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Conduction Block (conduction + block)
Selected AbstractsCLINICAL AND IMMUNOLOGICAL FEATURES AND RESPONSE TO IVIg IN PATIENTS WITH CLINICALLY TYPICAL MULTIFOCAL MOTOR NEUROPATHY BUT NO OVERT CONDUCTION BLOCKJOURNAL OF THE PERIPHERAL NERVOUS SYSTEM, Issue 1 2000E. Nobile-Orazio Multifocal motor neuropathy (MMN) is characterized by progressive asymmetric limb weakness usually predominant in the upper limbs associated with conduction block (CB) in motor but not sensory nerves. There are, however, occasional patients with clinically typical MMN in whom no CB can be detected. Whether these patients differ from patients with MMN and CB remains unclear. Since 1991, we have observed 24 patients with the typical clinical features of MMN. In 20 of them (14 men and 6 women), electrophysiological studies disclosed the presence of CB in at least one motor nerve. In four (all women), no evidence of CB could be detected in examined nerves even if three had some features of demyelination, including asymmetric reduction of motor conduction velocities (1 patient) or prolonged or absent F wave latencies (3 patients). Three of them had markedly reduced or absent proximal and distal CMAP amplitudes in some nerves. The mean age of onset of MMN was similar in patients with (41.5 years, range 21,70) and without CB (41.5 years, range 24,57). The mean duration of the disease at the time of our first visit was longer in patients without CB (18.5 years, range 13,25) than in those with CB (6.3 years, 3 months,25 years); only 3 patients with CB had a duration of the disease longer than 10 years. All patients without CB had a predominant or exclusive impairment of upper limbs compared with 18 (90%) of those with CB. The mean Rankin score before therapy was slightly worse in patients without (2.5) than with (2.2) CB. Anti-ganglioside antibodies were found in 1 patient without CB (25%) and in 8 (40%) with CB. All but 2 patients with CB (90%) consistently improved with IVIg. All patients without CB also improved with IVIg, but only one did so consistently. In conclusion, patients with the typical clinical presentation of MMN but no overt CB are clinically and immunologically indistinguishable from those with MMN and CB. The longer duration of the disease and frequent axonal impairment in patients without CB may explain the lower efficacy of IVIg in these patients than in those with CB. [source] Maintenance of Atrial Fibrillation by Pulmonary Vein Tachycardia with Ostial Conduction Block: Evidence of an Interpulmonary Vein Electrical ConnectionJOURNAL OF CARDIOVASCULAR ELECTROPHYSIOLOGY, Issue 10 2008SEIICHIRO MATSUO M.D. We report a case of a 56-year-old man with paroxysmal atrial fibrillation who underwent segmental, ostial pulmonary vein (PV) isolation while in arrhythmia. During isolation of the left superior PV (LSPV), organized electrical activity was seen within the vein, suggestive of a PV tachycardia with a cycle length of 90 ms. Simultaneously, organized electrical activity with a cycle length of 180 ms was seen in the left inferior PV (LIPV), suggestive of 2:1 conduction between the LSPV and the LIPV. Isolation of the LIPV resulted in conversion to sinus rhythm, while confirming isolation of the LSPV by the presence of ongoing PV tachycardia in this vein. This case demonstrates a direct electrical connection between the ipsilateral left PVs, leading to maintenance of atrial fibrillation. [source] Mitral Isthmus Conduction Block After a Single Radiofrequency Application for a Left Concealed Accessory PathwayJOURNAL OF CARDIOVASCULAR ELECTROPHYSIOLOGY, Issue 11 2007MARTIN FIALA M.D., Ph.D. No abstract is available for this article. [source] Paroxysmal Supraventricular Tachycardia with Persistent Ventriculoatrial BlockJOURNAL OF CARDIOVASCULAR ELECTROPHYSIOLOGY, Issue 1 2003BERNHARD STROHMER M.D. Supraventricular Tachycardia with VA Conduction Block. We report the case of a 64-year-old patient with paroxysmal supraventricular tachycardia and persistent VA block. Induction and maintenance of tachycardia occurred without apparent activation of the atria. Diagnostic characteristics were most compatible with AV nodal reentrant tachycardia (AVNRT). Automatic junctional tachycardia and orthodromic nodoventricular or nodofascicular reentry tachycardia were considered in the differential diagnosis. Upper common pathway block during AVNRT may be explained by either intra-atrial conduction block or purely intranodal confined AVNRT. The arrhythmia was cured by a typical posteroseptal ablation approach guided by slow pathway potentials. [source] Conduction block and glial injury induced in developing central white matter by glycine, GABA, noradrenalin, or nicotine, studied in isolated neonatal rat optic nerveGLIA, Issue 11 2009Stavros Constantinou Abstract The damaging effects of excessive glutamate receptor activation have been highlighted recently during injury in developing central white matter. We have examined the effects of acute exposure to four other neurotransmitters that have known actions on white matter. Eighty minutes of Glycine or GABA-A receptor activation produced a significant fall in the compound action potential recorded from isolated post-natal day 10 rat optic nerve. This effect was largely reversed upon washout. Nicotinic acetylcholine receptor (nAChR) or adrenoreceptor activation with noradrenalin resulted in an ,35% block of the action potential that did not reverse during a 30-min washout period. While the effect of nAChR activation was blocked by a nAChR antagonist, the effect of noradrenalin was not ablated by ,- or ,-adrenoreceptor blockers applied alone