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Honarbakhsh S, Dhillon G, Abbas H, Waddingham PH, Dennis A, Ahluwalia N, Welch S, Daw H, Sporton S, Chow A A, Earley MJ, Lambiase PD, Hunter RJ. Non-invasive Electrocardiographic Imaging guided targeting of drivers of persistent atrial fibrillation: the TARGET-AF1 trial. Heart Rhythm 2022; 19:875-884. [DOI: 10.1016/j.hrthm.2022.01.042] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/02/2021] [Revised: 01/25/2022] [Accepted: 01/30/2022] [Indexed: 12/12/2022]
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2
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Jenkins EV, Dharmaprani D, Schopp M, Quah JX, Tiver K, Mitchell L, Xiong F, Aguilar M, Pope K, Akar FG, Roney CH, Niederer SA, Nattel S, Nash MP, Clayton RH, Ganesan AN. The inspection paradox: An important consideration in the evaluation of rotor lifetimes in cardiac fibrillation. Front Physiol 2022; 13:920788. [PMID: 36148313 PMCID: PMC9486478 DOI: 10.3389/fphys.2022.920788] [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: 04/15/2022] [Accepted: 08/10/2022] [Indexed: 11/18/2022] Open
Abstract
Background and Objective: Renewal theory is a statistical approach to model the formation and destruction of phase singularities (PS), which occur at the pivots of spiral waves. A common issue arising during observation of renewal processes is an inspection paradox, due to oversampling of longer events. The objective of this study was to characterise the effect of a potential inspection paradox on the perception of PS lifetimes in cardiac fibrillation. Methods: A multisystem, multi-modality study was performed, examining computational simulations (Aliev-Panfilov (APV) model, Courtmanche-Nattel model), experimentally acquired optical mapping Atrial and Ventricular Fibrillation (AF/VF) data, and clinically acquired human AF and VF. Distributions of all PS lifetimes across full epochs of AF, VF, or computational simulations, were compared with distributions formed from lifetimes of PS existing at 10,000 simulated commencement timepoints. Results: In all systems, an inspection paradox led towards oversampling of PS with longer lifetimes. In APV computational simulations there was a mean PS lifetime shift of +84.9% (95% CI, ± 0.3%) (p < 0.001 for observed vs overall), in Courtmanche-Nattel simulations of AF +692.9% (95% CI, ±57.7%) (p < 0.001), in optically mapped rat AF +374.6% (95% CI, ± 88.5%) (p = 0.052), in human AF mapped with basket catheters +129.2% (95% CI, ±4.1%) (p < 0.05), human AF-HD grid catheters 150.8% (95% CI, ± 9.0%) (p < 0.001), in optically mapped rat VF +171.3% (95% CI, ±15.6%) (p < 0.001), in human epicardial VF 153.5% (95% CI, ±15.7%) (p < 0.001). Conclusion: Visual inspection of phase movies has the potential to systematically oversample longer lasting PS, due to an inspection paradox. An inspection paradox is minimised by consideration of the overall distribution of PS lifetimes.
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Affiliation(s)
- Evan V Jenkins
- College of Medicine and Public Health, Flinders University, Adelaide, SA, Australia
| | - Dhani Dharmaprani
- College of Medicine and Public Health, Flinders University, Adelaide, SA, Australia.,College of Science and Engineering, Flinders University, Adelaide, SA, Australia
| | - Madeline Schopp
- College of Science and Engineering, Flinders University, Adelaide, SA, Australia
| | - Jing Xian Quah
- College of Medicine and Public Health, Flinders University, Adelaide, SA, Australia.,Department of Cardiovascular Medicine, Flinders Medical Centre, Adelaide, SA, Australia
| | - Kathryn Tiver
- Department of Cardiovascular Medicine, Flinders Medical Centre, Adelaide, SA, Australia
| | - Lewis Mitchell
- School of Mathematical Sciences, University of Adelaide, Adelaide, SA, Australia
| | - Feng Xiong
- Montréal Heart Institute and Université de Montréal, Montréal, QC, Canada
| | - Martin Aguilar
- Montréal Heart Institute and Université de Montréal, Montréal, QC, Canada
| | - Kenneth Pope
- College of Science and Engineering, Flinders University, Adelaide, SA, Australia
| | - Fadi G Akar
- School of Medicine, Yale University, New Haven, CT, United States
| | - Caroline H Roney
- School of Engineering and Materials Science, Queen Mary University of London, London, United Kingdom
| | - Steven A Niederer
- School of Biomedical Engineering and Imaging Sciences, Kings College London, London, United Kingdom
| | - Stanley Nattel
- Montréal Heart Institute and Université de Montréal, Montréal, QC, Canada
| | - Martyn P Nash
- Auckland Bioengineering Institute, University of Auckland, Auckland, New Zealand
| | - Richard H Clayton
- Insigneo Institute for in Silico Medicine and Department of Computer Science, University of Sheffield, Sheffield, United Kingdom
| | - Anand N Ganesan
- College of Medicine and Public Health, Flinders University, Adelaide, SA, Australia.,Department of Cardiovascular Medicine, Flinders Medical Centre, Adelaide, SA, Australia
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Honarbakhsh S, Schilling RJ, Keating E, Finlay M, Hunter RJ. Drivers in AF colocate to sites of electrogram organization and rapidity: Potential synergy between spectral analysis and STAR mapping approaches in prioritizing drivers for ablation. J Cardiovasc Electrophysiol 2020; 31:1340-1349. [PMID: 32219906 DOI: 10.1111/jce.14456] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/17/2019] [Revised: 02/27/2020] [Accepted: 03/16/2020] [Indexed: 11/27/2022]
Abstract
INTRODUCTION Stochastic trajectory analysis of ranked signals (STAR) mapping has recently been used to ablate persistent atrial fibrillation (AF) with high rates of AF termination and long-term freedom from AF in small, single-arm studies. We hypothesized that rapidity and organization markers would correlate with early sites of activation (ESA). METHODS Patients undergoing persistent AF ablation as part of the STAR mapping study were included. Five-minute unipolar basket recordings used to create STAR maps were used to determine the minimum-cycle length (Min-CL) and CL variability (CLV) at each electrode to identify the site of the fastest Min-CL and lowest CLV across the left atrium (LA). The location of ESA targeted with ablation was compared with these sites. Dominant frequency was assessed at ESA and compared with that of neighboring electrodes to assess for regional gradients. RESULTS Thirty-two patients were included with 83 ESA ablated, with an ablation response at 73 sites (24 AF termination and 49 CL slowing ≥30 ms). Out of these, 54 (74.0%) and 56 (76.7%) colocated to sites of fastest Min-CL and lowest CLV, respectively. Regional CL and frequency gradients were demonstrable at majority of ESA. ESA colocating to sites of fastest Min-CL and lowest CLV were more likely to terminate AF with ablation (odds ratio, 34 and 29, respectively, P = .02). These showed a moderate sensitivity (74.0% Min-CL and 75.3% CLV) and specificity (66.7% Min-CL and 76.9% CLV) in predicting ESA with an ablation response. CONCLUSIONS ESA correlate with rapidity and organization markers. Further work is needed to clarify any role for spectral analysis in prioritizing driver ablation.
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Affiliation(s)
| | | | - Emily Keating
- Barts Heart Centre, Barts Health NHS Trust, London, United Kingdom
| | - Malcolm Finlay
- Barts Heart Centre, Barts Health NHS Trust, London, United Kingdom
| | - Ross J Hunter
- Barts Heart Centre, Barts Health NHS Trust, London, United Kingdom.,QUML
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4
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Chaotic Dynamics Enhance the Sensitivity of Inner Ear Hair Cells. Sci Rep 2019; 9:18394. [PMID: 31804578 PMCID: PMC6895040 DOI: 10.1038/s41598-019-54952-y] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/25/2018] [Accepted: 11/21/2019] [Indexed: 12/03/2022] Open
Abstract
Hair cells of the auditory and vestibular systems are capable of detecting sounds that induce sub-nanometer vibrations of the hair bundle, below the stochastic noise levels of the surrounding fluid. Furthermore, the auditory system exhibits a highly rapid response time, in the sub-millisecond regime. We propose that chaotic dynamics enhance the sensitivity and temporal resolution of the hair bundle response, and we provide experimental and theoretical evidence for this effect. We use the Kolmogorov entropy to measure the degree of chaos in the system and the transfer entropy to quantify the amount of stimulus information captured by the detector. By varying the viscosity and ionic composition of the surrounding fluid, we are able to experimentally modulate the degree of chaos observed in the hair bundle dynamics in vitro. We consistently find that the hair bundle is most sensitive to a stimulus of small amplitude when it is poised in the weakly chaotic regime. Further, we show that the response time to a force step decreases with increasing levels of chaos. These results agree well with our numerical simulations of a chaotic Hopf oscillator and suggest that chaos may be responsible for the high sensitivity and rapid temporal response of hair cells.
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5
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Honarbakhsh S, Schilling RJ, Dhillon G, Ullah W, Keating E, Providencia R, Chow A, Earley MJ, Hunter RJ. A Novel Mapping System for Panoramic Mapping of the Left Atrium: Application to Detect and Characterize Localized Sources Maintaining Atrial Fibrillation. JACC Clin Electrophysiol 2019; 4:124-134. [PMID: 29387810 PMCID: PMC5777816 DOI: 10.1016/j.jacep.2017.09.177] [Citation(s) in RCA: 68] [Impact Index Per Article: 13.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/01/2022]
Abstract
Objectives This study sought to use a novel panoramic mapping system (CARTOFINDER) to detect and characterize drivers in persistent atrial fibrillation (AF). Background Mechanisms sustaining persistent AF remain uncertain. Methods Patients undergoing catheter ablation for persistent AF were included. A 64-pole basket catheter was used to acquire unipolar signals, which were processed by the mapping system to generate wavefront propagation maps. The system was used to identify and characterize potential drivers in AF pre- and post-pulmonary vein (PV) isolation. The effect of ablation on drivers identified post-PV isolation was assessed. Results Twenty patients were included in the study with 112 CARTOFINDER maps created. Potential drivers were mapped in 19 of 20 patients with AF (damage to the basket and noise on electrograms was present in 1 patient). Thirty potential drivers were identified all of which were transient but repetitive; 19 were rotational and 11 focal. Twenty-six drivers were ablated with a predefined response in 22 of 26 drivers: AF terminated with 12 and cycle length slowed (≥30 ms) with 10. Drivers with rotational activation were predominantly mapped to sites of low-voltage zones (81.8%). PV isolation had no remarkable impact on the cycle length at the driver sites (138.4 ± 14.3 ms pre-PV isolation vs. 137.2 ± 15.2 ms post-PV isolation) and drivers that had also been identified on pre-PV isolation maps were more commonly associated with AF termination. Conclusions Drivers were identified in almost all patients in the form of intermittent but repetitive focal or rotational activation patterns. The mechanistic importance of these phenomena was confirmed by the response to ablation.
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Affiliation(s)
- Shohreh Honarbakhsh
- Barts Heart Centre, St. Bartholomew's Hospital, Barts Health NHS Trust, London, United Kingdom
| | - Richard J Schilling
- Barts Heart Centre, St. Bartholomew's Hospital, Barts Health NHS Trust, London, United Kingdom
| | - Gurpreet Dhillon
- Barts Heart Centre, St. Bartholomew's Hospital, Barts Health NHS Trust, London, United Kingdom
| | - Waqas Ullah
- Barts Heart Centre, St. Bartholomew's Hospital, Barts Health NHS Trust, London, United Kingdom
| | - Emily Keating
- Barts Heart Centre, St. Bartholomew's Hospital, Barts Health NHS Trust, London, United Kingdom
| | - Rui Providencia
- Barts Heart Centre, St. Bartholomew's Hospital, Barts Health NHS Trust, London, United Kingdom
| | - Anthony Chow
- Barts Heart Centre, St. Bartholomew's Hospital, Barts Health NHS Trust, London, United Kingdom
| | - Mark J Earley
- Barts Heart Centre, St. Bartholomew's Hospital, Barts Health NHS Trust, London, United Kingdom
| | - Ross J Hunter
- Barts Heart Centre, St. Bartholomew's Hospital, Barts Health NHS Trust, London, United Kingdom.
