bluuebunny/crossref_metadata_2025 huggingface dataset:
Evolution of the class III HD‐Zip gene family in land plants
Authors: Prigge Michael J. , Clark Steven E.
Published: June 2006

SUMMARY
Arabidopsis class III homeodomain‐leucine zipper (HD‐Zip III) proteins play overlapping, distinct, and antagonistic roles in key aspects of development that have evolved during land plant evolution. To better understand this gene family's role in plant evolution and development as well as to address broader questions of how duplicated genes functionally diversify, we investigated the evolutionary history of this gene family. Phylogenetic analyses including homologs from diverse land plants indicate that a gene duplication event before the angiosperm‐‐gymnosperm split gave rise to two gene lineages that diversified during angiosperm plant radiation. Heterologous expression of an HD‐Zip III gene from the nonvascular plant moss within the Arabidopsis HD‐zip III revoluta mutant modified but did not complement the phenotype. Comparison of the expression domains of flowering and nonflowering plant homologs indicate an ancestral role in vascular development and organ initiation but not in specifying organ polarity, a prominent role for angiosperm homologs.
Molecular evolution of fibrillar collagen in chordates, with implications for the evolution of vertebrate skeletons and chordate phylogeny
Authors: Wada Hiroshi , Okuyama Makiko , Satoh Nori , Zhang Shicui
Published: June 2006

SUMMARY
Vertebrates have seven types of fibrillar collagens that are encoded by 11 genes. Types I, V, and XXIV collagens are components of mineralized bone, whereas types II, XI, and XXVII collagens are components of cartilage. In this study, we traced the molecular evolutionary history of chordate collagen genes and examined how gene duplications gave rise to the collagen genes used for skeletons. Our analyses of deuterostome collagen genes, including one amphioxus gene that we identified in this study, suggest that the common ancestors of deuterostomes possessed three fibrillar collagen genes. Expression analyses of chordate fibrillar collagen genes suggest that in the ancestors of chordates, fibrillar collagen was co‐opted to the formation of the notochord sheath independently in three clades. Our results also imply that co‐option of collagen genes to cartilage occurred in clade A (col2A1), clade B (col11A1, 11A2), and clade C (COL27A1). Similarly, some fibrillar collagen genes have been co‐opted for mineralized bone independently from clade A genes (col1A1, 1A2, 5A2), clade B genes (col5A1), and clade C genes (COL24A1). These frequent co‐options for notochord, cartilage, and mineralized bone must have been accompanied by the rapid evolution of cis‐regulatory elements for transcription. In addition, we found that one of the ascidian fibrillar collagen genes possesses an amino acid insertion at the identical site of the C‐terminal noncollagenous domain in vertebrate fibrillar collagen genes. This observation raises a suspicion about the relatively well‐accepted phylogeny of the close relationship between amphioxus and vertebrates.
The First Year Experience with the Dual Chamber ICD
Authors: HIGGINS STEVEN L. , PAK JONATHAN P. , BARONE JULIE , WILLIAMS SETH K. , BOLLINGER FLORENCE M. , WHITING SHERIE L. , MEYER DAVID B.
Published: June 2006

In July 1997, a dual chamber pacemaker combined with a tiered therapy implantable cardioverter defibrillator (ICD) first became available in the United States. We report the first‐year experience of one center in the United States with this dual chamber ICD. Of a total of 174 ICDs, 95 (55%) were dual chamber devices and 79 (45%) were single chamber. New dual chamber ICD insertions averaged 57.4 ± 8.9 minutes, though there was a learning curve as the last 30 implants averaged 45.1 ± 6.1 minutes with a negative slope to the regression line of procedure duration (−0.52, P < 0.05). New single chamber ICD implants were 18.5 minutes quicker (38.9 ± 7.2 minutes). The most challenging implants were dual chamber upgrades (mean procedure duration 64.9 ± 15.8 minutes), especially if there was a previously implanted pacemaker and ICD at separate sites. Indications for a new dual chamber device were grouped into classic pacemaker indications (52.5%), which comprised the Class I ACC/AHA guidelines, ICD‐specific indications (24.6%), and other (23.0%). In the 34 patients undergoing dual chamber upgrade, the classic and ICD‐specific groups were equal (47.0% each). Complications were rare (2.8%), though 3 (8.8%) of 34 undergoing a dual chamber upgrade developed late infections requiring explanation. In its first year, the dual chamber ICD has become a common device at our institution comprising 55% of new implants. As experience grows, we anticipate similar usage at most institutions.
Importance of Ventricular Rate After Mode Switching During Low Intensity Exercise as Assessed by Clinical Symptoms and Ventilatory Gas Exchange
Authors: ROCCA HANS PETER BRUNNER‐LA , RICKLI HANS , WEILENMANN DANIEL , DURU FIRAT , CANDINAS RETO
Published: June 2006

