1
|
Wilhelm TI, Lewalter T, Reiser J, Werner J, Keil A, Oesterlein T, Gleirscher L, Tiemann K, Jilek C. Influence of Heart Rate and Change in Wavefront Direction through Pacing on Conduction Velocity and Voltage Amplitude in a Porcine Model: A High-Density Mapping Study. J Pers Med 2024; 14:473. [PMID: 38793055 PMCID: PMC11122149 DOI: 10.3390/jpm14050473] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/27/2024] [Revised: 04/04/2024] [Accepted: 04/23/2024] [Indexed: 05/26/2024] Open
Abstract
BACKGROUND Understanding the dynamics of conduction velocity (CV) and voltage amplitude (VA) is crucial in cardiac electrophysiology, particularly for substrate-based catheter ablations targeting slow conduction zones and low voltage areas. This study utilizes ultra-high-density mapping to investigate the impact of heart rate and pacing location on changes in the wavefront direction, CV, and VA of healthy pig hearts. METHODS We conducted in vivo electrophysiological studies on four healthy juvenile pigs, involving various pacing locations and heart rates. High-resolution electroanatomic mapping was performed during intrinsic normal sinus rhythm (NSR) and electrical pacing. The study encompassed detailed analyses at three levels: entire heart cavities, subregions, and localized 5-mm-diameter circular areas. Linear mixed-effects models were used to analyze the influence of heart rate and pacing location on CV and VA in different regions. RESULTS An increase in heart rate correlated with an increase in conduction velocity and a decrease in voltage amplitude. Pacing influenced conduction velocity and voltage amplitude. Pacing also influenced conduction velocity and voltage amplitude, with varying effects observed based on the pacing location within different heart cavities. Pacing from the right atrium (RA) decreased CV in all heart cavities. The overall CV and VA changes in the whole heart cavities were not uniformly reflected in all subregions and subregional CV and VA changes were not always reflected in the overall analysis. Overall, there was a notable variability in absolute CV and VA changes attributed to pacing. CONCLUSIONS Heart rate and pacing location influence CV and VA within healthy juvenile pig hearts. Subregion analysis suggests that specific regions of the heart cavities are more susceptible to pacing. High-resolution mapping aids in detecting regional changes, emphasizing the substantial physiological variations in CV and VA.
Collapse
Affiliation(s)
- Theresa Isabelle Wilhelm
- Peter-Osypka Heart Centre Munich, Internistisches Klinikum München Süd, 81379 Munich, Germany (K.T.)
- Eye Center, Medical Center, Faculty of Medicine, University of Freiburg, 79106 Freiburg, Germany
- Medical Graduate Center, TUM School of Medicine and Health, Technical University of Munich, 81675 Munich, Germany
| | - Thorsten Lewalter
- Peter-Osypka Heart Centre Munich, Internistisches Klinikum München Süd, 81379 Munich, Germany (K.T.)
- Department of Medicine, University of Bonn, 53127 Bonn, Germany
| | - Judith Reiser
- Center for Preclinical Research, TUM School of Medicine and Health, Technical University of Munich, 81675 Munich, Germany; (J.R.)
| | - Julia Werner
- Center for Preclinical Research, TUM School of Medicine and Health, Technical University of Munich, 81675 Munich, Germany; (J.R.)
| | - Andreas Keil
- Boston Scientific Medizintechnik GmbH, 40468 Düsseldorf, Germany
| | | | - Lukas Gleirscher
- Peter-Osypka Heart Centre Munich, Internistisches Klinikum München Süd, 81379 Munich, Germany (K.T.)
| | - Klaus Tiemann
- Peter-Osypka Heart Centre Munich, Internistisches Klinikum München Süd, 81379 Munich, Germany (K.T.)
- Department of Internal Medicine I, TUM School of Medicine and Health, Technical University of Munich, 81675 Munich, Germany
| | - Clemens Jilek
- Peter-Osypka Heart Centre Munich, Internistisches Klinikum München Süd, 81379 Munich, Germany (K.T.)
- Department of Internal Medicine I, TUM School of Medicine and Health, Technical University of Munich, 81675 Munich, Germany
| |
Collapse
|
2
|
Kodirov SA. Whole-cell patch-clamp recording and parameters. Biophys Rev 2023; 15:257-288. [PMID: 37124922 PMCID: PMC10133435 DOI: 10.1007/s12551-023-01055-8] [Citation(s) in RCA: 4] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/30/2023] [Accepted: 03/22/2023] [Indexed: 05/02/2023] Open
Abstract
The patch-clamp technique represents an electrophysiology type of method. This is one of several insightful approaches with five major configurations, namely a loose patch, cell-attached (also known as on-cell), whole-cell, inside-out, and outside-out modes. The patch-clamp method is more advanced compared to classical electrophysiology since it elucidates single-channel activation in a tiny portion of the membrane in addition to action potential (AP), junction potential (JP), endplate potential (EP), electrical coupling between two adjacent cells via Gap junction hemi-channels, excitatory/inhibitory postsynaptic potentials, and resting membrane potential (RMP). In fact, a malfunction of only one channel or even one component will alter AP amplitude or duration in vitro. If parameters are inferred appropriately and recordings are performed properly, the patch-clamp trace readouts and results are robust. The main hallmarks of currents via voltage-dependent calcium (Cav), hyperpolarization-activated cyclic nucleotide gated non-selective cation (HCN), inwardly rectifying potassium (Kir), voltage-dependent potassium (Kv), and voltage-dependent sodium (Nav) channels are similar and tractable among cells even when they are derived from evolutionary distinct organs and species. However, the size of the membrane area, where the functional subunits reside, and current magnitudes vary among cells of the same type. Therefore, dividing current magnitudes by cell capacitance- current density enables the estimate of functional and active channels relative to recorded cytoplasmic membrane area. Since the patch-clamp recordings can be performed in both current- and voltage-clamp modes, the action potential or spike durations can be adequately elucidated. Sometimes, optical methods are preferred to patch-clamp electrophysiology, but the obtained signals and traces are not robust. Finally, not only an alternans of AP durations, but also that of 'action potential shape' is observed with electrophysiology.
