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Szyller J, Antoniak R, Wadowska K, Bil-Lula I, Hrymniak B, Banasiak W, Jagielski D. Redox imbalance in patients with heart failure and ICD/CRT-D intervention. Can it be an underappreciated and overlooked arrhythmogenic factor? A first preliminary clinical study. Front Physiol 2023; 14:1289587. [PMID: 38028798 PMCID: PMC10663344 DOI: 10.3389/fphys.2023.1289587] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/06/2023] [Accepted: 10/23/2023] [Indexed: 12/01/2023] Open
Abstract
Introduction: Redox imbalance and oxidative stress are involved in the pathogenesis of arrhythmias. They also play a significant role in pathogenesis of heart failure (HF). In patients with HFand implanted cardioverter-defibrillator (ICD) or cardiac resynchronization therapy defibrillator (CRT-D), the direct current shocks may be responsible for additional redox disturbances and additionally increase arrhythmia risk. However, the precise role of oxidative stress in potentially fatal arrhythmias and shock induction remains unclear. Methods: 36 patients with diagnosed HF and implanted ICD/CRT-D were included in this study. Patients were qualified to the study group in case of registered ventricular arrhythmia and adequate ICD/CRT-D intervention. The control group consisted of patients without arrhythmia with elective replacement indicator (ERI) status. Activity of superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GPx), glutathione (GSH) in erythrocyte (RBC), SOD, GPx activity and reactive oxygen/nitrogen species (ROS/RNS) concentration in plasma were determined. The values were correlated with glucose, TSH, uric acid, Mg and ion concentrations. Results: In the perishock period, we found a significant decrease in RBC and extracellular (EC) SOD and RBC CAT activity (p = 0.0110, p = 0.0055 and p = 0.0002, respectively). EC GPx activity was also lower (p = 0.0313). In all patients, a decrease in the concentration of all forms of glutathione was observed compared to the ERI group. Important association between ROS/RNS and GSH, Mg, TSH and uric acid was shown. A relationship between the activity of GSH and antioxidant enzymes was found. Furthermore, an association between oxidative stress and ionic imbalance has also been demonstrated. The patients had an unchanged de Haan antioxidant ratio and glutathione redox potential. Conclusion: Here we show significant redox disturbances in patients with HF and ICD/CRT-D interventions. Oxidative stress may be an additional risk factor for the development of arrhythmia in patients with HF. The detailed role of oxidative stress in ventricular arrhythmias requires further research already undertaken by our team.
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Affiliation(s)
- Jakub Szyller
- Division of Clinical Chemistry and Laboratory Hematology, Department of Medical Laboratory Diagnostics, Faculty of Pharmacy, Wroclaw Medical University, Wroclaw, Poland
| | - Radosław Antoniak
- Department of Cardiology, Centre for Heart Diseases, 4th Military Hospital, Wroclaw, Poland
| | - Katarzyna Wadowska
- Division of Clinical Chemistry and Laboratory Hematology, Department of Medical Laboratory Diagnostics, Faculty of Pharmacy, Wroclaw Medical University, Wroclaw, Poland
| | - Iwona Bil-Lula
- Division of Clinical Chemistry and Laboratory Hematology, Department of Medical Laboratory Diagnostics, Faculty of Pharmacy, Wroclaw Medical University, Wroclaw, Poland
| | - Bruno Hrymniak
- Department of Cardiology, Centre for Heart Diseases, 4th Military Hospital, Wroclaw, Poland
| | - Waldemar Banasiak
- Department of Cardiology, Centre for Heart Diseases, 4th Military Hospital, Wroclaw, Poland
- Faculty of Medicine, Wroclaw University of Science and Technology, Wroclaw, Poland
| | - Dariusz Jagielski
- Department of Cardiology, Centre for Heart Diseases, 4th Military Hospital, Wroclaw, Poland
- Faculty of Medicine, Wroclaw University of Science and Technology, Wroclaw, Poland
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Clementy N, Bodin A, Bisson A, Teixeira-Gomes AP, Roger S, Angoulvant D, Labas V, Babuty D. The Defibrillation Conundrum: New Insights into the Mechanisms of Shock-Related Myocardial Injury Sustained from a Life-Saving Therapy. Int J Mol Sci 2021; 22:5003. [PMID: 34066832 PMCID: PMC8125879 DOI: 10.3390/ijms22095003] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/26/2021] [Revised: 05/03/2021] [Accepted: 05/05/2021] [Indexed: 11/16/2022] Open
Abstract
Implantable cardiac defibrillators (ICDs) are recommended to prevent the risk of sudden cardiac death. However, shocks are associated with an increased mortality with a dose response effect, and a strategy of reducing electrical therapy burden improves the prognosis of implanted patients. We review the mechanisms of defibrillation and its consequences, including cell damage, metabolic remodeling, calcium metabolism anomalies, and inflammatory and pro-fibrotic remodeling. Electrical shocks do save lives, but also promote myocardial stunning, heart failure, and pro-arrhythmic effects as seen in electrical storms. Limiting unnecessary implantations and therapies and proposing new methods of defibrillation in the future are recommended.
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Affiliation(s)
- Nicolas Clementy
- Service de Cardiologie, Hôpital Trousseau, Université de Tours, 37044 Tours, France; (A.B.); (A.B.); (D.A.); (D.B.)
- Transplantation, Immunologie et Inflammation T2I-EA 4245, Université de Tours, 37044 Tours, France;
| | - Alexandre Bodin
- Service de Cardiologie, Hôpital Trousseau, Université de Tours, 37044 Tours, France; (A.B.); (A.B.); (D.A.); (D.B.)
| | - Arnaud Bisson
- Service de Cardiologie, Hôpital Trousseau, Université de Tours, 37044 Tours, France; (A.B.); (A.B.); (D.A.); (D.B.)
