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Sripusanapan A, Yanpiset P, Sriwichaiin S, Siri-Angkul N, Chattipakorn SC, Chattipakorn N. Hyperpolarization-activated cyclic nucleotide-gated channel inhibitor in myocardial infarction: Potential benefits beyond heart rate modulation. Acta Physiol (Oxf) 2024; 240:e14085. [PMID: 38230890 DOI: 10.1111/apha.14085] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/27/2023] [Revised: 10/24/2023] [Accepted: 01/01/2024] [Indexed: 01/18/2024]
Abstract
Myocardial infarction (MI) and its associated complications including ventricular arrhythmias and heart failure are responsible for a significant incidence of morbidity and mortality worldwide. The ensuing cardiomyocyte loss results in neurohormone-driven cardiac remodeling, which leads to chronic heart failure in MI survivors. Ivabradine is a heart rate modulation agent currently used in treatment of chronic heart failure with reduced ejection fraction. The canonical target of ivabradine is the hyperpolarization-activated cyclic nucleotide-gated channels (HCN) in cardiac pacemaker cells. However, in post-MI hearts, HCN can also be expressed ectopically in non-pacemaker cardiomyocytes. There is an accumulation of intriguing evidence to suggest that ivabradine also possesses cardioprotective effects that are independent of heart rate reduction. This review aims to summarize and discuss the reported cardioprotective mechanisms of ivabradine beyond heart rate modulation in myocardial infarction through various molecular mechanisms including the prevention of reactive oxygen species-induced mitochondrial damage, improvement of autophagy system, modulation of intracellular calcium cycling, modification of ventricular electrophysiology, and regulation of matrix metalloproteinases.
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Affiliation(s)
- Adivitch Sripusanapan
- Cardiac Electrophysiology Research and Training Center, Faculty of Medicine, Chiang Mai University, Chiang Mai, Thailand
- Center of Excellent in Cardiac Electrophysiology Research, Chiang Mai University, Chiang Mai, Thailand
- Cardiac Electrophysiology Unit, Department of Physiology, Faculty of Medicine, Chiang Mai University, Chiang Mai, Thailand
| | - Panat Yanpiset
- Cardiac Electrophysiology Research and Training Center, Faculty of Medicine, Chiang Mai University, Chiang Mai, Thailand
- Center of Excellent in Cardiac Electrophysiology Research, Chiang Mai University, Chiang Mai, Thailand
- Cardiac Electrophysiology Unit, Department of Physiology, Faculty of Medicine, Chiang Mai University, Chiang Mai, Thailand
| | - Sirawit Sriwichaiin
- Cardiac Electrophysiology Research and Training Center, Faculty of Medicine, Chiang Mai University, Chiang Mai, Thailand
- Center of Excellent in Cardiac Electrophysiology Research, Chiang Mai University, Chiang Mai, Thailand
- Cardiac Electrophysiology Unit, Department of Physiology, Faculty of Medicine, Chiang Mai University, Chiang Mai, Thailand
| | - Natthaphat Siri-Angkul
- Cardiac Electrophysiology Research and Training Center, Faculty of Medicine, Chiang Mai University, Chiang Mai, Thailand
- Center of Excellent in Cardiac Electrophysiology Research, Chiang Mai University, Chiang Mai, Thailand
- Cardiac Electrophysiology Unit, Department of Physiology, Faculty of Medicine, Chiang Mai University, Chiang Mai, Thailand
| | - Siriporn C Chattipakorn
- Cardiac Electrophysiology Research and Training Center, Faculty of Medicine, Chiang Mai University, Chiang Mai, Thailand
- Center of Excellent in Cardiac Electrophysiology Research, Chiang Mai University, Chiang Mai, Thailand
| | - Nipon Chattipakorn
- Cardiac Electrophysiology Research and Training Center, Faculty of Medicine, Chiang Mai University, Chiang Mai, Thailand
- Center of Excellent in Cardiac Electrophysiology Research, Chiang Mai University, Chiang Mai, Thailand
- Cardiac Electrophysiology Unit, Department of Physiology, Faculty of Medicine, Chiang Mai University, Chiang Mai, Thailand
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2
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Bazoukis G, Hill B, Tse G, Naka KK. Ivabradine: pre-clinical and clinical evidence in the setting of ventricular arrhythmias. Hippokratia 2022; 26:49-54. [PMID: 37188047 PMCID: PMC10177854] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/17/2023]
Abstract
BACKGROUND Ivabradine, an agent lowering the heart rate, acting as a funny current (If) specific inhibitor, is responsible for the sinoatrial node's spontaneous depolarization. According to current guidelines, it is indicated in specific heart failure populations and as a second-line treatment option to improve angina in chronic coronary syndromes. REVIEW OF LITERATURE The role of ivabradine in the setting of ventricular arrhythmias has been studied in both experimental and clinical studies. Specifically, experimental studies have examined the role of ivabradine in acute myocardial ischemia, reperfusion, digitalis-induced ventricular arrhythmias, and catecholaminergic polymorphic ventricular tachycardia showing promising results. In addition, clinical studies have shown a beneficial role of ivabradine in reducing ventricular arrhythmias. Ivabradine reduced premature ventricular contractions in combination with beta-blockers in dilated cardiomyopathy patients. Similarly, in catecholaminergic polymorphic ventricular tachycardia, ivabradine reduced dobutamine-induced premature ventricular complexes and improved ventricular arrhythmias burden. On the other hand, current data show no beneficial role of ivabradine in reducing ventricular arrhythmias in myocardial ischemia. CONCLUSIONS Randomized clinical trials are needed to elucidate the role of ivabradine in reducing the burden of ventricular arrhythmias in various clinical settings. HIPPOKRATIA 2022, 26 (2):49-54.
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Affiliation(s)
- G Bazoukis
- Department of Cardiology, Larnaca General Hospital, Larnaca, Cyprus
- Department of Basic and Clinical Sciences, University of Nicosia Medical School, Nicosia, Cyprus
| | - B Hill
- Department of Medicine, Queen's University, Kingston, Ontario, Canada
| | - G Tse
- Tianjin Key Laboratory of Ionic-Molecular Function of Cardiovascular Disease, Department of Cardiology, Tianjin Institute of Cardiology, Second Hospital of Tianjin Medical University, Tianjin, China
- Kent and Medway Medical School, Canterbury, Kent, United Kingdom
| | - K K Naka
- Second Department of Cardiology and Michaelidion Cardiac Center, Medical School University of Ioannina, Ioannina, Greece
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3
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Kaya ST, Agan K, Fulden-Agan A, Agyar-Yoldas P, Ozarslan TO, Kekecoglu M, Kaya A. Protective effect of propolis on myocardial ischemia/reperfusion injury in males and ovariectomized females but not in intact females. J Food Biochem 2022; 46:e14109. [PMID: 35142377 DOI: 10.1111/jfbc.14109] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/26/2021] [Revised: 12/12/2021] [Accepted: 01/22/2022] [Indexed: 11/30/2022]
Abstract
The aim of this study is to investigate the effect of propolis, which may have estrogenic effects, on myocardial ischemia/reperfusion (mI/R) injury not only in male rats but also in intact and ovariectomized (ovx) female rats. Six groups were formed: untreated males (n = 8), treated males (n = 9), untreated intact females (n = 9), treated intact females (n = 10), untreated ovx females (n = 10), and treated ovx females (n = 8). An alcoholic extract of a single dose of propolis (200 mg/kg) was administered orally daily for 14 days. Thirty minutes of ischemia and 120 min of reperfusion were performed. Blood pressure, heart rate, arrhythmias (ventricular premature contraction [VPC], ventricular tachycardia [VT], ventricular fibrillation [VF]), and myocardial infarct size were evaluated. Total antioxidant status (TAS), total oxidant status (TOS), superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GPx), and 17 beta-estradiol (E2) were measured. The untreated females showed more resistance to mI/R injury than the untreated males, as evidenced by lower duration, incidence, and score of arrhythmias, and smaller infarct size (p < .05). After ovx, this resistance disappeared. Propolis improved these values in treated males and treated ovx females (p < .05). Propolis increased TAS in treated males and decreased TOS in treated ovx females as well as elevated SOD in all treated groups (p < .05). Propolis decreased E2 level in treated intact females; however, it increased E2 level in treated ovx females (p < .05). The results revealed that propolis could protect the heart against mI/R injury in males and ovx females. PRACTICAL APPLICATIONS: It is known that the female heart has an increased sensitivity to myocardial ischemia/reperfusion (mI/R) injury due to estrogen deficiency and/or estrogen deprivation following menopause or surgical removal of the ovaries. Propolis has the potential to mimic estrogen under physiological and pathophysiological conditions, as well as its antioxidant property. The results indicated that propolis decreased myocardial infarct size, arrhythmia score, arrhythmia duration, and incidence in ovariectomized female rats and male rats. In addition, the present results demonstrated that an alcoholic extract of propolis as a natural product can effectively maintain the resistance of female heart to mI/R injury after estrogen deficiency.
