bluuebunny/crossref_metadata_2025_split huggingface dataset:
Randomized Comparison of Anatomic and Electrogram Mapping Approaches to Ablation of Typical Atrial Flutter
Authors: TADA HIROSHI , ORAL HAKAN , OZAYDIN MEHMET , CHUGH AMAN , SCHARF CHRISTOPH , HASSAN SOHAIL , GREENSTEIN RADMIRA , PELOSI FRANK , KNIGHT BRADLEY P. , STRICKBERGER S. ADAM , MORADY FRED 
Published: August 2003

Isthmus Ablation.
Introduction: The cavotricuspid isthmus can be ablated using an anatomic approach or an electrogram mapping approach in which sites at which there is a gap in the line of block are targeted. The aim of this study was to compare the anatomic and electrogram mapping approaches for creating a line of block in the cavotricuspid isthmus after an initial, unsuccessful anatomically directed ablation line. Methods and Results: The subjects of this study were 63 patients with isthmus‐dependent atrial flutter in whom a single series of contiguous applications of radiofrequency energy guided by fluoroscopy in the cavotricuspid isthmus did not result in complete block. The patients were randomly assigned to additional ablation on an anatomic basis (n = 31) or guided by single potentials or narrowly split double potentials during coronary sinus pacing (n = 32). After every 15 applications of radiofrequency energy, the alternate approach was used until complete block was achieved. Before cross‐over, complete block was achieved in 6 patients (19%) with the anatomic approach compared with 19 patients (59%) with the electrogram mapping approach (P < 0.005). The electrogram mapping approach also was more effective than the anatomic approach in achieving complete isthmus block after the first cross‐over (72% vs 23%, P < 0.005) and after the second cross‐over (80% vs 42%, P < 0.05). Conclusion: When there is incomplete block after an initial series of applications of radiofrequency energy in the cavotricuspid isthmus, complete block is achieved more efficiently with an electrogram mapping approach than with an anatomic approach.
Frequency of Symptomatic Atrial Fibrillation in Patients Enrolled in the Atrial Fibrillation Follow‐up Investigation of Rhythm Management (AFFIRM) Study
Authors: EPSTEIN ANDREW E. , VIDAILLET HUMBERTO , GREENE H. LEON , CURTIS ANNE B. , ELLENBOGEN KENNETH A. , SIMMONS TODD , MICKEL MARY 
Published: August 2003

AF Frequency.
Introduction: The frequency of symptomatic paroxysmal atrial fibrillation (AF) may identify subsets with different characteristics. Because the approach to AF now is so varied, ranging from drug therapy to surgery and catheter ablation, the frequency of AF may have important therapeutic implications if the frequency identifies subsets with distinguishing features. Methods and Results: The Atrial Fibrillation Follow‐up Investigation of Rhythm Management (AFFIRM) Study is evaluating patients with AF who are at high risk for stroke. We evaluated the clinical characteristics of the patients in the AFFIRM Study in an attempt to identify features that might distinguish patients with infrequent and frequent AF occurrences. Patients were divided into five groups, based upon the historic frequency of occurrence of AF at the time the patients were enrolled in the study. Although statistically significant differences were present among the groups, no important differences were noted in clinical or echocardiographic characteristics that could differentiate patients with frequent episodes of AF from other patients in the AFFIRM population. Conclusion: In a large population of patients with AF at high risk for stroke, individual historic and echocardiographic characteristics failed to distinguish patients based on the frequency of AF. Those with frequent and infrequent AF were similar. Although AF frequency has been suggested as a marker of a focal etiology in young populations with little overt heart disease, it does not seem to be a distinguishing characteristic in older populations at high risk for stroke.
Phase Singularities and Termination of Spiral Wave Reentry
Authors: EASON JAMES , TRAYANOVA NATALIA 
Published: August 2003