- Transplantation, Immunologie et Inflammation T2I-EA 4245, Université de Tours, 37044 Tours, France;
| | - Ana-Paula Teixeira-Gomes
- Plate-forme de Chirurgie et d’Imagerie pour la Recherche et l’Enseignement (CIRE), INRA, Université de Tours, CHU de Tours, 37380 Nouzilly, France; (A.-P.T.-G.); (V.L.)
| | - Sebastien Roger
- Transplantation, Immunologie et Inflammation T2I-EA 4245, Université de Tours, 37044 Tours, France;
| | - Denis Angoulvant
- Service de Cardiologie, Hôpital Trousseau, Université de Tours, 37044 Tours, France; (A.B.); (A.B.); (D.A.); (D.B.)
- Transplantation, Immunologie et Inflammation T2I-EA 4245, Université de Tours, 37044 Tours, France;
| | - Valérie Labas
- Plate-forme de Chirurgie et d’Imagerie pour la Recherche et l’Enseignement (CIRE), INRA, Université de Tours, CHU de Tours, 37380 Nouzilly, France; (A.-P.T.-G.); (V.L.)
| | - Dominique Babuty
- Service de Cardiologie, Hôpital Trousseau, Université de Tours, 37044 Tours, France; (A.B.); (A.B.); (D.A.); (D.B.)
- Transplantation, Immunologie et Inflammation T2I-EA 4245, Université de Tours, 37044 Tours, France;
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Bodin A, Labas V, Bisson A, Teixeira-Gomes AP, Blasco H, Tomas D, Combes-Soia L, Marcelo P, Miquelestorena-Standley E, Baron C, Angoulvant D, Babuty D, Clementy N. Acute pathophysiological myocardial changes following intra-cardiac electrical shocks using a proteomic approach in a sheep model. Sci Rep 2020; 10:20252. [PMID: 33219330 PMCID: PMC7679418 DOI: 10.1038/s41598-020-77346-x] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/09/2020] [Accepted: 11/04/2020] [Indexed: 12/18/2022] Open
Abstract
Implantable cardioverter-defibrillators (ICD) are meant to fight life-threatening ventricular arrhythmias and reduce overall mortality. Ironically, life-saving shocks themselves have been shown to be independently associated with an increased mortality. We sought to identify myocardial changes at the protein level immediately after ICD electrical shocks using a proteomic approach. ICD were surgically implanted in 10 individuals of a healthy male sheep model: a control group (N = 5) without any shock delivery and a shock group (N = 5) with the delivery of 5 consecutive shocks at 41 J. Myocardial tissue samples were collected at the right-ventricle apex near to the lead coil and at the right ventricle basal free wall region. Global quantitative proteomics experiments on myocardial tissue samples were performed using mass spectrometry techniques. Proteome was significantly modified after electrical shock and several mechanisms were associated: protein, DNA and membrane damages due to extreme physical conditions induced by ICD-shock but also due to regulated cell death; metabolic remodeling; oxidative stress; calcium dysregulation; inflammation and fibrosis. These proteome modifications were seen in myocardium both "near" and "far" from electrical shock region. N-term acetylated troponin C was an interesting tissular biomarker, significantly decreased after electrical shock in the "far" region (AUC: 0.93). Our data support an acute shock-induced myocardial tissue injury which might be involved in acute paradoxical deleterious effects such as heart failure and ventricular arrhythmias.
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Affiliation(s)
- Alexandre Bodin
- Service de Cardiologie, Centre Hospitalier Universitaire Trousseau Et EA7505, Faculté de Médecine, Université François Rabelais, Tours, France.
- INRAE, CNRS, IFCE, UMR PRC, Université de Tours, 37380, Nouzilly, France.
| | - Valérie Labas
- INRAE, CNRS, IFCE, UMR PRC, Université de Tours, 37380, Nouzilly, France
- INRAE, CHU de Tours, Plate-Forme de Chirurgie Et D'Imagerie Pour La Recherche Et L'Enseignement, Université de Tours, 37380, Nouzilly, France
| | - Arnaud Bisson
- Service de Cardiologie, Centre Hospitalier Universitaire Trousseau Et EA7505, Faculté de Médecine, Université François Rabelais, Tours, France
| | | | - Hélène Blasco
- Imagerie Et Cerveau - UMR 1253, Université de Tours, Tours, France
| | - Daniel Tomas
- INRAE, CNRS, IFCE, UMR PRC, Université de Tours, 37380, Nouzilly, France
- INRAE, CHU de Tours, Plate-Forme de Chirurgie Et D'Imagerie Pour La Recherche Et L'Enseignement, Université de Tours, 37380, Nouzilly, France
| | - Lucie Combes-Soia
- INRAE, CNRS, IFCE, UMR PRC, Université de Tours, 37380, Nouzilly, France
- INRAE, CHU de Tours, Plate-Forme de Chirurgie Et D'Imagerie Pour La Recherche Et L'Enseignement, Université de Tours, 37380, Nouzilly, France
| | - Paulo Marcelo
- Plate-Forme ICAP, Centre Universitaire de Recherche en Santé, Université de Picardie Jules Verne, 80054, Amiens, France
| | | | - Christophe Baron
- Transplantation, Immunologie et Inflammation T2i - EA 4245, Université de Tours, Tours, France
| | - Denis Angoulvant
- Service de Cardiologie, Centre Hospitalier Universitaire Trousseau Et EA7505, Faculté de Médecine, Université François Rabelais, Tours, France
- Transplantation, Immunologie et Inflammation T2i - EA 4245, Université de Tours, Tours, France
| | - Dominique Babuty
- Service de Cardiologie, Centre Hospitalier Universitaire Trousseau Et EA7505, Faculté de Médecine, Université François Rabelais, Tours, France
| | - Nicolas Clementy
- Service de Cardiologie, Centre Hospitalier Universitaire Trousseau Et EA7505, Faculté de Médecine, Université François Rabelais, Tours, France
- Transplantation, Immunologie et Inflammation T2i - EA 4245, Université de Tours, Tours, France
