bluuebunny/crossref_metadata_2025_split huggingface dataset:
Measurement of Funny Current (If) Channel mRNA in Human Atrial Tissue: Correlation with Left Atrial Filling Pressure and Atrial Fibrillation
Authors: LAI LING‐PING , SU MING‐JAI , LIN JIUNN‐LEE , TSAI CHANG‐HER , LIN FANG‐YUE , CHEN YIH‐SHARNG , HWANG JUEY‐JEN , HUANG SHOEI K. STEPHEN , TSENG YUNG‐ZU , LIEN WEN‐PIN 
Published: April 2007

If in Human Atrial Tissue. Introduction: The funny current (If) contributes to phase IV spontaneous depolarization in cardiac pacemaker tissue. Enhanced If activity in myocardial tissue may lead to increased automatically and therefore tachyarrhythmia. We measured the amount of If, activity in the messenger ribonucleic acid (mRNA) in human atrial tissue and correlated the mRNA amount to left atrial filling pressure and atrial fibrillation (AF). Methods and Results: A total of 34 patients undergoing open heart surgery were included (15 men and 19 women, aged 55 ± 10 years). Atrial tissue was obtained from the right atrial free wall, the right atrial appendage, the left atrial free wall, and the left atrial appendage, respectively. The mRNA amount of the If channel was measured by reverse transcription polymerase chain reaction and was normalized to the mRNA levels of glyceraldehyde 3‐phosphate dehydrogenase. We found that the If channel mRNA was present at all the atrial sampling sites. A higher left atrial filling pressure, an indicator of congestive heart failure, was associated with a higher If mRNA level (r2= 0.446, P < 0.01 by linear regression). We also found that the mRNA amount was significantly higher in patients with AF than in patients without AF (1.68 ± 0.49 vs 1.27 ± 0.43; P < 0.05). Age, sex, right atrial filling pressure, left atrial dimension, and left ventricular ejection fraction had no significant effect on the mRNA level. Conclusion: The nRNA of the If, channel is present in the free‐wall area and appendage area from both atria. Increased left atrial filling pressure and clinical AF are associated with increased If mRNA level.
Characteristics, Circuit, Mechanism, and Ablation of Reentry in the Rabbit Atrioventricular Node
Authors: LIN LI‐JEN , BILLETTE JACQUES , KHALIFE KARIM , MARTEL KARYNE , WANG JUN , MEDKOUR DJAMILA 
Published: April 2007

Functional Origin of AV Nodal Reentry. Introduction: The circuitry underlying AV nodal reentry remains debated. We developed a model of AV nodal reentry and assessed the role of nodal inputs, compact node, and its posterior nodal extension (PNE) in this phenomenon. Methods and Results: A fine scanning of short coupling interval range with an atrial premature heat consistently initiated slow‐fast AV nodal reentrant heats that occurred 37 ± 31 msec (mean ± SD) after His‐bundle activation in 11 of 16 consecutive rabbit heart preparations. The repeated testing (>40 times) of a chosen coupling interval within reentry window (6 ± 9 msec, n = 11) yielded reentrant intervals that varied by 2 ± 1 msec (mean SD for 40 heats ± SD, n = 11). The breakthrough point of reentrant activation, as assessed from four perinodal sites, varied in different preparations from diffuse (4) to anterior (1), medial (3), or posterior (3); mean reentrant interval did not differ between perinodal sites. Antegrade perinodal activation pattern did not differ at reentrant versus nonreentrant coupling intervals and thus was not a primary determinant of reentry. A PNE ablation (n = 4) interrupted the slow pathway conduction and prevented reentry without affecting antegrade perinodal activation or fast pathway conduction. Conclusion: A reproducible model of AV nodal reentrant beats was developed and used to study underlying circuitry. The AV nodal reentry involves unaltered antegrade perinodal activation, slow PNE conduction and retrograde broad invasion of perinodal tissues starting at a preparation‐dependent breakthrough point. A PNE ablation abolishes the reentry.
Effects of Spatial Segmentation in the Continuous Model of Excitation Propagation in Cardiac Muscle
Authors: WU JIASHIN , ZIPES DOUGLAS P. 
Published: April 2007

