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Li W. Biomechanics of infarcted left Ventricle-A review of experiments. J Mech Behav Biomed Mater 2020; 103:103591. [PMID: 32090920 DOI: 10.1016/j.jmbbm.2019.103591] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/02/2019] [Revised: 12/06/2019] [Accepted: 12/09/2019] [Indexed: 01/14/2023]
Abstract
Myocardial infarction (MI) is one of leading diseases to contribute to annual death rate of 5% in the world. In the past decades, significant work has been devoted to this subject. Biomechanics of infarcted left ventricle (LV) is associated with MI diagnosis, understanding of remodelling, MI micro-structure and biomechanical property characterizations as well as MI therapy design and optimization, but the subject has not been reviewed presently. In the article, biomechanics of infarcted LV was reviewed in terms of experiments achieved in the subject so far. The concerned content includes experimental remodelling, kinematics and kinetics of infarcted LVs. A few important issues were discussed and several essential topics that need to be investigated further were summarized. Microstructure of MI tissue should be observed even carefully and compared between different methods for producing MI scar in the same animal model, and eventually correlated to passive biomechanical property by establishing innovative constitutive laws. More uniaxial or biaxial tensile tests are desirable on MI, border and remote tissues, and viscoelastic property identification should be performed in various time scales. Active contraction experiments on LV wall with MI should be conducted to clarify impaired LV pumping function and supply necessary data to the function modelling. Pressure-volume curves of LV with MI during diastole and systole for the human are also desirable to propose and validate constitutive laws for LV walls with MI.
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Affiliation(s)
- Wenguang Li
- School of Engineering, University of Glasgow, Glasgow, G12 8QQ, UK.
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2
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Bax JJ, Delgado V, Sogaard P, Singh JP, Abraham WT, Borer JS, Dickstein K, Gras D, Brugada J, Robertson M, Ford I, Krum H, Holzmeister J, Ruschitzka F, Gorcsan J. Prognostic implications of left ventricular global longitudinal strain in heart failure patients with narrow QRS complex treated with cardiac resynchronization therapy: a subanalysis of the randomized EchoCRT trial. Eur Heart J 2018; 38:720-726. [PMID: 28426885 DOI: 10.1093/eurheartj/ehw506] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/15/2016] [Accepted: 09/29/2016] [Indexed: 11/13/2022] Open
Abstract
Aim Left ventricular (LV) global longitudinal strain (GLS) reflects LV systolic function and correlates inversely with the extent of LV myocardial scar and fibrosis. The present subanalysis of the Echocardiography Guided CRT trial investigated the prognostic value of LV GLS in patients with narrow QRS complex. Methods and results Left ventricular (LV) global longitudinal strain (GLS) was measured on the apical 2-, 4- and 3-chamber views using speckle tracking analysis. Measurement of baseline LV GLS was feasible in 755 patients (374 with cardiac resynchronization therapy (CRT)-ON and 381 with CRT-OFF). The median value of LV GLS in the overall population was 7.9%, interquartile range 6.2-10.1%. After a mean follow-up period of 19.4 months, 95 patients in the CRT-OFF group and 111 in the CRT-ON group reached the combined primary endpoint of all-cause mortality and heart failure hospitalization. Each 1% absolute unit decrease in LV GLS was independently associated with 11% increase in the risk to reach the primary endpoint (Hazard ratio 1.11; 95% confidence interval 95% 1.04-1.17, P < 0.001), after adjusting for ischaemic cardiomyopathy and randomization treatment among other clinically relevant variables. When categorizing patients according to quartiles of LV GLS, the primary endpoint occurred more frequently in patients in the lowest quartile (<6.2%) treated with CRT-ON vs. CRT-OFF (45.6% vs. 28.7%, P = 0.009) whereas, no differences were observed in patients with LV GLS ≥6.2% treated with CRT-OFF vs. CRT-ON (23.7% vs. 24.5%, respectively; P = 0.62). Conclusion Low LV GLS is associated with poor outcome in heart failure patients with QRS width <130 ms, independent of randomization to CRT or not. Importantly, in the group of patients with the lowest LV GLS quartile, CRT may have a detrimental effect on clinical outcomes.