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Affiliation(s)
- Salih Tunc Kaya
- Faculty of Arts and Science, Department of Biology, Duzce University, Duzce, Turkey
| | - Kagan Agan
- Coordination Unit of Healthy and Environmental, Duzce University, Duzce, Turkey
| | - Aydan Fulden-Agan
- Beekeeping Research, Development and Application Centre, Duzce University, Duzce, Turkey
| | - Pınar Agyar-Yoldas
- Coordination Unit of Healthy and Environmental, Duzce University, Duzce, Turkey
| | - Talat Ogulcan Ozarslan
- Faculty of Medicine, Department of Infectious Diseases and Clinical Microbiology, Bolu Abant Izzet Baysal University, Bolu, Turkey
| | - Meral Kekecoglu
- Faculty of Arts and Science, Department of Biology, Duzce University, Duzce, Turkey.,Beekeeping Research, Development and Application Centre, Duzce University, Duzce, Turkey
| | - Adnan Kaya
- Faculty of Medicine, Department of Internal Medicine, Cardiology Section, Duzce University, Duzce, Turkey
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4
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Li X, Shi X, Handa BS, Sau A, Zhang B, Qureshi NA, Whinnett ZI, Linton NWF, Lim PB, Kanagaratnam P, Peters NS, Ng FS. Classification of Fibrillation Organisation Using Electrocardiograms to Guide Mechanism-Directed Treatments. Front Physiol 2021; 12:712454. [PMID: 34858198 PMCID: PMC8632359 DOI: 10.3389/fphys.2021.712454] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/20/2021] [Accepted: 09/29/2021] [Indexed: 11/13/2022] Open
Abstract
Background: Atrial fibrillation (AF) and ventricular fibrillation (VF) are complex heart rhythm disorders and may be sustained by distinct electrophysiological mechanisms. Disorganised self-perpetuating multiple-wavelets and organised rotational drivers (RDs) localising to specific areas are both possible mechanisms by which fibrillation is sustained. Determining the underlying mechanisms of fibrillation may be helpful in tailoring treatment strategies. We investigated whether global fibrillation organisation, a surrogate for fibrillation mechanism, can be determined from electrocardiograms (ECGs) using band-power (BP) feature analysis and machine learning. Methods: In this study, we proposed a novel ECG classification framework to differentiate fibrillation organisation levels. BP features were derived from surface ECGs and fed to a linear discriminant analysis classifier to predict fibrillation organisation level. Two datasets, single-channel ECGs of rat VF (n = 9) and 12-lead ECGs of human AF (n = 17), were used for model evaluation in a leave-one-out (LOO) manner. Results: The proposed method correctly predicted the organisation level from rat VF ECG with the sensitivity of 75%, specificity of 80%, and accuracy of 78%, and from clinical AF ECG with the sensitivity of 80%, specificity of 92%, and accuracy of 88%. Conclusion: Our proposed method can distinguish between AF/VF of different global organisation levels non-invasively from the ECG alone. This may aid in patient selection and guiding mechanism-directed tailored treatment strategies.
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Affiliation(s)
- Xinyang Li
- National Heart and Lung Institute, Imperial College London, London, United Kingdom
| | - Xili Shi
- National Heart and Lung Institute, Imperial College London, London, United Kingdom
| | - Balvinder S. Handa
- National Heart and Lung Institute, Imperial College London, London, United Kingdom
| | - Arunashis Sau
- National Heart and Lung Institute, Imperial College London, London, United Kingdom
| | - Bowen Zhang
- National Heart and Lung Institute, Imperial College London, London, United Kingdom
| | - Norman A. Qureshi
- National Heart and Lung Institute, Imperial College London, London, United Kingdom
| | - Zachary I. Whinnett
- National Heart and Lung Institute, Imperial College London, London, United Kingdom
| | - Nick W. F. Linton
- Department of Bioengineering, Imperial College London, London, United Kingdom
| | - Phang Boon Lim
- National Heart and Lung Institute, Imperial College London, London, United Kingdom
| | - Prapa Kanagaratnam
- National Heart and Lung Institute, Imperial College London, London, United Kingdom
| | - Nicholas S. Peters
- National Heart and Lung Institute, Imperial College London, London, United Kingdom
| | - Fu Siong Ng
- National Heart and Lung Institute, Imperial College London, London, United Kingdom
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5
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Oknińska M, Paterek A, Zambrowska Z, Mackiewicz U, Mączewski M. Effect of Ivabradine on Cardiac Ventricular Arrhythmias: Friend or Foe? J Clin Med 2021; 10:4732. [PMID: 34682854 PMCID: PMC8537674 DOI: 10.3390/jcm10204732] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/24/2021] [Revised: 09/24/2021] [Accepted: 10/08/2021] [Indexed: 12/12/2022] Open
Abstract
Life-threatening ventricular arrhythmias, such as ventricular tachycardia and ventricular fibrillation remain an ongoing clinical problem and their prevention and treatment require optimization. Conventional antiarrhythmic drugs are associated with significant proarrhythmic effects that often outweigh their benefits. Another option, the implantable cardioverter defibrillator, though clearly the primary therapy for patients at high risk of ventricular arrhythmias, is costly, invasive, and requires regular monitoring. Thus there is a clear need for new antiarrhythmic treatment strategies. Ivabradine, a heartrate-reducing agent, an inhibitor of HCN channels, may be one of such options. In this review we discuss emerging data from experimental studies that indicate new mechanism of action of this drug and further areas of investigation and potential use of ivabradine as an antiarrhythmic agent. However, clinical evidence is limited, and the jury is still out on effects of ivabradine on cardiac ventricular arrhythmias in the clinical setting.
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Affiliation(s)
| | | | | | | | - Michał Mączewski
- Centre of Postgraduate Medical Education, Department of Clinical Physiology, ul. Marymoncka 99/103, 01-813 Warsaw, Poland; (M.O.); (A.P.); (Z.Z.); (U.M.)
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6
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Ronzhina M, Stracina T, Lacinova L, Ondacova K, Pavlovicova M, Marsanova L, Smisek R, Janousek O, Fialova K, Kolarova J, Novakova M, Provaznik I. Di-4-ANEPPS Modulates Electrical Activity and Progress of Myocardial Ischemia in Rabbit Isolated Heart. Front Physiol 2021; 12:667065. [PMID: 34177617 PMCID: PMC8222999 DOI: 10.3389/fphys.2021.667065] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/11/2021] [Accepted: 04/12/2021] [Indexed: 11/16/2022] Open
Abstract
Aims Although voltage-sensitive dye di-4-ANEPPS is a common tool for mapping cardiac electrical activity, reported effects on electrophysiological parameters are rather. The main goals of the study were to reveal effects of the dye on rabbit isolated heart and to verify, whether rabbit isolated heart stained with di-4-ANEPPS is a suitable tool for myocardial ischemia investigation. Methods and Results Study involved experiments on stained (n = 9) and non-stained (n = 11) Langendorff perfused rabbit isolated hearts. Electrophysiological effects of the dye were evaluated by analysis of various electrogram (EG) parameters using common paired and unpaired statistical tests. It was shown that staining the hearts with di-4-ANEPPS leads to only short-term sporadic prolongation of impulse conduction through atria and atrioventricular node. On the other hand, significant irreversible slowing of heart rate and ventricular conduction were found in stained hearts as compared to controls. In patch clamp experiments, significant inhibition of sodium current density was observed in differentiated NG108-15 cells stained by the dye. Although no significant differences in mean number of ventricular premature beats were found between the stained and the non-stained hearts in ischemia as well as in reperfusion, all abovementioned results indicate increased arrhythmogenicity. In isolated hearts during ischemia, prominent ischemic patterns appeared in the stained hearts with 3–4 min delay as compared to the non-stained ones. Moreover, the ischemic changes did not achieve the same magnitude as in controls even after 10 min of ischemia. It resulted in poor performance of ischemia detection by proposed EG parameters, as was quantified by receiver operating characteristics analysis. Conclusion Our results demonstrate significant direct irreversible effect of di-4-ANEPPS on spontaneous heart rate and ventricular impulse conduction in rabbit isolated heart model. Particularly, this should be considered when di-4-ANEPPS is used in ischemia studies in rabbit. Delayed attenuated response of such hearts to ischemia might lead to misinterpretation of obtained results.
