bluuebunny/crossref_metadata_2025 huggingface dataset:
Electrophysiology of the Atrio‐AV Nodal Inputs and Exits in the Normal Dog Heart
Authors: HIRAO KENZO , SCHERLAG BENJAMIN J. , POTY HERVE , OTOMO KENICHIRO , TONDO CLAUDIO , ANTZ MATTHIAS , PATTERSON EUGENE , JACKMAN WARREN M. , LAZZARA RALPH
Published: April 2007

Ablation of Atrionodal Connections. Introduction: We studied the effects of selective and combined ablation of the fast (FP) and slow pathway (SP) on AV and VA conduction in the normal dog heart using a novel epicardial ablation technique.

Methods and Results: For FP ablation, radiofrequency current (RFC) was applied to a catheter tip that was held epicardially against the base of the right atrial wall. SP ablation was performed epicardially at the crux of the heart. Twenty‐three dogs were assigned to two ablation protocols: FP/SP ablation group (n = 17) and SP/FP ablation group (n = 6). In 12 of 17 dogs, FP ablation prolonged the PR interval (97 ± 10 to 149 ± 22 msec. P < 0.005) with no significant change in anterograde Wenckebach cycle length (WBCL), Subsequent SP ablation performed in 8 dogs further prolonged tbe PR interval and the anterograde WBCL (117 ± 22 to 193 ± 27, P < O.(M)5). Complete AV block was seen in I of 8 dogs, whereas complete or high‐grade VA block was seen in 6 of 8 dogs. In the SP/FP ablation group, SP ablation significantly increased WBCL with no PR changes. Combined SP/FP ablation in A dogs prolonged the PR interval significantly, but no instance of complete AV block was seen. VA block was found in 50% of these cases. Histologic studies revealed that RFC ablation affected the anterior and posterior atrium adjacent to the undamaged AV node and His bundle.

Conclusion: Using an epicardial approach, combined ablation of tbe FP and SP AV nodal inputs can be achieved with an unexpectedly low incidence of complete A V block, although retrograde VA conduction was significantly compromised.
Atrial Fibrillation
Authors: ZIPES DOUGLAS P.
Published: April 2007

Atrial Fibrillation: From Cell to Bedside. Atrial fibrillation is the most common sustained tachyarrhythmia and, as such, has become the recent focus of intense clinical and experimental interest. Because of its associated morbidity and mortality, there is a multidisciplinary effort to understand the pathophysiology that may ultimately lead to improved therapeutic options. This review concentrates on three aspects of atrial fibrillation that influence contemporary choices for treatment: an electrophysiologic basis for initiation of atrial fibrillation, anatomic and electrophysiologic remodeling, and concepts regarding its termination or prevention.
Structure of Connexin43 and its Regulation by pHi
Authors: MORLEY GREGORY E. , EK‐VITORÍN JOSÉ F , TAFFET STEVEN M. , DELMAR MARIO
Published: April 2007

pHi Regulation of Connexin43. Electrical coupling in the heart provides an effective mechanism fur propagating the cardiac action potential efficiently throughout the entire heart. Cells within the heart are electrically coupled through specialized membrane channels called gap junctions. Studies have shown that gap junctions are dynamic, carefully regulated channels that are important for normal cardiogenesis. We have recently been interested in the molecular mechanisms by which intracellular acidification leads to gap junction channel closure. Previous results in this lab have shown that truncation of the carboxyl terminal (CT) of connexin43 (Cx43) does not interfere with functional channel expression. Further, the pH‐dependent closure of C×43 channels is significantly impaired by removal of this region of the protein. Other studies have shown that the CT is capable of interacting with its receptor even when not covalently attached to the channel protein. From these data we have proposed a particle‐receptor model to explain the pH‐dependent closure of Cx43 gap junction channels. Detailed analysis of the CT has revealed interesting new information regarding its possible structure. Here we review the most recent studies that have contributed to our understanding of the molecular mechanisms of regulation of the cardiac gap protein C×43.
Indications for Radiofrequency Ablation in the Pediatric Population
Authors: VAN HARE GEORGE F.
Published: April 2007

Pediatric RF Ablation Procedures. Pediatric radiofrequency ablation procedures have become commonplace since their introduction to clinical practice 6 years ago. Excellent success rates coupled with low complication rates have allowed these procedures to be offered as firstline therapy to many children. This review focuses on the current indications for radiofrequency ablation in children. These indications are not the same as for adults. They are based on the natural history of various forms of arrhythmias, the risks of the procedure, and the current success rates of the procedures, all of which are dependent upon the age of the patient.
Book Review
Authors: REYNOLDS DWIGHT W.
Published: April 2007

Prevention of Tachyarrhythmias with Cardiac Pacing. Edited by J. Claude Daubert, Eric N. Prystowsky, and Alain Ripart.
Mode of Onset of Malignant Ventricular Arrhythmias in Idiopathic Ventricular Fibrillation
Authors: VISKIN SAMI , LESH MICHAEL D. , ELDAR MICHAEL , FISH ROMAN , SETBON ISRAEL , LANIADO SHLOMO , BELHASSEN BERNARD
Published: April 2007

Mode of Onset of Idiopathic VF. Introduction: The mode of onset of malignant ventricular arrhythmias (ventricular tachycardia [VT] or ventricular fibrillation [VF] has been well described in patients with organic heart disease and in patients with the long QT syndromes. Less is known about the mode of onset of VF in patients with out‐of‐hospital VF who have no evidence of organic heart disease or identifiable etiology.