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Honarbakhsh S, Hunter RJ, Ullah W, Keating E, Finlay M, Schilling RJ. Ablation in Persistent Atrial Fibrillation Using Stochastic Trajectory Analysis of Ranked Signals (STAR) Mapping Method. JACC Clin Electrophysiol 2019; 5:817-829. [PMID: 31320010 DOI: 10.1016/j.jacep.2019.04.007] [Citation(s) in RCA: 29] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/28/2019] [Revised: 04/23/2019] [Accepted: 04/24/2019] [Indexed: 11/16/2022]
Abstract
OBJECTIVES The aim of this study was to demonstrate that a stochastic vector-based mapping approach could guide ablation of atrial fibrillation (AF) drivers as evidenced by ablation response and long-term follow-up outcomes. BACKGROUND The optimal method for mapping and ablation of AF drivers is yet to be defined. METHODS Patients undergoing persistent AF ablation were recruited. Patients underwent pulmonary vein isolation (PVI) with further ablation guided by the stochastic trajectory analysis of ranked signals (STAR) mapping method. The proportion of the time an electrode's activation was seen to precede its neighboring electrodes activation was used to determine early sites of activation (ESA). A positive ablation response at ESA was defined as AF termination or cycle length slowing of ≥30 ms. Clinical outcome was defined as recurrence of AF/atrial tachycardia (AT) during a follow-up of 12 months. RESULTS Thirty-five patients were included (AF duration of 14.4 ± 5.3 months). After PVI, an average of 2.6 ± 0.8 ESA were ablated per patient with study-defined ablation response achieved in all patients. Of the 86 STAR maps created post-PVI, the same ESA was identified on 73.8 ± 26.1% of maps. ESA that resulted in AF termination were more likely to be identified on both pre- and post-PVI maps than those associated with cycle length slowing (23 of 24 vs. 16 of 49; p < 0.001). During a follow-up of 18.5 ± 3.7 months, 28 (80%) patients were free from AF/AT. CONCLUSIONS The ablation response at ESA suggests they may be drivers of AF. Ablation guided by STAR mapping produced a favorable clinical outcome and warrants testing through a randomized controlled trial. (Identification, Electro-mechanical Characterisation and Ablation of Driver Regions in Persistent Atrial Fibrillation [STAR MAPPING]; NCT02950844).
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Affiliation(s)
- Shohreh Honarbakhsh
- Barts Heart Centre, Barts Health National Health Service Trust, London, United Kingdom
| | - Ross J Hunter
- Barts Heart Centre, Barts Health National Health Service Trust, London, United Kingdom
| | - Waqas Ullah
- Barts Heart Centre, Barts Health National Health Service Trust, London, United Kingdom
| | - Emily Keating
- Barts Heart Centre, Barts Health National Health Service Trust, London, United Kingdom
| | - Malcolm Finlay
- Barts Heart Centre, Barts Health National Health Service Trust, London, United Kingdom
| | - Richard J Schilling
- Barts Heart Centre, Barts Health National Health Service Trust, London, United Kingdom.
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Zile MA, Trayanova NA. Increased thin filament activation enhances alternans in human chronic atrial fibrillation. Am J Physiol Heart Circ Physiol 2018; 315:H1453-H1462. [PMID: 30141984 PMCID: PMC6297809 DOI: 10.1152/ajpheart.00658.2017] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/10/2017] [Revised: 08/21/2018] [Accepted: 08/21/2018] [Indexed: 11/22/2022]
Abstract
Action potential duration (APD) alternans (APD-ALT), defined as beat-to-beat oscillations in APD, has been proposed as an important clinical marker for chronic atrial fibrillation (cAF) risk when it occurs at pacing rates of 120-200 beats/min. Although the ionic mechanisms for occurrence of APD-ALT in human cAF at these clinically relevant rates have been investigated, little is known about the effects of myofilament protein kinetics on APD-ALT. Therefore, we used computer simulations of single cell function to explore whether remodeling in myofilament protein kinetics in human cAF alters the occurrence of APD-ALT and to uncover how these mechanisms are affected by sarcomere length and the degree of cAF-induced myofilament remodeling. Mechanistically based, bidirectionally coupled electromechanical models of human right and left atrial myocytes were constructed, incorporating both ionic and myofilament remodeling associated with cAF. By comparing results from our electromechanical model with those from the uncoupled ionic model, we found that intracellular Ca2+ concentration buffering of troponin C has a dampening effect on the magnitude of APD-ALT (APD-ANM) at slower rates (150 beats/min) due to the cooperativity between strongly bound cross-bridges and Ca2+-troponin C binding affinity. We also discovered that cAF-induced enhanced thin filament activation enhanced APD-ANM at these clinically relevant heart rates (150 beats/min). In addition, longer sarcomere lengths increased APD-ANM, suggesting that atrial stretch is an important modulator of APD-ALT. Together, these findings demonstrate that myofilament kinetics mechanisms play an important role in altering APD-ALT in human cAF. NEW & NOTEWORTHY Using a single cell simulation approach, we explored how myofilament protein kinetics alter the formation of alternans in action potential duration (APD) in human myocytes with chronic atrial fibrillation remodeling. We discovered that enhanced thin filament activation and longer sarcomere lengths increased the magnitude of APD alternans at clinically important pacing rates of 120-200 beats/min. Furthermore, we found that altered intracellular Ca2+ concentration buffering of troponin C has a dampening effect on the magnitude of APD alternans.
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Affiliation(s)
- Melanie A Zile
- Institute for Computational Medicine and Department of Biomedical Engineering, Johns Hopkins University , Baltimore, Maryland
| | - Natalia A Trayanova
- Institute for Computational Medicine and Department of Biomedical Engineering, Johns Hopkins University , Baltimore, Maryland
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Handa BS, Roney CH, Houston C, Qureshi NA, Li X, Pitcher DS, Chowdhury RA, Lim PB, Dupont E, Niederer SA, Cantwell CD, Peters NS, Ng FS. Analytical approaches for myocardial fibrillation signals. Comput Biol Med 2018; 102:315-326. [PMID: 30025847 PMCID: PMC6215772 DOI: 10.1016/j.compbiomed.2018.07.008] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/22/2018] [Revised: 07/11/2018] [Accepted: 07/11/2018] [Indexed: 12/11/2022]
Abstract
Atrial and ventricular fibrillation are complex arrhythmias, and their underlying mechanisms remain widely debated and incompletely understood. This is partly because the electrical signals recorded during myocardial fibrillation are themselves complex and difficult to interpret with simple analytical tools. There are currently a number of analytical approaches to handle fibrillation data. Some of these techniques focus on mapping putative drivers of myocardial fibrillation, such as dominant frequency, organizational index, Shannon entropy and phase mapping. Other techniques focus on mapping the underlying myocardial substrate sustaining fibrillation, such as voltage mapping and complex fractionated electrogram mapping. In this review, we discuss these techniques, their application and their limitations, with reference to our experimental and clinical data. We also describe novel tools including a new algorithm to map microreentrant circuits sustaining fibrillation.
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Affiliation(s)
- Balvinder S Handa
- ElectroCardioMaths, Imperial Centre for Cardiac Engineering, National Heart & Lung Institute, Imperial College London, United Kingdom
| | - Caroline H Roney
- Division of Imaging Sciences and Bioengineering, King's College London, United Kingdom
| | - Charles Houston
- ElectroCardioMaths, Imperial Centre for Cardiac Engineering, National Heart & Lung Institute, Imperial College London, United Kingdom
| | - Norman A Qureshi
- ElectroCardioMaths, Imperial Centre for Cardiac Engineering, National Heart & Lung Institute, Imperial College London, United Kingdom
| | - Xinyang Li
- ElectroCardioMaths, Imperial Centre for Cardiac Engineering, National Heart & Lung Institute, Imperial College London, United Kingdom
| | - David S Pitcher
- ElectroCardioMaths, Imperial Centre for Cardiac Engineering, National Heart & Lung Institute, Imperial College London, United Kingdom
| | - Rasheda A Chowdhury
- ElectroCardioMaths, Imperial Centre for Cardiac Engineering, National Heart & Lung Institute, Imperial College London, United Kingdom
| | - Phang Boon Lim
- ElectroCardioMaths, Imperial Centre for Cardiac Engineering, National Heart & Lung Institute, Imperial College London, United Kingdom
| | - Emmanuel Dupont
- ElectroCardioMaths, Imperial Centre for Cardiac Engineering, National Heart & Lung Institute, Imperial College London, United Kingdom
| | - Steven A Niederer
- Division of Imaging Sciences and Bioengineering, King's College London, United Kingdom
| | - Chris D Cantwell
- ElectroCardioMaths, Imperial Centre for Cardiac Engineering, National Heart & Lung Institute, Imperial College London, United Kingdom; Department of Aeronautics, Imperial College London, United Kingdom
| | - Nicholas S Peters
- ElectroCardioMaths, Imperial Centre for Cardiac Engineering, National Heart & Lung Institute, Imperial College London, United Kingdom
| | - Fu Siong Ng
- ElectroCardioMaths, Imperial Centre for Cardiac Engineering, National Heart & Lung Institute, Imperial College London, United Kingdom.
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9
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Faber J, Bozovic D. Chaotic Dynamics of Inner Ear Hair Cells. Sci Rep 2018; 8:3366. [PMID: 29463841 PMCID: PMC5820366 DOI: 10.1038/s41598-018-21538-z] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/09/2017] [Accepted: 02/06/2018] [Indexed: 11/09/2022] Open
Abstract
Experimental records of active bundle motility are used to demonstrate the presence of a low-dimensional chaotic attractor in hair cell dynamics. Dimensionality tests from dynamic systems theory are applied to estimate the number of independent variables sufficient for modelling the hair cell response. Poincaré maps are constructed to observe a quasiperiodic transition from chaos to order with increasing amplitudes of mechanical forcing. The onset of this transition is accompanied by a reduction of Kolmogorov entropy in the system and an increase in transfer entropy between the stimulus and the hair bundle, indicative of signal detection. A simple theoretical model is used to describe the observed chaotic dynamics. The model exhibits an enhancement of sensitivity to weak stimuli when the system is poised in the chaotic regime. We propose that chaos may play a role in the hair cell's ability to detect low-amplitude sounds.
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Affiliation(s)
- Justin Faber
- Department of Physics & Astronomy, University of California, Los Angeles, California, 90095, USA
| | - Dolores Bozovic
- Department of Physics & Astronomy, University of California, Los Angeles, California, 90095, USA. .,California NanoSystems Institute, University of California, Los Angeles, California, 90095, USA.
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Lim B, Hwang M, Song JS, Ryu AJ, Joung B, Shim EB, Ryu H, Pak HN. Effectiveness of atrial fibrillation rotor ablation is dependent on conduction velocity: An in-silico 3-dimensional modeling study. PLoS One 2017; 12:e0190398. [PMID: 29287119 PMCID: PMC5747478 DOI: 10.1371/journal.pone.0190398] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/27/2017] [Accepted: 12/14/2017] [Indexed: 11/29/2022] Open
Abstract
BACKGROUND We previously reported that stable rotors are observed in in-silico human atrial fibrillation (AF) models, and are well represented by a dominant frequency (DF). In the current study, we hypothesized that the outcome of DF ablation is affected by conduction velocity (CV) conditions and examined this hypothesis using in-silico 3D-AF modeling. METHODS We integrated 3D CT images of left atrium obtained from 10 patients with persistent AF (80% male, 61.8±13.5 years old) into in-silico AF model. We compared AF maintenance durations (max 300s), spatiotemporal stabilities of DF, phase singularity (PS) number, life-span of PS, and AF termination or defragmentation rates after virtual DF ablation with 5 different CV conditions (0.2, 0.3, 0.4, 0.5, and 0.6m/s). RESULTS 1. AF maintenance duration (p<0.001), spatiotemporal mean variance of DF (p<0.001), and the number of PS (p = 0.023) showed CV dependent bimodal patterns (highest at CV0.4m/s and lowest at CV0.6m/s) consistently. 2. After 10% highest DF ablation, AF defragmentation rates were the lowest at CV0.4m/s (37.8%), but highest at CV0.5 and 0.6m/s (all 100%, p<0.001). 3. In the episodes with AF termination or defragmentation followed by 10% highest DF ablation, baseline AF maintenance duration was shorter (p<0.001), spatiotemporal mean variance of DF was lower (p = 0.014), and the number of PS was lower (p = 0.004) than those with failed AF defragmentation after DF ablation. CONCLUSION Virtual ablation of DF, which may indicate AF driver, was more likely to terminate or defragment AF with spatiotemporally stable DF, but not likely to do so in long-lasting and sustained AF conditions, depending on CV.