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Affiliation(s)
- Jeroen J Bax
- Department of Cardiology, Leiden University Medical Center, Albinusdreef 2, 2300 RC Leiden, The Netherlands
| | - Victoria Delgado
- Department of Cardiology, Leiden University Medical Center, Albinusdreef 2, 2300 RC Leiden, The Netherlands
| | - Peter Sogaard
- Aalborg University, Fredrik Bajers Vej 7-D3, Aalborg 9220, Denmark
| | - Jagmeet P Singh
- Cardiac Arrhythmia Service, Massachusetts General Hospital, Harvard Medical School, Corrigan Minehan Heart Center, 55 Fruit Street, Boston, MA 02114, USA
| | - William T Abraham
- The Division of Cardiovascular Medicine, Ohio State University Medical Center, Davis Heart and Lung Research Institute, 473 West 12th Avenue, Room 110P, Columbus, OH 43210-1252, USA
| | - Jeffrey S Borer
- The Division of Cardiovascular Medicine and Howard Gilman and Ron and Jean Schiavone Institutes, State University of New York Downstate College of Medicine, 450 Clarkson Avenue, Division of Cardiovascular Medicine, Sixth Floor, Brooklyn, NY, New York, USA
| | - Kenneth Dickstein
- University of Bergen, Stavanger University Hospital, Postboks 8600 Forus, 4036 Stavanger, Norway
| | - Daniel Gras
- Nouvelles Cliniques Nantaises, 2 - 4 Rue Eric Tabarly, 44200 Nantes, France
| | - Josep Brugada
- Cardiology Department, Thorax Institute, Hospital Clinic, University of Barcelona, Villarroel 170, 08036 Barcelona, Spain
| | - Michele Robertson
- Robertson Centre for Biostatistics, University of Glasgow, Glasgow, UK
| | - Ian Ford
- Robertson Centre for Biostatistics, University of Glasgow, Glasgow, UK
| | - Henry Krum
- Monash Centre of Cardiovascular Research and Education in Therapeutics, Monash University, Victoria 3800, Australia
| | - Johannes Holzmeister
- Clinic for Cardiology, University Hospital Zurich, Moussonstrasse 4, CH 8091 Zürich, Switzerland
| | - Frank Ruschitzka
- Clinic for Cardiology, University Hospital Zurich, Moussonstrasse 4, CH 8091 Zürich, Switzerland
| | - John Gorcsan
- The University of Pittsburgh, 4200 Fifth Ave, Pittsburgh, PA 15260, USA
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Institution of localized high-frequency electrical stimulation targeting early myocardial infarction: Effects on left ventricle function and geometry. J Thorac Cardiovasc Surg 2018; 156:568-575. [PMID: 29609885 DOI: 10.1016/j.jtcvs.2018.01.104] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/03/2017] [Revised: 12/20/2017] [Accepted: 01/13/2018] [Indexed: 11/21/2022]
Abstract
BACKGROUND Although strategies have focused on myocardial salvage/regeneration in the context of an acute coronary syndrome and a myocardial infarction (MI), interventions targeting the formed MI region and altering the course of the post-MI remodeling process have not been as well studied. This study tested the hypothesis that localized high-frequency stimulation instituted within a formed MI region using low-amplitude electrical pulses would favorably change the trajectory of changes in left ventricle geometry and function. METHODS At 7 days following MI induction, pigs were randomized for localized high-frequency stimulation (n = 5, 240 bpm, 0.8 V, and 0.05 ms pulses) or unstimulated (n = 6). Left ventricle geometry and function were measured at baseline (pre-MI) and at 7, 14, 21, and 28 days post-MI using echocardiography. MI size at 28 days post-MI was determined by histochemical staining and planimetry. RESULTS At 7 days post-MI and before randomization to localized high-frequency stimulation, left ventricular ejection fraction and end-diastolic volume was equivalent. However, when compared with 7-day post-MI values, left ventricle end-diastolic volume increased in a time-dependent manner in the MI unstimulated group, but the relative increase in left ventricle end-diastolic volume was reduced in the MI localized high-frequency stimulation group. For example, by 28 days post-MI, left ventricle end-diastolic volume increased by 32% in the MI unstimulated group but only by 12% in the MI localized high-frequency stimulation group (P < .05). Whereas left ventricular ejection fraction appeared unchanged between MI groups, estimates of pulmonary capillary wedge pressure, a marker of adverse left ventricle performance and progression to failure, increased by 62% in the MI unstimulated group and actually decreased by 17% in the MI localized high-frequency stimulation group when compared with 7-day post-MI values (P < .05). MI size was equivalent between the MI groups, indicative of no difference in the extent of absolute myocardial injury. CONCLUSIONS The unique findings from this study are 2-fold. First, targeting the MI region following the resolution of the acute event using a localized stimulation approach is feasible. Second, localized stimulation modified a key parameter of adverse post-MI remodeling (dilation) and progression to heart failure. These findings demonstrate that the MI region itself is a modifiable tissue and responsive to localized electrical stimulation.
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Novel therapeutic strategies targeting fibroblasts and fibrosis in heart disease. Nat Rev Drug Discov 2016; 15:620-638. [PMID: 27339799 DOI: 10.1038/nrd.2016.89] [Citation(s) in RCA: 221] [Impact Index Per Article: 27.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
Our understanding of the functions of cardiac fibroblasts has moved beyond their roles in heart structure and extracellular matrix generation and now includes their contributions to paracrine, mechanical and electrical signalling during ontogenesis and normal cardiac activity. Fibroblasts also have central roles in pathogenic remodelling during myocardial ischaemia, hypertension and heart failure. As key contributors to scar formation, they are crucial for tissue repair after interventions including surgery and ablation. Novel experimental approaches targeting cardiac fibroblasts are promising potential therapies for heart disease. Indeed, several existing drugs act, at least partially, through effects on cardiac connective tissue. This Review outlines the origins and roles of fibroblasts in cardiac development, homeostasis and disease; illustrates the involvement of fibroblasts in current and emerging clinical interventions; and identifies future targets for research and development.
