bluuebunny/crossref_metadata_2025_split huggingface dataset:
Retrograde Multiple and Multifiber Accessory Pathway Conduction in the Wolff‐Parkinson‐White Syndrome:
Authors: IESAKA YOSHITO , YAMANE TEIICHI , TAKAHASHI ATSUSHI , GOYA MASAHIKO , KOJIMA SHIGEYUKI , SOEJIMA YOHKOH , OKAMOTO YOSHIHIRO , FUJIWARA HIDEOMI , AONUMA KAZUTAKA , NOGAMI AKIHIKO , HIROE MICHIAKI , MARUMO FUMIAKI , HIRAOKA MASAYASU 
Published: April 2007

Retrograde Multiple Accessory Pathway Precipitating AF. Introduction: The determinants of susceptibility to atrial fibrillation (AF) and the existence of accessory pathway conduction have remained unidentified in the Wolff‐Parkinson‐White (WPW) syndrome. We tested the hypothesis that excitation inputs into the atrium over a retrograde multiple or multifiber accessory pathway during AV reentrant tachycardia (AVRT) could precipitate initiation of AF. Methods and Results: Two hundred fifty consecutive patients with WPW syndrome underwent electrophysiologic study and radiofrequency catheter ablation. The patients were classified into two groups according to the study results: 29 with retrograde multiple or multifiber accessory pathway (MP) and 221 with retrograde single accessory pathway (SP). Compared with the SP patients, the MP patients showed a significantly higher incidence of clinical AF (MP vs SP: 19/29 vs 51/221, P < 0.01), induced AF (12/29 vs 32/221, P < 0.01), and initiated AF during ventricular pacing and AVRT (10/12 vs 17/32, P < 0.05). There were no differences between the two groups in incidence of clinical and induced AVRT (24/29 vs 200/221 and 25/29 vs 206/221, respectively), mean cycle length of induced AVRT, or electrophysiologic parameters of the accessory pathway. AF inducibility during AVRT or ventricular pacing was eliminated by partial ablation in 7 of 10 patients with MP. After total ablation, the incidence of induced AF was similar between the two groups (MP vs SP: 1/29 vs 11/221). Conclusion: The existence of a retrograde multiple or multifiber accessory pathway in patients with WPW syndrome is associated with a higher incidence of clinical and induced AF. Successful ablation of the retrograde multiple or multifiber accessory pathway can eliminate the induction of both AVRT and AF.
Acute and Long‐Term Effects of Consecutive Radiofrequency Applications on Conduction Properties of the Subeustachian Isthmus in Type I Atrial Flutter
Authors: SCHUMACHER BURGHARD , PFEIFFER DIETRICH , TEBBENJOHANNS JÜRGEN , LEWALTER THORSTEN , JUNG WERNER , LÜDERITZ BERNDT 
Published: April 2007

Effects of Atrial Flutter Ablation. Introduction: Bidirectional conduction block at the subeustachian isthmus predicts long‐term efficacy of atrial flutter ablation. Limited data are available on the incidence and outcome of minor conduction changes such as unidirectional or incomplete block. This prospective study sought to systematically assess discrete acute and long‐term alterations of bidirectional conduction prior to a complete conduction block. Methods and Results: In 41 patients with type I atrial flutter, pulse propagation through the subeustachian isthmus during low lateral and proximal coronary sinus pacing was documented and analyzed following each consecutive radiofrequency (RF) application. In cases of altered conduction properties and noninducibility of atrial flutter, patients were followed‐up for 12 months. Three sets of results were found. First, following RF application. 23 patients presented a progressive conduction delay prior to a complete conduction block. Second, RF application did not always affect counterclockwise and clockwise conduction simultaneously or to the same extent. In 13 patients, an initial alteration of counterclockwise conduction was present before an alteration of clockwise conduction; in 5 patients, clockwise conduction was primarily affected. Third, the recurrence rate of typical atrial flutter was 9% (2/22) in patients with a complete bidirectional conduction block, 54% (7/13) in patients with unidirectional conduction block, and 100% (6/6) in patients with sole bidirectional conduction delay. Conclusion: In 50% of the patients, consecutive RF applications resulted primarily in a progressive conduction delay rather than a sudden conduction block. Since counterclockwise and clockwise conduction were not always affected simultaneously or to the same extent, lateral as well as septal pacing is recommended for improvement of bidirectional conduction block. Normalization of primarily altered conduction and, therefore, recurrence of atrial flutter are high in all patients without bidirectional block.
Endocardial and Epicardial Ablation Guided by Nonsurgical Transthoracic Epicardial Mapping to Treat Recurrent Ventricular Tachycardia
Authors: SOSA EDUARDO , SCANAVACCA MAURICIO , D'AVILA ANDRE , PICCIONI JOÃO , SANCHEZ OSVALDO , VELARDE JOSÉ L. , SILVA MARCIO , REOLÃO BASILEO 
Published: April 2007

