bluuebunny/crossref_metadata_2025 huggingface dataset:
Diagnostic Performance of a Dual‐Chamber Cardioverter Defibrillator Programmed with Nominal Settings: A European Prospective Study
Authors: SADOUL NICOLAS , JUNG WERNER , JORDAENS LUC , LEENHARDT ANTOINE , SANTINI MASSIMO , WOLPERT CHRISTIAN , ALIOT ETIENNE
Published: August 2003

Arrhythmia Discrimination by ICD.
Introduction: Despite technologic developments, accurate discrimination of ventricular tachyarrhythmia from rapid rhythms of nonventricular origin remains a challenge. We sought to examine the sensitivity and specificity of a dual‐chamber arrhythmia detection algorithm, the PARAD algorithm, incorporated in a dual‐chamber implantable cardioverter defibrillator, the Defender (ELA Medical).

Methods and Results:All detailed tachycardia episodes (i.e., with stored atrial and ventricular channel markers and electrograms) retrieved from the Holter memory of the device were analyzed from 95 patients (86 men and 9 women; age 62 ± 12 years) implanted with the Defender with the algorithm programmed at nominal settings. Over a follow‐up of 15 ± 8 months, 559 detailed sustained tachycardia episodes detected in the tachycardia zone were gathered in 62 patients. Of the 300 ventricular tachycardia (VT) episodes, 298 were appropriately classified as VT by the algorithm. Of the 259 supraventricular tachycardia (SVT) episodes, 231 were appropriately classified as SVT. In 8 patients, 28 episodes of SVT were misclassified as VT: 25 atrial fibrillation episodes (6 patients), 2 sinus tachycardia (1 patient), and 1 atrial tachycardia. Calculated sensitivity and specificity were 99.3% and 89.2% on a per episode basis and 99.8% (95% confidence interval: 97.8 to 100) and 91.6% (95% confidence interval: 86.0 to 97.3) on a per patient basis, respectively.

Conclusion: In this selected population of patients, the PARAD algorithm was safe and reliable for detection of a wide spectrum of tachyarrhythmias. Its specificity was high, particularly with respect to sinus tachycardia detection, but it must be improved with respect to detection of atrial fibrillation.
Implantable Cardioverter Defibrillator Utilization Based on Discharge Diagnoses from Medicare and Managed Care Patients
Authors: RUSKIN JEREMY N. , CAMM A. JOHN , ZIPES DOUGLAS P. , HALLSTROM ALFRED P. , MCGRORY‐USSET MARY E.
Published: August 2003

ICD Utilization.
Introduction: Implantable cardioverter defibrillators (ICDs) have become an accepted therapy for patients at high risk of sudden cardiac death. To assess the current utilization of this therapy, we estimated the number of patients at risk of sudden death using an historical claims‐based study and compared these results to current ICD usage volumes.

Methods and Results: Managed care and Medicare databases (claims related to 4.6 million covered U.S. lives during a 12‐month period) were analyzed to identify patients who had either a primary or secondary diagnosis of ventricular tachycardia, ventricular fibrillation, ventricular flutter, or cardiac arrest. These patients were further required to have a diagnosis code indicating a previous myocardial infarction or congestive heart failure. Patients who died during the study period or did not have medical insurance were excluded. In the base case scenario, 1,226 patients per million population were identified as potential ICD candidates. Sensitivity analyses reduced that value to a range from 736 to 1,140 ICD candidates per million population. Sensitivity factors considered included acute myocardial infarction, comorbidities, age, secondary ventricular tachycardia/ventricular fibrillation diagnosis, and varying degrees of left ventricular dysfunction. These results contrast with an ICD usage rate of 416 per million population in the United States and lower rates in other countries.

Conclusion: This study suggests that, based on discharge diagnoses, many patients who could benefit from ICDs are not receiving this therapy. Diverse reasons for this underutilization should be addressed to improve access to, and appropriate use of, this therapy.
T Wave Alternans as a Predictor of Spontaneous Ventricular Tachycardia in a Canine Model of Sudden Cardiac Death
Authors: TSAI JEROME , CAO JI‐MIN , ZHOU SHENGMEI , SWISSA MOSHE , CATES ADAM W. , KENKNIGHT BRUCE H. , CHEN LAN S. , KARAGUEUZIAN HRAYR S. , CHEN PENG‐SHENG
Published: August 2003

T Wave Alternans as Predictor of Spontaneous VT.
Introduction: We recently developed an ambulatory canine model of spontaneous ventricular tachycardia (VT) and sudden cardiac death by creating myocardial infarction, complete AV block, and infusion of nerve growth factor to the left stellate ganglion. Whether or not T wave alternans is associated with the spontaneously occurring episodes of VT in our model was unclear.

Methods and Results: Through intracardiac electrograms obtained from an implantable cardioverter defibrillator, we manually measured T wave amplitudes prior to VT and while the dogs were at rest (baseline, no VT). Of the 79 VT episodes analyzed, 28 (35.4%) exhibited repolarization alternans. In contrast, only 3 (4.7%) of 64 baseline data cases displayed alternans (P < 0.0001). The magnitude of T wave alternans for dogs that died of sudden cardiac death, dogs that did not die suddenly, and for the total 28 episodes that exhibited repolarization alternans were 4.8 ± 2.8 mm, 4.9 ± 3.5 mm, and 4.9 ± 3.3 mm, respectively (P = NS). We also found the sensitivity, specificity, positive predictive value, negative predictive value, and relative risk of repolarization alternans in predicting VT to be 35.4%, 95.3%, 90.3%, 54.5%, and 1.98, respectively. The ventricular rate prior to VT (65 ± 11 beats/min) was significantly higher than that at rest (49 ± 12 beats/min; P < 0.0001).

