bluuebunny/crossref_metadata_2025_split huggingface dataset:
Prevention of Atrial Fibrillation by Complete Compartmentalization of the Left Atrium Using a Catheter Technique
Authors: ERNST SABINE , OUYANG FEIFAN , SCHNEIDER BIRKE , KUCK KARL‐HEINZ 
Published: April 2007

LA Compartmentalization for AF Prevention. Introduction: Right atrial compartmentalization has been demonstrated to only reduce the number of atrial fibrillation (AF) episodes: left atrial (LA) fibrillation still occurs. Methods and Results: We report successful LA compartmentalization resulting in isolation of all four pulmonary veins in a 51‐year‐old woman suffering from paroxysmal AF. Deployment of a complete encircling line resulted in dissociation of electrical activation within the isolated area from the remaining LA. Despite attempts al reinduction by pacing maneuvers inside and outside the isolated area, AF was no longer inducible. During 2l‐week follow‐up, the patient remained in stable sinus rhythm with rare atrial extrasystoles. Conclusion: If reproducible, this ablation strategy could allow treatment of AF independent of suppression of any triggering event.
Effect of Chronic Amiodarone Therapy on Defibrillation Energy Requirements in Humans
Authors: PELOSI FRANK , ORAL HAKAN , KIM MICHAEL H. , STICHERLING CHRISTIAN , HORWOOD LAURA , KNIGHT BRADLEY P. , MICHAUD GREGORY E. , MORADY FRED , STRICKBERGER S. ADAM 
Published: April 2007

Amiodarone Effect on Defibrillation Energy Requirement. Introduction: The effect of oral amiodarone therapy on defibrillation energy requirements in patients with an implantable defibrillator has not been established. Methods and Results: Twenty‐one consecutive patients with implantable biphasic waveform defibrillators underwent a step‐down determination of the defibrillation energy requirement 211 ± 12 days before and 73 ± 22 days after initiation of amiodarone therapy (mean total dose 26.7 ± 11.1 g). Serum amiodarone and desethylamiodarone concentrations were measured at the time of defibrillation energy requirement determination. The mean defibrillation energy requirement before amiodarone therapy was 9.9 ± 4.6 J. After initiation of amiodarone therapy, the mean defibrillation energy requirement increased to 13.7 ± 5.6 J (P = 0.004). A linear relationship between the amiodarone (P = 0.02, r = 0.6), desethylamiodarone (P = 0.02, r = 0.6), and combined amiodarone‐desethylamiodarone concentrations (P = 0.001, r = 0.6) and the defibrillation energy requirement was noted. Stepwise regression analysis demonstrated that the combined amiodarone‐desethylamiodarone concentration was the only independent predictor of increase in the defibrillation energy requirement. Conclusion: Chronic oral amiodarone therapy increases the defibrillation energy requirement by approximately 62% in patients with an implantable defibrillator. The combined amiodarone‐desethylamiodarone concentration is directly related to the increase in the defibrillation energy requirement.
Atrial Tachycardias Originating from the Atrial Septum:
Authors: CHEN CHIEN‐CHENG , TAI CHING‐TAI , CHIANG CHERN‐EN , YU WEN‐CHUNG , LEE SHIH HUANG , CHEN YI‐JEN , HSIEH MING‐HSIUNG , TSAI CHIN‐FENG , LEE KUNG‐WEI , DING YU‐AN , CHANG MAU SONG , CHEN SHIH ANN 
Published: April 2007

Atrial Tachycardia. Introduction: The characteristics of atrial tachycardia (AT) have varied widely among different reports. The anatomic locations of ATs may bias the results. We propose that septal ATs and free‐wall ATs have different characteristics. Methods and Results: One hundred forty‐one patients with AT underwent electropharmacologic study, endocardial mapping, and radiofrequency ablation. Forty‐nine (34.7%) patients had septal AT originating from the anteroseptal, mid‐septal, and posteroseptal areas. Tachycardia cycle length was similar between septal AT and free‐wall AT (367 ± 46 msec vs 366 ± 58 msec, P > 0.05). More patients with septal AT required isoproterenol to facilitate induction (44.9% vs 31.5%, P < 0.05). Septal AT was more sensitive to adenosine than free‐wall AT (84.4% vs 67.8%, P < 0.05). Only posteroseptal AT showed a positive P wave in lead V, and negative P wave in all the inferior leads (II, III, aVF). Radiofrequency catheter ablation had a comparable success rate for septal AT and free‐wall AT (96% vs 95%) without impairment of AV conduction. During follow‐up of 49 ± 13 months (range 17 to 85), the recurrence rate was similar for septal AT and free‐wall AT (3.2% vs 4.6%, P = 0.08). Conclusion: Septal AT has electrophysiologic characteristics that are distinct from those of free‐wait AT. Catheter ablation of the septal AT is safe and effective.
Temporal Organization of Atrial Activity and Irregular Ventricular Rhythm During Spontaneous Atrial Fibrillation:
Authors: GELZER ANNA R.M. , MOISE N. SYDNEY , VAIDYA DHANANJAY , WAGNER KARIN A. , JALIFE JOSÉ 
Published: April 2007

