51
|
Shi S, Liu T, Wang D, Zhang Y, Liang J, Yang B, Hu D. Activation of N-methyl-d-aspartate receptors reduces heart rate variability and facilitates atrial fibrillation in rats. Europace 2017; 19:1237-1243. [PMID: 27170002 DOI: 10.1093/europace/euw086] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/26/2015] [Accepted: 03/09/2016] [Indexed: 11/15/2022] Open
Abstract
AIMS The goal of this study was to assess the effects of N-methyl-d-aspartate (NMDA) receptors activation on heart rate variability (HRV) and susceptibility to atrial fibrillation (AF). METHODS AND RESULTS Rats were randomized for treatment with saline, NMDA (agonist of NMDA receptors), or NMDA plus MK-801 (antagonist of NMDA receptors) for 2 weeks. Heart rate variability was evaluated by using implantable electrocardiogram telemeters. Atrial fibrillation susceptibility was assessed with programmed stimulation in isolated hearts. Compared with the controls, the NMDA-treated rats displayed a decrease in the standard deviation of normal RR intervals, the standard deviation of the average RR intervals, the mean of the 5-min standard deviations of RR intervals, the root mean square of successive differences, and high frequency (HF); and an increase in low frequency (LF) and LF/HF (all P< 0.01). Additionally, the NMDA-treated rats showed prolonged activation latency and reduced effective refractory period (all P< 0.01). Importantly, AF was induced in all NMDA-treated rats. While atrial fibrosis developed, connexin40 downgraded and metalloproteinase 9 upgraded in the NMDA-treated rats (all P< 0.01). Most of the above alterations were mitigated by co-administering with MK-801. CONCLUSION These results indicate that NMDA receptors activation reduces HRV and enhances AF inducibility, with cardiac autonomic imbalance, atrial fibrosis, and degradation of gap junction protein identified as potential mechanistic contributors.
Collapse
Affiliation(s)
- Shaobo Shi
- Department of Cardiology, Renmin Hospital of Wuhan University, 238 Jiefang Road, Wuchang District, Wuhan, Hubei 430060, China
- Cardiovascular Research Institute, Wuhan University, Wuhan, China
| | - Tao Liu
- Department of Cardiology, Renmin Hospital of Wuhan University, 238 Jiefang Road, Wuchang District, Wuhan, Hubei 430060, China
- Cardiovascular Research Institute, Wuhan University, Wuhan, China
- Montreal Heart Institute, University of Montreal, Montreal, QC, Canada
| | - Dandan Wang
- Department of Cardiology, Renmin Hospital of Wuhan University, 238 Jiefang Road, Wuchang District, Wuhan, Hubei 430060, China
- Cardiovascular Research Institute, Wuhan University, Wuhan, China
| | - Yan Zhang
- Department of Cardiology, Renmin Hospital of Wuhan University, 238 Jiefang Road, Wuchang District, Wuhan, Hubei 430060, China
- Cardiovascular Research Institute, Wuhan University, Wuhan, China
| | - Jinjun Liang
- Department of Cardiology, Renmin Hospital of Wuhan University, 238 Jiefang Road, Wuchang District, Wuhan, Hubei 430060, China
- Cardiovascular Research Institute, Wuhan University, Wuhan, China
| | - Bo Yang
- Department of Cardiology, Renmin Hospital of Wuhan University, 238 Jiefang Road, Wuchang District, Wuhan, Hubei 430060, China
- Cardiovascular Research Institute, Wuhan University, Wuhan, China
| | - Dan Hu
- Department of Cardiology, Renmin Hospital of Wuhan University, 238 Jiefang Road, Wuchang District, Wuhan, Hubei 430060, China
- Cardiovascular Research Institute, Wuhan University, Wuhan, China
- Masonic Medical Research Laboratory, 2150 Bleecker Street, Utica, NY 13501, USA
| |
Collapse
|
52
|
Inhibition of potassium currents is involved in antiarrhythmic effect of moderate ethanol on atrial fibrillation. Toxicol Appl Pharmacol 2017; 322:89-96. [DOI: 10.1016/j.taap.2017.03.006] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/22/2016] [Revised: 03/01/2017] [Accepted: 03/07/2017] [Indexed: 12/27/2022]
|
53
|
Zaman JAB, Baykaner T, Schricker AA, Krummen DE, Narayan SM. Mechanistic targets for the ablation of atrial fibrillation. Glob Cardiol Sci Pract 2017; 2017:e201707. [PMID: 28971106 PMCID: PMC5621726 DOI: 10.21542/gcsp.2017.7] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/03/2022] Open
Abstract
The mechanisms responsible for sustaining atrial fibrillation are a key debate in cardiovascular pathophysiology, and directly influence the approach to therapy including ablation Clinical and basic studies have split AF mechanisms into two basic camps: ‘spatially distributed disorganization’ and ‘localized sources’. Recent data suggest that these mechanisms can also be separated by the method for mapping – with nearly all traditional electrogram analyses showing spatially distributed disorganization and nearly all optical mapping studies showing localized sources We will review this dichotomy in light of these recently identified differences in mapping, and in the context of recent clinical studies in which localized ablation has been shown to impact AF, also lending support to the localized source hypothesis. We will conclude with other concepts on mechanism-based ablation and areas of ongoing research that must be addressed to continue improving our knowledge and treatment of AF.
Collapse
Affiliation(s)
- Junaid A B Zaman
- Stanford University, Palo Alto, California.,Imperial College, University of London, United Kingdom
| | - Tina Baykaner
- Stanford University, Palo Alto, California.,University of California, San Diego, California
| | | | | | | |
Collapse
|
54
|
Kunamalla A, Ng J, Parini V, Yoo S, McGee KA, Tomson TT, Gordon D, Thorp EB, Lomasney J, Zhang Q, Shah S, Browne S, Knight BP, Passman R, Goldberger JJ, Aistrup G, Arora R. Constitutive Expression of a Dominant-Negative TGF-β Type II Receptor in the Posterior Left Atrium Leads to Beneficial Remodeling of Atrial Fibrillation Substrate. Circ Res 2016; 119:69-82. [PMID: 27217399 DOI: 10.1161/circresaha.115.307878] [Citation(s) in RCA: 37] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/22/2015] [Accepted: 05/23/2016] [Indexed: 11/16/2022]
Abstract
RATIONALE Fibrosis is an important structural contributor to formation of atrial fibrillation (AF) substrate in heart failure. Transforming growth factor-β (TGF-β) signaling is thought to be intricately involved in creation of atrial fibrosis. OBJECTIVE We hypothesized that gene-based expression of dominant-negative type II TGF-β receptor (TGF-β-RII-DN) in the posterior left atrium in a canine heart failure model will sufficiently attenuate fibrosis-induced changes in atrial conduction and restitution to decrease AF. Because AF electrograms are thought to reflect AF substrate, we further hypothesized that TGF-β-RII-DN would lead to increased fractionation and decreased organization of AF electrograms. METHODS AND RESULTS Twenty-one dogs underwent injection+electroporation in the posterior left atrium of plasmid expressing a dominant-negative TGF-β type II receptor (pUBc-TGFβ-DN-RII; n=9) or control vector (pUBc-LacZ; n=12), followed by 3 to 4 weeks of right ventricular tachypacing (240 bpm). Compared with controls, dogs treated with pUBC-TGFβ-DN-RII demonstrated an attenuated increase in conduction inhomogeneity, flattening of restitution slope and decreased duration of induced AF, with AF electrograms being more fractionated and less organized in pUBc-TGFβ-DN-RII versus pUBc-LacZ dogs. Tissue analysis revealed a significant decrease in replacement/interstitial fibrosis, p-SMAD2/3 and p-ERK1/2. CONCLUSIONS Targeted gene-based reduction of TGF-β signaling in the posterior left atrium-with resulting decrease in replacement fibrosis-led to beneficial remodeling of both conduction and restitution characteristics of the posterior left atrium, translating into a decrease in AF and increased complexity of AF electrograms. In addition to providing mechanistic insights, this data may have important diagnostic and therapeutic implications for AF.