Conclusion: T wave alternans often occurred immediately before the onset of VT in dogs with myocardial infarction, complete AV block, and nerve growth factor infusion to the left stellate ganglion. Increased sympathetic activity might be responsible for the occurrence of the T wave alternans.
Use of an Insertable Loop Recorder in a Myotonic Dystrophy Patient
Authors: HADIAN DJAVID , LOWE MIRIAM R. , SCOTT LUIS R. , GROH WILLIAM J.
Published: August 2003

Loop Recorder Use in Myotonic Dystrophy. The case of a 66‐year‐old woman with myotonic dystrophy is presented. This patient underwent implantation of an insertable loop recorder as a participant in a clinical trial. At 1‐month follow‐up, interrogation of the insertable loop recorder revealed multiple episodes of wide complex tachycardia. She underwent electrophysiologic study, which revealed moderate His‐Purkinje disease, focal atrial tachycardia, monomorphic ventricular tachycardia, and ventricular fibrillation. Successful radiofrequency ablation of the focal atrial tachycardia and implantation of a dual‐chamber implantable cardioverter defibrillator was performed.
Latent Mahaim Fiber as a Cause of Antidromic Reciprocating Tachycardia: Recognition and Successful Radiofrequency Ablation
Authors: DAVIDSON NEIL C. , MORTON JOSEPH B. , SANDERS PRASHANTHAN , KALMAN JONATHAN
Published: August 2003

Latent Mahaim Fiber. The term “Mahaim fiber” usually is applied to an atriofascicular fiber that inserts distally into the right bundle branch and forms the anterograde limb of a reciprocating tachycardia. One of the features that has been used to describe the physiology of Mahaim fibers is the presence of anterograde preexcitation. We describe two patients who had a clinical tachycardia consistent with a “Mahaim tachycardia” in whom there was no evidence or minimal evidence of anterograde preexcitation during sinus rhythm or atrial pacing. In both patients, the tachycardia was rendered noninducible by radiofrequency ablation at the site of Mahaim potentials at the tricuspid annulus, and a long‐term cure was achieved. This is the first description of a “latent Mahaim fiber” that does not cause preexcitation but which can support antidromic reciprocating tachycardia.
Human Pathologic Validation of Left Ventricular Linear Lesion Formation Guided by Noncontact Mapping
Authors: KNIGHT BRADLEY P. , BOGNER PAUL , WASMER KRISTINA , MORADY FRED
Published: August 2003

Linear Lesions Guided by Noncontact Mapping. This case report describes the histopathologic findings associated with two left ventricular, linear radiofrequency lesions in a patient who underwent cardiac transplantation shortly after an ablation procedure for ventricular tachycardia. The lesions were created with conventional ablation equipment guided by a noncontact mapping system. The findings provide pathologic validation that continuous, linear lesions are feasible using a noncontact mapping system for guidance.
Calcium Cycling in Heart Failure: The Arrhythmia Connection
Authors: POGWIZD STEVEN M. , BERS DONALD M.
Published: August 2003

Calcium Cycling in Heart Failure. Ventricular tachycardia in nonischemic heart failure (HF) arises from a nonreentrant mechanism most likely due to delayed afterdepolarizations from activation of a transient inward current (Iti). We present data and a paradigm in which an up‐regulated Na/Ca exchanger, residual‐adrenergic responsiveness, and decreased inward rectifying K current (IK1) in HF all conspire to markedly increase the propensity for triggered arrhythmias. The up‐regulated Na/Ca exchanger plays an additional critical role in unloading the sarcoplasmic reticulum of Ca, thereby causing the mechanical dysfunction. It is imperative that therapeutic approaches for ventricular tachycardia in HF take into consideration cellular Ca handling and excitation‐contractile coupling, and their alteration in the failing heart.
Pulmonary Vein Paced Activation Sequence Mapping: Comparison with Activation Sequences During Onset of Focal Atrial Fibrillation
Authors: DEEN VINCENT R. , MORTON JOSEPH B. , VOHRA JITENDRA K. , KALMAN JONATHAN M.
Published: August 2003

Activation Sequence Mapping of Focal AF.
Introduction: Atrial fibrillation (AF) may originate from a single focus, with the vast majority observed within the pulmonary veins. To facilitate mapping, we hypothesized that there would be a characteristic right atrial endocardial activation sequence pattern associated with pacing and spontaneous focal activity from each of the four pulmonary veins.

Methods and Results: In 10 patients with focal AF, a standardized set of catheters was positioned in the right atrium. These included a 20–pole catheter along the crista terminalis, a decapolar catheter in the coronary sinus (CS), and a His‐bundle electrode. Pacing (700 and 300 msec) was performed with a mapping catheter from each of the four pulmonary veins. Activation sequence maps were created by measurement of activation times to each of the recording bipoles with the proximal CS bipole as the arbitrary reference point. Similar maps were constructed for the activation sequence of the pulmonary vein ectopic that initiated AF. There was a characteristic right atrial activation map created by pacing each pulmonary vein that corresponded closely with the map from the same pulmonary vein during initiation of focal AF. The pulmonary vein of origin could be distinguished on the basis of this characteristic pattern and some stereotypic observations. CS activation occurred proximal to distal for right pulmonary veins and distal to proximal for left pulmonary veins. Significant differences in activation timing between the CS and crista terminalis differentiated upper from lower pulmonary veins.

Conclusion: There is a characteristic right atrial activation map for activity arising from each of the four pulmonary veins that corresponded closely with the map from the same pulmonary vein during initiation of focal AF. These findings may facilitate mapping and ablation of focal AF.
Effects of Verapamil and Ibutilide on Atrial Fibrillation and Postfibrillation Atrial Refractoriness
Authors: STICHERLING CHRISTIAN , HSU WILLIAM , TADA HIROSHI , BARES ANTON C. , ORAL HAKAN , PELOSI FRANK , KNIGHT BRADLEY P. , STRICKBERGER S. ADAM , MORADY FRED
Published: August 2003

Verapamil and Ibutilide.
Introduction: Early recurrence of atrial fibrillation (AF) after cardioversion may be related to shortening of the atrial effective refractory period (ERP). This study compared the effects of verapamil and ibutilide on AF cycle length (AFCL), atrial ERP, and susceptibility to recurrent AF.