Collapse
Affiliation(s)
- Sodikdjon A. Kodirov
- Cardiovascular Division, Brigham and Women’s Hospital, Harvard Medical School, Boston, USA
- Instituto de Medicina Molecular, Universidade de Lisboa, Lisbon, Portugal
- Almazov Federal Medical Research Centre, Saint Petersburg, 197341 Russia
- Institute for Physiology and Pathophysiology, Johannes Kepler University, Linz, Austria
| |
Collapse
|
3
|
Tetsuka H, Pirrami L, Wang T, Demarchi D, Shin SR. Wirelessly Powered 3D Printed Hierarchical Biohybrid Robots with Multiscale Mechanical Properties. ADVANCED FUNCTIONAL MATERIALS 2022; 32:2202674. [PMID: 36313126 PMCID: PMC9603592 DOI: 10.1002/adfm.202202674] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/10/2023]
Abstract
The integration of flexible and stretchable electronics into biohybrid soft robotics can spur the development of new approaches to fabricate biohybrid soft machines, thus enabling a wide variety of innovative applications. Inspired by flexible and stretchable wireless-based bioelectronic devices, we have developed untethered biohybrid soft robots that can execute swimming motions, which are remotely controllable by the wireless transmission of electrical power into a cell simulator. To this end, wirelessly-powered, stretchable, and lightweight cell stimulators were designed to be integrated into muscle bodies without impeding the robots' underwater swimming abilities. The cell stimulators function by generating controlled monophasic pulses of up to ∼9 V in biological environments. By differentiating induced pluripotent stem cell-derived cardiomyocytes (iPSC-CMs) directly on the cell stimulators using an accordion-inspired, three-dimensional (3D) printing construct, we have replicated the native myofiber architecture with comparable robustness and enhanced contractibility. Wirelessly modulated electrical frequencies enabled us to control the speed and direction of the biohybrid soft robots. A maximum locomotion speed of ∼580 μm/s was achieved in robots possessing a large body size by adjusting the pacing frequency. This innovative approach will provide a platform for building untethered and biohybrid systems for various biomedical applications.
Collapse
Affiliation(s)
- Hiroyuki Tetsuka
- Division of Engineering in Medicine, Department of Medicine, Brigham and Women's Hospital, Harvard Medical School, 65 Lansdowne Street, Cambridge, Massachusetts, 02139 USA
- Future Mobility Research Department, Toyota Research Institute of North America, Toyota Motor North America, 1555 Woodridge Avenue, Ann Arbor, Michigan, 48105 USA
| | - Lorenzo Pirrami
- iPrint Institute, HEIA-FR, HES-SO University of Applied Sciences and Arts Western Switzerland, Fribourg-1700, Switzerland
| | - Ting Wang
- Division of Engineering in Medicine, Department of Medicine, Brigham and Women's Hospital, Harvard Medical School, 65 Lansdowne Street, Cambridge, Massachusetts, 02139 USA
| | - Danilo Demarchi
- Department of Electronics and Telecommunications, Politecnico di Torino, Turin 10129, Italy
| | - Su Ryon Shin
- Division of Engineering in Medicine, Department of Medicine, Brigham and Women's Hospital, Harvard Medical School, 65 Lansdowne Street, Cambridge, Massachusetts, 02139 USA
| |
Collapse
|
4
|
Nayir S, Lacour SP, Kucera JP. Active force generation contributes to the complexity of spontaneous activity and to the response to stretch of murine cardiomyocyte cultures. J Physiol 2022; 600:3287-3312. [PMID: 35679256 PMCID: PMC9541716 DOI: 10.1113/jp283083] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/10/2022] [Accepted: 06/01/2022] [Indexed: 11/17/2022] Open
Abstract
Abstract Cardiomyocyte cultures exhibit spontaneous electrical and contractile activity, as in a natural cardiac pacemaker. In such preparations, beat rate variability exhibits features similar to those of heart rate variability in vivo. Mechanical deformations and forces feed back on the electrical properties of cardiomyocytes, but it is not fully elucidated how this mechano‐electrical interplay affects beating variability in such preparations. Using stretchable microelectrode arrays, we assessed the effects of the myosin inhibitor blebbistatin and the non‐selective stretch‐activated channel blocker streptomycin on beating variability and on the response of neonatal or fetal murine ventricular cell cultures against deformation. Spontaneous electrical activity was recorded without stretch and upon predefined deformation protocols (5% uniaxial and 2% equibiaxial strain, applied repeatedly for 1 min every 3 min). Without stretch, spontaneous activity originated from the edge of the preparations, and its site of origin switched frequently in a complex manner across the cultures. Blebbistatin did not change mean beat rate, but it decreased the spatial complexity of spontaneous activity. In contrast, streptomycin did not exert any manifest effects. During the deformation protocols, beat rate increased transiently upon stretch but, paradoxically, also upon release. Blebbistatin attenuated the response to stretch, whereas this response was not affected by streptomycin. Therefore, our data support the notion that in a spontaneously firing network of cardiomyocytes, active force generation, rather than stretch‐activated channels, is involved mechanistically in the complexity of the spatiotemporal patterns of spontaneous activity and in the stretch‐induced acceleration of beating.
![]() Key points Monolayer cultures of cardiac cells exhibit spontaneous electrical and contractile activity, as in a natural cardiac pacemaker. Beating variability in these preparations recapitulates the power‐law behaviour of heart rate variability in vivo. However, the effects of mechano‐electrical feedback on beating variability are not yet fully understood. Using stretchable microelectrode arrays, we examined the effects of the contraction uncoupler blebbistatin and the non‐specific stretch‐activated channel blocker streptomycin on beating variability and on stretch‐induced changes of beat rate. Without stretch, blebbistatin decreased the spatial complexity of beating variability, whereas streptomycin had no effects. Both stretch and release increased beat rate transiently; blebbistatin attenuated the increase of beat rate upon stretch, whereas streptomycin had no effects. Active force generation contributes to the complexity of spatiotemporal patterns of beating variability and to the increase of beat rate upon mechanical deformation. Our study contributes to the understanding of how mechano‐electrical feedback influences heart rate variability.
