LIVIVO - Search results -

Search results

Result 1 - 10 of total 44

Search options

Article ; Online: Transition mechanisms from atrial flutter to atrial fibrillation during anti-tachycardia pacing therapy.

Okada, Jun-Ichi / Washio, Takumi / Sugiura, Seiryo / Hisada, Toshiaki

Pacing and clinical electrophysiology : PACE

2023 Volume 46, Issue 12, Page(s) 1509–1518

Abstract: Background: Atrial anti-tachycardia pacing (aATP) has been shown to be effective for the termination of atrial tachyarrhythmias, but its success rate is still not high enough.: Objective: The main objective of this study was to investigate the ... ...

Abstract	Background: Atrial anti-tachycardia pacing (aATP) has been shown to be effective for the termination of atrial tachyarrhythmias, but its success rate is still not high enough. Objective: The main objective of this study was to investigate the mechanisms of atrial flutter (AFL) termination by aATP and the transition from AFL to atrial fibrillation (AF) during aATP. Methods: We developed a multi-scale model of the human atrium based on magnetic resonance images and examined the atrial electrophysiology of AFL during aATP with a ramp protocol. Results: In successful cases of aATP, paced excitation entered the excitable gap and collided with the leading edge of the reentrant wave front. Furthermore, the excitation propagating in the opposite direction collided with the trailing edge of the reentrant wave to terminate AFL. The second collision was made possible by the distribution of the wave propagation velocity in the atria. The detailed analysis revealed that the slowing of propagation velocity occurred at the exit of the sub-Eustachian isthmus, probably due to source-sink mismatch. During the transition from AFL to AF, the excitation collided with the refractory zone of the preceding wave and broke into multiple wave fronts to induce AF. A similar observation was made for the transition from AF to sinus rhythm. In both cases, the complex anatomy of the atria played an essential role. Conclusion: The complex anatomy of atria plays an essential role in the maintenance of stable AFL and its termination by aATP, which were revealed by the realistic three-dimensional simulation model.
MeSH term(s)	Humans ; Atrial Flutter/therapy ; Atrial Fibrillation/therapy ; Cardiac Pacing, Artificial ; Tachycardia/therapy ; Heart Atria
Language	English
Publishing date	2023-11-03
Publishing country	United States
Document type	Journal Article ; Research Support, Non-U.S. Gov't
ZDB-ID	424437-0
ISSN	1540-8159 ; 0147-8389
ISSN (online)	1540-8159
ISSN	0147-8389
DOI	10.1111/pace.14863
Database	MEDical Literature Analysis and Retrieval System OnLINE

Full text online

Accessible to users with ZB MED library card

In stock of ZB MED Cologne/Königswinter

Zs.A 1466: Show issues			Location: Je nach Verfügbarkeit (siehe Angabe bei Bestand) bis Jg. 1994: Bestellungen von Artikeln über das Online-Bestellformular Jg. 1995 - 2021: Lesesall (1.OG) ab Jg. 2022: Lesesaal (EG)
Zs.MO 399: Show issues

Order via subito

This service is chargeable due to the Delivery terms set by subito. Orders including an article and supplementary material will be classified as separate orders. In these cases, fees will be demanded for each order.

Details ▾

Article ; Online: Low-energy defibrillation using a base-apex epicardial electrode.

Okada, Jun-Ichi / Washio, Takumi / Sugiura, Seiryo / Hisada, Toshiaki

Pacing and clinical electrophysiology : PACE

2023 Volume 46, Issue 11, Page(s) 1325–1332

Abstract: Background: Current implantable cardioverter defibrillators (ICDs) require electric conduction with high voltage and high energy, which can impair cardiac function and induce another malignant arrhythmia. As a result, there has been a demand for an ICD ... ...

