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Conduction
Kinds of Conduction Terms modified by Conduction Selected AbstractsOPTIMIZATION OF NATTOKINASE PRODUCTION CONDUCTION USING RESPONSE SURFACE METHODOLOGYJOURNAL OF FOOD PROCESS ENGINEERING, Issue 1 2006DJA-SHIN WANG ABSTRACT Natto has attracted worldwide attention because of its health benefits and long history in Japanese food. It has been found that a potent fibrinolytic enzyme named nattokinase, which is extracted from natto, is able to prevent atherosclerosis. The production of nattokinase may be influenced by various factors such as temperature, shaking speed, volume of medium, fermentation time and so forth. Three-step response surface methodology was applied to obtain the optimal operation conditions of the fermentation process in order to maximize the nattokinase yield. The three major steps are described as follows. First, the important factors for fermentation were identified by L8 orthogonal array experiment. The chosen factors were temperature (37 or 45C), shaking speed (110 or 150 rpm), volume of medium (80 or 120 mL), Brix of wheat bran extract (1.5 or 3°), Brix of soy meal extract (1 or 2°), glucose concentration (0.6 or 1.2%) and fermentation time (24 or 36 h). Second, a regression equation was established between the response (i.e., the enzyme activity) and the two statistically significant factors (i.e., the volume of medium and fermentation time). Third, the optimal solutions for the volume of medium and fermentation time were obtained based on the response surface of the regression equation. According to the response surface analysis, the optimal operation conditions for the fermentation process should be 80 mL and 37.0817 h for the volume of medium and the fermentation time, respectively, which resulted in 459.11 FU/mL as the predicted enzyme activity. [source] THERMAL PROCESS EVALUATION OF RETORTABLE POUCHES FILLED WITH CONDUCTION HEATED FOODJOURNAL OF FOOD PROCESS ENGINEERING, Issue 5 2002MARCELO CRISTIANINI ABSTRACT Two models using the finite element technique (FE) and another using an analytical solution to solve the 3-dimensional heat conduction equation for a finite plate were built. FE models were built considering the actual pouch shape and retort temperature profile. Chi-square and regression lines were obtained for each set of temperatures generated by the models against experimental data. A mass average sterilizing value of 9.9 min was estimated when a critical point sterilizing value was at 8.7 min using the 3-Dimensional FE model. Close agreement was found among the three models for heating phase. Using actual retort temperature profile made FE models more accurate than the one using analytical solution, especially for cooling phase. [source] Insight into Proton Conduction of Immobilised Imidazole Systems Via Simulations and Impedance Spectroscopy,FUEL CELLS, Issue 3-4 2008W. L. Cavalcanti Abstract The proton conduction in immobilised imidazole systems has been investigated in order to support the design of new membrane materials for polymer electrolyte membrane fuel cells (PEMFC). In the experimental part of this work, proton conductivities are measured via impedance spectroscopy. The simulation and modelling are performed combining molecular dynamics simulations and energy barrier calculations; the analysis is done via the proton jump energy barrier, collision ratio and radial distribution function. The dependence of the proton mobility on the temperature, spacer length and the density of conducting groups per area is presented. Donors and acceptors groups approach to each other within a distance from 2.8 to 3,Å where the energy barrier for a proton transfer is very low, which favours the proton jump under the studied conditions. The proton conductivity increases with increase in the spacer length. The simulation results are in good agreement with the proton conductivities presented. [source] Comprehensive Modeling of Ion Conduction of Nanosized CaF2/BaF2 Multilayer HeterostructuresADVANCED FUNCTIONAL MATERIALS, Issue 1 2009Xiangxin Guo Abstract Molecular beam epitaxy-grown CaF2/BaF2 heterolayers are a demonstration of the potential of nanoionics. It has been shown that ion conductivities both parallel and perpendicular to the interfaces increase with decrease in interfacial spacing. This size effect was attributed to the thermodynamically necessary redistribution of the mobile fluoride ions (N. Sata, K. Eberl, K. Eberman, J. Maier, Nature 2000, 408, 946; X. X. Guo, I. Matei, J.-S. Lee, J. Maier, Appl. Phys. Lett. 2007, 91, 103102). On this basis, the striking phenomenon of an upward bending in the effective parallel conductivity as a function of inverse interfacial spacing for low temperatures (T,,,593,K) has been satisfactorily explained by application of a modified Mott,Schottky model for BaF2 (X.X. Guo, I. Matei, J. Jamnik, J.