Collapse
Affiliation(s)
- Seyma Nayir
- Department of Physiology, University of Bern, Bern, Switzerland
| | | | - Jan P Kucera
- Department of Physiology, University of Bern, Bern, Switzerland
| |
Collapse
|
5
|
Nakanishi H, Lee JK, Miwa K, Masuyama K, Yasutake H, Li J, Tomoyama S, Honda Y, Deguchi J, Tsujimoto S, Hidaka K, Miyagawa S, Sawa Y, Komuro I, Sakata Y. Geometrical Patterning and Constituent Cell Heterogeneity Facilitate Electrical Conduction Disturbances in a Human Induced Pluripotent Stem Cell-Based Platform: An In vitro Disease Model of Atrial Arrhythmias. Front Physiol 2019; 10:818. [PMID: 31316396 PMCID: PMC6610482 DOI: 10.3389/fphys.2019.00818] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/08/2019] [Accepted: 06/11/2019] [Indexed: 01/09/2023] Open
Abstract
Ectopic foci from pulmonary veins (PVs) comprise the main trigger associated with the initiation of atrial fibrillation (AF). An abrupt anatomical narrow-to-wide transition, modeled as in vitro geometrical patterning with similar configuration in the present study, is located at the junction of PVs and the left atrium (LA). Complex cellular composition, i.e., constituent cell heterogeneity, is also observed in PVs and the PVs-LA junction. High frequency triggers accompanied with anatomical irregularity and constituent cell heterogeneity provoke impaired conduction, a prerequisite for AF genesis. However, few experiments investigating the effects of these factors on electrophysiological properties using human-based cardiomyocytes (CMs) with atrial properties have been reported. The aim of the current study was to estimate whether geometrical patterning and constituent cell heterogeneity under high frequency stimuli undergo conduction disturbance utilizing an in vitro two-dimensional (2D) monolayer preparation consisting of atrial-like CMs derived from human induced pluripotent stem cells (hiPSCs) and atrial fibroblasts (Fbs). We induced hiPSCs into atrial-like CMs using a directed cardiac differentiation protocol with the addition of all-trans retinoic acid (ATRA). The atrial-like hiPSC-derived CMs (hiPSC-CMs) and atrial Fbs were transferred in defined ratios (CMs/Fbs: 100%/0% or 70%/30%) on manually fabricated plates with or without geometrical patterning imitating the PVs-LA junction. High frequency field stimulation emulating repetitive ectopic foci originated in PVs were delivered, and the electrical propagation was assessed by optical mapping. We generated high purity CMs with or without the ATRA application. ATRA-treated hiPSC-CMs exhibited significantly higher atrial-specific properties by immunofluorescence staining, gene expression patterns, and optical action potential parameters than those of ATRA-untreated hiPSC-CMs. Electrical stimuli at a higher frequency preferentially induced impaired electrical conduction on atrial-like hiPSC-CMs monolayer preparations with an abrupt geometrical transition than on those with uniform geometry. Additionally, the application of human atrial Fbs to the geometrically patterned atrial-like hiPSC-CMs tended to further deteriorate the integrity of electrical conduction compared with those using the atrial-like hiPSC-CM alone preparations. Thus, geometrical narrow-to-wide patterning under high frequency stimuli preferentially jeopardized electrical conduction within in vitro atrial-like hiPSC-CM monolayers. Constituent cell heterogeneity represented by atrial Fbs also contributed to the further deterioration of conduction stability.
Collapse
Affiliation(s)
- Hiroyuki Nakanishi
- Department of Cardiovascular Medicine, Graduate School of Medicine, Osaka University, Suita, Japan
| | - Jong-Kook Lee
- Department of Advanced Cardiovascular Regenerative Medicine, Graduate School of Medicine, Osaka University, Suita, Japan
| | - Keiko Miwa
- Department of Mechanical Engineering, Kyushu University, Fukuoka, Japan
| | - Kiyoshi Masuyama
- Department of Cardiovascular Medicine, Graduate School of Medicine, Osaka University, Suita, Japan
| | - Hideki Yasutake
- Department of Cardiovascular Medicine, Graduate School of Medicine, Osaka University, Suita, Japan
| | - Jun Li
- Department of Cardiovascular Medicine, Graduate School of Medicine, Osaka University, Suita, Japan
| | - Satoki Tomoyama
- Department of Cardiovascular Medicine, Graduate School of Medicine, Osaka University, Suita, Japan
| | - Yayoi Honda
- Preclinical Research Unit, Sumitomo Dainippon Pharma Co., Ltd., Osaka, Japan
| | - Jiro Deguchi
- Preclinical Research Unit, Sumitomo Dainippon Pharma Co., Ltd., Osaka, Japan
| | - Shinji Tsujimoto
- Regenerative & Cellular Medicine Office, Sumitomo Dainippon Pharma Co., Ltd., Osaka, Japan
| | - Kyoko Hidaka
- Department of Advanced Cardiovascular Regenerative Medicine, Graduate School of Medicine, Osaka University, Suita, Japan.,Center for Fundamental Education, The University of Kitakyushu, Kitakyushu, Japan
| | - Shigeru Miyagawa
- Department of Cardiovascular Surgery, Graduate School of Medicine, Osaka University, Suita, Japan
| | - Yoshiki Sawa
- Department of Cardiovascular Surgery, Graduate School of Medicine, Osaka University, Suita, Japan
| | - Issei Komuro
- Department of Cardiovascular Medicine, Graduate School of Medicine, The University of Tokyo, Tokyo, Japan
| | - Yasushi Sakata
- Department of Cardiovascular Medicine, Graduate School of Medicine, Osaka University, Suita, Japan
| |
Collapse
|
6
|
Imboden M, de Coulon E, Poulin A, Dellenbach C, Rosset S, Shea H, Rohr S. High-speed mechano-active multielectrode array for investigating rapid stretch effects on cardiac tissue. Nat Commun 2019; 10:834. [PMID: 30783104 PMCID: PMC6381132 DOI: 10.1038/s41467-019-08757-2] [Citation(s) in RCA: 25] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/11/2018] [Accepted: 01/24/2019] [Indexed: 11/25/2022] Open
Abstract
Systematic investigations of the effects of mechano-electric coupling (MEC) on cellular cardiac electrophysiology lack experimental systems suitable to subject tissues to in-vivo like strain patterns while simultaneously reporting changes in electrical activation. Here, we describe a self-contained motor-less device (mechano-active multielectrode-array, MaMEA) that permits the assessment of impulse conduction along bioengineered strands of cardiac tissue in response to dynamic strain cycles. The device is based on polydimethylsiloxane (PDMS) cell culture substrates patterned with dielectric actuators (DEAs) and compliant gold ion-implanted extracellular electrodes. The DEAs induce uniaxial stretch and compression in defined regions of the PDMS substrate at selectable amplitudes and with rates up to 18 s−1. Conduction along cardiomyocyte strands was found to depend linearly on static strain according to cable theory while, unexpectedly, being completely independent on strain rates. Parallel operation of multiple MaMEAs provides for systematic high-throughput investigations of MEC during spatially patterned mechanical perturbations mimicking in-vivo conditions. While strain is known to affect cardiac electrophysiology, experimental systems to interrogate the effect of rapid strain cycles on cardiac tissue are lacking. Here the authors introduce a multielectrode array that can induce rapid dynamic strain cycles on cardiomyocyte strands and see effects of strain amplitude but not strain rate on impulse conduction.