Automatic mode switching from DDD(R) to DDI(R) or VV1(R) pacing modes has improved dual chamber pacing in patients at high risk for supraventricular tachyarrhythmias. However, little is known about the effect of ventricular pacing rate adaptation after mode switching. We conducted a single‐blinded, crossover study in 15 patients (58 ± 21 years) with a DDD pacemaker who had AV block and normal sinus node function to investigate the influence of pacing rate adaptation to intrinsic heart rate during low intensity exercise. Patients performed two tests (A/B) of low intensity treadmill exercise (0.5 W/kg) in randomized order. They initially walked for 6 minutes while paced in DDD mode. The pacing mode was then switched to VVI with a pacing rate of either 70 beats/min (test A) or matched to the intrinsic heart rate (95 ± 11 beats/min test B). Respiratory gas exchange variables were determined and patients classified the effort before and after mode switching on a Borg scale from 6 to 20. Percentage changes of respiratory gas exchange measurements were significantly larger (Oz consumption: −8.2 ± 5.0% vs. −0.6 ± 7.2%; Ventilatory equivalent of CO2 exhalation: 5.3 ± 4.9% vs. 1.5 ± 4.3%; respiratory exchange ratio: 7.0 ± 2.2% vs 3.5 ± 3.0%; end‐tidal CO2: −5.7 ± 2.9% vs. −1.8 ± 2.7%; all P < 0.01) and the increase in subjective assessment of the effort tended to be higher (mean increase on Borg scale: 1.6 ± 1.9 vs. 1.1 ± 1.8, P = 0.07) after heart rate unadjusted than after adjusted mode switching. Mode switching from ODD to WI pacing is better tolerated and gas exchange measurements are less influenced if ventricular pacing rate is adjusted to the level of physical activity. Thus, pacing rate adjustment should be considered as part of automatic mode switch algorithms.
Impact of Transisthmus Linear Ablation of Typical Atrial Flutter on Coronary Sinus Activation Time
Authors: TSAI CHIN‐FENG , CHEN SHIH‐ANN , TAI CHING‐TAI , CHIANG CHERN‐EN , YU WEN‐CHUNG , CHEN YI‐JEN , FENG AN‐NING , HSIEH MING‐HSIUNG , DING YU‐AN , CHANG MAD‐SONG
Published: June 2006

Complete or incomplete bidirectional isthmus conduction block after linear ablation of atrial flutter is difficult to interpret without detailed multiple electrodes mapping along the tricuspid an‐nulus and the low right atrial isthmus area. The influence of isthmus block on the intraatrial septal and coronary sinus activation has not been assessed by endocardial mapping. This study was designed to analyze the intraartial and interatrial activation times in a retrospective fashion to investigate (1) whether isthmus conduction block can change the coronary sinus activation sequence during low lateral right atrial pacing, and (2) the correlation between change of coronary sinus activation time and isthmus conduction block. Sixty‐five consecutive patients (mean age, 57 ± 18 years) with clinically documented typical atrial flutter were studied. A 20‐pole “Halo” catheter was placed around the tricuspid annulus including the entire low right atrial isthmus to verify complete bidirectional isthmus block. Activation time from ostium to distal coronary sinus (OCS→DCS), and interatrial septum and isthmus activation times during right atrial pacing were analyzed and compared before and after incomplete or complete isthmus block. Complete bidirectional isthmus block was achieved in 50 (77%) patients. During low lateral right atrial pacing, linear ablation at low right atrial isthmus results in a significant delay of activation in all coronary sinus recording sites with greater extent at the ostium area without influence on interatrial septum activation in complete and incomplete isthmus conduction block. The difference of the OCS→DCS interval before and after ablation, Δ (OCS→DCS), was well correlated with results of isthmus conduction block and significantly longer in patients with complete than those with incomplete isthmus block (34 ± 11 vs 11 ± 8 ms, P < 0.001), thereby allowing a value of 20 ms as a discriminative parameter to differentiate incomplete (<20 ms) from complete (< 20 ms) isthmus counterclockwise conduction block with a sensitivity of 96% and a specificity of 88%. In conclusion, creation of a line of block at the inferior vena cava‐tricuspid annulus isthmus could change coronary sinus activation sequence during low lateral right atrial pacing in sinus rhythm. The change of coronary sinus activation time after linear ablation, Δ (OCS→DCS), was well correlated with isthmus conduction block by using a value ≥ 20 ms to discern complete counterclockwise isthmus block.
Radiofrequency Ablation of a Posteroseptal Atrioventricular Accessory Pathway in a Left‐Sided Tricuspid Ring with Ebsteinlike Anomaly in a Patient with Congenitally Corrected Transposition of the Great Arteries
Authors: BRUGADA JOSEF , VALLS VALENTÍ , FREIXA ROMAN , GONZALEZ EVA , HERREROS BENITO , MATAS MARIONA , MONT LLUÍS
Published: June 2006

Radiofrequency ablation successfully eliminated a posteroseptal accessory pathway in a left‐sided tricuspid ring with Ebsteinlike anomaly in a patient with a congenially corrected transposition of the great arteries.
Successful Treatment of Severe Orthostatic Hypotension with Cardiac Tachypacing in Dual Chamber Pacemakers
Authors: ABE HARUHIKO , NUMATA TETSUYA , HANADA HIDEYUKI , KOHSHI KIYOTAKA , NAKASHIMA YASUHIDE
Published: June 2006

Orthostatic hypotension is an evolving and disabling disease usually observed in elderly patients with dramatic consequences on morbidity, mortality, and impairing the quality of life. We studied the effects of the pacing rate and AV interval on the blood pressure drop in the upright position in two patients with previously implanted pacemakers for sinus node dysfunction. Although the AV interval did not affect the blood pressure drop in the upright position, tachypacing at 100 paces/min improved it dramatically and prevented syncope. Cardiac tachypacing is a useful therapeutic option in severe refractory Orthostatic hypotensive patients, especially those with chronotropic incompetence.
Permanent Explantation of Implantable Cardioverter Defibrillators
Authors: GEIST MICHAEL , NEWMAN DAVID , GREENE MARY , PAQUETTE MINEY , DORIAN PAUL
Published: June 2006