or in combination. In the absence of noradrenalin, co-perfusion with ,- and ,-adrenoreceptor blockers resulted in nonreversible nerve failure indicating that tonic adrenoreceptor activation is required for nerve viability, while overactivation of these receptors is also damaging. Nerves exposed to nAChR + adrenoreceptor activation showed no axon pathology but had extensive glial injury revealed by ultrastructural analysis. Oligodendroglia exhibited regions of membrane vacuolization while profound changes were evident in astrocytes and included the presence of swollen and expanded mitochondria, vacuolization, cell processes disintegration, and membrane breakdown. Blinded assessment revealed higher levels of astrocyte injury than oligodendroglial injury. The findings show that overactivation of neurotransmitter receptors other than those for glutamate can produce extensive injury to developing white matter, a phenomenon that may be clinically significant. © 2009 Wiley-Liss, Inc. [source] Paraplegia associated with brucellosis involving the anterior lumbrosacral nerve rootsJOURNAL OF THE PERIPHERAL NERVOUS SYSTEM, Issue 1 2003Umit Hidir Ulas Abstract We report the case of a 21-year-old man with paraplegia due to brucellosis involvement of lumbosacral anterior roots. Lumbosacral magnetic resonance imaging showed contrast enhancement of anterior roots and the anterior part of duramater. Conduction block was found at the level of the lumbosacral anterior roots by electrophysiological studies, including magnetic stimulation study. Wright agglutination, Rose Bengal tests and bacterial culture obtained from cerebrospinal fluid confirmed the diagnosis of neurobrucellosis. Oral administration of ceftriaxon with additional rifampin was effective, and after 3 months of treatment, laboratory data resolved and clinical signs partially improved. [source] Electrophysiological sensory demyelination in typical chronic inflammatory demyelinating polyneuropathyEUROPEAN JOURNAL OF NEUROLOGY, Issue 7 2010Y. A. Rajabally Background:, The presence of electrophysiological demyelination of sensory nerves is not routinely assessed in the evaluation of suspected chronic inflammatory demyelinating polyneuropathy (CIDP). Whether this can be useful is unknown. Methods:, We compared, using surface recording techniques, in 19 patients with typical CIDP and 26 controls with distal large fibre sensory axonal neuropathy, the forearm median sensory conductions, sensory nerve action potential (SNAP) amplitudes and durations and sensory nerve conduction velocities (SNCVs) of median, radial and sural nerves. Results:, Median nerve sensory conduction block (SCB) across the forearm was greater in CIDP patients than in controls (P = 0.005). SNAP durations were longer in CIDP patients for median (P = 0.001) and sural nerves (P = 0.004). Receiver operating characteristic (ROC) curves provided sensitive (>40%) and specific (>95%) cut-offs for median nerve SCB as well as median and sural SNAP durations. SNCVs were significantly slower for median and sural nerves in CIDP patients, but ROC curves did not demonstrate cut-offs with useful sensitivities/specificities. Median SCB or prolonged median SNAP duration or prolonged sural SNAP duration offered a sensitivity of 73.7% for CIDP and specificity of 96.2%. Used as additional parameters, they improved diagnostic sensitivity of the American Academy of Neurology (AAN) criteria for CIDP of 1991, from 42.1% to 78.9% in this population, with preserved specificity of 100%. Discussion:, Sensory electrophysiological demyelination is present and may be diagnostically useful in typical CIDP. SCB detection and SNAP duration prolongation appear to represent more useful markers of demyelination than SNCV reduction. [source] A Tissue-Specific Model of Reentry in the Right Atrial AppendageJOURNAL OF CARDIOVASCULAR ELECTROPHYSIOLOGY, Issue 6 2009JICHAO ZHAO Ph.D. Introduction: Atrial fibrillation is prevalent in the elderly and contributes to mortality in congestive heart failure. Development of computer models of atrial electrical activation that incorporate realistic structures provides a means of investigating the mechanisms that initiate and maintain reentrant atrial arrhythmia. As a step toward this, we have developed a model of the right atrial appendage (RAA) including detailed geometry of the pectinate muscles (PM) and crista terminalis (CT) with high spatial resolution, as well as complete fiber architecture. Methods and Results: Detailed structural images of a pig RAA were acquired using a semiautomated extended-volume imaging system. The generally accepted anisotropic ratio of 10:1 was adopted in the computer model. To deal with the regional action potential duration heterogeneity in the RAA, a Courtemanche cell model and a Luo-Rudy cell model were used for the CT and PM, respectively. Activation through the CT and PM network was adequately reproduced with acceptable accuracy using reduced-order computer models. Using a train of reducing cycle length stimuli applied to a CT/PM junction, we observed functional block both parallel with and perpendicular to the axis of the CT. Conclusion: With stimulation from the CT at the junction of a PM, we conclude: (a) that conduction block within the CT is due to a reduced safety factor; and (b) that unidirectional block and reentry within the CT is due to its high anisotropy. Regional differences in effective refractive period do not explain the observed conduction block. [source] First Experiences for Pulmonary Vein Isolation with the High-Density Mesh Ablator (HDMA): A Novel Mesh Electrode Catheter for Both Mapping and Radiofrequency Delivery in a Single UnitJOURNAL