Spatial Segmentation in the Simulation of Propagation. Introduction: Spatial segmentation is essential for the numerical simulation of excitation propagation in cardiac muscle. Methods and Results: This study evaluated the effects of spatial segmentation on action potential and on the velocity of propagation in a continuous one‐dimensional model of cardiac muscle [intracellular and extracellular resistivities along (L) and transverse (T) to the muscle fibers: 402 ωcm (Ri, L), 3,620 ωcm (Ri, T), 48 ωcm (Re, L), and 126 ωcm (Re, T), J of Physiol 255:335‐346, 1976) and either Luo‐Rudy (L‐R, Circ Res 68:1501‐1526, 1991) or Beeler‐Reuter (B‐R, J Physiol 268:177‐210, 1977) ionic currents. Related cable equations for active membrane are derived. Spatial segmentations of < 31.2 μm (L, L‐R), < 11.5 μm (T, L‐R), < 44.7 μm (L, B‐R), and < 16.5 μm (T, B‐R) were required for < 1% errors in the characteristic parameters of action potential. Similarly, spatial segmentations of < 54.5 μm (L, L‐R), < 20.1 μm (T, L‐R), < 84.3 μm (L, B‐R), and < 31.2 μm (T, B‐R) were required for < 1% errors in the velocity of conduction. Conclusion: In general, spatial segmentations of < 26.9% and < 50.8% of the space constant of a fully activated membrane gave < 1.0% errors in the characteristic parameters of action potential and in the velocity of propagation, respectively, for both membranes. The action potential duration was relatively insensitive to the spatial segmentation. Our analysis suggests that λfull is a better criterion for the selection of spatial segmentation in numerical simulation than the space constant of the resting membrane.
Bimodal RR Interval Distribution in Chronic Atrial Fibrillation:
Authors: TEBBENJOHANNS JÜRGEN , SCHUMACHER BURGHARD , KORTE THOMAS , NIEHAUS MICHAEL , PFEIFFER DIETRICH 
Published: April 2007

Bimodal RR Interval Distribution, Introduction: Radiofrequency (RF) catheter modification of the AV node hi patients with atrial fibrillation (AF) is limited by an unpredictable decrease of the ventricular rate and a wish incidence of permanent AV block, A bimodal RR histogram has been suggested to serve as a predictor for successful outcome but the corresponding AV node properties have never been characterized, We hypothesized that a bimodal histogram indicates dual AV nodal physiology and predicts a better outcome after AV node modification in chronic AF. Methods and Results: Thirty‐seven patients were prospectively subdivided into two groups according to the RR histogram of 24‐hour ECC monitoring, Before to RF ablation, internal cardioversion and programmed stimulation were performed, Among the 22 patients (group I) with a bimodal RR histogram, dual AV nodal physiology was found in 17 (779f) patients, Ablation significantly decreased ventricular rate with loss of the peak of short RR cycles after ablation (mean and maximal ventricular rates: 32% and 35% rate reduction, respectively; P < 0,01), In 15 patients with a unimodal RR histogram (group II), dual AV nodal physiology was found in 2 (13%), and rate reductions were 16% and 17%, respectively, At 6 months, 3 (14%) patients in group 1 and 6 (40%) in group II underwent elective AV nodal ablation with pacemaker implantation due to intolerable rapid ventricular response to AF. Conclusion: Bimodal RR interval distribution during chronic AF suggests the presence of dual AV nodal physiology and predicts a better outcome of RF ablation of the posterior atrionocdal input.
Cycle Length Dynamics at the Onset of Postinfarction Ventricular Tachycardias Induced in Canines:
Authors: HÉLIE V FRANÇOIS , VINET ALAIN , CARDINAL RENÉ 
Published: April 2007