Nonsurgical Epicardial Ablation. Introduction: An epicardial site of origin of ventricular tachycardia (VT) may explain unsuccessful endocardial radiofrequency (RF) catheter ablation. A new technique to map the epicardial surface of the heart through pericardial puncture was presented recently and opened the possibility of using epicardial mapping to guide endocardial ablation or epicardial catheter ablation. We report the efficacy and safety of these two approaches to treat 10 consecutive patients with VT and Chagas’ disease. Methods and Results: Epicardial mapping was carried out with a regular steerable catheter introduced into the pericardial space. An epicardial circuit was found in 14 of 18 mapable VTs induced in 10 patients. Epicardial mapping was used to guide endocardial ablation in 4 patients and epicardial ablation in 6. The epicardial earliest activation site occurred 107 ± 60 msec earlier than the onset of the QRS complex. At the epicardial site used to guide endocardial ablation, earliest activation occurred 75 ± 55 msec before the QRS complex. Epicardial mid‐diastolic potentials and/or continuous electrical activity were seen in 7 patients. After 4.8 ± 2.9 seconds of epicardial RF applications, VT was rendered noninducible. Hemopericardium requiring drainage occurred in 1 patient; 3 others developed pericardial friction without hemopericardium. Patients remain asymptomatic 5 to 9 months after the procedure. Interruption during endocardial pulses occurred after 20.2 ± 14 seconds (P = 0.004), hut VT was always reinducible and the patients experienced a poor outcome. Conclusion: Epicardial mapping does not enhance the effectiveness of endocardial pulses of RF. Epicardial applications of RF energy can safely and effectively treat patients with VT and Chagas’ disease.
Temporal Stability of Defibrillation Thresholds with an Active Pectoral Lead System
Authors: OLSOVSKY MARY R. , PELTNI MICHAEL A. , SHOROESKY STEPHEN R. , GOLD MICHAEL R. 
Published: April 2007

Stability of Defibrillation Thresholds. Introduction: Monophasic defibrillation thresholds rise over time with a variety of lead systems. These chronic changes are attenuated or eliminated by biphasic waveforms, although the effect appears dependent upon the lead system. With the downsizing of pulse generator size to allow for routine pectoral implantation, active can lead systems have now become standard. However, the temporal stability of such lead systems has not been evaluated previously. Methods and Results: This study was a prospective assessment of the changes of active pectoral defibrillation thresholds over time. Thresholds were measured at implant, predischarge, and at a mean follow‐up of 50 days in 46 patients with a uniform testing protocol and shock polarity. The lead system was a dual‐coil Endotak DSP lead with an active pectoral pulse generator. Defibrillation thresholds were 9.9 ± 5.5 J at implantation, 8.5 ± 6.0 J predischarge, and 7.6 ± 5.5 J at follow‐up (ANOVA, P = 0.007). Moreover, only two patients developed an increased threshold > 5 J, and no patient had an inadequate safety margin at follow‐up. Conclusion: These results indicate that active pectoral defibirillation thresholds are stable over the first 2 months postimplantation and question the need for routine serial defibrillation threshold testing.
Enhanced Detection Criteria in Implantable Defibrillators
Authors: BRUGADA JOSEP , MONT LLUIS , FTGUEIREDO MARCIO , VALENTINO MARIANA , MATAS MARIONA , NAVARRO‐LÓPEZ FRANCISCO 
Published: April 2007