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Affiliation(s)
- Marina Ronzhina
- Department of Biomedical Engineering, Faculty of Electrical Engineering and Communication, Brno University of Technology, Brno, Czechia
| | - Tibor Stracina
- Department of Physiology, Faculty of Medicine, Masaryk University, Brno, Czechia
| | - Lubica Lacinova
- Centre of Biosciences, Institute of Molecular Physiology and Genetics, Slovak Academy of Sciences, Bratislava, Slovakia
| | - Katarina Ondacova
- Centre of Biosciences, Institute of Molecular Physiology and Genetics, Slovak Academy of Sciences, Bratislava, Slovakia
| | - Michaela Pavlovicova
- Centre of Biosciences, Institute of Molecular Physiology and Genetics, Slovak Academy of Sciences, Bratislava, Slovakia
| | - Lucie Marsanova
- Department of Biomedical Engineering, Faculty of Electrical Engineering and Communication, Brno University of Technology, Brno, Czechia
| | - Radovan Smisek
- Department of Biomedical Engineering, Faculty of Electrical Engineering and Communication, Brno University of Technology, Brno, Czechia
| | - Oto Janousek
- Department of Biomedical Engineering, Faculty of Electrical Engineering and Communication, Brno University of Technology, Brno, Czechia
| | - Katerina Fialova
- Department of Physiology, Faculty of Medicine, Masaryk University, Brno, Czechia
| | - Jana Kolarova
- Department of Biomedical Engineering, Faculty of Electrical Engineering and Communication, Brno University of Technology, Brno, Czechia
| | - Marie Novakova
- Department of Physiology, Faculty of Medicine, Masaryk University, Brno, Czechia.,International Clinical Research Center, St. Anne's University Hospital Brno, Brno, Czechia
| | - Ivo Provaznik
- Department of Biomedical Engineering, Faculty of Electrical Engineering and Communication, Brno University of Technology, Brno, Czechia
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7
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Effect of ivabradine on cardiac arrhythmias: Antiarrhythmic or proarrhythmic? Heart Rhythm 2021; 18:1230-1238. [PMID: 33737235 DOI: 10.1016/j.hrthm.2021.03.020] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/19/2021] [Revised: 03/09/2021] [Accepted: 03/10/2021] [Indexed: 12/28/2022]
Abstract
Cardiac arrhythmias are a major source of mortality and morbidity. Unfortunately, their treatment remains suboptimal. Major classes of antiarrhythmic drugs pose a significant risk of proarrhythmia, and their side effects often outweigh their benefits. Therefore, implantable devices remain the only truly effective antiarrhythmic therapy, and new strategies of antiarrhythmic treatment are required. Ivabradine is a selective heart rate-reducing agent, an inhibitor of hyperpolarization-activated, cyclic nucleotide-gated (HCN) channels, currently approved for treatment of coronary artery disease and chronic heart failure. In this review, we focus on the clinical and basic science evidence for the antiarrhythmic and proarrhythmic effects of ivabradine. We attempt to dissect the mechanisms behind the effects of ivabradine and indicate the focus of future studies.
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8
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Jiang LP, Lin JJ, Zhuang TP, Wang WW, Wu HZ, Zhang FL. Effects of ivabradine on ventricular electrophysiological remodeling after myocardial infarction in rats. Arch Med Sci 2020; 19:1497-1507. [PMID: 37732052 PMCID: PMC10507765 DOI: 10.5114/aoms.2020.101181] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/10/2020] [Accepted: 10/22/2020] [Indexed: 09/22/2023] Open
Abstract
Introduction This study aims to investigate the effects of ivabradine (IVA) on ventricular electrophysiological remodeling after myocardial infarction (MI) in rats. Material and methods A total of 60 male Sprague-Dawley rats were randomly divided into five groups: an MI group, an IVA group, a metoprolol (MET) group, an IVA + MET group, and a sham group. After a four-week intervention, the ventricular electrophysiological parameters were detected by multichannel electrophysiological polygraph. Then, the morphological characteristics were evaluated using hematoxylin and eosin (H&E) and Masson's staining, and the expression of phosphorylated connexin 43 (p-Cx43) in the left ventricular wall was detected through immunohistochemistry and the Western blot test. Results The electrophysiological examination revealed that the induction rate and fatality rate of ventricular tachycardia (VT)/ventricular fibrillation (VF) were lower in both the IVA and the MET group, compared with the MI group (6/12, 6/12 vs. 10/11; and 1/12, 1/12 vs. 5/11; all p < 0.05), as well as the IVA + MET group (1/11 vs. 10/11, p < 0.01; and 1/11 vs. 5/11, p < 0.05). The induction rate of VT/VF was lower in the IVA + MET group, compared to the MET group (1/11 vs. 6/12, p < 0.05). H&E and Masson's staining revealed that compared with the MI group, the left ventricular infarction area was lower in the IVA, MET, and IVA + MET groups (p < 0.05, p < 0.05, and p < 0.01, respectively), while collagen volume fraction (CVF) also was lower in the other groups (all p < 0.01). The left ventricular infarction area and CVF both were lower in the IVA + MET group, compared to the MET group (p < 0.05 and p < 0.01, respectively). The immunohistochemistry and Western blot revealed that p-Cx43 expression was higher in the treatment groups, compared with the MI group (all p < 0.01). Conclusions IVA can reduce the incidence of ventricular arrhythmia after MI in male rats by improving both structural and electrical remodeling, and the combination of IVA and MET is even more effective.
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Affiliation(s)
- Li-ping Jiang
- Department of General Medicine, Mengchao Hepatobiliary Hospital of Fujian Medical University, Fuzhou, China
| | - Jing-jing Lin
- Department of Cardiology, Fujian Medical University Union Hospital and Fujian Provincial Institute of Coronary Disease, Fuzhou, China
| | - Ting-pei Zhuang
- Department of Cardiology, Fujian Medical University Union Hospital and Fujian Provincial Institute of Coronary Disease, Fuzhou, China
| | - Wei-wei Wang
- Department of Cardiology, Fujian Medical University Union Hospital and Fujian Provincial Institute of Coronary Disease, Fuzhou, China
| | - Hang-zhou Wu
- Medical Insurance Office, Fujian Medical University Union Hospital, Fuzhou, China
| | - Fei-long Zhang
- Department of Cardiology, Fujian Medical University Union Hospital and Fujian Provincial Institute of Coronary Disease, Fuzhou, China
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9
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Ferraro E, Pozhidaeva L, Pitcher DS, Mansfield C, Koh JHB, Williamson C, Aslanidi O, Gorelik J, Ng FS. Prolonged ursodeoxycholic acid administration reduces acute ischaemia-induced arrhythmias in adult rat hearts. Sci Rep 2020; 10:15284. [PMID: 32943714 PMCID: PMC7499428 DOI: 10.1038/s41598-020-72016-4] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/09/2020] [Accepted: 08/07/2020] [Indexed: 12/13/2022] Open
Abstract
Acute myocardial ischaemia and reperfusion (I-R) are major causes of ventricular arrhythmias in patients with a history of coronary artery disease. Ursodeoxycholic acid (UDCA) has previously been shown to be antiarrhythmic in fetal hearts. This study was performed to investigate if UDCA protects against ischaemia-induced and reperfusion-induced arrhythmias in the adult myocardium, and compares the effect of acute (perfusion only) versus prolonged (2 weeks pre-treatment plus perfusion) UDCA administration. Langendorff-perfused adult Sprague-Dawley rat hearts were subjected to acute regional ischaemia by ligation of the left anterior descending artery (10 min), followed by reperfusion (2 min), and arrhythmia incidence quantified. Prolonged UDCA administration reduced the incidence of acute ischaemia-induced arrhythmias (p = 0.028), with a reduction in number of ventricular ectopic beats during the ischaemic phase compared with acute treatment (10 ± 3 vs 58 ± 15, p = 0.036). No antiarrhythmic effect was observed in the acute UDCA administration group. Neither acute nor prolonged UDCA treatment altered the incidence of reperfusion arrhythmias. The antiarrhythmic effect of UDCA may be partially mediated by an increase in cardiac wavelength, due to the attenuation of conduction velocity slowing (p = 0.03), and the preservation of Connexin43 phosphorylation during acute ischaemia (p = 0.0027). The potential antiarrhythmic effects of prolonged UDCA administration merit further investigation.
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Affiliation(s)
- Elisa Ferraro
- National Heart and Lung Institute, Imperial College London, London, UK
| | - Lidia Pozhidaeva
- School of Biomedical Engineering and Imaging Science, King's College London, London, UK
| | - David S Pitcher
- National Heart and Lung Institute, Imperial College London, London, UK
| | | | - Jia Han Benjamin Koh
- School of Biomedical Engineering and Imaging Science, King's College London, London, UK
| | | | - Oleg Aslanidi
- School of Biomedical Engineering and Imaging Science, King's College London, London, UK
| | - Julia Gorelik
- National Heart and Lung Institute, Imperial College London, London, UK.
| | - Fu Siong Ng
- National Heart and Lung Institute, Imperial College London, London, UK.
