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Thavandiran N, Hale C, Blit P, Sandberg ML, McElvain ME, Gagliardi M, Sun B, Witty A, Graham G, Do VTH, Bakooshli MA, Le H, Ostblom J, McEwen S, Chau E, Prowse A, Fernandes I, Norman A, Gilbert PM, Keller G, Tagari P, Xu H, Radisic M, Zandstra PW. Functional arrays of human pluripotent stem cell-derived cardiac microtissues. Sci Rep 2020; 10:6919. [PMID: 32332814 PMCID: PMC7181791 DOI: 10.1038/s41598-020-62955-3] [Citation(s) in RCA: 26] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/01/2019] [Accepted: 03/18/2020] [Indexed: 11/09/2022] Open
Abstract
To accelerate the cardiac drug discovery pipeline, we set out to develop a platform that would be capable of quantifying tissue-level functions such as contractile force and be amenable to standard multiwell-plate manipulations. We report a 96-well-based array of 3D human pluripotent stem cell (hPSC)-derived cardiac microtissues - termed Cardiac MicroRings (CaMiRi) - in custom 3D-print-molded multiwell plates capable of contractile force measurement. Within each well, two elastomeric microcantilevers are situated above a circumferential ramp. The wells are seeded with cell-laden collagen, which, in response to the gradual slope of the circumferential ramp, self-organizes around tip-gated microcantilevers to form contracting CaMiRi. The contractile force exerted by the CaMiRi is measured and calculated using the deflection of the cantilevers. Platform responses were robust and comparable across wells, and we used it to determine an optimal tissue formulation. We validated the contractile force response of CaMiRi using selected cardiotropic compounds with known effects. Additionally, we developed automated protocols for CaMiRi seeding, image acquisition, and analysis to enable the measurement of contractile force with increased throughput. The unique tissue fabrication properties of the platform, and the consequent effects on tissue function, were demonstrated upon adding hPSC-derived epicardial cells to the system. This platform represents an open-source contractile force screening system useful for drug screening and tissue engineering applications.
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Affiliation(s)
- Nimalan Thavandiran
- Institute for Biomaterials and Biomedical Engineering, University of Toronto, Toronto, Ontario, Canada.,Department of Chemical Engineering and Applied Chemistry, University of Toronto, Toronto, Ontario, Canada
| | - Christopher Hale
- Amgen Discovery Research, Amgen Inc., South San Francisco, CA, USA
| | | | | | | | - Mark Gagliardi
- McEwen Centre for Regenerative Medicine, University Health Network, Toronto, Ontario, Canada
| | - Bo Sun
- McEwen Centre for Regenerative Medicine, University Health Network, Toronto, Ontario, Canada
| | - Alec Witty
- McEwen Centre for Regenerative Medicine, University Health Network, Toronto, Ontario, Canada
| | | | | | - Mohsen Afshar Bakooshli
- Institute for Biomaterials and Biomedical Engineering, University of Toronto, Toronto, Ontario, Canada
| | - Hon Le
- Amgen Discovery Research, Amgen Inc., South San Francisco, CA, USA
| | - Joel Ostblom
- Institute for Biomaterials and Biomedical Engineering, University of Toronto, Toronto, Ontario, Canada
| | - Samuel McEwen
- Institute for Biomaterials and Biomedical Engineering, University of Toronto, Toronto, Ontario, Canada
| | - Erik Chau
- Department of Mechanical and Industrial Engineering, University of Toronto, Toronto, Ontario, Canada
| | | | - Ian Fernandes
- McEwen Centre for Regenerative Medicine, University Health Network, Toronto, Ontario, Canada
| | | | - Penney M Gilbert
- Institute for Biomaterials and Biomedical Engineering, University of Toronto, Toronto, Ontario, Canada.,Department of Biochemistry, University of Toronto, Toronto, Ontario, Canada.,Cell and Systems Biology, University of Toronto, Toronto, Ontario, Canada.,Terrence Donnelly Centre for Cellular and Biomolecular Research, University of Toronto, Toronto, Ontario, Canada
| | - Gordon Keller
- McEwen Centre for Regenerative Medicine, University Health Network, Toronto, Ontario, Canada
| | - Philip Tagari
- Amgen Discovery Research, Amgen Inc., South San Francisco, CA, USA
| | - Han Xu
- A2 Biotherapeutics Inc., Agoura Hills, CA, USA.
| | - Milica Radisic
- Institute for Biomaterials and Biomedical Engineering, University of Toronto, Toronto, Ontario, Canada. .,Department of Chemical Engineering and Applied Chemistry, University of Toronto, Toronto, Ontario, Canada. .,Heart and Stroke/Richard Lewar Centre of Excellence, University of Toronto, Toronto, Ontario, Canada.
| | - Peter W Zandstra
- Institute for Biomaterials and Biomedical Engineering, University of Toronto, Toronto, Ontario, Canada. .,CCRM, Toronto, Ontario, Canada. .,Terrence Donnelly Centre for Cellular and Biomolecular Research, University of Toronto, Toronto, Ontario, Canada. .,Michael Smith Laboratories, School of Biomedical Engineering, University of British Columbia, Vancouver, British Columbia, Canada.
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Zhang CL, Chen ZJ, Feng H, Zhao Q, Cao YP, Li L, Wang JY, Zhang Y, Wu LL. C1q/tumor necrosis factor-related protein-3 enhances the contractility of cardiomyocyte by increasing calcium sensitivity. Cell Calcium 2017; 66:90-97. [PMID: 28807153 DOI: 10.1016/j.ceca.2017.06.009] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/09/2017] [Revised: 06/15/2017] [Accepted: 06/25/2017] [Indexed: 01/24/2023]
Abstract
C1q/tumor necrosis factor-related protein-3 (CTRP3) is an adipokine that protects against myocardial infarction-induced cardiac dysfunction through its pro-angiogenic, anti-apoptotic, and anti-fibrotic effects. However, whether CTRP3 can directly affect the systolic and diastolic function of cardiomyocytes remains unknown. Adult rat cardiomyocytes were isolated and loaded with Fura-2AM. The contraction and Ca2+ transient data was collected and analyzed by IonOptix system. 1 and 2μg/ml CTRP3 significantly increased the contraction of cardiomyocytes. However, CTRP3 did not alter the diastolic Ca2+ content, systolic Ca2+ content, Ca2+ transient amplitude, and L-type Ca2+ channel current. To reveal whether CTRP3 affects the Ca2+ sensitivity of cardiomyocytes, the typical phase-plane diagrams of sarcomere length vs. Fura-2 ratio was performed. We observed a left-ward shifting of the late relaxation trajectory after CTRP3 perfusion, as quantified by decreased Ca2+ content at 50% sarcomere relaxation, and increased mean gradient (μm/Fura-2 ratio) during 500-600ms (-0.163 vs. -0.279), 500-700ms (-0.159 vs. -0.248), and 500-800ms (-0.148 vs. -0.243). Consistently, the phosphorylation level of cardiac troponin I at Ser23/24 was reduced by CTRP3, which could be eliminated by preincubation of okadaic acid, a type 2A protein phosphatase inhibitor. In summary, CTRP3 increases the contraction of cardiomyocytes by increasing the myofilament Ca2+ sensitivity. CTRP3 might be a potential endogenous Ca2+ sensitizer that modulates the contractility of cardiomyocytes.
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Affiliation(s)
- Cheng-Lin Zhang
- Department of Physiology and Pathophysiology, Peking University School of Basic Medical Sciences, Key Laboratory of Molecular Cardiovascular Science, Ministry of Education, and Beijing Key Laboratory of Cardiovascular Receptors Research, Beijing 100191, China
| | - Zheng-Ju Chen
- State Key Laboratory of Membrane Biology, College of Life Sciences, Peking University, Beijing 100871, China
| | - Han Feng
- Department of Physiology and Pathophysiology, Peking University School of Basic Medical Sciences, Key Laboratory of Molecular Cardiovascular Science, Ministry of Education, and Beijing Key Laboratory of Cardiovascular Receptors Research, Beijing 100191, China
| | - Qian Zhao
- Department of Physiology and Pathophysiology, Peking University School of Basic Medical Sciences, Key Laboratory of Molecular Cardiovascular Science, Ministry of Education, and Beijing Key Laboratory of Cardiovascular Receptors Research, Beijing 100191, China
| | - Yang-Po Cao
- Department of Physiology and Pathophysiology, Peking University School of Basic Medical Sciences, Key Laboratory of Molecular Cardiovascular Science, Ministry of Education, and Beijing Key Laboratory of Cardiovascular Receptors Research, Beijing 100191, China
| | - Li Li
- Department of Physiology and Pathophysiology, Peking University School of Basic Medical Sciences, Key Laboratory of Molecular Cardiovascular Science, Ministry of Education, and Beijing Key Laboratory of Cardiovascular Receptors Research, Beijing 100191, China
| | - Jin-Yu Wang
- Department of Physiology and Pathophysiology, Peking University School of Basic Medical Sciences, Key Laboratory of Molecular Cardiovascular Science, Ministry of Education, and Beijing Key Laboratory of Cardiovascular Receptors Research, Beijing 100191, China
| | - Yan Zhang
- Department of Physiology and Pathophysiology, Peking University School of Basic Medical Sciences, Key Laboratory of Molecular Cardiovascular Science, Ministry of Education, and Beijing Key Laboratory of Cardiovascular Receptors Research, Beijing 100191, China.
| | - Li-Ling Wu
- Department of Physiology and Pathophysiology, Peking University School of Basic Medical Sciences, Key Laboratory of Molecular Cardiovascular Science, Ministry of Education, and Beijing Key Laboratory of Cardiovascular Receptors Research, Beijing 100191, China.