-S. Lee, J. Maier, Phys. Rev. B 2007, 76, 125429). This model was further confirmed by measurements perpendicular to the interfaces that offer complementary information on the more resistive parts. Here a successful comprehensive modeling of parallel and perpendicular conductivities for the whole parameter range, namely for interfacial spacings ranging from 6 to 200,nm and investigated temperatures ranging from 455 to 833,K, is presented. The model is based on literature data for carrier mobilities and Frenkel reaction constants and the assumption of a pronounced F, redistribution. Given the fact that an impurity content that was experimentally supported is taken into account and apart from minor assumptions concerning profile homogeneity, the only fit parameter is the space charge potential. In particular, it is worth mentioning that in BaF2 the low temperature Mott,Schottky space charge zone which is determined by impurities changes over, at high temperatures, into a Gouy,Chapman situation owing to increased thermal disorder. (The situation in CaF2 is of Gouy,Chapman type at all temperatures.) [source] The Role of the Oxygen/Water Redox Couple in Suppressing Electron Conduction in Field-Effect TransistorsADVANCED MATERIALS, Issue 30 2009Carla M. Aguirre The suppression of electron (n-type) conduction observed in back-gated field effect transistors is the result of an electrochemical charge transfer process to the oxygen/water layer adsorbed on hydrophilic substrates. The impact of this phenomenon is demonstrated with nanoscale and thin-film carbon nanotube transistors. [source] A Glass Hook Allows Fishing of Hexa- peri -hexabenzocoronene Graphitic Nanotubes: Fabrication of a Macroscopic Fiber with Anisotropic Electrical Conduction,ADVANCED MATERIALS, Issue 10 2006Y. Yamamoto Fishing of graphitic nanotubes with a macroscopic glass hook: A ,30,mm long fiber (see figure and cover) is readily processed from a suspension of self-assembled nanotubes with one-handed helical chirality, formed from the (R)- or (S)-enantiomer of chiral amphiphile 2. The majority of the nanotubes in the fiber are unidirectionally oriented along the fiber axis. Upon doping with I2, the fiber displays an anisotropic electrical conduction along the fiber axis more than an order of magnitude greater than that across the fiber axis. [source] Utilization of Retrograde Right Bundle Branch Block to Differentiate Atrioventricular Nodal from Accessory Pathway ConductionJOURNAL OF CARDIOVASCULAR ELECTROPHYSIOLOGY, Issue 7 2009SURAJ KAPA M.D. Introduction: Defining whether retrograde ventriculoatrial (V-A) conduction is via the AV node (AVN) or an accessory pathway (AP) is important during ablation procedures for supraventricular tachycardia (SVT). With the introduction of ventricular extrastimuli (VEST), retrograde right bundle branch block (RBBB) may occur, prolonging the V-H interval, but only when AV node conduction is present. We hypothesized that when AP conduction was present, the V-A interval would increase less than the V-H interval, whereas with retrograde nodal conduction, the V-A interval would increase at least as much as the V-H interval. Methods and Results: We retrospectively reviewed the electrophysiological studies of patients undergoing ablation for AVN reentrant tachycardia (AVNRT) (55) or AVRT (50), for induction of retrograde RBBB during the introduction of VEST, and the change in the measured V-H and V-A intervals. Results were found to be reproducible between independent observers. Out of 105 patients, 84 had evidence of induced retrograde RBBB. The average V-H interval increase with induction of RBBB was 53.7 ms for patients with AVRT and 54.4 ms for patients with AVNRT (P = NS). The average V-A interval increase with induction of RBBB was 13.6 ms with AVRT and 70.1 ms with AVNRT (P < 0.001). All patients with a greater V-H than V-A interval change had AVRT, and those with a smaller had AVNRT. Conclusions: Induction of retrograde RBBB during VEST is common during an electrophysiological study for SVT. The relative change in the intervals during induction of RBBB accurately differentiates between retrograde AVN and AP conduction. [source] Intermittent Impairment of Atrioventricular Conduction: What is the Mechanism?JOURNAL OF CARDIOVASCULAR ELECTROPHYSIOLOGY, Issue 5 2009MAREK JASTRZEBSKI M.D., Ph.D. No abstract is available for this article. [source] Quantitative Analysis of the Duration of Slow Conduction in the Reentrant Circuit of Ventricular Tachycardia After Myocardial InfarctionJOURNAL OF CARDIOVASCULAR ELECTROPHYSIOLOGY, Issue 9 2008YI-GANG LI M.D. Background: Few data are available to define the circuits in ventricular tachycardia (VT) after myocardial infarction and the conduction time (CT) through the zone of slow conduction (SCZ). This study assessed the CT of the SCZ and identified different reentrant circuits. Methods: During VTs, concealed entrainment (CE) was attempted. The SCZ was identified by a difference between postpacing interval (PPI) and VT cycle length (VTcl) ,30 ms. Since the CT in the normally conducting part of the VT circuit is constant during VT and CE, a CE site within the reentrant circuit with (S-QRS)/PPI , 50% was classified as an inner reentry in which the entire circuit was within the scar, and a CE site with (S-QRS)/PPI < 50% as a common reentry in which part of the circuit was within the scar and part out of the scar. Results: CE was achieved in 20 VTs (12 patients). Six VTs (30%) with a (S-QRS)/PPI ,50% were classified as inner reentry and 14 VTs (70%) with a (S-QRS)/PPI <50% during CE mapping as common reentry. The EG-QRS interval (308 ± 73 ms vs 109 ± 59 ms, P < 0.0001) was significantly longer and the incidence of systolic potentials higher (4/6 vs 0/12, P < 0.001) in the inner reentry group. For the 14 VTs with a common reetry, the CT of the SCZ was 348 ± 73 ms, while the CT in the normal area was 135 ± 50 ms. Conclusion: According to the proposed classification, 30% of VTs after myocardial infarction had an entire reentrant circuit within the scar. In VTs with a common reentrant circuit, the CT of the SCZ is approximately