Collapse
Affiliation(s)
- Aaron Kunamalla
- From the Feinberg Cardiovascular Research Institute, Northwestern University, Feinberg School of Medicine, Chicago, IL
| | - Jason Ng
- From the Feinberg Cardiovascular Research Institute, Northwestern University, Feinberg School of Medicine, Chicago, IL
| | - Vamsi Parini
- From the Feinberg Cardiovascular Research Institute, Northwestern University, Feinberg School of Medicine, Chicago, IL
| | - Shin Yoo
- From the Feinberg Cardiovascular Research Institute, Northwestern University, Feinberg School of Medicine, Chicago, IL
| | - Kate A McGee
- From the Feinberg Cardiovascular Research Institute, Northwestern University, Feinberg School of Medicine, Chicago, IL
| | - Todd T Tomson
- From the Feinberg Cardiovascular Research Institute, Northwestern University, Feinberg School of Medicine, Chicago, IL
| | - David Gordon
- From the Feinberg Cardiovascular Research Institute, Northwestern University, Feinberg School of Medicine, Chicago, IL
| | - Edward B Thorp
- From the Feinberg Cardiovascular Research Institute, Northwestern University, Feinberg School of Medicine, Chicago, IL
| | - Jon Lomasney
- From the Feinberg Cardiovascular Research Institute, Northwestern University, Feinberg School of Medicine, Chicago, IL
| | - Qiang Zhang
- From the Feinberg Cardiovascular Research Institute, Northwestern University, Feinberg School of Medicine, Chicago, IL
| | - Sanjiv Shah
- From the Feinberg Cardiovascular Research Institute, Northwestern University, Feinberg School of Medicine, Chicago, IL
| | - Suzanne Browne
- From the Feinberg Cardiovascular Research Institute, Northwestern University, Feinberg School of Medicine, Chicago, IL
| | - Bradley P Knight
- From the Feinberg Cardiovascular Research Institute, Northwestern University, Feinberg School of Medicine, Chicago, IL
| | - Rod Passman
- From the Feinberg Cardiovascular Research Institute, Northwestern University, Feinberg School of Medicine, Chicago, IL
| | - Jeffrey J Goldberger
- From the Feinberg Cardiovascular Research Institute, Northwestern University, Feinberg School of Medicine, Chicago, IL
| | - Gary Aistrup
- From the Feinberg Cardiovascular Research Institute, Northwestern University, Feinberg School of Medicine, Chicago, IL
| | - Rishi Arora
- From the Feinberg Cardiovascular Research Institute, Northwestern University, Feinberg School of Medicine, Chicago, IL.
| |
Collapse
|
55
|
Nattel S. How does fibrosis promote atrial fibrillation persistence: in silico findings, clinical observations, and experimental data. Cardiovasc Res 2016; 110:295-7. [PMID: 27131507 DOI: 10.1093/cvr/cvw092] [Citation(s) in RCA: 33] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Affiliation(s)
- Stanley Nattel
- Department of Medicine and Research Center, Montreal Heart Institute and Université de Montréal, 5000 Belanger Street E, Montreal, QC, Canada H1T 1C8 Department of Pharmacology and Therapeutics, McGill University Montreal, Montreal, Canada Institute of Pharmacology, West German Heart and Vascular Center, Faculty of Medicine, University Duisburg-Essen, Essen, Germany
| |
Collapse
|
56
|
Krummen DE, Ho G, Villongco CT, Hayase J, Schricker AA. Ventricular fibrillation: triggers, mechanisms and therapies. Future Cardiol 2016; 12:373-90. [PMID: 27120223 DOI: 10.2217/fca-2016-0001] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/20/2023] Open
Abstract
Ventricular fibrillation (VF) is a common, life-threatening arrhythmia responsible for significant morbidity and mortality. Due to challenges in safely mapping VF, a comprehensive understanding of its mechanisms remains elusive. Recent findings have provided new insights into mechanisms that sustain early VF. Notably, the central role of electrical rotors and catheter-based ablation of VF rotor substrate have been recently reported. In this article, we will review data regarding four stages of VF: initiation, transition, maintenance and evolution. We will discuss the particular mechanisms for each stage and therapies targeting these mechanisms. We also examine inherited arrhythmia syndromes, including the mechanisms and therapies specific to each. We hope that the overview of VF outlined in this work will assist other investigators in designing future therapies to interrupt this life-threatening arrhythmia.
Collapse
Affiliation(s)
- David E Krummen
- Department of Medicine, University of California San Diego, 9500 Gilman Drive, La Jolla, CA 92093, USA.,Department of Medicine, VA San Diego Healthcare System, 3350 La Jolla Village Drive, San Diego, CA 92161, USA
| | - Gordon Ho
- Department of Medicine, University of California San Diego, 9500 Gilman Drive, La Jolla, CA 92093, USA.,Department of Medicine, VA San Diego Healthcare System, 3350 La Jolla Village Drive, San Diego, CA 92161, USA
| | - Christopher T Villongco
- Department of Bioengineering, University of California San Diego, 9500 Gilman Drive, La Jolla, CA 92093, USA
| | - Justin Hayase
- Department of Medicine, University of California San Diego, 9500 Gilman Drive, La Jolla, CA 92093, USA.,Department of Medicine, VA San Diego Healthcare System, 3350 La Jolla Village Drive, San Diego, CA 92161, USA
| | - Amir A Schricker
- Department of Medicine, University of California San Diego, 9500 Gilman Drive, La Jolla, CA 92093, USA.,Department of Medicine, VA San Diego Healthcare System, 3350 La Jolla Village Drive, San Diego, CA 92161, USA
| |
Collapse
|
57
|
Zahid S, Whyte KN, Schwarz EL, Blake RC, Boyle PM, Chrispin J, Prakosa A, Ipek EG, Pashakhanloo F, Halperin HR, Calkins H, Berger RD, Nazarian S, Trayanova NA. Feasibility of using patient-specific models and the "minimum cut" algorithm to predict optimal ablation targets for left atrial flutter. Heart Rhythm 2016; 13:1687-98. [PMID: 27108938 DOI: 10.1016/j.hrthm.2016.04.009] [Citation(s) in RCA: 67] [Impact Index Per Article: 8.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/18/2015] [Indexed: 11/19/2022]
Abstract
BACKGROUND Left atrial flutter (LAFL) occurs in patients after atrial fibrillation ablation. Identification of optimal ablation targets to terminate LAFL remains challenging. OBJECTIVE The purpose of this study was to use patient-specific models to simulate LAFL and predict optimal ablation targets using a novel approach based on flow network theory. METHODS Late gadolinium-enhanced cardiac magnetic resonance scans from 10 patients with LAFL were used to construct atrial models incorporating fibrosis by investigators blinded to procedural findings. Rapid pacing was applied in silico to induce LAFL. In each LAFL, we represented reentrant wave propagation as an electric flow network and identified the "minimum cut" (MC), which was the smallest amount of tissue that separated the flow into 2 discontinuous components. In silico ablation was applied at MCs, and targets were compared to those that terminated LAFL during catheter ablation. RESULTS Patient-specific atrial models were successfully generated from patient scans. LAFL was induced in 7 of 10 models. Ablation of MCs terminated LAFL in 4 models and produced new, slower LAFL morphologies in the other 3. For the latter cases, flow analysis was repeated to identify MCs of emergent LAFLs. Ablation of these MCs terminated emergent LAFLs. The MC-based ablation lesions in simulations were similar in length and location to ablation targets that terminated LAFL during catheter ablation for these 7 patients. CONCLUSION Personalized atrial simulations can predict ablation targets for LAFL. These simulations provide a powerful tool for planning ablation procedures and may reduce procedural times and complications.
Collapse
Affiliation(s)
- Sohail Zahid
- Institute for Computational Medicine, Department of Biomedical Engineering, Johns Hopkins University, Baltimore, Maryland
| | - Kaitlyn N Whyte
- Institute for Computational Medicine, Department of Biomedical Engineering, Johns Hopkins University, Baltimore, Maryland
| | - Erica L Schwarz
- Institute for Computational Medicine, Department of Biomedical Engineering, Johns Hopkins University, Baltimore, Maryland
| | - Robert C Blake
- CardioSolv Ablation Technologies Inc, Baltimore, Maryland
| | - Patrick M Boyle
- Institute for Computational Medicine, Department of Biomedical Engineering, Johns Hopkins University, Baltimore, Maryland
| | - Jonathan Chrispin
- Department of Medicine, Johns Hopkins University School of Medicine, Baltimore, Maryland
| | - Adityo Prakosa
- Institute for Computational Medicine, Department of Biomedical Engineering, Johns Hopkins University, Baltimore, Maryland
| | - Esra G Ipek
- Department of Medicine, Johns Hopkins University School of Medicine, Baltimore, Maryland
| | - Farhad Pashakhanloo
- Institute for Computational Medicine, Department of Biomedical Engineering, Johns Hopkins University, Baltimore, Maryland
| | - Henry R Halperin
- Department of Medicine, Johns Hopkins University School of Medicine, Baltimore, Maryland
| | - Hugh Calkins
- Department of Medicine, Johns Hopkins University School of Medicine, Baltimore, Maryland
| | - Ronald D Berger
- Department of Medicine, Johns Hopkins University School of Medicine, Baltimore, Maryland
| | - Saman Nazarian
- Department of Medicine, Johns Hopkins University School of Medicine, Baltimore, Maryland; Department of Epidemiology, Johns Hopkins University School of Medicine, Baltimore, Maryland
| | - Natalia A Trayanova
- Institute for Computational Medicine, Department of Biomedical Engineering, Johns Hopkins University, Baltimore, Maryland; Department of Medicine, Johns Hopkins University School of Medicine, Baltimore, Maryland.
