bluuebunny/crossref_metadata_2025_split huggingface dataset:
Histopathologic Exploration of Intra‐Hisian Conduction Disturbances
Authors: MATSUYAMA TAKA‐AKI , INOUE SHIN , KOBAYASHI YOUICHI , SAITO TSUKASA , TANNO KAORU , SAKAI TETSUO , OTSUKA TOSHIHIKO , SHIOKAWA AKIRA , KATAGIRI TAKASHI , OTA HIDEKAZU 
Published: August 2003

Pathology of Intra‐Hisian Block.
Introduction: The length of the His bundle and the precise location of injury responsible for split His potentials have not been fully established in patients with intra–Hisian block. We conducted an autopsy study comparing histologic findings in intra‐Hisian block versus control hearts. Methods and Results: We studied hearts from 4 intra‐Hisian block patients (age 66 to 93 years, mean 79.5) and hearts from 14 patients without AV conduction abnormalities (control). All intra‐Hisian block patients underwent electrophysiologic evaluation; 3 patients demonstrated intra‐Hisian block and 1 showed no His potential. Autopsies were performed when each patient died. After the heart was fixed in formaldehyde, the AV septal junctional area was removed en bloc and serially sectioned into 7‐μm thick slices. For study purposes, we considered the three segments of the His bundle separately: the penetrating bundle, the nonbranching bundle, and the branching bundle. The actual length of each segment was calculated from the number of respective serial sections, and the lesion was reconstructed within the conduction axis. Intra‐Hisian block hearts were heavier than control hearts (mean weight 389 vs 301 g; P < 0.05). The lesion was situated in the nonbranching bundle in 3 hearts and in the penetrating bundle in 1 heart. Mean compact node length was 3.8 mm in intra‐Hisian block hearts and 3.3 mm in control hearts. The penetrating bundle was 2.1 and 2.1 mm, the nonbranching bundle was 3.5 and 1.9 mm, and the branching bundle was 4.5 and 4.6 mm in intra‐Hisian block and control hearts, respectively. Conclusion: Most lesions were observed in the nonbranching bundle adjacent to the junction between the central fibrous body and ventricular septum. This segment was longer in intra‐Hisian block hearts than in control hearts.
Supervulnerable Phase Immediately After Termination of Atrial Fibrillation
Authors: DUYTSCHAEVER MATTIAS , DANSE PETER , ALLESSIE MAURITS 
Published: August 2003

Supervulnerable Phase After Termination of AF.
Introduction: Recent studies with the implantable atrial cardioverter have shown that atrial fibrillation (AF) recurs almost immediately after successful cardioversion in about 27% of cases. In the present study, we determined the electrophysiologic properties of the caprine atrium immediately after spontaneous termination of AF both before and after 48 hours of AF‐induced electrical remodeling. Methods and Results: In eight goats, atrial effective refractory period (AERP), intra‐atrial conduction velocity, and atrial wavelength were measured during sinus rhythm both before (t = 0) and after 48 hours (t = 48) of electrically maintained AF (baseline). After baseline, a 5‐minute paroxysm of AF was induced, during which the refractory period (RPAF) was determined. AERP, conduction velocity, and atrial wavelength also were measured immediately after spontaneous restoration of sinus rhythm (post‐AF values). Both in normal and remodeled atria, immediately after AF, AERP and conduction velocity were markedly decreased compared with baseline (P < 0.01). In normal atria, post‐AF AERP (107 ± 14 msec) gradually prolonged from its AF value (114 ± 17 msec) to its baseline value (138 ± 13 msec). Conduction velocity decreased from 130 ± 9 cm/sec to 117 ± 9 cm/sec. After 48 hours of AF, AERP had shortened to 74 ± 8 msec. RPAF was 89 ± 9 msec. Surprisingly, immediately after termination of AF, AERP shortened further to 58 ± 6 msec (P < 0.01). Post‐AF conduction velocity decreased from 136 ± 11 cm/sec to 122 ± 10 cm/sec (P < 0.01). As a result, the post‐AF atrial wavelength became as short as 7.1 ± 1 cm. These changes were transient, and all parameters gradually returned to baseline within 1 to 2 minutes after conversion of AF. Conclusion: Due to a combined decrease in AERP and conduction velocity, marked shortening of the atrial wavelength occurs during the first minutes after conversion of AF. In electrically remodeled atria, this results in a transient ultrashort value of AERP (< 60 msec) and atrial wavelength (7.1 cm). These observations imply a highly vulnerable substrate for reentry immediately after termination of AF. During this supervulnerable phase, both early and later premature beats reinitiated immediate recurrences of AF.
Effects of Estrogen on Cardiac Electrophysiology in Female Mice
Authors: SABA SAMIR , ZHU WEI , ARONOVITZ MARK J. , ESTES N.A. MARK , WANG PAUL J. , MENDELSOHN MICHAEL E. , KARAS RICHARD H. 
Published: August 2003