four times longer than the CT in the normal area, accounting for more than 70% of VTcl. [source] Conduction Through the Lateral Mitral Isthmus: Block or PseudoblockJOURNAL OF CARDIOVASCULAR ELECTROPHYSIOLOGY, Issue 1 2008SEIJI TAKATSUKI M.D. [source] A Basket Full of Mechanistic Insights into Pulmonary Vein Arrhythmogenicity: Reentry, Focal Activity, or Fibrillatory Conduction?JOURNAL OF CARDIOVASCULAR ELECTROPHYSIOLOGY, Issue 1 2007STEPHAN WILLEMS M.D. No abstract is available for this article. [source] Atrial Tachycardia Originating from the Upper Left Atrial Septum: Demonstration of Transseptal Interatrial Conduction Using the Infolded Atrial WallsJOURNAL OF CARDIOVASCULAR ELECTROPHYSIOLOGY, Issue 8 2006KOJI KUMAGAI M.D. We report a rare case of atrial tachycardia (AT) originating from the upper left atrial septum. Electroanatomic mapping of both atria demonstrated that the earliest atrial activation during AT occurred at the upper left atrial septum 26 msec before the onset of the P wave, followed by the mid-right atrial septum (10 msec before the onset of the P wave) and then the upper right atrial septum just adjacent to the left septal AT site (1 msec before the onset of the P wave), indicating detour pathway conduction from the upper left to the upper right atrium. Embryologically, it was suggested that the superior components of the secondary atrial septum are made by the infolded atrial walls and could develop a transseptal detour pathway involving the left-side atrial septal musculature, the superior rim of the oval fossa and the right-side atrial septal musculature. A single radiofrequency application targeting the upper left atrial septum successfully abolished the AT. [source] Spontaneous Transition of 2:1 Atrioventricular Block to 1:1 Atrioventricular Conduction During Atrioventricular Nodal Reentrant Tachycardia:JOURNAL OF CARDIOVASCULAR ELECTROPHYSIOLOGY, Issue 12 2003Evidence Supporting the Intra-Hisian or Infra-Hisian Area as the Site of Block Introduction: The incidence of spontaneous transition of 2:1 AV block to 1:1 AV conduction during AV nodal reentrant tachycardia has not been well reported. Among previous studies, controversy also existed about the site of the 2:1 AV block during AV nodal reentrant tachycardia. Methods and Results: In patients with 2:1 AV block during AV nodal reentrant tachycardia, the incidence of spontaneous transition of 2:1 AV block to 1:1 AV conduction and change of electrophysiologic properties during spontaneous transition were analyzed. Among the 20 patients with 2:1 AV block during AV nodal reentrant tachycardia, a His-bundle potential was absent in blocked beats during 2:1 AV block in 8 patients, and the maximal amplitude of the His-bundle potential in the blocked beats was the same as that in the conducted beats in 4 patients and was significantly smaller than that in the conducted beats in 8 patients (0.49 ± 0.25 mV vs 0.16 ± 0.07 mV, P = 0.007). Spontaneous transition of 2:1 AV block to 1:1 AV conduction occurred in 15 (75%) of 20 patients with 2:1 AV block during AV nodal reentrant tachycardia. Spontaneous transition of 2:1 AV block to 1:1 AV conduction was associated with transient right and/or left bundle branch block. The 1:1 AV conduction with transient bundle branch block was associated with significant His-ventricular (HV) interval prolongation (66 ± 19 ms) compared with 2:1 AV block (44 ± 6 ms, P < 0.01) and 1:1 AV conduction without bundle branch block (43 ± 6 ms, P < 0.01). Conclusion: The 2:1 AV block during AV nodal reentrant tachycardia is functional; the level of block is demonstrated to be within or below the His bundle in a majority of patients with 2:1 AV block during AV nodal reentrant tachycardia, and a minority are possibly high in the junction between the AV node and His bundle. (J Cardiovasc Electrophysiol, Vol. 14, pp. 1337-1341, December 2003) [source] Incessant Nonreentrant Tachycardia Due to Simultaneous Conduction Over Dual Atrioventricular Nodal Pathways Mimicking Atrial Fibrillation in Patients Referred for Pulmonary Vein IsolationJOURNAL OF CARDIOVASCULAR ELECTROPHYSIOLOGY, Issue 7 2003Moussa Mansour M.D. It has been reported that conduction over the fast and slow pathways of the AV node can occur simultaneously, leading to a double ventricular response from each atrial beat. We report the cases of two patients referred to us for evaluation of symptomatic, incessant, and irregular narrow-complex tachycardia, misdiagnosed as atrial fibrillation, for consideration of pulmonary vein isolation. At presentation, careful evaluation of the electrograms revealed the presence of two ventricular activations for each atrial beat. At electrophysiologic study, both patients were found to have nonreentrant tachycardias arising from simultaneous conduction over the fast and slow pathways of the AV node. In one patient, the tachycardia had resulted in cardiomyopathy. Slow AV nodal pathway ablation performed in both patients resulted in cure of their tachycardias and recovery of ventricular function in the patient with cardiomyopathy. (J Cardiovasc Electrophysiol, Vol. 14, pp. 752-755, July 2003) [source] Autonomic Blockade Unmasks Maturational Differences in Rate-Dependent Atrioventricular Nodal Conduction and Facilitation in the MouseJOURNAL OF CARDIOVASCULAR ELECTROPHYSIOLOGY, Issue 2 2003SAMIR SABA M.D. Maturational Differences in Murine AVN Conduction. Introduction: In large animals, rate-dependent AV nodal (AVN) properties of conduction are modulated by autonomic