Methods and Results: In 33 adults, the atrial ERP was measured at basic drive CLs of 350 and 500 msec before and after a brief episode of pacing‐induced AF. During AF, verapamil, ibutilide, or saline was infused in 11 patients each. Shortening of the post‐AF atrial ERP was attenuated by verapamil and prevented by ibutilide. AFCL shortened by 32 ± 21 msec in the verapamil group (P < 0.01), prolonged by 44 ± 14 msec in the ibutilide group (P < 0.001), and did not change in the control group. AF converted to sinus rhythm within 10 minutes less often after verapamil (0%) than after ibutilide (82%) or than in the control group (73%). Post‐AF, AF lasting > 10 minutes was induced more often in the verapamil group than in the ibutilide group (26% vs 0%; P = 0.01). Another 10 patients received verapamil or ibutilide in the absence of AF. Atrial ERP was unchanged after verapamil and prolonged after ibutilide.

Conclusion: Verapamil shortens AFCL and impedes the conversion of induced AF, whereas ibutilide prolongs AFCL and does not impede the early conversion of induced AF. Ibutilide is more effective than verapamil in preventing post‐AF shortening of the atrial ERP and reducing the susceptibility toward reinduction of AF.
Reexpression of the Nifedipine‐Resistant Calcium Channel During Dedifferentiation of Adult Rat Ventricular Cardiomyocytes
Authors: PIGNIER CHRISTOPHE , ANCEY CÉCILE , FARES NASSIM , BESCOND JOCELYN , POTREAU DANIEL
Published: August 2003

Nifedipine‐Resistant Calcium Current.
Introduction: Using an adult rat ventricular culture model and whole‐cell patch‐clamp technique, we investigated whether the nifedipine‐resistant calcium current observed at the neonatal stage but not at the adult stage could be reobserved under dedifferentiating conditions.

Methods and Results: Application of 2 μM nifedipine totally inhibited the inward calcium current (carried by 5 mM Ba2+) in freshly isolated cells from adult rat heart, but it failed to block it completely when cells are cultured for 8 to 12 days. Dose‐response curves of nifedipine in the range from 2 to 50 μM showed a residual current that represented, in the presence of 2 μM nifedipine, 16.4% ± 1.8% (n = 10) and 20.4% ± 1.5% (n = 10) of the total current in 8‐ and 12‐day‐old cultured cells, respectively. In these conditions, its density at 0 mV increased slightly during culture (−2.1 ± 0.2 pA/pF, n = 7, and −3.2 ± 0.4 pA/pF, n = 8, after 8 and 12 days in culture, respectively), without modification in the current‐tovoltage curve, as well as in kinetics properties.

Conclusion: These results show that nifedipine‐resistant calcium current, which has been shown to be developmentally regulated in rat ventricular cardiomyocytes, can be reexpressed in cultured‐dedifferentiated cells. Its possible expression and implication in physiopathologic function are suggested.
Atrioventricular Nodal Reentrant Tachycardia in Children: Effect of Slow Pathway Ablation on Fast Pathway Function
Authors: VAN HARE GEORGE F. , CHIESA NANCY A. , CAMPBELL ROBERT M. , KANTER RONALD J. , CECCHIN FRANK ,   FOR THE PEDIATRIC ELECTROPHYSIOLOGY SOCIETY
Published: August 2003

AV Nodal Reentry in Children.
Introduction: Prior studies in adults have shown significant shortening of the fast pathway effective refractory period after successful slow pathway ablation. As differences between adults and children exist in other characteristics of AV nodal reentrant tachycardia (AVNRT), we sought to characterize the effect of slow pathway ablation or modification in a multicenter study of pediatric patients.

Methods and Results: Data from procedures in pediatric patients were gathered retrospectively from five institutions. Entry criteria were age < 21 years, typical AVNRT inducible with/without isoproterenol infusion, and attempted slow pathway ablation or modification. Dual AV nodal pathways were defined as those with > 50 msec jump in A2‐H2 with a 10‐msec decrease in A1‐A2. Successful ablation was defined as elimination of AVNRT inducibility. A total of 159 patients (age 4.4 to 21 years, mean 13.1) were studied and had attempted slow pathway ablation. AVNRT was inducible in the baseline state in 74 (47%) of 159 patients and with isoproterenol in the remainder. Dual AV nodal pathways were noted in 98 (62%) of 159 patients in the baseline state. Ablation was successful in 154 (97%) of 159 patients. In patients with dual AV nodal pathways and successful slow pathway ablation, the mean fast pathway effective refractory period was 343 ± 68 msec before ablation and 263 ± 64 msec after ablation. Mean decrease in the fast pathway effective refractory period was 81 ± 82 msec (P < 0.0001) and was not explained by changes in autonomic tone, as measured by changes in sinus cycle length during the ablation procedure. Electrophysiologic measurements were correlated with age. Fast pathway effective refractory period was related to age both before (P = 0.0044) and after ablation (P < 0.0001). AV block cycle length was related to age both before (P = 0.0005) and after ablation (P < 0.0001). However, in dual AV nodal pathway patients, the magnitude of change in the fast pathway effective refractory period after ablation was not related to age.