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Geraghty L, Santangeli P, Tedrow UB, Shivkumar K, Kumar S. Contemporary Management of Electrical Storm. Heart Lung Circ 2019; 28:123-133. [DOI: 10.1016/j.hlc.2018.10.005] [Citation(s) in RCA: 29] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/01/2018] [Accepted: 10/02/2018] [Indexed: 01/10/2023]
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Özcan F, Topaloğlu S, Çay S, Canpolat U, Özeke Ö, Turak O, Çetin H, Aras D. Catheter ablation of drug refractory electrical storm in patients with ischemic cardiomyopathy: A single center experience. Anatol J Cardiol 2015; 16:159-64. [PMID: 26467375 PMCID: PMC5336800 DOI: 10.5152/akd.2015.6095] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022] Open
Abstract
Objective: Electrical storm (ES) is a life-threatening pathology that requires immediate and effective treatment due to increased morbidity and mortality. Catheter ablation (CA) is an effective therapeutic option, particularly in patients with drug resistant ventricular arrhythmia episodes. These procedures should only be performed in highly specialized and experienced centers. Here we aimed to assess safety and efficacy of CA in a relatively large cohort with ES in our tertiary center hospital. Methods: A total of 44 patients (90.9% male; mean age: 59.7±10.3 years) with ischemic cardiomyopathy undergoing CA for drug-refractory ES were prospectively evaluated. Procedures were performed using non-contact and electro-anatomic mapping systems. Long-term follow-up analysis addressed the predictors of ES recurrence and cardiac mortality. Results: Acute success rates for clinical and non-clinical VTs were 90.8% and 55.5%, respectively. A mean follow-up at 28±11 months revealed cardiac mortality in 8 (18%) patients, 39 (88.6%) patients were free from the ES, and 24 (55%) patients remained free from both ES and paroxysmal VT episodes. In multivariate regression analysis, recurrence of ES (OR=3.11, 95% CI: 1.65-4.62, p=0.001), LVEF, and serum creatinine were found as independent predictors of cardiac mortality. In addition, substrate based ablation, implantation of ICD for secondary prophylaxis, LVEF, and serum creatinine were good predictors of ES recurrence. Conclusion: Catheter ablation for ventricular arrhythmias in the course of ES in patients with ischemic cardiomyopathy is safe with an acceptable success rate. (Anatol J Cardiol 2016; 16: 159-64)
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Affiliation(s)
- Fırat Özcan
- Department of Cardiology, Yüksek İhtisas Training and Research Hospital; Ankara-Turkey.
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Abstract
Electrical storm (ES), characterized by recurrent ventricular tachycardia/fibrillation, is a serious condition, adversely affecting prognosis in patients with implantable cardioverter/defibrillators. Electrical storm patients often die of progressive heart failure, but the underlying molecular basis is poorly understood. We have recently created an animal model of ES that features repetitive implantable cardioverter/defibrillator firing for recurrent ventricular fibrillation and found that ES events cause striking activation of Ca(2+)/calmodulin-dependent protein kinase II and prominent alteration of Ca(2+)-handling protein phosphorylation, possibly explaining mechanical dysfunction and arrhythmia promotion that characterize ES. Here, the pathophysiology and potential therapeutic strategies for ES, based on experimental and clinical studies by us and others, are described.
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Ferreira M, de Abreu LC, Valenti VE, Meneghini A, Murad N, Ferreira C. Electric countershock and cold stress effects on liver and adrenal gland. Clinics (Sao Paulo) 2010; 65:291-6. [PMID: 20360920 PMCID: PMC2845770 DOI: 10.1590/s1807-59322010000300009] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/31/2009] [Accepted: 11/26/2009] [Indexed: 11/26/2022] Open
Abstract
OBJECTIVES Cold exposure induces glycogen and lipid depletion in the liver and the adrenal gland, respectively. However, no previous study has determined the effects of electrical countershock on those tissues. We aimed to evaluate the effects of electrical countershock on lipid depletion in the adrenal gland and on glycogen depletion in the liver. METHODS We used 40 male Wistar rats divided into four groups: the control group, in which the animals were subjected to a resting period of seven days; the electrical discharge group, in which the animals were subjected to a resting period followed by administration of ten 300-mV electrical discharges; the electrical post-discharge group, in which the animals received ten electrical shocks (300 mV) followed by rest for seven consecutive days; and the cold stress group, in which the animals were subjected to a resting period and were then exposed to -8 degrees C temperatures for four hours. All animals underwent a laparotomy after treatment. The lipid and glycogen depletions are presented using intensity levels (where + = low intensity and ++++ = high intensity, with intermediate levels in between). RESULTS The rats exposed to the cold stress presented the highest glycogen and lipid depletion in the liver and the adrenal gland, respectively. Furthermore, we noted that the electrical countershock significantly increased lipid depletion in the adrenal gland and glycogen depletion in the liver. One week after the electrical countershock, the liver and adrenal gland profiles were similar to that of the control group. CONCLUSION Electrical countershock immediately increased the glycogen depletion in the liver and the lipid depletion in the adrenal gland of rats.