Although ICD therapy is seen as an irrevocable mode of therapy in most patients, a small number of patients do have their devices permanently explanted. The long‐term outcome in these patients has not been described. The purpose of this single center study was to evaluate the long‐term outcome of patients whose ICD was ex‐planted and not replaced and to propose clinical variables that can be considered when making the decision to discontinue therapy. Ten of 323 (3.1%) patients in our ICD registry had their devices permanently explanted or turned off between 1986 and December 1998. The devices had been in place for 39 ± 31 months preexplant. No patient had received appropriate therapy prior to surgery, which was indicated for infection or lead fracture. All patients are alive and well 75 ± 30 months postexplant with 1 (10%) patient requiring late reimplantation. We reviewed the English language literature describing ICD explanation without replacement. A total of 151 patients were reported in eight studies and were followed for up to 30 months postexplant. Excluding patients with terminal illness or heart transplantation 57.6% survived without reimplantation. In selected patients, after not using an ICD for a long period and when clinical circumstances justify, device therapy may be discontinued with some degree of safety.
Autonomic Nervous System Activity Before and During Episodes of Myocardial Ischemia in Patients with Stable Coronary Artery Disease During Daily Life
Authors: KOCHIADAKIS GEORGE E. , MARKETOU MARIA E. , IGOUMENIDIS NIKOS E. , SIMANTIRAKIS EMMANUEL N. , PARTHENAKIS FRAGISKOS I. , MANIOS EMMANUEL G. , VARDAS PANOS E.
Published: June 2006

Spectral analysis of heart rate variability (HR V) was used to assess changes in the autonomic nervous system (ANS) 10 minutes before, during, and 10 minutes after 110 ischemic episodes (IEs) in 38 patients (25 men, age 61 ± 10 years) with stable coronary artery disease. In 26 of 77 diurnal IEs (07:00–22:59) there were no changes in the spectral indexes (LF and HF) during the study period. In the remainder there was an increase in the LF:HF ratio due to HF withdrawal that started before the onset of the IE. AII 33 nocturnal episodes also showed an increase in the LF:HF ratio, which was due not only to HF withdrawal, but also to a simultaneous increase in LF. Although it is not the only cause, the ANS plays a significant role in triggering IEs during daily life in patients with stable coronary artery disease. The common factor in all such episodes is a gradual withdrawal of parasympathetic tone.
Characteristics and Results of Epicardial Pacing in Neonates and Infants
Authors: VILLAIN E. , MARTELLI H. , BONNET D. , ISERIN L. , BUTERA G. , KACHANER J.
Published: June 2006

The results of epicardial pacing in infants with isolated congenital complete atrioventricular block (CAVB) are reported. Thirty‐four patients, aged 1 day to 20 months (22 patients < 1 month), were paced between 1988 and 1998. Thirty had bradycardia < 50 beats/min with symptoms in 12 patients, and 4 patients were paced because of associated ventricular ectopy or prolonged QT interval. In thirty cases, the electrodes were implanted through a left thoracotomy and connected to an abdominal generator; in four, the sub‐xyphoid approach was preferred. Twenty‐two children had dual chamber units. There was no operative death, but three patients died later of cardiomyopathy. Seven infants were reoperated for electrode displacement, infection, exit block, and pacemaker sensitivity. Chronic ventricular thresholds ranged from 0.3 to 2 V except in one case (4 V) and proper atrial sensing was lost in two cases. All children are doing well and the generator has lasted at least 5 years in 16 cases. In conclusion, epicardial pacing in infants with CAVB can be done with satisfactory results. There was no mortality in relation with pacing and thresholds have improved with the use of steroid‐eluting electrodes. The deep location of the generator prevents cutaneous erosion and allows implantation of large units with a longer life duration.
Diagnosis and Ablation of Atrial Flutter Using a High Resolution, Noncontact Mapping System
Authors: SCHMITT HEIKO , WEBER STEFAN , TILLMANNS HARALD , WALDECKER BERND
Published: June 2006

The ablation of atrial flutter can sometimes be time consuming and unsuccessful using conventional catheter techniques especially in patients with recurrences after previous ablation procedures. Simultaneous high resolution mapping from multiple sites may overcome some of the limitations. Therefore, a new high resolution noncontact mapping system was used for diagnosis and ablation of atrial flutter in 15 patients. The mapping system consists of a catheter‐mounted multielectrode array, an amplifier, and a computer workstation. Far‐field potentials recorded by the multielectrode catheter are amplified, digitized, and sampled at 1.2 kHz, and digitally filtered to construct high resolution activation maps during tachycardia. Ablation catheters can be steered to target sites without fluoroscopy. In 12 of the 15 patients the analysis of the activation sequence during tachycardia showed a counter‐clockwise, and in 1 of 15 patients a clockwise, rotating wavefront using the isthmus as part of the reentrant circuit. In two patients no tachycardia could be induced. In 12 of the 15 patients with previous conventional ablation procedures the gap in the line of block in the isthmus region was identified and marked on the animation model. The isthmus in the right atrium was ablated and isthmus block verified by the mapping system in all patients. No complications were observed. No recurrences of atrial flutter occurred during follow‐up of 4 ± 1,7 months. The total procedure and fluoroscopy time was 171 ± 50.0 minutes and 24 ± 12.7 minutes, respectively. In conclusion, the use of the new high resolution noncontact mapping system in patients with right atrial flutter is safe and highly effective. In patients with previously failed conventional ablation procedures the use of a noncontact mapping system may facilitate the identification of the gap in the line of block in the isthmus region and reablation of atrial flutter.
Passive‐Fixation J‐Shaped Versus Straight Leads in Atrial Position: Comparison of Efficacy and Safety
Authors: KRUPIENICZ ANDRZEJ , KARCZMAREWICZ STEFAN , MARCINIAK WOJCIECH , GNILKA ANNA , KULAKOWSKI PIOTR , ADAMUS JERZY
Published: June 2006