Methods and Results: We reviewed the ECGs of all our patients with Idiopathic VF. Documentation of the onset of spontaneous arrhythmias was available for 22 VK episodes in 9 patients (6 men and 3 women; age 41 ± 16 years). In all instances, spontaneous VF followed a rapid polymorphic VT, which was initiated by premature ventricular complexes (PVCs) with very short coupling intervals. The PVC initiating VF had a coupling interval of 302 ± 52 msec and a prematurity index of 0.4 ± 0.07. These PVCs occurred within 40 msec of the peak of the preceding T wave. Pause‐dependent arrhythmias were never observed.

Concltision: Cardiac arrest among patients with idiopathic VF has a very distinctive mode of onset. Documentation of a polymorphic VT that is not pause dependent is of diagnostic value.
Use of Only a Regular Diagnostic His‐Bundle Catheter for Both Fast and Reproducible “Para‐Hisian Pacing” and Stable Right Ventricular Pacing
Authors: HEIDBÜCHEL HEIN , ECTOR HUGO , ADAMS JEF , VAN DE WERF FRANS
Published: April 2007

Pacing from the Diagnostic His‐Bundle Catheter. Introduction: Para‐Hisian pacing, i.e., pacing the anteroseptal right ventricle (RV) with or without direct capture of the His bundle (HB), allows the differentiation of VA conduction over the AV node from conduction over an accessory pathway. Classically, it is performed by maneuvering a separate pacing catheter around the HB catheter, which may be difficult and time‐consuming.

Methods and Results: This study prospectively evaluated the use of a single standard octapolar HB catheter with 2‐mm interelectrode spacing for simultaneous (para‐Hisian) pacing from the distal bipole and recording from the three proximal bipoles in 148 consecutive patients. Para‐Hisian pacing was successful in 146 of 148 patients, performed within a median of only 10 seconds, and easily repeated several times during the course of an electrophysiologic study. Retrograde HB activation could he recorded in 132 of 146 patients; a clearly different surface ECG configuration confirmed the presence or absence of HB capture in all other patients. Interestingly, stable RV pacing could he performed from the HB catheter for the rest of the electrophysiologic study in 138 of 142 patients in whom this was tried. RV pacing from this site also led to better interpretation of retrograde conduction, due to clear visualization of retrograde HB activation.

Conclusion: Pacing from the distal dipole of a regular diagnostic HB catheter provides a fast and reliable way to perform para‐Hisian pacing. Therefore, it may be advocated as a routine diagnostic protocol during electrophysiologic procedures. Moreover, pacing from this site obviates the need for a separate RV pacing catheter in most patients.
Ablation of Ventricular Tachycardia Due to a Postinfarct Ventricular Septal Defect:
Authors: ELLISON KRISTIN E. , STEVENSON WTLLIAM G. , COUPER GREGORY S. , FRIEDMAN PETER L.
Published: April 2007

Outer Loop Tachycardia. Introduction: Ventricular tachycardia (VT) alter postinfarct ventricular septal defect (VSD) repair has not been well characterized.

Methods and Results: A 55‐year‐old man developed refractory VT after inferior wall infarction and VSD repair. Entrainment demonstrated a broad reentry circuit path (outer loop) between the tricuspid annulus and VSD patch. A series of radiofrequency (RF) lesions transected this path, abolishing VI’ and producing conduction block between the inferior and superior aspects of the basal right ventricular septum.

Conclusion: Some VTs have broad reentry loops requiring ablation by a series of RF lesions across the path to create a line of block. This approach is analogous to that for atrial flutter.
Carotid Sinus Hypersensitivity in Patients Undergoing Coronary Arteriography:
Authors: KALLIKAZAROS IOANNIS , STRATOS COSTAS , TSIOUFIS COSTAS , STEFANADIS CHRISTODOULOS , SIDERIS ASIMAKIS , SIDERIS SKEVOS , TOUTOUZAS PAVLOS
Published: April 2007

Carotid Sinus Hypersensitivity and Atherosclerosis. Introduction: The purpose of the present investigation was to study the precise relationship between carotid sinus hypersensitivity (CSH) and both the severity of carotid atherosclerosis and the extent of coronary artery disease in patients who were referred for evaluation for suspected ischemic heart disease.

Methods and Results: Duplex echocardiography and coronary angiography were used to assess carotid and coronary artery atherosclerosis in 130 consecutive patients. Carotid sinus stimulation was performed before coronary arteriography with simultaneous recordings of the ECG and aortic pressure. Coronary artery disease was present in 103 patients (79%). Thirty patients (23.08%) had one‐vessel disease (1‐VD), 31 (23.85%) had 2‐VD, 29 (22.31%) had 3‐VD, and 13 patients (10%) had left main coronary artery disease. Carotid artery atherosclerosis was present in 100 patients (76.92%) and carotid disease (diameter stenosis ≥ 50%) was present in 24 patients (18.46%). CSH was found in 33 patients (25%). The incidence of CSH was 9% in patients with carotid stenosis 1%‐15%, 17% in patients with stenosis 16%‐49%, 85% in patients with stenosis 50%‐79%, and 100% in patients with stenosis ≥ 80%. The incidence of CSH was 11%, 17%, 23%, 34%, and 62% in patients with no VD, 1‐VD, 2‐VD, 3‐VD, and left main coronary artery disease, respectively. Stepwise multiple logistic regression analysis revealed that carotid disease and left main coronary artery disease were the most significant determinants of CSH (P < 0.001 and P = 0.013, respectively).

Conclusion: The incidence of CSH increased in proportion to the severity of carotid and coronary atherosclerosis. These data provide evidence that CSH is closely related to severe carotid atherosclerosis or left main coronary artery disease in patients being evaluated for suspected ischemic heart disease.
Comparison of the Effects of Regional Ischemia and Hyperkalemia on the Membrane Action Potentials of the In Situ Pig Heart
Authors: WATANABE ICHIRO , KANDA AKIHIRO , ENGLE CONNIE L. , GETTES LEONARD S.
Published: April 2007

APD During Ischemia. Introduction: This study was designed to determine the role of increased extracellular potassium [K+]e on action potential duration (APD) in the in situ porcine heart during acute regional no‐flow ischemia.