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Leclercq C, Dievart F, Ruschitzka F. Peri-infarct pacing to prevent left reverse remodelling: an unvalidated concept? Eur Heart J 2016; 37:494-5. [DOI: 10.1093/eurheartj/ehv528] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
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Epstein AE. Complete Heart Block Complicating ST-Segment Elevation Myocardial Infarction Has Not Gone Away. JACC Clin Electrophysiol 2015; 1:539-541. [DOI: 10.1016/j.jacep.2015.09.005] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/04/2015] [Revised: 09/11/2015] [Accepted: 09/17/2015] [Indexed: 10/22/2022]
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Stone GW, Chung ES, Stancak B, Svendsen JH, Fischer TM, Kueffer F, Ryan T, Bax J, Leon A. Peri-infarct zone pacing to prevent adverse left ventricular remodelling in patients with large myocardial infarction. Eur Heart J 2015; 37:484-93. [PMID: 26321236 DOI: 10.1093/eurheartj/ehv436] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/04/2015] [Accepted: 08/12/2015] [Indexed: 11/13/2022] Open
Abstract
AIMS We sought to determine whether peri-infarct pacing prevents left ventricular (LV) remodelling and improves functional and clinical outcomes in patients with large first myocardial infarction (MI). METHODS AND RESULTS A total of 126 patients at 27 international sites within 10 days of onset of anterior or non-anterior MI with creatine phosphokinase >3000 U/L and QRS duration ≤120 ms were randomized 1:1:1 to dual-site biventricular pacing vs. single-site LV only pacing vs. non-implanted control. The primary endpoint was the echocardiographic core laboratory-assessed change in LV end-diastolic volume (ΔLVEDV) from baseline to 18 months between the pooled pacing therapy groups and the control group. ΔLVEDV increased by 15.3 ± 28.6 mL in the control group and by 16.7 ± 30.5 mL in the pooled pacing groups during follow-up (adjusted mean difference (95% CI) = 0.6 (-12.3, 13.5) mL, P = 0.92). There were also no significant between-group differences in the change in LV end-systolic volume or ejection fraction over time. Quality of life, as assessed by the Minnesota Living with Heart Failure (HF) and European Quality of Life-5 Dimension questionnaires and New York Heart Association class, was also similar between groups during 18-month follow-up. Six-minute walk distance improved during follow-up to an equal degree between groups, and there were no significant differences in the 18-month rates of death or HF hospitalization between the pooled pacing therapy vs. control groups (17.4 vs. 21.7% respectively, P = 0.59). CONCLUSIONS In the present multicentre, randomized trial, peri-infarct pacing did not prevent LV remodelling or improve functional or clinical outcomes during 18-month follow-up in patients with large first MI. CLINICALTRIALSGOV IDENTIFIER NCT01213251.
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Affiliation(s)
- Gregg W Stone
- Columbia University Medical Center, New York-Presbyterian Hospital, and the Cardiovascular Research Foundation, 111 E. 59th St., 11th Floor, New York, NY 10022, USA
| | | | - Branislav Stancak
- Eastern Slovakia Institute for Cardiac and Vascular Diseases, Kosice, Slovakia
| | - Jesper H Svendsen
- Rigshospitalet and the University of Copenhagen, Copenhagen, Denmark
| | | | | | - Thomas Ryan
- The Ohio State University, Columbus, OH, USA
| | - Jeroen Bax
- Leiden University Medical Center, Leiden, The Netherlands
| | - Angel Leon
- Emory University School of Medicine, Atlanta, GA, USA
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Chung ES, Fischer TM, Kueffer F, Anand IS, Bax JJ, Gold MR, Gorman RC, Theres H, Udelson JE, Stancak B, Svendsen JH, Stone GW, Leon A. The Post–Myocardial Infarction Pacing Remodeling Prevention Therapy (PRomPT) Trial: Design and Rationale. J Card Fail 2015; 21:601-7. [DOI: 10.1016/j.cardfail.2015.03.005] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/01/2014] [Revised: 02/02/2015] [Accepted: 03/10/2015] [Indexed: 11/29/2022]
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Chen Y, Cheng L, Yao H, Chen H, Wang Y, Zhao W, Pan C, Shu X. The myocardial ischemia evaluated by real-time contrast echocardiography may predict the response to cardiac resynchronization therapy: a large animal study. PLoS One 2014; 9:e113992. [PMID: 25469632 PMCID: PMC4254922 DOI: 10.1371/journal.pone.0113992] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/27/2014] [Accepted: 11/02/2014] [Indexed: 11/19/2022] Open
Abstract
Evidence-based criteria for applying cardiac resynchronization therapy (CRT) in patients with ischemic cardiomyopathy are still scarce. The aim of the present study was to evaluate the predictive value of real-time myocardial contrast echocardiography (RT-MCE) in a preclinical canine model of ischemic cardiomyopathy who received CRT. Ischemic cardiomyopathy was produced by ligating the first diagonal branch in 20 beagles. Dogs were subsequently divided into two groups that were either treated with bi-ventricular pacing (CRT group) or left untreated (control group). RT-MCE was performed at baseline, before CRT, and 4 weeks after CRT. Two-dimensional speckle tracking imaging was used to evaluate the standard deviation of circumferential (Cir12SD), radial (R12SD), and longitudinal (L12SD) strains of left ventricular segments at basal as well as middle levels. Four weeks later, the Cir12SD, R12SD, and myocardial blood