To compare the efficacy and safety of straight and J‐shaped passive‐fixation atrial leads we retrospectively analyzed the results of 100 consecutive implantations of atrial leads at one institution. There were seven cases of upgrades of VVIR to DDDR systems and in one case an active‐fixation lead was chosen as a primary approach. These eight patients were excluded from the analysis. The final study group consisted of 92 cases (69 DDDR, 23 AAIR), 69 were J and 23 straight leads. The stimulation threshold, slew rate, impedance, P wave amplitude, and procedural time did not differ significantly between the two types of leads used. During the long‐term follow‐up of 6–53 months (30 ± 11,9 months), replacements using active‐fixation leads were required in two patients with straight leads and three patients with J leads (P = NS). In addition, one J lead showed signs of damage (impedance > 3,000 Ohm) Long‐term follow‐up values of the stimulation thresholds and P wave amplitudes did not differ between the groups (P = NS). Transesophageal echocardiography performed in 13 patients revealed a trend toward more distal placement of straight leads within the right atrial appendage. In conclusion, J‐shaped leads do not seem to be superior to the straight leads for atrial implantations.
Initial Low Temperature Setting in Radiofrequency Catheter Ablation of Wolff‐Parkinson‐White Syndrome
Authors: VEGA‐ARRILLAGA FRANCES , YOUNG MING‐LON , WU JING‐MING , WOLFF GRACE S.
Published: June 2006

Previous studies have shown that with low temperature testing for RF ablation of arrhythmias, unnecessary irreversible myocardial lesions may be avoided. In children admitted/or RF ablation from June 1996 to May 1999, we evaluated the method of an initial temperature setting of 50°C for a maximum of 10 seconds. If accessory pathway block occurred, the temperature setting was immediately increased to 70°C and continued for 45–120 seconds (group 1). If accessory pathway block did not occur after several attempts, subsequent attempts were made with initial settings at 70°C–80°C at the same or different sites (group 2). Eighty patients with Wolff‐Parkinson‐White syndrome (mean age 11 ± 4 years) were treated using this method. Twelve patients were excluded for various reasons. Of the remaining 68 patients, 52 (76%) had successful block of the pathway at 50°C; 16 patients demonstrated block only at the higher temperature setting of 70°C–80°C. There were no statistically significant differences between these two groups in terms of age, weight, and location of accessory pathways. Unsuccessful 50°C test ablation attempts were 1.6 ± 2.4 in group 1 and 3.1 ± 2.9 in group 2 (P = 0.04). Total unsuccessful attempts were 1.6 ± 2.4 in group 1 and 8.1 ± 7.1 in group 2 (P = 0.001). The time from application of RF energy to the time of AP block in group 1 was not significantly different from group 2. In the majority of children, successful RF ablation can be achieved by using a temperature setting of 50°C, then 70°C. This will prevent unnecessary permanent injury at unsuccessful attempt sites.
Inferior Vena Cava Loop of the Implantable Cardioverter Defibrillator Endocardial Lead: A Possible Solution to the Growth Problem in Pediatric Implantation
Authors: GASPARINI MAURIZIO , MANTICA MASSIMO , GALIMBERTI PAOLA , COLTORTI FERNANDO , CERIOTTI CARLO , PRIORI SILVIA G.
Published: June 2006

The ICD is an important treatment option in adults and children with life‐threatening tachyarrhvthmias. The possibility of lead displacement caused by growth and the lack of dedicated leads cind devices poses special problems in pediatric ICD implantation. We describe our experience in three children in whom we left a redundant lead loop within the inferior vena cava (IVC) to allow for further growth. Since February 1998, three children underwent ICD implantation at our institution. A had (screw‐in) was advanced into the right ventricular apex, and a loop was created in the IVC by progressively withdrawing the stylet and pushing in the lead. Satisfactory sensing and pacing threshold values were obtained and a successful single 16‐J de‐fibrillation test was performed. No complications were encountered. After a mean follow‐up of 16 months, with a mean increase in body weight and height of 4.1 ± 0.5 Kg and 6.3 ± 0.4 cm, respectively, chest X ray showed some release of additional lead length, in the absence of dislodgments, while significant changes in pacing/sensing parameters were not found. In conclusion, the creation of a loop within the IVC allows the lead to adjust for growth in children receiving an ICD. This approach is feasible and safe.
Automated Classification of Human Atrial Fibrillation From Intraatrial Electrograms
Authors: BARBARO VINCENZO , BARTOLINI PIETRO , CALCAGNINI GIOVANNI , MORELLI SANDRA , MICHELUCCI ANTONIO , GENSINI GIANFRANCO
Published: June 2006

The assessment of the degree of organization and the classification of atrial fibrillation (AF) according to the types defined by Wells usually resorts to the visual inspection of bipolar intraatrial electro‐grams. The focus of this study was to test, seven parameters aimed to quantify the degree of organization of the electrograms, and then to design a final classification scheme based on a multidimensional, minimum‐distance analysis. The following parameters were tested: mean atrial period (AP) and its coefficient of variation (CV); number of points lying at the baseline (NO) and the Shannon entropy (EN) of the amplitude probability density function (APDF); depolarization width (F‐WIDTH); and correlation waveform analysis (CWA) and electrogram bandwidth (BW). The signal database consisted in a set of 160 AF strips of Type I, II, and HI AF, scored by an expert cardiologist (60 Type I, 40 Type II, 60 Type III) and further divided in a training set (60) and a test set (100). Strips were 6 seconds long and were recorded with 5‐mm interspace bipolar catheters from electrically induced (n = 13) and chronic (n = 10) patients. A classification algorithm based on a minimum‐distance (Mahalanobis distance) discriminant analysis was tested. Using a single parameter, the best discriminations were provided by NO, F‐WIDTH, and CV. F‐WIDTH was found strongly inversely correlated to NO (r =−0.90). Of all the two‐parameter combinations, CV‐NO provided the best classification: 92 of WO segments were correctly classified with sensitivity > 90% and specificity > 92%. A further improvement was obtained by including BW as a third parameter (93/100 correctly classified). The use of more than three parameters not only failed to improve, but even degraded the classification.
Prospective Comparison of Lesions Created Using a Multipolar Microcatheter Ablation System with Those Created Using a Fullback Approach with Standard Radiofrequency Ablation in the Canine Atrium
Authors: JUMRUSSIRIKUL PITAYADET , ATIGA WALTER L. , LARDO ALBERT C. , BERGER RONALD D. , HALPERIN HENRY , HUTCHINS GROVER M. , CALKINS HUGH
Published: June 2006

