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Conduction Properties (conduction + property)
Selected AbstractsConduction Properties of the Crista Terminalis and Its Influence on the Right Atrial Activation Sequence in Patients with Typical Atrial FlutterPACING AND CLINICAL ELECTROPHYSIOLOGY, Issue 2 2002HIROSHIGE YAMABE YAMABE, H., et al.: Conduction Properties of the Crista Terminalis and Its Influence on the Right Atrial Activation Sequence in Patients with Typical Atrial Flutter. The conduction properties of the crista terminalis (CT) and its influence on the right atrial activation sequence were analyzed in 14 patients with typical atrial flutter (AF). Atrial mapping was performed with 35 points of the right atrium during typical AF and during atrial pacing performed after linear ablation of inferior vena cava-tricuspid annulus (IVCTA) isthmus. Atrial pacing was delivered from the septal isthmus at cycle lengths of 600 ms and the tachycardia cycle length (TCL). The right atrial activation sequence and the conduction interval (CI) from the septal to lateral portion of the IVC-TA isthmus were analyzed. During AF, the conduction block line (CBL) (detected by the appearance of double potentials along the CT and craniocaudal activation on the side anterior to CT) was observed along the CT in all patients. The TCL and CI during AF were 254 ± 19 and 207 ± 14 ms, respectively. During pacing at a cycle length of 600 ms, the CBL was observed along the CT in four patients, however, a short-circuiting activation across the CT was observed in the remaining ten patients. The CI during pacing at 600 ms was 134 ± 38 ms, shorter than that during AF (P < .0001). During pacing at the TCL, the CBL was observed along the CT in all patients. The presence of the CBL along the CT prevented a short-circuiting activation across the CT and resulted in the same right atrial activation as observed during AF. With the formation of the CBL, the CI significantly increased to 206 ± 17 ms and was not different from that during AF. These data suggest that the conduction block along the CT is functional. It was presumed that presence of conduction block at the CT has some relevance to the initiation of typical AF though it was not confirmed. [source] ChemInform Abstract: Understanding the p-Type Conduction Properties of the Transparent Conducting Oxide CuBO2: A Density Functional Theory Analysis.CHEMINFORM, Issue 51 2009David O. Scanlon Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a "Full Text" option. The original article is trackable via the "References" option. [source] Electrical Conduction Properties of Sr-Doped LaPO4 and CePO4 under Oxidizing and Reducing Conditions.CHEMINFORM, Issue 29 2005Naoto Kitamura Abstract For Abstract see ChemInform Abstract in Full Text. [source] A New Fluorite Type Compound Pb5Bi17X5O43: Synchrotron and Neutron Structure Determination (X: P) and Conduction Properties (X: P, V and As).CHEMINFORM, Issue 3 2003Pascal Roussel Abstract For Abstract see ChemInform Abstract in Full Text. [source] Scn3b knockout mice exhibit abnormal sino-atrial and cardiac conduction propertiesACTA PHYSIOLOGICA, Issue 1 2010P. Hakim Abstract Aim:, In contrast to extensive reports on the roles of Nav1.5 , -subunits, there have been few studies associating the , -subunits with cardiac arrhythmogenesis. We investigated the sino-atrial and conduction properties in the hearts of Scn3b,/, mice. Methods:, The following properties were compared in the hearts of wild-type (WT) and Scn3b,/, mice: (1) mRNA expression levels of Scn3b, Scn1b and Scn5a in atrial tissue. (2) Expression of the ,3 protein in isolated cardiac myocytes. (3) Electrocardiographic recordings in intact anaesthetized preparations. (4) Bipolar electrogram recordings from the atria of spontaneously beating and electrically stimulated Langendorff-perfused hearts. Results:,Scn3b mRNA was expressed in the atria of WT but not Scn3b,/, hearts. This was in contrast to similar expression levels of Scn1b and Scn5a mRNA. Immunofluorescence experiments