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Impulse Propagation (impulse + propagation)
Selected AbstractsElectroanatomic Analysis of Sinus Impulse Propagation in Normal Human AtriaJOURNAL OF CARDIOVASCULAR ELECTROPHYSIOLOGY, Issue 1 2002ROBERTO DE PONTI M.D. Sinus Impulse Propagation in Normal Human Atria.Introduction: Better understanding of atrial propagation during sinus rhythm (SR) in normal hearts under the most normal physiologic conditions may be propaedeutic to pathophysiologic studies of complex atrial arrhythmias. In this study, qualitative and quantitative analyses of sinus impulse propagation in both atria were performed by electroanatomic mapping in patients with no organic heart disease who were undergoing an electrophysiologic procedure. Methods and Results: Seven patients (5 men and 2 women; age 37 ± 11 years) undergoing ablation of a left-sided accessory pathway were considered. Associated heart disease and coexisting atrial arrhythmias were excluded. After obtaining informed consent, electroanatomic mapping of both atria was performed during SR using a nonfluoroscopic system in the postablation phase. Mapping was accomplished in all patients with no complications. Qualitative analysis showed that sinus impulse propagation gives a reproducible activation pattern with minor individual variations. During interatrial propagation, two breakthroughs (anterior and posterior) in the left atrium are observed in the majority of cases. The anterior breakthrough, which reflects conduction over Bachmann's bundle, is predominant and shows a peculiar "preexcitation-like" endocardial activation pattern. Quantitative analysis showed minimal individual variations of propagation time intervals. Atria are activated simultaneously for 65% ± 9% of the duration of the atrial systolic time interval. Conclusion: In normal humans, electroanatomic mapping of SR identifies a typical and reproducible propagation pattern during SR. Bachmann's bundle plays the most important role in interatrial propagation. Atria are activated simultaneously by sinus impulse for a relevant portion of the systolic time interval. [source] Electroanatomic Analysis of Sinus Impulse Propagation in Normal Human AtriaJOURNAL OF CARDIOVASCULAR ELECTROPHYSIOLOGY, Issue 1 2002MELVIN M. SCHEINMAN M.D. [source] Deficiency of electroneutral K+,Cl, cotransporter 3 causes a disruption in impulse propagation along peripheral nervesGLIA, Issue 13 2010Yuan-Ting Sun Abstract Nerve conduction requires the fine tuning of ionic currents through delicate interactions between axons and Schwann cells. The K+,Cl, cotransporter (KCC) family includes four isoforms (KCC1,4) that play an important role in the maintenance of cellular osmotic homeostasis via the coupled electroneutral movement of K+ and Cl, with concurrent water flux. Mutation in SLC12A6 gene encoding KCC3 results in an autosomal recessive disease, known as agenesis of the corpus callosum associated with peripheral neuropathy. Nevertheless, the role of KCC3 in nerve function remains a puzzle. In this study, the microscopic examination of KCC isoforms expressed in peripheral nerves showed high expression of KCC2,4 in nodal segments of the axons and in the perinucleus and microvilli of Schwann cells. The KCC inhibitor [[(dihydroindenyl)oxy]alkanoic acid] but not the Na+,K+,2Cl, -cotransport inhibitor (bumetanide) dose-dependently suppressed the amplitude and area of compound muscle action potential, indicating the involvement of KCC activity in peripheral nerve conduction. Furthermore, the amplitude and area under the curve were smaller, and the nerve conduction velocity was slower in nerves from KCC3,/, mice than in nerves from wild-type mice, while the expression pattern of KCC2 and KCC4 was similar in KCC3 kockout and wild-type strains. KCC3,/, mice also manifested a prominent motor deficit in the beam-walking test. This is the first study to demonstrate that the K+,Cl, cotransporter activity of KCC3 contributes to the propagation of action potentials along peripheral nerves. © 2010 Wiley-Liss, Inc. [source] Development of an Optrode for Intramural Multisite Optical Recordings of Vm in the HeartJOURNAL OF CARDIOVASCULAR ELECTROPHYSIOLOGY, Issue 11 2003JONATHAN L. BYARS M.S. Introduction: Optical mapping of transmembrane potential (Vm) is an important tool in the investigation of impulse propagation in the heart. It provides valuable information about spatiotemporal changes of Vm that cannot be obtained by other techniques, but it presently is limited to measurements from the heart surfaces. Therefore, the goal of this work was to develop a technique for intramural multisite optical measurements of Vm using fiberoptic technology. Methods and Results: An optrode, a bundle of thin optical fibers, was developed for measuring intramural optical signals at multiple sites in the heart. The optrode consisted of seven fibers with diameter of 225 ,m arranged in a hexagonal pattern that were used to deliver excitation light to the myocardium, to collect the emitted fluorescence, and to project the light onto a 16 × 16 array of photodiode detectors. Rabbit hearts were stained with the Vm -sensitive dye RH-237. Fluorescence was excited using a 100-W Hg lamp. Intramural action potentials were recorded at multiple sites separated by 2 mm inside the left ventricle. Signal-to-noise (RMS) ratio was 21.2 ± 12 (n = 7) without averaging or ratiometry and with negligible cross-talk (<1.9%) between the neighboring photodiodes. The size of the recording area for an individual fiber was estimated at approximately 0.8 mm. Conclusion: These data demonstrate feasibility