Estrogen and Cardiac Electrophysiology.
Introduction: Understanding the molecular mechanisms that underlie gender‐ and hormonal‐related differences in susceptibility to cardiac arrhythmias has been hampered by the lack of a suitable animal model. We examined the effect of hormonal status on the electrophysiologic (EP) properties of the mouse heart in an in vivo, closed chest model. Methods and Results: Fifty‐three female C57/J mice aged 10 to 12 weeks were studied. Thirty‐six mice underwent bilateral ovariectomies; 18 received estrogen (OVX + E) and 18 received placebo (OVX). Seventeen female mice underwent only sham surgery. All animals underwent in vivo EP studies. Select EP parameters were measured after quinidine treatment. Data were analyzed by a blinded observer. Compared with the intact female mice, the PR and AH intervals were significantly shorter in the OVX mice, and these parameters normalized with estrogen replacement (PR = 45.9 ± 4.5 msec in the intact mice, 42.1 ± 4.3 msec in the OVX group, and 46.9 ± 3.5 msec in the OVX + E group, P < 0.005; AH = 36.5 ± 4.9 msec in the intact mice, 34.4 ± 4.7 msec in the OVX group, and 38.8 ± 2.7 msec in the OVX + E group, P = 0.03). The right ventricular effective refractory period was significantly shorter in the OVX mice versus the intact mice, and this also normalized with estrogen replacement. Hormonal status did not significantly affect any other EP variable, including QT interval. Conclusion: In female mice, estrogen prolongs AV nodal conduction and the right ventricular effective refractory period. Taken together, these data suggest that hormonal status affects aspects of cardiac EP function. Future application of this mouse model will be helpful in determining the molecular pathways that mediate hormonal differences in cardiac EP.
Temporal Patterns of Atrial Arrhythmia Recurrences in Patients with Implantable Defibrillators: Implications for Assessing Antiarrhythmic Therapies
Authors: SHEHADEH LINA A. , LIEBOVITCH LARRY S. , WOOD MARK A. 
Published: August 2003

Temporal Patterns of Atrial Arrhythmias.
Introduction: The statistical measures commonly used to assess therapies for recurrent atrial arrhythmias (such as time to first recurrence) often assume a uniformly random pattern of arrhythmic events over time. However, the true temporal pattern of atrial arrhythmia recurrences is unknown. The aim of this study was to use linear and nonlinear analyses to characterize the temporal pattern of atrial arrhythmia recurrences in patients with implantable cardioverter defibrillators. Methods and Results: The time and date of atrial tachyarrhythmias recorded in 65 patients with combined atrial and ventricular defibrillators were used to construct a probability density function (PDF) and a model of a Poisson distribution of arrhythmic events for each patient. Average patient age was 66 ± 10 years and follow‐up was 7.8 ± 4.8 months. A total of 10,759 episodes of atrial tachyarrhythmias were analyzed (range 43 to 618 episodes per patient). The PDF fit a power law distribution for all 65 patients, with an average r2= 0.89 ± 0.08. The PDF distribution differed significantly from the model Poisson distribution in 47 of 65 patients (P = 0.0002). Differences from the Poisson distribution were noted for patients both taking (30/43 patients; P < 0.015) and not taking (17/22 patients; P < 0.017) antiarrhythmic drugs. Median time between atrial arrhythmia detections for all 65 patients was 10.8 minutes. Conclusion: In implantable cardioverter defibrillator patients, the temporal pattern of frequent recurrences of atrial tachyarrhythmias usually is characterized by a power law distribution. The unique statistical properties of this type of distribution should be considered in designing outcome measures for treatment of atrial tachyarrhythmias.
Epicardial Foci of Atrial Arrhythmias Apparently Originating in the Left Pulmonary Veins
Authors: KATRITSIS DEMOSTHENES , GIAZITZOGLOU ELEFTHERIOS , KOROVESIS SOCRATES , PAXINOS GEORGE , ANAGNOSTOPOULOS CONSTANTINE E. , CAMM A. JOHN 
Published: August 2003

