bluuebunny/crossref_metadata_2025_split huggingface dataset:
Catheter Mounted Coaxially Moveable Ablation Electrode for the Creation of Linear Transmural Endocardial Lesions
Authors: MORGAN JOHN MARK , ROBERTS PAUL RICHARD , ALLEN STUART , GALLAGHER PATRICK JOSEPH , GIBSON CHARLES , CUNNINGHAM ANDREW DAVID 
Published: April 2007

Coaxially Moveable Ablation Catheter. Introduction: Use of a novel ablation catheter for the creation of linear transmural endocardial lesions, which uses a coaxially moving ablation electrode mounted on the terminal portion of a catheter shaft and able to move axially for a distance of up to 4 cm. is reported. Methods and Results: The coaxially moving ablation electrode is moved by a sliding mechanism in the catheter handle. The distal portion of the catheter shaft is steerable. Bipolar or unipolar electrograms can be recorded from electrodes on the catheter tip and the coaxially moving ablation. Radiofrequency (RF) current is delivered to the coaxially moving ablation electrode with thermocouple temperature control. This ablation catheter was evaluated in five (30 to 65 kg) anesthetized pigs and introduced via the venous/arterial systems into the right and left atrium (1 lesion) (using the retrograde aortic approach). The catheter was maneuvered to bring the slide range into apposition with atrial endocardium. The coaxially moving ablation electrode was deployed to the terminal portion of the catheter's slide range and then withdrawn in 2‐mm steps. RF current was delivered to the coaxially moving ablation electrode at each point (maximum temperature 70° C), Postmortem examination of eight endocardial linear lesions (2.2 to 4.1 cm length) was made 1 to 3 hours after creation. Histopathologic examination confirmed transmural myocyte necrosis along the length of the lesion, that included the trabeculated right atrium. Conclusion: We conclude that a catheter using a moveable electrode creates continuous linear transmural lesions and could find clinical application in the therapy of a variety of reentry tachycardia mechanisms.
Radiofrequency Ablation of a Concealed Nodoventricular Mahaim Fiber Guided by a Discrete Potential
Authors: HLUCHY JAN , SCHLEGELMILCH PETER , SCHICKEL STEFAN , JÖRGER URS , JURKOVICOVA OLGA , SABIN GEORG V. 
Published: April 2007

Concealed Nodoventricular Mahaim Fiber. Introduction: We present the case of a 17‐year‐old woman who underwent an electrophysiological study and radiofrequency (RF) ablation of supraventricular tachycardia refractory to medical treatment. Two right‐sided, concealed, nondecremental atrioventricular accessory pathways (AV‐APs) involved in ortho‐dromic circus movement tachycardias were identified. After RF ablation of both AV‐APs, evidence of bidirectional dual AV nodal conduction was demonstrated and regular narrow complex tachycardia was induced. Methods and Results: During the tachycardia, retrograde slow and fast AV nodal pathway conduction with second‐degree ventriculoatrial (VA) block and VA dissociation were observed. During the tachycardia with second‐degree VA block, ventricular extrastimuli elicited during His‐bundle refractoriness advanced the next His potential or terminated the tachycardia. Mapping the right atrial mid‐septal region, a distinct high‐frequency activation P potential was recorded in a discrete area, two thirds of the way from the His bundle toward the os of the coronary sinus. Detailed electrophysiologic testing with the recordahle P potential demonstrated that the tachycardia utilized a concealed nodoventricular AP arising from the proximal slow AV nodal pathway. Conclusion: The tachycardia with slow 1:1 VA conduction could be reset by ventricular extrastimuli elicited during His‐bundle refractoriness advancing the subsequent activation P potential and atrial activation. RF ablation guided by recording of the activation P potential resulted in elimination of both the slow AV nodal pathway and the nodoventricular connection with preservation of the normal AV conduction system.
Thromboembolic Complications of Cardiac Radiofrequency Catheter Ablation
Authors: ZHOU LI , KEANE DAVID , REED GUY , RUSKIN JEREMY 
Published: April 2007