Abstract	Background: Current implantable cardioverter defibrillators (ICDs) require electric conduction with high voltage and high energy, which can impair cardiac function and induce another malignant arrhythmia. As a result, there has been a demand for an ICD that can effectively operate with lower energy to mitigate the risks of a strong electric shock. Methods: A pair of sheet-shaped electrodes covering the heart were analyzed in three configurations (top-bottom, left-right, and front-back) using a heart simulator. We also varied the distance between the two electrodes (clearance) to identify the electrode shape with the lowest defibrillation threshold (DFT). We also investigated the ICD shock waveform, shock direction, and the effect of the backside insulator of the electrode. Results: The DFT was high when the clearance was too small and the DFT was high even when the clearance was too large, suggesting that an optimal value clearance. The top-bottom electrodes with optimal clearance showed the lowest DFT when the biphasic shocks set the top electrode to a high potential first and then the bottom electrode was set to a high potential. An interval between a first shock waveform and a second shock waveform should be provided for low-energy defibrillation. Because the insulator prevents unnecessary current flow to the backside, the DFT of the electrodes with insulators is less than those without insulators. Conclusion: Painless defibrillation using sheet-shaped electrodes on the epicardium is predicated on the basis of results using a heart simulator.
MeSH term(s)	Humans ; Electric Countershock/methods ; Defibrillators, Implantable ; Ventricular Fibrillation ; Pericardium
Language	English
Publishing date	2023-10-13
Publishing country	United States
Document type	Journal Article
ZDB-ID	424437-0
ISSN	1540-8159 ; 0147-8389
ISSN (online)	1540-8159
ISSN	0147-8389
DOI	10.1111/pace.14832
Database	MEDical Literature Analysis and Retrieval System OnLINE

Full text online

Accessible to users with ZB MED library card

In stock of ZB MED Cologne/Königswinter

Zs.A 1466: Show issues			Location: Je nach Verfügbarkeit (siehe Angabe bei Bestand) bis Jg. 1994: Bestellungen von Artikeln über das Online-Bestellformular Jg. 1995 - 2021: Lesesall (1.OG) ab Jg. 2022: Lesesaal (EG)
Zs.MO 399: Show issues

Order via subito

Details ▾

Article ; Online: UT-Heart: A Finite Element Model Designed for the Multiscale and Multiphysics Integration of our Knowledge on the Human Heart.

Sugiura, Seiryo / Okada, Jun-Ichi / Washio, Takumi / Hisada, Toshiaki

Methods in molecular biology (Clifton, N.J.)

2022 Volume 2399, Page(s) 221–245

Abstract: To fully understand the health and pathology of the heart, it is necessary to integrate knowledge accumulated at molecular, cellular, tissue, and organ levels. However, it is difficult to comprehend the complex interactions occurring among the building ... ...

Abstract	To fully understand the health and pathology of the heart, it is necessary to integrate knowledge accumulated at molecular, cellular, tissue, and organ levels. However, it is difficult to comprehend the complex interactions occurring among the building blocks of biological systems across these scales. Recent advances in computational science supported by innovative high-performance computer hardware make it possible to develop a multiscale multiphysics model simulating the heart, in which the behavior of each cell model is controlled by molecular mechanisms and the cell models themselves are arranged to reproduce elaborate tissue structures. Such a simulator could be used as a tool not only in basic science but also in clinical settings. Here, we describe a multiscale multiphysics heart simulator, UT-Heart, which uses unique technologies to realize the abovementioned features. As examples of its applications, models for cardiac resynchronization therapy and surgery for congenital heart disease will be also shown.
MeSH term(s)	Computer Simulation ; Finite Element Analysis ; Heart ; Humans
Language	English
Publishing date	2022-05-23
Publishing country	United States
Document type	Journal Article
ISSN	1940-6029
ISSN (online)	1940-6029
DOI	10.1007/978-1-0716-1831-8_10
Database	MEDical Literature Analysis and Retrieval System OnLINE

Order via subito

Inter-library loan at ZB MED

Your chosen title can be delivered directly to ZB MED Cologne location if you are registered as a user at ZB MED Cologne.

Article: Using Systolic Local Mechanical Load to Predict Fiber Orientation in Ventricles.

Washio, Takumi / Sugiura, Seiryo / Okada, Jun-Ichi / Hisada, Toshiaki

Frontiers in physiology

2020 Volume 11, Page(s) 467

Abstract: A simple rule adopted for myofiber reorientation in the ventricles is pursued by taking the microscopic branching network of myocytes into account. The macroscopic active tension generated on the microscopic branching structure is modeled by a ... ...