flow (MBF) of the treated group were significantly improved compared to their non-CRT counterparts. Furthermore, MBF values measured before CRT were significantly higher in responders than in non-responders to bi-ventricular pacing. Meanwhile, no significant differences were observed between the responder and non-responder groups in terms of Cir12SD, R12SD, and L12SD. A high degree of correlation was found between MBF values before CRT and LVEF after CRT. When MBF value>24.9 dB/s was defined as a cut-off point before CRT, the sensitivity and specificity of RT-MCE in predicting the response to CRT were 83.3% and 100%, respectively. Besides, MBF values increased significantly in the CRT group compared with the control group after 4 weeks of pacing (49.8±15.5 dB/s vs. 28.5±4.6 dB/s, p<0.05). Therefore, we considered that myocardial perfusion may be superior to standard metrics of LV synchrony in selecting appropriate candidates for CRT. In addition, CRT can improve myocardial perfusion in addition to cardiac synchrony, especially in the setting of ischemic cardiomyopathy.
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Affiliation(s)
- Yongle Chen
- Department of Echocardiography, Zhongshan Hospital, Fudan University, Shanghai Institute of Cardiovascular Diseases, Shanghai Institute of Medical Imaging, Shanghai, PR China
| | - Leilei Cheng
- Department of Echocardiography, Zhongshan Hospital, Fudan University, Shanghai Institute of Cardiovascular Diseases, Shanghai Institute of Medical Imaging, Shanghai, PR China
| | - Haohua Yao
- Department of Echocardiography, Zhongshan Hospital, Fudan University, Shanghai Institute of Cardiovascular Diseases, Shanghai Institute of Medical Imaging, Shanghai, PR China
| | - Haiyan Chen
- Department of Echocardiography, Zhongshan Hospital, Fudan University, Shanghai Institute of Cardiovascular Diseases, Shanghai Institute of Medical Imaging, Shanghai, PR China
| | - Yongshi Wang
- Department of Echocardiography, Zhongshan Hospital, Fudan University, Shanghai Institute of Cardiovascular Diseases, Shanghai Institute of Medical Imaging, Shanghai, PR China
| | - Weipeng Zhao
- Department of Echocardiography, Zhongshan Hospital, Fudan University, Shanghai Institute of Cardiovascular Diseases, Shanghai Institute of Medical Imaging, Shanghai, PR China
| | - Cuizhen Pan
- Department of Echocardiography, Zhongshan Hospital, Fudan University, Shanghai Institute of Cardiovascular Diseases, Shanghai Institute of Medical Imaging, Shanghai, PR China
| | - Xianhong Shu
- Department of Echocardiography, Zhongshan Hospital, Fudan University, Shanghai Institute of Cardiovascular Diseases, Shanghai Institute of Medical Imaging, Shanghai, PR China
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Rouillard AD, Holmes JW. Coupled agent-based and finite-element models for predicting scar structure following myocardial infarction. PROGRESS IN BIOPHYSICS AND MOLECULAR BIOLOGY 2014; 115:235-43. [PMID: 25009995 DOI: 10.1016/j.pbiomolbio.2014.06.010] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/27/2014] [Accepted: 06/28/2014] [Indexed: 01/19/2023]
Abstract
Following myocardial infarction, damaged muscle is gradually replaced by collagenous scar tissue. The structural and mechanical properties of the scar are critical determinants of heart function, as well as the risk of serious post-infarction complications such as infarct rupture, infarct expansion, and progression to dilated heart failure. A number of therapeutic approaches currently under development aim to alter infarct mechanics in order to reduce complications, such as implantation of mechanical restraint devices, polymer injection, and peri-infarct pacing. Because mechanical stimuli regulate scar remodeling, the long-term consequences of therapies that alter infarct mechanics must be carefully considered. Computational models have the potential to greatly improve our ability to understand and predict how such therapies alter heart structure, mechanics, and function over time. Toward this end, we developed a straightforward method for coupling an agent-based model of scar formation to a finite-element model of tissue mechanics, creating a multi-scale model that captures the dynamic interplay between mechanical loading, scar deformation, and scar material properties. The agent-based component of the coupled model predicts how fibroblasts integrate local chemical, structural, and mechanical cues as they deposit and remodel collagen, while the finite-element component predicts local mechanics at any time point given the current collagen fiber structure and applied loads. We used the coupled model to explore the balance between increasing stiffness due to collagen deposition and increasing wall stress due to infarct thinning and left ventricular dilation during the normal time course of healing in myocardial infarcts, as well as the negative feedback between strain anisotropy and the structural anisotropy it promotes in healing scar. The coupled model reproduced the observed evolution of both collagen fiber structure and regional deformation following coronary ligation in the rat, and suggests that fibroblast alignment in the direction of greatest stretch provides negative feedback on the level of anisotropy in a scar forming under load. In the future, this coupled model may prove useful in computational design and screening of novel therapies to influence scar formation in mechanically loaded tissues.