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Turnbull IC, Karakikes I, Serrao GW, Backeris P, Lee JJ, Xie C, Senyei G, Gordon RE, Li RA, Akar FG, Hajjar RJ, Hulot JS, Costa KD. Advancing functional engineered cardiac tissues toward a preclinical model of human myocardium. FASEB J 2013; 28:644-54. [PMID: 24174427 DOI: 10.1096/fj.13-228007] [Citation(s) in RCA: 122] [Impact Index Per Article: 11.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
Abstract
Cardiac experimental biology and translational research would benefit from an in vitro surrogate for human heart muscle. This study investigated structural and functional properties and interventional responses of human engineered cardiac tissues (hECTs) compared to human myocardium. Human embryonic stem cell-derived cardiomyocytes (hESC-CMs, >90% troponin-positive) were mixed with collagen and cultured on force-sensing elastomer devices. hECTs resembled trabecular muscle and beat spontaneously (1.18 ± 0.48 Hz). Microstructural features and mRNA expression of cardiac-specific genes (α-MHC, SERCA2a, and ACTC1) were comparable to human myocardium. Optical mapping revealed cardiac refractoriness with loss of 1:1 capture above 3 Hz, and cycle length dependence of the action potential duration, recapitulating key features of cardiac electrophysiology. hECTs reconstituted the Frank-Starling mechanism, generating an average maximum twitch stress of 660 μN/mm(2) at Lmax, approaching values in newborn human myocardium. Dose-response curves followed exponential pharmacodynamics models for calcium chloride (EC50 1.8 mM) and verapamil (IC50 0.61 μM); isoproterenol elicited a positive chronotropic but negligible inotropic response, suggesting sarcoplasmic reticulum immaturity. hECTs were amenable to gene transfer, demonstrated by successful transduction with Ad.GFP. Such 3-D hECTs recapitulate an early developmental stage of human myocardium and promise to offer an alternative preclinical model for cardiology research.
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Affiliation(s)
- Irene C Turnbull
- 2Cardiovascular Cell and Tissue Engineering Laboratory, Cardiovascular Research Center, Icahn School of Medicine at Mt. Sinai, One Gustave L. Levy Pl., P.O. Box 1030, New York, NY 10029, USA.
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Sauler M, Fares WH, Trow TK. Standard nonspecific therapies in the management of pulmonary arterial hypertension. Clin Chest Med 2013; 34:799-810. [PMID: 24267305 DOI: 10.1016/j.ccm.2013.08.013] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
Abstract
Recent advances in pulmonary arterial hypertension (PAH) research have created a new era of PAH-specific therapies. Although these therapeutics have revolutionized PAH therapy, their innovation was predated by supportive but nonspecific medical therapies adapted from their use in more common cardiopulmonary diseases. These therapies include oxygen therapy, diuretics, digoxin, anticoagulation, and high-dose calcium channel blockers. Expert opinion continues to support the use of adjunct therapies based on current pathologic understandings of PAH combined with some evidence extrapolated from small studies. This article discusses why these therapies continue to play an important role in the treatment of patients with PAH.
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Affiliation(s)
- Maor Sauler
- Section of Pulmonary, Critical Care, & Sleep Medicine, Department of Internal Medicine, Yale University School of Medicine, 333 Cedar Street, PO Box 208057, New Haven, CT 06520-8057, USA
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Menick DR, Li MS, Chernysh O, Renaud L, Kimbrough D, Kasiganesan H, Mani SK. Transcriptional pathways and potential therapeutic targets in the regulation of Ncx1 expression in cardiac hypertrophy and failure. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2013; 961:125-35. [PMID: 23224875 PMCID: PMC3624972 DOI: 10.1007/978-1-4614-4756-6_11] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/21/2023]
Abstract
Changes in cardiac gene expression contribute to the progression of heart failure by affecting cardiomyocyte growth, function, and survival. The Na(+)-Ca(2+) exchanger gene (Ncx1) is upregulated in hypertrophy and is often found elevated in end-stage heart failure. Studies have shown that the change in its expression contributes to contractile dysfunction. Several transcriptional pathways mediate Ncx1 expression in pathological cardiac remodeling. Both α-adrenergic receptor (α-AR) and β-adrenergic receptor (β-AR) signaling can play a role in the regulation of calcium homeostasis in the cardiomyocyte, but chronic activation in periods of cardiac stress contributes to heart failure by mechanisms which include Ncx1 upregulation. Our studies have even demonstrated that NCX1 can directly act as a regulator of "activity-dependent signal transduction" mediating changes in its own expression. Finally, we present evidence that histone deacetylases (HDACs) and histone acetyltransferases (HATs) act as master regulators of Ncx1 expression. We show that many of the transcription factors regulating Ncx1 expression are important in cardiac development and also in the regulation of many other genes in the so-called fetal gene program, which are activated by pathological stimuli. Importantly, studies have revealed that the transcriptional network regulating Ncx1 expression is also mediating many of the other changes in genetic remodeling contributing to the development of cardiac dysfunction and revealed potential therapeutic targets for the treatment of hypertrophy and failure.
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Abstract
β-adrenergic receptor (βAR) stimulation by the sympathetic nervous system or circulating catecholamines is broadly involved in peripheral blood circulation, metabolic regulation, muscle contraction, and central neural activities. In the heart, acute βAR stimulation serves as the most powerful means to regulate cardiac output in response to a fight-or-flight situation, whereas chronic βAR stimulation plays an important role in physiological and pathological cardiac remodeling.There are three βAR subtypes, β(1)AR, β(2)AR and β(3)AR, in cardiac myocytes. Over the past two decades, we systematically investigated the molecular and cellular mechanisms underlying the different even opposite functional roles of β(1)AR and β(2)AR subtypes in regulating cardiac structure and function, with keen interest in the development of novel therapies based on our discoveries. We have made three major discoveries, including (1) dual coupling of β(2)AR to G(s) and G(i) proteins in cardiomyocytes, (2) cardioprotection by β(2)AR signaling in improving cardiac function and myocyte viability, and (3) PKA-independent, CaMKII-mediated β(1)AR apoptotic and maladaptive remodeling signaling in the heart. Based on these discoveries and salutary effects of β(1)AR blockade on patients with heart failure, we envision that activation of β(2)AR in combination with clinically used β(1)AR blockade should provide a safer and more effective therapy for the treatment of heart failure.
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Decreased contractility due to energy deprivation in a transgenic rat model of hypertrophic cardiomyopathy. J Mol Med (Berl) 2009; 87:411-22. [PMID: 19189074 DOI: 10.1007/s00109-008-0436-x] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/17/2008] [Revised: 11/18/2008] [Accepted: 12/10/2008] [Indexed: 12/13/2022]
Abstract
Hypertrophic cardiomyopathy (HCM) is associated with cardiac hypertrophy, diastolic dysfunction, and sudden death. Recently, it has been suggested that inefficient energy utilization could be a common molecular pathway of HCM-related mutations. We have previously generated transgenic Sprague-Dawley rats overexpressing a truncated cardiac troponin T (DEL-TNT) molecule, displaying typical features of HCM such as diastolic dysfunction and an increased susceptibility to ventricular arrhythmias. We now studied these rats using 31P magnetic resonance spectroscopy (MRS). MRS demonstrated that cardiac energy metabolism was markedly impaired, as indicated by a decreased phosphocreatine to ATP ratio (-31%, p < 0.05). In addition, we assessed contractility of isolated cardiomyocytes. While DEL-TNT and control cardiomyocytes showed no difference under baseline conditions, DEL-TNT cardiomyocytes selectively exhibited a decrease in fractional shortening by 28% after 1 h in glucose-deprived medium (p < 0.05). Moreover, significant decreases in contraction velocity and relaxation velocity were observed. To identify the underlying molecular pathways, we performed transcriptional profiling using real-time PCR. DEL-TNT hearts exhibited induction of several genes critical for cardiac energy supply, including CD36, CPT-1/-2, and PGC-1alpha. Finally, DEL-TNT rats and controls were studied by radiotelemetry after being stressed by isoproterenol, revealing a significantly increased frequency of arrhythmias in transgenic animals. In summary, we demonstrate profound energetic alterations in DEL-TNT hearts, supporting the notion that inefficient cellular ATP utilization contributes to the pathogenesis of HCM.