confirmed that the ,3 protein was expressed in WT and absent in Scn3b,/, cardiac myocytes. Lead I electrocardiograms from Scn3b,/, mice showed slower heart rates, longer P wave durations and prolonged PR intervals than WT hearts. Spontaneously beating Langendorff-perfused Scn3b,/, hearts demonstrated both abnormal atrial electrophysiological properties and evidence of partial or complete dissociation of atrial and ventricular activity. Atrial burst pacing protocols induced atrial tachycardia and fibrillation in all Scn3b,/, but hardly any WT hearts. Scn3b,/, hearts also demonstrated significantly longer sinus node recovery times than WT hearts. Conclusion:, These findings demonstrate, for the first time, that a deficiency in Scn3b results in significant atrial electrophysiological and intracardiac conduction abnormalities, complementing the changes in ventricular electrophysiology reported on an earlier occasion. [source] Simultaneous IR Material Recognition and Conductivity Mapping by Nanoscale Near-Field Microscopy,ADVANCED MATERIALS, Issue 17 2007J. Huber IR scattering-type near-field microscopy is applied to simultaneously map material composition and conduction properties in cross-sectional samples of industrial bipolar and metal-oxide- semiconductor devices with nanoscale spatial resolution. Within a single mid-IR image, all relevant materials such as metals, Si, Si3N4, and oxides can be identified by material-specific amplitude and phase contrasts. [source] Conduction Characteristics at the Crista Terminalis During Onset of Pulmonary Vein Atrial FibrillationJOURNAL OF CARDIOVASCULAR ELECTROPHYSIOLOGY, Issue 8 2004SIMON P. FYNN M.D. Introduction: Focal atrial fibrillation (AF) may initiate with an irregular rapid burst of atrial ectopic (AE) activity from a pulmonary vein (PV) focus, but how AF is maintained it is not known. The crista terminalis (CT) is an important line of block in atrial flutter (AFL), but its role in AF has not been determined. The aim of this study was to examine the conduction properties of the CT during onset of AF. Methods and Results: In 10 patients (mean age 38 ± 8 years), we analyzed conduction across the CT during onset of focal AF from an arrhythmogenic PV and during pacing from the same PV at cycle lengths of 700 and 300 ms. A 20-pole catheter was positioned on the CT using intracardiac echocardiography. In 10 control patients with no history of AF, we analyzed conduction across the CT during pacing from the distal coronary sinus at 700 and 300 ms. In all 10 AF patients, AF was initiated with 1 to 9 AE beats (median 5) from a PV. During sinus rhythm, there were no split components (SC) recorded on the CT. During PV AE activity, discrete SC were recorded on the CT in all patients over 6.3 ± 0.9 bipoles (3.7 ± 0.3 cm). Maximal splitting of SC was 66 ± 31 ms (37,139). There was an inverse relationship between AE coupling intervals and the degree of splitting between SC in all patients. Degeneration to AF was preceded by progressive decrement across the CT. SC were recorded during PV pacing at 700 and 300 ms (maximal distance between SC of 24 ± 3 ms and 43 ± 5 ms, respectively, P < 0.001). Maximum SC at CT in controls was 13 ± 8 ms at 700 ms (P = 0.06 vs AF patients) and 16 ± 9 ms at 300 ms (P < 0.01 vs AF patients). Conclusion: (1) These observations provide evidence of anisotropic, decremental conduction across the CT during onset of focal AF and during pacing from the same PV. A line of functional conduction block develops along this anatomic structure (CT). Whether this line of block acts as an initiator of AF or simply contributes passively to nonuniform fibrillatory conduction is unknown. (2) In some patients with focal AF, development of conduction block along the CT may provide a substrate for typical AFL. [source] Maturational Atrioventricular Nodal Physiology in the MouseJOURNAL OF CARDIOVASCULAR ELECTROPHYSIOLOGY, Issue 5 2000COLIN T. MAGUIRE B.S. Mouse AV Nodal Maturation. Introduction: Dual AV nodal physiology is characterized by discontinuous