Conclusion: Lack of clear dual AV node physiology is common in pediatric patients with inducible AVNRT (38%). Fast pathway effective refractory period shortens substantially in response to slow pathway ablation. The magnitude of change is large compared with adult reports and is not completely explained by changes in autonomic tone. Prospective studies in children using autonomic blockade are needed.
Prevalence of a Shared Isthmus in Postinfarction Patients with Pleiomorphic, Hemodynamically Tolerated Ventricular Tachycardias
Authors: BOGUN FRANK , LI YI‐GANG , GROENEFELD GERIAN , HOHNLOSER STEFAN H. , SCHUGER CLAUDIO , ORAL HAKAN , PELOSI FRANK , KNIGHT BRADLEY , STRICKBERGER S. ADAM , MORADY FRED
Published: August 2003

Shared Isthmus.
Introduction: Multiple forms of ventricular tachycardia (VT) after myocardial infarction may result from multiple reentrant circuits that share an isthmus or from separate reentrant circuits. The prevalence of a shared isthmus in patients with multiple hemodynamically tolerated VTs has not been determined.

Methods and Results: Criteria for a shared isthmus consisted of (1) concealed entrainment of > 1 VT at a single pacing site; (2) concealed entrainment during VT and a perfect pace map of another VT at the same pacing site; or (3) concealed entrainment of VT of a given morphology that had at least two cycle lengths that varied by at least 100 msec. In a series of 19 patients (16 men and 3 women; age 65 ± 14 years, ejection fraction 0.25 ± 0.09) with 54 VTs (mean cycle length 494 ± 98 msec), there was evidence of a shared isthmus in 23 VTs (43%) at 11 sites in 9 patients. Concealed entrainment of two different VTs was observed at 4 of 11 sites. At 5 of 11 sites there was concealed entrainment of one VT and a perfect pace map of another VT. At the remaining 2 of 11 sites, there was concealed entrainment of a VT that had two different cycle lengths. Nineteen of the 23 VTs were ablated successfully with radiofrequency energy applications at 11 sites.

Conclusion: In postinfarction patients with pleiomorphic, hemodynamically stable VT, a shared isthmus may be present in approximately 40% of VTs.
Appraisal of “Mahaim” Automatic Tachycardia
Authors: STERNICK EDUARDO BACK , GERKEN LUIZ MÁRCIO , VRANDECIC MÁRIO
Published: August 2003

“Mahaim” Automatic Tachycardia. A series of four patients with right‐sided accessory pathways with long conducting times and decremental properties is reported. All patients underwent radiofrequency catheter ablation, and target areas were guided by a discrete “Mahaim” potential recorded at the lateral aspect of the tricuspid valve. A slow automatic and irregular rhythm with a QRS morphology similar to that of a fully preexcited QRS complex occurred during radiofrequency current delivery. The occurrence of so‐called “Mahaim” automatic tachycardia heralded successful elimination of the accessory pathway in a manner similar to that of junctional automatic rhythm during slow pathway ablation in patients with AV nodal reentrant tachycardia. The observation of an automatic rhythm brought about during radiofrequency current ablation of a Mahaim‐like accessory pathway is electrophysiologic evidence of the accessory AV nodal behavior of this structure.
Polymorphisms in Beta‐Adrenergic Receptor Genes in the Acquired Long QT Syndrome
Authors: KANKI HIDEAKI , YANG PING , XIE HONG‐GUANG , KIM RICHARD B. , GEORGE ALFRED L. , RODEN DAN M.
Published: August 2003

Adrenergic Receptor Polymorphism and Arrhythmia.
Introduction: Sympathetic activation is a trigger for life‐threatening arrhythmias in many patients with the congenital long QT syndrome (LQTS), and an increase in heart rate has been reported just prior to torsades de pointes in patients with drug‐associated (acquired) LQTS (aLQTS). We compared the frequencies of five recognized nonsynonymous coding region polymorphisms in genes encoding the β1‐adrenergic and β2‐adrenergic receptors (AR) in 93 patients with aLQTS and 3 control groups: an ethically diverse set of individuals from middle Tennessee (n = 71), a subset of the Polymorphism Discovery Resource obtained from National Human Genome Research Institute (n = 89), and patients who tolerated QT‐prolonging drugs without aLQTS (non‐aLQTS group; n = 66).

Methods and Results: Polymerase chain reaction‐restriction fragment length polymorphism was used to screen for Ser49Gly and Gly389Arg (β1‐AR) and Thr164Ile (β2‐AR). For Arg16Gly and Gln27Glu, polymorphic sites 33 nucleotides apart in the β2‐AR, single‐stranded conformational polymorphism was used to distinguish among the 4 possible haplotypes and 10 possible genotypes. Allele frequencies were similar among the 4 groups at the 2β1‐AR sites. The uncommon Ile164 variant in β2‐AR was slightly more frequent in patients (3.2%) than in any of the 3 control groups (0.6% to 2.3%). At the 16–27 neighboring sites in the β2‐AR, one haplotype (Arg16/Glu27) was not detected, as in previous studies; hence, only 6 genotypes were present. There were fewer Gly16/Gln27 homozygotes in the non‐aLQTS group (1.5%) than in two other control groups or the aLQTS group (8.5% to 10%).

Conclusion: None of the five common nonsynonymous coding region polymorphisms in the β‐AR genes predict drug‐associated torsades de pointes, although the Gly16/Gln27 haplotype may be a risk factor.
Histopathologic Exploration of Intra‐Hisian Conduction Disturbances
Authors: MATSUYAMA TAKA‐AKI , INOUE SHIN , KOBAYASHI YOUICHI , SAITO TSUKASA , TANNO KAORU , SAKAI TETSUO , OTSUKA TOSHIHIKO , SHIOKAWA AKIRA , KATAGIRI TAKASHI , OTA HIDEKAZU
Published: August 2003

Pathology of Intra‐Hisian Block.
Introduction: The length of the His bundle and the precise location of injury responsible for split His potentials have not been fully established in patients with intra–Hisian block. We conducted an autopsy study comparing histologic findings in intra‐Hisian block versus control hearts.