inputs. In this study, we investigated whether the properties of AVN conduction and facilitation are altered by autonomic blockade in the mouse and whether this effect is age dependent. Methods and Results: Young (age 4,6 weeks; n = 11) and adult (age 8,9 months; n = 11) female mice underwent in vivo electrophysiologic testing, before and after autonomic blockade. After autonomic blockade, the adult mice had significantly longer AVN effective refractory period (AVNERP; 67 ± 14 msec vs 56 ± 4 msec, P = 0.05) and functional refractory period (AVNFRP; 81 ± 10 msec vs 72 ± 4 msec, P = 0.05). With autonomic blockade, the increase from baseline of AVN Wenckebach cycle length (,AVW; 1.8 ± 8.1 msec vs 8.8 ± 3.3 msec, P = 0.04), as well as of AVNERP (,AVNERP; 3.5 ± 3.5 msec vs 21.4 ± 12.6 msec, P = 0.002) and AVNFRP (,AVNFRP; 2.3 ± 3.2 msec vs 12.8 ± 9.0 msec, P = 0.008), was significantly larger in adult than in young mice. Compared with young mice, adult mice were less likely to exhibit AVN facilitation (44% vs 90%, P = 0.03) and had smaller maximal shortening of AVN conduction times after the "test beat" for any coupling of the "facilitating beat" (4 ± 4 msec vs 7 ± 3 msec, P = 0.05). Conclusion: Complete autonomic blockade significantly increases AVN conduction times and refractory periods in adult but not in young mice. Adult mice also exhibit less AVN facilitation. Our results confirm that, like in larger animals, rate-dependent murine AVN properties of conduction are under autonomic regulation. Adult mice have higher sympathetic AVN inputs at baseline, leading to slower conduction after autonomic blockade. (J Cardiovasc Electrophysiol, Vol. 14, pp. 191-195, February 2003) [source] High-Resolution Mapping of Tachycardia Originating from the Superior Vena Cava: Evidence of Electrical Heterogeneity, Slow Conduction, and Possible Circus Movement ReentryJOURNAL OF CARDIOVASCULAR ELECTROPHYSIOLOGY, Issue 4 2002DIPEN C. SHAH M.D. Superior Vena Cava Reentry. High-resolution mapping of a tachycardia originating from the superior vena cava (SVC) in a patient with atrial fibrillation is described. Unidirectional circuitous repetitive activation encompassing the full tachycardia cycle length was documented around a line of block within the myocardial sleeve of the SVC. Intermittent conduction to the right atrium resulted in an irregular atrial tachycardia. Evidence of electrical heterogeneity and slow conduction persisted in sinus rhythm and was exaggerated by premature stimulation but did not reproduce the activation pattern during tachycardia. All the available evidence is best compatible with circus movement reentry within the SVC, with marked slow and anisotropic conduction responsible for the restricted dimensions of the reentrant circuit. These findings may suggest a similar substrate and arrhythmia mechanism in the myocardium of the pulmonary veins. [source] Influences on Fast and Slow Pathway Conduction in Children: Does the Definition of Dual Atrioventricular Node Physiology Need to Be Changed?JOURNAL OF CARDIOVASCULAR ELECTROPHYSIOLOGY, Issue 3 2002ANDREW D. BLAUFOX M.D. [source] Dissociation Between Coronary Sinus and Left Atrial Conduction in Patients with Atrial Fibrillation and FlutterJOURNAL OF CARDIOVASCULAR ELECTROPHYSIOLOGY, Issue 6 2001GJIN NDREPEPA M.D. Dissociation Between CS and LA Conduction.Introduction: Coronary sinus (CS) recordings are routinely used during electrophysiologic studies for various supraventricular and ventricular arrhythmias with the understanding that they represent left atrial (LA) activity. However, the behavior of CS electrical activity during atrial arrhythmias has not drawn any special attention beyond standard considerations. Methods and Results: The study population consisted of 9 patients (3 women; mean age 59 ± 11 years) with atrial fibrillation (AF) and atrial flutter (AFL) who developed dissociation of conduction between the CS and posterior LA during spontaneous AF and AFL. In all patients, the LA and the CS were mapped using a 64-electrode basket catheter and a multipolar electrode catheter, respectively. The right atrium (RA) was mapped simultaneously using a 24-polar electrode catheter (7 patients) or a 64-electrode basket catheter (2 patients). Eight patients showed stable double potentials in CS recordings during AF (9 episodes) and AFL (3 episodes). During ongoing arrhythmias, the first row of potentials maintained a constant relationship with the RA activity, whereas the second row of potentials was discordant with the posterior wall of the LA in 7 patients and concordant in 2 patients. In 1 patient with counterclockwise AFL, CS activation was isolated from the posterior wall of the RA until it reached the distal portion of the CS, after which it entered the lateral region of the LA. In 1 patient, a macroreentrant LA tachycardia involving CS muscle was observed. Rapid atrial pacing from the proximal CS and extrastimuli produced longitudinal dissociation of CS activation in all patients. Conclusion: Conduction between the CS and posterior LA can be dissociated during spontaneous atrial arrhythmias and provocative proximal CS pacing. [source] Connexin40-Deficient Mice Exhibit Atrioventricular Nodal and Infra-Hisian Conduction AbnormalitiesJOURNAL OF CARDIOVASCULAR ELECTROPHYSIOLOGY, Issue 11 2000BRIAN A. VANDERBRINK B.S. AV Nodal and Infra-Hisian Conduction in Cx40 Mice. Introduction: Previous electrophysiologic investigations have described AV conduction disturbances in connexin4(Cx40)-deficient