conduction from the atrium to His bundle during programmed atrial extrastimulus testing (A2V2 conduction curves), AV nodal echo beats, and induction of AV nodal reentry tachycardia (AVNRT). The purpose of this study was to characterize in vivo murine maturational AV nodal conduction properties and determine the frequency of dual AV nodal physiology and inducible AVNRT. Methods and Results: A complete transvenous in vivo electrophysiologic study was performed on 30 immature and 19 mature mice. Assessment of AV nodal conduction included (1) surface ECG and intracardiac atrial and ventricular electrograms; (2) decremental atrial pacing to the point of Wenckebach block and 2:1 conduction; and (3) programmed premature atrial extrastimuli to determine AV effective refractory periods (AVERP), construct A2V2 conduction curves, and attempt arrhythmia induction. The mean Wenckebach block interval was 73 ± 12 msec, 2:1 block pacing cycle length was 61 ± 11 msec, and mean AVERP100 was 54 ± 11 msec. The frequency of dual AV nodal physiology increased with chronologic age, with discontinuous A2V2, conduction curves or AV nodal echo heats in 27% of young mice < 8 weeks and 58% in adult mice (P = 0.03). Conclusion: These data suggest that mice, similar to humans, have maturation of AV nodal physiology, hut they do not have inducible AVNRT. Characterization of murine electrophysiology may be of value in studying genetically modified animals with AV conduction abnormalities. Furthermore, extrapolation to humans may help explain the relative rarity of AVNRT in the younger pediatric population. [source] Patterns of Accelerated Junctional Rhythm During Slow Pathway Catheter Ablation for Atrioventricular Nodal Reentrant Tachycardia: Temperature Dependence, Prognostic Value, and Insights into the Nature of the Slow PathwayJOURNAL OF CARDIOVASCULAR ELECTROPHYSIOLOGY, Issue 3 2000ALAN B. WAGSHAL M.D. Slow Pathway Accelerated Junctional Rhythm. Introduction: Although accelerated junctional rhythm (AJR) is a knuwn marker for successful slow pathway (SP) ablation sites. AJR may just be a regional effect of the anisotropic conduction properties of this area of the heart. We believe that detailed assessment of the AJR might provide insight into the SP specificity of this AJR and perhaps the nature of the SP itself. Methods and Results: Our ablation protocol consisted of 30-second, 70°C temperature-controlled ablation pulses with assessment after each pulse. Serial booster ablations were performed at the original successful site and at least 2 to 3 nearby sites to assess for residual AJR after the procedure in 50 consecutive SP ablations. We defined three distinct patterns of AJR: continuous AJR that persisted until the end of energy delivery (group 1, 25 patients); alternating or "stuttering" AJR that persisted throughout energy delivery (group II, 9 patients); and AJR that ended abruptly during energy delivery (group III, 16 patients). Mean ablation temperatures in the three groups was 57°± 5°C, 54°± 5°C, and 63°± 5°C, respectively (P = 0.0002 for groups I and II vs group III). Ten of 34 (29%) patients in groups I and II ("low-temperature ablation") exhibited residual SP (jump and/or single echo heats) despite tachycardia noninducibility, and 25 of 34 (73%) patients had residual AJR during the booster ablations, but neither of these was seen in any group III patients. Conclusion: Ablation temperature correlates with the pattern of AJR produced during SP ablation. That higher temperature lesions simultaneously abolish all SP activity as well as the focus of AJR suggests that this AJR is specific for the SP and is not a nonspecific regional effect. [source] Radiation-induced conduction block: Resolution following anticoagulant therapyMUSCLE AND NERVE, Issue 5 2005Oscar Soto MD Abstract Neurophysiologic studies documented proximal conduction blocks in a patient harboring a delayed radiation-induced brachial plexopathy. Since anticoagulants have been reported to be beneficial in radiation-induced neuropathies, the