Methods and Results: We studied hearts from 4 intra‐Hisian block patients (age 66 to 93 years, mean 79.5) and hearts from 14 patients without AV conduction abnormalities (control). All intra‐Hisian block patients underwent electrophysiologic evaluation; 3 patients demonstrated intra‐Hisian block and 1 showed no His potential. Autopsies were performed when each patient died. After the heart was fixed in formaldehyde, the AV septal junctional area was removed en bloc and serially sectioned into 7‐μm thick slices. For study purposes, we considered the three segments of the His bundle separately: the penetrating bundle, the nonbranching bundle, and the branching bundle. The actual length of each segment was calculated from the number of respective serial sections, and the lesion was reconstructed within the conduction axis. Intra‐Hisian block hearts were heavier than control hearts (mean weight 389 vs 301 g; P < 0.05). The lesion was situated in the nonbranching bundle in 3 hearts and in the penetrating bundle in 1 heart. Mean compact node length was 3.8 mm in intra‐Hisian block hearts and 3.3 mm in control hearts. The penetrating bundle was 2.1 and 2.1 mm, the nonbranching bundle was 3.5 and 1.9 mm, and the branching bundle was 4.5 and 4.6 mm in intra‐Hisian block and control hearts, respectively.

Conclusion: Most lesions were observed in the nonbranching bundle adjacent to the junction between the central fibrous body and ventricular septum. This segment was longer in intra‐Hisian block hearts than in control hearts.
Supervulnerable Phase Immediately After Termination of Atrial Fibrillation
Authors: DUYTSCHAEVER MATTIAS , DANSE PETER , ALLESSIE MAURITS
Published: August 2003

Supervulnerable Phase After Termination of AF.
Introduction: Recent studies with the implantable atrial cardioverter have shown that atrial fibrillation (AF) recurs almost immediately after successful cardioversion in about 27% of cases. In the present study, we determined the electrophysiologic properties of the caprine atrium immediately after spontaneous termination of AF both before and after 48 hours of AF‐induced electrical remodeling.

Methods and Results: In eight goats, atrial effective refractory period (AERP), intra‐atrial conduction velocity, and atrial wavelength were measured during sinus rhythm both before (t = 0) and after 48 hours (t = 48) of electrically maintained AF (baseline). After baseline, a 5‐minute paroxysm of AF was induced, during which the refractory period (RPAF) was determined. AERP, conduction velocity, and atrial wavelength also were measured immediately after spontaneous restoration of sinus rhythm (post‐AF values). Both in normal and remodeled atria, immediately after AF, AERP and conduction velocity were markedly decreased compared with baseline (P < 0.01). In normal atria, post‐AF AERP (107 ± 14 msec) gradually prolonged from its AF value (114 ± 17 msec) to its baseline value (138 ± 13 msec). Conduction velocity decreased from 130 ± 9 cm/sec to 117 ± 9 cm/sec. After 48 hours of AF, AERP had shortened to 74 ± 8 msec. RPAF was 89 ± 9 msec. Surprisingly, immediately after termination of AF, AERP shortened further to 58 ± 6 msec (P < 0.01). Post‐AF conduction velocity decreased from 136 ± 11 cm/sec to 122 ± 10 cm/sec (P < 0.01). As a result, the post‐AF atrial wavelength became as short as 7.1 ± 1 cm. These changes were transient, and all parameters gradually returned to baseline within 1 to 2 minutes after conversion of AF.

Conclusion: Due to a combined decrease in AERP and conduction velocity, marked shortening of the atrial wavelength occurs during the first minutes after conversion of AF. In electrically remodeled atria, this results in a transient ultrashort value of AERP (< 60 msec) and atrial wavelength (7.1 cm). These observations imply a highly vulnerable substrate for reentry immediately after termination of AF. During this supervulnerable phase, both early and later premature beats reinitiated immediate recurrences of AF.
Effects of Estrogen on Cardiac Electrophysiology in Female Mice
Authors: SABA SAMIR , ZHU WEI , ARONOVITZ MARK J. , ESTES N.A. MARK , WANG PAUL J. , MENDELSOHN MICHAEL E. , KARAS RICHARD H.
Published: August 2003

Estrogen and Cardiac Electrophysiology.
Introduction: Understanding the molecular mechanisms that underlie gender‐ and hormonal‐related differences in susceptibility to cardiac arrhythmias has been hampered by the lack of a suitable animal model. We examined the effect of hormonal status on the electrophysiologic (EP) properties of the mouse heart in an in vivo, closed chest model.

Methods and Results: Fifty‐three female C57/J mice aged 10 to 12 weeks were studied. Thirty‐six mice underwent bilateral ovariectomies; 18 received estrogen (OVX + E) and 18 received placebo (OVX). Seventeen female mice underwent only sham surgery. All animals underwent in vivo EP studies. Select EP parameters were measured after quinidine treatment. Data were analyzed by a blinded observer. Compared with the intact female mice, the PR and AH intervals were significantly shorter in the OVX mice, and these parameters normalized with estrogen replacement (PR = 45.9 ± 4.5 msec in the intact mice, 42.1 ± 4.3 msec in the OVX group, and 46.9 ± 3.5 msec in the OVX + E group, P < 0.005; AH = 36.5 ± 4.9 msec in the intact mice, 34.4 ± 4.7 msec in the OVX group, and 38.8 ± 2.7 msec in the OVX + E group, P = 0.03). The right ventricular effective refractory period was significantly shorter in the OVX mice versus the intact mice, and this also normalized with estrogen replacement. Hormonal status did not significantly affect any other EP variable, including QT interval.