The aim of this study was to compare the lesions created using a multi‐polar microcatheter (MICRO) ablation system in the right canine atrium to a pullback approach with a standard radiofrequency (STND RF) ablation and to determine the value of electrogram amplitude and pacing threshold in predicting transmurality of lesions. Ten dogs underwent right atrial ablation using a MICRO (6 dogs) or STND RF (4 dogs) ablation system in each animal. Attempts were made to create linear RF lesions at four predetermined atrial sites. RF energy was delivered for 60 seconds using closed‐loop temperature control to achieve a target temperature of 60°C for STND RF and 50°C for MICRO. Unipolar atrial electrogram amplitude and atrial pacing threshold were obtained before and after ablation. Pathological analysis was determined at 4 weeks after ablation. Lesions created with MICRO were narrower, more likely to be continuous, and more likely to be anchored to an anatomic structure than those lesions which were created using a STND RF. No difference was observed in overall lesion length or in the proportion of lesions that were transmural over at least 50% of their length. Of lesions created using MICRO, a significant relation was observed between transmurality of lesion and unipolar electrogram amplitude as well as pacing threshold. Further studies are needed to determine if this type of ablation technique and parameters during ablation may facilitate a successful catheter‐based MAZE procedure.
Catheter Ablation Approach on the Right Side Only for Paroxysmal Atrial Fibrillation Therapy: Long‐Term Results
Authors: NATALE ANDREA , LEONELLI FABIO , BEHEIRY SALWA , NEWBY KEITH , PISANO ENNIO , POTENZA DOMENICO , RAJKOVICH KATHLEEN , WIDES BRANDON , CROMWELL LISA , TOMASSONI† GERY
Published: June 2006

We report the long‐term follow‐up of a right side only catheter ablation approach for paroxysmal AF. Eighteen patients with AF refractory to drugs entered the study. Ablation was attempted in the right atrium only by creating linear lesions based on a specific design including from two to four linear lesions. Induction of AF was attempted before ablation and after placement of the lesions. A septal lesion was performed in nine patients. In ten patients atrial defibrillation thresholds (ADFTs) before ablation and following creation of the linear lesions were compared. After a mean follow‐up of 22±11 months, seven patients had recurrence of AF, and another nine patients experienced atria flutter or atrial tachycardia. Five patients remained in sinus rhythm without medications and four required the use of drugs. Three patients had sporadic AF and six were in chronic AF. The recurrence rate was similar in patients with and without the septal lesion. However, a cure with right side ablation appeared to be predicted by the presence of disorganized and earlier activity in the high right atrium and crista terminalis. Linear lesions in the right atrium were associated with a lower ADFT (pre 2.6 ± 04 J vs post 1.7 ± 0.6 J). In conclusion, in a small number of patients, control of AF can be obtained with a right side only approach. Certain activation patterns may identify patients suitable to this approach. No specific lesion pattern appeared more effective. Eight atrial linear lesions resulted in lower ADFT.
Signal‐Averaged P Wave Duration Predicts Early Recurrence of Atrial Fibrillation After Cardioversion
Authors: RAITT MERRITT H. , INGRAM KENNETH D. , THURMAN S. MICHAEL
Published: June 2006

Thirty‐two patients had signal‐averaged P wave duration measured after electrical cardioversion of AF, and were followed for 1 year or until there was a recurrence. The use of antiarrhyth‐mic medications was left to the discretion of the attending physician. Among 20 patients not taking an‐tiarrhythmic medication, the 11 patients who had a recurrence of AF within 3 months of cardioversion had a significantly longer signal‐averaged P wave duration compared to the 9 patients who did not (148 ± 17 vs 135 ± 20 ms, P = 0.005). There was no difference, in clinical parameters or left atrial diameter. A signal‐averaged P wave duration cutoff anywhere between 130 and 135 ms correctly classified 85% of patients with a sensitivity of 81 % and a specificity of 89%, In patients taking antiarrhythmic medications, signal‐averaged P wave duration did not correlate with the risk of recurrence. In patients not taking antiarrhythmic medications, signal‐averaged P wave duration can be used to predict the risk of an early recurrence of AF after cardioversion. The poor predictive value in patients taking antiarrhythmics may be due to changes in the atrial refractory period, which are not reflected in P wave duration.
Basket Catheter Localization of the Origin of Atrial Tachycardia with Atypical Morphology After Atrial Flutter Ablation
Authors: RODRIGUEZ ENRIQUE , CALLANS DAVID , KANTHARIA BHARAT , GOTTLIEB CHARLES , MARCHLINSKI FRANCIS E.
Published: June 2006

Atrial activation from a site in the low lateral right atrium will typically proceed in a superior direction. We present a case of a low lateral right atrial tachycardia with a surface electrocardiographic P wave morphology that appeared to have an inferiorly directed axis. The tachycardia occurred 2 years after successful atrial flutter ablation. The use of a multipolar basket catheter allowed confirmation of the focal origin of the tachycardia, permitted its rapid localization, facilitated catheter ablation, and provided clues to atrial activation that helped describe the appearance of the P wave.
Orthodromic Tachycardia with Atrioventricular Dissociation: Evidence for a Nodoventricular (Mahaim) Fiber
Authors: MANTOVAN ROBERTO , VERLATO ROBERTO , CORRADO DOMENICO , BUIA GIANFRANCO , HAISSAGUERRE MICHEL , SHAH DIPEN C.
Published: June 2006