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Affiliation(s)
- Byounghyun Lim
- Yonsei University Health System, Seoul, Republic of Korea
| | - Minki Hwang
- Yonsei University Health System, Seoul, Republic of Korea
| | - Jun-Seop Song
- Yonsei University Health System, Seoul, Republic of Korea
| | - Ah-Jin Ryu
- Department of Mechanical and Biomedical Engineering, Kangwon National University, Chuncheon, Ganwon-do, Republic of Korea
| | - Boyoung Joung
- Yonsei University Health System, Seoul, Republic of Korea
| | - Eun Bo Shim
- Department of Mechanical and Biomedical Engineering, Kangwon National University, Chuncheon, Ganwon-do, Republic of Korea
| | - Hyungon Ryu
- NVIDIA, Yonsei University, Department of Mathematics, Seoul, Republic of Korea
| | - Hui-Nam Pak
- Yonsei University Health System, Seoul, Republic of Korea
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11
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Yang PS, Park YA, Kim TH, Uhm JS, Joung B, Lee MH, Pak HN. Which patients recur as atrial tachycardia rather than atrial fibrillation after catheter ablation of atrial fibrillation? PLoS One 2017; 12:e0188326. [PMID: 29145517 PMCID: PMC5690680 DOI: 10.1371/journal.pone.0188326] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/24/2017] [Accepted: 11/03/2017] [Indexed: 01/09/2023] Open
Abstract
INTRODUCTION The ablation gaps have been known as the main mechanism of recurrence as atrial tachycardia (AT) rather than atrial fibrillation (AF) after AF catheter ablation. However, AF organization due to reduction of critical mass or focal trigger may also be the mechanism of AT recurrence. We sought to find out the main clinical factors of recurrence as AT rather than AF after AF ablation in the absence of antiarrhythmic drug effect. METHODS We analyzed 521 patients (70.8% men, 64.1% paroxysmal AF) who experienced AT or AF recurrence without antiarrhythmic drug effect during 44.7 ± 25.4 months follow-up. RESULTS Among 521 patients with recurrence, 42.0% (219 of 521) recurred with AT. The proportion of AT recurrence was not different between the pulmonary vein isolation only group and additional linear ablation group (45.1% vs. 38.1%, p = 0.128). The absence of hypertension (odds ratio [OR] 0.49, 95% confidence interval [CI] 0.29-0.83, p = 0.007), small left atrial (LA) volume index (OR 0.89 per 10 mL/m2, 95% CI 0.79-1.00, p = 0.049), and high mean LA bipolar voltage (OR 2.03 per 1 mV, 95% CI 1.30-3.16, p = 0.002) were independently associated with AT recurrence, whereas additional linear ablation was not. Among 90 patients who underwent repeat ablation procedure, rates of PV reconnection (p = 0.358) and gap in prior linear ablations (p = 0.269) were not significantly different between AT recurrence group and AF recurrence group. CONCLUSION The degree of LA remodeling is significantly associated with recurrence as AT after AF ablation, irrespective of potential ablation gap in linear lesion.
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Affiliation(s)
- Pil-Sung Yang
- Yonsei University Health System, Seoul, Republic of Korea
| | - Young-Ah Park
- Division of Cardiology, Inje University, Busan Paik Hosipital, Busan, Republic of Korea
| | - Tae-Hoon Kim
- Yonsei University Health System, Seoul, Republic of Korea
| | - Jae-Sun Uhm
- Yonsei University Health System, Seoul, Republic of Korea
| | - Boyoung Joung
- Yonsei University Health System, Seoul, Republic of Korea
| | | | - Hui-Nam Pak
- Yonsei University Health System, Seoul, Republic of Korea
- * E-mail:
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12
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Luo Q, Jin Q, Zhang N, Han Y, Wang Y, Huang S, Lin C, Ling T, Chen K, Pan W, Wu L. Global Bi-ventricular endocardial distribution of activation rate during long duration ventricular fibrillation in normal and heart failure canines. BMC Cardiovasc Disord 2017; 17:99. [PMID: 28407744 PMCID: PMC5390480 DOI: 10.1186/s12872-017-0530-5] [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: 10/31/2016] [Accepted: 04/01/2017] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND The objective of this study was to detect differences in the distribution of the left and right ventricle (LV & RV) activation rate (AR) during short-duration ventricular fibrillation (SDVF, <1 min) and long-duration ventricular fibrillation VF (LDVF, >1 min) in normal and heart failure (HF) canine hearts. METHODS Ventricular fibrillation (VF) was electrically induced in six healthy dogs (control group) and six dogs with right ventricular pacing-induced congestive HF (HF group). Two 64-electrode basket catheters deployed in the LV and RV were used for global endocardium electrical mapping. The AR of VF was estimated by fast Fourier transform analysis from each electrode. RESULTS In the control group, the LV was activated faster than the RV in the first 20 s, after which there was no detectable difference in the AR between them. When analyzing the distribution of the AR within the bi-ventricles at 3 min of LDVF, the posterior LV was activated fastest, while the anterior was slowest. In the HF group, a detectable AR gradient existed between the two ventricles within 3 min of VF, with the LV activating more quickly than the RV. When analyzing the distribution of the AR within the bi-ventricles at 3 min of LDVF, the septum of the LV was activated fastest, while the anterior was activated slowest. CONCLUSIONS A global bi-ventricular endocardial AR gradient existed within the first 20 s of VF but disappeared in the LDVF in healthy hearts. However, the AR gradient was always observed in both SDVF and LDVF in HF hearts. The findings of this study suggest that LDVF in HF hearts can be maintained differently from normal hearts, which accordingly should lead to the development of different management strategies for LDVF resuscitation.
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Affiliation(s)
- Qingzhi Luo
- Department of Cardiology, Shanghai Ruijin Hospital, Shanghai Jiao Tong University School of Medicine, No. 197, Ruijin Er Road, Shanghai, 200025, People's Republic of China
| | - Qi Jin
- Department of Cardiology, Shanghai Ruijin Hospital, Shanghai Jiao Tong University School of Medicine, No. 197, Ruijin Er Road, Shanghai, 200025, People's Republic of China
| | - Ning Zhang
- Department of Cardiology, Shanghai Ruijin Hospital, Shanghai Jiao Tong University School of Medicine, No. 197, Ruijin Er Road, Shanghai, 200025, People's Republic of China
| | - Yanxin Han
- Department of Cardiology, Shanghai Ruijin Hospital, Shanghai Jiao Tong University School of Medicine, No. 197, Ruijin Er Road, Shanghai, 200025, People's Republic of China
| | - Yilong Wang
- Department of Cardiology, Shanghai Ruijin Hospital, Shanghai Jiao Tong University School of Medicine, No. 197, Ruijin Er Road, Shanghai, 200025, People's Republic of China
| | - Shangwei Huang
- Department of Cardiology, Shanghai Ruijin Hospital, Shanghai Jiao Tong University School of Medicine, No. 197, Ruijin Er Road, Shanghai, 200025, People's Republic of China
| | - Changjian Lin
- Department of Cardiology, Shanghai Ruijin Hospital, Shanghai Jiao Tong University School of Medicine, No. 197, Ruijin Er Road, Shanghai, 200025, People's Republic of China
| | - Tianyou Ling
- Department of Cardiology, Shanghai Ruijin Hospital, Shanghai Jiao Tong University School of Medicine, No. 197, Ruijin Er Road, Shanghai, 200025, People's Republic of China
| | - Kang Chen
- Department of Cardiology, Shanghai Ruijin Hospital, Shanghai Jiao Tong University School of Medicine, No. 197, Ruijin Er Road, Shanghai, 200025, People's Republic of China
| | - Wenqi Pan
- Department of Cardiology, Shanghai Ruijin Hospital, Shanghai Jiao Tong University School of Medicine, No. 197, Ruijin Er Road, Shanghai, 200025, People's Republic of China
| | - Liqun Wu
- Department of Cardiology, Shanghai Ruijin Hospital, Shanghai Jiao Tong University School of Medicine, No. 197, Ruijin Er Road, Shanghai, 200025, People's Republic of China.
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Hwang M, Park J, Lee YS, Park JH, Choi SH, Shim EB, Pak HN. Fibrillation Number Based on Wavelength and Critical Mass in Patients Who Underwent Radiofrequency Catheter Ablation for Atrial Fibrillation. IEEE Trans Biomed Eng 2015; 62:673-9. [DOI: 10.1109/tbme.2014.2363669] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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Park SA, Gray RA. Optical Mapping of Ventricular Fibrillation Dynamics. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2015; 859:313-42. [PMID: 26238059 DOI: 10.1007/978-3-319-17641-3_13] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/21/2023]
Abstract
There is very limited information regarding the dynamic patterns of the electrical activity during ventricular fibrillation (VF) in humans. Most of the data used to generate and test hypotheses regarding the mechanisms of VF come from animal models and computer simulations and the quantification of VF patterns is non-trivial. Many of the experimental recordings of the dynamic spatial patterns of VF have been obtained from mammals using "optical mapping" or "video imaging" technology in which "phase maps" are derived from high-resolution transmembrane recordings from the heart surface. The surface manifestation of the unstable reentrant waves sustaining VF can be identified as "phase singularities" and their number and location provide one measure of VF complexity. After providing a brief history of optical mapping of VF, we compare and contrast a quantitative analysis of VF patterns from the heart surface for four different animal models, hence providing physiological insight into the variety of VF dynamics among species. We found that in all four animal models the action potential duration restitution slope was actually negative during VF and that the spatial dispersion of electrophysiological parameters were not different during the first second of VF compared to pacing immediately before VF initiation. Surprisingly, our results suggest that APD restitution and spatial dispersion may not be essential causes of VF dynamics. Analyses of electrophysiological quantities in the four animal models are consistent with the idea that VF is essentially a two-dimensional phenomenon in small rabbit hearts whose size are near the boundary of the "critical mass" required to sustain VF, while VF in large pig hearts is three-dimensional and exhibits the maximal theoretical phase singularity density, and thus will not terminate spontaneously.
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Affiliation(s)
- Sarah A Park
- F.M. Kirby Research Center for Functional Brain Imaging, Kennedy Krieger Institute, Russell H. Morgan Department of Radiology, The Johns Hopkins University School of Medicine, Baltimore, MD, 21205, USA
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Abstract
In a normal human life span, the heart beats about 2 to 3 billion times. Under diseased conditions, a heart may lose its normal rhythm and degenerate suddenly into much faster and irregular rhythms, called arrhythmias, which may lead to sudden death. The transition from a normal rhythm to an arrhythmia is a transition from regular electrical wave conduction to irregular or turbulent wave conduction in the heart, and thus this medical problem is also a problem of physics and mathematics. In the last century, clinical, experimental, and theoretical studies have shown that dynamical theories play fundamental roles in understanding the mechanisms of the genesis of the normal heart rhythm as well as lethal arrhythmias. In this article, we summarize in detail the nonlinear and stochastic dynamics occurring in the heart and their links to normal cardiac functions and arrhythmias, providing a holistic view through integrating dynamics from the molecular (microscopic) scale, to the organelle (mesoscopic) scale, to the cellular, tissue, and organ (macroscopic) scales. We discuss what existing problems and challenges are waiting to be solved and how multi-scale mathematical modeling and nonlinear dynamics may be helpful for solving these problems.