Collapse
Affiliation(s)
- Matthias Imboden
- Soft Transducers Laboratory, École Polytechnique Fédérale de Lausanne (EPFL), 2002, Neuchâtel, Switzerland. .,Department of Physiology, University of Bern, Bühlplatz 5, 3012, Bern, Switzerland.
| | - Etienne de Coulon
- Department of Physiology, University of Bern, Bühlplatz 5, 3012, Bern, Switzerland
| | - Alexandre Poulin
- Soft Transducers Laboratory, École Polytechnique Fédérale de Lausanne (EPFL), 2002, Neuchâtel, Switzerland
| | - Christian Dellenbach
- Department of Physiology, University of Bern, Bühlplatz 5, 3012, Bern, Switzerland
| | - Samuel Rosset
- Soft Transducers Laboratory, École Polytechnique Fédérale de Lausanne (EPFL), 2002, Neuchâtel, Switzerland
| | - Herbert Shea
- Soft Transducers Laboratory, École Polytechnique Fédérale de Lausanne (EPFL), 2002, Neuchâtel, Switzerland
| | - Stephan Rohr
- Department of Physiology, University of Bern, Bühlplatz 5, 3012, Bern, Switzerland.
| |
Collapse
|
7
|
Buccarello A, Azzarito M, Michoud F, Lacour SP, Kucera JP. Uniaxial strain of cultured mouse and rat cardiomyocyte strands slows conduction more when its axis is parallel to impulse propagation than when it is perpendicular. Acta Physiol (Oxf) 2018; 223:e13026. [PMID: 29282897 DOI: 10.1111/apha.13026] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/15/2017] [Revised: 12/14/2017] [Accepted: 12/21/2017] [Indexed: 11/28/2022]
Abstract
AIM Cardiac tissue deformation can modify tissue resistance, membrane capacitance and ion currents and hence cause arrhythmogenic slow conduction. Our aim was to investigate whether uniaxial strain causes different changes in conduction velocity (θ) when the principal strain axis is parallel vs perpendicular to impulse propagation. METHODS Cardiomyocyte strands were cultured on stretchable custom microelectrode arrays, and θ was determined during steady-state pacing. Uniaxial strain (5%) with principal axis parallel (orthodromic) or perpendicular (paradromic) to propagation was applied for 1 minute and controlled by imaging a grid of markers. The results were analysed in terms of cable theory. RESULTS Both types of strain induced immediate changes of θ upon application and release. In material coordinates, orthodromic strain decreased θ significantly more (P < .001) than paradromic strain (2.2 ± 0.5% vs 1.0 ± 0.2% in n = 8 mouse cardiomyocyte cultures, 2.3 ± 0.4% vs 0.9 ± 0.5% in n = 4 rat cardiomyocyte cultures, respectively). The larger effect of orthodromic strain can be explained by the increase in axial myoplasmic resistance, which is not altered by paradromic strain. Thus, changes in tissue resistance substantially contributed to the changes of θ during strain, in addition to other influences (eg stretch-activated channels). Besides these immediate effects, the application of strain also consistently initiated a slow progressive decrease in θ and a slow recovery of θ upon release. CONCLUSION Changes in cardiac conduction velocity caused by acute stretch do not only depend on the magnitude of strain but also on its orientation relative to impulse propagation. This dependence is due to different effects on tissue resistance.
Collapse
Affiliation(s)
- A. Buccarello
- Department of Physiology; University of Bern; Bern Switzerland
| | - M. Azzarito
- Department of Physiology; University of Bern; Bern Switzerland
| | - F. Michoud
- Bertarelli Foundation Chair in Neuroprosthetic Technology; Laboratory for Soft Bioelectronic Interfaces; Institute of Microengineering; Institute of Bioengineering; Centre for Neuroprosthetics; École Polytechnique Fédérale de Lausanne (EPFL); Geneva Switzerland
| | - S. P. Lacour
- Bertarelli Foundation Chair in Neuroprosthetic Technology; Laboratory for Soft Bioelectronic Interfaces; Institute of Microengineering; Institute of Bioengineering; Centre for Neuroprosthetics; École Polytechnique Fédérale de Lausanne (EPFL); Geneva Switzerland
| | - J. P. Kucera
- Department of Physiology; University of Bern; Bern Switzerland
| |
Collapse
|
8
|
Li Y, Zhang X, Zhang C, Zhang X, Li Y, Qi Z, Szeto C, Tang M, Peng Y, Molkentin JD, Houser SR, Xie M, Chen X. Increasing T-type calcium channel activity by β-adrenergic stimulation contributes to β-adrenergic regulation of heart rates. J Physiol 2018; 596:1137-1151. [PMID: 29274077 PMCID: PMC5878229 DOI: 10.1113/jp274756] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/09/2017] [Accepted: 12/13/2017] [Indexed: 11/08/2022] Open
Abstract
KEY POINTS Cav3.1 T-type Ca2+ channel current (ICa-T ) contributes to heart rate genesis but is not known to contribute to heart rate regulation by the sympathetic/β-adrenergic system (SAS). We show that the loss of Cav3.1 makes the beating rates of the heart in vivo and perfused hearts ex vivo, as well as sinoatrial node cells, less sensitive to β-adrenergic stimulation; it also renders less conduction acceleration through the atrioventricular node by β-adrenergic stimulation. Increasing Cav3.1 in cardiomyocytes has the opposite effects. ICa-T in sinoatrial nodal cells can be upregulated by β-adrenergic stimulation. The results of the present study add a new contribution to heart rate regulation by the SAS system and provide potential new mechanisms for the dysregulation of heart rate and conduction by the SAS in the heart. T-type Ca2+ channel can be a target for heart disease treatments that aim to slow down the heart rate ABSTRACT: Cav3.1 (α1G ) T-type Ca2+ channel (TTCC) is expressed in mouse sinoatrial node cells (SANCs) and atrioventricular (AV) nodal cells and contributes to heart rate (HR) genesis and AV conduction. However, its role in HR regulation and AV conduction acceleration by the β-adrenergic system (SAS) is unclear. In the present study, L- (ICa-L ) and T-type (ICa-T ) Ca2+ currents were recorded in SANCs from Cav3.1 transgenic (TG) and knockout (KO), and control mice. ICa-T was absent in KO SANCs but enhanced in TG SANCs. In anaesthetized animals, different doses of isoproterenol (ISO) were infused via the jugular vein and the HR was recorded. The EC50 of the HR response to ISO was lower in TG mice but higher in KO mice, and the maximal percentage of HR increase by ISO was greater in TG mice but less in KO mice. In Langendorff-perfused hearts, ISO increased HR and shortened PR intervals to a greater extent in TG but to a less extent in KO hearts. KO SANCs had significantly slower spontaneous beating rates than control SANCs before and after ISO; TG SANCs had similar basal beating rates as control SANCs probably as a result of decreased ICa-L but a greater response to ISO than control SANCs. ICa-T in SANCs was significantly increased by ISO. ICa-T upregulation by β-adrenergic stimulation contributes to HR and conduction regulation by the SAS. TTCC can be a target for slowing the HR.