Tachycardia Onset Dynamics. Introduction: Postinfarction monomorphic ventricular tachycardius induced by programmed stimulation may display initial cycle length (CL) variations before stabilizing. Methods and Results: To show that tachycardia onset dynamics depend on rate‐dependent electrical properties of the reentrant substrate, we extracted activation times and maximum negative slopes of local activation complexes (‐dV/dtmax) from 191 unipolar electrograms recorded in the anterior left ventricular wall of anesthetized, 3‐day‐old infarct canine preparations. Measurements were made of the responses to programmed stimulation, as well as in early and later beats of tachycardias, which displayed either a constant trend in CL (group A, n = 5 preparations) or one in which CL prolongation occurred according to an exponential course before stabilizing (group B, n = 9). Stimulation protocols inducing the tachycardias were more aggressive and their CL was significantly shorter (CL = 159 ± 24 msec) in group A than in group B (stabilized CL = 206 ± 34 msec). Reentrant activity occurred in subepicardial areas in which the absolute value of ‐dV/dtmax (|‐dV/dtmax|) was heterogeneously depressed (<2 mV/msec). |‐dV/dtmax| was reduced and activation delay increased in the successive responses to extrastimuli. Further reductions in |‐dV/dtmax| (10% to 23%) were shown to occur between early and later beats in 5 of the 9 tachycardias in group B (no change in the 4 others), and they were associated with localized prolongation of conduction times in reentrant pathways. In contrast, |‐dV/dtmax| improved in all group A tachycardias (7% to 25%). Conclusion: This study provides evidence that the onset dynamics of postinfarction ventricular tachycardias are determined by interval‐dependent electrical changes occurring in the reentrant substrate.
Simultaneous Optical Mapping of Transmembrane Potential and Intracellular Calcium in Myocyte Cultures
Authors: FAST VLADIMIR G. , IDEKER RAYMOND E. 
Published: April 2007

Simultaneous Mapping of Vm and Cai2+. Introduction: Fast spatially resolved measurements of transmembrane potential (Vm) and intracellular calcium (Cai2+) are important for studying mechanisms of arrhythmias and defibrillation. The goals of this work were (1) to develop an optical technique for simultaneous multisite optical recordings of Vm and Cai2+, and (2) to determine the relationship between Vm and Cai2+ during normal impulse propagation in myocyte cultures. Methods and Results: Monolayers of neonatal rat myocytes were stained with fluorescent dye RH‐237 (Vm) and Fluo‐3AM (Cai2+). Both dyes were excited at the same wavelength range. The emitted fluorescent was optically separated into components corresponding to changes in Vm, and Cai2+ and measured using two 16 × 16 photodiode arrays at a spatial resolution of up to 27.5 μm per diode and sampling rate of 2.5 kHz. The optical setup was adjusted so that there was no optical cross‐talk between the two types of measurements, which was validated in experiments involving staining with either RH‐237 or Fluo‐3. The amplitude of Fluo‐3 signals rapidly decreased during experiments due to dye leakage. Dye leakage was substantially reduced by application of 1 mM probenecid, a blocker of organic anion transport, which had no effect on action potential duration and only minor effect on conduction velocity. In double‐stained preparations, during regular pacing Cai2+ transients had a rise time of 14.2 ± 2 msec, and they followed Vm upstrokes with a delay of 5.3 ± 1 msec (n = 9). Durations of Vm, and Cai2+ transients determined at 50% level of signal recovery were 54.6 ± 10 msec and 136 ± 8 msec, respectively. Application of 2 μM nifedipine reduced the amplitude and duration of Cai2+ transients without significantly affecting conduction velocity. Conclusion: The results demonstrate feasibility of simultaneous optical recordings of Vm and Cai2+ transients with high spatial and temporal resolution.
Effects of Intracardiac Radiofrequency Current Application on Coronary Artery Vessels in Young Pigs
Authors: BÖKENKAMP REGINA , WIBBELT GUDRUN , STURM MATTHIAS , WINDHAGEN‐MAHNERT BRITTA , BERTRAM HARALD , HAUSDORF GERD , PAUL THOMAS 
Published: April 2007