| |
Collapse
|
58
|
Bayer JD, Roney CH, Pashaei A, Jaïs P, Vigmond EJ. Novel Radiofrequency Ablation Strategies for Terminating Atrial Fibrillation in the Left Atrium: A Simulation Study. Front Physiol 2016; 7:108. [PMID: 27148061 PMCID: PMC4828663 DOI: 10.3389/fphys.2016.00108] [Citation(s) in RCA: 46] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2015] [Accepted: 03/07/2016] [Indexed: 12/19/2022] Open
Abstract
Pulmonary vein isolation (PVI) with radiofrequency ablation (RFA) is the cornerstone of atrial fibrillation (AF) therapy, but few strategies exist for when it fails. To guide RFA, phase singularity (PS) mapping locates reentrant electrical waves (rotors) that perpetuate AF. The goal of this study was to test existing and develop new RFA strategies for terminating rotors identified with PS mapping. It is unsafe to test experimental RFA strategies in patients, so they were evaluated in silico using a bilayer computer model of the human atria with persistent AF (pAF) electrical (ionic) and structural (fibrosis) remodeling. pAF was initiated by rapidly pacing the right (RSPV) and left (LSPV) superior pulmonary veins during sinus rhythm, and rotor dynamics quantified by PS analysis. Three RFA strategies were studied: (i) PVI, roof, and mitral lines; (ii) circles, perforated circles, lines, and crosses 0.5-1.5 cm in diameter/length administered near rotor locations/pathways identified by PS mapping; and (iii) 4-8 lines streamlining the sequence of electrical activation during sinus rhythm. As in pAF patients, 2 ± 1 rotors with cycle length 185 ± 4 ms and short PS duration 452 ± 401 ms perpetuated simulated pAF. Spatially, PS density had weak to moderate positive correlations with fibrosis density (RSPV: r = 0.38, p = 0.35, LSPV: r = 0.77, p = 0.02). RFA PVI, mitral, and roof lines failed to terminate pAF, but RFA perforated circles and lines 1.5 cm in diameter/length terminated meandering rotors from RSPV pacing when placed at locations with high PS density. Similarly, RFA circles, perforated circles, and crosses 1.5 cm in diameter/length terminated stationary rotors from LSPV pacing. The most effective strategy for terminating pAF was to streamline the sequence of activation during sinus rhythm with >4 RFA lines. These results demonstrate that co-localizing 1.5 cm RFA lesions with locations of high PS density is a promising strategy for terminating pAF rotors. For patients immune to PVI, roof, mitral, and PS guided RFA strategies, streamlining patient-specific activation sequences during sinus rhythm is a robust but challenging alternative.
Collapse
Affiliation(s)
- Jason D Bayer
- Electrophysiology and Heart Modeling Institute (LIRYC), Bordeaux University FoundationPessac, France; Cardiothoracic Research Center of Bordeaux (Inserm U 1045), University of BordeauxBordeaux, France
| | - Caroline H Roney
- Electrophysiology and Heart Modeling Institute (LIRYC), Bordeaux University FoundationPessac, France; Institute of Mathematics of Bordeaux (IMB), University of BordeauxTalence, France
| | - Ali Pashaei
- Electrophysiology and Heart Modeling Institute (LIRYC), Bordeaux University FoundationPessac, France; Institute of Mathematics of Bordeaux (IMB), University of BordeauxTalence, France
| | - Pierre Jaïs
- Electrophysiology and Heart Modeling Institute (LIRYC), Bordeaux University FoundationPessac, France; Cardiothoracic Research Center of Bordeaux (Inserm U 1045), University of BordeauxBordeaux, France; Haut-Lévêque Cardiology Hospital, University Hospital Center (CHU) of BordeauxPessac, France
| | - Edward J Vigmond
- Electrophysiology and Heart Modeling Institute (LIRYC), Bordeaux University FoundationPessac, France; Institute of Mathematics of Bordeaux (IMB), University of BordeauxTalence, France
| |
Collapse
|
59
|
Zahid S, Cochet H, Boyle PM, Schwarz EL, Whyte KN, Vigmond EJ, Dubois R, Hocini M, Haïssaguerre M, Jaïs P, Trayanova NA. Patient-derived models link re-entrant driver localization in atrial fibrillation to fibrosis spatial pattern. Cardiovasc Res 2016; 110:443-54. [PMID: 27056895 DOI: 10.1093/cvr/cvw073] [Citation(s) in RCA: 200] [Impact Index Per Article: 25.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/19/2015] [Accepted: 03/31/2016] [Indexed: 12/19/2022] Open
Abstract
AIMS The mechanisms underlying persistent atrial fibrillation (AF) in patients with atrial fibrosis are poorly understood. The goal of this study was to use patient-derived atrial models to test the hypothesis that AF re-entrant drivers (RDs) persist only in regions with specific fibrosis patterns. METHODS AND RESULTS Twenty patients with persistent AF (PsAF) underwent late gadolinium-enhanced MRI to detect the presence of atrial fibrosis. Segmented images were used to construct personalized 3D models of the fibrotic atria with biophysically realistic atrial electrophysiology. In each model, rapid pacing was applied to induce AF. AF dynamics were analysed and RDs were identified using phase mapping. Fibrosis patterns in RD regions were characterized by computing maps of fibrosis density (FD) and entropy (FE). AF was inducible in 13/20 models and perpetuated by few RDs (2.7 ± 1.5) that were spatially confined (trajectory of phase singularities: 7.6 ± 2.3 mm). Compared with the remaining atrial tissue, regions where RDs persisted had higher FE (IQR: 0.42-0.60 vs. 0.00-0.40, P < 0.05) and FD (IQR: 0.59-0.77 vs. 0.00-0.33, P < 0.05). Machine learning classified RD and non-RD regions based on FD and FE and identified a subset of fibrotic boundary zones present in 13.8 ± 4.9% of atrial tissue where 83.5 ± 2.4% of all RD phase singularities were located. CONCLUSION Patient-derived models demonstrate that AF in fibrotic substrates is perpetuated by RDs persisting in fibrosis boundary zones characterized by specific regional fibrosis metrics (high FE and FD). These results provide new insights into the mechanisms that sustain PsAF and could pave the way for personalized, MRI-based management of PsAF.