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10
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Marciszek M, Paterek A, Oknińska M, Mackiewicz U, Mączewski M. Ivabradine is as effective as metoprolol in the prevention of ventricular arrhythmias in acute non-reperfused myocardial infarction in the rat. Sci Rep 2020; 10:15027. [PMID: 32929098 PMCID: PMC7490414 DOI: 10.1038/s41598-020-71706-3] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/03/2020] [Accepted: 07/29/2020] [Indexed: 12/29/2022] Open
Abstract
Ventricular arrhythmias are a major source of early mortality in acute myocardial infarction (MI) and remain a major therapeutic challenge. Thus we investigated effects of ivabradine, a presumably specific bradycardic agent versus metoprolol, a β-blocker, at doses offering the same heart rate (HR) reduction, on ventricular arrhythmias in the acute non-reperfused MI in the rat. Immediately after MI induction a single dose of ivabradine/ metoprolol was given. ECG was continuously recorded and ventricular arrhythmias were analyzed. After 6 h epicardial monophasic action potentials (MAPs) were recorded and cardiomyocyte Ca2+ handling was assessed. Both ivabradine and metoprolol reduced HR by 17% and arrhythmic mortality (14% and 19%, respectively, versus 33% in MI, p < 0.05) and ventricular arrhythmias in post-MI rats. Both drugs reduced QTc prolongation and decreased sensitivity of ryanodine receptors in isolated cardiomyocytes, but otherwise had no effect on Ca2+ handling, velocity of conduction or repolarization. We did not find any effects of potential IKr inhibition by ivabradine in this setting. Thus Ivabradine is an equally effective antiarrhythmic agent as metoprolol in early MI in the rat. It could be potentially tested as an alternative antiarrhythmic agent in acute MI when β-blockers are contraindicated.
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Affiliation(s)
- Mariusz Marciszek
- Department of Clinical Physiology, Centre of Postgraduate Medical Education, Warsaw, Poland
| | - Aleksandra Paterek
- Department of Clinical Physiology, Centre of Postgraduate Medical Education, Warsaw, Poland
| | - Marta Oknińska
- Department of Clinical Physiology, Centre of Postgraduate Medical Education, Warsaw, Poland
| | - Urszula Mackiewicz
- Department of Clinical Physiology, Centre of Postgraduate Medical Education, Warsaw, Poland
| | - Michał Mączewski
- Department of Clinical Physiology, Centre of Postgraduate Medical Education, Warsaw, Poland.
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11
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Handa BS, Li X, Aras KK, Qureshi NA, Mann I, Chowdhury RA, Whinnett ZI, Linton NW, Lim PB, Kanagaratnam P, Efimov IR, Peters NS, Ng FS. Granger Causality-Based Analysis for Classification of Fibrillation Mechanisms and Localization of Rotational Drivers. Circ Arrhythm Electrophysiol 2020; 13:e008237. [PMID: 32064900 PMCID: PMC7069398 DOI: 10.1161/circep.119.008237] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/24/2019] [Accepted: 02/04/2020] [Indexed: 11/16/2022]
Abstract
BACKGROUND The mechanisms sustaining myocardial fibrillation remain disputed, partly due to a lack of mapping tools that can accurately identify the mechanism with low spatial resolution clinical recordings. Granger causality (GC) analysis, an econometric tool for quantifying causal relationships between complex time-series, was developed as a novel fibrillation mapping tool and adapted to low spatial resolution sequentially acquired data. METHODS Ventricular fibrillation (VF) optical mapping was performed in Langendorff-perfused Sprague-Dawley rat hearts (n=18), where novel algorithms were developed using GC-based analysis to (1) quantify causal dependence of neighboring signals and plot GC vectors, (2) quantify global organization with the causality pairing index, a measure of neighboring causal signal pairs, and (3) localize rotational drivers (RDs) by quantifying the circular interdependence of neighboring signals with the circular interdependence value. GC-based mapping tools were optimized for low spatial resolution from downsampled optical mapping data, validated against high-resolution phase analysis and further tested in previous VF optical mapping recordings of coronary perfused donor heart left ventricular wedge preparations (n=12), and adapted for sequentially acquired intracardiac electrograms during human persistent atrial fibrillation mapping (n=16). RESULTS Global VF organization quantified by causality pairing index showed a negative correlation at progressively lower resolutions (50% resolution: P=0.006, R2=0.38, 12.5% resolution, P=0.004, R2=0.41) with a phase analysis derived measure of disorganization, locations occupied by phase singularities. In organized VF with high causality pairing index values, GC vector mapping characterized dominant propagating patterns and localized stable RDs, with the circular interdependence value showing a significant difference in driver versus nondriver regions (0.91±0.05 versus 0.35±0.06, P=0.0002). These findings were further confirmed in human VF. In persistent atrial fibrillation, a positive correlation was found between the causality pairing index and presence of stable RDs (P=0.0005,R2=0.56). Fifty percent of patients had RDs, with a low incidence of 0.9±0.3 RDs per patient. CONCLUSIONS GC-based fibrillation analysis can measure global fibrillation organization, characterize dominant propagating patterns, and map RDs using low spatial resolution sequentially acquired data.
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Affiliation(s)
- Balvinder S. Handa
- National Heart & Lung Institute, Imperial College London, United Kingdom (B.S.H., X.L., N.A.Q., I.M., R.A.C., Z.I.W., N.W.F.L., P.B.L., P.K., N.S.P., F.S.N.)
| | - Xinyang Li
- National Heart & Lung Institute, Imperial College London, United Kingdom (B.S.H., X.L., N.A.Q., I.M., R.A.C., Z.I.W., N.W.F.L., P.B.L., P.K., N.S.P., F.S.N.)
| | - Kedar K. Aras
- Department of Biomedical Engineering, George Washington University, Washington, DC (K.K.A., I.R.E.)
| | - Norman A. Qureshi
- National Heart & Lung Institute, Imperial College London, United Kingdom (B.S.H., X.L., N.A.Q., I.M., R.A.C., Z.I.W., N.W.F.L., P.B.L., P.K., N.S.P., F.S.N.)
| | - Ian Mann
- National Heart & Lung Institute, Imperial College London, United Kingdom (B.S.H., X.L., N.A.Q., I.M., R.A.C., Z.I.W., N.W.F.L., P.B.L., P.K., N.S.P., F.S.N.)
| | - Rasheda A. Chowdhury
- National Heart & Lung Institute, Imperial College London, United Kingdom (B.S.H., X.L., N.A.Q., I.M., R.A.C., Z.I.W., N.W.F.L., P.B.L., P.K., N.S.P., F.S.N.)
| | - Zachary I. Whinnett
- National Heart & Lung Institute, Imperial College London, United Kingdom (B.S.H., X.L., N.A.Q., I.M., R.A.C., Z.I.W., N.W.F.L., P.B.L., P.K., N.S.P., F.S.N.)
| | - Nick W.F. Linton
- National Heart & Lung Institute, Imperial College London, United Kingdom (B.S.H., X.L., N.A.Q., I.M., R.A.C., Z.I.W., N.W.F.L., P.B.L., P.K., N.S.P., F.S.N.)
| | - Phang Boon Lim
- National Heart & Lung Institute, Imperial College London, United Kingdom (B.S.H., X.L., N.A.Q., I.M., R.A.C., Z.I.W., N.W.F.L., P.B.L., P.K., N.S.P., F.S.N.)
| | - Prapa Kanagaratnam
- National Heart & Lung Institute, Imperial College London, United Kingdom (B.S.H., X.L., N.A.Q., I.M., R.A.C., Z.I.W., N.W.F.L., P.B.L., P.K., N.S.P., F.S.N.)
| | - Igor R. Efimov
- Department of Biomedical Engineering, George Washington University, Washington, DC (K.K.A., I.R.E.)
| | - Nicholas S. Peters
- National Heart & Lung Institute, Imperial College London, United Kingdom (B.S.H., X.L., N.A.Q., I.M., R.A.C., Z.I.W., N.W.F.L., P.B.L., P.K., N.S.P., F.S.N.)
- Department of Biomedical Engineering, George Washington University, Washington, DC (K.K.A., I.R.E.)
| | - Fu Siong Ng
- National Heart & Lung Institute, Imperial College London, United Kingdom (B.S.H., X.L., N.A.Q., I.M., R.A.C., Z.I.W., N.W.F.L., P.B.L., P.K., N.S.P., F.S.N.)