Thromboembolic Complications of Cardiac RF Catheter Ablation. Introduction: Radiofrequency catheter ablation (RFCA) has become established as an effective therapy for the treatment of many cardiac tachyarrhythmias. The principle limitation of conventional RFCA continues to be the risk of thromboembolism. This risk is of particular concern for the ongoing development of the catheter maze procedure for the treatment of atrial fibrillation, which currently involves the creation of extensive linear lesions in the left atrium. Methods and Results: A Medline search of the literature over the last ten years was performed. Focused review of the reported thromboembolic complications of RFCA indicates an overall incidence of 0.6%. However, the risk is increased when ablation is performed in the left heart (1.8% to 2%) and for ventricular tachycardia (2.8%). It is of concern that intravenous heparin and the use of temperature feedback to control radiofrequency current do not eliminate the risk of thromboembolic events. Conclusion: The thromboembolic complications of RFCA are not eliminated by the treatment of intravenous herapin and mode of temperature control during ablation. Potential approaches to further reduce the risk of thromboembolism include the adjunctive administration of specific inhibitors of platelet activation and aggregation, intraprocedural intracardiac echocardiography, irrigated radiofrequency ablation, and cryoablation catheter systems.
Noninvasive Diagnosis in Patients with Undocumented Tachycardias:
Authors: TEBBENJOHANNS JÜRGEN , NIEHAUS MICHAEL , KORTE THOMAS , DREXLER HELMUT 
Published: April 2007

Noninvasive Diagnosis in Patients with Undocumented Tachycardias. Introduction: Patients with symptoms suggestive of paroxysmal supraventricular tachycardia (PSVT) but no tachycardia documentation often undergo diagnostic electrophysiologic study. In dual AV node physiology with AV node reentrant tachycardia (AVNRT), the anterograde fast pathway is more sensitive than the slow pathway to the effects of adenosine. The purpose of the study was to test the hypothesis that adenosine can be used as a bedside test for the diagnosis of dual AV node physiology and hence for AVNRT. Methods and Results: During electrophysiologic study, 37 patients without prior documentation hut symptoms indicative for PSVT received incremental dosages of adenosine during sinus rhythm until second‐degree or greater AV block was observed. Suggestive signs of dual AV node physiology on the surface ECG (sudden jump of PQ interval ≥ 50 msec) were found in 13 (76%) of 17 patients with inducible AVNRT but in only 1 (5%) of the remaining patients (P < 0.01). In the AVNRT group, the maximal increase of the PQ interval between two beats was greater (88 ± 45 msec) than in the remaining 20 patients (17 ± 11 msec) (P < 0.01). Conclusion: Careful evaluation of surface ECG during administration of adenosine helps to identify patients prone to AVNRT. The adenosine test is a valuable noninvasive adjunct in patients with undocumented palpitations suggestive of PSVT
Radiofrequency Catheter Ablation of Frequent Monomorphic Ventricular Ectopic Activity
Authors: SEIDL KARLHEINZ , SCHUMACHER BURGHARD , HAUER BERND , JUNG WERNER , DRÖGEMÜLLER AXEL , SENGES JOCHEN , LÜDERITZ BERNDT 
Published: April 2007

Ablation of Ventricular Ectopic Activity. Introduction: Frequent ventricular ectopic beats can result in severe symptoms and may even be incapacitating in some patients. Although radiofrequency catheter ablation is an effective and safe therapy for drug refractory idiopathic ventricular tachycardia, it has not been widely used in ventricular ectopy. The purpose of this study was: (1) to assess the potential role of catheter ablation in eliminating monomorphic ventricular ectopy in symptomatic patients regarding feasibility and safety and (2) to determine the usefulness of various mapping strategies. Methods and Results: Forty‐one patients with symptomatic ventricular ectopic activity (right ventricular origin in 23 patients, left ventricular origin in 18 patients) were enrolled. The mean frequency of ventricular ectopic beats was 1512 ± 583/hour documented by Holter ECG monitoring. These patients had previously been unable to tolerate or had been unsuccessfully treated with a mean of 3 ± 1 antiarrhythmic agents. The site of origin was mapped using earliest endocardial activation times, unipolar electrograms and pace mapping. Radiofrequency ablation was successful in 34 (83%) of 41 patients. Multivariate logistic regression analysis revealed pace mapping as the only independent predictor for a successful ablation site (P < 0.01). After a follow‐up of 3 months, the overall success rate was 71%. The mean frequency of ventricular ectopic heats after successful ablation was 12 ± 10 ventricular premature beat/hour. Conclusion: Radiofrequency catheter ablation is an effective and safe treatment for frequent symptomatic drug refractory monomorphic ventricular ectopic activity. Pace mapping predicts best successful ablation of ventricular ectopic beats.
A Four‐Shock Bayesian Up‐Down Estimator of the 80% Effective Defibrillation Dose
Authors: MALKIN ROBERT A. , HERRE JOHN M. , McGOWEN LAUREN , TENZER MARTHA M. , ONUFER JOHN R. , STAMATO NICHOLAS J. , WOOD MARK , BERNSTEIN ROBERT C. 
Published: April 2007

