bluuebunny/crossref_metadata_2025 huggingface dataset:
Pulmonary Vein Dilation in Patients with Atrial Fibrillation: Detection by Magnetic Resonance Imaging
Authors: TSAO HSUAN‐MING , YU WEN‐CHUNG , CHENG HUI‐CHENG , WU MEI‐HAN , TAI CHING‐TAI , LIN WEI‐SHIANG , DING YU‐AN , CHANG MAU‐SONG , CHEN SHIH‐ANN
Published: August 2003

Pulmonary Vein Dilation in AF.
Introduction: The positive relationship between left atrial (LA) size and atrial fibrillation (AF) is well recognized; however, there is little information on the association of pulmonary vein (PV) diameter and AF. The purpose of this study was to investigate by magnetic resonance angiography the change of PV and LA size in patients with no history of AF, patients with paroxysmal AF (PAF), and patients with chronic AF (CAF).

Methods and Results: The study included 47 patients. Group I included 15 patients with normal sinus rhythm and no history of documented AF. Group II included 24 patients with drug‐refractory PAF who underwent electrophysiologic study and radiofrequency ablation of PV foci. Group III included 8 patients with CAF who were converted to sinus rhythm by external electrical cardioversion. Age and concomitant heart diseases were similar among the three groups. We measured the diameter of each PV at its junction with the LA in addition to LA dimensions by gadolinium‐enhanced magnetic resonance angiography with three‐dimensional reconstruction. Significant dilation of both superior PVs (P < 0.01) and transverse diameter of LA (P < 0.01) was seen in the three groups. There were no significant changes of both inferior PVs, corrected PV (PV/LA) diameter, or longitudinal diameter of LA among the three groups. Only 28% patients showed arrhythmogenic foci from the largest PV.

Conclusion: Significant dilation of both superior PVs with simultaneous LA enlargement was demonstrated in PAF and CAF patients. Although PV size cannot predict AF firing, the anatomic and geometric differences may participate in perpetuation of AF.
Echocardiographic Lesion Characteristics Associated with Successful Ablation of Inappropriate Sinus Tachycardia
Authors: REN JIAN‐FANG , MARCHLINSKI FRANCIS E. , CALLANS DAVID J. , ZADO ERICA S.
Published: August 2003

Ablation for Inappropriate Sinus Tachycardia.
Introduction: Catheter ablation of inappropriate sinus tachycardia has proven difficult. Despite the use of intracardiac echocardiography to help direct radiofrequency (RF) application to the anatomic target of the superolateral crista terminalis (CT), multiple RF lesions often are required. Furthermore, the characteristic echo‐anatomic changes with RF application associated with a reduction in heart rate have not been defined. A characteristic echo signature, if present, may facilitate the ablation process. The purpose of this retrospective study was to define the echocardiographic characteristic changes associated with effective RF ablation for inappropriate sinus tachycardia.

Methods and Results: Detailed intracardiac echocardiographic imaging characterization of the superolateral CT was performed before and at the time of successful heart rate reduction. Using on‐line videotape intracardiac echocardiography (9 MHz, 9 French), changes in wall thickness and echodensity at the CT lesion site were assessed at baseline, after each RF lesion, and with the lesion that produced heart rate reduction in 17 patients (age 32 ± 9 years; 15 women) with inappropriate sinus tachycardia. In all patients, RF ablation was anatomically based and targeted only the superolateral CT. RF lesions were created using 20 to 50 W for up to 2 minutes using an 8‐mm tip electrode. Successful heart rate reduction (≥ 20 beats/min) was achieved in 15 of 17 patients and required 41 ± 31 RF applications (range 5 to 110, median 40). Effective RF (reduced heart rate) was observed starting with the 34th ± 24th lesion (range 3rd to 86th, median 25th). After effective RF, CT wall thickness was increased (11.4 ± 3.1 mm vs 7.7 ± 2.4 mm at baseline) and wall swelling expanded to adjacent superior vena cava, but the degree of thickening was not specific for effective RF associated with heart rate reduction. Importantly, we noted echodensity changes reaching directly to the epicardium with the development of a linear low echodensity or echo‐free space at the time of effective RF resulting in heart rate reduction. In two patients without effective heart rate reduction, echodensity changes never reached the epicardium. No complications (superior vena cava‐right atrial junction orifice narrowing > 50% or pericardial effusion) of RF were identified.