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Handa BS, Lawal S, Wright IJ, Li X, Cabello-García J, Mansfield C, Chowdhury RA, Peters NS, Ng FS. Interventricular Differences in Action Potential Duration Restitution Contribute to Dissimilar Ventricular Rhythms in ex vivo Perfused Hearts. Front Cardiovasc Med 2019; 6:34. [PMID: 31001543 PMCID: PMC6456660 DOI: 10.3389/fcvm.2019.00034] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/12/2018] [Accepted: 03/13/2019] [Indexed: 01/24/2023] Open
Abstract
Background: Dissimilar ventricular rhythms refer to the occurrence of different ventricular tachyarrhythmias in the right and left ventricles or different rates of the same tachyarrhythmia in the two ventricles. Objective: We investigated the inducibility of dissimilar ventricular rhythms, their underlying mechanisms, and the impact of anti-arrhythmic drugs (lidocaine and amiodarone) on their occurrence. Methods: Ventricular tachyarrhythmias were induced with burst pacing in 28 Langendorff-perfused Sprague Dawley rat hearts (14 control, 8 lidocaine, 6 amiodarone) and bipolar electrograms recorded from the right and left ventricles. Fourteen (6 control, 4 lidocaine, 4 amiodarone) further hearts underwent optical mapping of transmembrane voltage to study interventricular electrophysiological differences and mechanisms of dissimilar rhythms. Results: In control hearts, dissimilar ventricular rhythms developed in 8/14 hearts (57%). In lidocaine treated hearts, there was a lower cycle length threshold for developing dissimilar rhythms, with 8/8 (100%) hearts developing dissimilar rhythms in comparison to 0/6 in the amiodarone group. Dissimilar ventricular tachycardia (VT) rates occurred at longer cycle lengths with lidocaine vs. control (57.1 ± 7.9 vs. 36.6 ± 8.4 ms, p < 0.001). The ratio of LV:RV VT rate was greater in the lidocaine group than control (1.91 ± 0.30 vs. 1.76 ± 0.36, p < 0.001). The gradient of the action potential duration (APD) restitution curve was shallower in the RV compared with LV (Control - LV: 0.12 ± 0.03 vs RV: 0.002 ± 0.03, p = 0.015), leading to LV-to-RV conduction block during VT. Conclusion: Interventricular differences in APD restitution properties likely contribute to the occurrence of dissimilar rhythms. Sodium channel blockade with lidocaine increases the likelihood of dissimilar ventricular rhythms.
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Affiliation(s)
- Balvinder S. Handa
- National Heart and Lung Institute, Imperial College London, London, United Kingdom
| | - Saheed Lawal
- National Heart and Lung Institute, Imperial College London, London, United Kingdom
| | - Ian J. Wright
- Imperial College Healthcare NHS Trust, London, United Kingdom
| | - Xinyang Li
- National Heart and Lung Institute, Imperial College London, London, United Kingdom
| | | | - Catherine Mansfield
- National Heart and Lung Institute, Imperial College London, London, United Kingdom
| | - Rasheda A. Chowdhury
- National Heart and Lung Institute, Imperial College London, London, United Kingdom
| | - Nicholas S. Peters
- National Heart and Lung Institute, Imperial College London, London, United Kingdom
| | - Fu Siong Ng
- National Heart and Lung Institute, Imperial College London, London, United Kingdom
- Imperial College Healthcare NHS Trust, London, United Kingdom
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Wang J, Yang Y, Li Y, Zhu J, Lian H, Shao X, Zhang H, Fu Y, Zhang L. Long‐term treatment with ivabradine in transgenic atrial fibrillation mice counteracts hyperpolarization‐activated cyclic nucleotide gated channel overexpression. J Cardiovasc Electrophysiol 2018; 30:242-252. [PMID: 30302853 DOI: 10.1111/jce.13772] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/29/2018] [Revised: 09/24/2018] [Accepted: 10/08/2018] [Indexed: 01/20/2023]
Affiliation(s)
- Juan Wang
- Emergency and Intensive Care Center, State Key Laboratory of Cardiovascular DiseaseFuwai Hospital, National Center for Cardiovascular Disease, Chinese Academy of Medical Science and Peking Union Medical CollegeBeijing China
| | - Yan‐min Yang
- Emergency and Intensive Care Center, State Key Laboratory of Cardiovascular DiseaseFuwai Hospital, National Center for Cardiovascular Disease, Chinese Academy of Medical Science and Peking Union Medical CollegeBeijing China
| | - Yang Li
- Department of CardiologyChinese PLA General HospitalBeijing China
| | - Jun Zhu
- Emergency and Intensive Care Center, State Key Laboratory of Cardiovascular DiseaseFuwai Hospital, National Center for Cardiovascular Disease, Chinese Academy of Medical Science and Peking Union Medical CollegeBeijing China
| | - Hong Lian
- State Key Laboratory of Cardiovascular DiseaseFuwai Hospital, National Center for Cardiovascular diseases, Chinese Academy of Medical Sciences and Peking Union Medical CollegeBeijing China
| | - Xing‐hui Shao
- Emergency and Intensive Care Center, State Key Laboratory of Cardiovascular DiseaseFuwai Hospital, National Center for Cardiovascular Disease, Chinese Academy of Medical Science and Peking Union Medical CollegeBeijing China
| | - Han Zhang
- Emergency and Intensive Care Center, State Key Laboratory of Cardiovascular DiseaseFuwai Hospital, National Center for Cardiovascular Disease, Chinese Academy of Medical Science and Peking Union Medical CollegeBeijing China
| | - Yi‐cheng Fu
- Department of GeriatricsPeking University Third HospitalBeijing China
| | - Lian‐feng Zhang
- Key Laboratory of Human Disease Comparative MedicineMinistry of Health, Institute of Laboratory Animal Science, Chinese Academy of Medical Sciences and Peking Union Medical CollegeBeijing China
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Kim HB, Hong YJ, Park HJ, Ahn Y, Jeong MH. Effects of Ivabradine on Left Ventricular Systolic Function and Cardiac Fibrosis in Rat Myocardial Ischemia-Reperfusion Model. Chonnam Med J 2018; 54:167-172. [PMID: 30288372 PMCID: PMC6165924 DOI: 10.4068/cmj.2018.54.3.167] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/19/2018] [Revised: 08/14/2018] [Accepted: 08/16/2018] [Indexed: 12/12/2022] Open
Abstract
We evaluated the effects of Ivabradine on left ventricle (LV) ejection fraction (EF) and LV infarcted tissue in the rat myocardial ischemia-reperfusion model. Twenty rats were randomly assigned to group 1 (ischemia-reperfusion, no treatment, n=10) and group 2 (ischemia-reperfusion + Ivabradine 10 mg/kg, n=10). Ivabradine was administered for 28 days. Echocardiography was performed at 7 days and at 28 days after the induction of ischemia-reperfusion injury. Cardiac fibrosis induced by ischemia-reperfusion injury was evaluated by Masson's trichrome staining. The infarct size was quantified using the Image J program. At the 28-day follow-up, LVEF was significantly higher (36.02±6.16% vs. 45.72±2.62%, p<0.001) and fractional shortening was significantly higher (15.23±2.84% vs. 20.13±1.38%, p<0.001) in group 2 than group 1. Delta (28 day minus 7 day) EF was significantly higher in group 2 than group 1 (-4.36±3.49% vs. 4.31±5.63%, p<0.001). Also, heart rate (beats/min) was significantly lower in group 2 than group 1 (251.67±25.19 vs. 199.29±31.33, p=0.025). Group 2 had a smaller infarct size (40.70±8.94% vs. 30.19±5.89%, p<0.01) than group 1 at 28-day follow-up. Oral administration of Ivabradine could improve LV systolic function and reduce infarcted tissue area in rat myocardial ischemia-reperfusion model.