Bayesian Estimation of the ED80.Introduction: New defibrillation techniques are often compared to standard approaches using the defibrillation threshold. However, inference from thresholding data necessitates extrapolation from reactions to relatively ineffective shocks, an error prone procedure requiring large sample sizes for hypothesis testing and large safety margins for defibrillator implantation. In contrast, this article presents a clinically validated statistical model of a minimum error, four‐shock defibrillation testing protocol for estimating the 80% effective defibrillation strength for a given patient (ED80).Methods and Results: A Bayesian statistical model was constructed assuming that the defibrillation dose‐response curve is sigmoidal, and the ED80 is between 150 and 750 V. The model was used to design a minimum predicted error testing protocol and estimates. To prospectively validate the testing protocol and estimates, 170 patients received voltage‐programmed biphasic testing. Four fibrillation episodes were induced and terminated in each patient according to the Bayesian up‐down protocol. In addition, a validation attempt was made at the estimated ED80 rounded up to the nearest 50 V. In order to estimate the safety margin, in 136 patients, a defibrillation attempt was made at the rounded ED80 + 100 V. Of the 170 attempts at the rounded ED80, 143 (84%) attempts terminated fibrillation. Of the 136 attempts at the rounded ED80 + 100 V, 133 (98%) were effective.Conclusions: The four‐shock Bayesian up‐down protocol is the first clinical protocol to accurately predict an ED80 voltage. A 100 V increment above the ED80 provides an adequate safety margin. This simple and accurate method for estimating a highly effective defibrillation dose may be a valuable tool for population‐based clinical hypothesis testing, as well as defibrillator implantation.
The Autonomic Control of the Transmural Dispersion of Ventricular Repolarization in Anesthetized Dogs
Authors: TAKEI MANABU , SASAKI YASUYUKI , YONEZAWA TAKANORI , LAKHE MANOJ , ARUGA MASAKAZU , KIYOSAWA KENDO 
Published: April 2007

Autonomic Effects of M Region. Introduction: The initiation of ventricular arrhythmias is in part associated with autonomic nervous tone. We investigated the effects of sympathetic and parasympathetic stimulation on the monophasic action potentials (MAPs) of the epicardium (EPi), mid‐myocardial (M) region, and endocardium (Endo) in vivo. Methods and Results: In 12 mongrel open chest anesthetized dogs, both sides of the cervical vagus nerves and stellate ganglia were crushed with a tight ligature. Right atrial pacing at 600 msec cycle length was begun after the sinus nodal area had been crushed. MAPs from the M region were measured by two needle electrodes that were supported by a W‐shaped plastic frame. The epicardial, M region, and endocardial MAP durations at 90% repolarization (MAPD90) were 287 ± 7, 315 ± 7, and 290 ± 8 msec, respectively. The MAPD90 from M cells was longer than that from Epi or Endo. Sympathetic stimulation shortened MAPD90 more in the M region (53 ± 4 msec) than that in the Epi (27 ± 3 msec) or Endo (26 ± 4 msec). The transmural dispersion of repolarization during sympathetic stimulation was shorter than that of the control. Parasympathetic stimulation did not significantly affect any of the MAPD90 values. Simultaneous sympathetic and parasympathetic stimulation produced changes not significantly to those produced by sympathetic stimulation alone. Conclusion: Our results suggest that sympathetic activity can reduce transmural dispersion of repolarization under autonomic control in the canine heart under baseline conditions.
Junctional Communication Between Isolated Pairs of Canine Atrial Cells is Mediated by Homogeneous and Heterogeneous Gap Junction Channels
Authors: ELENES SERGIO , RUBART MICHAEL , MORENO ALONSO P. 
Published: April 2007