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Affiliation(s)
- Marcelo Ferreira
- Departamento de Clínica Médica, Disciplina de Cardiologia, Faculdade de Medicina do ABC - Santo André/SP, Brazil
- Departamento de Medicina, Disciplina de Cardiologia, Universidade Federal de São Paulo (UNIFESP) - São Paulo/SP, Brazil
| | - Luiz Carlos de Abreu
- Departamento de Morfologia e Fisiologia, Faculdade de Medicina do ABC - Santo André/SP, Brazil
| | - Vitor E. Valenti
- Departamento de Medicina, Disciplina de Cardiologia, Universidade Federal de São Paulo (UNIFESP) - São Paulo/SP, Brazil
| | - Adriano Meneghini
- Departamento de Clínica Médica, Disciplina de Cardiologia, Faculdade de Medicina do ABC - Santo André/SP, Brazil
| | - Neif Murad
- Departamento de Clínica Médica, Disciplina de Cardiologia, Faculdade de Medicina do ABC - Santo André/SP, Brazil
| | - Celso Ferreira
- Departamento de Clínica Médica, Disciplina de Cardiologia, Faculdade de Medicina do ABC - Santo André/SP, Brazil
- Departamento de Medicina, Disciplina de Cardiologia, Universidade Federal de São Paulo (UNIFESP) - São Paulo/SP, Brazil
- , Tel.: 55 11 4993.5403
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Ferreira M, Ferreira C, de Abreu LC, Valenti VE, Murad N, Meneghini A, Filho CF, Filho JADO. Myocardium tissue changes caused by electrical transthoracic discharges in rats. Int Arch Med 2009; 2:31. [PMID: 19852820 PMCID: PMC2771001 DOI: 10.1186/1755-7682-2-31] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/02/2009] [Accepted: 10/23/2009] [Indexed: 11/25/2022] Open
Abstract
Background Cardiomyocytes cytoarchitecture changes caused by transthoracic countershocks have been focused recently. We aimed to evaluate the effects of electrical discharge application in the mitochondria structure in atrial myocardium of rats. Methods An electrical cardioverter was adapted to small rodent animals for our research. Electrical discharges were applied to the precordial region of 30 albino rats: (1) control group - animals that remained on resting period and were afterwards sacrificed; (2) electrical discharge group - animals that remained on resting period, followed by ten electrical discharges of 300 mV and sacrificed, and; (3) electrical post-discharge group - animals that remained on a resting period and received ten electrical discharges like the electrical discharge group, but were sacrificed seven days subsequently. We examined liver, adrenal and left atrium tissue fragments of the three groups. Results It was observed in control and post-discharge groups a normal cellular structure aspect with preserved architecture of cardiomyocytes and continuous sarcoplasmic membrane integrity. On the other hand, cardiac muscle fibers with mitochondrial edema and lysis occurred in the discharge group. Glycogen and adrenal lipids were not depleted in all groups. Conclusion These data suggest that transthoracic electrical discharges induce mitochondrial injuries in atrial cardiac cells of rats.
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Affiliation(s)
- Marcelo Ferreira
- Department of Clinical Medicine, Cardiology Division, School of Medicine of ABC, Santo André, SP, Brazil.
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Schauvliege S, van Loon G, De Clercq D, Devisscher L, Deprez P, Gasthuys F. Cardiovascular responses to transvenous electrical cardioversion of atrial fibrillation in anaesthetized horses. Vet Anaesth Analg 2009; 36:341-51. [PMID: 19538571 DOI: 10.1111/j.1467-2995.2009.00470.x] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
OBJECTIVE To examine the influence of direct current shock application in anaesthetized horses with atrial fibrillation (AF) and to study the effects of cardioversion to sinus rhythm (SR). STUDY DESIGN Prospective clinical study. ANIMALS Eight horses successfully treated for AF (transvenous electrical cardioversion after amiodarone pre-treatment). METHODS Cardioversion catheters and a pacing catheter were placed under sedation [detomidine 10 microg kg(-1) intravenously (IV)]. After additional sedation (5-10 microg kg(-1) detomidine, 0.1 mg kg(-1) methadone IV), anaesthesia was induced with ketamine, 2.2 mg kg(-1) and midazolam, 0.06 mg kg(-1) (IV) in a sling and maintained with isoflurane in oxygen. Flunixin meglumine, 1.1 mg kg(-1), was administered IV. Shocks were delivered as biphasic truncated exponential waves, synchronized with the R-wave of the electrocardiogram. Monitoring included pulse oximetry, electrocardiography, capnography, inhalational anaesthetic agent concentration, arterial blood pressure, LiDCO and PulseCO cardiac index (CI) and arterial blood gases. Values before and after the first unsuccessful shock and before and after cardioversion to SR were compared. RESULTS Values before the first shock were comparable to reported values in healthy, isoflurane anaesthetized horses. Reliable CI measurements could not be obtained using the PulseCO technique. Intermittent positive pressure ventilation was required in most horses (bradypnea and/or PaCO(2) >8 kPa, 60 mmHg), while dobutamine was administered in two horses (0.3-0.5 microg kg(-1) minute(-1)). After the 1st unsuccessful shock application, systolic arterial pressure (SAP) was decreased (p = 0.025), other recorded values were not influenced (CI measurements not available for this analysis). SR was associated with increases in CI (p = 0.039) and stroke index (p = 0.002) and a decrease in SAP (p = 0.030). CONCLUSIONS AND CLINICAL RELEVANCE Despite the presence of AF, cardiovascular function was well maintained during anaesthesia and was not affected by shock application. Cardiac index and stroke index increased and SAP decreased after cardioversion.
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Affiliation(s)
- Stijn Schauvliege
- Faculty of Veterinary Medicine, Department of Surgery and Anaesthesia of Domestic Animals, Ghent University, Salisburylaan, Merelbeke, Belgium.
