bluuebunny/crossref_metadata_2025_split huggingface dataset:
Intracardiac Stimulation of Human Parasympathetic Nerve Fibers Induces Negative Dromotropic Effects:
Authors: CHEN SHIH‐ANN , CHIANG CHERN‐EN , TAI TAI CHING , WEN ZU‐CHI , LEE SHIH‐HUANG , CHIOU CHUEN‐WANG , ANN DING YU , CHANG SONG 
Published: April 2007

Intracardiac Stimulation and Dromotropic Effect. Introduction: The dromotropic effects of intracardiac parasympathetic nerve stimulation have not been well studied; furthermore, the effects of radiofrequency ablation lesions on parasympathetic nerve stimulation are not clear. Methods and Results: Group I: intracardiac electrical stimulation in the right posteroseptal and anteroseptal areas under different stimulation strengths; group II: intracardiac electrical stimulation before and 10 minutes after intravenous propranolol; group III; intracardiac electrical stimulation before and 5 minutes after intravenous atropine. Among the 10 patients with AV nodal reentrant tachycardia (group IV) and the 10 patients with atrial flutter (group V), atrial fibrillation was induced before and after successful ablation, and intracardiac electrical stimulation in the right posteroseptal area was performed before and after successful ablation. The maximal response and complete decay of the response occurred within 2 to 6 seconds of initiation or termination of parasympathetic nerve stimulation. This negative dromotropic effect disappeared after atropine was administered, but not after propranolol. After successful ablation, parasympathetic stimulation still induced negative dromotropic effects. Conclusion: Electrical stimulation of parasympathetic nerve fibers near the posteroseptal and anteroseptal areas could induce a negative dromotropic effect, and this effect was preserved after successful radiofrequency ablation of slow pathway and isthmus conduction.
Changes in Cardiac Repolarization Following Short Periods of Ventricular Pacing
Authors: GOYAL RAJIVA , SYED ZAFFER A. , MUKHOPADHYAY PARTHA S. , SOUZA JOSEPH , ZIVIN ADAM , KNIGHT BRADLEY P , MAN K. CHING , STRICKBERGER S. ADAM , MORADY FRED 
Published: April 2007

Cardiac Memory. Introduction: “Cardiac memory” (primary T wave change) is thought to occur after 15 minutes to several hours of right ventricular (RV) pacing. The two components of the temporal change in repolarization are memory and accumulation. The purpose of this study was to examine quantitatively the effect of short periods of ventricular pacing on the human cardiac action potential, using monophasic action potential (MAP) recordings. Methods and Results: Thirty‐one patients (ages 43 ± 14 years) with structurally normal hearts undergoing a clinically indicated electrophysiologic procedure were enrolled. Catheters were placed in the right atrium (RA) and RV, and a MAP catheter was positioned at the RV septum. APD90 was calculated from digitized MAP recordings. MAP morphology comparisons were performed using the root mean square (RMS) of the difference between complexes. All pacing was at 500‐msec cycle length. There were four pacing protocols: (1) RA pacing was performed for approximately 15 minutes to evaluate temporal stability of the MAP recordings (5 pts); (2) to evaluate the memory phenomenon, four successive 1‐minute episodes of RV pacing were interspersed with 2 minutes of RA pacing (5 pts); (3) the accumulation phenomenon was evaluated by assessing the effects of 1, 5, 10, and 15 minutes of RV pacing on the MAP during RA pacing (16 pts); and (4) 20 minutes of RV pacing was followed by 10 minutes of RA pacing to correlate visually apparent T wave changes with changes in MAP recordings (5 pts). In the control patients, no changes in APD90 or RMS analysis were noted during 14.9 ± 1.4 minutes of RA pacing. In the second protocol, RMS of the difference between the baseline MAP complexes and the signal average of the first 50 beats following each of four 1‐minute RV pacing trains demonstrated progressively greater differences in morphology after successive episodes of RV pacing. In protocol 3, RMS analysis identified a progressively greater difference between the baseline MAP recording and the average of the first 50 beats after 1,5, 10, and 15 minutes of RV pacing. In protocol 4, visually apparent changes in T waves occurred in parallel with the RMS of the difference between the baseline MAP recordings and the average of the first 50 beats after 20 minutes of RV pacing. Similar changes also were demonstrated by APD90 analysis. Conclusion: This study is the first to demonstrate that episodes of abnormal ventricular activation as short as 1 minute in duration may exert lingering effects on the repolarization process once normal ventricular activation resumes.
Differential Role of Epicardial and Endocardial KATP Channels in Potassium Accumulation During Regional Ischemia Induced by Embolization of a Coronary Artery with Latex
Authors: MIYOSHI SHUNICHIRO , MIYAZAKT TOSHTHISA , ASANAGI MIKA , MORITANI KAZUNORI , OGAWA SATOSHI 
Published: April 2007