Methods and Results: In open chest, anesthetized swine, an arterial shunt from the carotid artery to the mid‐left anterior descending coronary artery was created through which a solution of KCl was infused to raise [K+]e, Myocardial [K+]e, was determined by potassium‐sensitive electrodes, and transmembrane action potential was recorded by floating glass microelectrode. During the first 2 minutes of ischemia, APD at 90% repolarization (APD90) lengthened by 31.2 ± 1.1 msec (P < 0.05). The comparable increase in [K+]e alone shortened APD90, During the next 6 minutes of ischemia. [K+]e, rose to 11.3 ± 0.3 mM and APD90, showed a decrease. However, the comparable increase in |K+]e, by infusion of KCl caused further shortening of APD90, at similar levels of [K+]e.

Conclusions: Acutely ischemic myocardium showed a brief increase in APD90, during the first 2 minutes of ischemia, followed by a fall in APD90, after 2 minutes of ischemia, but the shortening is less than anticipated by the rise in [K+]e. Thus, we hypothesize that other component(s) of ischemia may inhibit action potential repolarization.
Importance of Electrode Conductive Surface Area and Edge Effects on Ventricular Defibrillation Efficacy
Authors: TOMASSONI GERY , Ph.D. RAJESH PENDEKANTI , DIXON‐TULLOCH ELLEN , MINER BILL , FAIN ERIC S. , HOFEMANN DREW A. , WOLF PATRICK D.
Published: April 2007

Surface Area, Edge Effects, and Ventricular Defibrillation. Introduction: The role of edge effects and electrode surface area of the right ventricular (RV) trausveuous lead (TVL) on defibrillation efficacy is unknown.

Methods and Results: Defibrillation threshold (DFT) testing was conducted randomly in 12 dogs using ring electrode leads in an RV/SVC (superior vena cava) or RV/SVC/patch system. The leads (RV‐4, RV‐8t, RV‐8, RV‐15) had electrode surface areas of 20%, 20%, 40%, and 70%, respectively. A computer model predicted the magnitude of electrode surface current (RV‐8t > RV‐4 > RV‐8 > RV‐15) and the potential distribution (PD) at four sites: electrode surface (site a) and at 2 mm (b), 4 mm (c), and 8 mm (d) away from the surface. Despite different near‐field PDs (sites a, b, c), PDs were nearly identical at site d. Resistance decreased as the surface area increased. DFT energy for the RV‐15 lead was lower than the RV‐4 and RV‐8t. There was no difference between energy requirements for the RV‐15 and RV‐8 leads. No difference was found in DFT current for each lead. Comparison of the RV‐8t and RV‐4 leads showed no difference in DFT energy despite a lower resistance and a greater number of edges.

Conclusions: Increasing the RV TVL surface area lowered the resistance. However, surface area coverages ≥ 40% did not lower DFT energy. No significant change in DFT current occurred despite different predicted near‐Held current densities. PDs were nearly identical 8 mm from the electrode surface. Thus, the far‐field current density appears to play a more important role in determining defibrillation success.
Critical Atrial Site for Ablation of Pacing‐Induced Atrial Fibrillation in the Normal Dog Heart
Authors: TONDO CLAUDIO , SCHERLAG BENJAMIN J. , OTOMO KENICHIRO , ANTZ MATTHIAS , PATTERSON EUGENE , ARRUDA MAURICIO , JACKMAN WARREN M. , LAZZARA RALPH
Published: April 2007

Site for Ablation of AF in Dogs. Introduction: Radiofrequency catheter ablation (RFA) has been used recently to treat atrial fibrillation (AF). The purpose of this study was to investigate a new approach to preventing AF by RFA.

Methods and Results: In open chest, anesthetized dogs, AF (lasting > 30 sec) was induced after burst stimulation, and electrophysiologic parameters were recorded before and after RFA. In group 1 (9 dogs) we performed selective and combined slow and fast pathway RFA, whereas in group 2(11 dogs) RFA was applied as a linear lesion at the mid‐atrial septum between the inferior vena cava and the fossa ovalis. After ablation, the Wenckebach cycle length was significantly prolonged only in group 1 (194 ± 23 vs 282 ± 35 msec, P = 0.002). whereas the interval between the stimulus (S) artifact applied at the high right atrium to the His hundle (H) (SH interval) prolonged to the same extent in both groups (162 ± 14 vs 146 ± 45 msec. P = NS); group 1 due to an A‐H prolongation whereas in group 2 it was due to an intra‐atrial conduction delay. In group 1 AF still remained inducible, although with a longer mean R‐R interval (215 ± 16 vs 433 ± 88 msec, P < 0.05). No instance of complete AV block developed. In group 2, sustained AF was noninducible in 10 dogs and its duration was markedly shorter in the remaining one (8 sec). Gross anatomy and histology did not reveal any damage inside of Koch's triangle, and particularly to the compact AV node.