Conclusion: An echocardiographically guided anatomic approach to RF ablation of inappropriate sinus tachycardia is safe and effective. A characteristic echocardiographic signature suggesting transmural/epicardium damage appears to be present at the time of successful heart rate reduction and may serve as an appropriate guide for directing additional RF when using this anatomic echocardiographically based approach.
New Method for Predicting Efficiency of Heating by Measuring Bioimpedance During Radiofrequency Catheter Ablation in Humans
Authors: KO WEN‐CHIN , HUANG SHOEI K. STEPHEN , LIN JIUNN‐LEE , SHAU WEN‐YI , LAI LING‐PING , CHEN PAUL H.
Published: August 2003

Bioimpedance During Radiofrequency Catheter Ablation.
Introduction: Efficiency of heating (defined as the average temperature divided by the average power) during radiofrequency (RF) catheter ablation (RFCA) can be predicted by the electrode‐tissue contact pressure before RFCA. To predict the efficiency of heating during RFCA, we prospectively measured bioimpedance and correlated the bioimpedance with the efficiency of heating in patients undergoing RFCA for supraventricular tachycardias.

Method and Results: Of 239 RF applications in 55 patients, bioimpedance was measured from the distal pair of the electrodes of the ablation catheter using an extremely low current (10 μ A at 45 kHz). Tip electrode temperature was measured with a closed‐loop RF generator. Efficiency of heating and the difference (Δbioimpedance) between preablation bioimpedance (measured from the target ablation site) and baseline bioimpedance (measured in the right atrium without tissue contact) were calculated. There was significant positive correlation between preablation bioimpedance and efficiency of heating (regression coefficient = 0.053; P = 0.003) and between Δbioimpedance and efficiency of heating (regression coefficient = 0.067; P = 0.003). The highest degree of correlation was found during RFCA of the accessory pathways in the left free wall (regression coefficient = 0.14; P < 0.01). With preablation Δbioimpedance > 21.5 Ω, applications targeted at the left free‐wall, left posteroseptal, or right septal accessory pathways had a greater likelihood of achieving effective tissue heating (defined as maximal temperature achieved > 55°C).

Conclusion: Both preablation bioimpedance and Δ bioimpedance have positive correlation with efficiency of heating during RFCA of supraventricular tachycardia. Measuring preablation bioimpedance appears to be a useful tool for predicting the efficiency of heating during RFCA.
Shortening the Second Phase Duration of Biphasic Shocks: Effects of Class III Antiarrhythmic Drugs on Defibrillation Efficacy in Humans
Authors: MERKELY BÉLA , LUBIŃSKI ANDRZEJ , KISS ORSOLYA , HORKAY FERENC , LEWICKA‐NOWAK EVA , KEMPA MACIEJ , SZABOLCS ZOLTÁN , NYIKOS GYÖRGY , ZIMA ENDRE , ŚWIĄTECKA GRAŻYNA , GELLÉR LÁSZLÓ
Published: August 2003

Optimizing the Second Phase of Biphasic Shocks.
Introduction: The specific waveform providing optimal defibrillation threshold (DFT) is unknown. We compared the defibrillation efficacy of biphasic pulses with second phases (P2) of 2 and 5 msec in a randomized prospective clinical study.

Methods and Results: Intraoperative DFTs of 62 patients (age 54 ± 13 years; ejection fraction 43% ± 17%; amiodarone 47%, d,l‐sotalol 13%) were determined in random order using a binary search protocol. Anodal shocks of 60% tilt first phases (P1) and P2 of 2 msec/5 msec were delivered from two 100‐μ F capacitors between the right ventricular electrode and the test housing of a Phylax 06/XM device. Mean DFT was significantly lower using the shorter P2 (9.5 ± 4.5 J vs 11.3 ± 5.2 J; P < 0.0001). According to subgroup analysis, the effect of changing P2 duration was only influenced by antiarrhythmic treatment. DFT decreased markedly using the shorter P2 in patients treated with amiodarone (10.7 ± 4.9 J vs 13.4 ± 5.6 J; P < 0.00001) or d,l‐sotalol (6.1 ± 3.3 J vs 9.1 ± 4.6 J; P < 0.05). The difference in patients not treated with Class III drugs was found to be insignificant. Chronic amiodarone treatment increased DFT only when the longer P2 was used.