Temporal Organization of Atrial Activity. Introduction: Atrial fibrillation (AF) is common in healthy horses. We studied the temporal organization of AF to test the hypothesis that the arrhythmia is governed by a high degree of periodicity and therefore is not random in the horse. Further, we surmised that concealed conduction of AF impulses in the AV node results in an inverse relationship between AF frequency and ventricular frequency. Methods and Results: Fast Fourier transform (FFT) analysis of atrial activity was done on signal‐averaged ECGs (n = 11) and atrial electrograms (n = 3) of horses with AF at control (C), after quinidine sulfate (22 mg/kg by mouth every 2 hours) at 50% time to conversion (T50), and immediately before conversion (T90) to sinus rhythm. FFT always revealed a single dominant frequency peak. The mean dominant frequency decreased until conversion (C = 6.84 ± 0.85 Hz, T50 = 4.87 ± 1.5 Hz, T90 = 3.41 ± 1.18 Hz; P < 0.001). Mean AA intervals (n = 5WM gradually increased after quinidine. Mean RR intervals (n = 500), standard deviation of the mean ISDM), Poincaré plots, and serial autocorrelograms (SACs) of 500 RR intervals were measured at C and T90 to determine the ventricular response to AF and quinidine‐induced changes in the variability of the ventricular response. Mean RR interval and SDM were reduced after quinidine (C = 1431 ± 266 msec and 695 ± 23 msec; T90 = 974 ± 116 msec and 273 ± 158 msec, respectively: P < 0.01). Poincaré plots and SAC at C and at T90 revealed a significant correlation of consecutive RR intervals typical of a system with a deterministic behavior. At T90, the variability of RR intervals was reduced and the overall periodicity of RR intervals was increased after quinidine administration. Conclusion: In the horse, AF is a complex arrhythmia characterized by a high degree of underlying periodicity. The inverse AA‐to‐RR interval relationship and reduced variability of RR intervals after quinidine suggest that the ventricular response during AF results from rate‐dependent concealment of AF wavelets bombarding the AV node, which nevertheless results in a significant degree of short‐term predictability of beat‐to‐beat changes in RR intervals.
Existence of Bistability and Correlation with Arrhythmogenesis in Paced Sheep Atria
Authors: OLIVER ROBERT A. , HALL G. MARTIN , BAHAR SONYA , KRASSOWSKA WANDA , WOLF PATRICK D. , TULLOCH ELLEN G. DIXON , GAUTHIER DANIEL J. 
Published: April 2007

Bistability and Arrhythmogenesis in Paced Sheep Atria.Introduction:Studies of the electrical dynamics of cardiac tissue are important for understanding the mechanisms of arrhythmias. This study uses high‐frequency pacing to investigate the dynamics of sheep atria.Methods and Results:A 504‐electrode mapping plaque was affixed to the right atrium in six sheep. Cathodal pacing stimuli were delivered to the center of the plaque. Pacing period (Tp) was decreased from 275 ± 25 msec to 75 ± 25 msec and then increased to 230 ± 70 msec in steps of either 5 or 10 msec. In all 21 trials in six sheep, the atrium responded 1:1 at longer Tps and 2:1 at shorter Tps. As Tpwas decreased, the response switched to 2:1 at a particular Tp. Conversely, as Tpwas increased, the response switched back to 1:1 at a particular Tp. Over 21 trials, the l:1‐to‐2:l and 2:l‐to‐l:l transitions occurred at 119.5 ± 18.8 msec and 130.0 ± 19.1 m.sec, respectively. This hysteretic behavior yielded bistability windows. 10.5 ± 7.2 msec wide, wherein 1:1 and 2:1 responses existed at the same Tp. In 15 trials and in all animals, idiopathic wavefronts emanating from outside the mapped region passed through the mapped region. In 13 of those trials, the idiopathic wavefronts occurred at Tps within the bistability window or within 35 msec of its upper or lower limit.Conclusion:Bistability windows and idiopathic wavefronts were observed and found to be correlated with each other, suggesting a connection between bistability and arrhythmogenesis.
Clinical Characteristics of Patients With Spontaneous or Inducible Ventricular Fibrillation Without Apparent Heart Disease Presenting with J Wave and ST Segment Elevation in Inferior Leads
Authors: TAKAGI MASAHTKO , AIHARA NAOHIKO , TAKAKI HIROSHI , TAGUCHI ATSUSHI , SHIMIZU WATARU , KURITA TAKASHI , SUYAMA KAZUHIRO , KAMAKURA SHIRO 
Published: April 2007