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Israel CW, Barold SS. Electrical storm in patients with an implanted defibrillator: a matter of definition. Ann Noninvasive Electrocardiol 2008; 12:375-82. [PMID: 17970963 DOI: 10.1111/j.1542-474x.2007.00187.x] [Citation(s) in RCA: 85] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/29/2023] Open
Abstract
The term "electrical storm" (ES) indicates a state of cardiac electrical instability manifested by several episodes of ventricular tachyarrhythmias (VTs) within a short time. In patients with an implantable cardioverter defibrillator (ICD), ES is best defined as 3 appropriate VT detections in 24 h, treated by antitachycardia pacing, shock or eventually untreated but sustained in a VT monitoring zone. The number of shocks and inappropriate detections are irrelevant for the definition. ES occurs in approximately 25% of ICD patients within 3 years, with typically 5-55 individual VTs within one storm. Potential triggers can be found in approximately 66% of patients and include new/worsened heart failure, changes in antiarrhythmic medication, context with other illness, psychological stress, diarrhea, and hypokalemia. In most patients, ES consists of monomorphic VT indicating the presence of reentry while ventricular fibrillation indicating acute ischemia is rare. ES seems to have a low immediate mortality (1%) but frequently (50-80%) leads to hospitalization. Long-term prognostic implications of ES are unclear. The key intervention in ES is reduction of the elevated sympathetic tone by beta blockers and frequently benzodiazepines. Amiodarone i.v. has also been successful and azimilide seems promising while class I antiarrhythmic drugs are usually unsuccessful. Substrate mapping and VT ablation may be useful in treatment and prevention of ES. Prevention of ES requires ICD programming systematically avoiding unnecessary shocks (long VT detection, antitachycardia pacing where ever possible) which otherwise can fuel the sympathetic tone and prolong ES.
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Affiliation(s)
- Carsten W Israel
- Department of Medicine, Division of Cardiology, J. W. Goethe University Hospital, Frankfurt, Germany.
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Lampert R, Soufer R, McPherson CA, Batsford WP, Tirado S, Earley C, Goldberg A, Shusterman V. Implantable Cardioverter-Defibrillator Shocks Increase T-Wave Alternans. J Cardiovasc Electrophysiol 2007; 18:512-7. [PMID: 17428273 DOI: 10.1111/j.1540-8167.2007.00787.x] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
INTRODUCTION While implantable defibrillator shocks save lives, shock can lead to ventricular arrhythmias. However, the mechanism of shock-related proarrhythmia remains unclear. We evaluated the impact of ICD shock on repolarization instability, a factor associated with ventricular arrhythmogenesis. METHODS AND RESULTS Sixty-five patients with ICDs underwent ambulatory ECG monitoring during defibrillation testing 3 months postimplant. TWA was analyzed continuously in the time domain during baseline, sedated, and post-shock states. RR, QRS, and QT intervals and catecholamines were also measured continuously. Adequate pre- and post-shock Holter data were recorded in 55 patients, 48 male, mean 64 +/- 12 years, 50 with coronary disease, 48 with prior spontaneous or induced arrhythmia. TWA significantly increased after shock, from 9.6 +/- 0.5 to 11.9 +/- 0.6 microV, as did QRS duration, epinephrine, and norepinephrine levels, compared with sedated and baseline states. RR intervals decreased minimally. TWA changes with shock were not associated with RR or QRS duration changes, but were associated with changes in epinephrine. CONCLUSIONS ICD shock, even in the sedated state, increases repolarization instability as measured by TWA, an effect mediated in part by sympathetic stimulation. This association between shock and TWA may have important mechanistic and clinical implications for optimization of defibrillation therapy.
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Affiliation(s)
- Rachel Lampert
- Department of Medicine, Yale University School of Medicine New Haven, Connecticut, USA.
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Kim M, Perrino BA. CaM kinase II activation and phospholamban phosphorylation by SNP in murine gastric antrum smooth muscles. Am J Physiol Gastrointest Liver Physiol 2007; 292:G1045-54. [PMID: 17185633 DOI: 10.1152/ajpgi.00203.2006] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
Elevations in the intracellular Ca(2+) concentration activate the serine/threonine protein kinase Ca(2+)/calmodulin-dependent protein kinase II (CaM kinase II). We tested the hypothesis that increased sarco(endo)plasmic reticulum Ca(2+)-ATPase activity by phospholamban (PLB) phosphorylation contributes to smooth muscle relaxation by elevating the sarcoplasmic reticulum (SR) Ca(2+) load and increasing the frequency of Ca(2+) release events from the SR. We have previously shown that caffeine or sodium nitroprusside (SNP) relaxes murine gastric fundus smooth muscles and increases PLB phosphorylation by CaM kinase II. These findings suggest that an increased SR Ca(2+) load increases the frequency of Ca(2+) transients from the SR and results in PLB phosphorylation by CaM kinase II, contributing to caffeine- or SNP-induced relaxation. The aim of the present study was to investigate the effects of SNP on CaM kinase II and PLB phosphorylation in gastric antrum smooth muscles. SNP or 8-bromo-cGMP decreased the basal tone and amplitudes of spontaneous phasic contractions and activated CaM kinase II. SNP-induced relaxation and CaM kinase II activation were blocked by [1,2,4]oxadizolo-[4,3alpha]quinoxaline-1-one (ODQ) and inhibited by cyclopiazonic acid (CPA) or KN-93. SNP also increased PLBSer(16) and PLBThr(17) phosphorylation. Both PLBSer(16) and Thr(17) phosphorylation were ODQ sensitive. However, only PLBThr(17) phosphorylation was inhibited by CPA or KN-93. These results suggest that CaM kinase II activation and PLB phosphorylation participate in the relaxant effect of SNP on murine gastric antrum smooth muscles through a nitric oxide/guanylyl cyclase/cGMP pathway.