Epicardial and and Endocardial [K+]0 Rise and KATP Channels. Introduction: KATP channels are activated predominantly in the epicardium during regional ischemia. Therefore, the role of KATP channels in ischemia‐induced rise of extracellular potassium concentration ([K+]o) might he greater in the epicardium. Methods and Results: In 18 anesthetized dogs, the left anterior descending coronary artery (LAD) was ligated, followed by injection of 23‐μm latex heads into the occluded artery to interrupt collateral flow, by which accumulated [K+]o might wash out. Epicardial and endocardial [K+]o were measured during a 20‐minute period of ischemia using a valinomycin membrane. The dogs were divided into three groups: 6 control dogs (CTRL); 7 dogs pretreated with intravenous glibenclamide (0.3 mg/kg [GLIB]), a blocker of KATP channels: and 5 dogs pretreated with intravenous nicorandil (0.2 to 0.25 mg/kg [NCR]), a KATP channel opener. Before LAD occlusion, there was no difference in [K+]o among the three groups. In the control group, epicardial and endocardial [K+]o were increased to a similar level as a function of time after occlusion (CTRL) at both layers. Ischemia‐induced epicardial [K+]o rise was suppressed by GLIB (8.4 ± 0.4 vs 6.7 ± 0.5 mM, P < 0.05) but augmented by NCR (12.9 ± 2.0 mM, P < 0.05). In contrast, endocardial [K+]o, rise remained unaffected (7.6 ± 0.2 mM CTRL, 7.6 ± 1.3 mM GLIB, and 9.4 ± 2.2 mM NCR, P = NS). Conclusion: Activation of KATP channels plays an important role in epicardial [K+]o rise, but not in endocardial [K+]o rise, during regional ischemia. Another mechanism(s) may he important for endocardial [K+]o accumulation.
Effect of Shock Waveform on Relationship Between Upper Limit of Vulnerability and Defibrillation Threshold
Authors: SWERDLOW CHARLES D. , KASS ROBERT M. , O'CONNOR MARK E. , CHEN PEKG‐SHENG 
Published: April 2007