mice. Because expression or(Cx40 occurs predominantly in the atria and His-Purkinje system of the mouse heart, the AV conduction disturbances were thought to be secondary to disruption in His-Pnrkinje function. However, the lack of a His-bundle electrogram recording in the mouse has limited further investigation of the importance of Cx40. Using a novel technique to record His-bundle recordings in Cx40-deficient mice, we define the physiologic importance of defciencies in Cx40. Methods and Results: Ten Cx40 -/- mice and 11 Cx40+/+ controls underwent a blinded, in vivo, closed chest electrophysiology study at 9 to 12 weeks of age. In the Cx40+/+ mice, the PR interval was significantly longer compared with Cx40+/+ mice (44.6 ± 6.4 msec vs 36.0 ± 4.1 msec, P = 0.002). Not only the HV interval (14.0 ± 3.0 msec vs 10.4 ± 1.2 msec, P = 0.003) but also the AH interval (33.2 ± 4.8 msec vs 27.1 ± 3.7 msec, P = 0.006), AV Wenckebach cycle lengths, and AV nodal effective and functional refractory periods were prolonged in Cx40 -/- compared with Cx40+/+ mice. Conclusion: Cx40-deficient mice exhibit significant delay not only in infra-Hisian conduction, as would be expected from the expression of Cx40 in the His-Purkinje system but also in the electrophysiologic parameters that reflect AV nodal conduction. Our data suggest a significant role of Cx40 in atrionodal conduction and/or in proximal His-bundle conduction, [source] Transvenous Parasympathetic Nerve Stimulation in the Inferior Vena Cava and Atrioventricular ConductionJOURNAL OF CARDIOVASCULAR ELECTROPHYSIOLOGY, Issue 1 2000PATRICK SCHAUERTE M.D. Parasympathetic Stimulation in the Inferior Vena Cava. Introduction: In previous reports, we demonstrated a technique for parasympathetic nerve stimulation (PNS) within the superior vena cava, pulmonary artery, and coronary sinus to control rapid ventricular rates during atrial fibrillation (AF). In this report, we describe another vascular site, the inferior vena cava (IVC), at which negative dromotropic effects during AF could consistently he obtained. Moreover, stimulation at this site also induced dual AV nodal electrophysiology. Methods and Results: PNS was performed in ten dogs using rectangular stimuli (0.1 msec/20 Hz) delivered through a catheter with an expandable electrode basket at its tip. Within 3 minutes and without using fluoroscopy, the catheter was positioned at an effective PNS site in the IVC at the junction of the right atrium. AF was induced and maintained by rapid atrial pacing. During stepwise increase of the PNS voltage from 2 to 34 V, a graded response of ventricular rate slowing during AF was observed (266 ± 79 msec without PNS vs 1,539 ± 2,460 msec with PNS at 34 V; P = 0.005 by analysis of variance), which was abolished by atropine and blunted by hexamethonium. In three animals, PNS was performed during sinus rhythm. Dual AV nodal electrophysiology was present in 1 of 3 dogs in control, whereas with PNS, dual AV nodal electrophysiology was observed in all three dogs. PNS did not significantly change sinus rate or arterial blood pressure during ventricular pacing. Conclusion: Stable and consistent transvenous electrical stimulation of parasympathetic nerves innervating the AV node can be achieved in the IVC, a transvenous site that is rapidly and readily accessible. The proposed catheter approach for PNS can be used to control ventricular rate during AF in this animal model. [source] Acute Effects of Low Doses of Red Wine on Cardiac Conduction and Repolarization in Young Healthy SubjectsALCOHOLISM, Issue 12 2009Matteo Cameli Background:, Moderate to high blood concentrations of ethanol have been shown to yield acute changes in cardiac electrophysiological properties, but the effect of low concentrations have never been assessed. The role of concomitant changes in clinical variables or cardiac dimensions is also still unknown. This study aimed at exploring the acute effects of low doses of ethanol, administered as Italian red wine, on conduction, depolarization, and repolarization electrocardiographic (ECG) intervals in a population of healthy subjects. Methods:, Forty healthy young volunteers drank a low quantity of red wine (5 ml/kg), and an equal volume of fruit juice in separate experiments. Heart rate, P-wave duration, PR interval, QRS duration, QT interval, corrected QT interval, QT dispersion, and corrected QT dispersion were assessed at baseline and after 60 minutes from challenge. Results:, Mean blood ethanol concentration after drinking was 0.48 ± 0.06 g/l. Compared to the control challenge, significant changes after red wine intake were observed in P-wave duration (from 101 ± 11 to 108 ± 14 milliseconds, p = 0.0006), PR interval (from 153 ± 15 to 167 ± 17 milliseconds, p < 0.0001), QT interval (from 346 ± 28 to 361 ± 24 milliseconds, p < 0.0001), and corrected QT interval (from 388 ± 24 to 402 ± 30 milliseconds, p = 0.0006). None of these changes showed correlations with modifications in clinical or echocardiographic variables. In multivariate analyses aimed at exploring predictors of ECG changes, none of the variables entered the final models. Conclusions:, Low doses of red wine acutely slow cardiac conduction and prolong repolarization in normal individuals. These changes are poorly predictable. The potential arrhythmogenic impact of these effects is worthy of exploration. [source] Independence of Connexin Expression and Vasomotor Conduction from Sympathetic Innervation in Hamster Feed ArteriesMICROCIRCULATION, Issue 5 