patient was started on acenocumarol. After 3 months of treatment there was significant improvement of clinical deficits, which correlated with resolution of conduction blocks. This observation suggests that ischemic nerve injury leading to disruption of the conduction properties of motor axons contributes to the pathogenesis of delayed radiation-induced peripheral nerve injuries. Muscle Nerve, 2005 [source] Latent Atriofascicular Pathway Participating in a Wide Complex Tachycardia: Differentiation from Ventricular TachycardiaPACING AND CLINICAL ELECTROPHYSIOLOGY, Issue 12 2006MOHAMMAD V. JORAT M.D. Accessory pathways with anterograde decremental conduction properties usually are characterized by presence of antegrade preexcitation during atrial pacing. We report a 38-year-old man with frequent episodes of palpitation. No evidence of ventricular preexcitation was seen during sinus rhythm or atrial pacing. All electrophysiologic maneuvers were compatible with an antidromic tachycardia using atriofascicular pathway as the antegrade limb and the atrioventricular nodal pathway as retrograde limb. Radiofrequency ablation at recording site of accessory pathway potential resulted in cure of tachycardia with no recurrence during 3-month follow-up. This report indicated that atriofascicular pathway-mediated tachycardia should be considered in differential diagnosis of all cases of wide complex tachycardia with left bundle branch morphology and left axis. [source] Transgenic neuronal nitric oxide synthase expression induces axotomy-like changes in adult motoneuronsTHE JOURNAL OF PHYSIOLOGY, Issue 18 2010Fernando Montero Dysregulation of protein expression, function and/or aggregation is a hallmark of a number of neuropathological conditions. Among them, upregulation and/or de novo expression of the neuronal isoform of nitric oxide (NO) synthase (nNOS) commonly occurs in diverse neurodegenerative diseases and in axotomized motoneurons. We used adenoviral (AVV) and lentiviral (LVV) vectors to study the effects of de novo nNOS expression on the functional properties and synaptic array of motoneurons. AVV-nNOS injection into the genioglossus muscle retrogradely transduced neonatal hypoglossal motoneurons (HMNs). Ratiometric real-time NO imaging confirmed that transduced HMNs generated NO gradients in brain parenchyma (space constant: ,12.3 ,m) in response to a glutamatergic stimulus. Unilateral AVV-nNOS microinjection in the hypoglossal nucleus of adult rats induced axotomy-like changes in HMNs. Specifically, we found alterations in axonal conduction properties and the recruitment order of motor units and reductions in responsiveness to synaptic drive and in the linear density of synaptophysin-positive puncta opposed to HMN somata. Functional alterations were fully prevented by chronic treatment with nNOS or soluble guanylyl cyclase inhibitors. Synaptic and functional changes were also completely avoided by prior intranuclear injection of a neuron-specific LVV system for miRNA-mediated nNOS knock-down (LVV-miR-shRNA/nNOS). Furthermore, synaptic and several functional changes evoked by XIIth nerve injury were to a large extent prevented by intranuclear administration of LVV-miR-shRNA/nNOS. We suggest that nNOS up-regulation creates a repulsive NO gradient for synaptic boutons underlying most of the functional impairment undergone by injured motoneurons. This further strengthens the case for nNOS targeting as a plausible strategy for treatment of peripheral neuropaties and neurodegenerative disorders. [source] Hearing Results After Primary Cartilage Tympanoplasty,THE LARYNGOSCOPE, Issue 12 2000Matthew J. Gerber MD Abstract Objectives/Hypothesis Cartilage,perichondrium grafting of the tympanic membrane has been used in an effort to reduce recurrence or progression of middle ear disease. The rigidity of cartilage has obvious benefit in preventing tympanic membrane retraction, but concern has been raised regarding its sound conduction properties. Few studies in the literature address hearing results after