of multisite transmural measurements of Vm without signal averaging and ratiometry. This technique might become useful in studies of transmural impulse conduction during arrhythmias and defibrillation. (J Cardiovasc Electrophysiol, Vol. 14, pp. 1196-1202, November 2003) [source] Electroanatomic Analysis of Sinus Impulse Propagation in Normal Human AtriaJOURNAL OF CARDIOVASCULAR ELECTROPHYSIOLOGY, Issue 1 2002ROBERTO DE PONTI M.D. Sinus Impulse Propagation in Normal Human Atria.Introduction: Better understanding of atrial propagation during sinus rhythm (SR) in normal hearts under the most normal physiologic conditions may be propaedeutic to pathophysiologic studies of complex atrial arrhythmias. In this study, qualitative and quantitative analyses of sinus impulse propagation in both atria were performed by electroanatomic mapping in patients with no organic heart disease who were undergoing an electrophysiologic procedure. Methods and Results: Seven patients (5 men and 2 women; age 37 ± 11 years) undergoing ablation of a left-sided accessory pathway were considered. Associated heart disease and coexisting atrial arrhythmias were excluded. After obtaining informed consent, electroanatomic mapping of both atria was performed during SR using a nonfluoroscopic system in the postablation phase. Mapping was accomplished in all patients with no complications. Qualitative analysis showed that sinus impulse propagation gives a reproducible activation pattern with minor individual variations. During interatrial propagation, two breakthroughs (anterior and posterior) in the left atrium are observed in the majority of cases. The anterior breakthrough, which reflects conduction over Bachmann's bundle, is predominant and shows a peculiar "preexcitation-like" endocardial activation pattern. Quantitative analysis showed minimal individual variations of propagation time intervals. Atria are activated simultaneously for 65% ± 9% of the duration of the atrial systolic time interval. Conclusion: In normal humans, electroanatomic mapping of SR identifies a typical and reproducible propagation pattern during SR. Bachmann's bundle plays the most important role in interatrial propagation. Atria are activated simultaneously by sinus impulse for a relevant portion of the systolic time interval. [source] Simultaneous Optical Mapping of Transmembrane Potential and Intracellular Calcium in Myocyte CulturesJOURNAL OF CARDIOVASCULAR ELECTROPHYSIOLOGY, Issue 5 2000VLADIMIR G. FAST Ph.D. Simultaneous Mapping of Vm and Cai2+. Introduction: Fast spatially resolved measurements of transmembrane potential (Vm) and intracellular calcium (Cai2+) are important for studying mechanisms of arrhythmias and defibrillation. The goals of this work were (1) to develop an optical technique for simultaneous multisite optical recordings of Vm and Cai2+, and (2) to determine the relationship between Vm and Cai2+ during normal impulse propagation in myocyte cultures. Methods and Results: Monolayers of neonatal rat myocytes were stained with fluorescent dye RH-237 (Vm) and Fluo-3AM (Cai2+). Both dyes were excited at the same wavelength range. The emitted fluorescent was optically separated into components corresponding to changes in Vm, and Cai2+ and measured using two 16 × 16 photodiode arrays at a spatial resolution of up to 27.5 ,m per diode and sampling rate of 2.5 kHz. The optical setup was adjusted so that there was no optical cross-talk between the two types of measurements, which was validated in experiments involving staining with either RH-237 or Fluo-3. The amplitude of Fluo-3 signals rapidly decreased during experiments due to dye leakage. Dye leakage was substantially reduced by application of 1 mM probenecid, a blocker of organic anion transport, which had no effect on action potential duration and only minor effect on conduction velocity. In double-stained preparations, during regular pacing Cai2+ transients had a rise time of 14.2 ± 2 msec, and they followed Vm upstrokes with a delay of 5.3 ± 1 msec (n = 9). Durations of Vm, and Cai2+ transients determined at 50% level of signal recovery were 54.6 ± 10 msec and 136 ± 8 msec, respectively. Application of 2 ,M nifedipine reduced the amplitude and duration of Cai2+ transients without significantly affecting conduction velocity. Conclusion: The results demonstrate feasibility of simultaneous optical recordings of Vm and Cai2+ transients with high spatial and temporal resolution. [source] Electrical and Structural Remodeling in Left Ventricular Hypertrophy,A Substrate for a Decrease in QRS Voltage?ANNALS OF NONINVASIVE ELECTROCARDIOLOGY, Issue 3 2007Ljuba Bacharova M.D., M.B.A., Ph.D. Electrical remodeling in advanced stages of cardiovascular diseases creates a substrate for triggering and maintenance of arrhythmias. The electrical remodeling is a continuous process initiated already in the early stages of cardiological pathology. The aim of this opinion article was to discuss the changes in electrical properties of myocardium in left ventricular hypertrophy (LVH), with special focus on its early stage, as well as their possible reflection in the QRS amplitude of the electrocardiogram. It critically appraises the classical hypothesis related to the QRS voltage changes in LVH. The hypothesis of the relative voltage deficit is discussed in the context of supporting evidence from clinical studies, animal experiments, and simulation studies. The underlying determinants of electrical impulse propagation which may explain discrepancies between "normal" ECG findings and increased left ventricular size/mass in LVH are reviewed. [source] | ||||||||||