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Maack C, O'Rourke B. Excitation-contraction coupling and mitochondrial energetics. Basic Res Cardiol 2007; 102:369-92. [PMID: 17657400 PMCID: PMC2785083 DOI: 10.1007/s00395-007-0666-z] [Citation(s) in RCA: 186] [Impact Index Per Article: 10.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/22/2007] [Revised: 06/12/2007] [Accepted: 06/13/2007] [Indexed: 12/20/2022]
Abstract
Cardiac excitation-contraction (EC) coupling consumes vast amounts of cellular energy, most of which is produced in mitochondria by oxidative phosphorylation. In order to adapt the constantly varying workload of the heart to energy supply, tight coupling mechanisms are essential to maintain cellular pools of ATP, phosphocreatine and NADH. To our current knowledge, the most important regulators of oxidative phosphorylation are ADP, Pi, and Ca2+. However, the kinetics of mitochondrial Ca2+-uptake during EC coupling are currently a matter of intense debate. Recent experimental findings suggest the existence of a mitochondrial Ca2+ microdomain in cardiac myocytes, justified by the close proximity of mitochondria to the sites of cellular Ca2+ release, i. e., the ryanodine receptors of the sarcoplasmic reticulum. Such a Ca2+ microdomain could explain seemingly controversial results on mitochondrial Ca2+ uptake kinetics in isolated mitochondria versus whole cardiac myocytes. Another important consideration is that rapid mitochondrial Ca2+ uptake facilitated by microdomains may shape cytosolic Ca2+ signals in cardiac myocytes and have an impact on energy supply and demand matching. Defects in EC coupling in chronic heart failure may adversely affect mitochondrial Ca2+ uptake and energetics, initiating a vicious cycle of contractile dysfunction and energy depletion. Future therapeutic approaches in the treatment of heart failure could be aimed at interrupting this vicious cycle.
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Affiliation(s)
- Christoph Maack
- Klinik für Innere Medizin III, Universitätsklinikum des Saarlandes, 66421, Homburg/Saar, Germany.
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Kang M, Chung KY, Walker JW. G-protein coupled receptor signaling in myocardium: not for the faint of heart. Physiology (Bethesda) 2007; 22:174-84. [PMID: 17557938 DOI: 10.1152/physiol.00051.2006] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023] Open
Abstract
Catecholamines, endothelin-1 and angiotensin II are among a diverse group of diffusible extracellular signals that regulate pump function of the heart by binding to G-protein coupled receptors (GPCR). When the body demands a temporary boost of power output or if temporary budgeting of resources is required, these signals can adjust heart rate and contractile strength to maintain continuous perfusion of all vascular beds with nutrient- and oxygen-rich blood. Given adequate time in the face of prolonged challenges, activation of GPCRs can also promote "remodeling of the heart" by increasing cell size, organ size, and chamber dimensions, or by varying tissue composition and altering the expression of protein isoforms controlling excitability and contractility. A common feature of heart disease is the state of chronic activation of GPCR signaling systems. Paradoxically, whereas acute activation is beneficial, chronic activation often contributes to further deterioration of cardiac performance. A better understanding of how chronic GPCR activation contributes to the development of heart disease is needed so that it can be translated into better prevention and therapeutic strategies in the clinic.
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Affiliation(s)
- Misuk Kang
- Department of Physiology, University of Wisconsin School of Medicine, Madison, Wisconsin, USA
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Keweloh B, Janssen PML, Siegel U, Datz N, Zeitz O, Hermann HP. Influence of pyruvate on economy of contraction in isolated rabbit myocardium. Eur J Heart Fail 2007; 9:754-61. [PMID: 17532261 DOI: 10.1016/j.ejheart.2007.03.011] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/30/2006] [Revised: 01/31/2007] [Accepted: 03/08/2007] [Indexed: 11/17/2022] Open
Abstract
BACKGROUND Treatment of acute heart failure frequently requires positive-inotropic stimulation. However, there is still no inotropic agent available, which combines a favourable haemodynamic profile with low expenditure for energy metabolism. Pyruvate exhibits positive inotropic effects in vitro and in patients with heart failure. The effect on myocardial energy metabolism however remains unclear, but is meaningful in light of a clinical application. AIMS AND METHODS We investigated the influence of pyruvate on contractility and oxygen consumption in isolated isometric contracting rabbit myocardium compared to beta-adrenergic stimulation with isoproterenol. RESULTS Pyruvate (30 mM) increased developed force from 18.7+/-4.1 to 50.8+/-12.1 mN/mm2 (n=10, p<0.01). Force-time integral (FTI) increased by 329%, oxygen consumption assessed by diffusion-microelectrode technique increased from 2.86+/-0.30 mlO2/min*100 g to 6.28+/-1.28 mlO2/min*100 g (n=7, p<0.05). Economy of myocardial contraction calculated as the ratio of total FTI to oxygen consumption remained unchanged. In contrast, while isoproterenol (10 microM) produced a comparable increase in developed force from 21.4+/-8.3 to 67.3+/-15 mN/mm2 (n=7, p<0.01), FTI increased only by 260% and MVO2 increased from 2.96+/-0.43 to 6.12+/-1.01 mlO2/min*100 g (n=7, p<0.01); thus, economy decreased by 23% (n=7, p<0.05). CONCLUSION Pyruvate does not impair economy of myocardial contraction while isoproterenol decreases economy. Regarding energy expenditure, pyruvate appears superior to isoproterenol for the purpose of positive inotropic stimulation.
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Affiliation(s)
- Boris Keweloh
- Franz-Volhard-Klinik, Universitätsklinikum Charité, Berlin, Germany
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Busk M, Maeng M, Kristensen J, Berg JS, Mortensen UM, Nielsen TT, Nielsen-Kudsk JE. Effects of levosimendan on myocardial infarct size and hemodynamics in a closed-chest porcine ischemia-reperfusion model. Cardiovasc Drugs Ther 2007; 20:335-42. [PMID: 17122904 DOI: 10.1007/s10557-006-0294-0] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
INTRODUCTION Levosimendan is a positive inotropic drug with vasodilator action and proposed myocardioprotective properties. In a canine model, levosimendan increased coronary collateral flow and reduced myocardial infarct size (IS). We investigated the effect of levosimendan on IS and hemodynamics in the closed-chest porcine ischemia-reperfusion model, which is devoid of coronary collaterals. METHODS Infusion with levosimendan (0.2 microg/kg/min following a bolus of 24 microg/kg) or saline was initiated 30 min prior to ischemia in anaesthetized pigs (n = 10 in both groups). Balloon occlusion of the left anterior descending coronary artery for 45 min was followed by 2 1/2 h of reperfusion. Hemodynamics were monitored with a Swan-Ganz catheter and a left ventricular pressure micromanometer. Left ventricular systolic and diastolic function was estimated by dP/dt(max) and tau, respectively. Myocardial area at risk (AAR) and IS were assessed in vivo by myocardial perfusion imaging (MPI) and ex vivo by histopathology (fluorescein staining for AAR, tetrazolium staining for IS). RESULTS Prior to ischemia, levosimendan improved left ventricular systolic and diastolic function with coincident preload and afterload reduction. Cardiac output increased by 10 +/- 4% (p = 0.04), dP/dt(max) by 15 +/- 5% (p = 0.01). Pulmonary capillary wedge pressure decreased by 18 +/- 3% (p = 0.04), tau by 11 +/- 2% (p = 0.001), and mean arterial pressure by 11 +/- 2% (p < 0.001). A similar trend was observed during ischemia-reperfusion. The ratio of IS/AAR was not reduced by levosimendan compared to saline as evaluated by histopathology (76 +/- 4% vs. 64 +/- 7%, p = 0.12) and by MPI (94 +/- 2% vs. 87 +/- 5%, p = 0.14). CONCLUSION Levosimendan improves hemodynamics but does not reduce IS in an ischemia-reperfusion model without coronary collaterals.
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Affiliation(s)
- Martin Busk
- Department of Cardiology B, Research Unit, Skejby Sygehus, Aarhus University Hospital, Brendstrupgaardsvej 100, Aarhus, Denmark.