OF CARDIOVASCULAR ELECTROPHYSIOLOGY, Issue 4 2009AXEL MEISSNER M.D. Background: Interventional therapy of atrial fibrillation (AF) is often associated with long examination and fluoroscopy times. The use of mapping catheters in addition to the ablation catheter requires multiple transseptal sheaths for left atrial access. Objectives: The purpose of this prospective study was to evaluate feasibility and safety of pulmonary vein (PV) isolation using the high-density mesh ablator (HDMA), a novel single, expandable electrode catheter for both mapping and radiofrequency (RF) delivery at the left atrium/PV junctions. Methods: Twenty-six patients with highly symptomatic paroxysmal AF (14, 53.8%) and persistent AF (12, 46.2%) were studied. Segmental PV isolation via the HDMA was performed using a customized pulsed RF energy delivery program (target temperature 55,60°C, power 70,100 W, 600,900 seconds RF application time/PV). Results: All 104 PVs in 26 patients could be ablated by the HDMA. Segmental PV isolation was achieved with a mean of 3.25 ± 1.4 RF applications for a mean of 603 ± 185 seconds. Entrance conduction block was obtained in 94.2% of all PV. The mean total procedure and fluoroscopy time was 159.0 ± 32 minutes and 33.5 ± 8.6 minutes, respectively. None of the patients experienced severe acute complications. After 3 months no PV stenosis was observed, and 85.6% and 41.6% of the patients with PAF and persistent AF, respectively, did not report symptomatic AF. Conclusions: In this first study of PV isolation using the HDMA, our findings suggest that this method is safe and yields good primary success rates. The HDMA simplifies AF ablation, favorably impacting procedure and fluoroscopy times. [source] Temporary Occlusion of the Great Cardiac Vein and Coronary Sinus to Facilitate Radiofrequency Catheter Ablation of the Mitral IsthmusJOURNAL OF CARDIOVASCULAR ELECTROPHYSIOLOGY, Issue 6 2008ANDRE D'AVILA M.D. Introduction: Ablation of the mitral isthmus to achieve bidirectional conduction block is technically challenging, and incomplete block slows isthmus conduction and is often proarrhythmic. The presence of the blood pool in the coronary venous system may act as a heat-sink, thereby attenuating transmural RF lesion formation. This porcine study tested the hypothesis that elimination of this heat-sink effect by complete air occlusion of the coronary sinus (CS) would facilitate transmural endocardial ablation at the mitral isthmus. Methods: This study was performed in nine pigs using a 30 mm-long prototype linear CS balloon catheter able to occlude and displace the blood within the CS (the balloon was inflated with ,5 cc of air). Using a 3.5 mm irrigated catheter (35 W, 30 cc/min, 1 minute lesions), two sets of mitral isthmus ablation lines were placed per animal: one with the balloon deflated (CS open) and one inflated (CS Occluded). After ablation, gross pathological analysis of the linear lesions was performed. Results: A total of 17 ablation lines were placed: 7 with CS Occlusion, and 10 without occlusion. Despite similar biophysical characteristics of the individual lesions, lesion transmurality was consistently noted only when using the air-filled CS balloon. Conclusions: Temporary displacement of the venous blood pool using an air-filled CS balloon permits transmurality of mitral isthmus ablation; this may obviate the need for ablation within the CS to achieve bidirectional mitral isthmus conduction. [source] Time and Temperature Profile of Catheter Cryoablation of Right Septal and Free Wall Accessory Pathways in ChildrenJOURNAL OF CARDIOVASCULAR ELECTROPHYSIOLOGY, Issue 4 2008JONATHAN R. KALTMAN M.D. Introduction: The overall acute success with cryoablation for accessory pathways (APs) has been reported to be lower than with radiofrequency ablation. Generally, prior cryomapping (limited to ,30°C) has been used to test for loss of AP conduction and absence of atrioventricular (AV) node impairment. However, the temperature at which loss of AP conduction occurs may be variable. The purpose of this study was to evaluate the time and temperature profile at which loss of AP conduction occurs. Methods and Results: A retrospective study evaluated 25 patients (mean age 13.3 ± 3.6 years) who underwent cryoablation for right-sided APs (22 manifest/3 concealed). Direct cryoablation (,80°C) without cryomapping was performed using a "time to success" strategy. If AP conduction was successfully interrupted within 25 seconds of the onset of cryoablation, the lesion was continued for 240 seconds; otherwise it was terminated and further mapping was performed. Cryoablation was successful in 24/25 (96%) patients. Temperature at loss of AP conduction was ,66.2 ±,16.7°C (range +32 to ,84°C) with conduction block at temperatures lower than ,30°C for all but 3 APs. Critical time to success (interval from cryoadherence to loss of AP conduction) was significantly shorter for permanently successful cryolesions, compared with transiently successful lesions (6.3 ± 4.1 vs. 11.2 ± 2.2 sec; P < 0.001). There were no major complications. Conclusions: Cryothermal energy required for successful ablation may be variable and restricting test applications to ,30°may limit its efficacy. A "time to success" strategy may improve outcome of cryoablation for right-sided APs in children without compromising safety. [source] High-Density Mapping of Left Atrial Endocardial Activation During Sinus Rhythm and Coronary Sinus Pacing in Patients with Paroxysmal Atrial FibrillationJOURNAL OF CARDIOVASCULAR ELECTROPHYSIOLOGY, Issue 10 2004TIMOTHY R. BETTS M.D. Introduction: This study was designed to record global high-density maps of