We describe a patient in whom two tachycardias with AV dissociation were inducihle by ventricular extrastimulation. The first tachycardia was characterized by a narrow QRS preceded by a His deflection with an HV interval identical to that recorded in sinus rhythm (40 ms). Premature ventricular depolarization delivered when the His bundle was refractory advanced the next His deflection. These findings suggest the presence, of a nodoventricular bypass tract involved in an orthodromic tachycardia. The second tachycardia was induced after propafenone infusion and exhibited a wide QRS complex with left bundle branch block morphology; each ventricular complex was consistently associated with a His deflection with a HV interval of −15 ms. The second tachycardia may be considered to represent an antidromic tachycardia through the nodoventricular tract. However, a ventricular tachycardia cannot be excluded.
Late Onset of Accessory Pathway Conduction in a Patient with Complete AV Block
Authors: ERICKSON CHRISTOPHER C. , YETMAN ANJI T. , JONES CONNIE S. , DUNGAN W. THOMPSON
Published: June 2006

This case report discusses a patient with complete AV block in early childhood. The patient required a permanent pacemaker. At 6 years of age, intermittent preexcited beats were noted on telephonic transmissions. At 7 years of age, 1:1 prefixcitation was noted in sinus rhythm. Therefore, late onset of antegrade accessory pathway function is demonstrated. This case provides evidence of developmental changes in accessory pathways. This may explain age related differences in the onset of narrow complex tachycardia in the school age years.
Atrial Tachycardia as the Presenting Sign of a Left Atrial Appendage Aneurysm
Authors: WAGSHAL ALAN B. , APPLEBAUM AZAI , CRYSTAL PAVEL , GOLDFARB BENJAMIN , EREZ ALON , TAGER SALIS , KATZ AMOS
Published: June 2006

A patient presented with atrial tachycardia. The work‐up, guided by the tachycardia morphology, led to the diagnosis of left atrial appendage aneurysm. Surgical removal of the atrial appendage resulted in cure of the tachycardia and associated symptoms.
The Diagnostic Dilemma of “Pseudopacemaker Spikes”
Authors: BROADLEY ANDREW J.M.
Published: June 2006

In a patient who sustained sudden collapse, later attributed to pulmonary embolization, an ECG during her evaluation demonstrated sinus tachycardia and stimulus artefacts at a rate of 250 per minute which did not capture the heart. Implanted pacemaker malfunction was considered the cause until a chest X ray showed a transcutaneous electrical nerve stimulation (TENS) device, which was the source of the artefacts. In instances of rapid stimulus artefacts on the ECG that do not capture the heart, the presence of a TENS device should be considered.
Efficacy and Safety of Bipolar Sensing with High Atrial Sensitivity in Dual Chamber Pacemakers
Authors: WIEGAND UWE K.H. , BODE FRANK , PETERS WERNER , HAASE HENNING , BONNEMEIER HENDRIK , KATUS HUGO A. , POTRATZ JÜRGEN
Published: June 2006

In dual chamber pacemakers, atrial sensing performance is decisive for maintenance of AV synchrony. Particularly, the efficacy of mode switching algorithms during intermittent atrial tachyarrhythmias depends on the sensitive detection of low potential amplitudes. Therefore, a high atrial sensitivity of 0.18 mV, commonly used in single lead VDD pacemakers, was investigated for its efficacy and safety in DDD pacing. Thirty patients received dual chamber pacemakers and bipolar atrial screw‐in leads for sinus node syndrome or AV block; 15 patients suffered from intermittent atrial fibrillation. Pace makers were programmed to an atrial sensitivity of 0.18 mV. Two weeks, 3, 9, and 15 months after implantation, P wave sensing threshold and T wave oversensing thresholds for the native and paced T wave were determined. The myopotential oversensing thresholds were evaluated by isometric contraction of the pectoral muscles. Automatic mode switch to DDIR pacing was activated when the mean atrial rate exceeded 180 beats/min. The patients were followed by 24‐hour Holter monitoring. Two weeks after implantation, mean atrial sensing threshold was 1.81 ± 0.85 mV (range 0.25–2.8 mV) without significant differences during further follow‐up. Native T wave sensing threshold was < 0.18 mV in all patients. In 13% of patients, paced T waves were perceived in the atrial channel at the highest sensitivity. This T wave sensing could easily be avoided by programming a postventricular atrial refractory period exceeding 300 ms. Myopotential oversensing could not be provoked and Holter records showed no signs of sensing dysfunction. During a 15‐month follow‐up, 1,191 mode switch events were counted by autodiagnostic pacemaker function. Forty‐two of these events occurred during Holter monitoring. Unjustified mode switch was not observed. In DDD pacemakers, bipolar atrial sensing with a very high sensitivity is efficient and safe. Using these sensitivity settings, activation of the mode switch algorithm almost completely avoids fast transmission of atrial rate to the ventricle during atrial fibrillation.
Safety and Tolerability of an Aggressive Tilt Table Test Protocol in the Evaluation of Patients with Suspected Neurocardiogenic Syncope
Authors: VLAY STEPHEN C. , BRODSKY CRAIG , VLAY LINDA C.
Published: June 2006