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Affiliation(s)
- Zhilin Qu
- Department of Medicine (Cardiology), David Geffen School of Medicine, University of California, Los Angeles, California 90095, USA
- Correspondence to: Zhilin Qu, PhD, Department of Medicine, Division of Cardiology, David Geffen School of Medicine at UCLA, A2-237 CHS, 650 Charles E. Young Drive South, Los Angeles, CA 90095, Tel: 310-794-6050, Fax: 310-206-9133,
| | - Gang Hu
- Department of Physics, Beijing Normal University, Beijing 100875, China
| | - Alan Garfinkel
- Department of Medicine (Cardiology), David Geffen School of Medicine, University of California, Los Angeles, California 90095, USA
- Department of Integrative Biology and Physiology, University of California, Los Angeles, California 90095, USA
| | - James N. Weiss
- Department of Medicine (Cardiology), David Geffen School of Medicine, University of California, Los Angeles, California 90095, USA
- Department of Physiology, David Geffen School of Medicine, University of California, Los Angeles, California 90095, USA
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Clinical application of the fibrillation number in patients with an implantable cardioverter defibrillator. PROGRESS IN BIOPHYSICS AND MOLECULAR BIOLOGY 2014; 116:33-9. [DOI: 10.1016/j.pbiomolbio.2014.09.004] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/18/2014] [Revised: 09/05/2014] [Accepted: 09/07/2014] [Indexed: 11/21/2022]
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Hsieh YC, Chang PC, Hsueh CH, Lee YS, Shen C, Weiss JN, Chen Z, Ai T, Lin SF, Chen PS. Apamin-sensitive potassium current modulates action potential duration restitution and arrhythmogenesis of failing rabbit ventricles. Circ Arrhythm Electrophysiol 2013; 6:410-8. [PMID: 23420832 DOI: 10.1161/circep.111.000152] [Citation(s) in RCA: 51] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/23/2023]
Abstract
BACKGROUND Apamin-sensitive K currents (I(KAS)) are upregulated in heart failure. We hypothesize that apamin can flatten action potential duration restitution (APDR) curve and can reduce ventricular fibrillation duration in failing ventricles. METHODS AND RESULTS We simultaneously mapped membrane potential and intracellular Ca (Ca(i)) in 7 rabbit hearts with pacing-induced heart failure and in 7 normal hearts. A dynamic pacing protocol was used to determine APDR at baseline and after apamin (100 nmol/L) infusion. Apamin did not change APD(80) in normal ventricles, but prolonged APD(80) in failing ventricles at either long (≥300 ms) or short (≤170 ms) pacing cycle length, but not at intermediate pacing cycle length. The maximal slope of APDR curve was 2.03 (95% confidence interval, 1.73-2.32) in failing ventricles and 1.26 (95% confidence interval, 1.13-1.40) in normal ventricles at baseline (P=0.002). After apamin administration, the maximal slope of APDR in failing ventricles decreased to 1.43 (95% confidence interval, 1.01-1.84; P=0.018), whereas no significant changes were observed in normal ventricles. During ventricular fibrillation in failing ventricles, the number of phase singularities (baseline versus apamin, 4.0 versus 2.5), dominant frequency (13.0 versus 10.0 Hz), and ventricular fibrillation duration (160 versus 80 s) were all significantly (P<0.05) decreased by apamin. CONCLUSIONS Apamin prolongs APD at long and short, but not at intermediate pacing cycle length in failing ventricles. I(KAS) upregulation may be antiarrhythmic by preserving the repolarization reserve at slow heart rate, but is proarrhythmic by steepening the slope of APDR curve, which promotes the generation and maintenance of ventricular fibrillation.
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Affiliation(s)
- Yu-Cheng Hsieh
- Department of Medicine, Division of Cardiology, Krannert Institute of Cardiology, Indiana University School of Medicine, Indianapolis, IN 46202, USA
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Chorro FJ, Ibañez-Catalá X, Trapero I, Such-Miquel L, Pelechano F, Cánoves J, Mainar L, Tormos A, Cerdá JM, Alberola A, Such L. Ventricular fibrillation conduction through an isthmus of preserved myocardium between radiofrequency lesions. PACING AND CLINICAL ELECTROPHYSIOLOGY: PACE 2012; 36:286-98. [PMID: 23240900 DOI: 10.1111/pace.12060] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/17/2011] [Revised: 10/14/2012] [Accepted: 10/23/2012] [Indexed: 11/30/2022]
Abstract
BACKGROUND Selective local acceleration of myocardial activation during ventricular fibrillation (VF) contributes information on the interactions between neighboring zones during the arrhythmia. This study analyzes these interactions, centering the observations on an isthmus of myocardium between two radiofrequency (RF) lesions. METHODS In nine isolated rabbit hearts, a gap of preserved myocardium was established between two RF lesions in the anterolateral left ventricle (LV) wall. Before, during, and after increasing the spatial heterogeneity of VF by local myocardial stretching, VF epicardial recordings were obtained. RESULTS Local stretch in the anterior LV wall decreased the excitable window (17 ± 7 ms vs 26 ± 7 ms; P < 0.05) and increased the dominant frequency (DFr; 18.9 ± 5.0 Hz vs 15.2 ± 3.6 Hz; P < 0.05) in this zone, without changes in the non-stretched posterolateral zone (25 ± 4 ms vs 27 ± 6 ms, ns and 14.1 ± 2.7 Hz vs 14.3 ± 3.0 Hz, ns). The DFr ratio at both sides of the gap was inversely correlated to the excitable window ratio (R = -0.57; P = 0.002). Before (31% vs 26%), during (29% vs 22%), and after stretch suppression (35% vs 25%), the wavefronts passing through the gap from the posterolateral to the anterior LV wall were seen to predominate. The number of wavefronts that passed from the anterior to the posterolateral LV wall was related to the excitable window in this zone (R = 0.41; P = 0.03). CONCLUSIONS The VF acceleration induced in the stretched zone does not increase the flow of wavefronts toward the non-stretched zone in the adjacent gap of preserved myocardium. The absence of significant changes in the electrophysiological parameters of the non-stretched myocardium limits the arrival of wavefronts in this zone.
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Affiliation(s)
- Francisco J Chorro
- Service of Cardiology, Valencia University Clinic Hospital Incliva, Valencia, Spain.
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HWANG EUISEOCK, NAM GIBYUNG, JOUNG BOYOUNG, PARK JUNBEOM, LEE JIHEISARA, SHIM JAEMIN, UHM JAESUN, LEE MOONHYOUNG, PAK HUINAM. Significant Reduction of Atrial Defibrillation Threshold and Inducibility by Catheter Ablation of Atrial Fibrillation. PACING AND CLINICAL ELECTROPHYSIOLOGY: PACE 2012; 35:1428-35. [DOI: 10.1111/j.1540-8159.2012.03517.x] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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Morita N, Lee JH, Bapat A, Fishbein MC, Mandel WJ, Chen PS, Weiss JN, Karagueuzian HS. Glycolytic inhibition causes spontaneous ventricular fibrillation in aged hearts. Am J Physiol Heart Circ Physiol 2011; 301:H180-91. [PMID: 21478408 DOI: 10.1152/ajpheart.00128.2011] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
Selective glycolytic inhibition (GI) promotes electromechanical alternans and triggered beats in isolated cardiac myocytes. We sought to determine whether GI promotes triggered activity by early afterdepolarization (EAD) or delayed afterdepolarizations in intact hearts isolated from adult and aged rats. Dual voltage and intracellular calcium ion (Ca(i)(2+)) fluorescent optical maps and single cell glass microelectrode recordings were made from the left ventricular (LV) epicardium of isolated Langendorff-perfused adult (∼4 mo) and aged (∼24 mo) rat hearts. GI was induced by replacing glucose with 10 mM pyruvate in oxygenated Tyrode's. Within 20 min, GI slowed Ca(i)(2+) transient decline rate and shortened action potential duration in both groups. These changes were associated with ventricular fibrillation (VF) in the aged hearts (64 out of 66) but not in adult hearts (0 out of 18; P < 0.001). VF was preceded by a transient period of focal ventricular tachycardia caused by EAD-mediated triggered activity leading to VF within seconds. The VF was suppressed by the ATP-sensitive K (K(ATP)) channel blocker glibenclamide (1 μM) but not (0 out of 7) by mitochondrial K(ATP) block. The Ca-calmodulin-dependent protein kinase II (CaMKII) blocker KN-93 (1 μM) prevented GI-mediated VF (P < 0.05). Block of Na-Ca exchanger (NCX) by SEA0400 (2 μM) prevented GI-mediated VF (3 out of 6), provided significant bradycardia did not occur. Aged hearts had significantly greater LV fibrosis and reduced connexin 43 than adult hearts (P < 0.05). We conclude that in aged fibrotic unlike in adult rat hearts, GI promotes EADs, triggered activity, and VF by activation of K(ATP) channels CaMKII and NCX.
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Affiliation(s)
- Norishige Morita
- Translational Arrhythmia Research Section, Cardiovascular Research Laboratory, David Geffen School of Medicine at UCLA, 675 Charles E. Young Dr. South, MRL 3645 Mail Code: 176022, Los Angeles, CA 90095, USA
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Suppression of re-entrant and multifocal ventricular fibrillation by the late sodium current blocker ranolazine. J Am Coll Cardiol 2011; 57:366-75. [PMID: 21232675 DOI: 10.1016/j.jacc.2010.07.045] [Citation(s) in RCA: 95] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/15/2010] [Revised: 07/06/2010] [Accepted: 07/17/2010] [Indexed: 12/16/2022]
Abstract
OBJECTIVES The purpose of this study was to test the hypothesis that the late Na current blocker ranolazine suppresses re-entrant and multifocal ventricular fibrillation (VF). BACKGROUND VF can be caused by either re-entrant or focal mechanism. METHODS Simultaneous voltage and intracellular Ca(+)² optical mapping of the left ventricular epicardial surface along with microelectrode recordings was performed in 24 isolated-perfused aged rat hearts. Re-entrant VF was induced by rapid pacing and multifocal VF by exposure to oxidative stress with 0.1 mM hydrogen peroxide (H₂O₂). RESULTS Rapid pacing induced sustained VF in 7 of 8 aged rat hearts, characterized by 2 to 4 broad propagating wavefronts. Ranolazine significantly (p < 0.05) reduced the maximum slope of action potential duration restitution curve and converted sustained to nonsustained VF lasting 24 ± 8 s in all 7 hearts. Exposure to H₂O₂ initiated early afterdepolarization (EAD)-mediated triggered activity that led to sustained VF in 8 out of 8 aged hearts. VF was characterized by multiple foci, appearing at an average of 6.8 ± 3.2 every 100 ms, which remained confined to a small area averaging 2.8 ± 0.85 mm² and became extinct after a mean of 43 ± 16 ms. Ranolazine prevented (when given before H₂O₂) and suppressed H₂O₂-mediated EADs by reducing the number of foci, causing VF to terminate in 8 out of 8 hearts. Simulations in 2-dimensional tissue with EAD-mediated multifocal VF showed progressive reduction in the number of foci and VF termination by blocking the late Na current. CONCLUSIONS Late Na current blockade with ranolazine is effective at suppressing both pacing-induced re-entrant VF and EAD-mediated multifocal VF.
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22
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Haraguchi R, Ashihara T, Namba T, Tsumoto K, Murakami S, Kurachi Y, Ikeda T, Nakazawa K. Transmural dispersion of repolarization determines scroll wave behavior during ventricular tachyarrhythmias. Circ J 2010; 75:80-8. [PMID: 21099125 DOI: 10.1253/circj.cj-10-0071] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
BACKGROUND Ventricular tachyarrhythmia is the leading cause of sudden cardiac death, and scroll wave re-entry is known to underlie this condition. Class III antiarrhythmic drugs are commonly used worldwide to treat ventricular tachyarrhythmias; however, these drugs have a proarrhythmic adverse effect and can cause Torsade de Pointes or ventricular fibrillation. Transmural dispersion of repolarization (TDR) has been suggested to be a strong indicator of ventricular tachyarrhythmia induction. However, the role of TDR during sustained scroll wave re-entry is poorly understood. The purpose of the present study was to investigate how TDR affects scroll wave behavior and to provide a novel analysis of the mechanisms that sustain tachyarrhythmias, using computer simulations. METHODS AND RESULTS Computer simulations were carried out to quantify the TDR and QT interval under a variety of I(Ks) and I(Kr) during transmural conduction. Simulated scroll wave re-entries were done under a variety of I(Ks) and I(Kr) in a ventricular wall slab model, and the scroll wave behavior and the filament dynamics (3-dimensional organizing center) were analyzed. A slight increase in TDR, but not in the QT interval, reflected antiarrhythmic properties resulting from the restraint of scroll wave breakup, whereas a marked increase in TDR was proarrhythmic, as a result of scroll wave breakup. CONCLUSIONS The TDR determines the sustainment of ventricular tachyarrhythmias, through control of the scroll wave filament dynamics.
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Affiliation(s)
- Ryo Haraguchi
- National Cerebral and Cardiovascular Center Research Institute, Suita, Japan.