Phase Singularities and Termination of Reentry.
Introduction: Recent defibrillation studies show that electric fields interact with reentrant activity in myocardial tissue through virtual electrode polarization (VEP). This study focuses on determining how VEP relates to the creation and survival of postshock phase singularities in cardiac tissue and demonstrating that interactions between VEP and preshock tissue state engender the probabilistic nature of defibrillation. Methods and Results: We constructed a two‐dimensional tissue model representing a ventricular cross‐section with fiber architecture and surrounding bath. We initiated spiral wave reentry and subjected the tissue to a monophasic shock. We estimated the shock success probability for a given strength by testing 16 coupling intervals throughout a single rotation of the wavefront. Over a range of shock strengths, our model exhibits dose‐response behavior similar to experimental defibrillation efficacy curves. At the 50% effective strength (ED50), successful termination of reentry depends upon the interaction between preshock excitable gap and postshock phase singularities. We also found that increasing the stimulus strength toward ED50 increases the number of postshock singularities, whereas further strength increases above ED50 decrease the number of singularities. Conclusion: Our results show for the first time that a computational model can account for the probabilistic nature of defibrillation as VEP interacts with the dynamics of an ongoing reentrant wavefront. Further, we demonstrate that success of a shock depends on the annihilation of the phase singularities that arise after any strong stimulus. Our findings imply that VEP completely overrides the preshock tissue state in shocks that are highly likely to defibrillate (ED95).
Developmentally Modulated Cardiac Conduction Failure in Transgenic Mice with Fetal or Postnatal Overexpression of DNA Nonbinding Mutant Nkx2.5
Authors: WAKIMOTO HIROKO , KASAHARA HIDEKO , MAGUIRE COLIN T. , IZUMO SEIGO , BERUL CHARLES I. 
Published: August 2003

Conduction Failure in Mutant Nkx2.5 Overexpression Mice.
Introduction: Nkx2.5 is a conserved homeodomain (HD) containing transcription factor essential for early cardiac development. We generated a DNA nonbinding missense mutation, I183P in the HD, similar to the missense HD mutation found in patients. Transgenic mice expressing this mutation under β‐MHC promoter [β‐MHC(I183P)] showed a postnatal lethal phenotype with heart failure. In contrast, mice expressing the mutation under α‐MHC promoter [α‐MHC(I183P)] survive, with later onset heart failure. The aim of this study was to investigate the interrelationship between lethal cardiac failure and the electrophysiologic (EP) phenotypes using cardiac‐specific promoters with mutant gene expression at different stages of development and maturation. Methods and Results: In‐MHC(I183P) and wild‐type littermates, six‐lead ECG and in vivo endocardial EP studies were performed at 2.5, 3, 4, and 5 weeks of age. In α‐MHC(I183P) and their wild‐type controls, ECGs were acquired at 3, 19, 31, and 64 weeks and in vivo EP studies assssed at 19 ± 4 weeks of age. β‐MHC(I183P) mice display AV nodal, atrial, and ventricular EP dysfunction by 3 weeks of age. Bradycardia and PR prolongation were evident on telemetered ambulatory ECG of β‐MHC(I183P) mice. In contrast, α‐MHC(I183P) mice had no abnormalities on serial ECG through 31 weeks or EP findings at 19 weeks, except increased myocardial tissue refractoriness. However, by 64 weeks, PR intervals lengthened in α‐MHC(I183P) mice. Conclusion: Both prenatal and postnatal overexpression of DNA nonbinding mutant Nkx2.5 are associated with AV conduction malfunction and heart failure; however, more profound progressive EP defects are seen when this mutation expresses during fetal and neonatal periods. These conduction abnormalities may contribute to the lethal heart failure and early mortality evident in DNA nonbinding mutant Nkx2.5 mice.
Influence of QRS Duration on the Prognostic Value of T Wave Alternans
Authors: RASHBA ERIC J. , OSMAN AHMED F. , MACMURDY KAREN , KIRK MALCOLM M. , SARANG SAMANTHA , PETERS ROBERT W. , SHOROFSKY STEPHEN R. , GOLD MICHAEL R. 
Published: August 2003