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Affiliation(s)
- Andrew D Rouillard
- Department of Biomedical Engineering, University of Virginia, Charlottesville, VA 22908, USA
| | - Jeffrey W Holmes
- Department of Biomedical Engineering, Department of Medicine, Robert M. Berne Cardiovascular Research Center, University of Virginia, Charlottesville, VA 22908, USA.
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Impact of neonatal sertraline exposure on the post-myocardial infarction outcomes of adult male mice. J Cardiovasc Pharmacol 2014; 62:479-84. [PMID: 23921310 DOI: 10.1097/fjc.0b013e3182a4db90] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
Neonatal exposure to a selective serotonin reuptake inhibitor (SSRI) leads to decreased left ventricular volumes and sympathetic activation in adult mice. We hypothesized this neonatal SSRI exposure-induced small left heart syndrome would increase post-myocardial infarction (MI) morbidity and mortality. C57BL/6 mice received saline or sertraline (5 mg/kg intraperitoneally) on postnatal days 1-14. At 5 months, male mice underwent coronary artery ligation and were monitored by radiotelemetry until death or 4 weeks after ligation. After ligation, SSRI-exposed mice had increased heart rates (SSRI, 516 ± 13 bpm; control, 470 ± 15 bpm; P < 0.05). SSRI-exposed mice had significant reductions in left ventricular systolic volumes both before and after coronary ligation (SSRI: baseline = 20 ± 3 μL, post-MI = 37 ± 10 μL; control: baseline = 30 ± 3 μL, post-MI = 65 ± 23 μL). Post-MI echocardiography showed significantly decreased ejection fraction in control mice (baseline = 60% ± 4%, post-MI = 41% ± 2%, P < 0.01) but not the SSRI-exposed mice (baseline = 65% ± 3%, post-MI = 53% ± 7%). Neonatal SSRI exposure did not significantly alter post-MI survival. We conclude that the preexisting SSRI-induced small left heart syndrome may provide protection from post-MI ventricular dilation.
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Chow GV, Silverman MG, Tunin RS, Lardo AC, Nazarian S, Kass DA. Efficacy of cardiac resynchronization in acutely infarcted canine hearts with electromechanical dyssynchrony. Heart Rhythm 2014; 11:1819-26. [PMID: 24887137 DOI: 10.1016/j.hrthm.2014.05.036] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/22/2014] [Indexed: 10/25/2022]
Abstract
BACKGROUND Patients with acute myocardial infarction (MI), left bundle branch block (LBBB), and marked left ventricular (LV) decompensation suffer from nearly 50% early mortality. Whether cardiac resynchronization therapy (CRT) improves hemodynamic status in this condition is unknown. We tested CRT in this setting by using a canine model of delayed lateral wall (LW) activation combined with 2 hours of coronary artery occlusion-reperfusion. OBJECTIVE This study aimed to evaluate the acute hemodynamic effects of CRT during and immediately after MI. METHODS Adult dogs (n = 8) underwent open-chest 2-hour mid-left anterior descending artery occlusion followed by 1-hour reperfusion. Four pacing modes were compared: right atrial pacing, pseudo-left bundle block (right ventricular pacing), and CRT with the LV lead positioned at either the LW (LW-CRT) or the peri-infarct zone (peri-infarct zone-CRT). Continuous LV pressure-volume data, regional segment length, and proximal left anterior descending flow rates were recorded. RESULTS At baseline, both right ventricular pacing and peri-infarct zone CRT reduced anterior wall regional work by ~50% (vs right atrial pacing). During coronary occlusion, this territory became dyskinetic, and dyskinesis rose further with both CRT modes as compared to pseudo-LBBB. Global cardiac output, stroke work, and ejection fraction all still improved by 11%-23%. After reperfusion, both CRT modes elevated infarct zone regional work and blood flow by ~10% as compared to pseudo-LBBB, as well as improved global function. CONCLUSION CRT improves global chamber systolic function in left ventricles with delayed LW activation during and after sustained coronary occlusion. It does so while modestly augmenting infarct zone dyskinesis during occlusion and improving regional function and blood flow after reperfusion. These findings support CRT in the setting of early post-MI dyssynchronous heart failure.