Radiofrequency Current Lesions in Young Pigs. Introduction: Radiofrequency current is widely used in children to ablate accessory AV pathways. Previous data in a pig model demonstrated coronary artery obstruction adjacent to radiofrequency current lesions 48 hours and 6 months after energy delivery. In the present study, the long‐term effects (>6 months) of radiofrequency current application on coronary artery vessels in young pigs are assessed. Methods and Results: Radiofrequency current (500 kHz) was delivered over 30 seconds in ten piglets (mean body weight 12.8 kg) using a steerahle 6‐French catheter with a 4‐mm thermistor tip electrode (target temperature 75°C), Lesions were created under fluoroscopic and electrocardiographic guidance at the lateral right atrial (RA) wall above the tricuspid valve orifice, and at the lateral left atrial and left ventricular wall adjacent to the mitral valve orifice. Selective coronary angiography and intravascular ultrasound (IVUS) studies were performed 3, 6, 9, and 12 months after energy application. After 12 months, the lesions were studied pathohistologically. All lesions consisted of compact fibrous tissue, RA lesions extended to the adjacent right coronary artery and led to coronary artery involvement with increased fibrous tissue in the adventitia and media and intimal thickening in three animals. Coronary arterial narrowing was documented by IVUS during follow‐up in all three cases 9 months after energy application. Angiography failed to demonstrate coronary pathology in any of the three animals. Conclusion: The risk of late coronary artery lesions must be considered when catheter ablation at the RA wail is planned in children with free‐wall accessory AV pathways.
Regional Hyperkalemia Increases Ventricular Defibrillation Energy Requirements:
Authors: SIMS J. JASON , MILLER ALLISON W. , UJHELYI MICHAEL R. 
Published: April 2007

Regional Hyperkalemia and Defibrillation. Introduction: Increased spatial electrical heterogeneity has heen associated with impaired defibrillation efficacy. The current study investigated the relationship between electrical heterogeneity and defibrillation efficacy by manipulating spatial electrical heterogeneity. Methods and Results: We increased spatial electrical heterogeneity by infusing potassium chloride (2 to 4 mEq/hour) or placebo In the left anterior descending artery in 13 pentobarbital anesthetized swine. Electrophysiologic measurements at five myocardial sites and defibrillation energy requirement (DER) values were determined at baseline and during regional hyperkalemia (n = 7) or placebo (n = 6). Regional potassium infusion was titrated to a 20% reduction in action potential duration in the perfused region. Regional hyperkalemia increased biphasic DER values by 87% (P = 0.02), whereas infusion of placebo did not alter defibrillation efficacy. Regional hyperkalemia decreased myocardial repolarization and refractoriness in the perfused region by 21% (P < 0.001) and 18% (P = 0.01), respectively. However, regional hyperkalemia increased ventricular fibrillation cycle length (VFCL) by 39% (P = 0.008). Consequently, dispersions of repolarization, refractoriness, and VFCL were significantly increased by 169%, 92%, and 200%, respectively. Regional hyperkalemia also increased ventricular conduction time to the perfused region by 54% (P = 0.006), indicating conduction velocity dispersion, while not affecting local pacing threshold or local voltage gradient. Conclusion: Regional hyperkalemia increased DER values. Regional hyperkalemia likely impairs defibrillation by increasing myocardial electrical heterogeneity, which supports the theory that electrical heterogeneity promotes nonuniform propagation of early postshock activations, thereby inhibiting defibrillation.
Electrophysiologic Deterioration After One‐Minute Fibrillation Increases Relative Biphasic Defibrillation Efficacy
Authors: TOVAR OSCAR H. , JONES JANICE L. 
Published: April 2007

