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Cardiac Electrophysiology (cardiac + electrophysiology)
Selected AbstractsEffects of Estrogen on Cardiac Electrophysiology in Female MiceJOURNAL OF CARDIOVASCULAR ELECTROPHYSIOLOGY, Issue 3 2002SAMIR SABA M.D. Estrogen and Cardiac Electrophysiology.Introduction: Understanding the molecular mechanisms that underlie gender- and hormonal-related differences in susceptibility to cardiac arrhythmias has been hampered by the lack of a suitable animal model. We examined the effect of hormonal status on the electrophysiologic (EP) properties of the mouse heart in an in vivo, closed chest model. Methods and Results: Fifty-three female C57/J mice aged 10 to 12 weeks were studied. Thirty-six mice underwent bilateral ovariectomies; 18 received estrogen (OVX + E) and 18 received placebo (OVX). Seventeen female mice underwent only sham surgery. All animals underwent in vivo EP studies. Select EP parameters were measured after quinidine treatment. Data were analyzed by a blinded observer. Compared with the intact female mice, the PR and AH intervals were significantly shorter in the OVX mice, and these parameters normalized with estrogen replacement (PR = 45.9 ± 4.5 msec in the intact mice, 42.1 ± 4.3 msec in the OVX group, and 46.9 ± 3.5 msec in the OVX + E group, P < 0.005; AH = 36.5 ± 4.9 msec in the intact mice, 34.4 ± 4.7 msec in the OVX group, and 38.8 ± 2.7 msec in the OVX + E group, P = 0.03). The right ventricular effective refractory period was significantly shorter in the OVX mice versus the intact mice, and this also normalized with estrogen replacement. Hormonal status did not significantly affect any other EP variable, including QT interval. Conclusion: In female mice, estrogen prolongs AV nodal conduction and the right ventricular effective refractory period. Taken together, these data suggest that hormonal status affects aspects of cardiac EP function. Future application of this mouse model will be helpful in determining the molecular pathways that mediate hormonal differences in cardiac EP. [source] Atrial fibrillation and bisphosphonate therapyJOURNAL OF BONE AND MINERAL RESEARCH, Issue 1 2010Michael Pazianas Abstract Bisphosphonates are the most commonly used treatment for osteoporosis and have proven efficacy in the reduction of vertebral and nonvertebral fractures. Recently, concerns have been raised about a possible association between bisphosphonate therapy and atrial fibrillation (AF) following the report of a significant increase in risk of serious AF in women treated with zoledronic acid in the HORIZON study. Subsequent studies have produced conflicting results but have not excluded the possibility of such an association. Currently there is no direct evidence that bisphosphonates exert either acute or chronic effects on cardiac electrophysiology. Nevertheless, altered intracellular electrolyte homeostasis and proinflammatory, profibrotic, and antiangiogenic effects provide potential mechanisms by which atrial conduction could be affected in patients treated with bisphosphonates. In studies in which an increase in risk of AF has been identified, there is no evidence that this translates into increased mortality or increased risk of stroke, and the risk-benefit balance of bisphosphonate therapy in patients with osteoporosis and other forms of metabolic bone disease remains strongly positive. © 2010 American Society for Bone and Mineral Research [source] An Unusual Complication of Sinus Arrest Following Right-Sided Stellate Ganglion Block: A Case ReportPAIN PRACTICE, Issue 3 2004Ashok K. Saxena MD Abstract: We present a case of a 29-year-old female patient who had presented to us for the management of her chronic right shoulder,hand pain and developed a sinus arrest following a right-sided stellate ganglion block (RSGB). This patient on receiving a diagnostic RSGB via the anterior paratracheal (C6) approach developed sinus arrest followed by apnea and unconsciousness. On institution of resuscitative measures involving tracheal intubation, positive pressure ventilation, cardiac massage, and intravenous atropine, spontaneous cardiac activity recovered in about 3 minutes. Other signs and symptoms resolved fully in a total of 10 minutes. She had persistent postural hypotension lasting for about 24 hours requiring bed rest and was discharged about 36 hours after the procedure, without any adverse sequelae. As the sinus node is supplied by the right-sided sympathetic chain, its blockade probably resulted in unopposed parasympathetic activity leading to asystole. Available evidence of the role of right stellate ganglion in regulation of cardiac electrophysiology and functioning is also discussed. [source] Multichannel mapping of fetal magnetocardiogram in an unshielded hospital settingPRENATAL DIAGNOSIS, Issue 5 2005Donatella Brisinda Abstract Objectives To evaluate the feasibility of unshielded in-hospital multichannel mapping of fetal magnetocardiogram (FMCG), with a 36-channel system for standard adult magnetocardiographic (MCG) recordings, and its reliability according to the recommended standards for FMCG. Methods FMCG was ambulatory mapped with a 36-channel MCG system, in six normal pregnancies at different gestational ages. MCG analysis included adaptive digital filtering of 50 Hz, signal averaging, reconstruction of magnetic field distribution (MFD) and source localization. Fixed Point Independent Component Analysis algorithm (FastICA) was used to reconstruct the