Collapse
MESH Headings
- Adrenergic Agents/pharmacology
- Animals
- Arrhythmias, Cardiac/drug therapy
- Arrhythmias, Cardiac/metabolism
- Arrhythmias, Cardiac/pathology
- Calcium Channels, T-Type/physiology
- Heart Rate/drug effects
- Heart Rate/physiology
- Mice
- Mice, Inbred C57BL
- Mice, Knockout
- Mice, Transgenic
- Myocytes, Cardiac/cytology
- Myocytes, Cardiac/drug effects
- Myocytes, Cardiac/metabolism
- Receptors, Adrenergic, beta/metabolism
- Signal Transduction
- Sinoatrial Node/cytology
- Sinoatrial Node/drug effects
- Sinoatrial Node/metabolism
Collapse
Affiliation(s)
- Yingxin Li
- Cardiovascular Research Center and Department of PhysiologyTemple University School of Medicine3500 North Broad StreetPhiladelphiaPAUSA
| | - Xiaoxiao Zhang
- Cardiovascular Research Center and Department of PhysiologyTemple University School of Medicine3500 North Broad StreetPhiladelphiaPAUSA
- Department of Ultrasound, Union Hospital, Tongji Medical College, Huazhong University of Science and TechnologyHubei Provincial Key Laboratory of Molecular ImagineWuhanChina
| | - Chen Zhang
- Cardiovascular Research Center and Department of PhysiologyTemple University School of Medicine3500 North Broad StreetPhiladelphiaPAUSA
| | - Xiaoying Zhang
- Cardiovascular Research Center and Department of PhysiologyTemple University School of Medicine3500 North Broad StreetPhiladelphiaPAUSA
| | - Ying Li
- Cardiovascular Research Center and Department of PhysiologyTemple University School of Medicine3500 North Broad StreetPhiladelphiaPAUSA
- The General Hospital of The PLA Rocket ForceBeijingChina
- Institute of Burn Research, Southwest Hospital, State Key Laboratory of TraumaThird Military Medical UniversityChongqingChina
| | - Zhao Qi
- Cardiovascular Research Center and Department of PhysiologyTemple University School of Medicine3500 North Broad StreetPhiladelphiaPAUSA
| | - Christopher Szeto
- Cardiovascular Research Center and Department of PhysiologyTemple University School of Medicine3500 North Broad StreetPhiladelphiaPAUSA
| | - Mingxin Tang
- Cardiovascular Research Center and Department of PhysiologyTemple University School of Medicine3500 North Broad StreetPhiladelphiaPAUSA
| | - Yizhi Peng
- Institute of Burn Research, Southwest Hospital, State Key Laboratory of TraumaThird Military Medical UniversityChongqingChina
| | - Jeffery D. Molkentin
- Howard Hughes Medical Institute & Cincinnati Children's Hospital Medical CenterCincinnatiOHUSA
| | - Steven R. Houser
- Cardiovascular Research Center and Department of PhysiologyTemple University School of Medicine3500 North Broad StreetPhiladelphiaPAUSA
| | - Mingxing Xie
- Department of Ultrasound, Union Hospital, Tongji Medical College, Huazhong University of Science and TechnologyHubei Provincial Key Laboratory of Molecular ImagineWuhanChina
| | - Xiongwen Chen
- Cardiovascular Research Center and Department of PhysiologyTemple University School of Medicine3500 North Broad StreetPhiladelphiaPAUSA
| |
Collapse
|
9
|
Kucera JP, Rohr S, Kleber AG. Microstructure, Cell-to-Cell Coupling, and Ion Currents as Determinants of Electrical Propagation and Arrhythmogenesis. Circ Arrhythm Electrophysiol 2017; 10:CIRCEP.117.004665. [DOI: 10.1161/circep.117.004665] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/21/2017] [Accepted: 07/17/2017] [Indexed: 11/16/2022]
Affiliation(s)
- Jan P. Kucera
- From the Department of Physiology, University of Bern, Switzerland (J.P.K., S.R.); and the Department of Pathology, Harvard Medical School, Boston, MA (A.G.K.)
| | - Stephan Rohr
- From the Department of Physiology, University of Bern, Switzerland (J.P.K., S.R.); and the Department of Pathology, Harvard Medical School, Boston, MA (A.G.K.)
| | - Andre G. Kleber
- From the Department of Physiology, University of Bern, Switzerland (J.P.K., S.R.); and the Department of Pathology, Harvard Medical School, Boston, MA (A.G.K.)
| |
Collapse
|
10
|
Jabr RI, Hatch FS, Salvage SC, Orlowski A, Lampe PD, Fry CH. Regulation of gap junction conductance by calcineurin through Cx43 phosphorylation: implications for action potential conduction. Pflugers Arch 2016; 468:1945-1955. [PMID: 27757582 PMCID: PMC5138272 DOI: 10.1007/s00424-016-1885-7] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/08/2016] [Revised: 09/04/2016] [Accepted: 09/22/2016] [Indexed: 10/27/2022]
Abstract
Cardiac arrhythmias are associated with raised intracellular [Ca2+] and slowed action potential conduction caused by reduced gap junction (GJ) electrical conductance (Gj). Ventricular GJs are composed of connexin proteins (Cx43), with Gj determined by Cx43 phosphorylation status. Connexin phosphorylation is an interplay between protein kinases and phosphatases but the precise pathways are unknown. We aimed to identify key Ca2+-dependent phosphorylation sites on Cx43 that regulate cardiac gap junction conductance and action potential conduction velocity. We investigated the role of the Ca2+-dependent phosphatase, calcineurin. Intracellular [Ca2+] was raised in guinea-pig myocardium by a low-Na solution or increased stimulation. Conduction velocity and Gj were measured in multicellular strips. Phosphorylation of Cx43 serine residues (S365 and S368) and of the intermediary regulator I1 at threonine35 was measured by Western blot. Measurements were made in the presence and absence of inhibitors to calcineurin, I1 or protein phosphatase-1 and phosphatase-2.Raised [Ca2+]i decreased Gj, reduced Cx43 phosphorylation at S365 and increased it at S368; these changes were reversed by calcineurin inhibitors. Cx43-S368 phosphorylation was reversed by the protein kinase C inhibitor chelerythrine. Raised [Ca2+]i also decreased I1 phosphorylation, also prevented by calcineurin inhibitors, to increase activity of the Ca2+-independent phosphatase, PPI. The PP1 inhibitor, tautomycin, prevented Cx43-365 dephosphorylation, Cx43-S368 phosphorylation and Gj reduction in raised [Ca2+]i. PP2A had no role. Conduction velocity was reduced by raised [Ca2+]i and reversed by calcineurin inhibitors. Reduced action potential conduction and Gj in raised [Ca2+] are regulated by calcineurin-dependent Cx43-S365 phosphorylation, leading to Cx43-S368 dephosphorylation. The calcineurin action is indirect, via I1 dephosphorylation and subsequent activation of PP1.