Epicardial Foci of Atrial Arrhythmias.
Introduction: Epicardial potential sources of atrial arrhythmias, such as the ligament of Marshall, are in close proximity with, and electrically connected to, the left superior pulmonary vein. Ectopic activity arising from these areas may be difficult to differentiate from ectopy that, according to endocardial only mapping, originates in the left superior pulmonary vein. We hypothesized that in patients with paroxysmal atrial fibrillation (AF) apparently originating in the left pulmonary veins, mapping through the distal coronary sinus might identify possible epicardial locations of the arrhythmogenic focus. Methods and Results: Forty patients (age 48 ± 12 years) who underwent catheter ablation for paroxysmal AF were studied by epicardial mapping through the distal, superoposterior coronary sinus. Catheterization of the distal coronary sinus in order to approach the ostium of the left superior pulmonary vein was feasible in 14 of 19 patients with AF originating in the left superior vein (11 patients) or inferior pulmonary vein (3 patients) according to endocardial mapping criteria. In 2 patients, the sole focus of atrial tachycardia/fibrillation was epicardial with earliest activation clearly preceding electrograms recorded at the os of the left superior pulmonary vein or any other endocardial mapping site. Epicardial potentials separated from atrial electrograms were present during sinus rhythm in both patients and during atrial tachycardia in one patient. Catheter ablation through the coronary sinus rendered the arrhythmia noninducible in both patients without abolishing epicardial potentials in one of them. Conclusion: In patients with paroxysmal AF apparently originating from the left superior or inferior pulmonary vein, detailed epicardial mapping through the distal coronary sinus might identify epicardial locations of the arrhythmogenic focus.
Pediatric Radiofrequency Catheter Ablation Registry Success, Fluoroscopy Time, and Complication Rate for Supraventricular Tachycardia: Comparison of Early and Recent Eras
Authors: KUGLER JOHN D. , DANFORD DAVID A. , HOUSTON KRIS A. , FELIX GARY 
Published: August 2003

Ablation Outcomes for Supraventricular Tachycardia.
Introduction: To assess changes of success rate, fluoroscopy time, and complication rate for six supraventricular tachycardia pathways/mechanisms, data from the Pediatric Radiofrequency Catheter Ablation Registry were grouped into two eras (1991–1995; 1996–1999). Methods and Results: Data from the early era and the late era were compared using the Chi‐square test for the outcomes of success rate and complication rate and using the Student's t‐test for the outcome of mean fluoroscopy time. In the Registry as a whole, ablation failure rates fell from 9.6% in the early era to 4.8% in the recent era, a reduction of 50% overall. Improved success rates were found for posterior septal, right free‐wall, and left free‐wall pathways and for AV nodal reentry, whereas anterior septal pathways and atrial ectopic‐focus tachycardia did not show improvement. Mean fluoroscopy time overall decreased 21% from 50.9 ± 39.9 minutes to 40.1 ± 35.1 minutes. Individually, the improvement in fluoroscopy time was found for all but the atrial ectopic‐focus tachycardia mechanism. The complication rate decreased from 4.2% to 3.0%, with significant decreases for left free‐wall and posterior septal pathways. Conclusion: Patient selection strategies to optimize radiofrequency ablation outcomes in children, which have been based on the previously published Registry data, should be reconsidered in light of these new, updated data. The lack of uniform improvement provides the impetus for further research and development of new approaches and technologic advances so that further improvement can be achieved.
Determinants of First‐Shock Success for Atrial Implantable Cardioverter Defibrillators
Authors: SWERDLOW CHARLES D. , SCHWARTZMAN DAVID , HOYT ROBERT , BAILIN STEVEN J. , KOEHLER JODI L. , WARMAN EDUARDO N. 
Published: August 2003