ULV‐DFT Waveform. Introduction: The upper limit of vulnerability (ULV) correlates with the defibrillation threshold (DFT). The ULV can he determined with a single episode of ventricular fibrillation and is more reproducible than the single‐point DFT. The critical‐point hypothesis of defibrillation predicts that the relation between the ULV and the DFT is independent of shock waveform. The principal goal of this study was to test this prediction. Methods and Results: We studied 45 patients at implants of pectoral cardioverter defibrillators. In the monophasic‐biphasic group (n = 15), DFT and ULV were determined for monophasic and biphasic pulses from a 120‐μF capacitor. In the 60‐ to 110‐μF group (n = 30), DFT and ULV were compared for a clinically used 110‐μF waveform and a novel 60‐μF waveform with 70% phase 1 tilt and 7‐msec phase 2 duration. In the monophasic‐biphasic group, all measures of ULV and DFT were greater for monophasic than biphasic waveforms (P < 0.0001). In the 60‐ to 110‐/tF group, the current and voltage at the ULV and DFT were higher for the 60‐μF waveform (P < 0.0001), hut stored energy was lower (ULV 17%, P < 0.0001; DFT 19%, P = 0.03). There was a close correlation between ULV and DFT for both the monophasic‐biphasic group (monophasic r2= 0.75, P < 0.001; hiphasic r2= 0.82, P < 0.001) and the 60‐ to 110‐μF group (60 μF r2= 0.81 P < 0.001; 110 μF r2= 0.75, P < 0.001). The ratio of ULV to DFT was not significantly different for monophasic versus biphasic pulses (1.17 ± 0.12 vs 1.14 ± 0.19, P = 0.19) or 60‐μF versus 110‐μF pulses (1.15 ± 0.16 vs 1.11 ± 0.14, P = 0.82). The slopes of the ULV versus DFT regression lines also were not significantly different (monophasic vs biphasic pulses, P = 0.46; 60‐μF vs UO‐μF pulses, P = 0.99). The sample sizes required to detect the observed differences between experimental conditions (P < 0.05) were 4 for ULV versus 6 for DFT in the monophasic‐biphasic group (95% power) and 11 for ULV versus 31 for DFT in the 60‐ to 110‐μF group (75% power). Conclusion: The relation between ULV and DFT is independent of shock waveform. Fewer patients are required to detect a moderate difference in efficacy of defibrillation waveforms by ULV than by DFT. A small‐capacitor biphasic waveform with a long second phase defibrillates with lower stored energy than a clinically used waveform.
Effect of Shock Polarity on Biphasic Defibrillation Thresholds Using an Active Pectoral Lead System
Authors: OLSOVSKY MARY R. , SHOROFSKY STEPHEN R. , GOLD MICHAEL R. 
Published: April 2007

Polarity and Biphasic Defibrillation Thresholds. Introduction: The downsizing of implantable defibrillator pulse generators has made pectoral placement routine. A further reduction of defibrillation thresholds (DFTs) may simplify implantation defibrillation testing and allow for smaller, lower output pulse generators while maintaining an adequate defibrillation safety margin. One factor that may affect defibrillation efficacy is shock polarity. Methods and Results: Sixty consecutive patients undergoing dual‐coil, active left pectoral defibrillator implantation were evaluated. Paired, biphasic DFTs were measured in normal (RV apex = cathode) and reverse (RV apex = anode) polarity with order of testing randomized. Reverse polarity conferred a 15% reduction of mean DFTs (8.5 ± 5.0 J normal. 7.2 ± 4.6 J reverse polarity. P = 0.02). The effect of polarity appeared most pronounced among the patients with a high DFT (> 15 J) resulting in a 31% reduction with reverse polarity (16.7 ± 2.5 J normal, 11.5 ± 5.9 J reverse, P = 0.03). Conclusion: Reversing shock polarity results in significantly lower biphasic DFTs with an active pectoral lead system, particularly in the subgroup of patients with a high normal polarity threshold. Reversing polarity in these patients may simplify acute defibrillation testing and allow for lower output devices.
Focal Atrial Tachycardia:
Authors: CHEN SHIH‐ANN , TAI CHING‐TAI , CHIANG CHERN‐EN , DING YU‐AN , CHANG MAU SONG 
Published: April 2007