Conclusion: These findings suggest that RFA at the mid‐atrial septum prevents AF in the normal dog heart. This approach might also be successful in those clinical settings in which the atrial septum plays a critical role in the maintenance of sustained AF.
Retrograde Supernormal Conduction in Concealed Accessory Atrioventricular Pathway Following Catheter Ablation
Authors: SUGUTA MASAHIKO , NOGAMI AKIHIKO , NAITO SHIGETO , OSHIMA SHIGERU , TANIGUCHI KOICHI , AONUMA KAZUTAKA , IESAKA YOSHITO
Published: April 2007

Supernormal Conduction in Concealed Kent Following Ablation. A case is presented of a 63‐year‐old woman with a concealed accessory pathway that exhibited retrograde supernormal conduction after radiofrequency catheter ablation. Although ventricular pacing at a slow rate revealed no retrograde conduction over the accessory pathway following ablation, the tachycardia recurred 15 months later. During ventricular pacing there was retrograde 1:1 conduction over the accessory pathway at a fast rate while there was intermittent VA dissociation with rare retrograde conduction at the slower rate. Ventricular extrastimulus testing demonstrated a supernormal conduction zone of the coupling interval. Thus, accessory pathways may exhibit supernormal conduction after catheter ablation. Pacing should be performed at both slow and fast rates to confirm the presence of conduction block following ablation.
Radiofrequency Catheter Ablation of Ventricular Tachycardia Late After Myocardial Infarction
Authors: STEVENSON WILLIAM G. , FRIEDMAN PETER L. , GANZ LEONARD I.
Published: April 2007

Ablation of VT After MI. Radiofrequency catheter ablation is a promising method for controlling ventricular tachycardia (VT) due to prior myocardial infarction. Limitations of mapping and ablation techniques have largely restricted its use to selected patients who have hemodynamically tolerated sustained monomorphic VT that allows catheter mapping. Multiple monomorphologies of VT, which are usually present, often complicate the ablation procedure and interpretation of ablation effects. Ablation is generally restricted to experienced centers and is usually reserved for patients who have failed other therapies. Despite these difficulties, successful ablation can he life‐saving in patients with incessant VT and can markedly improve quality of life with frequent shocks from implantable defibrillators.
Management of the Child with Wolff‐Parkinson‐White Syndrome and Supraventricular Tachycardia:
Authors: GARSON ARTHUR , KANTER RONALD J.
Published: April 2007

Management of the Child with WPW. In the next decade, “better” management will be defined by cost effectiveness including morbidity, mortality, and cost. We used a cost‐effectiveness model for children with Wolff‐Parkinson‐White syndrome (WPW) and supraventricular tachycardia (SVT) comparing medical, surgical, and catheter ablative treatment between age 5 years (estimated average age at first recurrence after infancy) and age 21. Charges were quantitated from actual hospital bills; mortality was estimated from the literature; morbidity was assessed by estimating the number of hours in SVT, hours in clinic, hours in routine hospital bed, and hours in hospital intensive care; and the hours were then multiplied by a severity factor, normalized to 1.0 for 1 hour of SVT (0.5 for 1 hour in clinic, 0.75 for routine hospital, and 2.0 for intensive care). Overall charges (5 to 21 years old) for catheter ablation ($17,236) were 39% of surgical management and 57% of medical management; estimated mortality for catheter ablation (5 to 21 years old including failures that reverted to medical management) was 0.15%, which was 10% of medical management and 28% of surgical management; morbidity for catheter ablation was 27.6 units, which was 32% of medical management and 36% of surgical management. Sensitivity analysis demonstrated that the catheter ablation strategy remained preferable throughout the range of plausible values of cost, mortality, and morbidity (including a repeat procedure for initial failures). Therefore, catheter ablation has lower cost, mortality, and morbidity than either medical management or surgery and is the treatment of choice for the child 5 years of age or older with WPW and SVT. This type of analysis can be used for other forms of chronic disease in children.
Three‐Dimensional Electromagnetic Catheter Technology:
Authors: KOTTKAMP HANS , HINDRICKS GERHARD , BREITHARDT GÜNTER , BORGGREFE MARTIN
Published: April 2007

Electroanatomical Mapping. Introduction: The difficult catheter orientation and navigation associated with conventional technology and mono‐/multiplane fluoroscopy may complicate ablation procedures of atrial tachycardias. A new three‐dimensional catheter technology for electroanatomical mapping of the right atrium and ablation of ectopic atrial tachycardia is described.

Methods and Results: A novel electromagnetic catheter‐based mapping system was investigated for electroanatomical mapping of the entire right atrium in 12 patients. The system reconstructed three‐dimensional maps from the multitude of endocardial sites that were sequentially mapped and color coded the individual activation times. The electrophysiologic information was superimposed on the geometry of the mapped area. The anatomical landmarks of the right atrium, i.e., the tricuspid annulus. mouth of the coronary sinus, ostia of the superior and inferior venae cavae, and right atrial appendage, could he depicted in all cases. The sinus node area and the preferential conduction along the crista terminalis could be delineated. In four patients with ectopic atrial tachycardia, the earliest endocardial activation could be identified with high spatial resolution as a “hot spot.” After completion of the mapping procedure, the ablation catheter could be reliably renavigated to the site of origin, and ablation was successful with one or two impulses. In one patient with previous atrial septal repair, the activation map allowed the reconstruction of a long line of conduction block induced by the atriotoniy.

Conclusion: Three‐dimensional electroanatomical mapping of the right atrium allowed detailed reconstruction of the chamber geometry and activation sequence. The sites of origin of ectopic atrial tachycardias could be identified precisely. The system allowed accurate renavigation to the site of earliest activation, thereby guiding successful ablation of the foci.
Electrocardiographic Markers of Late Sudden Death Risk in Postoperative Tetralogy of Fallot Children
Authors: BERUL CHARLES I. , HILL SHARON L. , GEGGEL ROBERT L. , HIJAZI ZIYAD M. , MARX GERALD R. , RHODES JONATHAN , WALSH KERRI A. , EULTON DAVID R.
Published: April 2007