left atrial endocardial activation during sinus rhythm and coronary sinus pacing. Method and Results: Noncontact mapping of the left atrium was performed in nine patients with paroxysmal atrial fibrillation undergoing pulmonary vein ablation procedures. High-density isopotential and isochronal activation maps were superimposed on three-dimensional reconstructions of left atrial geometry. Mapping was repeated during pacing from sites within the coronary sinus. Earliest left atrial endocardial activation occurred anterior to the right pulmonary veins in seven patients and on the anterosuperior septum in two patients. A line of conduction block was seen in the posterior wall and inferior septum in all patients. The direction of activation in the left atrial myocardium overlying the coronary sinus was different from the electrogram sequence in the coronary sinus catheter in 6 of 9 patients. During coronary sinus pacing, activation entered the left atrium a mean (SD) of 41 (13) ms after the pacing stimulus at a site 12 (10) mm from the endocardium overlying the pacing electrode. Lines of conduction block were present in the posterior wall and inferior septum. Conclusion: In patients with paroxysmal atrial fibrillation, lines of conduction block are present in the left atrium during sinus rhythm and coronary sinus pacing. Electrograms recorded in the coronary sinus infrequently correspond to the direction of activation in the overlying left atrial myocardium. [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] Paroxysmal Supraventricular Tachycardia with Persistent Ventriculoatrial BlockJOURNAL OF CARDIOVASCULAR ELECTROPHYSIOLOGY, Issue 1 2003BERNHARD STROHMER M.D. Supraventricular Tachycardia with VA Conduction Block. We report the case of a 64-year-old patient with paroxysmal supraventricular tachycardia and persistent VA block. Induction and maintenance of tachycardia occurred without apparent activation of the atria. Diagnostic characteristics were most compatible with AV nodal reentrant tachycardia (AVNRT). Automatic junctional tachycardia and orthodromic nodoventricular or nodofascicular reentry tachycardia were considered in the differential diagnosis. Upper common pathway block during AVNRT may be explained by either intra-atrial conduction block or purely intranodal confined AVNRT. The arrhythmia was cured by a typical posteroseptal ablation approach guided by slow pathway potentials. [source] Cellular Mechanisms of Vagally Mediated Atrial Tachyarrhythmia in Isolated Arterially Perfused Canine Right AtriaJOURNAL OF CARDIOVASCULAR ELECTROPHYSIOLOGY, Issue 9 2002MASAMICHI HIROSE M.D. Mechanism of Vagally Mediated AT.Introduction: Increased vagal tone significantly enhances susceptibility to atrial fibrillation (AF); however, the cellular mechanisms responsible for vagally mediated AF are not completely understood. Methods and Results: In 12 isolated arterially perfused canine right atria, high-resolution optical mapping techniques were used to measure action potentials during control conditions, during intracardiac parasympathetic nerve stimulation (IPS; 30 to 50 Hz) as a surrogate for vagal stimulation, and during acetylcholine (ACh) infusion (10 to 30 ,M). During steady-state pacing, action potential duration was shorter during ACh infusion (43 ± 9 msec) than during IPS (78 ± 7 msec, P < 0.001) or control (129 ± 5 msec, P < 0.001). In contrast, repolarization gradients were larger during IPS (13 ± 3 msec/mm) than during ACh infusion (3 ± 1 msec/mm, P < 0.01) or control (5 ± 1 msec/mm, P < 0.01). Transmural repolarization gradients were relatively small for each intervention tested. During ACh infusion, atrial tachyarrhythmia (AT) was easily initiated with a single premature stimulus and was associated with a focal pattern of activation (84%). AT also was easily initiated by a single premature stimulus during IPS; however, when repolarization gradients were large, patterns of conduction block and incomplete macroreentry were often observed (64%). Importantly, AT initiation during IPS was associated with focal activity (36%) when repolarization gradients were small. Conclusion: In contrast to ACh infusion, IPS generally increased dispersion of repolarization and was often associated with patterns of conduction block and incomplete macroreentry, similar to that associated with in vivo cervical vagal stimulation. However, IPS also was associated with a focal pattern of initiation that was independent of local repolarization gradients. These results suggest that during vagal stimulation, AT initiation does not always depend on repolarization gradients. [source] Aging-Related Increase to Inducible Atrial Fibrillation in the Rat ModelJOURNAL OF CARDIOVASCULAR ELECTROPHYSIOLOGY, Issue 8 2002HIDEKI HAYASHI M.D. Aging and Atrial Fibrillation.Introduction: Aging is associated with atrial interstitial fibrosis and increased incidence of atrial fibrillation (AF). We hypothesized that aged rats are suitable for study of aging-related AF and that partial atrial cellular uncoupling induced with heptanol in young rats mimics aging-related AF. Methods and Results: Interatrial conduction time and atrial response to burst atrial pacing were evaluated in 11 young (2,3 months) and 12 old (22,24 months) male rats (Fisher 344) in the Langendorff-perfused setting. At baseline, sustained (>30 sec) atrial tachycardia (AT) and AF were induced in 10 of 12 and in 7 of 12 old rats, respectively. No such arrhythmias could be induced in the young rats. Old rats had significantly (P < 0.01) longer interatrial conduction time and P wave durations than the young rats. Burst pacing failed to induce AT and AF in all 11 young