T Wave Alternans and QRS Duration.
Introduction: T wave alternans (TWA) is a promising new noninvasive marker of arrhythmia vulnerability that quantifies beat‐to‐beat changes in ventricular repolarization. Secondary repolarization abnormalities are common in subjects with wide QRS complexes. However, the relationship between TWA and QRS prolongation has not been evaluated. The goal of this study was to determine if QRS prolongation influences the prevalence or prognostic value of TWA. Methods and Results: The study consisted of 108 consecutive patients with coronary artery disease and left ventricular ejection fraction ≤40% who were referred for electrophysiologic studies. Patients underwent TWA testing using bicycle ergometry in the absence of beta‐blockers or antiarrhythmic drugs. The primary endpoint was the combined incidence of death, sustained ventricular arrhythmias, and appropriate implantable cardioverter defibrillator therapy. The prognostic value of TWA was assessed in the entire cohort and in two subgroups: QRS < 120 msec (normal, n = 62) and QRS ≥ 120 msec (prolonged, n = 46). TWA (hazard ratio 2.2, P = 0.03) and QRS prolongation (hazard ratio 2.2, P = 0.01) were both significant and independent predictors of arrhythmic events. QRS prolongation had no effect on the prevalence of positive TWA tests (QRS < 120 msec: 48%, QRS ≥ 120 msec: 50%, P = NS). TWA was a highly significant predictor of events in patients with a normal QRS (hazard ratio 5.8, P = 0.02). In contrast, TWA was not useful for risk stratification in subjects with QRS prolongation (hazard ratio 1.1, P = 0.8). Conclusion: TWA is useful only for risk stratification in the absence of QRS prolongation. The presence of QRS prolongation and left ventricular ejection fraction ≤40% may be sufficient evidence of an adverse prognosis that additional risk stratification is not useful or necessary.
Aging‐Related Increase to Inducible Atrial Fibrillation in the Rat Model
Authors: HAYASHI HIDEKI , WANG CHARLES , MIYAUCHI YASUSHI , OMICHI CHIKAYA , PAK HUI‐NAM , ZHOU SHENGMEI , OHARA TOSHIHIKO , MANDEL WILLIAM J. , LIN SHIEN‐FONG , FISHBEIN MICHAEL C. , CHEN PENG‐SHENG , KARAGUEUZIAN HRAYR S. 
Published: August 2003

Aging and Atrial Fibrillation.
Introduction: Aging is associated with atrial interstitial fibrosis and increased incidence of atrial fibrillation (AF). We hypothesized that aged rats are suitable for study of aging‐related AF and that partial atrial cellular uncoupling induced with heptanol in young rats mimics aging‐related AF. Methods and Results: Interatrial conduction time and atrial response to burst atrial pacing were evaluated in 11 young (2–3 months) and 12 old (22–24 months) male rats (Fisher 344) in the Langendorff‐perfused setting. At baseline, sustained (>30 sec) atrial tachycardia (AT) and AF were induced in 10 of 12 and in 7 of 12 old rats, respectively. No such arrhythmias could be induced in the young rats. Old rats had significantly (P < 0.01) longer interatrial conduction time and P wave durations than the young rats. Burst pacing failed to induce AT and AF in all 11 young rats studied. The effects of heptanol 2 to 10 μM were studied in both groups. Heptanol 2 to 5 μM promoted inducible AT in all 5 young rats studied; however, when its concentration was raised to 10 μM, AT could no longer be induced in any of the 5 young rats. No AF could be induced in any of the 5 young rats at heptanol concentrations of 2 to 10 μM. In the old rats, AF could still be induced during perfusion of 2 μM heptanol. However, when its concentration was raised to 5 and 10 μM, AF could not be induced in any of the 6 old rats studied. Optical mapping using a potentiometric dye showed a periodic single wavefront of activation during AT in both groups and 2 to 4 independent wavefronts propagating in different directions during AF in the old rats. Histology revealed a significant increase in interstitial atrial fibrosis (P < 0.01), atrial cell size (P < 0.05), and heart weight in old versus young rats. Fibrosis in the old rats was highly heterogeneous. Conclusion: The rat model is suitable for study of aging‐related AF. Uniform partial atrial cellular uncoupling with heptanol perfusion in the young rats, although promoting inducible AT, does not mimic aging‐related AF. The results suggest that heterogeneous atrial interstitial fibrosis and atrial cell hypertrophy might contribute to the aging‐related increase in atrial conduction slowing, conduction block, and inducible AF in the old rat model.
Exercise is Superior to Pacing for T Wave Alternans Measurement in Subjects with Chronic Coronary Artery Disease and Left Ventricular Dysfunction
Authors: RASHBA ERIC J. , OSMAN AHMED F. , MACMURDY KAREN , KIRK MALCOLM M. , SARANG SAMANTHA , PETERS ROBERT W. , SHOROFSKY STEPHEN R. , GOLD MICHAEL R. 
Published: August 2003