Abstract	A simple rule adopted for myofiber reorientation in the ventricles is pursued by taking the microscopic branching network of myocytes into account. The macroscopic active tension generated on the microscopic branching structure is modeled by a multidirectional active stress tensor, which is defined as a function of the strains in the branching directions. In our reorientation algorithm, the principal direction of the branching network is updated so that it turns in the direction of greater active tension in the isovolumetric systole. Updates are performed step-by-step after the mechanical equilibrium has been attained with the current fiber structure. Starting from a nearly flat distribution of the principal fiber orientation along the circumferential direction, the reoriented fiber helix angles range from 70 to 40° at epicardium and from 60 to 80° at endocardium, in agreement with experimental observations. The helical ventricular myocardial band of Torrent-Guasp's model and the apical spiral structure of Rushmer's model are also reconstructed by our algorithm. Applying our algorithm to the infarcted ventricle model, the fiber structure near the infarcted site is remodeled so that the helix angle becomes steeper with respect to the circumferential direction near the epicardial surface. Based on our numerical analysis, we draw the following conclusions. (i) The multidirectional active tension based on the microscopic branching network is potentially used to seek tighter connection with neighboring aggregates. (ii) The thickening and thinning transitions in response to active tension in each myocyte allow the macroscopic principal fiber orientation of the microscopic branching network to move toward the direction of greater active tension. (iii) The force-velocity relationship is the key factor in transferring the fiber shortening strain to the magnitude of active tensions used in the myofiber reorientation. (iv) The algorithm naturally leads to homogeneity in the macroscopic active tension and the fiber shortening strain, and results in near-optimal pumping performance. (v) However, the reorientation mechanism may degrade the pumping performance if there is severely inhomogeneous contractility resulting from infarction. Our goal is to provide a tool to predict the fiber architecture of various heart disease patients for numerical simulations of their treatment plans.
Language	English
Publishing date	2020-06-09
Publishing country	Switzerland
Document type	Journal Article
ZDB-ID	2564217-0
ISSN	1664-042X
ISSN	1664-042X
DOI	10.3389/fphys.2020.00467
Database	MEDical Literature Analysis and Retrieval System OnLINE

Order via subito

Article: A Multiple Step Active Stiffness Integration Scheme to Couple a Stochastic Cross-Bridge Model and Continuum Mechanics for Uses in Both Basic Research and Clinical Applications of Heart Simulation.

Yoneda, Kazunori / Okada, Jun-Ichi / Watanabe, Masahiro / Sugiura, Seiryo / Hisada, Toshiaki / Washio, Takumi

Frontiers in physiology

2021 Volume 12, Page(s) 712816

Abstract: In a multiscale simulation of a beating heart, the very large difference in the time scales between rapid stochastic conformational changes of contractile proteins and deterministic macroscopic outcomes, such as the ventricular pressure and volume, have ... ...

Abstract	In a multiscale simulation of a beating heart, the very large difference in the time scales between rapid stochastic conformational changes of contractile proteins and deterministic macroscopic outcomes, such as the ventricular pressure and volume, have hampered the implementation of an efficient coupling algorithm for the two scales. Furthermore, the consideration of dynamic changes of muscle stiffness caused by the cross-bridge activity of motor proteins have not been well established in continuum mechanics. To overcome these issues, we propose a multiple time step scheme called the multiple step active stiffness integration scheme (MusAsi) for the coupling of Monte Carlo (MC) multiple steps and an implicit finite element (FE) time integration step. The method focuses on the active tension stiffness matrix, where the active tension derivatives concerning the current displacements in the FE model are correctly integrated into the total stiffness matrix to avoid instability. A sensitivity analysis of the number of samples used in the MC model and the combination of time step sizes confirmed the accuracy and robustness of MusAsi, and we concluded that the combination of a 1.25 ms FE time step and 0.005 ms MC multiple steps using a few hundred motor proteins in each finite element was appropriate in the tradeoff between accuracy and computational time. Furthermore, for a biventricular FE model consisting of 45,000 tetrahedral elements, one heartbeat could be computed within 1.5 h using 320 cores of a conventional parallel computer system. These results support the practicality of MusAsi for uses in both the basic research of the relationship between molecular mechanisms and cardiac outputs, and clinical applications of perioperative prediction.
Language	English
Publishing date	2021-08-13
Publishing country	Switzerland
Document type	Journal Article
ZDB-ID	2564217-0
ISSN	1664-042X
ISSN	1664-042X
DOI	10.3389/fphys.2021.712816
Database	MEDical Literature Analysis and Retrieval System OnLINE

Order via subito

Article ; Online: Chloroquine and hydroxychloroquine provoke arrhythmias at concentrations higher than those clinically used to treat COVID-19: A simulation study.