rats studied. The effects of heptanol 2 to 10 ,M were studied in both groups. Heptanol 2 to 5 ,M promoted inducible AT in all 5 young rats studied; however, when its concentration was raised to 10 ,M, AT could no longer be induced in any of the 5 young rats. No AF could be induced in any of the 5 young rats at heptanol concentrations of 2 to 10 ,M. In the old rats, AF could still be induced during perfusion of 2 ,M heptanol. However, when its concentration was raised to 5 and 10 ,M, AF could not be induced in any of the 6 old rats studied. Optical mapping using a potentiometric dye showed a periodic single wavefront of activation during AT in both groups and 2 to 4 independent wavefronts propagating in different directions during AF in the old rats. Histology revealed a significant increase in interstitial atrial fibrosis (P < 0.01), atrial cell size (P < 0.05), and heart weight in old versus young rats. Fibrosis in the old rats was highly heterogeneous. Conclusion: The rat model is suitable for study of aging-related AF. Uniform partial atrial cellular uncoupling with heptanol perfusion in the young rats, although promoting inducible AT, does not mimic aging-related AF. The results suggest that heterogeneous atrial interstitial fibrosis and atrial cell hypertrophy might contribute to the aging-related increase in atrial conduction slowing, conduction block, and inducible AF in the old rat model. [source] Mechanisms of Transition Between Double Paroxysmal Supraventricular TachycardiasJOURNAL OF CARDIOVASCULAR ELECTROPHYSIOLOGY, Issue 12 2001JEN-YUAN KUO M.D. Double Paroxysmal Supraventricular Tachycardias. Introduction: Coexistence of double tachycardias in one patient has been infrequently reported. Furthermore, the mechanisms of transition between double paroxysmal supraventricular tachycardias have not been well studied. Methods and Results: Thirty-five patients with two paroxysmal supraventricular tachycardias were studied. Group IA consisted of 3 patients with spontaneous transition between AV reciprocating tachycardia (AVRT) and AV nodal reentrant tachycardia (AVNRT). Group IB consisted of 13 patients without spontaneous transition between AVRT and AVNRT. Group IIA consisted of 5 patients with spontaneous transition between AVNRT and atrial tachycardia (AT). Group IIB consisted of 14 patients without spontaneous transition between AVNRT and AT. The absolute values of differences between the two tachycardia cycle lengths were significantly smaller in patients with than in those without transition between the two tachycardias (25 ± 8 msec vs 90 ± 46 msec, P < 0.05, IA vs IB; 21 ± 25 msec vs 99 ± 57 msec, P < 0.01, IIA vs IIB). The cutoff point of 25 msec had 80% positive predictive value for transition between the two tachycardias. Transition between two tachycardias occurred due to a spontaneous premature atrial complex (30%), conduction block at one limb of tachycardia (20%), or tachycardiainduced tachycardia (50%). Absence of transition between two tachycardias might be explained by the absence of a spontaneous premature atrial complex, longer cycle length of the first tachycardia, larger difference between two tachycardia cycle lengths, or induction of each tachycardia under different situations. Conclusion: Double supraventricular tachycardias with similar tachycardia cycle lengths are vulnerable to transition between different tachycardias. [source] Focal Atrial Fibrillation: Experimental Evidence for a Pathophysiologic Role of the Autonomic Nervous SystemJOURNAL OF CARDIOVASCULAR ELECTROPHYSIOLOGY, Issue 5 2001PATRICK SCHAUERTE M.D. Focal AF and Autonomic Nerves.Introduction: Focal paroxysmal atrial fibrillation (AF) was shown recently to originate in the pulmonary veins (PVs) and superior vena cava (SVC). In the present study, we describe an animal model in which local high-frequency electrical stimulation produces focal atrial activation and AF/AT (atrial tachycardia) with electrogram characteristics consistent with clinical reports. Methods and Results: In 21 mongrel dogs, local high-frequency electrical stimulation was performed by delivering trains of electrical stimuli (200 Hz, impulse duration 0.1 msec) to the PVs/SVC during atrial refractoriness. Atrial premature depolarizations (APDs), AT, and AF occurred with increasing highfrequency electrical stimulation voltage. APD/AT/AF originated adjacent to the site of high-frequency electrical stimulation and were inducible in 12 of 12 dogs in the SVC and in 8 of 9 dogs in the left superior PV (left inferior PV: 7/8, right superior PV: 6/8; right inferior PV: 4/8). In the PVs, APDs occurred at 13 ± 8 V and AT/AF at 15 ± 9 V (P < 0.01; n = 25). In the SVC, APDs were elicited at 19 ± 6 V and AT/AF at 26 ± 6 V (P < 0.01; n = 12). High-frequency electrical stimulation led to local refractory period shortening in the PVs. The response to high-frequency electrical stimulation was blunted or prevented after beta-receptor blockade and abolished by atropine. In vitro, high-frequency electrical stimulation induced a heterogeneous response, with shortening of the action potential in some cells (from 89 ± 35 msec to 60 ± 22 msec; P < 0.001; n = 7) but lengthening of the action potential and development of early afterdepolarizations that triggered APD/AT in other cells. Action potential shortening was abolished by atropine. Conclusion: High-frequency electrical stimulation evokes rapid ectopic beats from the PV/SVC, which show variable degrees of conduction block to the atria and induce AF, resembling findings in patients with focal idiopathic paroxysmal AF. The occurrence of the arrhythmia in this animal model was likely due to alterations in local