Enhanced Tachycardia Detection Algorithm introduction: Enhanced detection criteria in third‐generation implantable defibrillators have been implemented to avoid inappropriate therapy of fast supraventricular arrhythmias. We prospectively analyzed the use of these criteria in patients with an implantable defibrillator with electrogram storing capability. Methods and Results: In 82 consecutive patients with a Guidant‐CPI implantable defibrillator, sudden onset > 9% and stability < 40 msec were systematically programmed in zone 1 of therapy together with a sustained rate duration security mechanism. All detected tachycardia episodes were analyzed. The study population consisted of 59 patients who had at least one episode of tachycardia detected in zone 1 during follow‐up. The tachycardia rate in zone 1 never exceeded 210 beats/min. Twenty patients had no episodes during follow‐up, and three patients had episodes detected exclusively in zone 2 of therapy. Supraventricular arrhythmias were detected frequently in the ventricular tachycardia zone (193 of 690 tachycardia episodes in 23 of 59 patients). Use of sudden onset was very effective in detecting sinus tachycardias (65 of 67 episodes), and stability was very useful in detecting atrial fibrillation (31 of 32 episodes). However, sensitivity in detecting ventricular tachycardia was only 90% (451 of 497 episodes). Application of the sustained rate duration criterion allowed appropriate treatment of all ventricular tachycardia episodes, increasing sensitivity to 100%; however, specificity in appropriate non‐treatment of supraventricular decreased from 96% to 83%. Subsequent analysis of different algorithms applied to our data showed that sudden onset > 9% and stability < 40 msec was the algorithm with the best specificity and sensitivity. Conclusion: Programming sudden onset and stability detection criteria with a sustained rate duration safety net for triggering tachycardia therapy results in appropriate device management in most patients with supraventricular and slow (< 210 beats/min) ventricular tachycardias.
Mechanisms of Induction of Typical and Reversed Atrial Flutter
Authors: COSÍO FRANCISCO G. , LÓPEZ‐GIL MARÍA , ARRIBAS FERNANDO , GONZÁLEZ H. DANIEL 
Published: April 2007

Mechanisms of Flutter Induction. Introduction: Typical flutter is due to reentry around caval veins and terminal crest. In patients with typical flutter, reversed (clockwise) reentry can be induced. We studied mechanisms of typical and reversed flutter induction. Methods and Results: Thirteen patients (11 men) underwent 16 radiofrequency (RF) ablation procedures for typical (12) or reversed flutter (1), High right atrium (RA) stimulation included 1 to 3 extrastimuli over cycle lengths 6(M) to 250 msec, and burst. We recorded simultaneously from three levels of septal and anterior RA. RF was delivered to the inferior vena cava‐tricuspid isthmus (CTI). Of 25 inductions, 4 were a result of single, 9 double, and 11 triple extrastimuli, and 1 burst. Clinical basal flutter was induced (7 typical, 1 reversed). After RF, typical flutter was reinduced in 9 cases and reversed flutter in 7, with only typical flutter seen clinically. All flutters were interrupted by ablation or catheter pressure on the CTI. Typical flutter began by low RA septal activation block, preceded by repetitive responses in 12 instances, atypical flutter in 1, and directly from stimuli in 4. Reversed flutter started in 8 instances by low RA block of a stimulated front descending the anterior wall and in 1 by repetitive responses. Conclusion: Septal activation block was the usual mechanism of typical flutter induction by RA extrastimuli. Facilitation of reversed flutter after RF application is probably due to a new area of block in the CTI. Flutter induction without intermediate rhythms confirms the presence of block at the terminal crest at baseline.
Reduced Inward Rectifying and Increased E‐4031‐Sensitive K+ Current Density in Arrhythmogenic Subendocardial Purkinje Myocytes from the Infarcted Heart
Authors: PINTO JUDITH M.B. , BOYDEN PENELOPE A. 
Published: April 2007

Outward Currents in Purkinje Cells from 48‐Hour Infarcted Heart. Introduction: Subendocardial Purkinje myocytes from the 4K‐hour infarcted heart (IZPCs) have reduced resting potentials, possibly due to altered inwardly rectifying K+ currents IKI. Abnormal depolarization‐activated outward K+ currents could contribute to long triangularly shaped action potentials of IZPCs. Methods and Results: We used whole cell patch recordings to compare cesium‐sensitive IKI and 4‐aminopyridine (4‐AP)‐resistant, noninactivating sustained IK between normal Purkinje myocytes (NZPCs) and IZPCs. IZPCs showed decreased net membrane currents. Two IZPC groups were distinguished, based on 4‐AP‐resistant outward K+ currents. IZPC‐I had isochronal IKI current‐voltage relations similar to NZPCs whereas IZPC‐II showed significantly reduced IKI and increased outward plateau currents. To study the sustained IK in the presence of the Class III antiarrhythmic agent E‐4031, a two‐pulse protocol was used to inactivate transient outward currents, followed by step depolarizations. E‐4031‐sensitive currents were significantly greater in IZPCs at depolarized potentials (> 0 mV). Similar to NZPCs, IZPC E‐4031 currents showed time dependence during depolarization, lack of rectification at positive steps, and voltage‐dependent recovery from block. Conclusion: Decreased IKI may account for reduced resting potentials in IZPCs. E‐4031‐sensitive currents in NZPCs, unlike those in canine ventricular myocytes, are sensitive to 4‐AP and are larger in IZPCs.
Lidocaine's Effect on Defibrillation Threshold are Dependent on the Defibrillation Electrode System: Epicardial Versus Endocardial
Authors: MILLER ALLISON P. WINECOFF , SIMS J. JASON , McSWAIN ROBERT , UJHELYI MICHAEL R. 
Published: April 2007

