potential were applied to canine ventricular, atrial, and Purkinje myocytes. In ventricular myocytes, I Kr was minimal at plateau potentials but transiently increased during repolarizing ramps. The I Kr transient was unaffected by repolarization rate and maximal after 150-ms depolarizations (+25 mV). Action potential clamps revealed the I Kr transient terminating the plateau. Although peak I Kr transient density was relatively uniform among myocytes, potentials characterizing the peak transients were widely dispersed. In contrast, peak inward rectifier current ( I K1) density during repolarization was dispersed, whereas potentials characterizing I K1 defined a narrower (more negative) voltage range. In summary, rapidly activating I Kr provides a delayed voltage-dependent (and functionally time-independent) outward transient during ventricular repolarization, consistent with rapid recovery from inactivation. The heterogeneous voltage dependence of I Kr provides a novel means for modulating the contribution of this current during repolarization.

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