autonomic tone by high-frequency electrical stimulation. Further research is needed to prove absolutely that the observed effects of high-frequency electrical stimulation were caused by autonomic nerve stimulation. [source] Prevalence and significance of Exit Block During Arrhythmias Arising in Pulmonary VeinsJOURNAL OF CARDIOVASCULAR ELECTROPHYSIOLOGY, Issue 4 2000HUNG-FAT TSE M.D. Exit Block. Introduction: Recent studies described the occurrence of conduction block within pulmonary veins. The purpose of this study was to evaluate the prevalence of exit block during arrhythmias that arise in pulmonary veins. Methods and Results: Twenty-five patients with atrial tachycardia/fibrillation underwent successful ablation of 28 arrhythmogenic foci within a pulmonary vein. The prevalence of exit block in the pulmonary veins was determined in 28 arrhythmogenic pulmonary veins and 40 nonarrhythmogenic pulmonary veins. During isolated premature depolarizations, exit block in a pulmonary vein was observed at 50% of arrhythmogenic pulmonary vein sites and was never observed within pulmonary veins that did not generate a tachycardia (P < 0.01). During tachycardia, exit block from a pulmonary vein was observed in 61% of the arrhythmogenic pulmonary veins. The mean cycle length of the pulmonary vein tachycardias associated with exit block was significantly shorter than the cycle length of tachycardia that were not associated with exit block (163 ± 32 vs 251 ± 45 msec, P < 0.001), Exit block in two pulmonary veins during the same episode of tachycardia was observed in 3 of the 28 arrhythmogenic pulmonary veins (11%) in three different patients. Simultaneous recordings in the two pulmonary veins demonstrated bursts of tachycardia in both veins that were not synchronized. Radiofrequency catheter ablation of the arrhythmogenic site in one of the pulmonary veins eliminated spontaneous recurrences of tachycardia from the other pulmonary vein. Conclusion: Exit block from pulmonary veins is a common observation during tachycardias generated within pulmonary veins and indicates that an arrhythmogenic pulmonary vein has been identified. The occurrence of exit block in more than one pulmonary vein most likely is attributable to simultaneous tachycardias, one or both of which may be tachycardia induced and perpetuated by the other. [source] CLINICAL AND IMMUNOLOGICAL FEATURES AND RESPONSE TO IVIg IN PATIENTS WITH CLINICALLY TYPICAL MULTIFOCAL MOTOR NEUROPATHY BUT NO OVERT CONDUCTION BLOCKJOURNAL OF THE PERIPHERAL NERVOUS SYSTEM, Issue 1 2000E. Nobile-Orazio Multifocal motor neuropathy (MMN) is characterized by progressive asymmetric limb weakness usually predominant in the upper limbs associated with conduction block (CB) in motor but not sensory nerves. There are, however, occasional patients with clinically typical MMN in whom no CB can be detected. Whether these patients differ from patients with MMN and CB remains unclear. Since 1991, we have observed 24 patients with the typical clinical features of MMN. In 20 of them (14 men and 6 women), electrophysiological studies disclosed the presence of CB in at least one motor nerve. In four (all women), no evidence of CB could be detected in examined nerves even if three had some features of demyelination, including asymmetric reduction of motor conduction velocities (1 patient) or prolonged or absent F wave latencies (3 patients). Three of them had markedly reduced or absent proximal and distal CMAP amplitudes in some nerves. The mean age of onset of MMN was similar in patients with (41.5 years, range 21,70) and without CB (41.5 years, range 24,57). The mean duration of the disease at the time of our first visit was longer in patients without CB (18.5 years, range 13,25) than in those with CB (6.3 years, 3 months,25 years); only 3 patients with CB had a duration of the disease longer than 10 years. All patients without CB had a predominant or exclusive impairment of upper limbs compared with 18 (90%) of those with CB. The mean Rankin score before therapy was slightly worse in patients without (2.5) than with (2.2) CB. Anti-ganglioside antibodies were found in 1 patient without CB (25%) and in 8 (40%) with CB. All but 2 patients with CB (90%) consistently improved with IVIg. All patients without CB also improved with IVIg, but only one did so consistently. In conclusion, patients with the typical clinical presentation of MMN but no overt CB are clinically and immunologically indistinguishable from those with MMN and CB. The longer duration of the disease and frequent axonal impairment in patients without CB may explain the lower efficacy of IVIg in these patients than in those with CB. [source] Tetrodotoxin-induced conduction blockade is prolonged by hyaluronic acid with and without bupivacaineACTA ANAESTHESIOLOGICA SCANDINAVICA, Issue 1 2004M. F. Stevens Background:, In isolated nerves, tetrodotoxin (TTX) blocks nerve conduction longer than bupivacaine. In vivo, however, both substances block nerve conduction to an equal duration, presumably because the hydrophilic TTX binds only weakly to the perineural tissue. High molecular weight hyaluronic acid (HA) prolongs the action of local anaesthetics several-fold. We tested whether admixture of HA enhances the binding of TTX to the perineural tissue and thus induces an ultralong conduction block after a single application. Methods:, In 12 anaesthetized rabbits, the minimal blocking concentrations of TTX, TTX and HA (TTX/HA) and bupivacaine with HA (bupivacaine/HA) were determined by blocking the natural spike activity of the aortic nerve. In 18 other animals, equipotent concentrations of either TTX, TTX/HA or TTX/bupivacaine/HA