Late Sudden Death Risk in Postoperative TOF. Following surgery for tetralogy of Fallot (TOP), children may develop late onset ventricular arrhythmias. Many patients have both depolarization and repolarization abnormalities, including right bundle branch block (RBBB) and QT prolongation. The goal of this study was to improve prospective risk‐assessment screening for late onset sudden death. Resting ECG markers including QRS duration, QTc, JTc, and interlead QT and JT dispersion were statistically analyzed to identify those patients at risk for ventricular arrhythmias and sudden cardiac death. To determine predictive markers for future development of arrhythmia, we examined 101 resting ECGs in patients (age 12 ± 6 years) with postoperative TOF and RBBB, 14 of whom developed late ventricular tachycardia (VT) or sudden death. These ECGs were also compared with an additional control group of 1000 age‐ and gender‐matched normal ECGs. The mean QRS (± SD) in the VT group was 0.18 ± 0.02 seconds versus 0.14 ± 0.02 seconds in the non‐VT group (P < 0.01). QTc and JTc in the VT group was 0.53 ± 0.05 seconds and 0.33 ± 0.03 seconds compared with 0.50 ± 0.03 seconds and 0.32 ± 0.03 seconds in the non‐VT group (P = NS). There was no increase in QT dispersion among TOF patients with VT or sudden death compared with control patients or TOF patients without VT, although JT dispersion was more common in the TOF groups. A prolonged QRS duration in postoperative TOF with RBBB is more predictive than QTc, JTc, or dispersion indexes for identifying vulnerability to ventricular arrhythmias in this population, while retaining high specificity. The combination of both QRS prolongation and increased JT dispersion had very good positive and negative predictive values. These results suggest that arrhythmogenesis in children following TOF surgery might involve depolarization in addition to repolarization abnormalities. Prospective identification of high‐risk children may be accomplished using these ECG criteria.
Inappropriate Sinus Tachycardia After Radiofrequency Ablation of Para‐Hisian Accessory Pathways
Authors: PAPPONE CARLO , STABILE GIUSEPPE , ORETO GIUSEPPE , DE SIMONE ANTONIO , RILLO MARIANO , MAZZONE PATRIZIO , CAPPATO RICCARDO , CHIERCHIA SERGIO
Published: April 2007

Inappropriate Sinus Tachycardia After Catheter Ablation. Introduction: Inappropriate sinus tachycardia (IST) has been observed following radiofrequency ablation (RFA) of the AV nodal fast pathway. This study was aimed to prospectively analyze the incidence and clinical significance of IST following RFA of para‐Hisian accessory pathways (APs).

Methods and Results: Twenty‐eight patients (pts) with para‐Hisian APs underwent RFA. An AP was defined as para‐Hisian whenever its atrial and ventricular insertions were associated with a His‐bundle potential ≥ 0.1 mV. RF current was always delivered at the atrial aspect of the tricuspid annulus. to a site where the His‐bundle potential was < 0.15 mV. Time‐ and frequency‐domain analysis of heart rate variability was performed in 22 patients, before and after RFA. Abolition of AP conduction was obtained in all pts, and no AV conduction alteration occurred. Six pts (21.4%) presented with IST 45 to 240 minutes after the ablation procedure. In 5 of them, IST disappeared spontaneously within 72 hours, whereas in 1 pt β‐blockers were required for 2 months. The atrial potential amplitude (1.217 ± 0.264 mV vs 0.882 ± 0.173 mV, P = 0.009) and A/V potential amplitude ratio (2.633 vs 1.686, P = 0.05) were significantly higher in pts who developed IST than in those who did not. A marked decrease in heart rate variability was observed only in pts who developed IST.

Conclusion: IST is a relatively frequent complication after RFA of para‐Hisian APs: it is generally short‐lasting and usually does not require any treatment. IST after catheter ablation is likely to depend upon transient parasympathetic denervation of the sinus node.
Architecture of the Atrial Musculature In and Around the Triangle of Koch:
Authors: SANCHEZ‐QUINTANA DAMIAN , WYN DAVIES D. , YEN HO SIEW , OSLIZLOK PAUL , ANDERSON ROBERT H.
Published: April 2007

Atrial Fibers. Introduction: Recent studies suggest that atrial fibers in the approaches to the AV node form part of the dual pathways recognized electrophysiologically in patients with AV nodal reentrant tachycardia (AVNRT). Our aim was to determine, by gross dissection, the arrangement of the superficial musculature in the area of the triangle of Koch In normal hearts and in hearts with documented AVNRT. hoping to ascertain anatomic features that might contribute to the debate.

Methods and Results: We used blunt dissection to study the architecture of the superficial atrial musculature in 16 autopsied hearts from adults who died of noncardiac disease. A well‐defined pattern of architecture of muscle fibers was found in the region of the triangle of Koch, showing marked variations in 7 of the 16 specimens. The relationship of these fibers to the histologically specialized AV node was confirmed by histology in three cases. Two hearts from patients with known AVNRT, treated by ablation in one, were examined further histologically. These sections showed that the site of ablation was well distant from the histologically discrete AV node.

Conclusion: The variability in the arrangement of the superficial atrial muscle fibers in the area of the triangle of Koch may be one of the factors influencing the route for impulses entering the AV node. Lesions that ablate nodal reentry are within these atrial fibers rather than the histologically specialized AV node.
Low‐Energy Transvenous Cardioversion of Atrial Fibrillation Using a Single Atrial Lead System
Authors: HEISEL ARMIN , JUNG JENS , NEUZNER JORG , MICHEL ULI , PITSCHNER HEINZ
Published: April 2007

Atrial Cardioversion Using a Single Atrial Lead System. Introduction: Clinical studies have shown that electrical conversion of atrial fibrillation (AF) is feasible with transvenous catheter electrodes at low energies. We developed a single atrial lead system that allows atrial pacing, sensing, and defibrillation to improve and facilitate this new therapeutic option.