Atrial Defibrillation.
Introduction: The aim of this study was to identify determinants of first‐shock success for defibrillation of spontaneous atrial fibrillation (AF) in ambulatory patients with an atrial implantable cardioverter defibrillator (ICD). The determinants of first‐shock success in ambulatory patients with atrial ICDs are unknown. Methods and Results: We used the generalized estimating equation method to analyze determinants of first‐shock success in 50 consecutive atrial ICD recipients in whom DFT+ (weakest shock that defibrillates on two consecutive trials) was determined at implant and spontaneous AF was shocked with shock strength > 2 × DFT+. DFT+ was 6.2 ± 3.1 J. Of 470 first shocks, 407 were successful (generalized estimating equation 85%, confidence interval 79% to 90%). Determinants of first‐shock success were use of coronary sinus electrode (univariate P = 0.02; multivariate P < 0.001, relative risk 5.0), absence of a Class III antiarrhythmic drug (univariate P = 0.06; multivariate P < 0.001, relative risk 3.2), absence of early recurrence of atrial fibrillation (ERAF; univariate P = 0.06; multivariate P = 0.02, relative risk 2.9), and longer duration of AF prior to shock > 3 hours (univariate: P = 0.02; multivariate P = NS). Sinus rhythm > 1 minute persisted after 93% of first shocks in patients without documented ERAF but after only 58% of shocks in patients with documented ERAF (P < 0.001). Conclusion: Reducing ERAF is critical to achieving a clinically acceptable rate of persistent sinus rhythm after first shocks. For first shocks > 2 × DFT+, success is not increased by programming stronger shocks. Early cardioversion does not increase first‐shock success.
Large Sample Test of Defibrillation Waveform Sensitivity
Authors: MALKIN ROBERT A. 
Published: August 2003

Defibrillation Waveform Sensitivity.
Introduction: An unknown mechanism causes defibrillation efficacy to be sensitive to the temporal pattern (waveform) of the delivered energy. Using a guinea pig model, we tested hypotheses in 140 defibrillation waveforms. Methods and Results: Two hundred seven male guinea pigs (950 ± 100 g) were instrumented to continuously monitor the ECG and an optical plethysmographic signal from a forepaw. Two amplifiers served as a voltage‐based defibrillator with a maximum output of 400 V at 2 A. Defibrillation electrodes (12‐mm diameter) were placed 40 mm apart on the thorax. Thirty ventricular fibrillation episodes were induced where the first 10 episodes were used to estimate ED50 for a biphasic pulse (7/2 msec) and the remaining episodes were defibrillated with 18 test waveforms and two control waveforms all at the ED50 energy. Seven groups of 20 waveforms were tested. We directly tested hypotheses based on charge banking/burping, frequency concentration, and stimulus strength/duration. Of the hypotheses tested, nine are able to predict at least a 10% change in efficacy (P < 0.05): parabolic fit to duration; maximum, minimum, and remaining delivered charge; power at peak frequency; stimulus charge; and maximum, minimum, and maximum of the absolute value of stimulus strength. However, of these, only three are independent predictors of waveform efficacy (P < 0.05, near‐minimum residual variance): power at peak frequency; parabolic fit to the stimulus duration; and minimum stimulus strength. Conclusion: Stimulus strength and duration are the main determinants of the efficacy of a defibrillation waveform.
Linear Lesions Provide Protection from Atrial Fibrillation Induction with Rapid Atrial Pacing
Authors: AVITALL BOAZ , URBONAS ARVYDAS , URBONIENE DALIA , ROZMUS GRZEGORZ , HELMS RAY 
Published: August 2003

Linear Lesions Prevent Atrial Fibrillation.
Introduction: In the animal model, segmentation of the atria with radiofrequency‐generated linear lesions (LL) using the loop catheter has been shown to be highly effective in terminating chronic atrial fibrillation (AF). This study addresses the question whether the same lesion set also would prevent reinduction and sustainability of AF. Methods and Results: We studied two groups of dogs. The AF group included eight dogs in which the atria were paced until chronic AF was present. After 6 months of sustained AF, the dogs were converted to normal sinus rhythm (NSR) by the creation of LL in both atria. Rapid atrial pacing was restarted 6 months later and continued for 4 weeks. In the NSR group, there were nine dogs in NSR without inducible AF at baseline. LL were created, and after 6 months rapid atrial pacing was applied for 4 weeks. Rhythm status was monitored weekly. Transthoracic echocardiography was performed at baseline, before linear lesion placement, and before pacing/repacing. At the conclusion of the study, the hearts were excised and examined. The lesions were stained, and their quality was assessed. AF was induced in a much shorter interval in the dogs in which AF had previously been present than in NSR dogs (8 ± 5 days vs 25 ± 13 days; P < 0.05). LL prevented sustainability of AF induced via rapid pacing once the pacing stimulus was stopped. Incomplete lesions were associated with increased inducibility of atrial tachycardia and AF. Conclusion: In this animal model of AF, LL are not only capable of terminating chronic AF, but also lead to self‐termination of AF once the rapid pacing is stopped. Self‐termination of AF after induction with rapid pacing was not observed in this AF model in the absence of LL. In the dogs with 6 months of AF, the presence of AF led to increased atrial susceptibility to AF induction by rapid pacing, even with LL and after 6 months of recovery. Incomplete LL allows induction of atrial tachycardia and AF.
Characterization of Paroxysmal and Persistent Atrial Fibrillation in the Human Left Atrium During Initiation and Sustained Episodes
Authors: NDREPEPA GJIN , KARCH MARTIN R. , SCHNEIDER MICHAEL A.E. , WEYERBROCK SONJA , SCHREIECK JÜRGEN , DEISENHOFER ISABEL , ZRENNER BERNHARD , SCHÖMIG ALBERT , SCHMITT CLAUS 
Published: August 2003