Exercise vs Pacing for TWA Measurement.
Introduction: T wave alternans (TWA) is a heart rate‐dependent marker of vulnerability to ventricular arrhythmias. Atrial pacing and exercise both are used as provocative stimuli to elicit TWA. However, the prognostic value of the two testing methods has not been compared. The aim of this prospective study was to compare the prognostic value of TWA measured during bicycle exercise and atrial pacing in a large cohort of high‐risk patients with ischemic heart disease and left ventricular dysfunction. Methods and Results: This was a prospective study of 251 patients with coronary artery disease and left ventricular dysfunction who were referred for electrophysiologic studies (EPS) for standard clinical indications. Patients underwent TWA testing using bicycle ergometry (exercise TWA, n = 144) and/or atrial pacing (pacing TWA, n = 178). The primary endpoint was the combined incidence of death, sustained ventricular arrhythmias, and appropriate implantable cardioverter defibrillator therapy. The predictive value of exercise and pacing TWA for EPS results and for endpoint events was determined. Exercise and pacing TWA both were significant predictors of EPS results (odds ratios 3.0 and 2.9 respectively, P < 0.02). Kaplan‐Meier survival analysis of the primary endpoint revealed that exercise TWA was a significant predictor of events (hazard ratio 2.2, P = 0.03). In contrast, pacing TWA had no prognostic value for endpoint events (hazard ratio 1.1, P = 0.8). Conclusion: TWA should be measured during exercise when it is used for clinical risk stratification. EPS results may not be an adequate surrogate for spontaneous events when evaluating new risk stratification tests.
Randomized Comparison of Bipolar versus Unipolar Plus Bipolar Recordings During Segmental Ostial Ablation of Pulmonary Veins
Authors: TADA HIROSHI , ORAL HAKAN , KNIGHT BRADLEY P. , OZAYDIN MEHMET , CHUGH AMAN , SCHARF CHRISTOPH , HASSAN SOHAIL , GREENSTEIN RADMIRA , PELOSI FRANK , STRICKBERGER S. ADAM , MORADY FRED 
Published: August 2003

Unipolar vs Bipolar Electrograms.
Introduction: Segmental ostial ablation to isolate pulmonary veins is guided by pulmonary vein potentials. The aim of this prospective randomized study was to compare the utility of unipolar plus bipolar electrograms versus only bipolar electrograms as a guide for segmental ablation to isolate the pulmonary veins in patients with atrial fibrillation. Methods and Results: Isolation of the left superior, right superior, and left inferior pulmonary veins was attempted in 44 patients (35 men and 9 women; mean age 54 ± 10 years) with paroxysmal atrial fibrillation. A decapolar Lasso catheter was positioned in the pulmonary veins, near the ostium, and a conventional ablation catheter was used for segmental ablation aimed at elimination of all pulmonary vein potentials. One hundred fourteen pulmonary veins were randomly assigned for ostial ablation guided by either bipolar or unipolar plus bipolar recordings. Electrical isolation was achieved in 51 (96%) of 53 pulmonary veins randomized to the bipolar approach, and 57 (93%) of 61 pulmonary veins randomized to the unipolar plus bipolar approach (P = 0.7). In the unipolar plus bipolar group, the total duration of radiofrequency energy needed to achieve isolation, 5.5 ± 2.8 minutes/vein, was significant shorter than in the bipolar group, 7.6 ± 4.1 minutes/vein (P < 0.01). Mean procedure and fluoroscopy durations per vein were 19% to 28% shorter in the unipolar plus bipolar group. Conclusion: Segmental ostial ablation to isolate the pulmonary veins can be achieved more efficiently and with less radiofrequency energy when guided by both unipolar and bipolar recordings than by bipolar recordings alone.
Conduction Delay Within the Coronary Sinus in Humans: Implications for Atrial Arrhythmias
Authors: KATRITSIS DEMOSTHENES , IOANNIDIS JOHN P.A. , GIAZITZOGLOU ELEFTHERIOS , KOROVESIS SOCRATES , ANAGNOSTOPOULOS CONSTANTINE E. , CAMM A. JOHN 
Published: August 2003

Coronary Sinus Mapping.
Introduction: Striated myocardial connections between the venous wall of the coronary sinus (CS) and the left atrium have been described in humans. This aim of this study was to investigate the conduction properties and potential arrhythmogenicity of CS and left atrial myocardial connections in patients with and patients without paroxysmal atrial fibrillation (PAF). Methods and Results: Thirty‐eight patients with PAF, 52 patients with other arrhythmias, and 44 patients without arrhythmia underwent catheter mapping of the CS from the distal superoposterior part to the ostium. Catheterization of the superoposterior CS was feasible in 21, 32, and 25 subjects in the three groups, respectively (P = 0.82). Discrete double potentials or fractionated electrograms were recorded during proximal CS or right atrial pacing in 14 (66.7%), 11 (34.4%), and 5 (20.0%) patients, respectively (P = 0.004). In 29 patients, double or fractionated potentials were recorded at the distal superoposterior CS, in 3 at the mid‐CS, and in 4 at the ostium. Spontaneous or induced atrial ectopy and/or tachyarrhythmias were recorded in 18 (85.7%), 12 (37.5%), and 2 (8.0%) patients in the three groups, respectively (P < 0.001) and originated from the CS in 6, 3, and 0 patients, respectively (P = 0.010). Conclusion: Recording of double potentials is possible within the CS, particularly at its distal superoposterior part, near the left superior pulmonary vein. Their prevalence is higher in patients with PAF than in subjects with other or no arrhythmias, and their presence denotes possible sources or substrate for atrial arrhythmia.
Heterogeneous Loss of Connexin43 Protein in Nonischemic Dilated Cardiomyopathy with Ventricular Tachycardia
Authors: KITAMURA HIDETSUNA , OHNISHI YOSHIO , YOSHIDA AKIHIRO , OKAJIMA KATSUNORI , AZUMI HIROSHI , ISHIDA AKIHIKO , GALEANO ERDULFO J. , KUBO SHINYA , HAYASHI YOSHITAKE , ITOH HIROSHI , YOKOYAMA MITSUHIRO 
Published: August 2003