Conclusion: Biphasic shocks with shorter P2 should be used in patients undergoing Class III antiarrhythmic treatment.
Reduced Anisotropy of Action Potential Conduction in Left Ventricular Hypertrophy
Authors: CAREY PETER A. , TURNER MARK , FRY CHRISTOPHER H. , SHERIDAN DESMOND J.
Published: August 2003

Conduction and Left Ventricular Hypertrophy.
Introduction: The aim of this study was to determine if anisotropic action potential conduction was altered during development of left ventricular hypertrophy (LVH).

Methods and Results: Isolated guinea pig left ventricular preparations from hearts that had developed LVH were used to measure conduction velocity in longitudinal and transverse orientations to the fiber direction. A variable degree of LVH was induced by placing a ring around the ascending aorta for 50 to 250 days. Results were compared with an age‐matched control group that underwent a similar operation but with no ring placement. LVH was measured as the heart‐to‐body‐weight ratio (HBR), which correlated with an increase of mean myocyte cross‐sectional area. Longitudinal conduction velocity (LCV) declined progressively as HBR increased (mean ± SD: sham vs LVH: HBR 3.74 ± 0.30 g/kg vs 4.53 ± 0.52 g/kg; LCV 72.8 ± 15.5 vs 63.6 ± 11.1 cm/sec). Mean transverse conduction velocity (TCV) was greater in LVH compared with control (20.5 ± 4.7 cm/sec vs 25.4 ± 8.1 cm/sec), but there was no significance in the trend as a function of HBR. The anisotropic ratio (LCV/TCV) significantly declined as HBR increased. The time constant of the foot of the action potential was smaller in the transverse compared with the longitudinal dimension. There was no influence of hypertrophy.

Conclusion: The decrease of LCV and reduction of the anisotropic conduction ratio suggest remodeling of the tissue in LVH. The consequences for the generation of arrhythmias are discussed.
Spontaneous Right Ventricular Outflow Tract Tachycardia in a Patient with Brugada Syndrome
Authors: OGAWA MASAHIRO , KUMAGAI KOICHIRO , SAKU KEIJIRO
Published: August 2003

RVOT Tachycardia in Brugada Syndrome. We report the case of a 28‐year‐old man with no structural heart disease, who exhibited clearly augmented ST segment elevation in the right precordial leads, followed by induction of spontaneous right ventricular outflow tract tachycardia with intravenous administration of Class IA antiarrhythmic drugs. The electrophysiologic mechanism of this tachycardia was thought to be triggered activity due to delayed afterdepolarizations. Due to the existence of substrates that were similar to Brugada syndrome combined with right ventricular outflow tract tachycardia, this case may represent a subtype of Brugada syndrome.
On the Neural Connection
Authors: LATHROP DAVID A. , SPOONER PETER M.
Published: August 2003

On the Neural Connection Discoveries concerning cardiac neural‐electrical modulation and local neural remodeling provide powerful new approaches for the development of novel antiarrhythmic strategies. This “view” of developments in this emerging field highlights recent advances and suggests that additional neurally targeted investigations have considerable potential for prevention of arrhythmic diseases.
Classification of Atrial Flutter and Regular Atrial Tachycardia According to Electrophysiologic Mechanism and Anatomic Bases: A Statement from a Joint Expert Group from the Working Group of Arrhythmias of the European Society of Cardiology and the North American Society of Pacing and Electrophysiology
Authors: SAOUDI NADIR , COSIO FRANCISCO , WALDO ALBERT , CHEN SHIH‐ANN , IESAKA YOSHITO , LESH MICHAEL , SAKSENA SANJEEV , SALERNO JORGE , SCHOELS WOLFGANG
Published: August 2003