Collapse
Affiliation(s)
- Rita I Jabr
- School of Biosciences and Medicine, Faculty of Health and Medical Sciences, University of Surrey, Guildford, GU2 7XH, UK. .,Institute of Cardiovascular Research, Ashford & St Peter's NHS Foundation Trust, Surrey, Chertsey, KT16 0PZ, UK.
| | - Fiona S Hatch
- School of Biosciences and Medicine, Faculty of Health and Medical Sciences, University of Surrey, Guildford, GU2 7XH, UK
| | - Samantha C Salvage
- School of Biosciences and Medicine, Faculty of Health and Medical Sciences, University of Surrey, Guildford, GU2 7XH, UK
| | - Alejandro Orlowski
- School of Biosciences and Medicine, Faculty of Health and Medical Sciences, University of Surrey, Guildford, GU2 7XH, UK
| | - Paul D Lampe
- Fred Hutchinson Cancer Research Center, 1100 Fairview Avenue North, Seattle, WA, 98109, USA
| | - Christopher H Fry
- Institute of Cardiovascular Research, Ashford & St Peter's NHS Foundation Trust, Surrey, Chertsey, KT16 0PZ, UK.,School of Physiology, Pharmacology & Neuroscience, University of Bristol, BS8 1TD, Bristol, UK
| |
Collapse
|
11
|
TRIBULOVA N, KNEZL V, SZEIFFOVA BACOVA B, EGAN BENOVA T, VICZENCZOVA C, GONÇALVESOVA E, SLEZAK J. Disordered Myocardial Ca2+ Homeostasis Results in Substructural Alterations That May Promote Occurrence of Malignant Arrhythmias. Physiol Res 2016; 65 Suppl 1:S139-48. [DOI: 10.33549/physiolres.933388] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022] Open
Abstract
We aimed to determine the impact of Ca2+-related disorders induced in intact animal hearts on ultrastructure of the cardiomyocytes prior to occurrence of severe arrhythmias. Three types of acute experiments were performed that are known to be accompanied by disturbances in Ca2+ handling. Langedorff-perfused rat or guinea pig hearts subjected to K+-deficient perfusion to induce ventricular fibrillation (VF), burst atrial pacing to induce atrial fibrillation (AF) and open chest pig heart exposed to intramyocardial noradrenaline infusion to induce ventricular tachycardia (VT). Tissue samples for electron microscopic examination were taken during basal condition, prior and during occurrence of malignant arrhythmias. Cardiomyocyte alterations preceding occurrence of arrhythmias consisted of non-uniform sarcomere shortening, disruption of myofilaments and injury of mitochondria that most likely reflected cytosolic Ca2+ disturbances and Ca2+ overload. These disorders were linked with non-uniform pattern of neighboring cardiomyocytes and dissociation of adhesive junctions suggesting defects in cardiac cell-to-cell coupling. Our findings identified heterogeneously distributed high [Ca2+]i-induced subcellular injury of the cardiomyocytes and their junctions as a common feature prior occurrence of VT, VF or AF. In conclusion, there is a link between Ca2+-related disorders in contractility and coupling of the cardiomyocytes pointing out a novel paradigm implicated in development of severe arrhythmias.
Collapse
Affiliation(s)
- N. TRIBULOVA
- Institute for Heart Research, Slovak Academy of Sciences, Bratislava, Slovak Republic
| | | | | | | | | | | | | |
Collapse
|
12
|
Kucera JP, Prudat Y, Marcu IC, Azzarito M, Ullrich ND. Slow conduction in mixed cultured strands of primary ventricular cells and stem cell-derived cardiomyocytes. Front Cell Dev Biol 2015; 3:58. [PMID: 26442264 PMCID: PMC4585316 DOI: 10.3389/fcell.2015.00058] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/13/2015] [Accepted: 09/09/2015] [Indexed: 11/30/2022] Open
Abstract
Modern concepts for the treatment of myocardial diseases focus on novel cell therapeutic strategies involving stem cell-derived cardiomyocytes (SCMs). However, functional integration of SCMs requires similar electrophysiological properties as primary cardiomyocytes (PCMs) and the ability to establish intercellular connections with host myocytes in order to contribute to the electrical and mechanical activity of the heart. The aim of this project was to investigate the properties of cardiac conduction in a co-culture approach using SCMs and PCMs in cultured cell strands. Murine embryonic SCMs were pooled with fetal ventricular cells and seeded in predefined proportions on microelectrode arrays to form patterned strands of mixed cells. Conduction velocity (CV) was measured during steady state pacing. SCM excitability was estimated from action potentials measured in single cells using the patch clamp technique. Experiments were complemented with computer simulations of conduction using a detailed model of cellular architecture in mixed cell strands. CV was significantly lower in strands composed purely of SCMs (5.5 ± 1.5 cm/s, n = 11) as compared to PCMs (34.9 ± 2.9 cm/s, n = 21) at similar refractoriness (100% SCMs: 122 ± 25 ms, n = 9; 100% PCMs: 139 ± 67 ms, n = 14). In mixed strands combining both cell types, CV was higher than in pure SCMs strands, but always lower than in 100% PCM strands. Computer simulations demonstrated that both intercellular coupling and electrical excitability limit CV. These data provide evidence that in cultures of murine ventricular cardiomyocytes, SCMs cannot restore CV to control levels resulting in slow conduction, which may lead to reentry circuits and arrhythmias.
Collapse
Affiliation(s)
- Jan P Kucera
- Department of Physiology, University of Bern Bern, Switzerland
| | - Yann Prudat
- Department of Physiology, University of Bern Bern, Switzerland
| | - Irene C Marcu
- Department of Physiology, University of Bern Bern, Switzerland ; Department of Physiology and Pathophysiology, Heidelberg University Heidelberg, Germany
| | | | - Nina D Ullrich
- Department of Physiology and Pathophysiology, Heidelberg University Heidelberg, Germany
| |
Collapse
|
13
|
Wang YT, Gu S, Rollins AM, Jenkins MW. Optical mapping of optically paced embryonic hearts. ANNUAL INTERNATIONAL CONFERENCE OF THE IEEE ENGINEERING IN MEDICINE AND BIOLOGY SOCIETY. IEEE ENGINEERING IN MEDICINE AND BIOLOGY SOCIETY. ANNUAL INTERNATIONAL CONFERENCE 2015; 2013:1623-6. [PMID: 24110014 DOI: 10.1109/embc.2013.6609827] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
Conduction maps of early embryonic hearts with optical mapping point to heterogeneous conduction patterns that quickly evolve over time. In adult hearts, electrical pacing is utilized to determine the anisotropy of the conduction patterns and the susceptibility of the tissue to arrhythmias. However, studying electrophysiology in developing hearts is limited due to their size. Electrical pacing creates an electrical artifact that obscures recordings from the entirety of early embryonic hearts. In this study, optical point stimulation using a 1440-nm near-infrared diode laser with a 12-µm diameter beam waist was used to pace embryonic quail hearts. Electrical activity was recorded across the surface of the embryonic hearts by high resolution optical mapping using di-4-ANEPPS and cytochalasin D. While there were no electrical artifacts produced by the optical point stimulation, an optical artifact due to thermal lensing did obscure the optical mapping near the point of stimulation. The optical artifact can be minimized by optimizing the stimulation parameters to minimize the energy deposited and can be further reduced by signal processing. Despite the presence of the optical artifact, the electrical activity over the majority of the heart can be obtained.