Okada, Jun-Ichi / Yoshinaga, Takashi / Washio, Takumi / Sawada, Kohei / Sugiura, Seiryo / Hisada, Toshiaki

Clinical and translational science

2021 Volume 14, Issue 3, Page(s) 1092–1100

Abstract: The risk of fatal arrhythmias is the major concern for using chloroquine (CQ) or hydroxychloroquine (HCQ) to treat coronavirus disease 2019 (COVID-19), but the reported number of life-threatening arrhythmic events or deaths is relatively small. The ... ...

Abstract	The risk of fatal arrhythmias is the major concern for using chloroquine (CQ) or hydroxychloroquine (HCQ) to treat coronavirus disease 2019 (COVID-19), but the reported number of life-threatening arrhythmic events or deaths is relatively small. The objective of this study was to assess the arrhythmogenic risk of these two drugs using a multiscale heart simulation, which allows testing even at high concentrations, including those that cause fatal arrhythmias. We measured the inhibitory action of CQ, HCQ, and HCQ with 30 μM azithromycin (AZ) on six ion currents (fast [INa] and late [INa,L] components of the sodium current, L-type calcium current [ICa,L], rapid [IKr/hERG], and slow [IKs] components of delayed rectifier potassium, and inward rectifier potassium [IK1]) over a wide range of concentrations using the automated patch-clamp system. Using the concentration-inhibition relationship that was thus obtained, we simulated the drug effects while increasing the concentration until the life-threatening arrhythmia, torsade de pointes (TdP), was observed. The obtained threshold concentrations for TdP were 12.5, 35, and 22.5 μM for CQ, HCQ, and HCQ with AZ, respectively. Adding therapeutic concentrations of mexiletine or verapamil successfully prevented the occurrence of TdP, and verapamil was more effective. CQ, HCQ, and HCQ with AZ thresholds for TdP were larger than both antiviral concentrations that were reported by in vitro experiments and free plasma concentrations that were attained by the clinically used dosage. The current simulation data provided a safety margin to the currently used clinical dose for CQ and HCQ/AZ. Study Highlights WHAT IS THE CURRENT KNOWLEDGE ON THE TOPIC? Despite the potent in vitro antiviral effect, clinical trials have failed to show the therapeutic effects of chloroquine (CQ) and hydroxychloroquine (HCQ)/azithromycin (AZ) to treat coronavirus disease 2019. Torsadogenic potentials may limit the dosage of these drugs, but the reported incidence of fatal arrhythmias is rare. WHAT QUESTION DID THIS STUDY ADDRESS? Our objective was to assess the arrhythmogenicity of CQ and HCQ/AZ over a wide range of drug concentrations using a multiscale heart simulation. WHAT DOES THIS STUDY ADD TO OUR KNOWLEDGE? Our study showed that CQ and HCQ/AZ do not induce fatal arrhythmias even at concentrations much higher than in vitro antiviral half-maximal effective concentration (EC
MeSH term(s)	Anti-Arrhythmia Agents/therapeutic use ; Arrhythmias, Cardiac/chemically induced ; COVID-19/drug therapy ; Chloroquine/adverse effects ; Computer Simulation ; Electrocardiography/drug effects ; Humans ; Hydroxychloroquine/adverse effects ; SARS-CoV-2
Chemical Substances	Anti-Arrhythmia Agents ; Hydroxychloroquine (4QWG6N8QKH) ; Chloroquine (886U3H6UFF)
Language	English
Publishing date	2021-02-13
Publishing country	United States
Document type	Journal Article ; Research Support, Non-U.S. Gov't
ZDB-ID	2433157-0
ISSN	1752-8062 ; 1752-8054
ISSN (online)	1752-8062
ISSN	1752-8054
DOI	10.1111/cts.12976
Database	MEDical Literature Analysis and Retrieval System OnLINE

Order via subito

Article: A thermodynamically consistent monte carlo cross-bridge model with a trapping mechanism reveals the role of stretch activation in heart pumping.