Methods and Results: The lead consists of a tripolar sensing, pacing, and defibrillation system. Two defibrillation coil electrodes are positioned on a stylet‐guided lead. A ring electrode located between the two coils serves as the cathode for atrial sensing and pacing. We used this lead to cardiovert patients with acute or chronic AE. The distal coil was positioned in the coronary sinus, and the proximal coil and the ring electrode in the right atrium. R wave synchronized biphasic shocks were delivered between the two coils. Atrial signal detection and pacing were performed using the proximal coil and the ring electrode. Eight patients with acute AF (38 ± 9 min) and eight patients with chronic AF (6.6 ± 5 months) were included. The fluoroscopy time for lead placement was 3.5 ± 4.3 minutes. The atrial defibrillation threshold was 2.0 ± 1.4 J for patients with acute AE and 9.2 ± 5.9 J for patients with chronic AF (P < 0.01). The signal amplitude detected was 1.7 ± 1.1 mV during AF and 4.0 ± 2.9 mV after restoration of sinus rhythm (P < 0.001). Atrial pacing was feasible at a threshold of 4.4 ± 3.3 V (0.5‐msec pulse width).

Conclusions: Atrial signal detection, atrial pacing, and low‐energy atrial defibrillation using this single atrial lead system is feasible in various clinical settings. Tbis system might lead to a simpler, less invasive approach for internal atrial cardioversion.
QT and JT Dispersion in Children with Long QT Syndrome
Authors: SHAH MAULLY J. , WIEAND TAMMY S. , RHODES LARRY A. , BERUL CHARLES I. , VETTER VICTORIA L.
Published: April 2007

QT and JT Dispersion in Long QT Syndrome. Introduction: Abnormalities of ventricular repolarization leading to ventricular arrhythmias place children with long QT syndrome at high risk for sudden death. Dispersion of the QT (QTd) and JT (JTd) intervals, as markers of cardiac electrical heterogeneity, may be helpful in evaluating children with long QT syndrome and identifying a subset of patients at high risk for development of critical ventricular arrhythmias (ventricular tachycardia, torsades de pointes, and/or cardiac arrest).

Methods and Results: The QTd and JTd intervals in 39 children with long QT syndrome were compared to those of 50 normal age‐matched children. In the long QT syndrome group, QTd measured 81 ± 70 msec compared to 28 ± 14 msec in the control group (P < 0.05), and JTd in the long QT syndrome group was 80 ± 69 msec compared to 25 ± 15 msec in the control group (P < 0.05).

Conclusion: Children with long QT syndrome have an increased QTd and JTd when compared to normal controls. A QTd or JTd ≥ 55 msec correlates with the presence of critical ventricular arrhythmias. These ECG measures of dispersion can be useful in stratifying children with the long QT syndrome who are at higher risk for developing critical ventricular arrhythmias.
Optimized First Phase Tilt in “Parallel‐Series” Biphasic Waveform
Authors: YAMANOUCHI YOSHIO , MOWREY KENT A. , KROLL MARK W. , BREWER JAMES E. , DONOHOO ANN M. , WILKOFF BRUCE L. , TCHOU PATRICK J.
Published: April 2007

“Parallel‐Series” Biphasic Waveform. Introduction: A biphasic defibrillation waveform can achieve a large second phase leading‐edge voltage by a “parallel‐series” switching system. Recently, such a system using two 30‐μF capacitances demonstrated better defibrillation threshold than standard waveforms available in current implantable devices. However, the optimized tilt of such a “parallel‐series” system had not been defined.

Methods and Results: Defibrillation thresholds were evaluated for five different biphasic “parallel‐series” waveforms (60/15 μF) and a biphasic “parallel‐parallel” waveform (60/60 μF) in 12 anesthetized pigs. The five “parallel‐series” waveforms had first phase tilts of 40%, 50%, 60%, 70%, and 80% with second phase pulse width of 3 msec. The “parallel‐parallel” waveform had first phase tilt of 50% with second phase pulse width of 3 msec. The defibrillation lead system comprised a left pectoral “hot can” electrode (cathode) and a right ventricular lead (anode). The stored energy at defibrillation threshold of the “parallel‐series” waveform with first phase tilts of 40%, 50%, 60%, 70%, and 80% was 7.0 ± 2.1, 6.1 ± 2.8, 6.8 ± 2.8, 7.2 ± 2.9. and 8.4 ± 3.1 J, respectively. The stored energy of the “parallel‐series” waveform with a 50% first phase tilt was 16% less than the nonswitching “parallel‐parallel” waveform (7.3 ± 2.8 J, P = 0.006).

Conclusions: A first phase tilt of 50% maximized defibrillation efficacy of biphasic waveforms implemented with a “parallel‐series” switching system. This optimized “parallel‐series” waveform was more efficient than the comparable “parallel‐parallel” biphasic waveform having the same first phase capacitance and tilt.
Electrophysiologic Effects of Interactions Between Activated Canine Neutrophils and Cardiac Myocytes
Authors: HOFFMAN BRIAN F. , FEINMARK STEVEN J. , GUO SHI‐DUO
Published: April 2007

Effects of Neutrophils on Cardiac Myocytes. Introduction: Myocardial ischemia causes neutrophils to bind to activaled myocytes and liberate platelet‐activating factor (PAF). PAF causes delayed repolarization, early afterdepolarizations (EADs), and arrest of repolarization. We studied the effect of activation of neutrophils bound to canine cardiac myocytes to determine if such activation causes PAF generation and similar changes in transmembrane potentials.

Methods and Results: Myocytes from canine left ventricle and neutrophils from the same dog were superfused with Tyrode's solution and transmembrane potentials recorded from the former. Neutrophils (100 μL, 10‐6/mL) were added and allowed to bind to the myocytes. Neutrophils were activated with 1% zymosan‐activated serum (ZAS). CV‐6209 (100 nM) was used to block receptors for PAF. Liberation of PAF by activated neutrophils was quantified with a commercial radioimmunoassay kit. Neutrophils activated with ZAS caused changes in myocyte transmembrane potentials like those induced by PAF: action potential prolongation, runs of EAD, and periods of plateau arrest. PAF receptor blockade prevented neutrophil activation from altering transmembrane potentials. Neutrophils activated with 1 % ZAS liberated significant amounts of PAF.