Heterogeneous Cardiac Gap Junction Channels. Introduction: The expression of multiple connexins (Cxs) in the canine right atria raises the possibility that heterogeneous gap junction channels might he formed. Methods and Results: We compared the unitary conductance (γj) of gap junction channels between isolated canine atrial cell pairs with those of homogeneous cardiac gap junction channels expressed in other systems. After partial uncoupling with halothane (2 mmol/L), the γj calculations for atrial isolated cardiocytes ranged from 30 to 220 pS and their distribution in event histograms was spread over the entire range, with a small peak at ∼100 pS. This distribution deviates from the discrete peaks calculated from γj of homogeneous channels. All–points histograms of junctional current traces revealed distinct open–state levels. Some of these are related to the main open state of connexin43 (Cx43) (∼100 pS), observed between canine ventricular cells, or connexin40 (Cx40) (∼215 pS) observed between transfected N2A cells under similar recording conditions. Intermediate values for γj were not observed in recordings from ventricular cells, which express mostly Cx43, nor in those from N2A cells expressing Cx40, but were observed consistently between atrial cells. Because they were measured as first openings from the nonconductance state, these intermediate values most likely represent main conductance states of heterogeneous channels rather than subconductance states of homogeneous channels. Conclusion: This suggests that regulation of cell–to–cell coupling in the heart depends not only on posttranslational modulation of preexisting Cxs, but also on the intracellular assembly mechanisms, and the way individual Cxs interact with others within a connexon and/or with other connexons from adjacent cells.
Dependence of Electrogram Duration in Right Posteroseptal Atrium and Atrium‐Pulmonary Vein Junction on Pacing Site:
Authors: CHEN YI‐JEN , TAI CHING‐TAI , HSIEH MING‐HSIUNG , TSAI CHIN‐FENG , LIN WEI‐SHIANG , CHEN SHIH‐ANN 
Published: April 2007

Right Posteroseptal Atrium and Atrium‐PV Junction. introduction: The fractionated atrial electrogram. a signal helpful in identifying the target site for radiofrequency catheter ablation of the slow AV nodal pathway, is considered to arise from nonuniform anisotropic electrical activity. However, the effects of pacing sites and radiofrequency ablation on these electrograms are not clear. Similarly, the nature of the fractionated atrial electrogram in the atrium‐pumonary vein junction has yet to be determined. Methods and Results: Two experiments were performed in this study. Experiment 1 evaluated the fractionated atrial electrogram at target sites before and after slow AV nodal pathway ablation during sinus rhythm or during pacing from different sites, Group 1A consisted of 16 patients with dual AV nodal pathway physiology and AV nodal reentrant tachycardia who underwent successful ablation without residual slow AV nodal pathway. Group IB consisted of 7 patients who underwent successful elimination of AV nodal reentry but with residual dual AV nodal pathway physiology. Group IC consisted of 6 patients who still had AV nodal reentrant tachycardia after two applications of radiofrequency energy. In Group 1D, there were 16 patients with dual AV nodal pathway physiology, but without inducible AV nodal reentrant tachycardia. In group 1E, there were 15 patients without dual AV nodal pathway physiology. Experiment 2 investigated the fractionated atrial electrogram in the ostium of the left and right superior pulmonary veins I 18 patients with paroxysmal strial fibrillation (2A) and in 8 patients without paroxysmal atrial fibrillation (2B). Before radiofrequency ablation, eletrogram duration in the right posteroseptal atrium during pacing from the middle coronary sinus or the right posterolateral atrium was shorter than that during pacing from the high right atrium (HRA) in all group 1 patients. After the successful elimination of the slow AV nodal pathway conduction in group 1A, atrial electrogram duration during HRA pacing was shorter than that before ablation. In experiment 2 patients, electrogram duration during pacing from the proximal or distal coronary sinus was shorter than that during pacing from HRA or sinus rhythm. Conclusion: These findings suggest that the fractionated atrial electrogrms in the right posteroseptal atrium and ostium of left or right superior pulmonary veins are potentially consistent with nonuniform anisotropic propagation. Alternations of electrogram characteristics after successful radiofrequency ablation of the slow AV nodal pathway may arise from the changes of nonuniform anisotropic activity in the right posteroseptal atrium.
Spatial and Temporal Heterogeneity of Depolarization and Repolarization May Complicate Implantable Cardioverter Defibrillator Therapy in Brugada Syndrome
Authors: STIX GUENTER , BELLA PAOLO DELLA , CARBUCICCHIO CORRADO , SCHMIDINGER HERWIG 
Published: April 2007