Conclusion: In female mice, estrogen prolongs AV nodal conduction and the right ventricular effective refractory period. Taken together, these data suggest that hormonal status affects aspects of cardiac EP function. Future application of this mouse model will be helpful in determining the molecular pathways that mediate hormonal differences in cardiac EP.
Accessory Pathway Automaticity After Radiofrequency Ablation
Authors: MACLE LAURENT , SHAH DIPEN C. , JAÏS PIERRE , HAÏSSAGUERRE MICHEL
Published: August 2003

Accessory Pathway Automaticity. Mapping in a patient undergoing radiofrequency ablation for a left‐sided concealed accessory pathway showed that the site with the shortest VA conduction time was in the great cardiac vein. Epicardial radiofrequency delivery at that site was successful. After ablation, a potential dissociated from both atrial and ventricular activity during sinus rhythm and atrial pacing was noted on the distal bipole of the ablation catheter. During incremental ventricular pacing, intermittent ventricular to potential conduction was observed. This indicates complete block at the atrial‐accessory pathway interface and impaired conduction at the ventricular interface. This dissociated activity originating neither from the ventricle nor from the atria provides evidence of automatic accessory pathway activity.
Temporal Patterns of Atrial Arrhythmia Recurrences in Patients with Implantable Defibrillators: Implications for Assessing Antiarrhythmic Therapies
Authors: SHEHADEH LINA A. , LIEBOVITCH LARRY S. , WOOD MARK A.
Published: August 2003

Temporal Patterns of Atrial Arrhythmias.
Introduction: The statistical measures commonly used to assess therapies for recurrent atrial arrhythmias (such as time to first recurrence) often assume a uniformly random pattern of arrhythmic events over time. However, the true temporal pattern of atrial arrhythmia recurrences is unknown. The aim of this study was to use linear and nonlinear analyses to characterize the temporal pattern of atrial arrhythmia recurrences in patients with implantable cardioverter defibrillators.

Methods and Results: The time and date of atrial tachyarrhythmias recorded in 65 patients with combined atrial and ventricular defibrillators were used to construct a probability density function (PDF) and a model of a Poisson distribution of arrhythmic events for each patient. Average patient age was 66 ± 10 years and follow‐up was 7.8 ± 4.8 months. A total of 10,759 episodes of atrial tachyarrhythmias were analyzed (range 43 to 618 episodes per patient). The PDF fit a power law distribution for all 65 patients, with an average r2= 0.89 ± 0.08. The PDF distribution differed significantly from the model Poisson distribution in 47 of 65 patients (P = 0.0002). Differences from the Poisson distribution were noted for patients both taking (30/43 patients; P < 0.015) and not taking (17/22 patients; P < 0.017) antiarrhythmic drugs. Median time between atrial arrhythmia detections for all 65 patients was 10.8 minutes.

Conclusion: In implantable cardioverter defibrillator patients, the temporal pattern of frequent recurrences of atrial tachyarrhythmias usually is characterized by a power law distribution. The unique statistical properties of this type of distribution should be considered in designing outcome measures for treatment of atrial tachyarrhythmias.
Epicardial Foci of Atrial Arrhythmias Apparently Originating in the Left Pulmonary Veins
Authors: KATRITSIS DEMOSTHENES , GIAZITZOGLOU ELEFTHERIOS , KOROVESIS SOCRATES , PAXINOS GEORGE , ANAGNOSTOPOULOS CONSTANTINE E. , CAMM A. JOHN
Published: August 2003

Epicardial Foci of Atrial Arrhythmias.
Introduction: Epicardial potential sources of atrial arrhythmias, such as the ligament of Marshall, are in close proximity with, and electrically connected to, the left superior pulmonary vein. Ectopic activity arising from these areas may be difficult to differentiate from ectopy that, according to endocardial only mapping, originates in the left superior pulmonary vein. We hypothesized that in patients with paroxysmal atrial fibrillation (AF) apparently originating in the left pulmonary veins, mapping through the distal coronary sinus might identify possible epicardial locations of the arrhythmogenic focus.

Methods and Results: Forty patients (age 48 ± 12 years) who underwent catheter ablation for paroxysmal AF were studied by epicardial mapping through the distal, superoposterior coronary sinus. Catheterization of the distal coronary sinus in order to approach the ostium of the left superior pulmonary vein was feasible in 14 of 19 patients with AF originating in the left superior vein (11 patients) or inferior pulmonary vein (3 patients) according to endocardial mapping criteria. In 2 patients, the sole focus of atrial tachycardia/fibrillation was epicardial with earliest activation clearly preceding electrograms recorded at the os of the left superior pulmonary vein or any other endocardial mapping site. Epicardial potentials separated from atrial electrograms were present during sinus rhythm in both patients and during atrial tachycardia in one patient. Catheter ablation through the coronary sinus rendered the arrhythmia noninducible in both patients without abolishing epicardial potentials in one of them.

Conclusion: In patients with paroxysmal AF apparently originating from the left superior or inferior pulmonary vein, detailed epicardial mapping through the distal coronary sinus might identify epicardial locations of the arrhythmogenic focus.
Pediatric Radiofrequency Catheter Ablation Registry Success, Fluoroscopy Time, and Complication Rate for Supraventricular Tachycardia: Comparison of Early and Recent Eras
Authors: KUGLER JOHN D. , DANFORD DAVID A. , HOUSTON KRIS A. , FELIX GARY
Published: August 2003

Ablation Outcomes for Supraventricular Tachycardia.
Introduction: To assess changes of success rate, fluoroscopy time, and complication rate for six supraventricular tachycardia pathways/mechanisms, data from the Pediatric Radiofrequency Catheter Ablation Registry were grouped into two eras (1991–1995; 1996–1999).