Conclusions: When neutrophils bound to cardiac myocytes are activated by exposure to 1% ZAS, they cause prompt and consistent changes in myocyte electrical activity that could be arrhythmogenic for the in situ heart. These changes are similar to those caused by PAF in pharmacologic studies. Neutrophils activated in this manner generate PAF, and the effects of their activation are prevented by blockade of PAF receptors. We conclude that, during reperfusion of ischemic myocardium, PAF generated by activated neutrophils most likely is a cause of some arrhythmias.
Bundle Branch Reentry Ventricular Tachycardia with Two Distinct Left Bundle Branch Block Morphologies
Authors: WANG CHAO‐WEN , STERBA RICHARD , TCHOU PATRICK
Published: April 2007

Bundle Branch Reentry VT with Two Morphologies. Introduction: Bundle branch reentry ventricular tachycardia (VT) is usually amenable to treatment with radiofrequency ablation. Different QRS morphologies during VT are possible when anterograde ventricular activation is over the left bundle branch. Manifestations of tbis reentrant tachycardia with more than one QRS morphology with anterograde activation via the right bundle have not been reported and would be unusual due to the more discrete anatomy of the right bundle branch.

Methods and Results: An electropbysiologic study was conducted in a patient with dilated ventricle and diminished ventricular function with VT, Typical characteristics of bundle branch reentry were noted when VT was induced. The study was notable for the presence of a right bundle recording only during macroreentrant beats or VT and the distal location of the recording. Radiofrequency ablation was performed. Postablation stimulation again induced VT, proven to be of the same bundle branch reentry mechanism but of a different QRS morphology. A second ablation was required for complete ablation of this patient's bundle branch reentry VT.

Conclusion: In bundle branch reentry utilizing the left bundle as the retrograde limb and the right bundle branch as the anterograde limb of the circuit, VT of more than one distinct morphology can be seen. Careful evaluation to assess for the persistence of VT of the same mechanism is necessary to ensure complete ablation of the reentrant circuit. Preexisting right bundle disease and a dilated heart with more dispersed distal right bundle branches may predispose to such a phenomenon.
Radiofrequency Ablation‐Induced Asystole During Transaortic Approach for a Left Anterolateral Accessory Pathway
Authors: TSAI CHING‐FUNG , CHEN SHIH‐ANN , CHIANG CHERN‐EN , TAI CHING TAI , LEE SHIH HUANG , WEN ZU‐CHIN , CHEN YI‐JEN , YU WEN CHUNG , HUANG JIN‐LONG , FENG AN‐NING , CHANG MAU‐SONG
Published: April 2007

RF Ablation‐Induced Cardiac Asystole. We present a case of cardiac asystole induced by radiofrequency catheter ablation of a left anterolateral accessory pathway in a 28‐year‐old woman with Wolff‐Parkinson‐White syndrome who was experiencing recurrent palpitation. Radiofrequency current applied on the ventricular aspect of the mitral annulus corresponding to the aforementioned site provoked profound slowing of the sinus rate preceded by disappearance of the preexcitation, and then asystole ensued. The proposed causal mechanism was a reflexogenically mediated hypotension‐bradycardia syndrome (Bezold‐Jarisch‐like phenomenon) through stimulation of either nearby vagal afferent pathways or sensory terminal receptors at the ablation site.
Pretreatment with Antithrombotic Agents During Radiofrequency Catheter Ablation: A Randomized Comparison of Aspirin Versus Ticlopidine
Authors: MANOLIS ANTONIS S. , MAOUNIS THEMOS , VASSILIKOS VASSILIS , MELITA‐MANOLIS HELEN , PSARROS LEFTERIS , TERZOGLOU GEORGE , COKKINOS DENNIS V.
Published: April 2007

Aspirin Versus Ticlopidine in Radiofrequency Ablation. introduction: D‐dimer is a product of fibrin degradation and can serve as a biochemical marker of thrombus formation and reactive fibrinolysis. According to our previous observations, and as reflected by elevated plasma D‐dimer levels, lesions produced by radiofrequency (RF) ablation have a thrombogenic effect, Pretreatment with combined aspirin and ticlopidine mitigates this thrombogenicity; however, the effect of either agent alone remains unknown.

Methods and Results: In this study, 59 patients undergoing RF ablation were randomized to pretreatment with aspirin (group I; n = 30) or ticlopidine (group II; n = 29) for 3 days prior to RF ablation. D‐dimer levels were measured by enzyme immunoassay before and after the electrophysiologic study (EPS), and both immediately and at 48 hours after RF ablation. Results also were compared with those of 31 patients (nonrandomized group III) who bad received both aspirin and ticlopidine. At all stages, D‐dimer levels were higher in groups I and II when compared with group III. Baseline D‐dimer (31 ± 20 vs 24 ± 13 vs 17 ± 11 Mg/L, respectively; P= 0.002) rose after EPS to higher levels in groups I and II (91 ± 100 Mg/L and 51 ± 35 μg/L) compared with group III (31 ± 17 μg/L; P= 0.001). After RF ablation, D‐dimer levels increased in all groups, but this increase was much higher in groups I and II (214 ± 210 μg/L and 201 ± 222 μg/L) than in group III (74 ± 60 μg/L; P= 0.005). At 48 hours, D‐dimer levels decreased in all groups, but remained higher in groups I and II (91 ± 100 μg/L and 95 ± 99 μg/L) than in group III (35 ± 31 μg/L; P= 0.009). There were no differences among the three groups in the number of RF ablation lesions or the duration of the RF ablation procedure.