2004ROBIN C. LOOFT-WILSON ABSTRACT Objective: Vasomotor responses can travel along the wall of resistance microvessels by two distinct mechanisms: cell-to-cell conduction through gap junctions or the release of neurotransmitter along perivascular nerves. It is unknown whether vascular innervation influences the expression of connexin molecules which comprise gap junctions, or the conduction of vasomotor responses. In feed arteries of the hamster retractor muscle (RFA), the authors tested whether sympathetic denervation would alter the expression of connexin isoforms and the conduction of vasomotor responses. Methods: Using intact vessels with sympathetic innervation and those 7,8 days following denervation surgery, mRNA expression was quantified using real-time PCR, cellular localization of Cx protein was characterized using immunohistochemistry, and vasomotor responses to dilator and constrictor stimuli were evaluated in isolated pressurized RFA. Results: Connexin protein localization and mRNA expression were similar between innervated and denervated vessels. mRNA levels were Cx43 = Cx37 > Cx45 , Cx40. Vasodilation to acetylcholine conducted ,2000 , m along innervated and denervated vessels, as did the biphasic conduction of vasoconstriction and vasodilation in response to KCl. Vasoconstriction to phenylephrine conducted < 500 , m and was attenuated (p < .05) in denervated vessels. Conclusions: The profile of connexin expression and the conduction of vasomotor responses are largely independent of sympathetic innervation in feed arteries of the hamster retractor muscle (RFA). [source] Stepwise Transition of 2:1 Atrio-Ventricular Block to 1:1 Conduction Induced by Ventricular Premature Beats in a Patient with Atypical AVNRTPACING AND CLINICAL ELECTROPHYSIOLOGY, Issue 2 2010ANTONIO SORGENTE M.D. A 55-year-old man with a 2-year history of recurrent paroxysmal palpitations and with an electrocardiogram documentation of atypical atrioventricular nodal re-entrant tachycardia (AVNRT) was referred to us for catheter ablation. After an initial ablation attempt, several episodes of atypical AVNRT were induced. During one of these episodes, we documented a stepwise transition of 2:1 atrioventricular block to 1:1 conduction, following two single ventricular premature beats. This phenomenon confirmed the functional nature of the AV block during AVNRT and indirectly its infra-nodal location. (PACE 2010; 33:e20,e23) [source] Abnormal Atrioventricular Node Conduction and Atrioventricular Nodal Reentrant Tachycardia in Patients Older Versus Younger Than 65 Years of AgePACING AND CLINICAL ELECTROPHYSIOLOGY, Issue 2009MIHAELA GRECU M.D. Study Objective: We examined the possible role of atrioventricular node (AVN) conduction abnormalities as a cause of AVN reentrant tachycardia (RT) in patients >65 years of age. Study Population: Slow pathway radiofrequency catheter ablation (RFCA) was performed in 104 patients. Patients in group 1 (n = 14) were >65 years of age and had AV conduction abnormalities associated with structural heart disease. Patients in group 2 (n = 90) were <65 years of age and had lone AVNRT. Results: Patients in group 1 versus group 2 (66% vs. 46% men) had a first episode of tachycardia at an older age than in group 2 (68 ± 16.8 vs 32.5 ± 18.8 years, P = 0.007). The history of arrhythmia was shorter in group 1 (5.4 ± 3.8 vs 17.5 ± 14, P = 0.05) and was associated with a higher proportion of patients with underlying heart disease than in group 2 (79% vs 3%, P < 0.001). The electrophysiological measurements were significantly shorter in group 2: atrial-His interval (74 ± 17 vs 144 ± 44 ms, P = 0.005), His-ventricular (HV) interval (41 ± 5 vs 57 ± 7 ms, P = 0.001), Wenckebach cycle length (329 ± 38 vs 436 ± 90 ms, P = 0.001), slow pathway effective refractory period (268 ± 7 vs 344 ± 94 ms, P = 0.005), and tachycardia cycle length (332 ± 53 vs 426 ± 56 ms, P = 0.001). The ventriculoatrial block cycle length was similar in both groups. The immediate procedural success rate was 100% in both groups, and no complication was observed in either group. One patient in group 2 had recurrence of AVNRT. One patient with a 98-ms HV interval underwent permanent VVI pacemaker implantation before RFCA procedure. Conclusion: In patients undergoing RFCA for AVNRT at >65 years of age had a shorter history of tachycardia-related symptoms than patients with lone AVNRT. The longer AVN conduction intervals and refractory period might explain the late development of AVNRT in group 1. [source] Supraventricular Tachycardia with Transient Aberrant Conduction: What is the Mechanism?PACING AND CLINICAL ELECTROPHYSIOLOGY, Issue 7 2007WARANGKNA BOONYAPISIT M.D. No abstract is available for this article. [source] Chronic Amiodarone Effects on Epicardial Conduction and Repolarization in the Isolated Porcine HeartPACING AND CLINICAL ELECTROPHYSIOLOGY, Issue 7 2000DOMINIQUE LACROIX Amiodarone is a potent antiarrhythmic agent with complex chronic effects, notably on repolarization and conduction, that are not fully understood. Its low arrhythmogenic potential has been related to a lack of increase in repolarizution dispersion. Since its effects are not documented in pigs we conducted a mapping study of activation and repolarization in isolated perfused porcine hearts. Amio20 female pigs (n = 7) received amiodarone 20 mg/kg per day over 4 weeks while Amio 5O female pigs (n = 7) received 50 mg/kg per day over 4 weeks. Concentrations of the drug encompassed values found in clinical