Atrial Tachycardia. Introduction: Reports about the clinical and electrophysiologic characteristics of focal atrial tachycardia vary widely. Furthermore, the impact of age, gender, associated cardiac diseases, mechanism, location of atrial tachycardia, and the prediction of results of radiofrequency catheter ablation was not clear. The purpose of this study was to further understand the clinical and electrophysiologic characteristics of focal atrial tachycardia and the prediction of results of radiofrequency ablation. Methods and Results: We searched the literature published between January 1969 and July 1997 using the key word “atrial tachycardia” from the MEDLINE and National Library of Medicine systems. The items analyzed were age, sex, cardiac disease, mechanism, attack pattern, cycle length, location, number of atrial tachycardias, results of ablation, and recurrence after ablation. Multivariate analysis showed that age and paroxysmal type of tachycardia were independent predictors of nonautomatic mechanism; age and presence of other cardiac diseases were independent predictors of multiple atrial tachycardias, and age also was the independent predictor of right‐sided atrial tachycardia. Atrial tachycardia located in the right atrium was the only significant predictor of successful radiofrequency catheter ablation. Other cardiac diseases and multiple atrial tachycardias were the significant predictors of recurrence after initial successful radiofrequency catheter ablation. Conclusion: Patient age is closely related to the clinical and electrophysiologic characteristics of atrial tachycardia based on our reanalysis, which found that patient age is an independent predictor of nonautomatic mechanism, right atrial location, existence of multiple atrial tachycardias, and recurrence of atrial tachycardia after initial successful ablation.
Evidence for Multiple Atrio‐AV Nodal Inputs in the Normal Dog Heart
Authors: ANTZ MATTHIAS , SCHERLAG BENJAMIN J. , OTOMO KENICHIRO , PITHA JAN , TONDO CLAUDIO , PATTERSON EUGENE , JACKMAN WARREN M. , LAZZARA RALPH 
Published: April 2007

Multiple Atrio‐AVN Inputs in Dog Heart. Introduction: Complete AV block after combined fast pathway (FP) and slow pathway (SP) ablation is uncommon. The purpose of this study was to interrupt activation of these and additional inputs by placing a radiofrequency lesion across the interatrial septum between the FP and SP ablation sites. Methods and Results: In eight anesthetized open chest dogs, FP ablation induced significant A‐H prolongation (δA‐H: 51±14 msec; P < 0.001) and a shift of earliest retrograde atrial activation from the anterior septum to the region of the coronary sinus (CS) os. Subsequently, ablation of the interatrial septum across the fossa ovalis was successful in 5 of 8 dogs, changing the sequence of atrial activation (A) so that A at the His‐bundle electrogram, which initially preceded A at the CS os (18 ± 4 msec vs 46 ± 7 msec, P < 0.01), now followed CS os A (81 ± 31 msec vs 59 ± 20 msec, P < 0.05). Additional ablation of the SP caused a type II Mobitz AV block or complete AV block in 5 of 8 dogs. The four dogs with complete AV block sbowed a stable, high junctional escape rhytbm at a rate of 64 ± 16 beats/min. Pacing between the ablation lesions and the AV node in one dog showed 1:1 AV conduction and Wenckebach‐type AV block indicating preserved AV nodal function. Histology showed necrotic changes in the FP and SP transitional cell zones and in the atrial tissue of the interatrial septum. However, the compact AV node. His bundle, and adjacent atria and transitional cells were undamaged. Conclusion: There are additional AV nodal inputs in the interatrial septum in addition to the anterior FP and posterior SP inputs. Ablation of all of these may be required, if the aim is production of complete AV block proximal to the AV node with a high Junctional escape rhythm.
Recurrent Supine Syncope:
Authors: ISKOS DEMOSTHENES , SHULTZ JEFFREY J. , BENDITT DAVID G. 
Published: April 2007

Supine Syncope. Introduction: Syncope occasionally may occur in the supine patient due to severe brady‐ or tachyarrhythmia. However, recurrent syncope upon assumption of the supine position as a result of a neurally mediated reflex mechanism has not been reported previously. Methods and Results: Two young patients, both of whom had significant systemic illnesses, experienced recurrent episodes of presyncope and/or syncope shortly after assuming the supine position. During ambulatory ECG monitoring, symptoms were provoked only by lying down and were associated with transient bradycardia. Head‐up tilt table testing was undertaken as part of the syncope evaluation and was nondiagnostic in both cases. However, both patients exhibited a transient cardioinhibitory response with reproduction of typical symptoms upon return of the table to the supine position (“reverse tilt”). During follow‐up (8 and 14 months), both patients improved with pharmacologic treatment (disopyramide in one case and midodrine in the other). Conclusion: Presyncope or syncope upon lying down can he an unusual manifestation of the neurally mediated faint.
Effect of Electrode Length on Atrial Defibrillation Thresholds
Authors: TIMMERMANS CARL , RODRIGUEZ LUZ‐MARIA , AYERS GREGORY M. , LAMBERT HENDRIK , SMEETS JOEP , WELLENS HEIN J.J. 
Published: April 2007