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Rhodes SS, Camara AKS, Ropella KM, Audi SH, Riess ML, Pagel PS, Stowe DF. Ischemia reperfusion dysfunction changes model-estimated kinetics of myofilament interaction due to inotropic drugs in isolated hearts. Biomed Eng Online 2006; 5:16. [PMID: 16512898 PMCID: PMC1431537 DOI: 10.1186/1475-925x-5-16] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/09/2005] [Accepted: 03/02/2006] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND The phase-space relationship between simultaneously measured myoplasmic [Ca2+] and isovolumetric left ventricular pressure (LVP) in guinea pig intact hearts is altered by ischemic and inotropic interventions. Our objective was to mathematically model this phase-space relationship between [Ca2+] and LVP with a focus on the changes in cross-bridge kinetics and myofilament Ca2+ sensitivity responsible for alterations in Ca2+-contraction coupling due to inotropic drugs in the presence and absence of ischemia reperfusion (IR) injury. METHODS We used a four state computational model to predict LVP using experimentally measured, averaged myoplasmic [Ca2+] transients from unpaced, isolated guinea pig hearts as the model input. Values of model parameters were estimated by minimizing the error between experimentally measured LVP and model-predicted LVP. RESULTS We found that IR injury resulted in reduced myofilament Ca2+ sensitivity, and decreased cross-bridge association and dissociation rates. Dopamine (8 microM) reduced myofilament Ca2+ sensitivity before, but enhanced it after ischemia while improving cross-bridge kinetics before and after IR injury. Dobutamine (4 microM) reduced myofilament Ca2+ sensitivity while improving cross-bridge kinetics before and after ischemia. Digoxin (1 microM) increased myofilament Ca2+ sensitivity and cross-bridge kinetics after but not before ischemia. Levosimendan (1 microM) enhanced myofilament Ca2+ affinity and cross-bridge kinetics only after ischemia. CONCLUSION Estimated model parameters reveal mechanistic changes in Ca2+-contraction coupling due to IR injury, specifically the inefficient utilization of Ca2+ for contractile function with diastolic contracture (increase in resting diastolic LVP). The model parameters also reveal drug-induced improvements in Ca2+-contraction coupling before and after IR injury.
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Affiliation(s)
- Samhita S Rhodes
- Department of Anesthesiology, Medical College of Wisconsin, 8701 Watertown Plank Road, Milwaukee, WI 53226, USA
| | - Amadou KS Camara
- Department of Anesthesiology, Medical College of Wisconsin, 8701 Watertown Plank Road, Milwaukee, WI 53226, USA
| | - Kristina M Ropella
- Department of Biomedical Engineering, Marquette University, 1515 W Wisconsin Ave, Milwaukee, WI 53233, USA
| | - Said H Audi
- Department of Pulmonary Medicine and Critical Care, Medical College of Wisconsin, 8701 Watertown Plank Road, Milwaukee, WI 53226, USA
- Department of Biomedical Engineering, Marquette University, 1515 W Wisconsin Ave, Milwaukee, WI 53233, USA
- VA Medical Center, Milwaukee, WI 53295, USA
| | - Matthias L Riess
- Department of Anesthesiology, Medical College of Wisconsin, 8701 Watertown Plank Road, Milwaukee, WI 53226, USA
- Department of Physiology, Medical College of Wisconsin, 8701 Watertown Plank Road, Milwaukee, WI 53226, USA
| | - Paul S Pagel
- Department of Anesthesiology, Medical College of Wisconsin, 8701 Watertown Plank Road, Milwaukee, WI 53226, USA
- Department of Biomedical Engineering, Marquette University, 1515 W Wisconsin Ave, Milwaukee, WI 53233, USA
- VA Medical Center, Milwaukee, WI 53295, USA
| | - David F Stowe
- Department of Anesthesiology, Medical College of Wisconsin, 8701 Watertown Plank Road, Milwaukee, WI 53226, USA
- Department of Physiology, Medical College of Wisconsin, 8701 Watertown Plank Road, Milwaukee, WI 53226, USA
- Cardiovascular Research Center, Medical College of Wisconsin, 8701 Watertown Plank Road, Milwaukee, WI 53226, USA
- Department of Biomedical Engineering, Marquette University, 1515 W Wisconsin Ave, Milwaukee, WI 53233, USA
- VA Medical Center, Milwaukee, WI 53295, USA
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Montgomery DE, Rundell VLM, Goldspink PH, Urboniene D, Geenen DL, de Tombe PP, Buttrick PM. Protein kinase C epsilon induces systolic cardiac failure marked by exhausted inotropic reserve and intact Frank-Starling mechanism. Am J Physiol Heart Circ Physiol 2005; 289:H1881-8. [PMID: 15951344 DOI: 10.1152/ajpheart.00454.2005] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Myofilament dysfunction is a common point of convergence for many forms of heart failure. Recently, we showed that cardiac overexpression of PKC epsilon initially depresses myofilament activity and then leads to a progression of changes characteristic of human heart failure. Here, we examined the effects of PKC epsilon on contractile reserve, Starling mechanism, and myofilament activation in this model of end-stage dilated cardiomyopathy. Pressure-volume loop analysis and echocardiography showed that the PKC epsilon mice have markedly compromised systolic function and increased end-diastolic volumes. Dobutamine challenge resulted in a small increase in contractility in PKC epsilon mice but failed to enhance cardiac output. The PKC epsilon mice showed a normal length-dependent tension development in skinned cardiac muscle preparations, although Frank-Starling mechanism appeared to be compromised in the intact animal. Simultaneous measurement of tension and ATPase demonstrated that the maximum tension and ATPase were markedly lower in the PKC epsilon mice at any length or Ca2+ concentration. However, the tension cost was also lower indicating less energy expenditure. We conclude 1) that prolonged overexpression of PKC epsilon ultimately leads to a dilated cardiomyopathy marked by exhausted contractile reserve, 2) that PKC epsilon does not compromise the Frank-Starling mechanism at the myofilament level, and 3) that the Starling curve excursion is limited by the inotropic state of the heart. These results reflect the significance of the primary myofilament contractilopathy induced by phosphorylation and imply a role for PKC epsilon-mediated phosphorylation in myofilament physiology and the pathophysiology of decompensated cardiac failure.
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Affiliation(s)
- David E Montgomery
- Department of Medicine, Section of Cardiology, Univ. of Illinois at Chicago, College of Medicine, Chicago, IL 60612, USA
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15
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Nassar R, Malouf NN, Mao L, Rockman HA, Oakeley AE, Frye JR, Herlong JR, Sanders SP, Anderson PAW. cTnT1, a cardiac troponin T isoform, decreases myofilament tension and affects the left ventricular pressure waveform. Am J Physiol Heart Circ Physiol 2004; 288:H1147-56. [PMID: 15513965 DOI: 10.1152/ajpheart.00140.2004] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Four isoforms of cardiac troponin T (cTnT), a protein essential for calcium-dependent myocardial force development, are expressed in the human; they differ in charge and length. Their expression is regulated developmentally and is affected by disease states. Human cTnT (hcTnT) isoform effects have been examined in reconstituted myofilaments. In this study, we evaluated the modulatory effects of overexpressing one cTnT isoform on in vitro and in vivo myocardial function. A hcTnT isoform, hcTnT(1), expressed during development and in heart disease but not in the normal adult heart, was expressed in transgenic (TG) mice (1-30% of total cTnT). Maximal active tension measured in skinned myocardium decreased as a function of relative hcTnT(1) expression. The pCa at half-maximal force development, Hill coefficient, and rate of redevelopment of force did not change significantly with hcTnT(1) expression. In vivo maximum rates of rise and fall of left ventricular pressure decreased, and the half-time of isovolumic relaxation increased, with hcTnT(1) expression. Substituting total cTnT charge for hcTnT(1) expression resulted in similar conclusions. Morphometric analysis and electron microscopy revealed no differences between wild-type (non-TG) and TG myocardium. No differences in isoform expression of tropomyosin, myosin heavy chain, essential and regulatory myosin light chains (MLC), TnI, or in posttranslational modifications of mouse cTnT, cTnI, or regulatory MLC were observed. These results support the hypothesis that cTnT isoform amino-terminal differences affect myofilament function and suggest that hcTnT(1) expression levels present during human development and in human heart disease can affect in vivo ventricular function.