Methods and Results: Data from the early era and the late era were compared using the Chi‐square test for the outcomes of success rate and complication rate and using the Student's t‐test for the outcome of mean fluoroscopy time. In the Registry as a whole, ablation failure rates fell from 9.6% in the early era to 4.8% in the recent era, a reduction of 50% overall. Improved success rates were found for posterior septal, right free‐wall, and left free‐wall pathways and for AV nodal reentry, whereas anterior septal pathways and atrial ectopic‐focus tachycardia did not show improvement. Mean fluoroscopy time overall decreased 21% from 50.9 ± 39.9 minutes to 40.1 ± 35.1 minutes. Individually, the improvement in fluoroscopy time was found for all but the atrial ectopic‐focus tachycardia mechanism. The complication rate decreased from 4.2% to 3.0%, with significant decreases for left free‐wall and posterior septal pathways.

Conclusion: Patient selection strategies to optimize radiofrequency ablation outcomes in children, which have been based on the previously published Registry data, should be reconsidered in light of these new, updated data. The lack of uniform improvement provides the impetus for further research and development of new approaches and technologic advances so that further improvement can be achieved.
Determinants of First‐Shock Success for Atrial Implantable Cardioverter Defibrillators
Authors: SWERDLOW CHARLES D. , SCHWARTZMAN DAVID , HOYT ROBERT , BAILIN STEVEN J. , KOEHLER JODI L. , WARMAN EDUARDO N.
Published: August 2003

Atrial Defibrillation.
Introduction: The aim of this study was to identify determinants of first‐shock success for defibrillation of spontaneous atrial fibrillation (AF) in ambulatory patients with an atrial implantable cardioverter defibrillator (ICD). The determinants of first‐shock success in ambulatory patients with atrial ICDs are unknown.

Methods and Results: We used the generalized estimating equation method to analyze determinants of first‐shock success in 50 consecutive atrial ICD recipients in whom DFT+ (weakest shock that defibrillates on two consecutive trials) was determined at implant and spontaneous AF was shocked with shock strength > 2 × DFT+. DFT+ was 6.2 ± 3.1 J. Of 470 first shocks, 407 were successful (generalized estimating equation 85%, confidence interval 79% to 90%). Determinants of first‐shock success were use of coronary sinus electrode (univariate P = 0.02; multivariate P < 0.001, relative risk 5.0), absence of a Class III antiarrhythmic drug (univariate P = 0.06; multivariate P < 0.001, relative risk 3.2), absence of early recurrence of atrial fibrillation (ERAF; univariate P = 0.06; multivariate P = 0.02, relative risk 2.9), and longer duration of AF prior to shock > 3 hours (univariate: P = 0.02; multivariate P = NS). Sinus rhythm > 1 minute persisted after 93% of first shocks in patients without documented ERAF but after only 58% of shocks in patients with documented ERAF (P < 0.001).

Conclusion: Reducing ERAF is critical to achieving a clinically acceptable rate of persistent sinus rhythm after first shocks. For first shocks > 2 × DFT+, success is not increased by programming stronger shocks. Early cardioversion does not increase first‐shock success.
Large Sample Test of Defibrillation Waveform Sensitivity
Authors: MALKIN ROBERT A.
Published: August 2003

Defibrillation Waveform Sensitivity.
Introduction: An unknown mechanism causes defibrillation efficacy to be sensitive to the temporal pattern (waveform) of the delivered energy. Using a guinea pig model, we tested hypotheses in 140 defibrillation waveforms.

Methods and Results: Two hundred seven male guinea pigs (950 ± 100 g) were instrumented to continuously monitor the ECG and an optical plethysmographic signal from a forepaw. Two amplifiers served as a voltage‐based defibrillator with a maximum output of 400 V at 2 A. Defibrillation electrodes (12‐mm diameter) were placed 40 mm apart on the thorax. Thirty ventricular fibrillation episodes were induced where the first 10 episodes were used to estimate ED50 for a biphasic pulse (7/2 msec) and the remaining episodes were defibrillated with 18 test waveforms and two control waveforms all at the ED50 energy. Seven groups of 20 waveforms were tested. We directly tested hypotheses based on charge banking/burping, frequency concentration, and stimulus strength/duration. Of the hypotheses tested, nine are able to predict at least a 10% change in efficacy (P < 0.05): parabolic fit to duration; maximum, minimum, and remaining delivered charge; power at peak frequency; stimulus charge; and maximum, minimum, and maximum of the absolute value of stimulus strength. However, of these, only three are independent predictors of waveform efficacy (P < 0.05, near‐minimum residual variance): power at peak frequency; parabolic fit to the stimulus duration; and minimum stimulus strength.

Conclusion: Stimulus strength and duration are the main determinants of the efficacy of a defibrillation waveform.
Atrial Fibrillation and Congestive Heart Failure: Specific Considerations at the Intersection of Two Common and Important Cardiac Disease Sets
Authors: EHRLICH JOACHIM R. , NATTEL STANLEY , HOHNLOSER STEFAN H.
Published: August 2003

AF in Congestive Heart Failure. Atrial fibrillation (AF) and congestive heart failure (CHF) are two increasingly common cardiac disorders with a growing prevalence in the overall population. Improved treatment of acute medical conditions has increased the incidence of these cardiac disorders. AF and CHF have similar epidemiologic characteristics and adversely affect quality of life and life expectancy of affected patients. CHF predisposes to AF, and AF may worsen the prognosis of CHF. The relevant literature was intensively reviewed with emphasis on aspects at the intersection of both disease sets. Recent advances in basic research have provided a more in‐depth view of changes promoting the occurrence of AF in CHF. Data from clinical trials have provided means to improve medical treatment of AF. Precautions must be taken for specific CHF‐related side effects, such as torsades de pointes tachycardia, when treating AF. The specific electrophysiologic basis of AF associated with CHF may provide targets for improved treatment modalities. New treatment approaches, both pharmacologic and nonpharmacologic, as well as the results of ongoing controlled clinical studies are likely to greatly alter AF therapy over the next 5 to 10 years in patients with CHF.
Linear Lesions Provide Protection from Atrial Fibrillation Induction with Rapid Atrial Pacing
Authors: AVITALL BOAZ , URBONAS ARVYDAS , URBONIENE DALIA , ROZMUS GRZEGORZ , HELMS RAY
Published: August 2003

Linear Lesions Prevent Atrial Fibrillation.
Introduction: In the animal model, segmentation of the atria with radiofrequency‐generated linear lesions (LL) using the loop catheter has been shown to be highly effective in terminating chronic atrial fibrillation (AF). This study addresses the question whether the same lesion set also would prevent reinduction and sustainability of AF.