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Affiliation(s)
- Minkyung Kim
- Department of Physiology and Cell Biology, Center of Biomedical Research Excellence, University of Nevada School of Medicine, Anderson Bldg., MS352, Reno, NV 89557, USA
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Jiang M, Xu A, Narayanan N. Thyroid hormone downregulates the expression and function of sarcoplasmic reticulum-associated CaM kinase II in the rabbit heart. Am J Physiol Heart Circ Physiol 2006; 291:H1384-94. [PMID: 16617128 DOI: 10.1152/ajpheart.00875.2005] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Phosphorylation of sarcoplasmic reticulum (SR) Ca2+-cycling proteins by a membrane-associated Ca2+/calmodulin-dependent protein kinase II (CaM kinase II) is a well-documented physiological mechanism for regulation of transmembrane Ca2+fluxes and the cardiomyocyte contraction-relaxation cycle. The present study investigated the effects of l-thyroxine-induced hyperthyroidism on protein expression of SR CaM kinase II and its substrates, endogenous CaM kinase II-mediated SR protein phosphorylation, and SR Ca2+pump function in the rabbit heart. Membrane vesicles enriched in junctional SR (JSR) or longitudinal SR (LSR) isolated from euthyroid and hyperthyroid rabbit hearts were utilized. Endogenous CaM kinase II-mediated phosphorylation of ryanodine receptor-Ca2+release channel (RyR-CRC), Ca2+-ATPase, and phospholamban (PLN) was significantly lower (30–70%) in JSR and LSR vesicles from hyperthyroid than from euthyroid rabbit heart. Western immunoblotting analysis revealed significantly higher (∼40%) levels of sarco(endo)plasmic reticulum Ca2+-ATPase isoform 2 (SERCA2) in JSR, but not in LSR, from hyperthyroid than from euthyroid rabbit heart. Maximal velocity of Ca2+uptake was significantly increased in JSR (130%) and LSR (50%) from hyperthyroid compared with euthyroid rabbit hearts. Apparent affinity of the Ca2+-ATPase for Ca2+did not differ between the two groups. Protein levels of PLN and CaM kinase II were significantly lower (30–40%) in JSR, LSR, and ventricular tissue homogenates from hyperthyroid rabbit heart. These findings demonstrate selective downregulation of expression and function of CaM kinase II in hyperthyroid rabbit heart in the face of upregulated expression and function of SERCA2 predominantly in the JSR compartment.
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Affiliation(s)
- Mao Jiang
- Department of Physiology and Pharmacology, Health Science Center, The University of Western Ontario, London, ON, Canada N6A 5C1
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Kim M, Han IS, Koh SD, Perrino BA. Roles of CaM kinase II and phospholamban in SNP-induced relaxation of murine gastric fundus smooth muscles. Am J Physiol Cell Physiol 2006; 291:C337-47. [PMID: 16510846 DOI: 10.1152/ajpcell.00397.2005] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/14/2023]
Abstract
The mechanisms by which nitric oxide (NO) relaxes smooth muscles are unclear. The NO donor sodium nitroprusside (SNP) has been reported to increase the Ca2+ release frequency (Ca2+ sparks) through ryanodine receptors (RyRs) and activate spontaneous transient outward currents (STOCs), resulting in smooth muscle relaxation. Our findings that caffeine relaxes and hyperpolarizes murine gastric fundus smooth muscles and increases phospholamban (PLB) phosphorylation by Ca2+/calmodulin (CaM)-dependent protein kinase II (CaM kinase II) suggest that PLB phosphorylation by CaM kinase II participates in smooth muscle relaxation by increasing sarcoplasmic reticulum (SR) Ca2+ uptake and the frequencies of SR Ca2+ release events and STOCs. Thus, in the present study, we investigated the roles of CaM kinase II and PLB in SNP-induced relaxation of murine gastric fundus smooth muscles. SNP hyperpolarized and relaxed gastric fundus circular smooth muscles and activated CaM kinase II. SNP-induced CaM kinase II activation was prevented by KN-93. Ryanodine, tetracaine, 2-aminoethoxydiphenylborate, and cyclopiazonic acid inhibited SNP-induced fundus smooth muscle relaxation and CaM kinase II activation. The Ca2+-activated K+ channel blockers iberiotoxin and apamin inhibited SNP-induced hyperpolarization and relaxation. The soluble guanylate cyclase inhibitor 1H-[1,2,4]oxadiazolo-[4,3-alpha]quinoxalin-1-one inhibited SNP-induced relaxation and CaM kinase II activation. The membrane-permeable cGMP analog 8-bromo-cGMP relaxed gastric fundus smooth muscles and activated CaM kinase II. SNP increased phosphorylation of PLB at Ser16 and Thr17. Thr17 phosphorylation of PLB was inhibited by cyclopiazonic acid and KN-93. Ser16 and Thr17 phosphorylation of PLB was sensitive to 1H-[1,2,4]oxadiazolo-[4,3-alpha]quinoxalin-1-one. These results demonstrate a novel pathway linking the NO-soluble guanylyl cyclase-cGMP pathway, SR Ca2+ release, PLB, and CaM kinase II to relaxation in gastric fundus smooth muscles.
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Affiliation(s)
- Minkyung Kim
- Dept. of Physiology and Cell Biology, Univ. of Nevada School of Medicine, Anderson Bldg./MS352, Reno, NV 89557, USA
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Sathish V, Xu A, Karmazyn M, Sims SM, Narayanan N. Mechanistic basis of differences in Ca2+ -handling properties of sarcoplasmic reticulum in right and left ventricles of normal rat myocardium. Am J Physiol Heart Circ Physiol 2006; 291:H88-96. [PMID: 16461368 DOI: 10.1152/ajpheart.01372.2005] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
This study investigated Ca2+ -cycling properties of sarcoplasmic reticulum (SR) in right ventricle (RV) and left ventricle (LV) of normal rat myocardium. Intracellular Ca2+ transients and contractile function were monitored in freshly isolated myocytes from RV and LV. SR in RV displayed nearly fourfold lower rates of ATP-energized Ca2+ uptake in vitro than SR of LV. The Ca2+ concentration required for half-maximal activation of Ca2+ transport was nearly twofold higher in SR of RV. The lower Ca2+ -sequestering activity of SR in RV was accompanied by a matching decrement in Ca2+ -induced phosphoenzyme formation during the catalytic cycle of the Ca2+ -pumping ATPase (SERCA2). Western immunoblot analysis showed that protein levels of Ca2+ -ATPase and its inhibitor phospholamban (PLN) were only approximately 15% lower in SR of RV than in SR of LV. Coimmunoprecipitation experiments revealed that PLN-bound, functionally inert Ca2+ -ATPase molecules in SR of RV greatly exceed (> 50%) that in SR of LV. Endogenous Ca2+/calmodulin-dependent protein kinase-mediated phosphorylation of SR substrates did not abolish the huge disparity in SR Ca2+ pump function between RV and LV. Intracellular Ca2+ transients, evoked by electrical field stimulation, were significantly prolonged in RV myocytes compared with LV myocytes, mainly because of slow decay of intracellular Ca2+ concentration. The slow decay of intracellular Ca2+ concentration in RV and consequent decrease in the speed of RV relaxation may promote temporal synchrony of the end of diastole in RV and LV. The preponderance of functionally silent SR Ca2+ pumps in RV reflects a higher diastolic reserve required to protect and maintain RV function in the face of a sudden rise in afterload or resistance in the pulmonary circulation.