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23
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Morita N, Sovari AA, Xie Y, Fishbein MC, Mandel WJ, Garfinkel A, Lin SF, Chen PS, Xie LH, Chen F, Qu Z, Weiss JN, Karagueuzian HS. Increased susceptibility of aged hearts to ventricular fibrillation during oxidative stress. Am J Physiol Heart Circ Physiol 2009; 297:H1594-605. [PMID: 19767530 DOI: 10.1152/ajpheart.00579.2009] [Citation(s) in RCA: 101] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Abstract
Oxidative stress with hydrogen peroxide (H(2)O(2)) readily promotes early afterdepolarizations (EADs) and triggered activity (TA) in isolated rat and rabbit ventricular myocytes. Here we examined the effects of H(2)O(2) on arrhythmias in intact Langendorff rat and rabbit hearts using dual-membrane voltage and intracellular calcium optical mapping and glass microelectrode recordings. Young adult rat (3-5 mo, N = 25) and rabbit (3-5 mo, N = 6) hearts exhibited no arrhythmias when perfused with H(2)O(2) (0.1-2 mM) for up to 3 h. However, in 33 out of 35 (94%) aged (24-26 mo) rat hearts, 0.1 mM H(2)O(2) caused EAD-mediated TA, leading to ventricular tachycardia (VT) and fibrillation (VF). Aged rabbits (life span, 8-12 yr) were not available, but 4 of 10 middle-aged rabbits (3-5 yr) developed EADs, TA, VT, and VF. These arrhythmias were suppressed by the reducing agent N-acetylcysteine (2 mM) and CaMKII inhibitor KN-93 (1 microM) but not by its inactive form (KN-92, 1 microM). There were no significant differences between action potential duration (APD) or APD restitution slope before or after H(2)O(2) in aged or young adult rat hearts. In histological sections, however, trichrome staining revealed that aged rat hearts exhibited extensive fibrosis, ranging from 10-90%; middle-aged rabbit hearts had less fibrosis (5-35%), whereas young adult rat and rabbit hearts had <4% fibrosis. In aged rat hearts, EADs and TA arose most frequently (70%) from the left ventricular base where fibrosis was intermediate ( approximately 30%). Computer simulations in two-dimensional tissue incorporating variable degrees of fibrosis showed that intermediate (but not mild or severe) fibrosis promoted EADs and TA. We conclude that in aged ventricles exposed to oxidative stress, fibrosis facilitates the ability of cellular EADs to emerge and generate TA, VT, and VF at the tissue level.
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Affiliation(s)
- Norishige Morita
- Translational Arrhythmia Research Laboratory and Cardiovascular Research Laboratory, Division of Cardiology, Department of Medicine, David Geffen School of Medicine at University of California, Los Angeles, USA
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Holcomb MR, Woods MC, Uzelac I, Wikswo JP, Gilligan JM, Sidorov VY. The potential of dual camera systems for multimodal imaging of cardiac electrophysiology and metabolism. Exp Biol Med (Maywood) 2009; 234:1355-73. [PMID: 19657065 DOI: 10.3181/0902-rm-47] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022] Open
Abstract
Fluorescence imaging has become a common modality in cardiac electrodynamics. A single fluorescent parameter is typically measured. Given the growing emphasis on simultaneous imaging of more than one cardiac variable, we present an analysis of the potential of dual camera imaging, using as an example our straightforward dual camera system that allows simultaneous measurement of two dynamic quantities from the same region of the heart. The advantages of our system over others include an optional software camera calibration routine that eliminates the need for precise camera alignment. The system allows for rapid setup, dichroic image separation, dual-rate imaging, and high spatial resolution, and it is generally applicable to any two-camera measurement. This type of imaging system offers the potential for recording simultaneously not only transmembrane potential and intracellular calcium, two frequently measured quantities, but also other signals more directly related to myocardial metabolism, such as [K(+)](e), NADH, and reactive oxygen species, leading to the possibility of correlative multimodal cardiac imaging. We provide a compilation of dye and camera information critical to the design of dual camera systems and experiments.
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Affiliation(s)
- Mark R Holcomb
- Department of Physics and Astronomy, Vanderbilt University, Nashville, Tennessee 37235-1807, USA
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Enjoji Y, Mizobuchi M, Muranishi H, Miyamoto C, Utsunomiya M, Funatsu A, Kobayashi T, Nakamura S. Catheter ablation of fatal ventricular tachyarrhythmias storm in acute coronary syndrome—role of Purkinje fiber network. J Interv Card Electrophysiol 2009; 26:207-15. [DOI: 10.1007/s10840-009-9394-7] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/07/2009] [Accepted: 02/25/2009] [Indexed: 11/30/2022]
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Shajahan TK, Nayak AR, Pandit R. Spiral-wave turbulence and its control in the presence of inhomogeneities in four mathematical models of cardiac tissue. PLoS One 2009; 4:e4738. [PMID: 19270753 PMCID: PMC2650787 DOI: 10.1371/journal.pone.0004738] [Citation(s) in RCA: 61] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/07/2008] [Accepted: 01/21/2009] [Indexed: 12/02/2022] Open
Abstract
Regular electrical activation waves in cardiac tissue lead to the rhythmic contraction and expansion of the heart that ensures blood supply to the whole body. Irregularities in the propagation of these activation waves can result in cardiac arrhythmias, like ventricular tachycardia (VT) and ventricular fibrillation (VF), which are major causes of death in the industrialised world. Indeed there is growing consensus that spiral or scroll waves of electrical activation in cardiac tissue are associated with VT, whereas, when these waves break to yield spiral- or scroll-wave turbulence, VT develops into life-threatening VF: in the absence of medical intervention, this makes the heart incapable of pumping blood and a patient dies in roughly two-and-a-half minutes after the initiation of VF. Thus studies of spiral- and scroll-wave dynamics in cardiac tissue pose important challenges for in vivo and in vitro experimental studies and for in silico numerical studies of mathematical models for cardiac tissue. A major goal here is to develop low-amplitude defibrillation schemes for the elimination of VT and VF, especially in the presence of inhomogeneities that occur commonly in cardiac tissue. We present a detailed and systematic study of spiral- and scroll-wave turbulence and spatiotemporal chaos in four mathematical models for cardiac tissue, namely, the Panfilov, Luo-Rudy phase 1 (LRI), reduced Priebe-Beuckelmann (RPB) models, and the model of ten Tusscher, Noble, Noble, and Panfilov (TNNP). In particular, we use extensive numerical simulations to elucidate the interaction of spiral and scroll waves in these models with conduction and ionic inhomogeneities; we also examine the suppression of spiral- and scroll-wave turbulence by low-amplitude control pulses. Our central qualitative result is that, in all these models, the dynamics of such spiral waves depends very sensitively on such inhomogeneities. We also study two types of control schemes that have been suggested for the control of spiral turbulence, via low amplitude current pulses, in such mathematical models for cardiac tissue; our investigations here are designed to examine the efficacy of such control schemes in the presence of inhomogeneities. We find that a local pulsing scheme does not suppress spiral turbulence in the presence of inhomogeneities; but a scheme that uses control pulses on a spatially extended mesh is more successful in the elimination of spiral turbulence. We discuss the theoretical and experimental implications of our study that have a direct bearing on defibrillation, the control of life-threatening cardiac arrhythmias such as ventricular fibrillation.
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Affiliation(s)
- T. K. Shajahan
- Centre for Condensed Matter Theory, Department of Physics, Indian Institute of Science, Bangalore, India
- Indian Institute of Science Eduation and Research (IISER), Thiruvananthapuram, CET Campus, Thiruvananthapuram, Kerala, India
| | - Alok Ranjan Nayak
- Centre for Condensed Matter Theory, Department of Physics, Indian Institute of Science, Bangalore, India
| | - Rahul Pandit
- Centre for Condensed Matter Theory, Department of Physics, Indian Institute of Science, Bangalore, India
- Jawaharlal Nehru Centre for Advanced Scientific Research, Bangalore, India
- * E-mail:
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Choi JI, Pak HN, Park JH, Choi EJ, Kim SK, Kwak JJ, Jang JK, Hwang C, Kim YH. Clinical significance of complete conduction block of the left lateral isthmus and its relationship with anatomical variation of the vein of Marshall in patients with nonparoxysmal atrial fibrillation. J Cardiovasc Electrophysiol 2009; 20:616-22. [PMID: 19207770 DOI: 10.1111/j.1540-8167.2008.01408.x] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
BACKGROUND The vein of Marshall (VOM), which exists along the left lateral isthmus (LLI), constitutes a muscular connection between the coronary sinus (CS) and the left atrium (LA). We hypothesized that anatomical variation of the VOM affects the bidirectional block of LLI and the clinical outcome in patients with nonparoxysmal atrial fibrillation (NPAF). METHODS Among 73 patients with NPAF, 54 patients (47 male, 54.1 +/- 10.4 years old) with a clearly visible VOM (74.0%) were included. After circumferential antral ablation, double linear endocardial ablation of LLI was performed along the VOM. Unless LLI block was achievable by endocardial ablation, the ablation was performed inside the CS. RESULTS LLI block was achievable in 35 patients (64.8%; 11.1% by endocardial ablation vs 53.7% by additional inside CS ablation; P < 0.01). In patients with failed LLI block, the VOM was significantly longer (P < 0.05) on the right anterior oblique (RAO) view than in those with successful LLI block. LA volume or LLI length measured by CT image were not different (P = NS). During 11.4 +/- 5.0 months follow-up, early recurrences within 3 months (47.4% vs 28.6%, P = NS) and recurrences after 3 months (10.5% vs 17.7%, P = NS) were not different with or without LLI block. CONCLUSION LLI block, which is more difficult to achieve in patients with a longer VOM, was achievable in 65% of patients with NPAF by linear ablation along the VOM and additional inside CS ablation, but did not affect the short-term clinical outcome.
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Affiliation(s)
- Jong-Il Choi
- Korea University Cardiovascular Center, Seoul, Republic of Korea
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28
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Rodriguez E, Lerma C, Echeverria JC, Alvarez-Ramirez J. ECG scaling properties of cardiac arrhythmias using detrended fluctuation analysis. Physiol Meas 2008; 29:1255-66. [DOI: 10.1088/0967-3334/29/11/002] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
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29
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Tang L, Hwang GS, Hayashi H, Song J, Ogawa M, Kobayashi K, Joung B, Karagueuzian HS, Chen PS, Lin SF. Intracellular calcium dynamics at the core of endocardial stationary spiral waves in Langendorff-perfused rabbit hearts. Am J Physiol Heart Circ Physiol 2008; 295:H297-304. [PMID: 18487432 DOI: 10.1152/ajpheart.00137.2008] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
In vitro models of sustained monomorphic ventricular tachycardia (MVT) are rare and do not usually show spiral reentry on the epicardium. We hypothesized that MVT is associated with the spiral wave in the endocardium and that this stable reentrant propagation is supported by a persistently elevated intracellular calcium (Ca(i)) transient at the core of the spiral wave. We performed dual optical mapping of transmembrane potential (V(m)) and Ca(i) dynamics of the right ventricular (RV) endocardium in Langendorff-perfused rabbit hearts (n = 12). Among 64 induced arrhythmias, 55% were sustained MVT (>10 min). Eighty percent of MVT showed stationary spiral waves (>10 cycles, cycle length: 128 +/- 14.6 ms) in the endocardial mapped region, anchoring to the anatomic discontinuities. No reentry activity was observed in the epicardium. During reentry, the amplitudes of V(m) and Ca(i) signals were higher in the periphery and gradually decreased toward the core. At the core, maximal V(m) and Ca(i) amplitudes were 42.95 +/- 5.89% and 43.95 +/- 9.46%, respectively, of the control (P < 0.001). However, the trough of the V(m) and Ca(i) signals at the core were higher than those in the periphery, indicating persistent V(m) and Ca(i) elevations during reentry. BAPTA-AM, a calcium chelator, significantly reduced the maximal Ca(i) transient amplitude and prevented sustained MVT and spiral wave formation in the mapped region. These findings indicate that endocardial spiral waves often anchor to anatomic discontinuities causing stable MVT in normal rabbit ventricles. The spiral core is characterized by diminished V(m) and Ca(i) amplitudes and persistent V(m) and Ca(i) elevations during reentry.
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Affiliation(s)
- Liang Tang
- Krannert Institute of Cardiology, Indiana Univ. School of Medicine, Indianapolis, IN 46202, USA
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30
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Irimia A, Wikswo JP. Gastrointestinal arrhythmias are associated with statistically significant fluctuations in systemic information dimension. Physiol Meas 2008; 29:N33-40. [PMID: 18427160 PMCID: PMC7722964 DOI: 10.1088/0967-3334/29/5/n01] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Abstract
Although cardiac arrhythmias have been studied extensively, little is known about arrhythmic phenomena in the gastrointestinal (GI) system. In this study, we demonstrate for the first time that the onset of GI arrhythmias is associated with statistically significant fluctuations in the information dimension of the associated systems. We induced gastric and intestinal arrhythmias in pigs using surgical stomach division and mesenteric artery ligation, respectively. Both conditions lead to a decreased supply of blood to the GI tract, which is associated in humans with various potentially lethal conditions including chronic mesenteric ischemia, whose mortality rate is over 60%. During our experiments, we recorded simultaneous magnetocardiographic, magnetogastrographic and magnetoenterographic signals and concluded that, when GI circulation is compromised, the information dimensionality of the system fluctuates significantly. In conclusion, dimensionality may be an important diagnostic factor for the characterization of arrhythmias in the context of GI pathophysiology.