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Affiliation(s)
- Rashid Nassar
- Department of Pediatrics, Duke University, Durham, NC, USA
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16
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Savio-Galimberti E, Dos Santos Costa P, Campos De Carvalho AC, Ponce-Hornos JE. Mechanical and energetic effects of chronic chagasic patients' antibodies on rat myocardium. Am J Physiol Heart Circ Physiol 2004; 287:H1239-45. [PMID: 15155265 DOI: 10.1152/ajpheart.01155.2003] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
Abstract
Chagasic (Ch) and nonchagasic (NCh) IgG fraction (20 microg/ml) effects on cardiac performance of adult Wistar rat ventricles were studied with a novel approach applying a microcalorimetric technique. Resting heat (Hr) was significantly decreased by Ch antibodies (DeltaHrCh = 4.8 +/- 0.9 mW/g). Although the Hr decrease can be associated with diminished activity of the Na+/K+ pump, the magnitude of the effect (25% of control Hr) indicates that additional processes may also be affected. Ch antibodies induced an initial increase in developed pressure (P), which was associated with a decreased contractile economy. However, after 30 min of Ch antibody perfusion, P reached a significantly lower level (DeltaPCh = 3.8 +/- 1.2 mN/mm2) without changes in active heat per beat (Ha'). Consequently, Ha'/P ratio increased, indicating that the energetic cost per unit of P was higher. In contrast, P and Ha' were both significantly and reversibly decreased by NCh antibodies (DeltaPNCh = 4.4 +/- 1.2 mN/mm2; DeltaHa'NCh = 9.7 +/- 2.2 mJ/g), but Ha'/P remained unaffected. According to these data, normal hearts exposed to Ch antibodies present a biphasic mechanical response: 1) an initial period of increased contractility (and decreased global muscle economy) consistent with antibodies with beta1-adrenergic activity, such as those used in the present study, and 2) a decrease in P at 30 min of Ch antibody perfusion, which suggests that another Ca(2+)-related mechanism is compromised. These data contribute to redefine the role of antibody-mediated responses in the pathophysiology of chronic chagasic cardiomyopathy as agents of myocardial failure.
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Affiliation(s)
- Eleonora Savio-Galimberti
- Instituto de Investigaciones Cardiológicas, School of Medicine (Universidad de Buenos Aires-Consejo Nacional de Investigaciones Cientificas y Técnicas), Buenos Aires, Argentina.
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17
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Hermann HP, Arp J, Pieske B, Kögler H, Baron S, Janssen PML, Hasenfuss G. Improved systolic and diastolic myocardial function with intracoronary pyruvate in patients with congestive heart failure. Eur J Heart Fail 2004; 6:213-8. [PMID: 14984729 DOI: 10.1016/j.ejheart.2003.10.001] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/07/2003] [Revised: 06/25/2003] [Accepted: 10/01/2003] [Indexed: 11/24/2022] Open
Abstract
BACKGROUND Pyruvate increases myocardial performance in isolated myocardium and improves hemodynamics in patients with congestive heart failure. AIMS To investigate the influence of pyruvate on detailed parameters of systolic and diastolic left ventricular (LV) function. METHODS AND RESULTS In patients with heart failure due to dilated cardiomyopathy (LVEF 30+/-4%, n=9) pyruvate was infused intracoronarily. LV function was analysed before, during and after application of different pyruvate concentrations using a LV-micromanometer catheter. LV volumes were determined using cine ventriculography. Pyruvate increased maximum rate of LV isovolumic pressure rise (Peak +dP/dt) from 802+/-106 to 1125+/-103 mmHg/s (P<0.05). Left ventricular end-diastolic pressure declined in parallel from 17+/-2 to 12+/-2 mmHg (P<0.05) and heart rate decreased from 79+/-4 to 72+/-5 min(-1) (P<0.05). Stroke volume index increased from 34+/-4 to 43+/-6 ml/m(2) (P<0.05), end-diastolic LV volume remained unchanged, thus left ventricular ejection fraction increased with pyruvate from 30+/-4 to 39+/-4% (P<0.05). Maximum rate of LV isovolumic pressure decline (Peak -dP/dt) was significantly increased with pyruvate (from 794+/-94 to 980+/-108 mmHg/s; P<0.05) and mean arterial pressure increased from 80+/-5 to 88+/-4 mmHg (P<0.05). Discontinuation of pyruvate resulted in immediate reversibility of its effects. CONCLUSION Intracoronary pyruvate improves systolic and diastolic myocardial function and increases ejection fraction without increasing heart rate. Pyruvate thus exhibits the profile of a favourable inotropic agent, however, further investigation for the treatment of patients with acute heart failure is mandatory.
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Affiliation(s)
- Hans-Peter Hermann
- Abteilung Kardiologie und Pneumologie, Georg-August-Universität Göttingen, Robert-Koch-Str. 40, Göttingen D-37075, Germany.
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18
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Schiffmann H, Rizouli V, Luers F, Hackmann F, Hoebel D, Pfahlberg A, Hellige G. Na(+)-channel modulation, a new principle of inotropic intervention: effects on hemodynamic and myocardial energetics in the immature rabbit heart. Pediatr Res 2003; 54:875-84. [PMID: 12930905 DOI: 10.1203/01.pdr.0000091286.21994.e5] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
Na+-channel modulators exert their positive inotropic action without affecting the adenylate-cyclase pathway by an increase in the open probability of the sarcolemmal Na+ channels. Although inotropic effects in neonatal hearts are less pronounced compared with adult hearts, the Na+-channel modulator BDF 9148 increases contractility and relaxation velocity in immature myocardium. Effects on hemodynamics and myocardial energetics are not known. Therefore, we studied the Na+-channel modulator BDF 9148 in isolated antegrade perfused rabbit hearts of different ages (2-28 d) and compared the effects with isoproterenol, enoximone, and ouabain. ANOVA showed significant effects in the concentration response curves for heart rate, stroke volume, cardiac output, and oxygen consumption but not for myocardial efficiency (p = 0.06). Age-dependent differences were observed for heart rate and stroke volume. Administration of BDF 9148 resulted in a maximal increase in stroke volume and cardiac output up to 25% in neonatal and 40% to 60% in adult preparations. Heart rate decreased by 15% in adult hearts only. Myocardial oxygen consumption was increased in a concentration-dependent manner between 25% in neonatal and 50% in adult hearts. Myocardial efficiency was increased by 35% in adult and by 10% in neonatal preparations. Although positive hemodynamic and energetic effects were less pronounced in immature compared with adult hearts, neonatal hearts also profited from the administration of the Na+-channel modulator BDF 9148. Further studies are necessary to clarify the risk of arrhythmia during application of Na+-channel modulators such as BDF 9148.
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Affiliation(s)
- Holger Schiffmann
- Department of Pediatric Cardiology and Intensive Care, University of Goettingen, Goettingen D-37075, Germany.
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19
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Abstract
Despite the introduction of a variety of new classes of drugs for the management of heart failure, digoxin continues to have an important role in long-term outpatient management. A wide variety of placebo-controlled clinical trials have unequivocally shown that treatment with digoxin can improve symptoms, quality of life, and exercise tolerance in patients with mild, moderate, or severe heart failure. These benefits are evident regardless of the underlying rhythm (normal sinus rhythm or atrial fibrillation), etiology of the heart failure, or concomitant therapy (eg. ACE inhibitors). Unlike other agents with positive inotropic properties, digoxin does not increase all-cause mortality and has a substantial benefit in reducing heart failure hospitalizations. Consensus guidelines have recently been published by the Heart Failure Society of America and the American College of Cardiology/American Heart Association, and they contain the following recommendations for digoxin treatment: 1. Digoxin should be considered for the outpatient treatment of all patients who have persistent symptoms of heart failure (NYHA class II-IV) despite conventional pharmacologic therapy with diuretics, ACE inhibitors, and a beta-blocker when the heart failure is caused by systolic dysfunction (the strength of evidence = A for NYHA class II and III; strength of evidence = C for NYHA class IV). 2. Digoxin is not indicated as primary treatment for the stabilization of patients with acutely decompensated heart failure. (Strength of evidence = B). Digoxin may be initiated after emergent treatment of heart failure has been completed in an effort to establish a long-term treatment strategy. 3. Digoxin should not be administered to patients who have significant sinus or atrioventricular block, unless the block has been treated with a permanent pacemaker (strength of evidence = B). The drug should be used cautiously in patients who receive other agents known to depress sinus or atrioventricular nodal function (such as amiodarone or a beta-blocker) (strength of evidence = B). 4. The dosage of digoxin should be 0.125-0.25 mg daily in the majority of patients (strength of evidence = C). The lower dose should be used in patients over 70 years of age, those with impaired renal function, or those with a low lean body mass. Higher doses (eg, digoxin 0.375-0.50 mg daily) are rarely needed. Loading doses of digoxin are not necessary during initiation of therapy for patients with chronic heart failure. 5. Serial assessment of serum digoxin levels is unnecessary in most patients. The radioimmunoassay was developed to assist in the evaluation of toxicity, not the efficacy of the drug. There appears to be little relationship between serum digoxin concentration and the drug's therapeutic effects. 6. Digoxin toxicity is commonly associated with serum levels >2 ng/mL but may occur with lower digoxin levels if hypokalemia, hypomagnesemia, or hypothyroidism coexist. Likewise, the concomitant use of agents such as quinidine, verapamil, spironolactone, flecainide, and amiodarone can increase serum digoxin levels and increase the likelihood of digoxin toxicity. 7. For patients with heart failure and atrial fibrillation with a rapid ventricular response, the administration of high doses of digoxin (>0.25 mg daily) for the purpose of rate control is not recommended. When necessary, additional rate control should be achieved by the addition of beta-blocker therapy or amiodarone (strength of evidence = C). If amiodarone is added, the dose of digoxin should be reduced. Digitalis preparations are now entering their fourth century of clinical use for the treatment of chronic heart failure symptoms. Its clinical efficacy can no longer be doubted and its safety has been verified by the multicenter DIG trial. Future advances in pharmacogenetics should facilitate identification of those patients most likely to benefit from its pharmacologic effects.