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Affiliation(s)
- Han Byul Kim
- Division of Cardiology, Chonnam National University Hospital, Cardiovascular Convergence Research Center Nominated by Korea Ministry of Health and Welfare, Gwangju, Korea
| | - Young Joon Hong
- Division of Cardiology, Chonnam National University Hospital, Cardiovascular Convergence Research Center Nominated by Korea Ministry of Health and Welfare, Gwangju, Korea
| | - Hyuk Jin Park
- Division of Cardiology, Chonnam National University Hospital, Cardiovascular Convergence Research Center Nominated by Korea Ministry of Health and Welfare, Gwangju, Korea
| | - Youngkeun Ahn
- Division of Cardiology, Chonnam National University Hospital, Cardiovascular Convergence Research Center Nominated by Korea Ministry of Health and Welfare, Gwangju, Korea
| | - Myung Ho Jeong
- Division of Cardiology, Chonnam National University Hospital, Cardiovascular Convergence Research Center Nominated by Korea Ministry of Health and Welfare, Gwangju, Korea
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Mengesha HG, Tafesse TB, Bule MH. If Channel as an Emerging Therapeutic Target for Cardiovascular Diseases: A Review of Current Evidence and Controversies. Front Pharmacol 2017; 8:874. [PMID: 29225577 PMCID: PMC5705549 DOI: 10.3389/fphar.2017.00874] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/07/2017] [Accepted: 11/13/2017] [Indexed: 01/09/2023] Open
Abstract
In 2015, non-communicable diseases accounted for 39.5 million (70%) of the total 56.4 million deaths that occurred globally, of which 17.7 million (45%) were due to cardiovascular diseases. An elevated heart rate is considered to be one of the independent predictors and markers of future cardiovascular diseases. A variety of experimental and epidemiological studies have found that atherosclerosis, heart failure, coronary artery disease, stroke, and arrhythmia are linked to elevated heart rate. Although there are established drugs to reduce the heart rate, these drugs have undesirable side effects. Hence, the development of new drugs that selectively inhibit the heart rate is considered necessary. In the search for such drugs, almost four decades ago the If channel, also known as the “funny channel,” emerged as a novel site for the selective inhibition of heart rate. These If channels, with a mixed sodium and potassium inward current, have been identified in the sinoatrial node of the heart, which mediates the slow diastolic depolarization of the pacemaker of the spontaneous rhythmic cells. The hyperpolarization-activated cyclic nucleotide-gated (HCN) subfamily is primarily articulated in the heart and neurons that are encoded by a family of four genes (HCN1-4) and they identify the funny channel. Of these, HCN-4 is the principal protein in the sinoatrial node. Currently, funny channel inhibition is being targeted for the treatment and prevention of cardiovascular diseases such as atherosclerosis and stroke. A selective If channel inhibitor named ivabradine was discovered for clinical use in treating heart failure and coronary artery disease. However, inconsistencies regarding the clinical effects of ivabradine have been reported in the literature, suggesting the need for a rigorous analysis of the available evidence. The objective of this review is therefore to assess the current advances in targeting the If channel associated with ivabradine and related challenges.
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Affiliation(s)
- Hayelom G Mengesha
- Pharmacology and Toxicology Research Unit, School of Pharmacy, Mekelle University, Mekelle, Ethiopia.,College of Medicine and Health Science, Adigrat University, Adigrat, Ethiopia
| | - Tadesse B Tafesse
- School of Pharmacy, College of Health and Medical Sciences, Haramaya University, Harar, Ethiopia
| | - Mohammed H Bule
- Department of Pharmacy, College of Medicine and Health Sciences, Ambo University, Ambo, Ethiopia
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Frommeyer G, Sterneberg M, Dechering DG, Ellermann C, Bögeholz N, Kochhäuser S, Pott C, Fehr M, Eckardt L. Effective suppression of atrial fibrillation by ivabradine: Novel target for an established drug? Int J Cardiol 2017; 236:237-243. [DOI: 10.1016/j.ijcard.2017.02.055] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/07/2016] [Revised: 01/25/2017] [Accepted: 02/15/2017] [Indexed: 12/28/2022]
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Niccoli G, Borovac JA, Vetrugno V, Camici PG, Crea F. Ivabradine in acute coronary syndromes: Protection beyond heart rate lowering. Int J Cardiol 2017; 236:107-112. [DOI: 10.1016/j.ijcard.2017.02.046] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/23/2016] [Revised: 02/07/2017] [Accepted: 02/13/2017] [Indexed: 12/26/2022]
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Ng FS, Kalindjian JM, Cooper SA, Chowdhury RA, Patel PM, Dupont E, Lyon AR, Peters NS. Enhancement of Gap Junction Function During Acute Myocardial Infarction Modifies Healing and Reduces Late Ventricular Arrhythmia Susceptibility. JACC Clin Electrophysiol 2016; 2:574-582. [PMID: 27807593 PMCID: PMC5076465 DOI: 10.1016/j.jacep.2016.03.007] [Citation(s) in RCA: 25] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
OBJECTIVES The purpose of this study was to investigate the effects of enhancing gap junction (GJ) coupling during acute myocardial infarction (MI) on the healed infarct scar morphology and late post-MI arrhythmia susceptibility. BACKGROUND Increased heterogeneity of myocardial scarring after MI is associated with greater arrhythmia susceptibility. We hypothesized that short-term enhancement of GJ coupling during acute MI can produce more homogeneous infarct scars, reducing late susceptibility to post-MI arrhythmias. METHODS Following arrhythmic characterization of a rat 4-week post-MI model (n = 24), another 27 Sprague-Dawley rats were randomized to receive rotigaptide to enhance GJ coupling (n = 13) or to saline control (n = 14) by osmotic minipump immediately prior to and for the first 7 days following surgically induced MI. At 4 weeks post-MI, hearts were explanted for ex vivo programmed electrical stimulation (PES) and optical mapping. Heterogeneity of infarct border zone (IBZ) scarring was quantified by histomorphometry. RESULTS Despite no detectable differences in infarct size at 4 weeks post-MI, rotigaptide-treated hearts had reduced arrhythmia susceptibility during PES (inducibility score for rotigaptide: 2.4 ± 0.8; for control: 5.0 ± 0.6; p = 0.02) and less heterogeneous IBZ scarring (dispersion of IBZ complexity score: rotigaptide: 1.1 ± 0.1; control: 1.4 ± 0.1; p = 0.04), associated with an improvement in IBZ conduction velocity (rotigaptide: 43.1 ± 3.4 cm/s; control: 34.8 ± 2.0 cm/s; p = 0.04). CONCLUSIONS Enhancement of GJ coupling for only 7 days at the time of acute MI produced more homogeneous IBZ scarring and reduced arrhythmia susceptibility at 4 weeks post-MI. Short-term GJ modulation at the time of MI may represent a novel treatment strategy to modify the healed infarct scar morphology and reduce late post-MI arrhythmic risk.
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Affiliation(s)
- Fu Siong Ng
- Imperial College, London, United Kingdom; Myocardial Function, National Heart & Lung Institute, Imperial College, London, United Kingdom.
| | - Jeremy M Kalindjian
- Imperial College, London, United Kingdom; Myocardial Function, National Heart & Lung Institute, Imperial College, London, United Kingdom
| | - Simon A Cooper
- Imperial College, London, United Kingdom; Myocardial Function, National Heart & Lung Institute, Imperial College, London, United Kingdom
| | - Rasheda A Chowdhury
- Imperial College, London, United Kingdom; Myocardial Function, National Heart & Lung Institute, Imperial College, London, United Kingdom
| | - Pravina M Patel
- Imperial College, London, United Kingdom; Myocardial Function, National Heart & Lung Institute, Imperial College, London, United Kingdom
| | - Emmanuel Dupont
- Imperial College, London, United Kingdom; Myocardial Function, National Heart & Lung Institute, Imperial College, London, United Kingdom
| | - Alexander R Lyon
- Imperial College, London, United Kingdom; Myocardial Function, National Heart & Lung Institute, Imperial College, London, United Kingdom
| | - Nicholas S Peters
- Imperial College, London, United Kingdom; Myocardial Function, National Heart & Lung Institute, Imperial College, London, United Kingdom
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20
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Spironolactone Regulates HCN Protein Expression Through Micro-RNA-1 in Rats With Myocardial Infarction. J Cardiovasc Pharmacol 2016; 65:587-92. [PMID: 26065643 PMCID: PMC4461389 DOI: 10.1097/fjc.0000000000000227] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Abstract
Emerging evidence has shown that aldosterone blockers reduced the incidence of ventricular arrhythmias in patients with myocardial infarction (MI). However, the mechanism remains unknown. In this study, we investigated the mechanism by which spironolactone, a classic aldosterone blocker, regulates hyperpolarization-activated cyclic nucleotide-gated channel (HCN) protein expression in ischemic rat myocardium after MI. Eighteen rats surviving 24 hours after MI were randomly assigned into 3 groups: MI, spironolactone, and spironolactone + antagomir-1. Six sham-operated rats had a suture loosely tied around the left coronary artery, without ligation. The border zone of the myocardial infarct was collected from each rat at 1 week after MI. HCN2 and HCN4 protein and messenger RNA (mRNA) level were measured in addition to miRNA-1 levels. Spironolactone significantly increased miRNA-1 levels and downregulated HCN2 and HCN4 protein and mRNA levels. miRNA-1 suppression with antagomir-1 increased HCN2 and HCN4 protein levels; however, HCN2 and HCN4 mRNA levels were not affected. These results suggested that spironolactone could increase miRNA-1 expression in ischemic rat myocardium after MI and that the upregulation of miRNA-1 expression partially contributed to the posttranscriptional repression of HCN protein expression, which may contribute to the effect of spironolactone to reduce the incidence of MI-associated ventricular arrhythmias.