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Affiliation(s)
- V Sathish
- Department of Physiology and Pharmacology, University of Western Ontario, London, ON, Canada N6A 5C1
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Kim M, Cho SY, Han IS, Koh SD, Perrino BA. CaM kinase II and phospholamban contribute to caffeine-induced relaxation of murine gastric fundus smooth muscle. Am J Physiol Cell Physiol 2005; 288:C1202-10. [PMID: 15659716 DOI: 10.1152/ajpcell.00299.2004] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Caffeine has been shown to increase the Ca2+release frequency (Ca2+sparks) from the sarcoplasmic reticulum (SR) through ryanodine-sensitive stores and relax gastric fundus smooth muscle. Increased Ca2+store refilling increases the frequency of Ca2+release events and store refilling is enhanced by CaM kinase II (CaMKII) phosphorylation of phospholamban (PLB). These findings suggest that transient, localized Ca2+release events from the SR may activate CaMKII and contribute to relaxation by enhancing store refilling due to PLB Thr17 phosphorylation. To investigate this possibility, we examined the effects of caffeine on CaMKII, muscle tone, and PLB phosphorylation in murine gastric fundus smooth muscle. Caffeine (1 mM) hyperpolarized and relaxed murine gastric fundus smooth muscle and activated CaMKII. Ryanodine, tetracaine, or cyclopiazonic acid each prevented CaMKII activation and significantly inhibited caffeine-induced relaxation. The large-conductance Ca2+-activated K+channel blocker iberiotoxin, but not apamin, partially inhibited caffeine-induced relaxation. Caffeine-induced CaMKII activation increased PLB Thr17, but not PLB Ser16 phosphorylation. 3-Isobutyl-1-methylxanthine increased PLB Ser16 phosphorylation, but not PLB Thr17 phosphorylation. The CaMKII inhibitor KN-93 inhibited caffeine-induced relaxation and PLB Thr17 phosphorylation. These results show that caffeine-induced CaMKII activation and PLB phosphorylation play a role in the relaxation of gastric fundus smooth muscles.
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Affiliation(s)
- Minkyung Kim
- Department of Physiology and Cell Biology, Center of Biomedical Research Excellence, University of Nevada School of Medicine, Anderson Bldg./MS352, Reno, NV 89557, USA
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Jiang M, Xu A, Jones DL, Narayanan N. Coordinate downregulation of CaM kinase II and phospholamban accompanies contractile phenotype transition in the hyperthyroid rabbit soleus. Am J Physiol Cell Physiol 2004; 287:C622-32. [PMID: 15115706 DOI: 10.1152/ajpcell.00352.2003] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
This study investigated the effects of l-thyroxine-induced hyperthyroidism on Ca2+/calmodulin (CaM)-dependent protein kinase (CaM kinase II)-mediated sarcoplasmic reticulum (SR) protein phosphorylation, SR Ca2+pump (Ca2+-ATPase) activity, and contraction duration in slow-twitch soleus muscle of the rabbit. Phosphorylation of Ca2+-ATPase and phospholamban (PLN) by endogenous CaM kinase II was found to be significantly lower (30–50%) in soleus of the hyperthyroid compared with euthyroid rabbit. Western blotting analysis revealed higher levels of sarco(endo)plasmic reticulum Ca2+-ATPase (SERCA) 1 (∼150%) Ca2+pump isoform, unaltered levels of SERCA2 Ca2+pump isoform, and lower levels of PLN (∼50%) and δ-, β-, and γ-CaM kinase II (40 ∼ 70%) in soleus of the hyperthyroid rabbit. SR vesicles from hyperthyroid rabbit soleus displayed approximately twofold higher ATP-energized Ca2+uptake and Ca2+-stimulated ATPase activities compared with that from euthyroid control. The Vmaxof Ca2+uptake (in nmol Ca2+·mg SR protein−1·min−1: euthyroid, 818 ± 73; hyperthyroid, 1,649 ± 90) but not the apparent affinity of the Ca2+-ATPase for Ca2+(euthyroid, 0.97 ± 0.02 μM, hyperthyroid, 1.09 ± 0.04 μM) differed significantly between the two groups. CaM kinase II-mediated stimulation of Ca2+uptake by soleus muscle SR was ∼60% lower in the hyperthyroid compared with euthyroid. Isometric twitch force of soleus measured in situ was significantly greater (∼36%), and the time to peak force and relaxation time were significantly lower (∼30–40%), in the hyperthyroid. These results demonstrate that thyroid hormone-induced transition in contractile properties of the rabbit soleus is associated with coordinate downregulation of the expression and function of PLN and CaM kinase II and selective upregulation of the expression and function of SERCA1, but not SERCA2, isoform of the SR Ca2+pump.