cartilage tympanoplasty. The purpose of this study was to investigate the hearing results after primary cartilage tympanoplasty and compare them with results after primary tympanoplasty with temporalis fascia. Study Design A retrospective review of all ear surgeries using cartilage between 1994 and 1999 was performed. Methods Only primary cases in which the ossicular chain was intact and no mastoid surgery was performed were included. Indications for surgery included tympanic membrane perforation, retraction, and cholesteatoma. Pre- and postoperative speech reception thresholds and air,bone gaps at 500 Hz, 1000 Hz, 2000 Hz, and 4000 Hz were compared. Results Eleven patients comprised the cartilage study group, and there were 11 age- and temporally matched control subjects. The mean improvement in speech reception threshold for both the study group and the control group was 10 dB. The majority of patients in both groups had ABG closure to within 10 dB at all frequencies examined. There were no statistically significant differences in speech reception threshold improvement or air,bone gap closures between the two groups. Conclusions These results demonstrate that hearing results after cartilage tympanoplasty are comparable to those after temporalis fascia tympanoplasty. Therefore, when indicated, a cartilage,perichondrium graft can be used for prevention of disease recurrence or progression without fear of impairing hearing. [source] The incommensurately modulated crystal structure of ,-Pb2BiVO6: interpretation of the phase transition ,,,,, and conduction properties of related materialsACTA CRYSTALLOGRAPHICA SECTION B, Issue 4 2009Pascal Roussel A new polymorph of Pb2BiVO6 was prepared under ambient conditions and its crystal structure was determined by single-crystal X-ray diffraction. The phase transitions ,,, and ,,, were identified in the mother phase; the high-temperature form ,-Pb2BiVO6 eventually decomposes at 753,K to a mixture of Pb4BiVO8 and the high-temperature form of PbBiVO5 before showing recombination at 923,K. ,-Pb2BiVO6 has an incommensurate monoclinic modulated structure. This crystal structure is twinned and complementary structural investigations of a powder sample of ,-Pb2BiVO6 by TEM diffraction studies confirmed the lattice and incommensurate modulation character. Log , = f(T,1) dependences for Pb2BiVO6 -related materials (6% M -for-V-substituted compositions; M = Cr, Mn, P) are reported, which allow the characterization (Ea and isothermal , values) of the ,- as well as the ,- and ,-Pb2BiVO6 varieties. [source] L'arséniate Na3Fe2(AsO4)3: étude structurale de la forme basse température et simulation des propriétés de conduction des cations alcalinsACTA CRYSTALLOGRAPHICA SECTION C, Issue 5 2008Najoua Ouerfelli The crystal structure of the low-temperature garnet-like form of trisodium diiron(III) triarsenate, Na3Fe2(AsO4)3, exhibits a three-dimensional framework with small tunnels running along the [111] direction, in which the Na+ cations are located. This study demonstrates the structural origins of the different ionic conductivities of the low- and high-temperature forms. Sodium conduction properties are simulated by means of the bond-valence-sum (BVS) model; the correlations between the low- and high-temperature crystal structures are discussed. The As, Fe and Na atoms lie on special positions (Wyckoff symbols 24d, 16a and 24c, respectively). [source] Cavotricuspid Isthmus: Anatomy, Electrophysiology, and Long-Term Outcome of Radiofrequency AblationPACING AND CLINICAL ELECTROPHYSIOLOGY, Issue 12 2009Ching-Tai Tai M.D. The cavotricuspid isthmus (CTI) had a complex architecture with an anisotropic conduction property. An incremental pacing from the low right atrial isthmus produced a conduction delay and block, and initiated atrial flutter. Radiofrequency catheter ablation of the CTI was very effective in eliminating the typical atrial flutter. However, atrial fibrillation often occurred after ablation of the isthmus and needs further treatment. [source] | ||||||||||||||||