were applied topically to the aortic nerve. After disappearance of the spike activity, the wound was closed to simulate the clinical situation of a single shot nerve block. The time until recovery of spike activity was determined. The nerves were examined for signs of neurotoxicity 24 h after the application of the drugs. Data are presented as means ± SD and compared by ANOVA and Student's t -test for unpaired data. Results:, The conduction block by TTX/bupivacaine/HA (10.1 ± 1.9 h) or TTX/HA (9.3 ± 1.0 h) was significantly longer than that of plain TTX (7.9 ± 1.0 h). Neurotoxicity was not observed. Conclusions:, Both HA and HA/bupivacaine prolong the TTX-induced conduction blockade of the aortic nerve of rabbits in vivo. No signs of neurotoxicity were observed. [source] Familial, demyelinating sensory and motor polyneuropathy with conduction blockMUSCLE AND NERVE, Issue 4 2010Stephen N. Scelsa MD Abstract Both multifocal, demyelinating features and prednisone responsiveness are rare in Charcot,Marie,Tooth (CMT) disease. We report a mother and son with a prednisone-responsive, multifocal, demyelinating, predominantly sensory polyneuropathy that was associated with an isoleucine92valine polymorphism of lipopolysaccharide-induced TNF-alpha factor (LITAF). The mother had a multifocal, acquired, demyelinating sensory and motor polyneuropathy (MADSAM)-like presentation. The son developed left peroneal neuropathy during acute Lyme disease with a subsequent relapsing, MADSAM-like illness, despite antibiotic treatment. Both shared prednisone responsiveness and multifocal, demyelinating features electrophysiologically. MADSAM may be familial (FaDSAM) and respond to prednisone. Muscle Nerve 41: 558,562, 2010 [source] Childhood multifocal acquired demyelinating sensory and motor neuropathyMUSCLE AND NERVE, Issue 6 2008Hiroyuki Wakamoto MD Abstract We report the first pediatric cases of multifocal acquired demyelinating sensory and motor neuropathy with electrophysiologic evidence of proximal conduction abnormalities but no definite conduction block. Intravenous immunoglobulin caused clinical improvement followed by long-term remission without maintenance therapy; one patient has exhibited a monophasic course and the other has had a single relapse during the last 5 years. These cases suggest that there may be a long-term sustained beneficial effect of intravenous immunoglobulin therapy for children with this neuropathy. Muscle Nerve, 2008 [source] Frequency-dependent conduction block in carpal tunnel syndromeMUSCLE AND NERVE, Issue 5 2006DScArticle first published online: 31 MAR 200, David Burke MD No abstract is available for this article. [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] Gentle dorsal root retraction and dissection can cause areflexia: Implications for intraoperative monitoring during "selective" partial dorsal rhizotomyMUSCLE AND NERVE, Issue 10 2001Eric L. Logigian MD Abstract During partial dorsal rhizotomy (PDR), intraoperative dorsal rootlet stimulation often evokes nonreflex, rather than reflex, motor responses that are due to costimulation of adjacent ventral roots. Intraoperative areflexia typically predicts that motor responses evoked by dorsal rootlet stimulation are nonreflexive. The cause of areflexia during PDR is in part due to anesthesia, but other mechanisms are likely to play a role as well. In this study of three consecutive patients undergoing lumbosacral neurosurgery, soleus H-reflexes evoked by tibial nerve stimulation at the popliteal fossa were found to suddenly decline in amplitude following retraction and gentle dissection of the S-1 dorsal root. In one areflexic patient, dorsal rootlet stimulation proximal to the main site of dissection evoked soleus H-reflexes, although they could not be evoked by tibial nerve stimulation. We conclude that the gentle retraction and dissection of dorsal rootlets that occurs during PDR can induce conduction block of reflex afferents. High-intensity dorsal rootlet stimulation distal to the site of conduction block may then evoke not reflex responses, but rather nonreflex motor responses, due to the costimulation of adjacent ventral roots. © 2001 John Wiley & Sons, Inc. Muscle Nerve 24: 1352,1358, 2001 [source] Analysis of Atrioventricular Nodal Reentrant Tachycardia with Variable Ventriculoatrial Block: Characteristics of the Upper Common PathwayPACING AND CLINICAL ELECTROPHYSIOLOGY, Issue 4 2009KENJI MORIHISA M.D. Background: The precise nature of the upper turnaround part of atrioventricular nodal reentrant tachycardia (AVNRT) is not entirely understood. Methods: In nine patients with AVNRT accompanied by variable ventriculoatrial (VA) conduction block, we examined the electrophysiologic characteristics of its upper common pathway. Results: Tachycardia was induced by atrial burst and/or extrastimulus followed by atrial-His jump, and the earliest atrial electrogram was observed at the His bundle site in all patients. Twelve incidents of VA block: Wenckebach VA block (n = 7), 2:1 VA block (n = 4), and intermittent (n = 1) were observed. In two of seven Wenckebach VA block, the retrograde earliest atrial activation site shifted from the His bundle site to coronary sinus ostium just before VA block. Prolongation of His-His interval occurred during VA block in 11 of 12 incidents. After isoproterenol administration, 1:1 VA conduction resumed in all patients. Catheter ablation at the right inferoparaseptum eliminated antegrade slow pathway conduction and rendered AVNRT noninducible in all patients. Conclusion: Selective elimination of the slow pathway conduction at the inferoparaseptal right atrium may suggest that the subatrial