studies. Then, activation patterns and activation-to-recovery intervals (ARI) were mapped epicardially from 128 unipolar electrograms in isolated perfused hearts in corroboration of epicardial action potential recordings. Mean ARI was longer in Amio20 experiments compared to the seven control hearts (325 ±11 ms vs 288 ± 5 m.s at 1,000 ms), whereas ARI dispersion was not different, being comprised between 7 and 11 ms and generating smooth gradients. In Amio5O experiments, mean ARI was further prolonged (390 ±10 ms at 1,500 ms) with an exaggerated reverse rate dependence concomitant with a depressant effect on the plateau of the action potential. Again, ARI dispersion did not differ from controls. Finally, the drug depressed the maximal rate of depolarization (Vmax) and slowed conduction in a rate dependent and concentration dependent fashion. In conclusion, chronic amiodarone induces Class I and Class HI antiarrhythmic effects in ventricular porcine epicardium that are concentration dependent but does not affect dispersion of repolarization. This may partly explain its low arrhythmogenic potential. [source] Preserving Normal Ventricular Activation Versus Atrioventricular Delay Optimization During Pacing: The Role of Intrinsic Atrioventricular Conduction and Pacing RatePACING AND CLINICAL ELECTROPHYSIOLOGY, Issue 1 2000IVAN ILIEV ILIEV The purpose of the study was to compare the effects of DDD pacing with optimal AV delay and AAI pacing on the systolic and diastolic performance at rest in patients with prolonged intrinsic AV conduction (first-degree AV block). We studied 17 patients (8 men, aged 69 ± 9 years) with dual chamber pacemakers implanted for sick sinus syndrome in 15 patients and paroxysmal high degree AV block in 2 patients. Aortic flow and mitral flow were evaluated using Doppler echocardiography. Study protocol included the determination of the optimal A V delay in the DDD mode and comparison between AAI and DDD with optimal A V delay for pacing rate 70/min and 90/min. Stimulus-R interval during AAI (AHI) was 282 ± 68 ms for rate 70/min and 330 ± 98 ms for rate 90/min (P < 0.01). The optimal A V delay was 159 ± 22 ms, A V delay optimization resulted in an increase of an aortic flow time velocity integral (AFTVI) of 16%± 9%. At rate 70/min the patients with ARI , 270 ms had higher AFTVI in AAI than in DDD (0.214 ± 0.05 m vs 0.196 ± 0.05 m, P < 0.01), while the patients with ARI > 270 ms demonstrated greater AFTVI under DDD compared to AAI(0.192 ± 0.03 m vs 0.166 ± 0.02 m, P < 0.01). At rate 90/min AFTVI was higher during DDD than AAI (0.183 ± 0.03 m vs 0.162 ± 0.03 m, P < 0.01). Mitral flow time velocity integral (MFTVI) at rate 70/min was higher in DDD than in AAI (0.189 ± 0.05 m vs 0.173 ± 0.05 mP < 0.01), while at rate 90/min the difference was not significant in favor of DDD (0.149 ± 0.05 m vs 0.158 ± 0.04 m). The results suggest that in patients with first-degree AV block the relative impact of DDD and AAI pacing modes on the systolic performance depends on the intrinsic AV conduction time and on pacing rate. [source] Soret Diffusion and Non-Ideal Dufour Conduction in Macroporous Catalysts with Exothermic Chemical Reaction at Large Intrapellet Damköhler NumbersTHE CANADIAN JOURNAL OF CHEMICAL ENGINEERING, Issue 3 2007Laurence A. Belfiore Abstract The adiabatic temperature rise in catalytic pellets is predicted from a modified version of the Prater equation. Onsager reciprocal relations for coupled heat and mass transfer are violated in an analysis of thermal diffusion in macroporous catalysts with exothermic chemical reaction when Dufour conduction (i.e., the diffusion-thermo effect) is neglected. In this contribution, Dufour conduction is analyzed for both ideal and non-ideal pseudo-binary gas mixtures that simulate the production of methanol from carbon monoxide and hydrogen. In the diffusion-controlled regime at large intrapellet Damköhler numbers where intermolecular collisions provide the dominant resistance to mass transfer within the catalytic pores, temperatures in the catalytic core could be much greater than predictions based on the original Prater equation when the Prater number exceeds 0.30. The molecular flux of thermal energy includes Fourier's law, the interdiffusional flux, and Dufour conduction. Diffusional mass flux includes Fick's law and the Soret effect. All physicochemical properties of the reactive gas mixture exhibit temperature dependence. There is essentially no difference between maximum intrapellet temperature predictions that include or neglect ideal Dufour conduction when external catalytic surface temperatures range from 300-400 K and thermal diffusion enhances the flux of "smaller" reactants toward the centre of the catalyst. For "large-molecule reactants" that participate in exothermic reactions, thermal diffusion opposes Fick's law and Dufour conduction opposes Fourier's law. Under these conditions, it is demonstrated that core temperatures are overestimated by neglecting both off-diagonal coupling mechanisms (i.e., Soret diffusion and Dufour conduction). Prater numbers greater than unity and unrealistically high gas pressures are required to distinguish between maximum intrapellet temperatures for ideal and real gas simulations, where the latter consider two-body interactions for Lennard-Jones molecules in the virial equation of state. On prédit l'augmentation de la température adiabatique dans les pastilles catalytiques à partir d'une version modifiée de l'équation de Prater. Les relations