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Affiliation(s)
- G William Dec
- Heart Failure and Transplantation Unit, Massachusetts General Hospital, Boston, MA 02114, USA.
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20
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Reiken S, Gaburjakova M, Guatimosim S, Gomez AM, D'Armiento J, Burkhoff D, Wang J, Vassort G, Lederer WJ, Marks AR. Protein kinase A phosphorylation of the cardiac calcium release channel (ryanodine receptor) in normal and failing hearts. Role of phosphatases and response to isoproterenol. J Biol Chem 2003; 278:444-53. [PMID: 12401811 DOI: 10.1074/jbc.m207028200] [Citation(s) in RCA: 165] [Impact Index Per Article: 7.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The cardiac ryanodine receptor/calcium release channel (RyR2) on the sarcoplasmic reticulum (SR) comprises a macromolecular complex that includes a kinase and two phosphatases that are bound to the channel via targeting proteins. We previously found that the RyR2 is protein kinase A (PKA)-hyperphosphorylated in end-stage human heart failure. Because heart failure is a progressive disease that often evolves from hypertrophy, we analyzed the RyR2 macromolecular complex in several animal models of cardiomyopathy that lead to heart failure, including hypertrophy, and at different stages of disease progression. We now show that RyR2 is PKA-hyperphosphorylated in diverse models of heart failure and that the degree of RyR2 PKA phosphorylation correlates with the degree of cardiac dysfunction. Interestingly, we show that RyR2 PKA hyperphosphorylation can be lost during perfusion of isolated hearts due to the activity of the endogenous phosphatases in the RyR2 macromolecular complex. Moreover, infusion of isoproterenol resulted in PKA phosphorylation of RyR2 in rat, indicating that systemic catecholamines can activate phosphorylation of RyR2 in vivo. These studies extend our previous analyses of the RyR2 macromolecular complex, show that both the kinase and phosphatase activities in the macromolecular complex are regulated physiologically in vivo, and suggest that RyR2 PKA hyperphosphorylation is likely a general feature of heart failure.
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Affiliation(s)
- Steven Reiken
- Center for Molecular Cardiology, Columbia University College of Physicians and Surgeons, New York, New York 10032, USA
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21
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Abstract
After 200 years of use, digitalis still appears to have a place in our armamentarium for heart failure and atrial fibrillation despite the proven survival benefits with ACE inhibitors and beta-blockers. Digoxin therapy is inexpensive and well tolerated and may result in considerable savings. Digoxin is the only oral inotrope that does not increase mortality in heart failure patients, particularly if low doses are being used. Digoxin therapy should be used in patients with systolic heart failure who continue to have signs and symptoms despite therapeutic doses of ACE inhibitors or diuretics or in patients with atrial fibrillation with or without heart failure for rate control.
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Affiliation(s)
- Eric J Eichhorn
- Cardiac Catheterization Laboratory and Department of Internal Medicine, Dallas Veterans Administration Hospital and University of Texas Southwestern Medical Center, Dallas, TX, USA
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22
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Birks EJ, Burton PB, Owen VJ, Latif N, Nyawo B, Yacoub MH. Molecular and cellular mechanisms of donor heart dysfunction. Transplant Proc 2001; 33:2749-51. [PMID: 11498147 DOI: 10.1016/s0041-1345(01)02178-9] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Affiliation(s)
- E J Birks
- National Heart and Lung Institute at Imperial College of Science, Technology and Medicine, Royal Brompton and Harefield Hospital, Harefield, Middlesex, United Kingdom
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23
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Nieminen MS, Akkila J, Hasenfuss G, Kleber FX, Lehtonen LA, Mitrovic V, Nyquist O, Remme WJ. Hemodynamic and neurohumoral effects of continuous infusion of levosimendan in patients with congestive heart failure. J Am Coll Cardiol 2000; 36:1903-12. [PMID: 11092663 DOI: 10.1016/s0735-1097(00)00961-x] [Citation(s) in RCA: 262] [Impact Index Per Article: 10.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
OBJECTIVES We sought to define the therapeutic dose range of levosimendan in patients with New York Heart Association class II-IV heart failure of ischemic origin. BACKGROUND Levosimendan is a calcium sensitizer for treatment of acute decompensated heart failure. METHODS A double-blind, placebo-controlled, randomized, multicenter, parallel-group study included 151 adult patients. Levosimendan was given as a 10-min intravenous bolus of 3, 6, 12, 24 or 36 microg/kg, followed by a 24-h infusion of 0.05, 0.1, 0.2, 0.4 or 0.6 microg/kg/min, respectively. Dobutamine, for comparative purposes, was given as an open-label infusion (6 microg/kg/min). The primary efficacy variable was the proportion of patients achieving in each treatment group at least one of the following: 1) a > or =15% increase in stroke volume (SV) at 23 h to 24 h; 2) a > or =25% decrease in pulmonary capillary wedge pressure (PCWP) (and > or =4 mm Hg) at 23 h to 24 h; 3) a > or =40% increase in cardiac output (CO) (with change in heart rate [HR] <20%); 4) a > or =50% decrease in PCWP during two consecutive measurements. RESULTS The response rate to levosimendan ranged from 50% at the lowest dose to 88% at the highest dose (compared with placebo 14%, dobutamine 70%). A dose-response relationship was demonstrated for levosimendan on increases in CO and SV, and reductions in PCWP during the infusion (for all, p< or =0.001). Headache (9%), nausea (5%) and hypotension (5%) were the most frequently reported adverse events at higher dosages. CONCLUSIONS Dosing of levosimendan with a 10-min bolus of 6 to 24 microg/kg followed by an infusion of 0.05 to 0.2 microg/kg/min is well tolerated and leads to favorable hemodynamic effects.
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24
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Abstract
The therapeutic indications for digoxin in the treatment of children with large left-to-right shunts continue to be reassessed. New insights into the alterations in cardiac function imposed by this hemodynamic burden have shown preserved systolic performance. Pharmacological interventions that improve cardiac output by afterload reduction or other modalities have proven useful and potentially have low risk for serious toxicity. Early and successful surgical treatment of most conditions causing pulmonary overcirculation has shortened the duration of medical management and prevented many of the untoward complications of this pathology. As new agents are forthcoming to treat various cardiac conditions, use-by-tradition of cardiac glycosides has appropriately diminished. While the understanding of complicated molecular aspects of cation transport have been enhanced by the unique actions of cardiac glycosides, their clinical utility has decreased. This report summarizes studies on the use of cardiac glycosides in the treatment of large left-to-right shunts in children.
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Affiliation(s)
- TJ Hougen
- Georgetown University Children's Medical Center, Division of Cardiology, 2-PHC, 3800 Reservoir Road NW, 20007-2197, Washington, DC, USA
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25
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Janssen PM, Datz N, Zeitz O, Hasenfuss G. Levosimendan improves diastolic and systolic function in failing human myocardium. Eur J Pharmacol 2000; 404:191-9. [PMID: 10980279 DOI: 10.1016/s0014-2999(00)00609-9] [Citation(s) in RCA: 60] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/17/2022]
Abstract
Ca(2+)-sensitizers increase myocardial contractility, but may worsen diastolic dysfunction. Levosimendan, through its unique troponin-C interaction, may preserve diastolic function. We investigated the effects of levosimendan (10(-7)-10(-5) M) on diastolic and systolic function in multicellular cardiac muscle preparations from end-stage failing human hearts (1 and 2.5 Hz, 37 degrees C, 1.25 mM [Ca(2+)], pH 7.4). Levosimendan improved systolic function: at 1 Hz, developed force (F(dev)) increased from 13.84+/-3.27 to 16.40+/-3.57 (10(-7) M, P<0.05), while diastolic force (F(dia)) decreased from 5.32+/-0.67 to 4.94+/-0.61 mN/mm(2) (P<0.05). Under control conditions, the increase in stimulation frequency from 1 to 2.5 Hz resulted in a decrease in F(dev) of -0.51+/-1.80 mN/mm(2) (negative force-frequency relationship). Levosimendan improved this relationship: at 10(-7) M, this change became positive (+1.81+/-2.06 mN/mm(2), P<0.05). Diastolic function was markedly improved in the presence of levosimendan; the increase in F(dia) of 1.56+/-0.42 mN/mm(2) (control) was attenuated to 0.70+/-0.19 mN/mm(2) (P<0.05). To allow for a more detailed analysis, preparations were sometimes divided into two groups, based on their force-frequency behavior. Twitch timing parameters were accelerated by levosimendan in preparations with a negative force-frequency relationship. Levosimendan improves both systolic and diastolic function in failing human myocardium. Effects are even more pronounced at higher heart rates and under prevailing diastolic dysfunction.