tissue linking the retrograde fast and antegrade slow pathways forms the upper common pathway in AVNRT with VA block. [source] Delayed Occurrence of Unheralded Phase IV Complete Heart Block After Ethanol Septal Ablation for Symmetric Hypertrophic Obstructive CardiomyopathyPACING AND CLINICAL ELECTROPHYSIOLOGY, Issue 6 2006JOANNA J. WYKRZYKOWSKA Ethanol septal ablation has emerged as a less invasive alternative to surgical myomectomy for treatment of asymmetric hypertrophic obstructive cardiomyopathy (ASH). The procedure has very low mortality, but high-degree AV conduction block is a frequent complication. Prior studies have documented baseline left bundle branch block and high volume of ethanol injection (greater than 4 mL) as risk factors. Complete heart block is often preceded by postprocedure conduction abnormalities and generally develops within 48 hours after ethanol ablation. We present a unique case of a patient with symmetric hypertensive hypertrophic obstructive cardiomyopathy (SHOCM) who developed phase IV complete heart block >96 hours postprocedure without preceding conduction abnormalities or other classic risk factors.3 [source] Atrial Linear Lesions: Feasibility Using CryoablationPACING AND CLINICAL ELECTROPHYSIOLOGY, Issue 3 2006KLAUS KETTERING Background: Long linear lesions are created in the left atrium to modify the atrial substrate, thereby curing atrial fibrillation. The creation of long linear left atrial lesions using radiofrequency (RF) ablation is time consuming and difficult. Furthermore, it might result in significant complications. Cryoablation might overcome some of the disadvantages of RF ablation. Therefore, the aim of our study was to assess whether the creation of a long linear lesion is possible using cryotherapy. Methods: A right atrial septal linear lesion was created in six pigs (median weight: 50 kg; range: 40,60 kg). The ablation procedure was performed with a 7-F Freezor cryocatheter. The nonfluoroscopic mapping system LocaLisa was used as a navigation tool. At each point, freezing was maintained at the lowest attainable temperature (,75°C) for 4 minutes. The CARTO system was used for the evaluation of the linear lesions. Furthermore, all animals were sacrificed immediately after the ablation procedure and a postmortem examination of the lesions was performed. Additionally, an analysis of the amplitudes of the intracardiac electrograms registered via the ablation catheter was performed before and after the ablation procedure. Results: A right atrial septal linear lesion could be created successfully in all six pigs. For the performance of this ablation line, a median number of 16 cryoapplications (range, 11,26) was necessary. The amplitudes of the intracardiac electrograms registered via the ablation catheter decreased significantly after ablation. The CARTO bipolar voltage map revealed very low potentials along the ablation line and showed a sharply demarcated ablation area at the septum in all pigs. Further analysis of the CARTO map revealed an incomplete conduction block in all cases. Most of the pigs had a small gap close to the fossa ovalis. The postmortem examination of 2,3,5-triphenyl-tetrazolium chloride-stained specimens showed sharply demarcated lesions without any ulcerations. There were no major complications during the procedure. Conclusions: The creation of long linear lesions using cryoablation is feasible and safe. Lesion characteristics are different and more favorable than those created by RF. However, the aim of creating a transmural lesion and a complete conduction block remains an unsolved problem even with current cryoablation techniques. Nevertheless, growing experience and technical improvements might overcome some of the current limitations of this new technique. [source] Reentry Within the Cavotricuspid Isthmus: An Isthmus Dependent CircuitPACING AND CLINICAL ELECTROPHYSIOLOGY, Issue 8 2005YANFEI YANG Background: We describe a new cavotricuspid isthmus (CTI) circuit. Methods: This study includes 8 patients referred for atrial flutter (AFL) ablation whose tachycardia circuit was confined to the septal CTI and the os of the coronary sinus (CSOS) region. Entrainment mapping was performed within the CTI, CSOS, and other right atrial annular sites (tricuspid annulus (TA)). Electroanatomic mapping was available in 2 patients. Results: Sustained AFL occurred in all patients with mean tachycardia cycle length (TCL) of 318 ± 54 (276 , 420) ms. During tachycardia, fractionated or double potentials were recorded at either the septal CTI and/or the region of CSOS in all, and concealed entrainment with post-pacing interval (PPI) , TCL , 25 ms occurred in this area; but manifest entrainment with PPI > TCL was demonstrated from the anteroinferior CTI and other annular sites in 7/8 patients. In one, tachycardia continued with conduction block at the anteroinferior CTI during ablation. Up to three different right atrial activation patterns (identical TCL) were observed. The tachycardia showed a counterclockwise (CCW) pattern in 6, a clockwise pattern in 2, and simultaneous activation of both low lateral right atrium and septum in 5. Electroanatomic mapping was available in 2, showing an early area arising from the septal CTI in 1, and a CCW activation sequence along the TA in another. Radiofrequency application to the septal CTI terminated tachycardia in 4, and tachycardia no longer inducible in all. Conclusions: We describe a tachycardia circuit confined to the septal CTI/CSOS region, and hypothesize that this circuit involves slow conduction within the CTI and around the CSOS, which acts as a central obstacle. [source] | |||||||||||||||||||||||||