ICD Therapy in Brugada Syndrome. Introduction: Dynamic variations in electrophysiologic phenomena inherent to the Brugada syndrome may complicate therapy with implantable cardioverter defibrillators (ICDs). Methods and Results: Between 1997 and 1999, 3 of 7 patients with Brugada syndrome (1 man and 2 women, mean age 42 years) received an ICD. During follow‐up, 2 patients experienced multiple inappropriate shocks. Simultaneously with dynamic changes in the surface ECG, endocardial ECGs revealed a dynamic decrease in the right ventricular R wave and an increase in the corresponding T wave, resulting in T wave oversensing. With ajmaline administration, these dynamic changes in endocardial signals were reproducible at different right ventricular sites, whereas left ventricular epicardial signals remained stable. Incremental AAI pacing and exercise stress testing resulted in similar changes in right ventricular endocardial signals, but normalization of the surface ECG apart from progressively increasing S waves in leads II, V5, and V6. Orciprenaline administration had no effect on ECG phenomena. After implantation of a left ventricular epicardial lead for sensing and pacing, no inappropriate tachycardia detection recurred. Conclusion: These findings demonstrate that, in Brugada syndrome, spontaneous or ajmaline‐induced changes in the surface ECG may be paralleled by significant variations in the right ventricular endocardial electrogram that may result in ICD malfunction. Implantation of a left ventricular epicardial lead for sensing and pacing may be the ultimate successful approach in certain patients. To assure proper ICD function, ajmaline testing during ICD implantation appears to be helpful.
Maturational Atrioventricular Nodal Physiology in the Mouse
Authors: MAGUIRE COLIN T. , BEVILACQUA LAURA M. , WAKIMOTO HIROKO , GEHRMANN JOSEF , BERUL CHARLES I. 
Published: April 2007

Mouse AV Nodal Maturation. Introduction: Dual AV nodal physiology is characterized by discontinuous conduction from the atrium to His bundle during programmed atrial extrastimulus testing (A2V2 conduction curves), AV nodal echo beats, and induction of AV nodal reentry tachycardia (AVNRT). The purpose of this study was to characterize in vivo murine maturational AV nodal conduction properties and determine the frequency of dual AV nodal physiology and inducible AVNRT. Methods and Results: A complete transvenous in vivo electrophysiologic study was performed on 30 immature and 19 mature mice. Assessment of AV nodal conduction included (1) surface ECG and intracardiac atrial and ventricular electrograms; (2) decremental atrial pacing to the point of Wenckebach block and 2:1 conduction; and (3) programmed premature atrial extrastimuli to determine AV effective refractory periods (AVERP), construct A2V2 conduction curves, and attempt arrhythmia induction. The mean Wenckebach block interval was 73 ± 12 msec, 2:1 block pacing cycle length was 61 ± 11 msec, and mean AVERP100 was 54 ± 11 msec. The frequency of dual AV nodal physiology increased with chronologic age, with discontinuous A2V2, conduction curves or AV nodal echo heats in 27% of young mice < 8 weeks and 58% in adult mice (P = 0.03). Conclusion: These data suggest that mice, similar to humans, have maturation of AV nodal physiology, hut they do not have inducible AVNRT. Characterization of murine electrophysiology may be of value in studying genetically modified animals with AV conduction abnormalities. Furthermore, extrapolation to humans may help explain the relative rarity of AVNRT in the younger pediatric population.
Prevalence and Significance of Focal Sources of Atrial Arrhythmia in Patients Undergoing Cardioversion of Persistent Atrial Fibrillation
Authors: TODD DERICK M. , FYNN SIMON P. , HOBBS W. JULIAN , FITZPATRICK ADAM P. , GARRATT CLIFFORD J. 
Published: April 2007

Atrial Arrhythmias After Cardioversion of AF. Introduction: Recent reports have highlighted the importance of focal atrial arrhythmias as a curable cause fur a group of patients with frequently recurrent paroxysmal atrial fibrillation (AF). The importance of this arrhythmia mechanism in the general population of patients with persistent AF is unknown. Methods and Results: After successful internal cardioversion of 50 consecutive patients with persistent AF (mean age 60 years, mean duration of AF 26 months), endocardial activity in the immediate postcardioversion period was analyzed for the presence of focal atria activity. Postcardioversion atrial arrhythmias were considered to be focal if there was evidence of a localized source of repetitive early atrial activation, either in the form of (1) self‐terminating monomorphic atrial tachycardia (at least five heats) or (2) recurrences of AF with an initial atrial activation sequence (first five beats) that was both monomorphic and reproducible with repeated recurrences. Evidence for a focal atrial arrhythmia was present in 20 of the total group of 50 patients (40%). Multivariate analysis of clinical characteristics revealed the diagnosis of lone AF as the only independent predictor of a focal source of AF (P = 0.028). Thirty‐nine patients were discharged from hospital in sinus rhythm. At 1‐month follow‐up. 25 (64%) of these 39 patients had suffered AF recurrence. The only significant predictor of AF recurrence was evidence of a focal source of atrial arrhythmia immediately after cardioversion, with a relative risk of 1.73 (range 1.1 to 2.7: P = 0.015). Conclusion: Focal atrial arrhythmias are common in patients presenting with “idiopathic” persistent AF, suggesting a possible causative role in the generation of this common arrhythmia.