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Affiliation(s)
- Grant V Chow
- Division of Cardiology, Johns Hopkins Medical Institutions, The Johns Hopkins University School of Medicine, Baltimore, Maryland
| | - Michael G Silverman
- Division of Cardiology, Johns Hopkins Medical Institutions, The Johns Hopkins University School of Medicine, Baltimore, Maryland
| | - Richard S Tunin
- Division of Cardiology, Johns Hopkins Medical Institutions, The Johns Hopkins University School of Medicine, Baltimore, Maryland
| | - Albert C Lardo
- Division of Cardiology, Johns Hopkins Medical Institutions, The Johns Hopkins University School of Medicine, Baltimore, Maryland
| | - Saman Nazarian
- Division of Cardiology, Johns Hopkins Medical Institutions, The Johns Hopkins University School of Medicine, Baltimore, Maryland
| | - David A Kass
- Division of Cardiology, Johns Hopkins Medical Institutions, The Johns Hopkins University School of Medicine, Baltimore, Maryland.
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Rationale and design of a randomized, double-blind, placebo-controlled clinical trial to evaluate the efficacy of B-type natriuretic peptide for the preservation of left ventricular function after anterior myocardial infarction. J Card Fail 2014; 19:533-9. [PMID: 23910581 DOI: 10.1016/j.cardfail.2013.06.002] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/25/2013] [Revised: 06/04/2013] [Accepted: 06/10/2013] [Indexed: 11/21/2022]
Abstract
BACKGROUND B-type natriuretic peptide (BNP) is a hormone with pleiotropic cardioprotective properties. Previously in our non-placebo-controlled non-blinded pilot study (BELIEVE) in human ST-segment-elevation anterior acute myocardial infarction (AMI), a 72-hour intravenous (IV) infusion of recombinant human BNP (nesiritide) at a dose of 0.006 μg kg(-1) min(-1) suppressed plasma aldosterone, reduced cardiac dilatation, and improved left ventricular (LV) ejection fraction (LVEF) at 1 month compared with baseline. METHODS AND DESIGN The BELIEVE II study is a phase II, randomized, double-blind, placebo-controlled, single-center clinical trial to assess the efficacy of 72-hour IV infusion of nesiritide therapy (0.006 μg kg(-1) min(-1)) in humans with first-time ST-segment-elevation anterior AMI and successful reperfusion, in preventing adverse LV remodeling and preserving LV function. A total of 60 patients will be randomized to placebo or nesiritide therapy. The primary efficacy end point is LV end-systolic and end-diastolic dimensions determined by multiple gated acquisition scan between placebo and nesiritide groups at 30 days; secondary end points include 30-day LVEF, diastolic function, infarct size, LV mass, and combined total mortality and heart failure hospitalization. CONCLUSIONS This will be the first randomized, double-blind, placebo-controlled clinical trial to assess the clinical efficacy of nesiritide in human ST-segment-elevation anterior AMI.
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Abstract
Initial studies established patient selection criteria for cardiac resynchronization therapy (CRT) as left ventricular ejection fraction less than or equal to 35%, QRS greater than or equal to 120 ms, and New York Heart Association 3-4. Based on newer data, post hoc analyses, and meta-analyses, these criteria have been refined and guidelines updated, highlighting left bundle branch morphology and QRS greater than 150 ms in selecting patients with a likelihood of favorable outcomes. Guidelines will change as more data become available; the decision to apply CRT should be based on patient clinical profile and the balance of risk tolerance and likelihood of benefit.
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Abstract
Over the past five decades, management of acute ST-segment elevation myocardial infarction (STEMI) has evolved substantially. Current treatment encompasses a systematic chain of network activation, antithrombotic drugs, and rapid instigation of mechanical reperfusion, although pharmacoinvasive strategies remain relevant. Secondary prevention with drugs and lifestyle modifications completes the contemporary management package. Despite a tangible improvement in outcomes, STEMI remains a frequent cause of morbidity and mortality, justifying the quest to find new therapeutic avenues. Ways to reduce delays in doing coronary angioplasty after STEMI onset include early recognition of symptoms by patients and prehospital diagnosis by paramedics so that the emergency room can be bypassed in favour of direct admission to the catheterisation laboratory. Mechanical reperfusion can be optimised by improvements to stent design, whereas visualisation of infarct size has been improved by developments in cardiac MRI. Novel treatments to modulate the inflammatory component of atherosclerosis and the vulnerable plaque include use of bioresorbable vascular scaffolds and anti-proliferative drugs. Translational efforts to improve patients' outcomes after STEMI in relation to cardioprotection, cardiac remodelling, and regeneration are also being realised.
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Affiliation(s)
- Stephan Windecker
- Department of Cardiology, Bern University Hospital, Bern, Switzerland.