Ventricular Fibrillation with J Wave in Inferior Leads. Introduction: The clinical characteristics of three patients with spontaneous or inducible ventricular fibrillation (VF) without apparent heart disease, who presented with J wave and ST segment elevation in inferior leads, are described. Methods and Results: All patients were male and experienced syncope. Their symptoms occurred at night or early in the morning. Holter ECG revealed infrequent premature ventricular complexes. Injection with disopyramide 2 mg/kg augmented ST segment elevation. Conclusion: These characteristics were very similar to those of patients with Brugada syndrome. These three patients with these specific features might have a variant of Brugada syndrome.
Gender and Seasonally Related Differences in Myocardial Recovery and Susceptibility to Sotalol‐Induced Arrhythmias in Isolated Rabbit Hearts
Authors: SPEAR JOSEPH F. , MOORE E. NEIL 
Published: April 2007

Gender and Seasonal Differences in Rabbit Hearts. Introduction: Gender differences and seasonal variations in cardiac electrophysiology and susceptibility to arrhythmias have been described clinically. The present study was undertaken to determine if there are similar gender and seasonally related differences in the electrophysiology of the rabbit heart. Methods and Results: We analyzed epicardial electrograms, left ventricular endocardial monophasic action potentials (MAPs), and simulated X and Y lead ECGs from 145 isolated rabbit hearts studied over a period of 41 months. Hearts from males had seasonal increases in the duration of myocardial recovery. During the months of June to September compared with October to January and February to May, epicardial activation‐recovery intervals (231.6 ± 23.4 vs 215.6 ± 19.2 and 213.5 ± 18.8 msec, P = 0.003), MAP durations (256.5 ± 25.4 vs 237.0 ± 19.6 and 230.7 ± 26.4 msec, P < 0.001), and QT intervals (278.3 ± 25.6 vs 267.3 ± 11.8 and 261.3 ± 13.0 msec, P = 0.03) were longer. Overall, hearts from females had shorter QT intervals than males (257.7 ± 15.7 vs 270.1 ± 20.3 msec, P < 0.001), and this difference was reflected in their shorter epicardial activationrecovery intervals and MAP durations. However, hearts from females showed a greater prolongation of epicardial recovery (P = 0.007) and greater incidence of arrhythmias (P < 0.001) with sotalol than males. Also, the incidence of arrhythmias was greater in the winter months October to May (P < 0.001). Conclusion: The isolated rabbit heart provides a spontaneous model of gender and seasonally related differences in cardiac electrophysiology and arrhythmia susceptibility. These differences may be related to variation in the expression of or regulation of the membrane ion channels mediating repolarization.
Left Atrial Myocardial Extension onto Pulmonary Veins in Humans:
Authors: SAITO TSUKASA , WAKI KENJI , BECKER ANTON E. 
Published: April 2007

Anatomy of Pulmonary Veins. Introduction: Electrophysiologic studies have shown that spontaneous initiation of atrial fibrillation (AF) by ectopic heats may originate from within pulmonary veins. The extensions of left atrial myocardium are considered to play a role, but there is little detailed anatomic information available. particularly in humans. Methods and Results: Thirty‐nine human autopsy hearts were studied; 22 with AF and 17 without atrial arrhythmias. The muscle fiber arrangement of the left atrial wall and pulmonary veins was dissected. In 18 hearts, myocardial sleeves were studied microscopically; in five hearts, three‐dimensional reconstruction of the fiber arrangement in the myocardial sleeves was performed. Of 99 pulmonary veins examined, 96 contained a myocardial sleeve. The length of the sleeves was largest in the superior pulmonary veins (P < 0.01). There were no statistically significant differences between uniform and nonuniform muscle fiber arrangements. Microscopic evaluation revealed myocardial sleeves positioned on the adventitial side of the pulmonary vein, separated from the muscular media by a fibrofatty tissue plane. The most distal zone of the myocardial sleeves showed increasing fibrosis with encapsulation of small groups of myocardial cells and eventually with total disappearance of atrophic cells within fibrous tissue. Node‐like structures were not encountered. There was no relationship with presence or absence of AF. Conclusion: The observation that the peripheral zones of myocardial sleeves are associated with increasing connective tissue deposition between myocardial muscle groups suggests a degenerative change that, from the histologic viewpoint, fits with progressive ischemia. These changes could provide a basis for microreentry and, hence, for atrial arrhythmias.
Computer Model for Study of Cardiac Repolarization
Authors: BERNARDO DIEGO di , MURRAY ALAN 
Published: April 2007