Collapse
Affiliation(s)
- Sohail Zahid
- Institute for Computational Medicine, Department of Biomedical Engineering, Johns Hopkins University, Baltimore, MD, USA
| | - Hubert Cochet
- IHU LIRYC, Electrophysiology and Heart Modeling Institute, INSERM U1045, Bordeaux, France Hôpital Cardiologique du Haut-Lévêque, CHU Bordeaux, Université de Bordeaux, Bordeaux, France
| | - Patrick M Boyle
- Institute for Computational Medicine, Department of Biomedical Engineering, Johns Hopkins University, Baltimore, MD, USA
| | - Erica L Schwarz
- Institute for Computational Medicine, Department of Biomedical Engineering, Johns Hopkins University, Baltimore, MD, USA
| | - Kaitlyn N Whyte
- Institute for Computational Medicine, Department of Biomedical Engineering, Johns Hopkins University, Baltimore, MD, USA
| | - Edward J Vigmond
- IHU LIRYC, Electrophysiology and Heart Modeling Institute, INSERM U1045, Bordeaux, France
| | - Rémi Dubois
- IHU LIRYC, Electrophysiology and Heart Modeling Institute, INSERM U1045, Bordeaux, France
| | - Mélèze Hocini
- IHU LIRYC, Electrophysiology and Heart Modeling Institute, INSERM U1045, Bordeaux, France Hôpital Cardiologique du Haut-Lévêque, CHU Bordeaux, Université de Bordeaux, Bordeaux, France
| | - Michel Haïssaguerre
- IHU LIRYC, Electrophysiology and Heart Modeling Institute, INSERM U1045, Bordeaux, France Hôpital Cardiologique du Haut-Lévêque, CHU Bordeaux, Université de Bordeaux, Bordeaux, France
| | - Pierre Jaïs
- IHU LIRYC, Electrophysiology and Heart Modeling Institute, INSERM U1045, Bordeaux, France Hôpital Cardiologique du Haut-Lévêque, CHU Bordeaux, Université de Bordeaux, Bordeaux, France
| | - Natalia A Trayanova
- Institute for Computational Medicine, Department of Biomedical Engineering, Johns Hopkins University, Baltimore, MD, USA Department of Medicine, Johns Hopkins University School of Medicine, Baltimore, MD, USA
| |
Collapse
|
60
|
Vigmond E, Pashaei A, Amraoui S, Cochet H, Hassaguerre M. Percolation as a mechanism to explain atrial fractionated electrograms and reentry in a fibrosis model based on imaging data. Heart Rhythm 2016; 13:1536-43. [PMID: 26976038 DOI: 10.1016/j.hrthm.2016.03.019] [Citation(s) in RCA: 70] [Impact Index Per Article: 8.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/05/2015] [Indexed: 11/17/2022]
Abstract
BACKGROUND Complex fractionated atrial electrograms (CFAEs) have long been associated with proarrhythmic alterations in atrial structure or electrophysiology. Structural alterations disrupt and slow smoothly propagating wavefronts, leading to wavebreaks and electrogram (EGM) fractionation, but the exact nature and characteristics for arrhythmia remain unknown. Clinically, in atrial fibrillation (AF) patients, increases in frequency, whether by pacing or fibrillation, increase EGM fractionation and duration, and reentry can occur in relation with the conduction disturbance. Recently, percolation has been proposed as an arrhythmogenic mechanism, but its role in AF has not been investigated. OBJECTIVE We sought to determine if percolation can explain reentry formation and EGM behavior observed in AF patients. METHODS Computer models of fibrotic tissue with different densities were generated based on late gadolinium-enhanced magnetic resonance images, using pixel intensity as a fibrosis probability to avoid an arbitrary binary threshold. Clinical pacing protocols were followed to induce AF, and EGMs were computed. RESULTS Reentry could be elicited, with a biphasic behavior dependent on fibrotic density. CFAEs were recorded above fibrotic regions, and consistent with clinical data, EGM duration and fractionation increased with more rapid pacing. CONCLUSION These findings confirm percolation as a potential mechanism to explain AF in humans and give new insights into dynamics underlying conduction distortions and fractionated signals in excitable media, which correlate well with the experimental findings in fibrotic regions. The greater understanding of the different patterns of conduction changes and related EGMs could lead to more individualized and effective approaches to AF ablation therapy.
Collapse
Affiliation(s)
- Edward Vigmond
- L'Institut de Rythmologie et Modélisation Cardiaque LIRYC, Fondation Université de Bordeaux, Hôpital Xavier-Arnozan, Pessac, France; Institut de Mathématiques de Bordeaux, Université de Bordeaux, Talence, France.
| | - Ali Pashaei
- L'Institut de Rythmologie et Modélisation Cardiaque LIRYC, Fondation Université de Bordeaux, Hôpital Xavier-Arnozan, Pessac, France; Institut de Mathématiques de Bordeaux, Université de Bordeaux, Talence, France
| | - Sana Amraoui
- L'Institut de Rythmologie et Modélisation Cardiaque LIRYC, Fondation Université de Bordeaux, Hôpital Xavier-Arnozan, Pessac, France; Hôpital cardiologique de Haut- Lévèque, Pessac, France
| | - Hubert Cochet
- L'Institut de Rythmologie et Modélisation Cardiaque LIRYC, Fondation Université de Bordeaux, Hôpital Xavier-Arnozan, Pessac, France; Centre de Recherche Cardio-Thoracique de Bordeaux U1045,Université de Bordeaux, Bordeaux, France; Hôpital cardiologique de Haut- Lévèque, Pessac, France
| | - Michel Hassaguerre
- L'Institut de Rythmologie et Modélisation Cardiaque LIRYC, Fondation Université de Bordeaux, Hôpital Xavier-Arnozan, Pessac, France; Centre de Recherche Cardio-Thoracique de Bordeaux U1045,Université de Bordeaux, Bordeaux, France; Hôpital cardiologique de Haut- Lévèque, Pessac, France
| |
Collapse
|
61
|
Jacquemet V. Lessons from computer simulations of ablation of atrial fibrillation. J Physiol 2016; 594:2417-30. [PMID: 26846178 DOI: 10.1113/jp271660] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/02/2015] [Accepted: 01/28/2016] [Indexed: 11/08/2022] Open
Abstract
This paper reviews the simulations of catheter ablation in computer models of the atria, from the first attempts to the most recent anatomical models. It describes how postulated substrates of atrial fibrillation can be incorporated into mathematical models, how modelling studies can be designed to test ablation strategies, what their current trade-offs and limitations are, and what clinically relevant lessons can be learnt from these simulations. Drawing a parallel between clinical and modelling studies, six ablation targets are considered: pulmonary vein isolation, linear ablation, ectopic foci, complex fractionated atrial electrogram, rotors and ganglionated plexi. The examples presented for each ablation target illustrate a major advantage of computer models, the ability to identify why a therapy is successful or not in a given atrial fibrillation substrate. The integration of pathophysiological data to create detailed models of arrhythmogenic substrates is expected to solidify the understanding of ablation mechanisms and to provide theoretical arguments supporting substrate-specific ablation strategies.
Collapse
Affiliation(s)
- Vincent Jacquemet
- Department of Molecular and Integrative Physiology, Faculty of Medicine, Université de Montréal, Montréal, QC, Canada.,Centre de Recherche, Hôpital du Sacré-Cœur, Montréal, QC, Canada
| |
Collapse
|
62
|
Krogh-Madsen T, Sobie EA, Christini DJ. Improving cardiomyocyte model fidelity and utility via dynamic electrophysiology protocols and optimization algorithms. J Physiol 2016; 594:2525-36. [PMID: 26661516 DOI: 10.1113/jp270618] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/09/2015] [Accepted: 09/30/2015] [Indexed: 12/15/2022] Open
Abstract
Mathematical models of cardiac electrophysiology are instrumental in determining mechanisms of cardiac arrhythmias. However, the foundation of a realistic multiscale heart model is only as strong as the underlying cell model. While there have been myriad advances in the improvement of cellular-level models, the identification of model parameters, such as ion channel conductances and rate constants, remains a challenging problem. The primary limitations to this process include: (1) such parameters are usually estimated from data recorded using standard electrophysiology voltage-clamp protocols that have not been developed with model building in mind, and (2) model parameters are typically tuned manually to subjectively match a desired output. Over the last decade, methods aimed at overcoming these disadvantages have emerged. These approaches include the use of optimization or fitting tools for parameter estimation and incorporating more extensive data for output matching. Here, we review recent advances in parameter estimation for cardiomyocyte models, focusing on the use of more complex electrophysiology protocols and global search heuristics. We also discuss future applications of such parameter identification, including development of cell-specific and patient-specific mathematical models to investigate arrhythmia mechanisms and predict therapy strategies.
Collapse
Affiliation(s)
- Trine Krogh-Madsen
- Greenberg Division of Cardiology, Weill Cornell Medical College, New York, NY, USA.,Institute for Computational Biomedicine, Weill Cornell Medical College, New York, NY, USA
| | - Eric A Sobie
- Pharmacology and Systems Therapeutics, Mount Sinai School of Medicine, New York, NY, USA
| | - David J Christini
- Greenberg Division of Cardiology, Weill Cornell Medical College, New York, NY, USA.,Institute for Computational Biomedicine, Weill Cornell Medical College, New York, NY, USA.,Department of Physiology and Biophysics, Weill Cornell Medical College, New York, NY, USA
| |
Collapse
|
63
|
Narayan SM, Zaman JAB. Mechanistically based mapping of human cardiac fibrillation. J Physiol 2016; 594:2399-415. [PMID: 26607671 PMCID: PMC4850202 DOI: 10.1113/jp270513] [Citation(s) in RCA: 33] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/23/2015] [Accepted: 11/20/2015] [Indexed: 12/02/2022] Open
Abstract
The mechanisms underpinning human cardiac fibrillation remain elusive. In his 1913 paper ‘On dynamic equilibrium in the heart’, Mines proposed that an activation wave front could propagate repeatedly in a circle, initiated by a stimulus in the vulnerable period. While the dynamics of activation and recovery are central to cardiac fibrillation, these physiological data are rarely used in clinical mapping. Fibrillation is a rapid irregular rhythm with spatiotemporal disorder resulting from two fundamental mechanisms – sources in preferred cardiac regions or spatially diffuse self‐sustaining activity, i.e. with no preferred source. On close inspection, however, this debate may also reflect mapping technique. Fibrillation is initiated from triggers by regional dispersion in repolarization, slow conduction and wavebreak, then sustained by non‐uniform interactions of these mechanisms. Notably, optical mapping of action potentials in atrial fibrillation (AF) show spiral wave sources (rotors) in nearly all studies including humans, while most traditional electrogram analyses of AF do not. Techniques may diverge in fibrillation because electrograms summate non‐coherent waves within an undefined field whereas optical maps define waves with a visually defined field. Also fibrillation operates at the limits of activation and recovery, which are well represented by action potentials while fibrillatory electrograms poorly represent repolarization. We conclude by suggesting areas for study that may be used, until such time as optical mapping is clinically feasible, to improve mechanistic understanding and therapy of human cardiac fibrillation.