Yoneda, Kazunori / Kanada, Ryo / Okada, Jun-Ichi / Watanabe, Masahiro / Sugiura, Seiryo / Hisada, Toshiaki / Washio, Takumi

Frontiers in physiology

2022 Volume 13, Page(s) 855303

Abstract: Changes in intracellular calcium concentrations regulate heart beats. However, the decline in the left ventricular pressure during early diastole is much sharper than that of the ... ...

Abstract	Changes in intracellular calcium concentrations regulate heart beats. However, the decline in the left ventricular pressure during early diastole is much sharper than that of the Ca
Language	English
Publishing date	2022-09-08
Publishing country	Switzerland
Document type	Journal Article
ZDB-ID	2564217-0
ISSN	1664-042X
ISSN	1664-042X
DOI	10.3389/fphys.2022.855303
Database	MEDical Literature Analysis and Retrieval System OnLINE

Order via subito

Article: Clinical and pharmacological application of multiscale multiphysics heart simulator, UT-Heart.

Okada, Jun-Ichi / Washio, Takumi / Sugiura, Seiryo / Hisada, Toshiaki

The Korean journal of physiology & pharmacology : official journal of the Korean Physiological Society and the Korean Society of Pharmacology

2019 Volume 23, Issue 5, Page(s) 295–303

Abstract: A heart simulator, UT-Heart, is a finite element model of the human heart that can reproduce all the fundamental activities of the working heart, including propagation of excitation, contraction, and relaxation and generation of blood pressure and blood ... ...

Abstract	A heart simulator, UT-Heart, is a finite element model of the human heart that can reproduce all the fundamental activities of the working heart, including propagation of excitation, contraction, and relaxation and generation of blood pressure and blood flow, based on the molecular aspects of the cardiac electrophysiology and excitation-contraction coupling. In this paper, we present a brief review of the practical use of UT-Heart. As an example, we focus on its application for predicting the effect of cardiac resynchronization therapy (CRT) and evaluating the proarrhythmic risk of drugs. Patient-specific, multiscale heart simulation successfully predicted the response to CRT by reproducing the complex pathophysiology of the heart. A proarrhythmic risk assessment system combining
Language	English
Publishing date	2019-08-26
Publishing country	Korea (South)
Document type	Journal Article ; Review
ZDB-ID	1387595-4
ISSN	2093-3827 ; 1226-4512
ISSN (online)	2093-3827
ISSN	1226-4512
DOI	10.4196/kjpp.2019.23.5.295
Database	MEDical Literature Analysis and Retrieval System OnLINE

In stock of ZB MED Cologne/Königswinter

Zs.A 4872: Show issues

Location:
Je nach Verfügbarkeit (siehe Angabe bei Bestand)
bis Jg. 1994: Bestellungen von Artikeln über das Online-Bestellformular
Jg. 1995 - 2021: Lesesall (2.OG)
ab Jg. 2022: Lesesaal (EG)

Order via subito

Details ▾
- See ZB MED holdings
- Order with fees

Article ; Online: Semi-Implicit Time Integration with Hessian Eigenvalue Corrections for a Larger Time Step in Molecular Dynamics Simulations.

Washio, Takumi / Kanada, Ryo / Cui, Xiaoke / Okada, Jun-Ichi / Sugiura, Seiryo / Takada, Shoji / Hisada, Toshiaki

Journal of chemical theory and computation

2021 Volume 17, Issue 9, Page(s) 5792–5804

Abstract: In molecular dynamics simulations, the limited time step size has been a barrier to simulating long-time behaviors. Implicit time integration methods allow markedly larger time steps than the standard explicit time method, although they have major ... ...