Electrode Length for Atrial Defibrillation. Introduction: Catheter‐based electrodes have been used previously to terminate episodes of atrial fibrillation in animals and man. Typically, these electrodes span 6 to 7 cm, and lowest energy requirements are achieved when these electrodes are positioned in the distal coronary sinus and in the right atrium. The purpose of this study was to evaluate the use of longer electrode lengths for atrial defibrillation. Methods and Results: In 15 patients, two decapolar catheters were inserted, one into the distal coronary sinus and one in the right atrium. To provide longer electrodes lengths, a third catheter was inserted and alternated positioned in the right atrium or coronary sinus. A 6‐cm electrode span was obtained by using the distal 8 rings on the coronary sinus catheter or 8 consecutive electrodes on the right atrial catheter and increased from 6 to 11 cm by connecting consecutive, nonoverlapping rings of the third catheter with the 10 rings of the initial right atrial or coronary sinus catheter. Atrial defibrillation thresholds were determined twice, in a randomized order, in each patient for each of the three combinations of electrode lengths. All 15 patients could he successfully converted to sinus rhythm without complications; however, one patient could be converted reproducibly with only 2 of the 3 electrode combinations. Mean thresholds were 306 ± 102 V, 5.9 ± 4.0 J for the 6 cm/6 cm electrode length combination with an impedance of 72 ± 18 ω. For the electrode combination using the 11‐cm electrode in the right atrium, the defibrillation threshold was 296 ± 107 V, 5.8 ± 3.9 J with an impedance of 61 ± 17 ω and was 294 ± 91 V, 5.6 ± 3.6 J with an impedance of 55 ± 11 ω for the 11‐cm electrode in the coronary sinus. There were no significant differences in defibrillation voltage or energy (P > 0.05) associated with the longer electrode lengths; however, the longer electrode lengths did significantly lower shock impedance (P < 0.05). Conclusion: The use of longer electrodes, when using the right atrium to coronary sinus shock vector, does not lower the defibrillation requirements for restoration of sinus rhythm.
Immediate Reproducibility of Upper Limit of Vulnerability Measurements in Patients Undergoing Transvenous Implantable Cardioverter Defibrillator Implantation
Authors: ELLENBOGEN KENNETH A. , WOOD MARK A. , GILLIGAN DAVID M. , CROFTS THERESA , LONDON WENDY , McCLISH DONNA 
Published: April 2007

Reproducibility of ULV. Introduction: Measurement of the upper limit of vulnerability (ULV) with monophasic T wave shocks has been proposed as a patient‐specific measurement of defibrillation efficacy that results in fewer episodes of ventricular fibrillation (VF) than measurement of a defibrillation efficacy curve. Methods and Results: We sought to determine the magnitude of variance in ULV in 63 consecutive patients undergoing implantation of an implantable cardioverter defibrillator (ICD). We measured ULV as the strength at or above which VF is not induced when a stimulus is delivered at 310 msec after an 8‐beat ventricular pacing drive at 400 msec. Defibrillation threshold (DFT) was measured in patients with an active can device using a biphasic waveform and the binary search method beginning at 12 J. Sixty‐three patients were studied; they bad a mean age of 62 × 12 years and a mean ejection fraction of 35%± 15%. Three quarters of patients bad an ischemic cardiomyopathy. Each patient underwent 4.5 ± 0.8 measurements f ULV. Monophasic ULV correlated poorly with biphasic DFT (R between 0.19 and 0.28, P = 0.04 to 0.17). There was no change in ULV between second to third, third to fourth, and first to last measurement in 22% to 41% of patients. The reliability coefficient was 0.87. A ULV ≥ 20 J was found in eight patients. The only predictor of high ULV was a high DFT. Conclusion: Monophasic ULVs do not closely predict biphasic active can DFTs using a standard protocol. High DFTs were predicted by high ULVs. There was little variation in the acute measurement of ULV between trials. These findings have important implications for using ULV measurements to determine changes in DFTs after interventions. The methodology of determining ULV is critical to its use for predicting DFTs and programming ICDs.
Altered Pattern of Connexin40 Distribution in Persistent Atrial Fibrillation in the Goat
Authors: van der VELDEN HUUB M.W. , van KEMPEN MARJAN J.A. , WIJEFELS MAURITS C.E.E , van ZIJVERDEN MAAIKE , GROENEWEGEN W. ANTOINETTE , ALLESSIE MAURITS A. , JONGSMA HABO J. 
Published: April 2007