Biphasic Shocks and One‐Minute Fibrillation. Introduction: The probability of survival decreases to 70% after 2 minutes of ventricular fibriltation. Bipliasic shocks are more effective than monophasic shocks in terminating short‐duration (<30 sec) ventricular fibrillation. We tested the hypotheses that developing ischemia changes the electrophysiologic characteristics of fibrillation and that the relative efficacy of biphasic shocks increases as electrophysiologic characteristics deteriorate. Methods and Results: Monophasic (12 msec) and biphasic (6/6 msec) shocks (1 to 4 A) were tested in random order in isolated rabbit hearts after 1‐minute ischemic fibrillation. Monophasic action potentials showed only a sporadic occurrence of electrical diastole after 5 seconds of fibrillation (24% of action potentials in the right ventricle and 18% in the left ventricle). After 60 seconds of fibrillation, diastole (17.83 ± 1.14 msec in the right ventricle and 21.52 ± 1.16 msec in the left ventricle) appeared after almost every action potential (P < 0.0001 compared with 5 sec), despite a lack of change in fibrillation cycle length and dominant frequency. Monophasie I50 was 2.89 A, and biphasic I50 was 1.4 A (77% reduction in energy). Normalized curve width decreased 28%. Retrospective analysis showed that shocks delivered early in the fibrillation action potential bad a greater probability of succeeding (89%) than shocks delivered late (30%; P < 0.001). Conclusion: After l‐minute ischemic fibrillation, diastolic intervals occur during fibrillation. Therefore, defibrillation shocks have an approximately 29% probability of interacting with the fibrillation action potential during diastole. At this time, biphasic shocks produced a more deterministic defibrillation threshold and became even more efficacious (I50B/M = 0.48) than at short fibrillation durations (I50 B/M = 0.7).
Pulmonary Vein Stenosis Complicating Catheter Ablation of Focal Atrial Fibrillation
Authors: SCANAVACCA MAURICIO I. , KAJITA LUIZ J. , VIEIRA MARCELO , SOSA EDUARDO A. 
Published: April 2007

Pulmonary Vein Stenosis. Introduction: A recently described focal origin of atrial fibrillation, mainly inside pulmonary veins, is creating new perspectives for radiofrequency catheter ablation. However, pulmonary venous stenosis may occur with uncertain clinical consequences. This report describes a veno‐occlusive syndrome secondary to left pulmonary vein stenosis after radiofrequency catheter ablation. Methods and Results: A 36‐year‐old man who experienced daily episodes of atrial fibrillation that was refractory to antiarrhythmic medication, including amiodarone, was enrolled in our focal atrial fibrillation radiofrequency catheter ablation protocol. The left superior pulmonary vein was the earliest site mapped, and radiofrequency ablation was performed. Atrial fibrillation was interrupted and sinus rhythm restored after one radiofrequency pulse inside the left superior pulmonary vein. Atrial fibrillation recurred and a new procedure was performed in an attempt to isolate (26 radiofrequency pulses around the ostium) the left superior pulmonary vein. Ten days later, the patient developed chest pain and hemoptysis related to severe left superior and inferior pulmonary veins stenosis. Balloon angioplasty of both veins was followed by complete relief of symptoms after 2 months of recurrent pulmonary symptoms. The patient has been asymptomatic for 12 months, without antiarrhythmic drugs. Conclusion: Multiple radiofrequency pulses applied inside the pulmonary veins ostia can induce severe pulmonary venous stenosis and veno‐occlusive pulmonary syndrome.
Analysis of the Pattern of Initiation of Sustained Ventricular Arrhythmias in Patients with Implantable Defibrillators
Authors: TAYLOR ERIC , BERGER RONALD , HUMMEL JOHN D. , DINERMAN JAY L. , KENKNIGHT BRUCE , ARRIA AMELIA M. , TOMASELLI GORDON , CALKINS HUGH 
Published: April 2007