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Affiliation(s)
- Andrei Irimia
- Department of Physics and Astronomy, Vanderbilt University, Nashville, TN 37235, USA
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31
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Lever NA, Newall EG, Larsen PD. Differences in the characteristics of induced and spontaneous episodes of ventricular fibrillation. ACTA ACUST UNITED AC 2007; 9:1054-8. [PMID: 17872925 DOI: 10.1093/europace/eum194] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022]
Abstract
AIMS The degree of organization of ventricular fibrillation (VF) can be examined in terms of the regularity of the electrical activity within the ventricle. Using electrograms (EGMs) stored within implanted cardioverter defibrillators (ICDs), we examined the hypothesis that the degree of organization, or regularity, was different if the VF was induced by electrical stimulation as opposed to occurring clinically due to ischemia or scar. METHODS AND RESULTS We compared the statistical characteristics of EGMs recorded by ICDs during spontaneous episodes with those induced during device testing in the laboratory in nine subjects. Regularity of the VF EGM signals was quantified using autocorrelation, Shannon entropy (derived from cycle to cycle activation complexes), and Kolmogorov entropy (derived from eight second long episodes of VF). All three measurements showed a statistically greater degree of regularity for induced VF than in spontaneous episodes. CONCLUSION Analysis of VF EGMs using these techniques is novel and robust, providing a new way for assessing electrical organization during VF. The clinical significance and utility of differences in VF waveform regularity is unclear at this stage.
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Affiliation(s)
- Nigel A Lever
- Department of Medicine, University of Auckland, Auckland, New Zealand
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32
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Huang J, Cheng KA, Dosdall DJ, Smith WM, Ideker RE. Role of maximum rate of depolarization in predicting action potential duration during ventricular fibrillation. Am J Physiol Heart Circ Physiol 2007; 293:H2530-6. [PMID: 17704288 DOI: 10.1152/ajpheart.00793.2007] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
During ventricular fibrillation (VF) only 39% of the variation in action potential duration (APD) is accounted for by the previous diastolic interval [DI((n-1))], i.e., restitution, and the previous APD [APD((n-1))], i.e., memory. We tested the hypothesis that a characteristic of the AP upstroke, the maximum rate of depolarization (V(max)), also helps account for its APD. A floating microelectrode was used to make transmembrane recordings at 16,000 samples/s from the anterior left ventricular wall during four 20-s episodes of VF in each of six pigs. V(max), time from V(max) to 60% repolarization (APD(60)), and DI were calculated throughout all episodes. Stepwise linear regression was used to determine how well each APD(60) (APD(60n)) was predicted by V(max) of that AP, the four previous DIs (n-1, n - 2, n - 3, n - 4), and the three previous APD(60)s (n-1, n - 2, n - 3). V(max) entered in the regression equation significantly more often (86% of VF episodes) than either APD((n-1)) (47% of episodes) or DI((n-1)) (58% of episodes). When these three variables entered first or second, their coefficients were almost always positive, consistent with a longer APD associated with 1) a larger V(max), 2) a longer APD((n-1)), and 3) a longer DI((n-1)). R(2) of the regression for all entered variables was 0.51 +/- 0.01 (mean +/- SD). During the first 20 s of VF in swine, V(max) is a more important determinant of APD than the previous DI (restitution) or the previous APD (memory). All variables together account for only one-half of APD variation during VF.
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Affiliation(s)
- Jian Huang
- Cardiac Rhythm Management Laboratory, Division of Cardiovascular Disease, Department of Medicine, University of Alabama at Birmingham, Birmingham, Alabama 35294-0019, USA.
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33
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Tang L, Hwang GS, Song J, Chen PS, Lin SF. Post-shock synchronized pacing in isolated rabbit left ventricle: evaluation of a novel defibrillation strategy. J Cardiovasc Electrophysiol 2007; 18:740-9. [PMID: 17388914 DOI: 10.1111/j.1540-8167.2007.00792.x] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
INTRODUCTION A failed near-threshold defibrillation shock is followed by an isoelectric window (IEW) and rapid repetitive responses that reinitiate ventricular fibrillation (VF). We hypothesized that properly timed (synchronized) postshock pacing stimuli (SyncP) may capture the recovered tissues during the repetitive responses and prevent postshock reinitiation of VF, resulting in improved defibrillation efficacy. METHODS AND RESULTS We explored the effect of postshock SyncP on defibrillation efficacy in isolated rabbit hearts (n = 12). Optical recording-guided real-time detection and electrical stimulation (5 mA) of recovered tissues in anterior/posterior left ventricle (LV) were performed following IEW. The IEW duration was found to be 69 +/- 13 ms. With the same shock strength, successful and failed defibrillation episodes were associated with 50% and 15% of the myocardium, respectively, captured by the SyncP (P < 0.001). Electrical stimulation from the posterior LV resulted in 75% of episodes capturing myocardium, as compared with anterior LV stimulation (55%; P < 0.01) and higher successful defibrillation rate (14%, posterior vs. 3%, anterior LV). The overall success in terminating VF by postshock SyncP was approximately 10%. The causes for failed myocardium capture by postshock SyncP included lack of IEW after low-strength shock (42.9%), incorrect locations of reference site (25.7%) and pacing electrodes (17.9%), and others, such as wave breakthroughs (13.5%). CONCLUSION Postshock SyncP was feasible and the larger the myocardium captured area, the more likely was the successful defibrillation. Postshock SyncP delivered to the posterior LV was more effective than anterior LV to terminate VF.
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Affiliation(s)
- Liang Tang
- Division of Cardiology, Department of Medicine, Cedars-Sinai Medical Center and David Geffen School of Medicine, UCLA, Los Angeles, California 90048, USA
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34
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Chorro FJ, Blasco E, Trapero I, Cánoves J, Ferrero A, Mainar L, Such-Miquel L, Sanchis J, Bodí V, Cerdá JM, Alberola A, Such L. Selective Myocardial Isolation and Ventricular Fibrillation. PACING AND CLINICAL ELECTROPHYSIOLOGY: PACE 2007; 30:359-70. [PMID: 17367355 DOI: 10.1111/j.1540-8159.2007.00676.x] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
BACKGROUND Few experimental studies have analyzed the effects of selective radiofrequency (RF) lesions upon ventricular fibrillation (VF). The RF-induced isolation of selected zones would make it possible to determine whether these zones are essential for existence of the arrhythmia. METHODS In 31 Langendorff-perfused rabbit hearts, the characteristics and inducibility of VF were analyzed before and after the induction of RF lesions comprising: (1) the posterior zone of the septum and of the walls of both ventricles (n = 10); (2) the anterior zone of the septum and of the walls of both ventricles (n = 11); and (3) the midseptal zone (n = 10). RESULTS Complete isolation of the zone encompassed by the lesions was obtained in 5, 6, and 5 experiments of series 1, 2, and 3, respectively. In these experiments, the arrhythmia was only induced from within the zone encompassed by the lesions in one experiment belonging to series 2 (P < 0.05 with respect to baseline). In contrast, in all but one of the cases in series 2, VF could be induced from outside the isolated zone (ns vs baseline). Partial isolation was obtained in five experiments of each series. In these experiments, on pacing from within the partially isolated zone, sustained VF was not induced in any experiment (P < 0.05 with respect to baseline), while in all cases VF could be induced on pacing from the external zone (ns vs baseline). CONCLUSION In the experimental model used, the three zones studied were not essential for maintaining VF. In most cases, their partial or total isolation avoided inducibility of the arrhythmia in those zones, though not in the remaining myocardium.
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Affiliation(s)
- Francisco J Chorro
- Service of Cardiology, Valencia University Clinic Hospital, Valencia, Spain.
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35
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Pak HN, Kim YH, Lim HE, Chou CC, Miyauchi Y, Fang YH, Sun K, Hwang C, Chen PS. Role of the Posterior Papillary Muscle and Purkinje Potentials in the Mechanism of Ventricular Fibrillation in Open Chest Dogs and Swine: Effects of Catheter Ablation. J Cardiovasc Electrophysiol 2006; 17:777-83. [PMID: 16836678 DOI: 10.1111/j.1540-8167.2006.00511.x] [Citation(s) in RCA: 68] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Abstract
BACKGROUND Papillary muscle (PM) ablation may terminate ventricular fibrillation (VF) in rabbit hearts. Whether or not PM ablation prevents ventricular fibrillation (VF) induction in large animals is unknown. METHODS We performed noncontact endocardial mapping and/or high-density epicardial mapping during VF in 12 dogs and 16 swine and tested the effects of posterior PM (PPM) ablation on VF inducibility. RESULTS During VF in progressive global ischemia (3 swine and 2 dogs), the highest dominant frequency (DF) was near PPM. The majority of the reentrant wavefronts during a propranolol infusion (swine) were anchored to the PPM. Purkinje potentials onset were recorded on the PPM both during sinus rhythm and during VF. Radiofrequency (RF) ablation of the endocardium on the PPM with a linear extension of the ablation line from the PPM to the mitral valve annulus and then the left ventricular apex in 7 dogs reduced the VF inducibility from 100% at baseline to 22% after ablation (P < 0.0001). RF applications to the anterolateral wall of dogs (n = 3) did not prevent VF induction. The application of RF energy near the PPM frequently initiated VF in swine (n = 7), preventing subsequent testing of VF inducibility. CONCLUSION In dogs and swine, the highest DF and majority of reentrant wavefronts during VF with acute global ischemia or during a propranolol infusion were located on the PPM. RF ablation targeted at the PPM reduced the inducibility of VF in normal dogs. However, the same ablation provoked incessant VF in swine, preventing subsequent testing of VF inducibility.
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Affiliation(s)
- Hui-Nam Pak
- Korea University Cardiovascular Center, Seoul, Republic of Korea
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36
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Bien H, Yin L, Entcheva E. Calcium instabilities in mammalian cardiomyocyte networks. Biophys J 2006; 90:2628-40. [PMID: 16399841 PMCID: PMC1403171 DOI: 10.1529/biophysj.105.063321] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/22/2005] [Accepted: 12/15/2005] [Indexed: 11/18/2022] Open
Abstract
The degeneration of a regular heart rhythm into fibrillation (a chaotic or chaos-like sequence) can proceed via several classical routes described by nonlinear dynamics: period-doubling, quasiperiodicity, or intermittency. In this study, we experimentally examine one aspect of cardiac excitation dynamics, the long-term evolution of intracellular calcium signals in cultured cardiomyocyte networks subjected to increasingly faster pacing rates via field stimulation. In this spatially extended system, we observed alternans and higher-order periodicities, extra beats, and skipped beats or blocks. Calcium instabilities evolved nonmonotonically with the prevalence of phase-locking or Wenckebach rhythm, low-frequency magnitude modulations (signature of quasiperiodicity), and switches between patterns with occasional bursts (signature of intermittency), but period-doubling bifurcations were rare. Six ventricular-fibrillation-resembling episodes were pace-induced, for which significantly higher complexity was confirmed by approximate entropy calculations. The progressive destabilization of the heart rhythm by coexistent frequencies, seen in this study, can be related to theoretically predicted competition of control variables (voltage and calcium) at the single-cell level, or to competition of excitation and recovery at the cell network level. Optical maps of the response revealed multiple local spatiotemporal patterns, and the emergence of longer-period global rhythms as a result of wavebreak-induced reentries.