![]()
Collapse
Affiliation(s)
| | - Junaid A B Zaman
- Stanford University, Palo Alto, CA, USA.,Imperial College London, London, UK
| |
Collapse
|
64
|
Trayanova NA, Chang KC. How computer simulations of the human heart can improve anti-arrhythmia therapy. J Physiol 2016; 594:2483-502. [PMID: 26621489 DOI: 10.1113/jp270532] [Citation(s) in RCA: 35] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/01/2015] [Accepted: 11/25/2015] [Indexed: 01/26/2023] Open
Abstract
Over the last decade, the state-of-the-art in cardiac computational modelling has progressed rapidly. The electrophysiological function of the heart can now be simulated with a high degree of detail and accuracy, opening the doors for simulation-guided approaches to anti-arrhythmic drug development and patient-specific therapeutic interventions. In this review, we outline the basic methodology for cardiac modelling, which has been developed and validated over decades of research. In addition, we present several recent examples of how computational models of the human heart have been used to address current clinical problems in cardiac electrophysiology. We will explore the use of simulations to improve anti-arrhythmic pacing and defibrillation interventions; to predict optimal sites for clinical ablation procedures; and to aid in the understanding and selection of arrhythmia risk markers. Together, these studies illustrate how the tremendous advances in cardiac modelling are poised to revolutionize medical treatment and prevention of arrhythmia.
Collapse
Affiliation(s)
- Natalia A Trayanova
- Johns Hopkins School of Medicine, Baltimore, MD, 21205, USA.,Johns Hopkins University, Baltimore, MD, 21218, USA
| | - Kelly C Chang
- Johns Hopkins School of Medicine, Baltimore, MD, 21205, USA
| |
Collapse
|
65
|
Karathanos TV, Boyle PM, Trayanova NA. Optogenetics-enabled dynamic modulation of action potential duration in atrial tissue: feasibility of a novel therapeutic approach. Europace 2015; 16 Suppl 4:iv69-iv76. [PMID: 25362173 DOI: 10.1093/europace/euu250] [Citation(s) in RCA: 32] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
AIMS Diseases that abbreviate the cardiac action potential (AP) by increasing the strength of repolarizing transmembrane currents are highly arrhythmogenic. It has been proposed that optogenetic tools could be used to restore normal AP duration (APD) in the heart under such disease conditions. This study aims to evaluate the efficacy of an optogenetic treatment modality for prolonging pathologically shortened APs in a detailed computational model of short QT syndrome (SQTS) in the human atria, and compare it to drug treatment. METHODS AND RESULTS We used a human atrial myocyte model with faster repolarization caused by SQTS; light sensitivity was inscribed via the presence of channelrhodopsin-2 (ChR2). We conducted simulations in single cells and in a magnetic resonance imaging-based model of the human left atrium (LA). Application of an appropriate optical stimulus to a diseased cell dynamically increased APD, producing an excellent match to control AP (<1.5 mV deviation); treatment of a diseased cell with an AP-prolonging drug (chloroquine) also increased APD, but the match to control AP was worse (>5 mV deviation). Under idealized conditions in the LA (uniform ChR2-expressing cell distribution, no light attenuation), optogenetics-based therapy outperformed chloroquine treatment (APD increased to 87% and 81% of control). However, when non-uniform ChR2-expressing cell distribution and light attenuation were incorporated, optogenetics-based treatment was less effective (APD only increased to 55%). CONCLUSION This study demonstrates proof of concept for optogenetics-based treatment of diseases that alter atrial AP shape. We identified key practical obstacles intrinsic to the optogenetic approach that must be overcome before such treatments can be realized.
Collapse
Affiliation(s)
- Thomas V Karathanos
- Department of Biomedical Engineering, Institute for Computational Medicine and Johns Hopkins University, 3400 N. Charles St., Hackerman Hall Room 316, Baltimore, MD 21218, USA
| | - Patrick M Boyle
- Department of Biomedical Engineering, Institute for Computational Medicine and Johns Hopkins University, 3400 N. Charles St., Hackerman Hall Room 316, Baltimore, MD 21218, USA
| | - Natalia A Trayanova
- Department of Biomedical Engineering, Institute for Computational Medicine and Johns Hopkins University, 3400 N. Charles St., Hackerman Hall Room 316, Baltimore, MD 21218, USA
| |
Collapse
|
66
|
Pashaei A, Bayer J, Meillet V, Dubois R, Vigmond E. Computation and projection of spiral wave trajectories during atrial fibrillation: a computational study. Card Electrophysiol Clin 2015; 7:37-47. [PMID: 25784021 DOI: 10.1016/j.ccep.2014.11.001] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/24/2022]
Abstract
To show how atrial fibrillation rotor activity on the heart surface manifests as phase on the torso, fibrillation was induced on a geometrically accurate computer model of the human atria. The Hilbert transform, time embedding, and filament detection were compared. Electrical activity on the epicardium was used to compute potentials on different surfaces from the atria to the torso. The Hilbert transform produces erroneous phase when pacing for longer than the action potential duration. The number of phase singularities, frequency content, and the dominant frequency decreased with distance from the heart, except for the convex hull.
Collapse
Affiliation(s)
- Ali Pashaei
- LIRYC Electrophysiology and Heart Modelling Institute, University of Bordeaux, PTIB-Campus Xavier, Arnozan, Avenue du Haut Lévèque, Bordeaux 33600, France; Inserm U1045, Cardiothoracic Research Center, 146 rue Léo-Saignat, Bordeaux Cedex 33076, France.
| | - Jason Bayer
- LIRYC Electrophysiology and Heart Modelling Institute, University of Bordeaux, PTIB-Campus Xavier, Arnozan, Avenue du Haut Lévèque, Bordeaux 33600, France; Inserm U1045, Cardiothoracic Research Center, 146 rue Léo-Saignat, Bordeaux Cedex 33076, France
| | - Valentin Meillet
- LIRYC Electrophysiology and Heart Modelling Institute, University of Bordeaux, PTIB-Campus Xavier, Arnozan, Avenue du Haut Lévèque, Bordeaux 33600, France; Inserm U1045, Cardiothoracic Research Center, 146 rue Léo-Saignat, Bordeaux Cedex 33076, France
| | - Rémi Dubois
- LIRYC Electrophysiology and Heart Modelling Institute, University of Bordeaux, PTIB-Campus Xavier, Arnozan, Avenue du Haut Lévèque, Bordeaux 33600, France; Inserm U1045, Cardiothoracic Research Center, 146 rue Léo-Saignat, Bordeaux Cedex 33076, France
| | - Edward Vigmond
- LIRYC Electrophysiology and Heart Modelling Institute, University of Bordeaux, PTIB-Campus Xavier, Arnozan, Avenue du Haut Lévèque, Bordeaux 33600, France; Bordeaux Institute of Mathematics UMR 5251, University of Bordeaux, 351 cours de la Libération, Talence 33405, France
| |
Collapse
|
67
|
Krummen DE, Hebsur S, Salcedo J, Narayan SM, Lalani GG, Schricker AA. Mechanisms Underlying AF: Triggers, Rotors, Other? CURRENT TREATMENT OPTIONS IN CARDIOVASCULAR MEDICINE 2015; 17:371. [PMID: 25778423 DOI: 10.1007/s11936-015-0371-4] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 10/23/2022]
Abstract
OPINION STATEMENT There is ongoing debate regarding the precise mechanisms underlying atrial fibrillation (AF). An improved understanding of these mechanisms is urgently needed to improve interventional strategies to suppress and eliminate AF, since the success of current strategies is suboptimal. At present, guidelines for AF ablation focus on pulmonary vein (PV) isolation for the prevention of arrhythmia. Additional targets are presently unclear, and include additional linear ablation and electrogram-guided substrate modification, without clear mechanistic relevance. PV and non-PV triggers are likely central in the first few seconds of AF initiation. Rapid activation from such triggers interacts with transitional mechanisms including conduction velocity slowing, action potential duration (APD) alternans, and steep APD restitution to cause conduction block and initiate functional reentry. However, complete suppression of potential triggers has proven elusive, and the intra-procedural mapping and targeting of transitional mechanisms has not been reported. A growing body of research implicates electrical rotors and focal sources as central mechanisms for the maintenance of AF. In several recent series, they were observed in nearly all patients with sustained arrhythmia. Ablation of rotor and focal source sites, prior to pulmonary vein isolation, substantially modulated atrial fibrillation in a high proportion of patients, and improved ablation outcomes versus pulmonary vein isolation alone. These results have subsequently been confirmed in multicenter series, and the improved outcomes have been found to persist to a mean follow-up of 3 years. Recently, rotors have been observed by multiple groups using diverse technologies. These findings represent a paradigm shift in AF, focusing on sustaining mechanisms, as is currently done with other arrhythmias such as atrioventricular node reentrant tachycardia. Studies are currently underway to assess the optimal strategy for the application of rotor-based ablation in AF management, including clinical trials on the relative efficacy of rotor-only ablation versus PVI-only ablation, which will inform future practice guidelines.