Lidocaine's Effect on Defibrillation Depends on Lead System. Introduction: Epicardial and endocardial defibrillation electrode systems affect myocardial electrophysiology and sympathetic function differently. Thus, we postulate that antiarrhythmic drugs will interact with these electrode systems differently. Methods and Results: Defibrillation energy requirements (DER) at 20% (ED20), 50% (ED50), and 80% (ED80), success were measured at baseline and during lidocaine (10 mg/kg per hour) or D5W treatment for epicardial and endocardial electrodes. Pigs were randomized to treatment (lidocaine or D5W) and electrode system, which resulted in four experimental groups: (1) epicardial electrode + D5W; (2) epicardial electrode + lidocaine; (3) endocardial electrode + D5W; and (4) endocardial electrode + lidocaine. ED50 DER (mean ± SEM) values at baseline for groups 1–4 were 10.6 ± 1, 8.5 ± 1, 12.6 ± 1, and 12.3 ± 1 J, respectively. DER values for groups 1 and 3 during D5W were similar to baseline. Conversely, lidocaine increased ED50 DER values from 8.5 ± 1 to 13.5 ± 2 J (P < 0.05) in group 2 animals (epicardial electrodes). When lidocaine was administered to group 4 animals (endocardial electrodes), however, ED50 DER values remained similar to baseline values (12.3 ± 1 to 14.3 ± 2 J, P = NS). Lidocaine increased ED50 DER values by 59% with the epicardial electrode system, which was significantly greater than the 16% increase with the endocardial electrode system (P < 0.05). Electrophysiologic response and electrode impedance were similar between electrode systems. Conclusion: Lidocaine increases DER values to a greater extent when using epicardial versus endocardial electrode system. Thus, drug‐device interactions are dependent on the electrode system. These data suggest that the electrophysiologic milieu created by endocardial defibrillation mitigates the effects that lidocaine has on DER values.
Syncytial Heterogeneity as a Mechanism Underlying Cardiac Far‐Field Stimulation During Defibrillation‐Level Shocks
Authors: FISHLER MATTHEW G. 
Published: April 2007

Far‐Field Stimulation via Syncytial Heterogeneities. Introduction: The mechanisms by which a defibrillation shock directly stimulates regions of cardiac tissue distal to the stimulus electrodes (“far‐field” stimulation) are still not well understood. Existing hypotheses have proposed that intercellular discontinuities and/or fiber curvatures induce the requisite membrane polarizations. This article hypothesizes a third potential mechanism: one based on the existence and influences of syncytial (anatomic) heterogeneities inherent throughout the bulk myocardium itself. Methods and Results: We simulated the effects of such heterogeneities in a model of a two‐dimensional region of passive cardiac tissue subjected to uniform 1 V/cm longitudinal or transverse field stimuli. Heterogeneities were manifested via random spatial variations of intracellular volume fractions (fi) over multiple length scales, with mean of 80% and standard deviation ofi (σfi) ranging from 0% to 10%. During field stimulation, many interspersed and variously shaped and sized islands of hyperpolarization and depolarization developed across the tissue, with their locations and extents correlated to the spatial gradients of the underlying heterogeneities. Increases in σfi correspondingly increased the shock‐induced magnitudes of resulting membrane polarizations. The ratio of maximal polarizations for equivalent longitudinal and transverse shocks approximated 2:1 across all σfi tested. At σfi= 5%, these maximal induced polarizations were 17.4 ± 2.4 mV and 8.18 ± 1.5 mV, respectively. Assuming an excitation threshold of 25 mV, these data suggest corresponding diastolic thresholds of 1.47 ± 0.20 V/cm and 3.14 ± 0.50 V/cm, respectively. Conclusion: This study predicts that syncytial heterogeneities inherent within cardiac tissue could represent a significant—and heretofore unappreciated—mechanism underlying field‐induced polarizations throughout the bulk myocardium.
Temperature‐Controlled Irrigated Tip Radiofrequency Catheter Ablation:
Authors: PETERSEN HELEN HØGH , CHEN XU , PIETERSEN ADRIAN , SVENDSEN JESPER HASTRUP , HAUNSØ STIG 
Published: April 2007