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Affiliation(s)
- M Jiang
- Dept. of Physiology and Pharmacology, Health Science Center, The University of Western Ontario, London, Ontario, Canada N6A 5C1
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Rao MK, Xu A, Narayanan N. Glucocorticoid modulation of protein phosphorylation and sarcoplasmic reticulum function in rat myocardium. Am J Physiol Heart Circ Physiol 2001; 281:H325-33. [PMID: 11406500 DOI: 10.1152/ajpheart.2001.281.1.h325] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
To decipher the mechanism(s) underlying glucocorticoid action on cardiac contractile function, this study investigated the effects of adrenalectomy and dexamethasone treatment on the contents of sarcoplasmic reticulum (SR) Ca(2+)-cycling proteins, their phosphorylation by endogenous Ca(2+)/calmodulin-dependent protein kinase II (CaM kinase II), and SR Ca(2+) sequestration in the rat myocardium. Cardiac SR vesicles from adrenalectomized rats displayed significantly diminished rates of ATP-energized Ca(2+) uptake in vitro compared with cardiac SR vesicles from control rats; in vivo administration of dexamethasone to adrenalectomized rats prevented the decline in SR function. Western immunoblotting analysis showed that the relative protein amounts of ryanodine receptor/Ca(2+)-release channel, Ca(2+)-ATPase, calsequestrin, and phospholamban were neither diminished significantly by adrenalectomy nor elevated by dexamethasone treatment. However, the relative amount of SR-associated CaM kinase II protein was increased 2.5- to 4-fold in dexamethasone-treated rats compared with control and adrenalectomized rats. Endogenous CaM kinase II activity, as judged from phosphorylation of ryanodine receptor, Ca(2+)-ATPase, and phospholamban protein, was also significantly higher (50--80% increase) in the dexamethasone-treated rats. The stimulatory effect of CaM kinase II activation on Ca(2+) uptake activity of SR was significantly depressed after adrenalectomy and greatly enhanced after dexamethasone treatment. These findings identify the SR as a major target for glucocorticoid actions in the heart and implicate modification of the SR CaM kinase II system as a component of the mechanisms by which dexamethasone influences SR Ca(2+)-cycling and myocardial contraction.
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Affiliation(s)
- M K Rao
- Department of Physiology, The University of Western Ontario, London, Ontario, Canada N6A 5C1
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Gomes PA, Bassani RA, Bassani JW. Electric field stimulation of cardiac myocytes during postnatal development. IEEE Trans Biomed Eng 2001; 48:630-6. [PMID: 11396593 DOI: 10.1109/10.923781] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
Studies on cardiac cell response to electric field stimulation are important for understanding basic phenomena underlying cardiac defibrillation. In this work, we used a model of a prolate spheroidal cell in a uniform external field (Klee and Plonsey, 1976) to predict the threshold electric field (ET) for stimulation of isolated ventricular myocytes of rats at different ages. The model assumes that ET is primarily determined by cell shape and dimensions, which markedly change during postnatal development. Neonatal cells showed very high ET, which progressively decreased with maturation (experimental mean values were 29, 21, 13, and 5.9 and 6.3 V/cm for 3-6, 13-16, 20-21, 28-35, and 120-180 day-old rats, respectively, P < 0.001; theoretical values were 24, 18, 11, 9, and 6 V/cm, respectively). Estimated maximum membrane depolarization at threshold (deltaVT approximately equals 35 mV, under our experimental conditions) was reasonably constant during development, except for cells from 1-mo-old animals, in which deltaVT was lower than at other ages. We conclude that the model reasonably correlates ET with cell geometry and size in most cases. Our results might be relevant for the development of efficient procedures for defibrillation of pediatric patients.
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Affiliation(s)
- P A Gomes
- Núcleo de Pesquisas Tecnologicas, Universidade de Mogi das Cruzes, SP, Brazil
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Jiang M, Xu A, Tokmakejian S, Narayanan N. Thyroid hormone-induced overexpression of functional ryanodine receptors in the rabbit heart. Am J Physiol Heart Circ Physiol 2000; 278:H1429-38. [PMID: 10775119 DOI: 10.1152/ajpheart.2000.278.5.h1429] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Modifications in the Ca(2+)-uptake and -release functions of the sarcoplasmic reticulum (SR) may be a major component of the mechanisms underlying thyroid state-dependent alterations in heart rate, myocardial contractility, and metabolism. We investigated the influence of hyperthyroid state on the expression and functional properties of the ryanodine receptor (RyR), a major protein in the junctional SR (JSR), which mediates Ca(2+) release to trigger muscle contraction. Experiments were performed using homogenates and JSR vesicles derived from ventricular myocardium of euthyroid and hyperthyroid rabbits. Hyperthyroidism, with attendant cardiac hypertrophy, was induced by the injection of L-thyroxine (200 microg/kg body wt) daily for 7 days. Western blotting analysis using cardiac RyR-specific antibody revealed a significant increase (>50%) in the relative amount of RyR in the hyperthyroid compared with euthyroid rabbits. Ca(2+)-dependent, high-affinity [(3)H]ryanodine binding was also significantly greater ( approximately 40%) in JSR from hyperthyroid rabbits. The Ca(2+ )sensitivity of [(3)H]ryanodine binding and the dissociation constant for [(3)H]ryanodine did not differ significantly between euthyroid and hyperthyroid hearts. Measurement of Ca(2+)-release rates from passively Ca(2+)-preloaded JSR vesicles and assessment of the effect of RyR-Ca(2+)-release channel (CRC) blockade on active Ca(2+)-uptake rates revealed significantly enhanced (>2-fold) CRC activity in the hyperthyroid, compared with euthyroid, JSR. These results demonstrate overexpression of functional RyR in thyroid hormone-induced cardiac hypertrophy. Relative abundance of RyR may be responsible, in part, for the changes in SR Ca(2+) release, cytosolic Ca(2+) transient, and cardiac systolic function associated with thyroid hormone-induced cardiac hypertrophy.
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Affiliation(s)
- M Jiang
- Department of Physiology, The University of Western Ontario, London, Ontario, Canada N6A 5C1
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