Characterization of AF in the LA.
Introduction: Atrial fibrillation (AF) in the left atrium (LA) is poorly defined in terms of regional differences in the degree of organization, characteristics of paroxysmal and persistent variants, and electrophysiologic events that develop at the onset of episodes. Methods and Results: The study population consisted of 21 patients (15 men and 6 women; mean age 58 ± 9.4 years) with paroxysmal (10 patients) or persistent (11 patients) AF. Mapping of the LA during sustained episodes and the onset of AF was performed with a 64‐electrode basket catheter. At the onset of AF, repetitive beats starting with atrial premature complexes and ending with generation of the earliest fibrillatory activity were defined as intermediary rhythm. Patients with paroxysmal AF had longer AF cycle lengths and more pronounced regional differences than patients with persistent AF. In total, AF cycle lengths in the LA in patients with persistent AF were 20% shorter than in patients with paroxysmal AF. Initiation of AF was preceded by an intermediary rhythm of 5.5 ± 2.5 cycles (6.3 ± 2.7 cycles in paroxysmal AF vs 4.2 ± 1.0 cycles in persistent AF; P = 0.026). At the onset of AF, the earliest generators of fibrillatory activity were located more frequently in the posterior wall of the LA. Conclusion: AF in the LA displays substantial regional differences in terms of AF cycle lengths and degree of organization. Patients with persistent AF have shorter cycle lengths and a higher degree of disorganized activity than patients with paroxysmal AF. Intermediary rhythms play an important role in initiation of AF via activation of generator regions in the LA.
How to Diagnose, Locate, and Ablate Coronary Cusp Ventricular Tachycardia
Authors: HACHIYA HITOSHI , AONUMA KAZUTAKA , YAMAUCHI YASUTERU , IGAWA MASAYUKI , NOGAMI AKIHIKO , IESAKA YOSHITO 
Published: August 2003

Catheter Ablation of LVOT VT from a Coronary Cusp.
Introduction: Although radiofrequency energy usually is applied to the most favorable endocardial site in patients with outflow tract ventricular tachycardia, there are still some patients in whom the tachycardia can be ablated only from an epicardial site. We established the characteristics and technique of catheter ablation from both the left and right coronary cusps to cure left ventricular outflow tract ventricular tachycardia. Methods and Results: We studied 15 patients in whom VT was thought to originate from the coronary cusp by both activation and pace mapping after precise mapping of the right ventricle, left ventricle, pulmonary artery, coronary cusps, and anterior interventricular vein. Twelve‐lead ECG analysis revealed an S wave on lead I, tall R wave on leads II, III, and aVF, and no S wave on either lead V5 or V6. Precordial R wave transition occurred on leads V1 and V2. The earliest ventricular electrogram at a successful ablation site was recorded 35 ± 12 msec before QRS onset and 19 ± 15 msec earlier than the earliest ventricular electrogram recorded from the anterior interventricular vein. Almost identical pace mappings were obtained from the coronary cusp. Catheter tip temperature was maintained at 55°C during energy delivery, and the distance from the tip to the ostium of each left and right coronary artery was > 1.0 cm by coronary angiography. Conclusion: Left ventricular outflow tract VT that could not be ablated from an endocardial site could be safely eliminated by radiofrequency application to the left and right coronary cusps.