Temperature‐Controlled Irrigated Tip Ablation. Introduction: In patients with ventricular tachycardias due to structural heart disease, catheter ablation cures < 60% partly due to the limited lesion size after conventional radiofrequency ablation. Irrigated tip radiofrequency ablation using power control and high infusion rates enlarges lesion size, hut has increased risk of cratering. The present study explores irrigated tip catheter ablation in temperature‐ controlled mode, target temperature 60°C, using an irrigation rate of 1 mL/min, comparing this to conventional catheter technique, target temperature 80°C. Methods and Results: In vivo anesthetized pigs were ablated in the left ventricle. In vitro strips of porcine left ventricular myocardium were ablated in a tissue bath. Lesion volume was significantly larger after irrigated tip ablation both in vivo (544 ± 218 vs 325 ± 194 mm3, P < 0.01) and in vitro (286 ± 113 vs 179 ± 23 mm3, P < 0.01). The incidence of cratering was not significantly different between the two groups. In vivo, no coagulum formation on part of the catheter tip was seen after irrigated tip ablation as opposed to 52% of the applications with conventional ablation (P < 0.05). Conclusion: We conclude that temperature‐controlled radiofrequency ablation with irrigated tip catheters using low target temperature and low infusion rate enlarges lesion size without increasing the incidence of cratering and reduces coagulum formation of the tip.
Susceptibility to Atrial Fibrillation:
Authors: POWER JOHN M. , BEACOM GRAHAM A. , ALEERNESS CUE A. , RAMAN JAI , WUEEELS MAURITS , EARISH STEPHEN J. , BURRELL LOUISE M. , TONKIN ANDREW M. 
Published: April 2007

Propensity for Extrastimulus to Induce AF. Introduction: The development of susceptibility to atrial fibrillation (AF) is a common consequence of many forms of cardiovascular disease, especially heart failure. In this study we used a sheep model of pacing‐induced stable early heart failure to describe, quantify, and relate the level of susceptibility to AF to changes in structural and electrophysiologic parameters. Methods and Results: Epicardial electrodes were implanted on the atria and right ventricles of nine sheep. The AF thresbold, atrial vulnerability period, atrial effective refractory period (ERP), and interatrial conduction time were examined during control and over a 6‐week period of ventricular pacing at 190 beats/min. Left atrial (LA) area and left ventricular (LV) fractional shortening were monitored using echocardiography. There were significant increases in LA susceptibility to AF (P < 0.0003), LA area (P < 0.0002), and LA FRP400 (P < 0.0002). Rate of increase in LA area was related positively to AF susceptibility (P = 0.02) and inversely to LA ERP400 (P = 0.002). LV fractional shortening decreased to approximately 50% of control value (P < 0.00001). No changes were observed in right atrial electrophysiology. Conclusion: In this study, susceptibility (the ability of an extrastimulus to induce AF) was rigorously measured within a predetermined format. Significant relationships were found to exist between susceptibility, certain of the observed changes in atrial electrophysiology and structure.
Preserved Autonomic Modulation of the Sinus and Atrioventricular Nodes Following Posteroseptal Ablation for Treatment of Atrioventricular Nodal Reentrant Tachycardia
Authors: KOWALLIK PETER , ESCHER SILKE , PETERS WERNER , BRAUN CHRISTIAN , MEESMANN MALTE 
Published: April 2007

Autonomic Control of the AV Node. Introduction: Following radiofrequency catheter ablation of AV nodal reentrant tachycardia (AVNRT), inappropriate sinus tachycardia may occur, possibly due to damage to autonomic cardiac nerve fibers. Furthermore, inducibility of AVNRT is often critically dependent on the autonomic balance. We investigated whether successful ablation of AVNRT is associated with an alteration of autonomic input to the sinus and AV nodes. Methods and Results: To estimate changes in the automatic modulation of the sinus and AV nodes, power spectra of beat‐to‐beat PP and PR intervals were analyzed from high‐quality nighttime ECG recordings of 11 patients before and after radiofrequency application. Normalized HF power (nHF) of PP and PR intervals was used as an index of efferent vagal modulation and the LF/HF ratio as an index of sympathovagal balance of the sinus node (PP) and AV node (PR). Before ablation, LF/HFPP was 3.2 and nHFPP was 0.3 in the sinus node, For the A/V node, LF/HFPR was 1.2 and nHFPR was 0.5. Following ablation. LF/HFPP (3.5) and nHFPP (0.3) of the PP intervals did not change. Similarly to the sinus node, there were no changes in the autonomic modulation of the AV node, as both LF/HFPR (1.2) and nHFPR (0.5) remained unchanged. Conclusion: Our results indicate that autonomic control of the sinus und AV nodes is preserved following successful radiofrequency ablation of AVNRT. The effects of posteroseptal radiofrequency current application are not necessarily mediated by changes in the autonomic input to the AV node.