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Fomovsky GM, Clark SA, Parker KM, Ailawadi G, Holmes JW. Anisotropic reinforcement of acute anteroapical infarcts improves pump function. Circ Heart Fail 2012; 5:515-22. [PMID: 22665716 DOI: 10.1161/circheartfailure.111.965731] [Citation(s) in RCA: 42] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
BACKGROUND We hypothesize that a therapy that improves left ventricular (LV) pump function early after infarction should decrease the need for compensation through sympathetic activation and dilation, thereby reducing the risk of developing heart failure. The mechanical properties of healing myocardial infarcts are an important determinant of LV function, yet improving function by altering infarct properties has proven unexpectedly difficult. Using a computational model, we recently predicted that stiffening a large anterior infarct anisotropically (in only one direction) would improve LV function, whereas isotropic stiffening, the focus of previous studies and therapies, would not. The goal of this study was to test the novel strategy of anisotropic infarct reinforcement. METHODS AND RESULTS We tested the effects of anisotropic infarct reinforcement in 10 open-chest dogs with large anteroapical infarcts that depressed LV pump function. We measured regional mechanics, LV volumes, and cardiac output at a range of preloads at baseline, 45 minutes after coronary ligation (ischemia), and 30 minutes later, after surgical reinforcement in the longitudinal direction (anisotropic). Ischemia shifted the end-systolic pressure-volume relationship and cardiac output curves rightward, decreasing cardiac output at matched end-diastolic pressure by 44%. Anisotropic reinforcement significantly improved systolic function without impairing diastolic function, recovering half the deficit in overall LV function. CONCLUSIONS We conclude that anisotropic reinforcement is a promising new approach to improving LV function after a large myocardial infarction.
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Affiliation(s)
- Gregory M Fomovsky
- Departments of Biomedical Engineering, Medicine, and Surgery and the Robert M. Berne Cardiovascular Research Center, University of Virginia, Charlottesville, VA 22908, USA
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Rouillard AD, Holmes JW. Mechanical regulation of fibroblast migration and collagen remodelling in healing myocardial infarcts. J Physiol 2012; 590:4585-602. [PMID: 22495588 DOI: 10.1113/jphysiol.2012.229484] [Citation(s) in RCA: 60] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
Effective management of healing and remodelling after myocardial infarction is an important problem in modern cardiology practice. We have recently shown that the level of infarct anisotropy is a critical determinant of heart function following a large anterior infarction, which suggests that therapeutic gains may be realized by controlling infarct anisotropy. However, factors regulating infarct anisotropy are not well understood. Mechanical, structural and chemical guidance cues have all been shown to regulate alignment of fibroblasts and collagen in vitro, and prior studies have proposed that each of these cues could regulate anisotropy of infarct scar tissue, but understanding of fibroblast behaviour in the complex environment of a healing infarct is lacking. We developed an agent-based model of infarct healing that accounted for the combined influence of these cues on fibroblast alignment, collagen deposition and collagen remodelling. We pooled published experimental data from several sources in order to determine parameter values, then used the model to test the importance of each cue for predicting collagen alignment measurements from a set of recent cryoinfarction experiments. We found that although chemokine gradients and pre-existing matrix structures had important effects on collagen organization, a response of fibroblasts to mechanical cues was critical for correctly predicting collagen alignment in infarct scar. Many proposed therapies for myocardial infarction, such as injection of cells or polymers, alter the mechanics of the infarct region. Our modelling results suggest that such therapies could change the anisotropy of the healing infarct, which could have important functional consequences. This model is therefore a potentially important tool for predicting how such interventions change healing outcomes.
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Affiliation(s)
- Andrew D Rouillard
- Department of Biomedical Engineering, University of Virginia, Charlottesville, VA 22908, USA
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Regional mechanics determine collagen fiber structure in healing myocardial infarcts. J Mol Cell Cardiol 2012; 52:1083-90. [PMID: 22418281 DOI: 10.1016/j.yjmcc.2012.02.012] [Citation(s) in RCA: 87] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/15/2011] [Revised: 02/10/2012] [Accepted: 02/28/2012] [Indexed: 11/20/2022]
Abstract
Following myocardial infarction, the mechanical properties of the healing infarct are an important determinant of heart function and the risk of progression to heart failure. In particular, mechanical anisotropy (having different mechanical properties in different directions) in the healing infarct can preserve pump function of the heart. Based on reports of different collagen structures and mechanical properties in various animal models, we hypothesized that differences in infarct size, shape, and/or location produce different patterns of mechanical stretch that guide evolving collagen fiber structure. We tested the effects of infarct shape and location using a combined experimental and computational approach. We studied mechanics and collagen fiber structure in cryoinfarcts in 53 Sprague-Dawley rats and found that regardless of shape or orientation, cryoinfarcts near the equator of the left ventricle stretched primarily in the circumferential direction and developed circumferentially aligned collagen, while infarcts at the apex stretched similarly in the circumferential and longitudinal directions and developed randomly oriented collagen. In a computational model of infarct healing, an effect of mechanical stretch on fibroblast and collagen alignment was required to reproduce the experimental results. We conclude that mechanical environment determines collagen fiber structure in healing myocardial infarcts. Our results suggest that emerging post-infarction therapies that alter regional mechanics will also alter infarct collagen structure, offering both potential risks and novel therapeutic opportunities.
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Circulation: Arrhythmia and Electrophysiology
Editors' Picks. Circ Arrhythm Electrophysiol 2012. [DOI: 10.1161/circep.112.970889] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
The following articles are being highlighted as part of
Circulation: Arrhythmia and Electrophysiology's
Topic Review series. This series will summarize the most important articles, as selected by the editors, published in
Circulation: Arrhythmia and Electrophysiology, Circulation,
and the other
Circulation
subspecialty journals. The studies included in this article represent the most read articles published on the topic of bradyarrhythmias in 2010 and 2011.