réciproques d'Onsager pour le transfert de chaleur et de matière couplé sont violées dans une analyse de la diffusion thermique dans les catalyseurs macroporeux avec réaction chimique exothermique lorsque la conduction de Dufour (p.ex., l'effet de thermo-diffusion) est négligée. Dans cet article, on analyse la conduction de Dufour pour des mélanges de gaz pseudo-binaires idéaux et non idéaux qui simulent la production de méthanol à partir d'oxyde de carbone et d'hydrogène. Dans le régime à diffusion contrôlée à grand nombre de Damköhler entre les pastilles pour lesquels les collisions entre les molécules fournit la résistance dominante au transfert de matière à l'intérieur des pores catalytiques, les températures dans le noyau catalytique pourraient être bien plus grandes que les prédictions basées sur l'équation de Prater originale lorsque le nombre de Prater excède 0,30. Le flux moléculaire de l'énergie thermique inclut la loi de Fourier, le flux interdiffusionnel, et la conduction de Dufour. Le flux massique diffusionnel inclut la loi de Fick et l'effet Soret. Toutes les propriétés physicochimiques du mélange de gaz réactif montre une dépendance thermique. Il n'y a essentiellement pas de différence entre les prédictions des températures maximales entre les pastilles qui incluent ou négligent la conduction de Dufour idéale quand les températures de surface catalytiques externes sont comprises entre 300 et 400 K; la diffusion thermique améliore le flux des réactifs «plus petits» vers le centre du catalyseur. Pour les «réactifs composés de grandes molécules» qui participent aux réactions exothermiques, la diffusion thermique s'oppose à la loi de Fick et la conduction de Dufour à la loi de Fourier. Dans ces conditions, il est démontré que les températures de noyau sont surestimées en négligeant les deux mécanismes de couplage hors-diagonales (c.à-d. la diffusion de Soret et la conduction de Dufour). Des nombres de Prater plus grands que l'unité et des pressions de gaz élevées peu réalistes sont nécessaires pour distinguer les températures maximales entre les pastilles entre les simulations de gaz idéales et réelles, en considérant pour ces dernières les interactions à deux corps pour les molécules de Lennard-Jones dans l'équation d'état du viriel. [source] The Effect of Topical Epinephrine on Peripheral Nerve Conduction,,§THE LARYNGOSCOPE, Issue 10 2002Quintessa Miller MD Abstract Objective/Hypothesis The aim of the study was to determine the effect of direct application of epinephrine solution on peripheral nerve conduction latency and amplitude. It was hypothesized that epinephrine does not cause neurapraxia when a standard (1:10,000) solution is applied topically. Study Design Eleven animals were divided into two groups of five and six. Group I had their left sciatic nerves and group II had their right sciatic nerves treated with epinephrine-soaked patties. The contralateral nerves of each group served as controls. Methods Nerve conduction studies were performed at baseline and immediately, at 1 minute, and at 5 minutes after patty application. Results Latency was found to increase above baseline immediately after patty application (P = .003) for the epinephrine-treated and saline-treated groups. Furthermore, the amplitude at 5 minutes after patty application increased from baseline (P = .009) for both groups. These observed differences were below what is considered to be clinically significant. Conclusion Topical epinephrine at a standard solution (1:10,000) does not lead to clinically significant nerve conduction abnormalities. [source] Altered Interatrial Conduction Detected in MADIT II Patients Bound to Develop Atrial FibrillationANNALS OF NONINVASIVE ELECTROCARDIOLOGY, Issue 3 2009Fredrik Holmqvist M.D., Ph.D. Background: Changes in P-wave morphology have recently been shown to be associated with interatrial conduction route used, without noticeable changes of P-wave duration. This study aimed at exploring the association between P-wave morphology and future atrial fibrillation (AF) development in the Multicenter Automatic Defibrillator Trial II (MADIT II) population. Methods: Patients included in MADIT-II without a history of AF with sinus rhythm at baseline who developed AF during the study ("Pre-AF") were compared to matched controls without AF development ("No-AF"). Patients were followed for a mean of 20 months. A 10-minute high-resolution bipolar ECG recording was obtained at baseline. Signal-averaged P waves were analyzed to determine orthogonal P-wave morphology, P-wave duration, and RMS20. The P-wave morphology was subsequently classified into one of three predefined types using an automated algorithm. Results: Thirty patients (age 68 ± 7 years) who developed AF during MADIT-II were compared with 60 patients (age 68 ± 8 years) who did not. P-wave duration and RMS20 in the Pre-AF group was not significantly different from the No-AF group (143 ± 21 vs 139 ± 30 ms, P = 0.26, and 2.0 ± 1.3 vs 2.1 ± 1.0 ,V, P = 0.90). The distribution of P-wave morphologies was shifted away from Type 1 in the Pre-AF group when compared to the No-AF group (Type 1/2/3/atypical; 25/60/0/15% vs 10/63/10/17%, P = 0.04). Conclusions: This study is the first to describe changes in P-wave morphology in patients prior to AF development. The results indicate that abnormal interatrial conduction may play a role in AF development in patients with prior myocardial infarction and congestive heart failure. [source] | ||||||||||||||||||||||||||||||||||||||||||||||