Computer Model for Cardiac Repolarization. Introduction: We propose a new and simple method to model repolarization in the left ventricle and the corresponding T waves on the surface ECG. Methods and Results: We modeled the cardiac cell action potentials (APs) in the left ventricle (LV) with differences in only the duration of the plateau phase. Using published experimental data on the epicardial and endocardial repolarization sequences, or each point on the left ventricular surface we set a different AP repolarization starting time, determined by the duration of the plateau phase. The surface source model was used to compute potentials on the surface of the torso, generated by repolarization of the LV. Both the torso and the LV had homogeneous and isotropic conductivity. We simulated T waves on the 12‐lead ECG and compared our results with measured T waves from five normal subjects. The orientation and shape in each lead were reproduced. In each lead we computed the root mean square error between simulated and measured T waves. The average error across the 12 leads was small, with a mean value of 0.11 mV across all the subjects. Conclusion: Repolarization of the LV can be modeled independently of the depolarization sequence and AP duration gradients. This method is an easy and powerful tool to describe the ECG features of repolarization.
Marked Reduction of Ventricular Defibrillation Threshold by Application of an Auxiliary Shock to a Catheter Electrode in the Left Posterior Coronary Vein of Dogs
Authors: KENKNIGHT BRUCE H. , WALKER ROBERT G. , IDEKER RAYMOND E. 
Published: April 2007

Ventricular Defibrillation with Coronary Venous Electrode. Introduction: For endocardial shocks near the defibrillation threshold (DFT), postshock activity originates from the lateral left ventricular apex, where the shock field is weak. This study tested the hypothesis that an auxiliary shock (AS) delivered between an electrode at this site and a superior vena cava (SVC) electrode before the primary endocardial shock (PS) would reduce the DFT. Methods and Results: In six pentobarbital‐anesthetized dogs (26 to 36 kg), catheter electrodes were placed in the right ventricular (RV) apex and the SVC. To simulate transvenous introduction, a small electrode was inserted into the posterior cardiac vein using an epicardial approach. For dual shock treatments. AS (2‐m.sec monophasic) was applied to the coronary vein electrode at different time intervals before a biphasic PS (4 msec/3 msec) to the RV‐SVC electrodes. The mean DFT energy for dual shocks treatments were significantly reduced (P < 0.05) in comparison to the control treatment (no AS, 26.5 ± 8.8 J). Mean DFT energy after 10 seconds of electrically induced ventricular fibrillation for dual shocks, in which AS and PS were separated by 1, 5, 10, and 20 msec, were 10.2 ± 4.1 J, 10.9 ± 5.5 J, 11.3 ± 6.3 J, and 15.4 ± 7.2 J, respectively. These values were all significantly lower than the PS alone (26.5 ± 8.8 J). Conclusion: Addition of an AS from the posterior cardiac vein before an endocardial PS reduces DFT energy by more than 50%. Such DFT reduction could improve therapeutic safety margin or permit reduction in volume of implantable cardioverter defibrillators.
New Approach to Biphasic Waveforms for Internal Defibrillation:
Authors: YAMANOUCHI YOSHIO , FISHLER MATTHEW G. , MOWRHY KENT A. , WILKOFF BRUCE L. , MAZGALEV TODOR N. , TCHOU PATRICK J. 
Published: April 2007