Safety and tolerability of a one‐step tilt table test with high dose (5 μg/min) isoproterenol (ISO) without intermediate stages were evaluated in a symptomatic population of 300 patients referred for clinical syncope, near syncope, or dizziness. ISO has been used as a provocative test but remains controversial. A population of 118 male and 182 female patients with a mean age of 45 (range 5–90) years underwent 300 tests. Heart rate and blood pressure were monitored continuously. A positive test was one in which clinical symptoms were reproduced or hemodynamic criteria met. Patients were initially supine for 5 minutes followed by head upright tilt (HUT) to an angle of 80± for 10 minutes. Negative tests were repeated with an infusion of ISO at a rate of 5 μg/min, HUT was positive in 133 (44.3%) of 300 tests. With a 10‐minute HUT alone, only 17 (5.7%) of 300 of tests were positive. Of the initial negative tests, 273 of 283 were tested with ISO. With ISO, 116(42.5%) of 273 were positive. ISO in high dose (5 μg/min) was used in 264 of 273 patients, while low dose (1.0–2.5 μg/min) was used in 9 of 273 under special circumstances. High dose ISO was tolerated in 164 (62.1 %) of 264 patients, reduced in 87 (33%) of 264, and discontinued in 11 (4.2 %) of 264. Reasons for reduction included tachycardia (40 patients), nausea (31 patients), chest pain (2 patients), arrhythmia (5 patients), or other (9 patients). Adverse effects resolved within 1 minute of dose reduction. This one‐step high dose ISO protocol reproduced neurocardiogenic syncope in symptomatic patients who tested negative without ISO and was safe, tolerated, and expeditious.
Chemoreflexsensitivity in Patients with Survived Sudden Cardiac Arrest and Prior Myocardial Infarction
Authors: HENNERSDORF MARCUS G. , PERINGS CHRISTIAN , NIEBCH VERENA , HILLEBRAND STEFANIE , VESTER ERNST G. , STRAUER BODO E.
Published: June 2006

For evaluation of patients with an increased risk of sudden cardiac death, the analyses of ventricular late potentials, heart rate variability, and baroreflexsensitivity are helpful. But so far, the prediction of a malignant arrhythmic event is not possible with sufficient accuracy, For a better risk stratification other methods are necessary. In this study the importance of the ChRS for the identification of patients at risk for ventricular tachyarrhythmic events should be investigated. Of 41 patients included in the study, 26 were survivors of sudden cardiac arrest. Fifteen patients were not resuscitated, of whom 6 patients had documented monomorphic ventricular tachycardia and 9 had no ventricular tachyarrhythmias in their prior history. All patients had a history of an old myocardial infarction (> 1 year ago). For determination of the ChRS the ratio between the difference of the RR intervals in the ECG and the venous pO2 before and after a 5‐minute oxygen inhalation via a nose mask was measured (ms/mmHg). The 26 patients with survived sudden cardiac death showed a significantly decreased ChRS compared to those patients without a tachyarrhythmic event (1.74 ± 1.02 vs 6.97 ± 7.14 ms/mmHg, P < 0.0001). The sensitivity concerning a survived sudden cardiac death amounted to 88% for a ChRS below 3.0 ms/mmHg. During a 12‐month follow‐up period, the ChRS was significantly different between patients with and without an arrhythmic event (1.64 ± 1.06 vs 4.82 ± 5.83 ms/mmHg, P < 0.01). As a further method for evaluation of patients with increased risk of sudden cardiac death after myocardial infarction the analysis of ChRS seems to be suitable and predicts arrhythmias possibly more sensitive than other tests of neurovegetative imbalance. The predictive importance has to be examined by prospective investigations in larger patient populations.
24‐Hour Heart Rate Variability in Patients with Vasovagal Syncope
Authors: LAZZERI CHIARA , LA VILLA GIORGIO , BARLETTA GIUSEPPE , FRANCHI FRANCO
Published: June 2006

Since alterations in the autonomic nervous system are thought to play a major role in the pathogenesis of vasovagal syncope, we characterized the chronic autonomic profile of 44 patients with syncope and 20 healthy subjects by means of heart rate variability using 24‐hour Holter recordings (time‐ and frequency‐domain indexes), and evaluated whether the different types of responses to tilting (vasodepressive versus cardioinhibitory) could be associated with different cardiac autonomic patterns. Twenty‐three patients exhibited a positive response to tilting, which was vasodepressive in 11 patients and cardioinhibitory in 12 patients. All vasodepressive patients had a standard deviation of the averages of NN (SDANN) intervals in all 5‐minute segments lower than 100 ms. Patients with vasodepressive syncope also had significantly lower values of RMSSD (the 24‐hour square root of the mean of the sum of the squares of differences between adjacent normal RR intervals) than those with cardioinhibitory response, and lacked the day‐night rhythm of the low frequency/high frequency ratio. However, only SDANN values correctly identified patients with vasodepressive response to tilting. We conclude that (1) the population of patients with vasovagal syncope is heterogeneous, (2) patients with vasodepressive syncope have a peculiar chronic autonomic profile as assessed by 24‐hour heart rate variability analysis, and (3) the evaluation of the autonomic profile in 24‐hour Holter recordings could be of value in the diagnosis of patients with syncope.
Identification of the Slow Conduction Zone in Idiopathic Left Ventricular Tachycardia
Authors: MIYAUCHI YASUSHI , KOBAYASHI YOSHINORI , INO TAKESHI , ATARASHI HIROTSUGU
Published: June 2006