Methods and Results: We studied two groups of dogs. The AF group included eight dogs in which the atria were paced until chronic AF was present. After 6 months of sustained AF, the dogs were converted to normal sinus rhythm (NSR) by the creation of LL in both atria. Rapid atrial pacing was restarted 6 months later and continued for 4 weeks. In the NSR group, there were nine dogs in NSR without inducible AF at baseline. LL were created, and after 6 months rapid atrial pacing was applied for 4 weeks. Rhythm status was monitored weekly. Transthoracic echocardiography was performed at baseline, before linear lesion placement, and before pacing/repacing. At the conclusion of the study, the hearts were excised and examined. The lesions were stained, and their quality was assessed. AF was induced in a much shorter interval in the dogs in which AF had previously been present than in NSR dogs (8 ± 5 days vs 25 ± 13 days; P < 0.05). LL prevented sustainability of AF induced via rapid pacing once the pacing stimulus was stopped. Incomplete lesions were associated with increased inducibility of atrial tachycardia and AF.

Conclusion: In this animal model of AF, LL are not only capable of terminating chronic AF, but also lead to self‐termination of AF once the rapid pacing is stopped. Self‐termination of AF after induction with rapid pacing was not observed in this AF model in the absence of LL. In the dogs with 6 months of AF, the presence of AF led to increased atrial susceptibility to AF induction by rapid pacing, even with LL and after 6 months of recovery. Incomplete LL allows induction of atrial tachycardia and AF.
Characterization of Paroxysmal and Persistent Atrial Fibrillation in the Human Left Atrium During Initiation and Sustained Episodes
Authors: NDREPEPA GJIN , KARCH MARTIN R. , SCHNEIDER MICHAEL A.E. , WEYERBROCK SONJA , SCHREIECK JÜRGEN , DEISENHOFER ISABEL , ZRENNER BERNHARD , SCHÖMIG ALBERT , SCHMITT CLAUS
Published: August 2003

Characterization of AF in the LA.
Introduction: Atrial fibrillation (AF) in the left atrium (LA) is poorly defined in terms of regional differences in the degree of organization, characteristics of paroxysmal and persistent variants, and electrophysiologic events that develop at the onset of episodes.

Methods and Results: The study population consisted of 21 patients (15 men and 6 women; mean age 58 ± 9.4 years) with paroxysmal (10 patients) or persistent (11 patients) AF. Mapping of the LA during sustained episodes and the onset of AF was performed with a 64‐electrode basket catheter. At the onset of AF, repetitive beats starting with atrial premature complexes and ending with generation of the earliest fibrillatory activity were defined as intermediary rhythm. Patients with paroxysmal AF had longer AF cycle lengths and more pronounced regional differences than patients with persistent AF. In total, AF cycle lengths in the LA in patients with persistent AF were 20% shorter than in patients with paroxysmal AF. Initiation of AF was preceded by an intermediary rhythm of 5.5 ± 2.5 cycles (6.3 ± 2.7 cycles in paroxysmal AF vs 4.2 ± 1.0 cycles in persistent AF; P = 0.026). At the onset of AF, the earliest generators of fibrillatory activity were located more frequently in the posterior wall of the LA.

Conclusion: AF in the LA displays substantial regional differences in terms of AF cycle lengths and degree of organization. Patients with persistent AF have shorter cycle lengths and a higher degree of disorganized activity than patients with paroxysmal AF. Intermediary rhythms play an important role in initiation of AF via activation of generator regions in the LA.
How to Diagnose, Locate, and Ablate Coronary Cusp Ventricular Tachycardia
Authors: HACHIYA HITOSHI , AONUMA KAZUTAKA , YAMAUCHI YASUTERU , IGAWA MASAYUKI , NOGAMI AKIHIKO , IESAKA YOSHITO
Published: August 2003

Catheter Ablation of LVOT VT from a Coronary Cusp.
Introduction: Although radiofrequency energy usually is applied to the most favorable endocardial site in patients with outflow tract ventricular tachycardia, there are still some patients in whom the tachycardia can be ablated only from an epicardial site. We established the characteristics and technique of catheter ablation from both the left and right coronary cusps to cure left ventricular outflow tract ventricular tachycardia.

Methods and Results: We studied 15 patients in whom VT was thought to originate from the coronary cusp by both activation and pace mapping after precise mapping of the right ventricle, left ventricle, pulmonary artery, coronary cusps, and anterior interventricular vein. Twelve‐lead ECG analysis revealed an S wave on lead I, tall R wave on leads II, III, and aVF, and no S wave on either lead V5 or V6. Precordial R wave transition occurred on leads V1 and V2. The earliest ventricular electrogram at a successful ablation site was recorded 35 ± 12 msec before QRS onset and 19 ± 15 msec earlier than the earliest ventricular electrogram recorded from the anterior interventricular vein. Almost identical pace mappings were obtained from the coronary cusp. Catheter tip temperature was maintained at 55°C during energy delivery, and the distance from the tip to the ostium of each left and right coronary artery was > 1.0 cm by coronary angiography.

Conclusion: Left ventricular outflow tract VT that could not be ablated from an endocardial site could be safely eliminated by radiofrequency application to the left and right coronary cusps.