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Affiliation(s)
- Harold Bien
- Department of Biomedical Engineering, Stony Brook University, Stony Brook, New York 11794-8181, USA
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37
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Qu Z. Critical mass hypothesis revisited: role of dynamical wave stability in spontaneous termination of cardiac fibrillation. Am J Physiol Heart Circ Physiol 2005; 290:H255-63. [PMID: 16113075 PMCID: PMC3644506 DOI: 10.1152/ajpheart.00668.2005] [Citation(s) in RCA: 55] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The tendency of atrial or ventricular fibrillation to terminate spontaneously in finite-sized tissue is known as the critical mass hypothesis. Previous studies have shown that dynamical instabilities play an important role in creating new wave breaks that maintain cardiac fibrillation, but its role in self-termination, in relation to tissue size and geometry, is not well understood. This study used computer simulations of two- and three-dimensional tissue models to investigate qualitatively how, in relation to tissue size and geometry, dynamical instability affects the spontaneous termination of cardiac fibrillation. The major findings are as follows: 1) Dynamical instability promotes wave breaks, maintaining fibrillation, but it also causes the waves to extinguish, facilitating spontaneous termination of fibrillation. The latter effect predominates as dynamical instability increases, so that fibrillation is more likely to self-terminate in a finite-sized tissue. 2) In two-dimensional tissue, the average duration of fibrillation increases exponentially as tissue area increases. In three-dimensional tissue, the average duration of fibrillation decreases initially as tissue thickness increases as a result of thickness-induced instability but then increases after a critical thickness is reached. Therefore, in addition to tissue mass and geometry, dynamical instability is an important factor influencing the maintenance of cardiac fibrillation.
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Affiliation(s)
- Zhilin Qu
- Department of Medicine (Cardiology), David Geffen School of Medicine at UCLA, 47-123 CHS, 10833 Le Conte Ave., Los Angeles, CA 90095, USA.
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38
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Abstract
Background—
Although restitution has been hypothesized to determine action potential duration (APD) during ventricular fibrillation (VF), cardiac memory may also be important.
Methods and Results—
Transmembrane recordings were made with a floating microelectrode from the anterior right ventricular wall in 6 pigs during up to 60 seconds of VF. The recordings were divided into 5-second intervals, and APD
60
and the diastolic interval (DI) were calculated for each activation cycle throughout each interval. Stepwise linear regression was used to determine how well each APD
60
[APD
60
(n)] was predicted by the 4 previous DIs (n−1, n−2, n−3, n−4) and the 3 previous APD
60
s (n−1, n−2, n−3). A mean±SD of 3±1.5 of the variables entered the regression equation. DI(n−1) (70% of intervals) and APD
60
(n−1) (71% of intervals) appeared most frequently in the regression equations and were the first or second variables entered during the stepwise regression in 87% and 76% of the intervals in which they were present, respectively. The coefficients of DI(n−1) and APD
60
(n−1) were positive 89% and 98% of the time, respectively.
R
2
of the regression for all entered variables during all intervals was 0.39±0.05.
Conclusions—
The high incidence and positive coefficient of DI(n−1) indicate that restitution is important in determining APD during VF, whereas the similarly high incidence and positive coefficient of APD(n−1) indicate that cardiac memory is equally important. The finding that the regression equation accounts for only 39% of the variability of APD indicates that factors other than restitution and memory are also important in determining APD during VF.
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Affiliation(s)
- Jian Huang
- Cardiac Rhythm Management Laboratory, Division of Cardiovascular Disease, Department of Medicine, University of Alabama at Birmingham, Volker Hall B140, 1530 3rd Ave S, Birmingham, AL 35294-0019, USA.
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Kay MW, Amison PM, Rogers JM. Three-Dimensional Surface Reconstruction and Panoramic Optical Mapping of Large Hearts. IEEE Trans Biomed Eng 2004; 51:1219-29. [PMID: 15248538 DOI: 10.1109/tbme.2004.827261] [Citation(s) in RCA: 49] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
Optical mapping of electrical activity from the surface of the heart is a powerful tool for studying complex arrhythmias. However, a limitation of traditional optical mapping is that the mapped region is restricted to the field of view of the sensor, which makes it difficult to track electrical waves as they drift in and out of view. To address this, we developed an optical system that panoramically maps epicardial electrical activity in three dimensions. The system was engineered to accomodate hearts comparable in size to human hearts. It is comprised of a surface scanner that measures epicardial geometry and a panoramic fluorescence imaging system that records electrical activity. Custom software texture maps the electrical data onto a reconstructed epicardial surface. The result is a high resolution, spatially contiguous, mapping dataset. In addition, the three-dimensional positions of the recording sites are known, making it possible to accurately measure parameters that require geometric information, such as propagation velocity. In this paper, we describe the system and demonstrate it by mapping a swine heart.
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Affiliation(s)
- Matthew W Kay
- Department of Biomedical Engineering, University of Alabama at Birmingham, Birmingham, AL 35294-0019, USA.
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40
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Cherry EM, Fenton FH. Suppression of alternans and conduction blocks despite steep APD restitution: electrotonic, memory, and conduction velocity restitution effects. Am J Physiol Heart Circ Physiol 2004; 286:H2332-41. [PMID: 14751863 DOI: 10.1152/ajpheart.00747.2003] [Citation(s) in RCA: 177] [Impact Index Per Article: 8.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
We examine the utility of the action potential (AP) duration (APD) restitution curve slope in predicting the onset of electrical alternans when electrotonic and memory effects are considered. We develop and use two ionic cell models without memory that have the same restitution curve with slope >1 but different AP shapes and, therefore, different electrotonic effects. We also study a third cell model that incorporates short-term memory of previous cycle lengths, so that it has a family of S1-S2 restitution curves as well as a dynamic restitution curve with slope >1. Our results indicate that both electrotonic and memory effects can suppress alternans, even when the APD restitution curve is steep. In the absence of memory, electrotonic currents related to the shape of the AP, as well as conduction velocity restitution, can affect how alternans develops in tissue and, in some cases, can prevent its induction entirely, even when isolated cells exhibit alternans. When short-term memory is included, alternans may not occur in isolated cells, despite a steep APD restitution curve, and may or may not occur in tissue, depending on conduction velocity restitution. We show for the first time that electrotonic and memory effects can prevent conduction blocks and stabilize reentrant waves in two and three dimensions. Thus we find that the slope of the APD restitution curve alone does not always well predict the onset of alternans and that incorporating electrotonic and memory effects may provide a more useful alternans criterion. A Data Supplement containing movies and JAVA applets is available online at http://ajpheart.physiology.org/cgi/content/full/00747.2003/DC1 .
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Affiliation(s)
- Elizabeth M Cherry
- Department of Physics, CHPHB 102, Hofstra University, Hempstead, NY 11549, USA
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41
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Chou CC, Zhou S, Miyauchi Y, Pak HN, Okuyama Y, Fishbein MC, Karagueuzian HS, Chen PS. Effects of procainamide on electrical activity in thoracic veins and atria in canine model of sustained atrial fibrillation. Am J Physiol Heart Circ Physiol 2004; 286:H1936-45. [PMID: 15072975 DOI: 10.1152/ajpheart.00754.2003] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Focal discharges (FDs) are present in thoracic veins during atrial fibrillation (AF). We hypothesize that procainamide exerts its anti-AF action by suppressing FDs in the thoracic veins. We studied six mongrel dogs (22-27 kg) with sustained (>6 h) AF induced by 47 +/- 20 days of chronic rapid LA appendage (LAA) or pulmonary vein (PV) pacing. Procainamide was infused intravenously until AF was terminated or a cumulative dose of 20 mg/kg was reached. High-resolution mapping during AF showed FDs in the vein of Marshall, PVs, and the LAA. Procainamide significantly (P < 0.05) reduced the frequency of these FDs and suppressed the interactions of wave fronts between PVs and LA. The cumulative dose of PA needed to terminate AF correlated negatively (r =-0.9, P < 0.05) with the baseline effective refractory period (ERP) of PV and positively (r = 0.8, P < 0.05) with the baseline maximum dominant frequency (DF) of AF. In four of five dogs, AF converted to atrial tachycardia originating from the PVs before termination. Attempts to reinduce sustained AF were unsuccessful in these five dogs. AF was resistant to procainamide in the sixth dog. In conclusion, procainamide reduced the rate of FDs in the thoracic veins and the LA and suppressed the interaction between PVs and LA. Second, FDs in the PV are more resistant to procainamide's action than FDs in the atria. Third, inherent PV ERP is important in determining the antifibrillatory efficacy of procainamide.
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Affiliation(s)
- Chung-Chuan Chou
- Division of Cardiology, Department of Medicine, Cedars-Sinai Medical Center, Los Angeles, California 90048, USA
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42
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Omichi C, Lamp ST, Lin SF, Yang J, Baher A, Zhou S, Attin M, Lee MH, Karagueuzian HS, Kogan B, Qu Z, Garfinkel A, Chen PS, Weiss JN. Intracellular Ca dynamics in ventricular fibrillation. Am J Physiol Heart Circ Physiol 2004; 286:H1836-44. [PMID: 14704235 DOI: 10.1152/ajpheart.00123.2003] [Citation(s) in RCA: 74] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
In the heart, membrane voltage ( Vm) and intracellular Ca (Cai) are bidirectionally coupled, so that ionic membrane currents regulate Cai cycling and Cai affects ionic currents regulating action potential duration (APD). Although Cai reliably and consistently tracks Vm at normal heart rates, it is possible that at very rapid rates, sarcoplasmic reticulum Cai cycling may exhibit intrinsic dynamics. Non-voltage-gated Cai release might cause local alternations in APD and refractoriness that influence wavebreak during ventricular fibrillation (VF). In this study, we tested this hypothesis by examining the extent to which Cai is associated with Vm during VF. Cai transients were mapped optically in isolated arterially perfused swine right ventricles using the fluorescent dye rhod 2 AM while intracellular membrane potential was simultaneously recorded either locally with a microelectrode (5 preparations) or globally with the voltage-sensitive dye RH-237 (5 preparations). Mutual information (MI) is a quantitative statistical measure of the extent to which knowledge of one variable ( Vm) predicts the value of a second variable (Cai). MI was high during pacing and ventricular tachycardia (VT; 1.13 ± 0.21 and 1.69 ± 0.18, respectively) but fell dramatically during VF (0.28 ± 0.06, P < 0.001). Cai at sites 4–6 mm apart also showed decreased MI during VF (0.63 ± 0.13) compared with pacing (1.59 ± 0.34, P < 0.001) or VT (2.05 ± 0.67, P < 0.001). Spatially, Cai waves usually bore no relationship to membrane depolarization waves during nonreentrant fractionated waves typical of VF, whereas they tracked each other closely during pacing and VT. The dominant frequencies of Vm and Cai signals analyzed by fast Fourier transform were similar during VT but differed significantly during VF. Cai is closely associated with Vm closely during pacing and VT but not during VF. These findings suggest that during VF, non-voltage-gated Cai release events occur and may influence wavebreak by altering Vm and APD locally.
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Affiliation(s)
- Chikaya Omichi
- Division of Cardiology, Cedars-Sinai Medical Center and Center for Health Sciences, University of California-Los Angeles Cardiovascular Research Laboratory, David Geffen School of Medicine, UCLA, Los Angeles, California 90095-1760, USA
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Banville I, Chattipakorn N, Gray RA. Restitution Dynamics During Pacing and Arrhythmias in Isolated Pig Hearts. J Cardiovasc Electrophysiol 2004; 15:455-63. [PMID: 15089996 DOI: 10.1046/j.1540-8167.2004.03330.x] [Citation(s) in RCA: 72] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
INTRODUCTION The dependence of action potential duration (APD) on the preceding diastolic interval (DI), i.e., restitution, has been purported to predict the development of alternans and reentrant arrhythmias. However, restitution depends on the history of activation (i.e., memory), and its relevance to arrhythmia induction and maintenance is unknown. METHODS AND RESULTS Using a dual-camera video imaging system, we recorded action potentials from thousands of sites on the surface of the isolated pig heart. A steady-state pacing (SSP) protocol was performed to generate the SSP APD restitution curve. During SSP, the minimum DI and APD were 57 +/- 6 ms and 107 +/- 6 ms, respectively. The restitution slope was >1 for DIs <85 +/- 5 ms; however, alternans were not observed. Abrupt decreases in cycle length (CL) resulted in a rapid (<5 beats) decrease in APD followed by a slower decrease to "steady state." DI, APD pairs for the initial beats following these rate changes were significantly above the SSP restitution curve. DI, APD pairs measured during sustained ventricular fibrillation clustered significantly below the SSP restitution curve, at significantly shorter APDs (57 +/- 4 ms) and DIs (49 +/- 6 ms) than could be achieved during SSP. In addition, abrupt increases in CL following SSP resulted in APDs significantly shorter than those predicted from the SSP restitution curve. CONCLUSION Our results indicate that the responses of APD and DI to sudden rate changes and during arrhythmias are not predicted by the SSP restitution relationship. Acute dynamics act to damp out the proarrhythmic oscillations predicted from the SSP restitution curve.