Collapse
Affiliation(s)
- David E Krummen
- University of California San Diego and VA San Diego Healthcare System, 3350 La Jolla Village Drive, Cardiology Section 111A, San Diego, CA, 92161, USA,
| | | | | | | | | | | |
Collapse
|
68
|
Krummen DE, Swarup V, Narayan SM. The role of rotors in atrial fibrillation. J Thorac Dis 2015; 7:142-51. [PMID: 25713729 DOI: 10.3978/j.issn.2072-1439.2014.11.15] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/01/2014] [Accepted: 10/23/2014] [Indexed: 11/14/2022]
Abstract
Despite significant advances in our understanding of atrial fibrillation (AF) mechanisms in the last 15 years, ablation outcomes remain suboptimal. A potential reason is that many ablation techniques focus on anatomic, rather than patient-specific functional targets for ablation. Panoramic contact mapping, incorporating phase analysis, repolarization and conduction dynamics, and oscillations in AF rate, overcomes many prior difficulties with mapping AF. This approach provides evidence that the mechanisms sustaining human AF are deterministic, largely due to stable electrical rotors and focal sources in either atrium. Ablation of such sources (Focal Impulse and Rotor Modulation: FIRM ablation) has been shown to improve ablation outcome compared with conventional ablation alone; independent laboratories directly targeting stable rotors have shown similar results. Clinical trials examining the role of stand-alone FIRM ablation are in progress. Looking forward, translating insights from patient-specific mapping to evidence-based guidelines and clinical practice is the next challenge in improving patient outcomes in AF management.
Collapse
Affiliation(s)
- David E Krummen
- 1 Department of Medicine/Cardiology, University of California San Diego Medical Center, San Diego, CA and VA San Diego Healthcare System, San Diego, CA 92161, USA ; 2 Arizona Heart Hospital, Phoenix, AZ, USA ; 3 Stanford University, Palo Alto, CA, USA
| | - Vijay Swarup
- 1 Department of Medicine/Cardiology, University of California San Diego Medical Center, San Diego, CA and VA San Diego Healthcare System, San Diego, CA 92161, USA ; 2 Arizona Heart Hospital, Phoenix, AZ, USA ; 3 Stanford University, Palo Alto, CA, USA
| | - Sanjiv M Narayan
- 1 Department of Medicine/Cardiology, University of California San Diego Medical Center, San Diego, CA and VA San Diego Healthcare System, San Diego, CA 92161, USA ; 2 Arizona Heart Hospital, Phoenix, AZ, USA ; 3 Stanford University, Palo Alto, CA, USA
| |
Collapse
|
69
|
McDowell KS, Zahid S, Vadakkumpadan F, Blauer J, MacLeod RS, Trayanova NA. Virtual electrophysiological study of atrial fibrillation in fibrotic remodeling. PLoS One 2015; 10:e0117110. [PMID: 25692857 PMCID: PMC4333565 DOI: 10.1371/journal.pone.0117110] [Citation(s) in RCA: 95] [Impact Index Per Article: 10.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/16/2014] [Accepted: 12/18/2014] [Indexed: 12/19/2022] Open
Abstract
Research has indicated that atrial fibrillation (AF) ablation failure is related to the presence of atrial fibrosis. However it remains unclear whether this information can be successfully used in predicting the optimal ablation targets for AF termination. We aimed to provide a proof-of-concept that patient-specific virtual electrophysiological study that combines i) atrial structure and fibrosis distribution from clinical MRI and ii) modeling of atrial electrophysiology, could be used to predict: (1) how fibrosis distribution determines the locations from which paced beats degrade into AF; (2) the dynamic behavior of persistent AF rotors; and (3) the optimal ablation targets in each patient. Four MRI-based patient-specific models of fibrotic left atria were generated, ranging in fibrosis amount. Virtual electrophysiological studies were performed in these models, and where AF was inducible, the dynamics of AF were used to determine the ablation locations that render AF non-inducible. In 2 of the 4 models patient-specific models AF was induced; in these models the distance between a given pacing location and the closest fibrotic region determined whether AF was inducible from that particular location, with only the mid-range distances resulting in arrhythmia. Phase singularities of persistent rotors were found to move within restricted regions of tissue, which were independent of the pacing location from which AF was induced. Electrophysiological sensitivity analysis demonstrated that these regions changed little with variations in electrophysiological parameters. Patient-specific distribution of fibrosis was thus found to be a critical component of AF initiation and maintenance. When the restricted regions encompassing the meander of the persistent phase singularities were modeled as ablation lesions, AF could no longer be induced. The study demonstrates that a patient-specific modeling approach to identify non-invasively AF ablation targets prior to the clinical procedure is feasible.
Collapse
Affiliation(s)
- Kathleen S. McDowell
- The Johns Hopkins University, Department of Biomedical Engineering, Baltimore, Maryland, United States of America
| | - Sohail Zahid
- The Johns Hopkins University, Department of Biomedical Engineering, Baltimore, Maryland, United States of America
| | - Fijoy Vadakkumpadan
- The Johns Hopkins University, Department of Biomedical Engineering, Baltimore, Maryland, United States of America
| | - Joshua Blauer
- University of Utah, Comprehensive Arrhythmia Research and Management Center, School of Medicine, Salt Lake City, Utah, United States of America
| | - Rob S. MacLeod
- University of Utah, Comprehensive Arrhythmia Research and Management Center, School of Medicine, Salt Lake City, Utah, United States of America
| | - Natalia A. Trayanova
- The Johns Hopkins University, Department of Biomedical Engineering, Baltimore, Maryland, United States of America
- * E-mail:
| |
Collapse
|
70
|
Chang KC, Bayer JD, Trayanova NA. Disrupted calcium release as a mechanism for atrial alternans associated with human atrial fibrillation. PLoS Comput Biol 2014; 10:e1004011. [PMID: 25501557 PMCID: PMC4263367 DOI: 10.1371/journal.pcbi.1004011] [Citation(s) in RCA: 35] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/27/2014] [Accepted: 10/29/2014] [Indexed: 12/19/2022] Open
Abstract
Atrial fibrillation (AF) is the most common cardiac arrhythmia, but our knowledge of the arrhythmogenic substrate is incomplete. Alternans, the beat-to-beat alternation in the shape of cardiac electrical signals, typically occurs at fast heart rates and leads to arrhythmia. However, atrial alternans have been observed at slower pacing rates in AF patients than in controls, suggesting that increased vulnerability to arrhythmia in AF patients may be due to the proarrythmic influence of alternans at these slower rates. As such, alternans may present a useful therapeutic target for the treatment and prevention of AF, but the mechanism underlying alternans occurrence in AF patients at heart rates near rest is unknown. The goal of this study was to determine how cellular changes that occur in human AF affect the appearance of alternans at heart rates near rest. To achieve this, we developed a computational model of human atrial tissue incorporating electrophysiological remodeling associated with chronic AF (cAF) and performed parameter sensitivity analysis of ionic model parameters to determine which cellular changes led to alternans. Of the 20 parameters tested, only decreasing the ryanodine receptor (RyR) inactivation rate constant (kiCa) produced action potential duration (APD) alternans seen clinically at slower pacing rates. Using single-cell clamps of voltage, fluxes, and state variables, we determined that alternans onset was Ca2+-driven rather than voltage-driven and occurred as a result of decreased RyR inactivation which led to increased steepness of the sarcoplasmic reticulum (SR) Ca2+ release slope. Iterated map analysis revealed that because SR Ca2+ uptake efficiency was much higher in control atrial cells than in cAF cells, drastic reductions in kiCa were required to produce alternans at comparable pacing rates in control atrial cells. These findings suggest that RyR kinetics may play a critical role in altered Ca2+ homeostasis which drives proarrhythmic APD alternans in patients with AF. Atrial fibrillation is an irregular heart rhythm affecting millions of people worldwide. Effective treatment of this cardiac disorder relies upon our detailed knowledge and understanding of the mechanisms that lead to arrhythmia. Recent clinical observations have suggested that alternans, a phenomenon where the shape of the electrical signal in the heart alternates from beat to beat, may play an important role in this process, but the underlying mechanisms remain unknown. In this study, we use computational models to conduct a detailed examination of the causes and contributors to alternans associated with human atrial fibrillation. We find that in atria remodeled by atrial fibrillation, alternans appears near resting heart rates because several aspects of calcium cycling are disrupted in the atrial cells. In particular, the release and uptake of calcium from the cellular storage compartment, the sarcoplasmic reticulum, becomes imbalanced, leading to alternation in calcium signals from beat to beat. These findings provide important insights into the mechanisms of proarrhythmic alternans in human atrial fibrillation which may be used to develop novel therapeutic targets and treatment strategies in the future.