FMCG, separating them from maternal contamination and noise. Results The quality of FMCG recorded after the 32nd gestational week and reconstructed with FastICA was close to FMCG obtained in shielded rooms, and good enough to measure cardiac intervals and heart rate variability parameters. In two cases, reconstruction of the MFD during the QRS allowed three-dimensional localization of ventricular sources. Conclusions A first demonstration has been given that multichannel mapping of FMCG can be performed in unshielded clinical environments, with resolution good enough for contactless assessment of fetal cardiac electrophysiology. FastICA processing on unshielded FMCG, recorded after the 32nd week, provided beat-to-beat analysis and heart rate variability assessment. Further work is needed to improve signal reconstruction in early pregnancy. Copyright © 2005 John Wiley & Sons, Ltd. [source] Electromechanics of Cardiac Tissue: A Unified Approach to the Fully Coupled Excitation-Contraction ProblemPROCEEDINGS IN APPLIED MATHEMATICS & MECHANICS, Issue 1 2009Serdar Göktepe This contribution is concerned with a new, unified finite element approach to the fully coupled problem of cardiac electromechanics. In contrast to the existing numerical approaches suggested in the literature; to the best of our knowledge, for the first time, we propose a fully implicit, purely finite-element-based approach to the coupled problem. The system of coupled algebraic equations obtained by simultaneous linearization of non-linear weighted residual terms is solved monolithically. The put forward modular algorithmic framework leads to an unconditionally stable and geometrically flexible structure that can readily be extended towards complex ionic models of cardiac electrophysiology. The performance of the proposed approach is illustrated by the coupled electromechanical analysis of a biventricular generic heart model. (© 2009 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Challenges Facing Validation of Noninvasive Electrical Imaging of the HeartANNALS OF NONINVASIVE ELECTROCARDIOLOGY, Issue 1 2005Martyn P. Nash Ph.D. Noninvasive imaging of regional cardiac electrophysiology remains an elusive target. Such imaging is still in its infancy, particularly in comparison to structural imaging modalities such as magnetic resonance imaging (MRI), x-ray computed tomography (CT), and ultrasound. We present an overview of noninvasive ECG imaging, and the challenges and successes of the various techniques across a range of applications. Unlike MRI and CT, reconstructing cardiac electrophysiology from remote body surface measurements is a highly ill-posed problem. We therefore first review the theoretical considerations and associated algorithms that are used to address this issue. We then focus on the important issue of validation, and review and contrast recent advances in this area. Efforts to validate ECG inverse procedures using a modeling-based approach are addressed first. We then discuss various experimental studies that have been conducted to provide appropriate data for robust validations. We present new data that are simultaneously recorded from dense arrays of electrodes on the epicardium and body surface of anesthetized pigs during sinus rhythm, ventricular pacing, and regional ischemia. These data have been obtained specifically to help validate inverse ECG procedures, and form a useful supplement to recent clinical validation studies. Finally, clinical applications and outstanding issues regarding noninvasive imaging of regional cardiac electrophysiology are addressed. [source] EFFECT OF BENAZEPRIL ON HEART RATE TURBULENCE IN PATIENTS WITH DILATED CARDIOMYOPATHYCLINICAL AND EXPERIMENTAL PHARMACOLOGY AND PHYSIOLOGY, Issue 7 2007Jiang-Hua Zhong SUMMARY 1Heart rate (HR) turbulence describes short-term sinus rhythmic fluctuation after a single premature ventricular beat. Turbulence onset (TO) and turbulence slope (TS) are two essential parameters in HR turbulence. Turbulence onset and TS have been used to evaluate cardiac autonomic nerve function. 2In the present study, we measured the HR turbulence in dilated cardiomyopathy (DCM) and determined the possible role of benazepril, an angiotensin-converting enzyme inhibitor (ACEI), on these parameters. There were three groups: control, DCM and DCM treated with benazepril. The control group consisted of normal subjects with PVB, but no structural heart disease. Ambulatory electrocardiogram, blood pressure and echocardiography were analysed. 3There was an increase in TO and a decrease in TS in DCM patients. Benazepril treatment (10 mg/day, p.o.) reduced those changes. There were no significant differences in blood pressure and left ventricular ejection fraction (LVEF) between DCM patients and DCM patients treated with benazepril. 4Linear regression analysis showed that TO was negatively correlated with LVEF, whereas TS was positively correlated with LVEF, in the DCM group. After benazepril treatment, the correlations between TO and TS and LVEF disappeared. 5It is concluded that the TO and TS of HR turbulence are altered in patients with DCM. These alterations indicate a dysfunction of the autonomic control of cardiac electrophysiology in DCM patients. Although TO and TS are correlated with LVEF in DCM patients, the effect of benazepril in improving HR turbulence parameters is not a result of its action on heart function, which suggests a new beneficial effect of ACEI in the treatment of DCM patients. [source] | ||||||||||