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Stolen CM, Lam YM, Siu CW, Lau CP, Parker JA, Hauser TH, Tse HF. Pacing to reduce refractory angina in patients with severe coronary artery disease: a crossover pilot trial. J Cardiovasc Transl Res 2011; 5:84-91. [PMID: 22038623 DOI: 10.1007/s12265-011-9326-7] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/24/2011] [Accepted: 10/12/2011] [Indexed: 11/27/2022]
Abstract
Biventricular pacing (BiV) has been shown to reduce wall stress and workload in regions near the pacing sites. This trial investigated if BiV near the ischemic region would reduce chest pain in patients with refractory angina due to severe coronary artery disease (CAD). Eleven patients were implanted with BiV devices with leads positioned at or adjacent to their ischemic regions as detected by single-photon emission computed tomography (SPECT) and randomized to either pacing turned ON or OFF for 3 months, and then crossed over for 3 months. With pacing turned ON, a Dynamic atrioventricular (AV) delay was set for approximately 90% and 70% of the intrinsic AV delay at the resting heart rate and at the onset of symptoms, respectively. One patient was excluded from the analysis due to a large amount of RV pacing during the OFF periods (24-64%) and due to an inability to properly deliver therapy because of an excessive number of ventricular premature complexes. Overall, with the device ON vs. OFF, the number of angina episodes (0.8 ± 0.4 vs. 1.2 ± 0.7 per week, P = 0.03) and amount of nitroglycerin used (0.2 ± 0.1 vs. 1.0 ± 0.7 per week, P = 0.11) was lower with BiV pacing. Furthermore, the treadmill exercise time to symptoms trended higher (427 ± 65 vs. 408 ± 64 s, P = 0.19), and the sum of fluorodeoxyglucose-positron emission tomography (FDG-PET) scores trended lower (7.9 ± 3.5 vs. 12.0 ± 4.0, P = 0.11) with the device ON vs. OFF. Nevertheless, there were no significant differences in SPECT myocardial perfusion scores, left ventricle ejection fraction, wall motion score index, and quality of life scores with device programmed ON vs. OFF (all P > 0.05). In conclusion, this pilot study demonstrated that BiV-P at or near the ischemic region was feasible and associated with significant reductions in angina in patients with severe CAD. Adequately powered prospective studies are needed to confirm these findings.
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Cornelussen RN, Splett V, Klepfer RN, Stegemann B, Kornet L, Prinzen FW. Electrical modalities beyond pacing for the treatment of heart failure. Heart Fail Rev 2011; 16:315-25. [PMID: 21104313 PMCID: PMC3074071 DOI: 10.1007/s10741-010-9206-2] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
In this review, we report on electrical modalities, which do not fit the definition of pacemaker, but increase cardiac performance either by direct application to the heart (e.g., post-extrasystolic potentiation or non-excitatory stimulation) or indirectly through activation of the nervous system (e.g., vagal or sympathetic activation). The physiological background of the possible mechanisms of these electrical modalities and their potential application to treat heart failure are discussed.
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Affiliation(s)
- Richard N Cornelussen
- Research and Technology, Medtronic Bakken Research Center BV, Endepolsdomein 5, 6229 GW Maastricht, The Netherlands.
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Huang G, Pashmforoush M, Chung B, Saxon LA. The role of cardiac electrophysiology in myocardial regenerative stem cell therapy. J Cardiovasc Transl Res 2010; 4:61-5. [PMID: 21128127 DOI: 10.1007/s12265-010-9239-x] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/28/2010] [Accepted: 10/28/2010] [Indexed: 12/26/2022]
Abstract
Recent advances in stem cell biology and tissue engineering have put forth new therapeutic paradigms for treatment of myocardial disease. The aim of stem cell therapy for myocardial regeneration has been directed to induce angiogenesis for ischemic heart disease and/or introduction of new cardiomyocytes to improve the mechanical function of the failing heart. Encouraged by positive preliminary results in mouse models of myocardial infarction, clinical trials have utilized autologous skeletal myoblasts and bone-marrow-derived stem cells to treat patients in various clinical settings including acute myocardial injury, chronic angina, and heart failure. These studies have collectively shown, at best, modest improvement in cardiac function. This may be due to the fact that there is little evidence to support actual formation and/or integration of transplanted cells into the recipient myocardium. More recent and emerging data supports the finding that electrical stimulation may be an effective catalyst for sustained functional organization, integration, and maturation of transplanted cell populations into the host myocardium. A therapeutic model that utilizes electrical stimulation and/or achieves cardiac resynchronization in conjunction with stem cell transplantation may be an effective means to achieve successful myocardial regenerative therapy.
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Affiliation(s)
- Grace Huang
- Division of Cardiovascular Medicine, Department of Medicine, LAC + USC Medical Center, Keck School of Medicine, University of Southern California, Los Angeles, CA, USA
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