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Garg V, Taylor T, Warren M, Venable P, Sciuto K, Shibayama J, Zaitsev A. β-Adrenergic stimulation and rapid pacing mutually promote heterogeneous electrical failure and ventricular fibrillation in the globally ischemic heart. Am J Physiol Heart Circ Physiol 2015; 308:H1155-70. [PMID: 25713306 PMCID: PMC4551128 DOI: 10.1152/ajpheart.00768.2014] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/24/2014] [Accepted: 02/16/2015] [Indexed: 01/09/2023]
Abstract
Global ischemia, catecholamine surge, and rapid heart rhythm (RHR) due to ventricular tachycardia or ventricular fibrillation (VF) are the three major factors of sudden cardiac arrest (SCA). Loss of excitability culminating in global electrical failure (asystole) is the major adverse outcome of SCA with increasing prevalence worldwide. The roles of catecholamines and RHR in the electrical failure during SCA remain unclear. We hypothesized that both β-adrenergic stimulation (βAS) and RHR accelerate electrical failure in the globally ischemic heart. We performed optical mapping of the action potential (OAP) in the right ventricular (RV) and left (LV) ventricular epicardium of isolated rabbit hearts subjected to 30-min global ischemia. Hearts were paced at a cycle length of either 300 or 200 ms, and either in the presence or in the absence of β-agonist isoproterenol (30 nM). 2,3-Butanedione monoxime (20 mM) was used to reduce motion artifact. We found that RHR and βAS synergistically accelerated the decline of the OAP upstroke velocity and the progressive expansion of inexcitable regions. Under all conditions, inexcitability developed faster in the LV than in the RV. At the same time, both RHR and βAS shortened the time to VF (TVF) during ischemia. Moreover, the time at which 10% of the mapped LV area became inexcitable strongly correlated with TVF (R(2) = 0 .72, P < 0.0001). We conclude that both βAS and RHR are major factors of electrical depression and failure in the globally ischemic heart and may contribute to adverse outcomes of SCA such as asystole and recurrent/persistent VF.
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Affiliation(s)
- Vivek Garg
- Nora Eccles Harrison Cardiovascular Research and Training Institute, University of Utah, Salt Lake City, Utah
| | - Tyson Taylor
- Nora Eccles Harrison Cardiovascular Research and Training Institute, University of Utah, Salt Lake City, Utah; Department of Bioengineering, University of Utah, Salt Lake City, Utah; and
| | - Mark Warren
- Nora Eccles Harrison Cardiovascular Research and Training Institute, University of Utah, Salt Lake City, Utah; Department of Bioengineering, University of Utah, Salt Lake City, Utah; and
| | - Paul Venable
- Nora Eccles Harrison Cardiovascular Research and Training Institute, University of Utah, Salt Lake City, Utah; Department of Bioengineering, University of Utah, Salt Lake City, Utah; and
| | - Katie Sciuto
- Nora Eccles Harrison Cardiovascular Research and Training Institute, University of Utah, Salt Lake City, Utah; Department of Bioengineering, University of Utah, Salt Lake City, Utah; and
| | - Junko Shibayama
- Nora Eccles Harrison Cardiovascular Research and Training Institute, University of Utah, Salt Lake City, Utah; Department of Internal Medicine, School of Medicine, University of Utah, Salt Lake City, Utah
| | - Alexey Zaitsev
- Nora Eccles Harrison Cardiovascular Research and Training Institute, University of Utah, Salt Lake City, Utah; Department of Bioengineering, University of Utah, Salt Lake City, Utah; and
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Wu L, Tan JL, Wang ZH, Chen YX, Gao L, Liu JL, Shi YH, Endoh M, Yang HT. ROS generated during early reperfusion contribute to intermittent hypobaric hypoxia-afforded cardioprotection against postischemia-induced Ca(2+) overload and contractile dysfunction via the JAK2/STAT3 pathway. J Mol Cell Cardiol 2015; 81:150-61. [PMID: 25731682 DOI: 10.1016/j.yjmcc.2015.02.015] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/10/2014] [Revised: 02/17/2015] [Accepted: 02/19/2015] [Indexed: 01/09/2023]
Abstract
Moderate enhanced reactive oxygen species (ROS) during early reperfusion trigger the cardioprotection against ischemia/reperfusion (I/R) injury, while the mechanism is largely unknown. Janus kinase 2 (JAK2)/signal transducer and activator of transcription 3 (STAT3) contributes to the cardioprotection but whether it is activated by ROS and how it regulates Ca(2+) homeostasis remain unclear. Here we investigated whether the ROS generated during early reperfusion protect the heart/cardiomyocyte against I/R-induced Ca(2+) overload and contractile dysfunction via the activation of JAK2/STAT3 signaling pathway by using a cardioprotective model of intermittent hypobaric hypoxia (IHH) preconditioning. IHH improved the postischemic recovery of myocardial contractile performance in isolated rat I/R hearts as well as Ca(2+) homeostasis and cell contraction in simulated I/R cardiomyocytes. Meanwhile, IHH enhanced I/R-increased STAT3 phosphorylation at tyrosine 705 in the nucleus and reversed I/R-suppressed STAT3 phosphorylation at serine 727 in the nucleus and mitochondria during reperfusion. Moreover, IHH improved I/R-suppressed sarcoplasmic reticulum (SR) Ca(2+)-ATPase 2 (SERCA2) activity, enhanced I/R-increased Bcl-2 expression, and promoted the co-localization and interaction of Bcl-2 with SERCA2 during reperfusion. These effects were abolished by scavenging ROS with N-(2-mercaptopropionyl)-glycine (2-MPG) and/or by inhibiting JAK2 with AG490 during the early reperfusion. Furthermore, IHH-improved postischemic SERCA2 activity and Ca(2+) homeostasis as well as cell contraction were reversed after Bcl-2 knockdown by short hairpin RNA. In addition, the reversal of the I/R-suppressed mitochondrial membrane potential by IHH was abolished by 2-MPG and AG490. These results indicate that during early reperfusion the ROS/JAK2/STAT3 pathways play a crucial role in (i) the IHH-maintained intracellular Ca(2+) homeostasis via the improvement of postischemic SERCA2 activity through the increase of SR Bcl-2 and its interaction with SERCA2; and (ii) the IHH-improved mitochondrial function.
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Affiliation(s)
- Lan Wu
- Key Laboratory of Stem Cell Biology and Laboratory of Molecular Cardiology, Institute of Health Sciences, Shanghai Institutes for Biological Sciences (SIBS), Chinese Academy of Sciences (CAS) & Shanghai Jiao Tong University School of Medicine (SJTUSM), Shanghai, China
| | - Ji-Liang Tan
- Key Laboratory of Stem Cell Biology and Laboratory of Molecular Cardiology, Institute of Health Sciences, Shanghai Institutes for Biological Sciences (SIBS), Chinese Academy of Sciences (CAS) & Shanghai Jiao Tong University School of Medicine (SJTUSM), Shanghai, China
| | - Zhi-Hua Wang
- Key Laboratory of Stem Cell Biology and Laboratory of Molecular Cardiology, Institute of Health Sciences, Shanghai Institutes for Biological Sciences (SIBS), Chinese Academy of Sciences (CAS) & Shanghai Jiao Tong University School of Medicine (SJTUSM), Shanghai, China; Division of Molecular Medicine, Department of Anesthesiology, David Geffen School of Medicine at UCLA, Los Angeles, USA
| | - Yi-Xiong Chen
- Key Laboratory of Stem Cell Biology and Laboratory of Molecular Cardiology, Institute of Health Sciences, Shanghai Institutes for Biological Sciences (SIBS), Chinese Academy of Sciences (CAS) & Shanghai Jiao Tong University School of Medicine (SJTUSM), Shanghai, China
| | - Ling Gao
- Key Laboratory of Stem Cell Biology and Laboratory of Molecular Cardiology, Institute of Health Sciences, Shanghai Institutes for Biological Sciences (SIBS), Chinese Academy of Sciences (CAS) & Shanghai Jiao Tong University School of Medicine (SJTUSM), Shanghai, China
| | - Jin-Long Liu
- Key Laboratory of Stem Cell Biology and Laboratory of Molecular Cardiology, Institute of Health Sciences, Shanghai Institutes for Biological Sciences (SIBS), Chinese Academy of Sciences (CAS) & Shanghai Jiao Tong University School of Medicine (SJTUSM), Shanghai, China
| | - Yun-Hua Shi
- Key Laboratory of Stem Cell Biology and Laboratory of Molecular Cardiology, Institute of Health Sciences, Shanghai Institutes for Biological Sciences (SIBS), Chinese Academy of Sciences (CAS) & Shanghai Jiao Tong University School of Medicine (SJTUSM), Shanghai, China
| | - Masao Endoh
- Department of Pharmacology, Yamagata University School of Medicine, Yamagata, Japan
| | - Huang-Tian Yang
- Key Laboratory of Stem Cell Biology and Laboratory of Molecular Cardiology, Institute of Health Sciences, Shanghai Institutes for Biological Sciences (SIBS), Chinese Academy of Sciences (CAS) & Shanghai Jiao Tong University School of Medicine (SJTUSM), Shanghai, China.