Cx40 Distribution in Goat Atrial Fibrillation. Introduction: Since altered expression of gap junction proteins (connexins) in diseased myocardial tissue may lead to abnormal electrical coupling between cardiomyocytes and hence contribute to arrhythmogenesis, the expression of connexin(Cx)40 and Cx43 was studied in atrial appendage from goats in sinus rhythm (SR) and persistent atrial fibrillation (AF). Methods and Results: Biopsies were taken from the left and right atrial appendages from goats in SR or after pacing‐induced persistent AF. Analyses of Cx40 and Cx43 mRNA and protein levels, using quantitative (competitive) polymerase chain reaction and western blotting, respectively, revealed no significant changes in the overall expression of Cx40 and Cx43 as a result of persistent AF. At the cellular level, immunohistochemistry and confocal laser canning microscopy showed a homogeneous distribution of either connexin in atrial sections taken during SR. After induction of AF, the distribution of Cx43 gap Junctions was unchanged whereas the Cx40 pattern showed marked inhomogeneities with small areas (0.15 to 0.6 mm in diameter, 25% of section surface area) of low‐density Cx40 located between larger areas of normal (unchanged) Cx40 density. Activation mapping (244 electrodes, spatial resolution 2.25 mm) of the right atrial wall did not reveal changes in atrial conduction velocity. Conclusion: Pacing‐induced persistent AF in the goat gave rise to changes in the spatial organization of Cx40 gap junctions. Although the overall conduction velocity appeared not to have changed, microheterogeneities in conduction due to the local redistribution of Cx40 gap junctions might have contributed to the initiation and maintenance of AF.
Nonfluoroscopic Transseptal Catheterization:
Authors: EPSTEIN LAURENCE M. , SMITH TIMIOTHY , HOFF HARM Ten 
Published: April 2007

ICE‐Guided Transseptal Catheterization. Introduction: Recently, there has been a revival in the use of transseptal catheterization due to the development of balloon mitral valvuloplasty and radiofrequency catheter ablation. Complications of transseptal puncture, although rare, can be serious and life‐threatening. In the present study, we evaluated the use of intracardiac echocardiography (ICE) as the sole imaging modality to guide transseptal puncture and catheterization. Methods and Results: In each animal. 10 transseptal punctures were performed guided solely by ICE. The standard approach to transseptal catheterization using a Brockenbrough needle and long vascular sheath was used except for the use of ICE instead of fluoroscopy. A 6.2‐French/12.5‐MHz and 9‐Frencb/9‐MH7, ICE catheter was used for imaging. At the end of each study, pathologic evaluation was performed. Transseptal puncture was performed safely, guided solely by ICE, in each of 100 attempts (five attempts guided by each ICE catheter in 10 dogs). While the fossa ovalis was easily visualized with both ICE catheters, the 9‐Frcnch/9‐MHz catheter offered an enhanced field of view. On pathologic evaluation, there was no evidence of perforation of either the right or left atrium outside of the fossa ovalis. Conclusion: Both ICE catheters used in this trial allowed for excellent visualization of the fossa ovalis and safe transseptal puncture. Intracardiac echocardiography may be a better imaging modality than fluoroscopy for guiding transseptal atheterization, especially in less experienced hands.