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Affiliation(s)
- P M Janssen
- Abt. Kardiologie und Pneumologie, Universität Göttingen, Göttingen, Germany.
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26
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Hermann HP, Zeitz O, Keweloh B, Hasenfuss G, Janssen PM. Pyruvate potentiates inotropic effects of isoproterenol and Ca(2+) in rabbit cardiac muscle preparations. Am J Physiol Heart Circ Physiol 2000; 279:H702-8. [PMID: 10924069 DOI: 10.1152/ajpheart.2000.279.2.h702] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Catecholamines and elevated extracellular Ca(2+) concentration ([Ca(2+)](o)) augment contractile force by increased Ca(2+) influx and subsequent increased sarcoplasmic reticulum (SR) Ca(2+) release. We tested the hypothesis that pyruvate potentiates Ca(2+) release and inotropic response to isoproterenol and elevated [Ca(2+)](o), since this might be of potential importance in a clinical setting to circumvent deleterious effects on energy demand during application of catecholamines. Therefore, we investigated isometrically contracting myocardial preparations from rabbit hearts at 37 degrees C, pH 7.4, and a stimulation frequency of 1 Hz. At a [Ca(2+)](o) of 1.25 mM, pyruvate (10 mM) alone increased developed force (F(dev)) from 1.89 +/- 0.42 to 3.62 +/- 0.62 (SE) mN/mm(2) (n = 8, P < 0.05) and isoproterenol (10(-6) M) alone increased F(dev) from 2.06 +/- 0. 55 to 25.11 +/- 2.1 mN/mm(2) (P < 0.05), whereas the combination of isoproterenol and pyruvate increased F(dev) overproportionally from 1.89 +/- 0.42 to 33.31 +/- 3.18 mN/mm(2) (P < 0.05). In a separate series of experiments, we assessed SR Ca(2+) content by means of rapid cooling contractures and observed that, despite no further increase in F(dev) by increasing [Ca(2+)](o) from 8 to 16 mM, 10 mM pyruvate could still increase F(dev) from 26.4 +/- 6.8 to 29.7 +/- 7. 1 mN/mm(2) (P < 0.05, n = 9) as well as the Ca(2+) load of the SR. The results show that the positive inotropic effects of pyruvate potentiate the inotropic effects of isoproterenol or Ca(2+), because in the presence of pyruvate, Ca(2+) and isoproterenol induced larger increases in inotropy than can be calculated by mere addition of the individual effects.
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Affiliation(s)
- H P Hermann
- Abteilung für Kardiologie und Pneumologie, Universität Göttingen, D-37075 Göttingen, Germany
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27
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Litwin SE, Zhang D, Roberge P, Pennock GD. DITPA prevents the blunted contraction-frequency relationship in myocytes from infarcted hearts. Am J Physiol Heart Circ Physiol 2000; 278:H862-70. [PMID: 10710355 DOI: 10.1152/ajpheart.2000.278.3.h862] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Loss of the positive force-frequency relationship is a characteristic finding in failing hearts. The mechanisms of this change are not well understood. Myocardial infarction (MI) was induced in rabbits to produce left ventricular (LV) dysfunction. Beginning 1 day after MI, a subgroup of rabbits received diiodothyropropionic acid (DITPA) (3.75 mg x kg(-1) x day(-1) sc) for 3 wk. We measured contractions, Ca(2+) transients, action potentials, and sarcoplasmic reticulum (SR) Ca(2+) content at different stimulation rates in single LV myocytes. The shortening-frequency relationship was markedly flattened in MI myocytes compared with control myocytes. In addition, Ca(2+) transients, action potentials, and contractions were prolonged. Myocytes from DITPA-treated MI rabbits had preserved inotropic responses to increased stimulation rate and normal duration of action potentials and Ca(2+) transients. SR Ca(2+) content increased significantly when stimulation rate was increased from 0.5 to 2.0 Hz in control myocytes but did not change significantly in MI myocytes. Myocytes from DITPA-treated MI rabbits had a greater frequency-dependent increase in SR Ca(2+) content compared with the untreated MI rabbits. Thus single myocytes from infarcted rabbit hearts have frequency-dependent abnormalities of contractility, Ca(2+) cycling, and action potential repolarization. The flattened contraction-frequency relationship can be partially explained by an attenuation of the normal enhancement of SR Ca(2+) content that occurs when stimulation rate is increased. Chronic DITPA administration after MI largely prevents the development of these abnormalities.
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Affiliation(s)
- S E Litwin
- Cardiovascular Division, Veterans Affairs Medical Center, and University of Utah Health Sciences Center, Salt Lake City, Utah 84132, USA.
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28
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Miyamoto MI, del Monte F, Schmidt U, DiSalvo TS, Kang ZB, Matsui T, Guerrero JL, Gwathmey JK, Rosenzweig A, Hajjar RJ. Adenoviral gene transfer of SERCA2a improves left-ventricular function in aortic-banded rats in transition to heart failure. Proc Natl Acad Sci U S A 2000; 97:793-8. [PMID: 10639159 PMCID: PMC15410 DOI: 10.1073/pnas.97.2.793] [Citation(s) in RCA: 415] [Impact Index Per Article: 17.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023] Open
Abstract
In human and experimental models of heart failure, sarcoplasmic reticulum Ca(2+) ATPase (SERCA2a) activity is decreased, resulting in abnormal calcium handling. The disturbances in calcium metabolism have been shown to contribute significantly to the contractile dysfunction observed in heart failure. We investigated whether increasing SERCA2a expression can improve ventricular function in an animal model of heart failure obtained by creating ascending aortic constriction in rats. After 19-23 wk of banding during the transition from compensated hypertrophy to heart failure (documented by >25% decrease in fractional shortening), rats were randomized to receive either an adenovirus carrying the SERCA2a gene (Ad.SERCA2a, n = 13) or beta-galactosidase (Ad.betagal, n = 14) by using a catheter-based technique. The failing hearts infected with Ad. betagal were characterized by a significant decrease in SERCA2a expression and a decrease in SERCA2a activity compared with nonfailing sham-operated rats (n = 11). In addition, these failing hearts had reduced left-ventricular systolic pressure, maximal rate of left-ventricular pressure rise and decline (+dP/dt, -dP/dt), and rate of isovolumic relaxation (tau). Overexpression of SERCA2a restored both SERCA2a expression and ATPase activity to nonfailing levels. Furthermore, rats infected with Ad.SERCA2a had significant improvement in left-ventricular systolic pressure, +dP/dt, -dP/dt, and rate of isovolumic relaxation (tau) normalizing them back to levels comparable to sham-operated rats. In this study, we show that in an animal model of heart failure where SERCA2a protein levels and activity are decreased and severe contractile dysfunction is present, overexpression of SERCA2a in vivo restores both systolic and diastolic function to normal levels.