Collapse
Affiliation(s)
- Kelly C. Chang
- Institute for Computational Medicine, Department of Biomedical Engineering, Johns Hopkins University, Baltimore, Maryland, United States of America
| | - Jason D. Bayer
- IHU-LIRYC - L'Institut de RYthmologie et Modélisation Cardiaque, University of Bordeaux, Bordeaux, France
| | - Natalia A. Trayanova
- Institute for Computational Medicine, Department of Biomedical Engineering, Johns Hopkins University, Baltimore, Maryland, United States of America
- * E-mail:
| |
Collapse
|
71
|
Xie Y, Grandi E, Bers DM, Sato D. How does β-adrenergic signalling affect the transitions from ventricular tachycardia to ventricular fibrillation? Europace 2014; 16:452-7. [PMID: 24569900 DOI: 10.1093/europace/eut412] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023] Open
Abstract
AIMS Ventricular tachycardia (VT) and fibrillation (VF) are the most lethal cardiac arrhythmias. The degeneration of VT into VF is associated with the breakup of a spiral wave of the action potential in cardiac tissue. β-Adrenergic (βAR) signalling potentiates the L-type Ca current (ICaL) faster than the slow delayed rectifier potassium current (IKs), which transiently prolongs the action potential duration (APD) and promotes early after depolarizations. In this study, we aimed at investigating how βAR signalling affects the transition from VT to VF. METHODS AND RESULTS We used a physiologically detailed computer model of the rabbit ventricular myocyte in a two-dimensional tissue to determine how spiral waves respond to βAR activation following administration of isoproterenol. A simplified mathematical model was also used to investigate the underlying dynamics. We found that the spatiotemporal behaviour of spiral waves strongly depends on the kinetics of βAR activation. When βAR activation is rapid, a stable spiral wave turns into small fragments and its electrocardiogram reveals the transition from VT to VF. This is due to the transiently steepened APD restitution induced by the faster activation of ICaL vs. IKs upon sudden βAR activation. The spiral wave may also disappear if its transient wavelength is too large to be supported by the tissue size upon sudden strong βAR activation that prolongs APD transiently. When βAR activation is gradual, a stable spiral wave remains such, because of more limited increase in both APD and slope of APD restitution due to more contemporaneous ICaL and IKs activation. CONCLUSION Changes in APD restitution during βAR activation revealed a novel transient spiral wave dynamics; this spatiotemporal characteristic strongly depends on the protocol of isoproterenol application.
Collapse
Affiliation(s)
- Yuanfang Xie
- Department of Pharmacology, University of California Davis, 451 Health Sciences Drive, GBSF Room 3502, Davis, CA 95616-8636, USA
| | | | | | | |
Collapse
|
72
|
Nishida K, Datino T, Macle L, Nattel S. Atrial Fibrillation Ablation. J Am Coll Cardiol 2014; 64:823-31. [DOI: 10.1016/j.jacc.2014.06.1172] [Citation(s) in RCA: 59] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/27/2014] [Revised: 06/26/2014] [Accepted: 06/27/2014] [Indexed: 10/24/2022]
|
73
|
Abstract
Atrial fibrillation (AF) is the most common arrhythmia targeted by catheter ablation. Despite significant advances in our understanding of AF, ablation outcomes remain suboptimal, and this is due in large part to an incomplete understanding of the underlying sustaining mechanisms of AF. Recent developments of patient-tailored and physiology-based computational mapping systems have identified localized electrical spiral waves, or rotors, and focal sources as mechanisms that may represent novel targets for therapy. This report provides an overview of Focal Impulse and Rotor Modulation (FIRM) mapping, which reveals that human AF is often not actually driven by disorganized activity but instead that disorganization is secondary to organized rotors or focal sources. Targeted ablation of such sources alone can eliminate AF and, when added to pulmonary vein isolation, improves long-term outcome compared with conventional ablation alone. Translating mechanistic insights from such patient-tailored mapping is likely to be crucial in achieving the next major advances in personalized medicine for AF.
Collapse
Affiliation(s)
- Amir A. Schricker
- Department of Medicine/Cardiology, University of California San Diego Medical Center, San Diego, CA 92161, USA
| | - Gautam G. Lalani
- Department of Medicine/Cardiology, University of California San Diego Medical Center, San Diego, CA 92161, USA
| | - David E. Krummen
- Department of Medicine/Cardiology, University of California San Diego Medical Center, San Diego, CA 92161, USA
| | - Sanjiv M. Narayan
- Department of Medicine/Cardiology, University of California San Diego Medical Center, San Diego, CA 92161, USA
| |
Collapse
|
74
|
Trayanova NA. Mathematical approaches to understanding and imaging atrial fibrillation: significance for mechanisms and management. Circ Res 2014; 114:1516-31. [PMID: 24763468 DOI: 10.1161/circresaha.114.302240] [Citation(s) in RCA: 74] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
Atrial fibrillation (AF) is the most common sustained arrhythmia in humans. The mechanisms that govern AF initiation and persistence are highly complex, of dynamic nature, and involve interactions across multiple temporal and spatial scales in the atria. This article aims to review the mathematical modeling and computer simulation approaches to understanding AF mechanisms and aiding in its management. Various atrial modeling approaches are presented, with descriptions of the methodological basis and advancements in both lower-dimensional and realistic geometry models. A review of the most significant mechanistic insights made by atrial simulations is provided. The article showcases the contributions that atrial modeling and simulation have made not only to our understanding of the pathophysiology of atrial arrhythmias, but also to the development of AF management approaches. A summary of the future developments envisioned for the field of atrial simulation and modeling is also presented. The review contends that computational models of the atria assembled with data from clinical imaging modalities that incorporate electrophysiological and structural remodeling could become a first line of screening for new AF therapies and approaches, new diagnostic developments, and new methods for arrhythmia prevention.
Collapse
Affiliation(s)
- Natalia A Trayanova
- From the Department of Biomedical Engineering and Institute for Computational Medicine, Johns Hopkins University, Baltimore, MD
| |
Collapse
|
75
|
Faggioni M, Savio-Galimberti E, Venkataraman R, Hwang HS, Kannankeril PJ, Darbar D, Knollmann BC. Suppression of spontaneous ca elevations prevents atrial fibrillation in calsequestrin 2-null hearts. Circ Arrhythm Electrophysiol 2014; 7:313-20. [PMID: 24493699 DOI: 10.1161/circep.113.000994] [Citation(s) in RCA: 46] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
BACKGROUND Atrial fibrillation (AF) risk has been associated with leaky ryanodine receptor 2 (RyR2) Ca release channels. Patients with mutations in RyR2 or in the sarcoplasmic reticulum Ca-binding protein calsequestrin 2 (Casq2) display an increased risk for AF. Here, we examine the underlying mechanisms of AF associated with loss of Casq2 and test mechanism-based drug therapy. METHODS AND RESULTS Compared with wild-type Casq2+/+ mice, atrial burst pacing consistently induced atrial flutter or AF in Casq2-/- mice and in isolated Casq2-/- hearts. Atrial optical voltage maps obtained from isolated hearts revealed multiple independent activation sites arising predominantly from the pulmonary vein region. Ca and voltage mapping demonstrated diastolic subthreshold spontaneous Ca elevations (SCaEs) and delayed afterdepolarizations whenever the pacing train failed to induce AF. The dual RyR2 and Na channel inhibitor R-propafenone (3 μmol/L) significantly reduced frequency and amplitude of SCaEs and delayed afterdepolarizations in atrial myocytes and intact atria and prevented induction of AF. In contrast, the S-enantiomer of propafenone, an equipotent Na channel blocker but much weaker RyR2 inhibitor, did not reduce SCaEs and delayed afterdepolarizations and failed to prevent AF. CONCLUSIONS Loss of Casq2 increases risk of AF by promoting regional SCaEs and delayed afterdepolarizations in atrial tissue, which can be prevented by RyR2 inhibition with R-propafenone. Targeting AF caused by leaky RyR2 Ca channels with R-propafenone may be a more mechanism-based approach to treating this common arrhythmia.