Conclusion: Pretreatment with aspirin or ticlopidine alone does not decrease the thrombogenic potential of RF ablation. Only combined therapy with aspirin and ticlopidine has a favorable effect, as reflected by the lower degree of D‐dimer elevation.
Does Radiofrequency Ablation Induce a Prethrombotic State? Analysis of Coagulation System Activation and Comparison to Electrophysiologic Study
Authors: DORBALA SHARMILA , COHEN ALICE J. , HUTCHINSON LEIGH A. , MENCHAVEZ‐TAN EDITH , STEINBERG JONATHAN S.
Published: April 2007

Ablation and Coagulation Activation. Introduction: Although thromboembolism is an uncommon complication of radiofrequency (RF) ablation, some preliminary reports have suggested that RF ablation results in activation of the coagulation system, possibly increasing this risk. We hypothesized that the insertion of intravenous catheters and their prolonged intravenous placement rather than RF ablation activates the coagulation cascade.

Methods and Results: Thirty‐seven patients, group 1 (n = 21) during RF ablation, and group 2 (n = 16) during routine electrophysiologic studies (EPS), were studied prospectively. Blood was drawn for coagulation and fibrinolytic studies following insertion of venous sheaths (TO), following catheter placement (T1), and 1 hour after completion of RF ablation or EPS {T2). Conversion of prothrombin to thrombin was measured using thrombin‐antithrombin complex (TAT) and prothrombin activation peptide (F1+2). and fibrinolytic activity was assessed using D‐dlmer concentration. Levels of D‐dimer increased in group 1 from 823.52 ± 323.52 ng/mL at TO to 1,314.28 ± 297.63 ng/mL at T2 (P= 0.005), and in group 2 from 658.15 ± 161.70 ng/mL at T0 to 1625 641.45 ng/mL at T2 (P=±0.064). TAT levels increased from to 27.74 ± 5.6 μg/L at T0 to 52.99 ± 5.93 μg/L at T2 in group 1 (P= 0.09), and from 19.79 ± 5.14 μg/L at T0 to 73.5 ± 24.15 μg/L at T2 in group 2 (P= 0.05). F1+2 concentration increased from 1.52 ± 0.30 nmol/L at T0 to 3.06 ± 0.41 nmol/L at T2 in group 1 (P= 0.004), and from 1.32 ± 0.30 nmol/L at T0 to 3.11 ± 0.46 nmol/L at T2 in group 2 (P= 0.087). There was no significant difference in the concentration of the three coagulation variables between group 1 and group 2 at any given time point. No correlation was demonstrable between concentration of D‐dimers, TAT, or F1+2 and variables of RF delivery such as cumulative energy, number of RF energy applications, or number of impedance rises. However, a significant positive correlation (r = 0.65, P < 0.01) was noted between the duration of the RF ablation procedure and the concentration of D‐dimers.

Conclusion: We conclude that activation of the coagulation cascade in RF ablation procedures is not related to the delivery of RF energy, but is related to the placement of intravascular catheters and to the duration of the ablation procedure.
ST Segment Elevation Induced by Class IC Antiarrhythmic Agents: Underlying Electrophysiologic Mechanisms and Insights into Drug‐Induced Proarrhythmia
Authors: KRISHNAN SUBRAMANIAM C. , JOSEPHSON MARK E.
Published: April 2007

Sodium Block‐Induced ST Segment Elevation. Three patients in whom Class IC sodium channel blockers induced ST segment elevation in leads V1 through V3 are described. The underlying electrophysiologic mechanism, implications for drug‐induced proarrhythmia, and the relationship of the finding to the Brugada syndrome type of idiopathic ventricular fibrillation are discussed.
Atrial Electrograms and Activation Sequences in the Transition Between Atrial Fibrillation and Atrial Flutter
Authors: EMORI TETSURO , FUKUSHIMA KENGO , SAITO HIRONORI , NAKAYAMA KAZUAKT , OHE TOHRU
Published: April 2007

Transition Between Atrial Fibrillation and Flutter. Introduction: The eletrophysiologic mechanism of atrial fibrillation (AF) has a wide spectrum, and it seems that some atrial regions are essential for the occurrence of a particular type of AF. We focused on one type of AF: AF associated with typical atrial flutter (AFI), which was right atrial (RA) arrhythmia, and sought to investigate intra‐atrial electrograms and activation sequences in the transition between AF and AFL.

Methods and Results: Intra‐atrial electrograms and activation sequences in the R.A free wall and the septum were evaluated in the transition between AF and AFL in seven patients without organic heart disease (all men; mean age 57 ± 11 years). In five episodes of the conversion of AFL into AF, the AFL cycle length was shortened (from 211 ± 6 msec in stable AFL to 190 ± 15 msec before the conversion, P, 0.001). Interruption of the AFL wavefront and an abrupt activation sequential change induced by a premature atrial impulse resulted in fractionation and disorganization of the septal electrograms. During sustained AF, septal electrograms were persistently fractionated with disorganized activation sequences. However, the RA free‐wall electrograms were organized, and the activation sequence was predominantly craniocaudal rather than caudocranial throughout AF. In 12 episodes of the conversion of AF into AFL, the AF cycle length measured in the RA free wall increased (from 165 ± 26 msec at the onset of AF to 180 ± 24 msec before the conversion, P, 0.001). AFL resumed when fractionated septal electrograms were separated and organized to the caudocranial direction, despite the RA free‐wall electrograms remaining discrete and sharp with an isoelectric line.

Conclusion: Changes of the electrogram and activation sequence in the atrial septum played an important role in the transition between AF and AFL.