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Affiliation(s)
- Isabelle Banville
- Department of Biomedical Engineering, University of Alabama at Birmingham, 1670 University Boulevard, Birmingham, AL 35294, USA
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Pak HN, Oh YS, Liu YB, Wu TJ, Karagueuzian HS, Lin SF, Chen PS. Catheter Ablation of Ventricular Fibrillation in Rabbit Ventricles Treated With β-Blockers. Circulation 2003; 108:3149-56. [PMID: 14656917 DOI: 10.1161/01.cir.0000104563.12408.12] [Citation(s) in RCA: 56] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
BACKGROUND A therapeutic implication of the focal-source hypothesis of ventricular fibrillation (VF) is that VF can be terminated by focal ablation. We hypothesize that beta-adrenergic receptor blockade converts multiple-wavelet VF to focal-source VF and that this focal source is located near the papillary muscle (PM). METHODS AND RESULTS We used optical mapping techniques to study the effects of propranolol (0.3 mg/L) on VF dynamics in Langendorff-perfused rabbit hearts. The left ventricular (LV) anterior wall was mapped and optical action potential duration restitution (APDR) was determined at 25 epicardial sites. We performed ablation during VF of the left anterior PM in hearts with (N=6) or without (N=6) cytochalasin infusion, the LV lateral epicardium (Epi group, N=3), and the LV endocardium (Endo group, N=3). The PM was also ablated in 3 hearts without propranolol (control group). Propranolol converted multiple-wavelet VF to slow VF with reentry localized to the PM. Propranolol decreased the maximal slope of the APDR curve (P<0.001) as well as its spatial heterogeneity (P<0.01) and conduction velocity (P=0.01) while increasing the VF cycle length (P<0.001). PM ablation terminated VF during propropranolol infusion with (6 of 6, 100%) or without (4 of 6, 67%) cytochalasin D and significantly reduced inducibility. VF did not terminate in the Epi, Endo, and control groups (P<0.001). CONCLUSIONS Propranolol flattens the APDR curve and reduces conduction velocity, converting multiple-wavelet VF into VF with a focal source anchored to the PM. Ablation of this focal source may terminate VF.
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Affiliation(s)
- Hui-Nam Pak
- Division of Cardiology, Department of Medicine, Cedars-Sinai Medical Center and David Geffen School of Medicine, University of California Los Angeles, Calif 90048, USA
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Pak HN, Liu YB, Hayashi H, Okuyama Y, Chen PS, Lin SF. Synchronization of ventricular fibrillation with real-time feedback pacing: implication to low-energy defibrillation. Am J Physiol Heart Circ Physiol 2003; 285:H2704-11. [PMID: 12893637 DOI: 10.1152/ajpheart.00366.2003] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Wavefront synchronization is an important aspect preceding the termination of ventricular fibrillation (VF). We evaluated the defibrillation efficacy of a novel multisite pacing algorithm using optical recording-guided synchronized pacing (SyncP) in the excitable gaps. We compared the effects of SyncP with traditional overdrive pacing (ODP) at 90% of the VF cycle length (VFCL) and high-frequency pacing (HFP; 43-215 Hz) on spontaneous VF termination in isolated rabbit hearts. For SyncP, the pacing current was triggered by the activation of a reference site and was delivered when the optical potential of the pacing site was in an excitable gap. We measured VFCL and the spatial dispersion of VFCL (SDCL) from five points (3 points in the paced area and 2 points in the nonpaced area) and the distribution of phase singularities during the prepacing, pacing, and postpacing periods. The results showed that 1) the VF termination rate of SyncP (16.0%, n = 106) was higher than that of ODP (2.1%, n = 48, P < 0.01) or HFP (1.6%, n = 129, P < 0.0001); 2) energy consumption for SyncP (7.6 +/- 9.3 mJ) was significantly lower than that of ODP (14.0 +/- 14.8 mJ, P < 0.0001); and 3) SyncP, but not ODP or HFP, decreased SDCL in the paced area during the pacing (P < 0.01) and postpacing (P < 0.05) periods compared with the prepacing period. We conclude that SyncP is effective in inducing wavefront synchronization and is more effective at facilitating spontaneous VF termination than non-SyncP.
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Affiliation(s)
- Hui-Nam Pak
- Department of Medicine, Cedars-Sinai Medical Center and David Geffen School of Medicine, University of California, Los Angeles, 90048, USA
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Kadish A, Johnson D, Choe W, Goldberger J, Horvath G. Characterization of fibrillatory rhythms by ensemble vector directional analysis. Am J Physiol Heart Circ Physiol 2003; 285:H1705-19. [PMID: 12791595 DOI: 10.1152/ajpheart.01108.2001] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Recent studies have demonstrated that fibrillatory rhythms are not random phenomena but have definable patterns. However, standard mapping techniques may have limitations in their ability to identify the organization of fibrillation. The purpose of this study was to develop and apply a method, "ensemble vector mapping," for characterizing the spatiotemporal organization of fibrillation. Ventricular fibrillation was induced by burst pacing in normal mongrel dogs. In a separate protocol, atrial fibrillation was induced by epicardial aconitine application. Epicardial electrograms were recorded from a 112-electrode plaque array using a computerized mapping system. Vectors were created by summing orthogonal bipolar electrograms. The magnitude of the vectors was transformed using a logarithmic function, integrated over time, and normalized for local electrogram amplitude to produce an "ensemble vector" index whose magnitude is high when beat-to-beat activation direction is consistent and low when activation direction is variable. The mean index was 137 +/- 36 mV/s during ventricular pacing at a cycle length of 300 ms but only 39 +/- 23 mV/s during ventricular fibrillation (P < 0.001). The ensemble vector index was also lower during atrial fibrillation (60 +/- 54 mV/s) than during atrial pacing (115 +/- 27 mV/s, P < 0.01 vs. atrial fibrillation) but not as low as during ventricular fibrillation (P < 0.05, atrial vs. ventricular fibrillation). The index was also capable of distinguishing atrial tachycardia from atrial fibrillation. Ensemble vector mapping produces an objective assessment of the consistency of myocardial activation during fibrillation. The consistency of activation direction differs in different models of fibrillation and is higher during atrial than ventricular fibrillation. This technique has the potential to rapidly characterize repetitive activation patterns in fibrillatory rhythms and may help distinguish among different characteristics of fibrillatory rhythms.
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Affiliation(s)
- Alan Kadish
- Feinberg Cardiovascular Research Institute and Department of Medicine, Northwestern University, Chicago, IL 60611, USA.
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Hayashi H, Miyauchi Y, Chou CC, Karagueuzian HS, Chen PS, Lin SF. Effects of Cytochalasin D on Electrical Restitution and the Dynamics of Ventricular Fibrillation in Isolated Rabbit Heart. J Cardiovasc Electrophysiol 2003; 14:1077-84. [PMID: 14521661 DOI: 10.1046/j.1540-8167.2003.03234.x] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
UNLABELLED Cytochalasin D in Rabbit Ventricle. INTRODUCTION Cytochalasin D (cyto-D) has been used as an excitation-contraction uncoupler during optical mapping studies. However, its effects on action potential duration restitution (APDR) and dynamics during ventricular fibrillation (VF) are unclear. METHODS AND RESULTS Langendorff-perfused rabbit hearts (N = 6) were immersed in a tissue chamber. Transmembrane potential was recorded using glass microelectrodes. APD measured to 90% repolarization (APD90) was used to construct the APDR curve. During regular pacing at 300-msec cycle length, increasing concentrations of cyto-D resulted in progressively prolonged APD90 (131 +/- 26 msec, 171 +/- 14 msec, and 177 +/- 14 msec) and steepened maximum slope of the APDR curve (1.1 +/- 0.2, 1.3 +/- 0.2, and 1.6 +/- 0.4 for control, 5 micromoles, and 10 micromoles, respectively; P < 0.01). Resting membrane potential, AP amplitude, and maximum dV/dt did not change. Cyto-D lengthened VF cycle length and APD90, and steepened the maximum slope of the APDR curve. However, cyto-D did not significantly change the diastolic interval. The dominant frequency of pseudoelectrocardiogram progressively decreased with increasing concentrations of cyto-D (15.2 +/- 0.6 Hz, 11.1 +/- 2.4 Hz, and 9.8 +/- 3.2 Hz for control, 5 micromoles, and 10 micromoles, respectively; P < 0.01). Sustained (>1 min) VF was repeatedly inducible at baseline and with 5 or 10 micromoles of cyto-D. CONCLUSION Continuous perfusion of cyto-D at 5 or 10 micromoles prolonged APD90, steepened APDR slope, and reduced dominant frequency in rabbit ventricles. Cyto-D at these concentrations allowed induction of sustained VF.
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Affiliation(s)
- Hideki Hayashi
- Division of Cardiology, Department of Medicine, Cedars-Sinai Medical Center, and David Geffen School of Medicine at UCLA, Los Angeles, California, USA
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Affiliation(s)
- Douglas P Zipes
- Krannert Institute of Cardiology, Indiana University School of Medicine and the Roudebush Veterans Administration Medical Center, Indianapolis, Indiana 46202, USA
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Abstract
BACKGROUND Multiple excitation wavelets are present during ventricular fibrillation (VF). The underlying wavelet organization of VF is unclear. Phase singularities (PSs)-locations of ambiguous activation state-underlie reentry and wavelet splitting and represent the sources of VF. Understanding the mechanisms of PS formation might be important in the development of effective therapies for sudden death. METHODS AND RESULTS We performed voltage, phase, and PS mapping in fibrillating ventricles, applying an automated PS detection algorithm to optically recorded fibrillation signals. PS clustering was noted along epicardial vessels, ridges of endocardial trabeculae, and papillary muscle insertions. Microscopically, these locations correlated with areas of apposition of fibers with different angulations and intramural vessels. A total of 83.2% of PSs were formed at and meandered about these anatomic structures, which acted as stabilizers: PSs colocalizing at anatomic substrates had longer life spans than nonanatomic PS (82.46+/-60.8 versus 40.5+/-31.9 ms, P<0.01). The RV endocardium had a higher PS incidence than the epicardium (42.3+/-9.2 versus 23.5+/-11.6 PS/s, P<0.01). Autocorrelation showed that irregular behavior was spatially restricted to anatomic heterogeneities compared with other areas, which had nearly periodic behaviors. Simple spatial PS distributions underlay complex and variable activation patterns attributable to variable PS behaviors, life spans, and inter-PS interactions. CONCLUSIONS PSs occur in a nonrandom spatial distribution and colocalize with normal anatomic heterogeneities. Varying PS behaviors and life spans but stable PS spatial distributions cause ever-changing activation patterns that characterize VF.
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Affiliation(s)
- Miguel Valderrábano
- Division of Cardiology, Department of Medicine, Cedars-Sinai Medical Center and David Geffen School of Medicine, University of California Los Angeles, Calif 90048, USA
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Qin H, Kay MW, Chattipakorn N, Redden DT, Ideker RE, Rogers JM. Effects of heart isolation, voltage-sensitive dye, and electromechanical uncoupling agents on ventricular fibrillation. Am J Physiol Heart Circ Physiol 2003; 284:H1818-26. [PMID: 12679330 DOI: 10.1152/ajpheart.00923.2002] [Citation(s) in RCA: 53] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
We tested whether the interventions typically required for optical mapping affect activation patterns during ventricular fibrillation (VF). A 21 x 24 unipolar electrode array (1.5 mm spacing) was sutured to the left ventricular epicardium of 16 anesthetized pigs, and four episodes of electrically induced VF (30-s duration) were recorded. The hearts were then rapidly excised and connected to a Langendorff perfusion apparatus. Four of the hearts were controls, in which 24 additional VF episodes were then mapped. In the remaining 12 hearts, four VF episodes were mapped after isolation, four more episodes were mapped after exposure to the voltage-sensitive dye di-4-ANEPPS, and six more episodes were mapped after exposure to the electromechanical uncoupling agents diacetyl monoxime (DAM; 20 mmol/l, n = 6) or cytochalasin D (CytoD; 10 micromol/l, n = 6). VF episodes were separated by 4 min. VF activation patterns were quantified using custom pattern analysis algorithms. From comparisons with time-corrected control data, all interventions significantly changed VF patterns. Most changes were broadly consistent with slowing and regularization due to loss of excitability. Heart isolation had the largest effect on VF patterns, followed by CytoD, DAM, and dye.
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Affiliation(s)
- Hao Qin
- Department of Physiology and Biophysics, University of Alabama, 1670 University Boulevard, Birmingham, AL 35294, USA
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