Collapse
|
14
|
Krul SP, Meijborg VM, Berger WR, Linnenbank AC, Driessen AH, van Boven WJ, Wilde AA, de Bakker JM, Coronel R, de Groot JR. Disparate response of high-frequency ganglionic plexus stimulation on sinus node function and atrial propagation in patients with atrial fibrillation. Heart Rhythm 2014; 11:1743-51. [DOI: 10.1016/j.hrthm.2014.04.041] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/12/2014] [Indexed: 11/29/2022]
|
15
|
Prudat Y, Kucera JP. Nonlinear behaviour of conduction and block in cardiac tissue with heterogeneous expression of connexin 43. J Mol Cell Cardiol 2014; 76:46-54. [PMID: 25128085 DOI: 10.1016/j.yjmcc.2014.07.019] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/09/2014] [Revised: 07/25/2014] [Accepted: 07/31/2014] [Indexed: 11/18/2022]
Abstract
Altered gap junctional coupling potentiates slow conduction and arrhythmias. To better understand how heterogeneous connexin expression affects conduction at the cellular scale, we investigated conduction in tissue consisting of two cardiomyocyte populations expressing different connexin levels. Conduction was mapped using microelectrode arrays in cultured strands of foetal murine ventricular myocytes with predefined contents of connexin 43 knockout (Cx43KO) cells. Corresponding computer simulations were run in randomly generated two-dimensional tissues mimicking the cellular architecture of the strands. In the cultures, the relationship between conduction velocity (CV) and Cx43KO cell content was nonlinear. CV first decreased significantly when Cx43KO content was increased from 0 to 50%. When the Cx43KO content was ≥60%, CV became comparable to that in 100% Cx43KO strands. Co-culturing Cx43KO and wild-type cells also resulted in significantly more heterogeneous conduction patterns and in frequent conduction blocks. The simulations replicated this behaviour of conduction. For Cx43KO contents of 10-50%, conduction was slowed due to wavefront meandering between Cx43KO cells. For Cx43KO contents ≥60%, clusters of remaining wild-type cells acted as electrical loads that impaired conduction. For Cx43KO contents of 40-60%, conduction exhibited fractal characteristics, was prone to block, and was more sensitive to changes in ion currents compared to homogeneous tissue. In conclusion, conduction velocity and stability behave in a nonlinear manner when cardiomyocytes expressing different connexin amounts are combined. This behaviour results from heterogeneous current-to-load relationships at the cellular level. Such behaviour is likely to be arrhythmogenic in various clinical contexts in which gap junctional coupling is heterogeneous.
Collapse
Affiliation(s)
- Yann Prudat
- Department of Physiology, University of Bern, Bühlplatz 5, CH-3012 Bern, Switzerland.
| | - Jan P Kucera
- Department of Physiology, University of Bern, Bühlplatz 5, CH-3012 Bern, Switzerland.
| |
Collapse
|
16
|
Xu B, Jacquir S, Laurent G, Bilbault JM, Binczak S. Phase space reconstruction of an experimental model of cardiac field potential in normal and arrhythmic conditions. ANNUAL INTERNATIONAL CONFERENCE OF THE IEEE ENGINEERING IN MEDICINE AND BIOLOGY SOCIETY. IEEE ENGINEERING IN MEDICINE AND BIOLOGY SOCIETY. ANNUAL INTERNATIONAL CONFERENCE 2013; 2013:3274-7. [PMID: 24110427 DOI: 10.1109/embc.2013.6610240] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Cardiac arrhythmias are one of the most important death causes in the world. Compared to the numerical models, the experimental ones provide a more realistic tool to study the mechanisms of cardiac arrhythmias. The in vitro culture of cardiac cells developed on the Multi-Electrodes Array (MEA) constitutes a suitable model in this context. The extracellular field potential (EFP) acquired from the MEA can be used to measure the electrophysiological parameters of action potential. In this article, the stability of this experimental model is investigated using the phase space reconstruction in normal and in arrhythmia conditions. The results show that the embedding dimension of signal EFP changed slightly in both cases (normal conditions and arrhythmia). The parameter time lag τ in the normal conditions is lower than in the arrhythmia. The shape of attractors remains similar but disturbed in case of arrhythmia compared to the normal conditions.
Collapse
|
17
|
Kelly A, Ghouri IA, Kemi OJ, Bishop MJ, Bernus O, Fenton FH, Myles RC, Burton FL, Smith GL. Subepicardial action potential characteristics are a function of depth and activation sequence in isolated rabbit hearts. Circ Arrhythm Electrophysiol 2013; 6:809-17. [PMID: 23733913 DOI: 10.1161/circep.113.000334] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
BACKGROUND Electric excitability in the ventricular wall is influenced by cellular electrophysiology and passive electric properties of the myocardium. Action potential (AP) rise time, an indicator of myocardial excitability, is influenced by conduction pattern and distance from the epicardial surface. This study examined AP rise times and conduction velocity as the depolarizing wavefront approaches the epicardial surface. METHODS AND RESULTS Two-photon excitation of di-4-aminonaphthenyl-pyridinum-propylsulfonate was used to measure electric activity at discrete epicardial layers of isolated Langendorff-perfused rabbit hearts to a depth of 500 μm. Endo-to-epicardial wavefronts were studied during right atrial or ventricular endocardial pacing. Similar measurements were made with epi-to-endocardial, transverse, and longitudinal pacing protocols. Results were compared with data from a bidomain model of 3-dimensional (3D) electric propagation within ventricular myocardium. During right atrial and endocardial pacing, AP rise time (10%-90% of upstroke) decreased by ≈50% between 500 and 50 μm from the epicardial surface, whereas conduction velocity increased and AP duration was only slightly shorter (≈4%). These differences were not observed with other conduction patterns. The depth-dependent changes in rise time were larger at higher pacing rates. Modeling data qualitatively reproduced the behavior seen experimentally and demonstrated a parallel reduction in peak I(Na) and electrotonic load as the wavefront approaches the epicardial surface. CONCLUSIONS Decreased electrotonic load at the epicardial surface results in more rapid AP upstrokes and higher conduction velocities compared with the bulk myocardium. Combined effects of tissue depth and pacing rate on AP rise time reduce conduction safety and myocardial excitability within the ventricular wall.