Initiation of Sustained Ventricular Arrhythmias. Introduction: The purpose of this study was to analyze the pattern of initiation of sustained ventricular arrhythmias in patients with varying types of underlying structural heart disease. Methods and Results: The study group consisted of 90 patients with an implantable cardioverter defibrillator. Cardiovascular diagnoses included coronary artery disease in 64 patients (71%). The patients were divided into four groups based on the type and severity of structural heart disease. Two hundred sixty episodes of sustained ventricular arrhythmias were analyzed. The mean coupling interval of the initiating heat of all ventricular arrhythmias was 523 ± 171 msec. The coupling interval of the initiating beat was longer in patients with impaired ventricular function, particularly those with nonischemic dilated cardiomyopathy. The prematurity index was similar regardless of the type of underlying structural heart disease. However, the prematurity index was shorter in patients with polymorphic ventricular tachycardia (VT) compared to those with monomorphic VT. A pause was observed more commonly before the onset of polymorphic VT/ventricular fibrillation than sustained monomorphic VT. Two hundred twenty‐two (85%) of the arrhythmia episodes were initiated by a late‐coupled premature beat, 33 (13%) were initiated by an early‐coupled premature beat, and 5 episodes (2%) were initiated with a short‐long‐short sequence. The patttern of initiation of the ventricular arrhythmias was similar in all patient groups and for both monomorphic and polymorphic tachycardias. Conclusion: These findings demonstrate that sustained ventricular arrhythmias typically are initiated by late‐coupled ventricular premature depolarizations, regardless of the type or severity of underlying structural heart disease or resultant arrhythmia.
Unusual Features of Intermediate Septal Bypass Tracts
Authors: COPPESS MARK A. , ALTEMOSE GREGORY T. , JAYACHANDRAN J. VIJAY , AL‐SHEIKH THABET , ZIPES DOUGLAS P. , MILLER JOHN M. 
Published: April 2007

Intermediate Septal Bypass Tracts. Introduction: Intermediate septal (TS) AV bypass tracts, located along the tricuspid annulus between the His bundle and coronary sinus os, lie in close proximity to the AV node. Surgical or catheter ablation of IS bypass tracts incurs increased risk for development of complete heart block. We report additional unusual features of some IS bypass tracts that distinguish them from typical bypass tracts in other anatomic regions. Methods and Results: We analyzed a consecutive series of 150 patients with a history of Wolff‐Parkinson‐White syndrome and supraventricular tachycardia who underwent ablation of bypass tracts. We studied the incidence and characteristics of AV conduction of IS bypass tracts compared with bypass tracts in other locations. Of the 150 patients in the study, 21 had an IS bypass tract (all had anterograde AV conduction). Ten (48%) of these 21 IS bypass tracts demonstrated anterograde decremental properties with atrial pacing versus 3 (2%) of 129 non‐IS bypass tracts (P < 0.001). During ablation, a change in delta wave morphology before total loss of conduction in the IS bypass tract also occurred in 3 (14%) of 21 IS bypass tracts versus 0 of 129 non‐IS bypass tracts (P = 0.0004). During ablation, a change in P wave to delta wave interval occurred in 4 (19%) of 21 IS bypass tracts versus 0 of 129 non‐IS bypass tracts (P < 0.0001). One IS patient exhibited retrograde Wenckebach block in the bypass tract, and two IS patients showed loss of retrograde bypass tract conduction after ablation attempts that first changed the delta wave morphology. No non‐IS patient had these features (P < 0.0001) for each comparison). Conclusion: Some IS bypass tracts have unusual properties that distinguish them from bypass tracts in other locations, perhaps due to the presence of multiple ventricular insertions of the bypass tract. It is possible that some cases represent true “nodoventricular” pathways.