The mechanism of verapamil sensitive idiopathic left ventricular tachycardia (ILVT) is considered to be reentry. However, the nature of the reentry circuit, including the location of the slow conduction zone, is unclear. We sought the local electrical activity that would reflect slow conduction by precise mapping around the tachycardia exit (TE) in nine patients with ILVT (mean age, 28 ± 10 years) undergoing radiofrequency catheter ablation (RFCA). The TE was defined as the earliest discrete spiky potential (SP) recorded during the tachycardia, or as a complete configuration‐matched pacemap 12‐lead electrocardiogram (ECG). In all patients, the TE was located at the mid or inferior distal portion of the septum. The SP at the TE preceded the surface QRS by 20 ± 9 ms. The pacemap score at the TE was 11.4 ± 0.6 points. In three patients, fractionated potentials (FP) were recorded during the tachycardia. The onset of the FP preceded the surface QRS by 47 ± 8 ms and was earlier than the SP at the TE (P < 0.01). The sites where an FP was detectable were restricted to a small area, and were at a distance of 14 ±4 mm from the TE. The direction of the FP site from the TE was more basal in two patients and inferior in one, Pacemap ECGs at the sites with an FP showed poor matching (9 ± 1 points), presumably because of predominant capture of the local ventricular muscle rather than an electrically isolated reentry circuit. Successful RFCA was achieved at the site of the FP in all three patients in which one was recorded, and at the TE in the other six patients. The FP, which has been shown to reflect the slow conduction of the ventricular tachycardia circuit in structural heart disease, was also detected in ILVT in the present study, and it is likely to reflect electrical excitation of the distal rim of the slow conduction zone.
Successful Results of a Bipolar Active Fixation Lead for Atrial Application: An Interim Analysis
Authors: BUYS EUGENE M. , VAN HEMEL NORBERT M. , JESSURUN EMILE R. , FOOT BARBARA , KELDER JOHANNES C. , DEFAUW JO J.A.M.
Published: June 2006

Adequate atrial lead performance consists of stable sensing and pacing properties. To evaluate whether the CPI 4269 bipolar lead, covered with mannitol (Sweet Tip), in the atrial position encounters these properties, we performed a prospective study of this lead. After complete dissolution of the mannitol helix, mapping of the atrium to obtain the highest electrogram and lowest threshold was followed by screw‐in into the endocardium. Intraoperative measurements were performed and long‐term follow‐up was scheduled every 6 to 12 months to measure threshold and perform an intracardial electro‐gram. Between February 1993 and December 1996, a total number of 73 leads in the atrial position in a consecutive series of patients was implanted. Implantation was performed in 28 patients receiving an AAIR and 45 patients a DDDR pacemaker. Reason for pacemaker implantation was a third‐degree AV block in 37% of patients, type II second‐degree AV block in 25%, sick sinus syndrome in 35%, and drug refractory paroxysmal atrial fibrillation following His‐bundle ablation in 3%. The intraoperative bipolar atrial electrogram had a mean voltage of 4.25 ± 2.1 mV. The acute atrial bipolar threshold was 0.63 ± 0.43 V, and current was 1.35 ± 0.81 mA at a 1.0‐ms pulse duration. The mean acute resistance of the lead was 572 ± 86 Ohm. After a mean follow‐up of 18.3 months, the bipolar intracardial electrogram was 3.37 ± 2.00 mV, the mean atrial threshold measured at the last outpatient clinic visit was 0.99 ± 0.74 V and the mean impedance was 640 ±127 Ohm. A sensing problem due to traction of the atrial lead occurred in only one patient. Acute and late dislodgement did not occur. The CPI 4269 (Sweet Tip) lead is manufactured with a dissolvable capsule covering the helix tip electrode, permitting a safe passage through the venous system. This interim analysis shows that this lead in the atrial position has favorable acute and chronic results.
Thrombus Formation at the Site of Radiofrequency Catheter Ablation
Authors: FARAH AMIN , KHAN FARRUKH , MACHADO CHRISTIAN
Published: June 2006

A 55‐year‐old woman with a history of resected atrial myxoma with residual patched atrial septal defect (ASD) underwent a successful radiofrequency (RF) ablation of reentry atrial tachycardia. She presented with progressive dyspnea 5 days later. Transesophageal echocardiography revealed a 1‐cm right atrial mass attached to the intra atrial septum at the ablation site. Repeat study after anticoagulation for 5 weeks showed complete resolution of the thrombus. Thrombus formation at the site of RF ablation is a potential complication that may require aggressive anticoagulation. Patients with patched ASD might be at higher risk.
Regional Differences in Arrhythmogenic Aftereffects of High Intensity DC Stimulation in the Ventricles
Authors: KODAMA ITSUO , SAKUMA ICHIRO , SHIBATA NITARO , KNISLEY STEPHEN B. , NIWA RYOKO , HONJO HARUO
Published: June 2006

Regional differences of the aftereffects of high intensity DC stimulation were investigated in isolated rabbit hearts stained with a voltage‐sensitive dye (di‐4‐ANEPPS). Optical action potential signals were recorded from the epicardial surface of the right and left ventricular free wall (RVep, LVep) and from the right endocardial surface of the interventricular septum (IVS). Ten‐millisecond monophasic DC stimulation (S2, 20–120 V) was applied to the signal recording spots during the early plateau phase of the action potential induced by basic stimuli (S1, 2.5 Hz). There was a linear relationship between S2 voltage and the S2 field intentisy (FI). S2 caused postshock additional depolarization. giving rise to a prolongation of the shocked action potential. With S2≥ 40 V (FI ≥≃20 V/cm), terminal repolarization of action potential was inhibited, and subsequent postshock S1 action potentials for 1–5 minutes were characterized by a decrease in the maximum diastolic potential and a decrease in the amplitude and a slowing of their upstroke phase. The higher the S2 voltage, the larger the aftereffects. The changes in postshock action potential configuration in RVep were significantly greater than those observed in LVep and IVS when compared at the same levels of S2 intensity. In RVep, 12 of 20 shocks of 120 V resulted in a prolonged refractoriness to S1 (> 1 s), and the arrest was often followed by oscillation of membrane potential. Ventricular tachycardia or fibrillation ensued from the oscillation in five cases. No such long arrest or serious arrhythmias were elicited in LVep and IVS. These results suggest that RVep is more susceptible than LVep and IVS for arrhythmogenic aftereffects of high intensity DC stimulation.