Collapse
Affiliation(s)
- Allen Kelly
- Institute of Cardiovascular and Medical Sciences, University of Glasgow, Glasgow, United Kingdom
| | | | | | | | | | | | | | | | | |
Collapse
|
18
|
Direct action of angiotensin II on the conduction through papillary muscle preparations of rat heart immediately after reoxygenation. J Arrhythm 2012. [DOI: 10.1016/j.joa.2012.02.005] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
|
19
|
Alternans resonance and propagation block during supernormal conduction in cardiac tissue with decreased [K(+)](o). Biophys J 2010; 98:1129-38. [PMID: 20371312 DOI: 10.1016/j.bpj.2009.12.4280] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/06/2009] [Revised: 12/02/2009] [Accepted: 12/03/2009] [Indexed: 11/20/2022] Open
Abstract
Cardiac restitution is an important factor in arrhythmogenesis. Steep positive action potential duration and conduction velocity (CV) restitution slopes promote alternans and reentrant arrhythmias. We examined the consequences of supernormal conduction (characterized by a negative CV restitution slope) on patterns of conduction and alternans in strands of Luo-Rudy model cells and in cultured cardiac cell strands. Interbeat intervals (IBIs) were analyzed as a function of distance during S1S2 protocols and during pacing at alternating cycle lengths. Supernormal conduction was induced by decreasing [K(+)](o). In control [K(+)](o) simulations, S1S2 intervals converged toward basic cycle length with a length constant determined by both CV and the CV restitution slope. During alternant pacing, the amplitude of IBI alternans converged with a shorter length constant, determined also by the action potential duration restitution slope. In contrast, during supernormal conduction, S1S2 intervals and the amplitude of alternans diverged. This amplification (resonance) led to phase-locked or more complex alternans patterns, and then to distal conduction block. The convergence/divergence of IBIs was verified in the cultured strands, in which naturally occurring tissue heterogeneities resulted in prominent discontinuities of the spatial IBI profiles. We conclude that supernormal conduction potentiates alternans and spatial analysis of IBIs represents a powerful method to locate tissue heterogeneities.
Collapse
|
20
|
Bursac N, Kirkton RD, McSpadden LC, Liau B. Characterizing functional stem cell-cardiomyocyte interactions. Regen Med 2010; 5:87-105. [PMID: 20017697 DOI: 10.2217/rme.09.69] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022] Open
Abstract
Despite the progress in traditional pharmacological and organ transplantation therapies, heart failure still afflicts 5.3 million Americans. Since June 2000, stem cell-based approaches for the prevention and treatment of heart failure have been pursued in clinics with great excitement; however, the exact mechanisms of how transplanted cells improve heart function remain elusive. One of the main difficulties in answering these questions is the limited ability to directly access and study interactions between implanted cells and host cardiomyocytes in situ. With the growing number of candidate cell types for potential clinical use, it is becoming increasingly more important to establish standardized, well-controlled in vitro and in situ assays to compare the efficacy and safety of different stem cells in cardiac repair. This article describes recent innovative methodologies to characterize direct functional interactions between stem cells and cardiomyocytes, aimed to facilitate the rational design of future cell-based therapies for heart disease.
Collapse
Affiliation(s)
- Nenad Bursac
- Department of Biomedical Engineering, Duke University, Room 136 Hudson Hall, Durham, NC 27708, USA.
| | | | | | | |
Collapse
|
21
|
de Lange E, Kucera JP. The transfer functions of cardiac tissue during stochastic pacing. Biophys J 2010; 96:294-311. [PMID: 19134481 DOI: 10.1016/j.bpj.2008.09.025] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/30/2008] [Accepted: 09/29/2008] [Indexed: 11/18/2022] Open
Abstract
The restitution properties of cardiac action potential duration (APD) and conduction velocity (CV) are important factors in arrhythmogenesis. They determine alternans, wavebreak, and the patterns of reentrant arrhythmias. We developed a novel approach to characterize restitution using transfer functions. Transfer functions relate an input and an output quantity in terms of gain and phase shift in the complex frequency domain. We derived an analytical expression for the transfer function of interbeat intervals (IBIs) during conduction from one site (input) to another site downstream (output). Transfer functions can be efficiently obtained using a stochastic pacing protocol. Using simulations of conduction and extracellular mapping of strands of neonatal rat ventricular myocytes, we show that transfer functions permit the quantification of APD and CV restitution slopes when it is difficult to measure APD directly. We find that the normally positive CV restitution slope attenuates IBI variations. In contrast, a negative CV restitution slope (induced by decreasing extracellular [K(+)]) amplifies IBI variations with a maximum at the frequency of alternans. Hence, it potentiates alternans and renders conduction unstable, even in the absence of APD restitution. Thus, stochastic pacing and transfer function analysis represent a powerful strategy to evaluate restitution and the stability of conduction.
Collapse
Affiliation(s)
- Enno de Lange
- Department of Physiology, University of Bern, Bern, Switzerland
| | | |
Collapse
|
22
|
Petitprez S, Jespersen T, Pruvot E, Keller DI, Corbaz C, Schläpfer J, Abriel H, Kucera JP. Analyses of a novel SCN5A mutation (C1850S): conduction vs. repolarization disorder hypotheses in the Brugada syndrome. Cardiovasc Res 2008; 78:494-504. [PMID: 18252757 DOI: 10.1093/cvr/cvn023] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Affiliation(s)
- Séverine Petitprez
- Department of Pharmacology and Toxicology, University of Lausanne, 27, Bugnon, 1005 Lausanne, Vaud, Switzerland
| | | | | | | | | | | | | | | |
Collapse
|
23
|
Analysis of damped oscillations during reentry: a new approach to evaluate cardiac restitution. Biophys J 2007; 94:1094-109. [PMID: 17921218 DOI: 10.1529/biophysj.107.113811] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Reentry is a mechanism underlying numerous cardiac arrhythmias. During reentry, head-tail interactions of the action potential can cause cycle length (CL) oscillations and affect the stability of reentry. We developed a method based on a difference-delay equation to determine the slopes of the action potential duration and conduction velocity restitution functions, known to be major determinants of reentrant arrhythmogenesis, from the spatial period P and the decay length D of damped CL oscillations. Using this approach, we analyzed CL oscillations after the induction of reentry and the resetting of reentry with electrical stimuli in rings of cultured neonatal rat ventricular myocytes grown on microelectrode arrays and in corresponding simulations with the Luo-Rudy model. In the experiments, P was larger and D was smaller after resetting impulses compared to the induction of reentry, indicating that reentry became more stable. Both restitution slopes were smaller. Consistent with the experimental findings, resetting of simulated reentry caused oscillations with gradually increasing P, decreasing D, and decreasing restitution slopes. However, these parameters remained constant when ion concentrations were clamped, revealing that intracellular ion accumulation stabilizes reentry. Thus, the analysis of CL oscillations during reentry opens new perspectives to gain quantitative insight into action potential restitution.
Collapse
|