Abstract	In molecular dynamics simulations, the limited time step size has been a barrier to simulating long-time behaviors. Implicit time integration methods allow markedly larger time steps than the standard explicit time method, although they have major drawbacks such as overheads solving linear systems and instability of Newton iterations. To overcome these issues, we propose a semi-implicit time integration scheme, the semi-implicit Hessian correction (SimHec) scheme, for overdamped Langevin dynamics. The method focuses on the Hessian matrices of bonded and nonbonded interactions, where components with large negative Hessian eigenvalues are cut off in the linear approximation of momentum equations to avoid instability. The narrow band Hessian matrix enables an efficient parallelized linear solution with an overlapping approximation. We tested SimHec for the interdomain fluctuations in adenylate kinase and the powerstroke transition of myosin II using a coarse-grained protein model. SimHec reproduced the same dynamics as the explicit method, although the transition dynamics tended to be accelerated and fluctuations in bonded potentials were slightly reduced. These deviations were corrected using a hybrid method, SimHec-H, which adds explicit time steps after the semi-implicit time step. The proposed scheme allowed us to use time steps 50-200 times larger than those in explicit time integration, which resulted in a speedup factor of 7-30 taking the overhead into account.
Language	English
Publishing date	2021-08-05
Publishing country	United States
Document type	Journal Article
ISSN	1549-9626
ISSN (online)	1549-9626
DOI	10.1021/acs.jctc.1c00398
Database	MEDical Literature Analysis and Retrieval System OnLINE

Order via subito

Inter-library loan at ZB MED

Your chosen title can be delivered directly to ZB MED Cologne location if you are registered as a user at ZB MED Cologne.

Article ; Online: Ionic mechanisms of ST segment elevation in electrocardiogram during acute myocardial infarction.

Okada, Jun-Ichi / Fujiu, Katsuhiko / Yoneda, Kazunori / Iwamura, Takashi / Washio, Takumi / Komuro, Issei / Hisada, Toshiaki / Sugiura, Seiryo

The journal of physiological sciences : JPS

2020 Volume 70, Issue 1, Page(s) 36

Abstract: ST elevation on an electrocardiogram is a hallmark of acute transmural ischemia. However, the underlying mechanism remains unclear. We hypothesized that high ischemic sensitivities of epicardial adenosine triphosphate-sensitive potassium ( ... ...

Abstract	ST elevation on an electrocardiogram is a hallmark of acute transmural ischemia. However, the underlying mechanism remains unclear. We hypothesized that high ischemic sensitivities of epicardial adenosine triphosphate-sensitive potassium (IK
MeSH term(s)	Action Potentials ; Computer Simulation ; Electrocardiography ; Finite Element Analysis ; Heart Rate ; Humans ; KATP Channels/metabolism ; Models, Cardiovascular ; Pericardium/metabolism ; Pericardium/physiopathology ; Potassium/metabolism ; Predictive Value of Tests ; ST Elevation Myocardial Infarction/diagnosis ; ST Elevation Myocardial Infarction/metabolism ; ST Elevation Myocardial Infarction/physiopathology ; Sodium/metabolism ; Time Factors
Chemical Substances	KATP Channels ; Sodium (9NEZ333N27) ; Potassium (RWP5GA015D)
Language	English
Publishing date	2020-07-13
Publishing country	Japan
Document type	Comparative Study ; Journal Article ; Video-Audio Media
ZDB-ID	2234472-X
ISSN	1880-6562 ; 1880-6546
ISSN (online)	1880-6562
ISSN	1880-6546
DOI	10.1186/s12576-020-00760-3
Database	MEDical Literature Analysis and Retrieval System OnLINE

In stock of ZB MED Cologne/Königswinter

Uc I Zs.360: Show issues

Location:
Je nach Verfügbarkeit (siehe Angabe bei Bestand)
bis Jg. 2021: Bestellungen von Artikeln über das Online-Bestellformular
ab Jg. 2022: Lesesaal (EG)

Order via subito

Details ▾
- See ZB MED holdings
- Order with fees

To top

Full text online

More links

Kategorien

In stock of ZB MED Cologne/Königswinter

Order via subito

Full text online

More links

Kategorien

In stock of ZB MED Cologne/Königswinter

Order via subito

More links

Kategorien

Order via subito

Inter-library loan at ZB MED

More links

Kategorien

Order via subito

More links

Kategorien

Order via subito

More links

Kategorien

Order via subito

More links

Kategorien

Order via subito

More links

Kategorien

In stock of ZB MED Cologne/Königswinter

Order via subito

More links

Kategorien

Order via subito

Inter-library loan at ZB MED

More links

Kategorien

In stock of ZB MED Cologne/Königswinter

Order via subito