Internal Defibrillation with Fully Discharging Capacitors. Introduction: The use of two independent, fully discharging capacitors for each phase of a biphasic defibrillation waveform may lead to the design of a simpler, smaller, internal defibrillator. The goal of this study was to determine the optimal combination of capacitor sizes for such a waveform. Methods and Results: Eight full‐discharge (95/95% tilt), biphasic waveforms produced by several combinations of phase‐1 capacitors (30, 60, and 90 μF) and phase‐2 capacitors (1/3, 2/3, and 1.0 times the phase‐1 capacitor) were tested and compared to a single‐capacitor waveform (120 μF, 65/65% tilt) in a pig ventricular fibrillation model (n = 12, 23 ± 2 kg). In the full‐discharge waveforms, phase‐2 peak voltage was equal to phase‐1 peak voltage. Shocks were delivered between a right ventricular lead and a left pectoral can electrode. E50s and V50s were determined using a ten‐step Bayesian process. Full‐discharge waveforms with phase‐2 capacitors of ≥40 μF had the same E50 (6.7 ± 1.7 J to 7.3 ± 3.9 J) as the single‐capacitor truncated waveform (7.3 ± 3.7 J), whereas waveforms with phase‐2 capacitors of ≥60 μF had an extremely high E50 (14.5 ± 10.8 J or greater, P < 0.05). Moreover, of the former set of energy‐efficient waveforms, those with phase‐1 capacitors of ≥60 μF additionally exhibited V50s that were equivalent to the V50 of the single‐capacitor waveform (344 ± 65 V to 407 ± 50 V vs 339 ± 83 V). Conclusion: Defibrillation efficacy can be maintained in a full‐discharge, two‐capacitor waveform with the proper choice of capacitors.
Mini‐Maze Suffices as Adjunct to Mitral Valve Surgery in Patients with Preoperative Atrial Fibrillation
Authors: TUINENBURG ANTON E. , VAN GELDER ISABELLE C. , TIELEMAN ROBERT G. , GRANDJEAN JAN G. , HUET ROLE C.G. , VAN DER MAATEN JOOST M.A.A. , PIEPER ELS G. , DE KAM PIETER J. , EBELS TJARK , CRIJNS HARRY J.G.M. 
Published: April 2007

Mini‐Maze and Mitral Valve Surgery. Introduction: After mitral valve (MV) surgery, preoperative atrial fibrillation (AF) often recurs while cardioversion therapy generally fails. Additional Cox maze surgery improves postoperative arrhythmia outcome, but the extensive nature of such an approach limits general appliance. We investigated the clinical outcome of a simplified, less extensive Cox maze procedure (“mini‐maze”) as adjunct to MV surgery. Methods and Results: Thirteen patients with MV disease and preoperative AF were treated with combined surgery (group 1). Nine control patients without previous AF underwent isolated MV surgery (group 2). We retrospectively compared the results to findings in 23 patients with preoperative AF who had undergone isolated MV surgery (group 3). In group 1, mini‐maze took an additional 46 minutes of perfusion time. One 75‐year‐old patient died of postoperative multiple organ failure. Seven patients showed spontaneously converting (within 2 months) postoperative AF. After 1 year, 82% were in sinus rhythm (SR). No sinus node dysfunction was observed. In group 2, all patients were in SR after 1 year. In group 3, only 53% were in SR after 1 year, despite serial cardioversion and antiarrhythmic drug therapy. Exercise tolerance and heart rate were comparable for groups 1 and 2. Left atrial function was present in all but one patient in group 1 and in all patients in group 2 (after MV reconstruction). Conclusion: Adding a relatively simple mini‐maze to MV surgery improves arrhythmia outcome in patients with preoperative AF without introducing sinus node dysfunction or persistent absence of left atrial function. The results of this type of combined surgery are encouraging and deserve further attention.
Mechanism for Site‐Dependent Differences in the Shape of the Resetting Response Curve in Fixed Barrier Reentry
Authors: INGELMO CHRISTOPHER , FRAME LAWRENCE H. 
Published: April 2007

Site Dependence of Resetting Response Curves. introduction: We investigated whether the site of stimulation within a reentrant circuit affects the resetting response curve (RRC). RRCs are used to characterize the excitable gap of reentrant circuits, including the duration of the fully excitable gap and the presence of partially excitable tissue. Methods and Results: We reset proximal and distal to a site of interval‐dependent conduction (IDC) in canine in vitro atrial tricuspid rings. Adjustable reentry allowed changes in the cycle length and direction of reentry. In nine preparations we reset 26 tachycardias. In the 16 tachycardias with one site of IDC, RRCs were significantly different when stimulating distal and proximal to a site of interval‐dependent conduction. For the distal curves, the duration of the flat portion was 42 ± 26 msec greater (P < 0.001), the slope of the increasing portion was 0.20 ± 0.17 less (P < 0.02), and the increase in the return cycle was 14 ± 9 msec less (P < 0.001). These differences resulted from early activation of the site of IDC by the antidromic premature impulse when stimulating from distal sites. As a result, the coupling interval of the orthodromic impulse at the site of IDC was the same or greater than at the stimulation site. In 10 tachycardias with multiple sites of IDC, significant differences in the resetting responses did not occur even when the antidromic impulse penetrated one site of IDC. Conclusion: In a fixed anatomic barrier reentrant circuit with one site of IDC, resetting distal to this site misrepresents the properties of the excitable gap of the entire circuit.