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23
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Alexandre J, Beygui F, Puddu PE, Manrique A, Rouet R, Milliez P. Electrophysiological and antiarrhythmic properties of potassium canrenoate during myocardial ischemia-reperfusion. J Cardiovasc Pharmacol Ther 2014; 20:313-21. [PMID: 25389106 DOI: 10.1177/1074248414557036] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/24/2014] [Accepted: 09/23/2014] [Indexed: 01/09/2023]
Abstract
INTRODUCTION Recent clinical studies have reported the potential benefit of an early mineralocorticoid receptor (MR) blockade with potassium canrenoate (PC) on ventricular arrhythmias (VAs) occurrence in patients experiencing an ST-segment elevation myocardial infarction (STEMI). However, most of the electrophysiological properties of PC demonstrated to date have been investigated in normoxic conditions, and therefore, in vitro experiments during an acute myocardial ischemia-reperfusion were lacking. MATERIALS AND METHODS We used rabbit in vitro models and standard microelectrode technique to assess the electrophysiological impact of PC during myocardial ischemia-reperfusion, including right ventricle mimicking the "border zone" existing between normal and ischemic/reperfused areas (1 µmol/L, 10 and 100 nmol/L), isolated right ventricle, and sinoatrial node (SAN) experiments (1 µmol/L, respectively). RESULTS During ischemia-reperfusion, acute superfusion of PC 100 nmol/L prevented the increase in action potential (AP) duration at 90% of repolarization (APD90) dispersion between ischemic and nonischemic areas and in VAs occurrence induced by aldosterone 10 nmol/L (86 ± 3 vs 114 ± 4 milliseconds for aldosterone alone, P < .05). Potassium canrenoate also induced conduction blocks and significantly decreased Vmax during simulated ischemia (from 25 ± 5 to 12 ± 4, 14 ± 3, and 14 ± 5 V/s, respectively, for PC 1 µmol/L, 100, and 10 nmol/L, P < .05). Potassium canrenoate 1 µmol/L demonstrated cycle length (CL)-dependent effects on APD90 and on Vmax, and it also reduced SAN beating CL (from 446 ± 28 to 529 ± 24 millisecond, P < .05). CONCLUSION Our experimental study highlights new evidence for an antiarrhythmic impact of PC during myocardial ischemia-reperfusion via multiple channels modulation. These results are in line with recent clinical trials suggesting that an early MR blockade in STEMI may be preventive of VAs.
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Affiliation(s)
- Joachim Alexandre
- Department of Cardiology, CHU de Caen, Caen, France Université de Caen Basse-Normandie, EA 4650 Signalisation, électrophysiologie et imagerie des lésions d'ischémie-reperfusion myocardique, Caen, France
| | - Farzin Beygui
- Department of Cardiology, CHU de Caen, Caen, France Université de Caen Basse-Normandie, Medical School, Caen, France
| | | | - Alain Manrique
- Université de Caen Basse-Normandie, EA 4650 Signalisation, électrophysiologie et imagerie des lésions d'ischémie-reperfusion myocardique, Caen, France Université de Caen Basse-Normandie, Medical School, Caen, France
| | - René Rouet
- Université de Caen Basse-Normandie, EA 4650 Signalisation, électrophysiologie et imagerie des lésions d'ischémie-reperfusion myocardique, Caen, France Université de Caen Basse-Normandie, Medical School, Caen, France
| | - Paul Milliez
- Department of Cardiology, CHU de Caen, Caen, France Université de Caen Basse-Normandie, EA 4650 Signalisation, électrophysiologie et imagerie des lésions d'ischémie-reperfusion myocardique, Caen, France Université de Caen Basse-Normandie, Medical School, Caen, France
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24
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Ng FS, Holzem KM, Koppel AC, Janks D, Gordon F, Wit AL, Peters NS, Efimov IR. Adverse remodeling of the electrophysiological response to ischemia-reperfusion in human heart failure is associated with remodeling of metabolic gene expression. Circ Arrhythm Electrophysiol 2014; 7:875-82. [PMID: 25114062 DOI: 10.1161/circep.113.001477] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
BACKGROUND Ventricular arrhythmias occur more frequently in heart failure during episodes of ischemia-reperfusion although the mechanisms underlying this in humans are unclear. We assessed, in explanted human hearts, the remodeled electrophysiological response to acute ischemia-reperfusion in heart failure and its potential causes, including the remodeling of metabolic gene expression. METHODS AND RESULTS We optically mapped coronary-perfused left ventricular wedge preparations from 6 human end-stage failing hearts (F) and 6 donor hearts rejected for transplantation (D). Preparations were subjected to 30 minutes of global ischemia, followed by 30 minutes of reperfusion. Failing hearts had exaggerated electrophysiological responses to ischemia-reperfusion, with greater action potential duration shortening (P<0.001 at 8-minute ischemia; P=0.001 at 12-minute ischemia) and greater conduction slowing during ischemia, delayed recovery of electric excitability after reperfusion (F, 4.8±1.8 versus D, 1.0±0 minutes; P<0.05), and incomplete restoration of action potential duration and conduction velocity early after reperfusion. Expression of 46 metabolic genes was probed using custom-designed TaqMan arrays, using extracted RNA from 15 failing and 9 donor hearts. Ten genes important in cardiac metabolism were downregulated in heart failure, with SLC27A4 and KCNJ11 significantly downregulated at a false discovery rate of 0%. CONCLUSIONS We demonstrate, for the first time in human hearts, that the electrophysiological response to ischemia-reperfusion in heart failure is accelerated during ischemia with slower recovery after reperfusion. This can enhance spatial conduction and repolarization gradients across the ischemic border and increase arrhythmia susceptibility. This adverse response was associated with downregulation of expression of cardiac metabolic genes.
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Affiliation(s)
- Fu Siong Ng
- From the Department of Biomedical Engineering, Washington University in Saint Louis, MO (F.S.N., K.M.H., A.C.K., D.J., I.R.E.); National Heart & Lung Institute (F.S.N., N.S.P.) and Statistical Advisory Service (F.G.), Imperial College London, London, United Kingdom; and Department of Pharmacology, Columbia University, New York, NY (A.L.W.)
| | - Katherine M Holzem
- From the Department of Biomedical Engineering, Washington University in Saint Louis, MO (F.S.N., K.M.H., A.C.K., D.J., I.R.E.); National Heart & Lung Institute (F.S.N., N.S.P.) and Statistical Advisory Service (F.G.), Imperial College London, London, United Kingdom; and Department of Pharmacology, Columbia University, New York, NY (A.L.W.)
| | - Aaron C Koppel
- From the Department of Biomedical Engineering, Washington University in Saint Louis, MO (F.S.N., K.M.H., A.C.K., D.J., I.R.E.); National Heart & Lung Institute (F.S.N., N.S.P.) and Statistical Advisory Service (F.G.), Imperial College London, London, United Kingdom; and Department of Pharmacology, Columbia University, New York, NY (A.L.W.)
| | - Deborah Janks
- From the Department of Biomedical Engineering, Washington University in Saint Louis, MO (F.S.N., K.M.H., A.C.K., D.J., I.R.E.); National Heart & Lung Institute (F.S.N., N.S.P.) and Statistical Advisory Service (F.G.), Imperial College London, London, United Kingdom; and Department of Pharmacology, Columbia University, New York, NY (A.L.W.)
| | - Fabiana Gordon
- From the Department of Biomedical Engineering, Washington University in Saint Louis, MO (F.S.N., K.M.H., A.C.K., D.J., I.R.E.); National Heart & Lung Institute (F.S.N., N.S.P.) and Statistical Advisory Service (F.G.), Imperial College London, London, United Kingdom; and Department of Pharmacology, Columbia University, New York, NY (A.L.W.)
| | - Andrew L Wit
- From the Department of Biomedical Engineering, Washington University in Saint Louis, MO (F.S.N., K.M.H., A.C.K., D.J., I.R.E.); National Heart & Lung Institute (F.S.N., N.S.P.) and Statistical Advisory Service (F.G.), Imperial College London, London, United Kingdom; and Department of Pharmacology, Columbia University, New York, NY (A.L.W.)
| | - Nicholas S Peters
- From the Department of Biomedical Engineering, Washington University in Saint Louis, MO (F.S.N., K.M.H., A.C.K., D.J., I.R.E.); National Heart & Lung Institute (F.S.N., N.S.P.) and Statistical Advisory Service (F.G.), Imperial College London, London, United Kingdom; and Department of Pharmacology, Columbia University, New York, NY (A.L.W.)
| | - Igor R Efimov
- From the Department of Biomedical Engineering, Washington University in Saint Louis, MO (F.S.N., K.M.H., A.C.K., D.J., I.R.E.); National Heart & Lung Institute (F.S.N., N.S.P.) and Statistical Advisory Service (F.G.), Imperial College London, London, United Kingdom; and Department of Pharmacology, Columbia University, New York, NY (A.L.W.).
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