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Affiliation(s)
- M I Miyamoto
- Cardiovascular Research Center, Massachusetts General Hospital, Boston, MA 02129, USA
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Janssen PM, Lehnart SE, Prestle J, Hasenfuss G. Preservation of contractile characteristics of human myocardium in multi-day cell culture. J Mol Cell Cardiol 1999; 31:1419-27. [PMID: 10423340 DOI: 10.1006/jmcc.1999.0978] [Citation(s) in RCA: 42] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Functional studies of different human cell types have been successfully conducted under in vitro conditions. Despite many efforts, it has not been possible to develop a human myocardial preparation in which contractile function can be studied over several days. We hypothesize that by mimicking the in vivo situation in an in vitro environment we can preserve viability and function of human myocardial preparations over several days. From explanted hearts of patients undergoing cardiac transplantation, multicellular preparations were dissected and mounted in a sterile muscle chamber. Muscles were stimulated at 0.5 or 1 Hz at 1.75 mmol/l Ca(2+), a pH of 7.4 and at 37 degrees C, and kept contracting isometrically for 2-6 days. This study shows for the first time that contractile function of human myocardial tissue can be preserved over several days; active force development had not significantly changed after 48 h (10.6+/-1.2 at t=0 v 11.4+/-2.8 mN/mm(2)at t=48, n=10), nor had diastolic force (1.0+/-0.1 v 0.9+/-0.1 mN/mm(2)). After at least 48 h, the contractile response to stimulation with 1 micromol/l isoproterenol was clearly present: developed force increased to 631+/-146% of control values, while half-relaxation time declined to 57+/-6% (n=7). In addition, both pharmacological responses and regulatory physiological behavior, such as post-rest potentiation and force-frequency relationships, are preserved. This technique allows the study of the regulation of contractile function of human myocardium in vitro and may be used to link changes in protein expression to consequent changes in myocardial contraction.
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Affiliation(s)
- P M Janssen
- Department of Cardiology and Pneumology, University of Göttingen, Göttingen, Germany
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Hermann HP, Pieske B, Schwarzmüller E, Keul J, Just H, Hasenfuss G. Haemodynamic effects of intracoronary pyruvate in patients with congestive heart failure: an open study. Lancet 1999; 353:1321-3. [PMID: 10218531 DOI: 10.1016/s0140-6736(98)06423-x] [Citation(s) in RCA: 88] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
BACKGROUND Pyruvate, as an intermediate in the Krebs cycle, is an important source of energy for myocardium and improves contractility of normal, hypoxic, and postischaemic animal myocardium. We investigated the effect of intracoronary pyruvate in patients with congestive heart failure. METHODS Haemodynamic measurements were done in eight patients with dilated cardiomyopathy after two 15 min infusions of pyruvate into the left main coronary artery and after saline washout of pyruvate. FINDINGS There were no significant differences between the two pyruvate concentrations. Application of pyruvate resulted in a 23% increase in cardiac index (p<0.05), a 38% increase in stroke-volume index (p<0.05), and a 36% decrease in pulmonary capillary wedge pressure (p<0.05). Heart rate decreased significantly by 11%. Mean aortic pressure and systemic vascular resistance did not change. Most of the effects of pyruvate were reversed 15 min after the infusion stopped. INTERPRETATION Pyruvate has the profile of a favourable inotropic substance. Other modes of administration need to be studied.
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Affiliation(s)
- H P Hermann
- Zentrum Innere Medizin, Abteilung Kardiologie und Pneumologie, Universität Göttingen, Germany
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Abstract
Despite the documented efficacy of cardiac glycosides in improving symptoms in patients with heart failure caused by systolic ventricular dysfunction, considerable debate continues as to whether the use of this class of drugs should continue into the next millennium. In this review, the authors briefly examine the basic pharmacology of these drugs relevant to the treatment of heart failure, emphasizing their role in reducing sympathetic nervous system activity in patients with advanced heart failure. Next, withdrawal trials and the Digoxin Investigation Group dataset are reviewed in some detail. Despite these important additional data on the safety and efficacy of digitalis use in heart failure that became available in the 1990s, considerable controversy remains. Perhaps most importantly, if the mechanism by which these drugs improve symptoms in patients with heart failure is principally mediated by sympatholytic activity, do they remain relevant as beta-adrenergic antagonists become standard therapy for this disease?
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Affiliation(s)
- P J Hauptman
- Cardiology Division, Saint Louis University Hospital and Saint Louis University School of Medicine, MO, USA
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Shimizu J, Araki J, Mizuno J, Lee S, Syuu Y, Hosogi S, Mohri S, Mikane T, Takaki M, Taylor TW, Suga H. A new integrative method to quantify total Ca2+ handling and futile Ca2+ cycling in failing hearts. THE AMERICAN JOURNAL OF PHYSIOLOGY 1998; 275:H2325-33. [PMID: 9843835 DOI: 10.1152/ajpheart.1998.275.6.h2325] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Ca2+ handling in excitation-contraction coupling requires considerable O2 consumption (VO2) in cardiac contraction. We have developed an integrative method to quantify total Ca2+ handling in normal hearts. However, its direct application to failing hearts, where futile Ca2+ cycling via the Ca2+-leaky sarcoplasmic reticulum (SR) required an increased Ca2+ handling VO2, was not legitimate. To quantify total Ca2+ handling even in such failing hearts, we combined futile Ca2+ cycling with Ca2+ handling VO2 and the internal Ca2+ recirculation fraction via the SR. We applied this method to the canine heart mechanoenergetics before and after intracoronary ryanodine at nanomolar concentrations. We found that total Ca2+ handling per beat was halved after the ryanodine treatment from approximately 60 micromol/kg left ventricle before ryanodine. We also found that futile Ca2+ cycling via the SR increased to >1 cycle/beat after ryanodine from presumably zero before ryanodine. These results support the applicability of the present method to the failing hearts with futile Ca2+ cycling via the SR.
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Affiliation(s)
- J Shimizu
- Department of Physiology II, Okayama University Medical School, Okayama 700-8558, 634-8521 Japan
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Lehnart SE, Schillinger W, Pieske B, Prestle J, Just H, Hasenfuss G. Sarcoplasmic reticulum proteins in heart failure. Ann N Y Acad Sci 1998; 853:220-30. [PMID: 10603950 DOI: 10.1111/j.1749-6632.1998.tb08270.x] [Citation(s) in RCA: 52] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
Altered calcium homeostasis may play a key role in the pathophysiology of human heart failure. Levels of sarcoplasmic reticulum (SR) proteins and sarcolemmal Na(+)-Ca2+ exchanger were analyzed by Western blot in failing and nonfailing human myocardium and related to myocardial function. Levels of the SR calcium release channel and of calcium storage proteins (calsequestrin and calreticulin) were not different in nonfailing and failing hearts. However, proteins involved in calcium removal were significantly altered in the failing human heart: (1) SR-Ca(2+)-ATPase levels and the ratio of SR-Ca(2+)-ATPase to its inhibitory protein phospholamban were significantly decreased, and (2) Na(+)-Ca2+ exchanger levels and the ratio of Na(+)-Ca2+ exchanger to SR-Ca(2+)-ATPase were significantly increased. SR-Ca(2+)-ATPase levels were closely correlated to systolic function as evaluated by frequency potentiation of contractile force. The frequency-dependent rise of diastolic force was inversely correlated with protein levels of Na(+)-Ca2+ exchanger. These findings indicate that altered expression of SR-Ca(2+)-ATPase and Na(+)-Ca2+ exchanger is relevant for altered systolic and diastolic function in human heart failure.
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Affiliation(s)
- S E Lehnart
- Medizinische Klinik III, Universität Freiburg, Germany
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Syuu Y, Araki J, Lee S, Suzuki S, Mizuno J, Mohri S, Mikane T, Shimizu J, Takaki M, Suga H. Effects of Ca2+ and epinephrine on Ca2+ recirculation fraction and total Ca2+ handling in canine left ventricles. THE JAPANESE JOURNAL OF PHYSIOLOGY 1998; 48:123-32. [PMID: 9639547 DOI: 10.2170/jjphysiol.48.123] [Citation(s) in RCA: 19] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
Abstract
We investigated the effects of intracoronary Ca2+ and epinephrine on the intracellular Ca2+ recirculation fraction (RF) and total Ca2+ handling in the left ventricle (LV) of the excised cross-circulated canine heart preparation. We analyzed LV postextrasystolic potentiation (PESP) following a spontaneous extrasystole that occurred sporadically under constant atrial pacing. All PESPs decayed in alternans and none decayed monotonically. We extracted an exponential decay component from the alternans PESP, determined its beat constant (taue), and calculated RF = exp(-1/taue). Increased intracoronary Ca2+ slightly increased taue and RF, but epinephrine did not change them, although both agents enhanced LV contractility 2-3 times. Neither Ca2+ nor epinephrine affected the sinusoidal decay of the alternans PESP. These results indicate that RF via the sarcoplasmic reticulum was slightly augmented by Ca2+, but not by epinephrine. We combined these RF data with LV Ca2+ handling O2 consumption data and obtained 40-110 micromol/kg as the total amount of Ca2+ handled in one cardiac cycle in the control and enhanced contractile states. These results indicate that this new LV-level approach seems to better the understanding of the Ca2+ mass dynamics responsible for the mechanoenergetics enhanced by inotropic interventions.
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Affiliation(s)
- Y Syuu
- Department of Physiology II, Okayama University Medical School, Shikata-cho, Okayama, 700-8558, Japan
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