Collapse
Affiliation(s)
- Michela Faggioni
- Division of Clinical Pharmacology, Department of Medicine, Division of Cardiology, Department of Medicine, Department of Biomedical Engineering and Physics, and Division of Cardiology, Department of Pediatrics, Vanderbilt University, Nashville, TN; and Department of Cardiovascular Diseases, University of Pisa, Pisa, Italy
| | | | | | | | | | | | | |
Collapse
|
76
|
McDowell KS, Vadakkumpadan F, Blake R, Blauer J, Plank G, Macleod RS, Trayanova NA. Mechanistic inquiry into the role of tissue remodeling in fibrotic lesions in human atrial fibrillation. Biophys J 2014; 104:2764-73. [PMID: 23790385 DOI: 10.1016/j.bpj.2013.05.025] [Citation(s) in RCA: 98] [Impact Index Per Article: 9.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/08/2013] [Revised: 04/23/2013] [Accepted: 05/10/2013] [Indexed: 01/23/2023] Open
Abstract
Atrial fibrillation (AF), the most common arrhythmia in humans, is initiated when triggered activity from the pulmonary veins propagates into atrial tissue and degrades into reentrant activity. Although experimental and clinical findings show a correlation between atrial fibrosis and AF, the causal relationship between the two remains elusive. This study used an array of 3D computational models with different representations of fibrosis based on a patient-specific atrial geometry with accurate fibrotic distribution to determine the mechanisms by which fibrosis underlies the degradation of a pulmonary vein ectopic beat into AF. Fibrotic lesions in models were represented with combinations of: gap junction remodeling; collagen deposition; and myofibroblast proliferation with electrotonic or paracrine effects on neighboring myocytes. The study found that the occurrence of gap junction remodeling and the subsequent conduction slowing in the fibrotic lesions was a necessary but not sufficient condition for AF development, whereas myofibroblast proliferation and the subsequent electrophysiological effect on neighboring myocytes within the fibrotic lesions was the sufficient condition necessary for reentry formation. Collagen did not alter the arrhythmogenic outcome resulting from the other fibrosis components. Reentrant circuits formed throughout the noncontiguous fibrotic lesions, without anchoring to a specific fibrotic lesion.
Collapse
Affiliation(s)
- Kathleen S McDowell
- The Johns Hopkins University, Department of Biomedical Engineering and Institute for Computational Medicine, Baltimore, Maryland, USA
| | | | | | | | | | | | | |
Collapse
|
77
|
Finlay MC, Xu L, Taggart P, Hanson B, Lambiase PD. Bridging the gap between computation and clinical biology: validation of cable theory in humans. Front Physiol 2013; 4:213. [PMID: 24027527 PMCID: PMC3761165 DOI: 10.3389/fphys.2013.00213] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/13/2013] [Accepted: 07/25/2013] [Indexed: 11/13/2022] Open
Abstract
Introduction: Computerized simulations of cardiac activity have significantly contributed to our understanding of cardiac electrophysiology, but techniques of simulations based on patient-acquired data remain in their infancy. We sought to integrate data acquired from human electrophysiological studies into patient-specific models, and validated this approach by testing whether electrophysiological responses to sequential premature stimuli could be predicted in a quantitatively accurate manner. Methods: Eleven patients with structurally normal hearts underwent electrophysiological studies. Semi-automated analysis was used to reconstruct activation and repolarization dynamics for each electrode. This S2 extrastimuli data was used to inform individualized models of cardiac conduction, including a novel derivation of conduction velocity restitution. Activation dynamics of multiple premature extrastimuli were then predicted from this model and compared against measured patient data as well as data derived from the ten-Tusscher cell-ionic model. Results: Activation dynamics following a premature S3 were significantly different from those after an S2. Patient specific models demonstrated accurate prediction of the S3 activation wave, (Pearson's R2 = 0.90, median error 4%). Examination of the modeled conduction dynamics allowed inferences into the spatial dispersion of activation delay. Further validation was performed against data from the ten-Tusscher cell-ionic model, with our model accurately recapitulating predictions of repolarization times (R2 = 0.99). Conclusions: Simulations based on clinically acquired data can be used to successfully predict complex activation patterns following sequential extrastimuli. Such modeling techniques may be useful as a method of incorporation of clinical data into predictive models.
Collapse
Affiliation(s)
- Malcolm C Finlay
- Department of Cardiac Electrophysiology, The Heart Hospital, Institute of Cardiovascular Science, University College London London, UK
| | | | | | | | | |
Collapse
|
78
|
Lalani GG, Schricker AA, Clopton P, Krummen DE, Narayan SM. Frequency analysis of atrial action potential alternans: a sensitive clinical index of individual propensity to atrial fibrillation. Circ Arrhythm Electrophysiol 2013; 6:859-67. [PMID: 23995250 DOI: 10.1161/circep.113.000204] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
BACKGROUND Few clinical indices identify the propensity of patients to atrial fibrillation (AF) when not in AF. Repolarization alternans has been shown to indicate AF vulnerability, but is limited in its sensitivity to detect changes in action potential (AP) duration (APD), which may be subtle. We hypothesized that spectral analysis would be a more sensitive and robust marker of AP alternans and thus a better clinical index of individual propensity to AF than APD alternans. METHODS AND RESULTS In 31 patients (12 persistent AF, 15 paroxysmal AF, 4 controls with no AF), we recorded left (n=27) and right (n=6) atrial monophasic APs during incremental pacing from cycle length 500 ms (120 beats per minute) to AF onset. Alternans was measured by APD and spectral analysis. At baseline pacing (median cycle length [1st, 3rd quartiles], 500 ms [500, 500]), APD alternans was detected in only 7 of 27 AF patients (no controls), whereas spectral AP alternans was detected in 18 of 27 AF patients (no controls; P=0.003); AP alternans was more prevalent in persistent than paroxysmal AF, and absent in controls (P=0.018 APD; P=0.042 spectral). Spectral AP alternans magnitude at baseline was highest in persistent AF, with modest rate-dependent amplification, followed by paroxysmal AF, with marked rate dependence, and undetectable in controls until just before induced AF. CONCLUSIONS Spectral AP alternans near baseline rates can identify patients with, versus those without, clinical histories and pathophysiological substrates for AF. Future studies should examine whether the presence of spectral AP alternans during sinus rhythm may obviate the need to actually demonstrate AF, such as on ambulatory ECG monitoring.
Collapse
Affiliation(s)
- Gautam G Lalani
- University of California-San Diego and Veterans Affairs Medical Center, San Diego, CA
| | | | | | | | | |
Collapse
|
79
|
Smaill BH, Zhao J, Trew ML. Three-dimensional impulse propagation in myocardium: arrhythmogenic mechanisms at the tissue level. Circ Res 2013; 112:834-48. [PMID: 23449546 DOI: 10.1161/circresaha.111.300157] [Citation(s) in RCA: 47] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Impulse propagation in the heart depends on the excitability of individual cardiomyocytes, impulse transmission between adjacent myocytes, and the 3-dimensional arrangement of those cells. Here, we review the role of each of these factors in normal and aberrant cardiac electric activation, with particular emphasis on the effects of 3-dimensional myocyte architecture at the tissue scale. The analysis draws on findings from in vivo and in vitro experiments, as well as biophysically based computer models that have been used to integrate and interpret these experimental data. It indicates that discontinuous arrangement of myocytes and extracellular connective tissue at the tissue scale can give rise to current source-to-sink mismatch, spatiotemporal distribution of refractoriness, and rate-sensitive electric instability, which contribute to the initiation and maintenance of reentrant cardiac arrhythmia. This exacerbates the risk of rhythm disturbance associated with heart disease. We conclude that structure-based, multiscale computer models that incorporate accurate information about local cellular electric activity provide a powerful platform for investigating the basis of reentrant cardiac arrhythmia. However, it is important that these models capture key features of structure and related electric function at the tissue scale.
Collapse
Affiliation(s)
- Bruce H Smaill
- Auckland Bioengineering Institute, University of Auckland, Auckland Mail Centre, Auckland 1142, New Zealand.
| | | | | |
Collapse
|