Connexin43 Expression in DCM.
Introduction: Gap junction alterations recently have been implicated in chronic heart failure, but direct evidence between gap junction manifestation in nonischemic dilated cardiomyopathy (DCM) is lacking. The current study examines whether qualitative changes or altered distribution of gap junctional connexin43 (Cx43) are related to global ventricular function and ventricular arrhythmia in DCM. Methods and Results: We investigated 31 DCM patients (52 ± 15 years) and 5 control subjects (55 ± 10 years). Expression of Cx43 proteins was qualitatively and quantitatively determined using immunoconfocal microscopy in right ventricular biopsy specimens from each patient. The expression level of Cx43 protein was defined as the proportion of tissue area occupied by Cx43 (percent tissue area) in each test area. Cx43 immunoreactive signal expressed as percent tissue area was not correlated with the change in left ventricular ejection fraction (P = 0.17). Of 31 DCM patients, 23% subsequently developed sustained ventricular tachycardia (VT), which allowed retrospective division of the samples into two groups: non‐VT and VT. Left ventricular ejection fraction was comparable in both groups, but the percent tissue area in the VT groups was significantly decreased compared with that of the non‐VT groups (P = 0.03). Furthermore, Cx43 protein was distributed heterogeneously in the VT groups (P < 0.0001). Conclusion: Heterogeneous reduction of Cx43 protein may result in development of malignant ventricular arrhythmia in DCM.
Phased‐Array Intracardiac Echocardiography During Pulmonary Vein Isolation and Linear Ablation for Atrial Fibrillation
Authors: MARTIN ROBERT E. , ELLENBOGEN KENNETH A. , LAU YUNG R. , HALL JEFF A. , KAY G. NEAL , SHEPARD RICHARD K. , NIXON J.V. , WOOD MARK A. 
Published: August 2003

Phased‐Array Intracardiac Echocardiography for AF Ablation.
Introduction: Fluoroscopic imaging provides limited anatomic guidance for left atrial structures. The aim of this study was to determine the utility of real‐time, phased‐array intracardiac echocardiography during radiofrequency ablation for atrial fibrillation. Methods and Results: In 29 patients undergoing pulmonary vein isolation (n = 16) or linear (n = 13) left atrial radiofrequency ablation for atrial fibrillation, intracardiac phased‐array echocardiography was used to visualize left atrial anatomy and the pulmonary veins, as well as ablation and mapping catheters during ablation procedures. In the 16 pulmonary vein isolation patients, the mean pulmonary vein ostial diameters measured by venography and intracardiac echocardiography were similar for all veins positions, except that left common pulmonary vein diameters were larger as measured by echocardiography (2.50 ± 0.29 cm) than by venography (1.79 ± 0.50 cm, P = 0.001). The ostial diameters measured by echocardiography and venography were not correlated, however (r = 0.23, P = 0.19). As directed by echocardiography, only 1 of 25 circular mapping catheters (4%) used in 16 patients was replaced due to inappropriate sizing of the pulmonary veins. Mean pulmonary vein Doppler flow velocities increased after ablation for left‐sided veins but ostial diameters were unchanged. In the linear ablation patients, the entire extent of the linear electrode array could be visualized in only 3 of 52 of catheter positions (6%) in the 13 patients. A portion of the catheter could be seen in only 50% of all target catheter positions. Conclusion: Phased‐array intracardiac echocardiography (1) allows sizing and positioning of pulmonary vein mapping catheters, (2) provides measures of pulmonary vein ostial diameters, (3) continuously monitors pulmonary vein Doppler flow velocities, and (4) has limited use in positioning linear ablation catheters in the left atrium.