New Classification of Atrial Tachycardia. Regular atrial tachycardias classically are classified into flutter or tachycardia, depending on the rate and presence of a stable baseline on the ECG. However, current understanding of electrophysiology atrial tachycardias makes this classification obsolete, because it does not correlate with mechanisms. The proposed classification is based on electrophysiologic mechanisms, defined by mapping and entrainment. Radiofrequency ablation of a critical focus or isthmus can afford proof. Focal tachycardias are characterized by radial spread of activation and endocardial activation not covering the whole cycle. Ablation of the focus of origin interrupts the tachycardia. The mechanism of focal firing is difficult to ascertain by clinical methods. Macroreentrant tachycardias are characterized by circular patterns of activation that cover the whole cycle. Fusion can be shown during entrainment on the ECG or by multiple endocardial recordings. Ablation of a critical isthmus interrupts the tachycardia. Macroreentry can occur around normal structures (terminal crest, eustachian ridge) or around atrial lesions. The anatomic bases of these tachycardias must be defined, to guide appropriate treatment. Atrial flutter is a mere description of continuous undulation on the ECG, and only some strictly defined typical flutter patterns correlate with right atrial macroreentry bounded by the tricuspid valve, terminal crest, and caval vein orifices. This classification should be considered open, as some classically described tachycardias, such as reentrant sinus tachycardia, inappropriate sinus tachycardia, and type II atrial flutter, cannot be classified accurately. Furthermore, the possibility of fibrillatory conduction makes the limits with atrial fibrillation still ill defined.
Atrial Size Reduction as a Predictor of the Success of Radiofrequency Maze Procedure for Chronic Atrial Fibrillation in Patients Undergoing Concomitant Valvular Surgery
Authors: CHEN MIEN‐CHENG , CHANG JEN‐PING , GUO G. BIH‐FANG , CHANG HSUEH‐WEN
Published: August 2003

Radiofrequency Maze Procedure and Atrial Size.
Introduction: Previous studies showed that the surgical maze procedure can restore sinus rhythm and atrial transport function in patients with chronic atrial fibrillation (AF). However, no previous studies discussed the association of atrial size reduction and the success of sinus conversion by the radiofrequency (RF) maze procedure for chronic AF.

Methods and Results: A total of 119 chronic AF patients undergoing valvular operations were included in this study. Sixty‐one patients received RF and cryoablation to create lesions in both atria to simulate the surgical maze II or III procedure (RF maze II or RF maze III; 13 patients, group 1) or a modified maze pattern (RF maze “IV”; 48 patients, group 2). The other 58 patients who underwent valvular operations alone without the maze procedure served as control (group 3). At 3‐month follow‐up after operation, sinus rhythm was restored in 73%, 81%, and 11% of patients in groups 1, 2 and 3, respectively. Preoperative left and right atrial sizes were not statistically significant predictors of sinus conversion by the RF maze procedure. However, as a result of postoperative reduction of atrial sizes, postoperative left atrial diameter was significantly smaller in patients who had sinus conversion by the RF maze procedure than in patients who did not regain sinus rhythm (45.0 ± 7.0 mm vs 51.0 ± 8.0 mm; P = 0.03). Postoperative right atrial area of patients who had sinus conversion by the RF maze procedure also was significantly smaller than that of patients who did not regain sinus rhythm (18.1 ± 4.4 cm2 vs 28.5 ± 8.2 cm2; P = 0.008).

Conclusion: Atrial size reduction appears to predict the success of sinus conversion with the RF maze procedure used in conjunction with valvular surgery.
Increased Levels of Tissue Plasminogen Activator Antigen and Factor VIII Activity in Nonvalvular Atrial Fibrillation: Relation to Predictors of Thromboembolism
Authors: WANG TZUNG‐DAU , CHEN WEN‐JONE , SU SOPHIA SEH‐YI , SU TA‐CHEN , CHEN MING‐FONG , LIAU CHIAU‐SUONG , LEE YUAN‐TEH
Published: August 2003

Atrial Fibrillation and Hypercoagulability.
Introduction: Given that nonvalvular atrial fibrillation (AF)‐associated stroke can be either cardioembolic or atherothrombotic, we investigated the relationships between nonvalvular AF and hemostatic factors reflecting intrinsic thrombogenic and atherogenic potentials (tissue plasminogen activator [t‐PA] antigen, plasminogen activator inhibitor‐1, and factor VIII activity). We also evaluated the clinical applicability of these hemostatic factors by examining whether AF subjects with established clinical or echocardiographic predictors of thromboembolism had higher levels of these factors.

Methods and Results: Of the 3,212 participants of a Chinese population‐based study, 53 subjects (1.7%) with AF were identified. Among the hemostatic factors measured, t‐PA antigen (median 12.8 vs 8.1 ng/mL; P < 0.01) and factor VIII activity (median 155% vs 133%; P < 0.05) were significantly higher in AF subjects after adjustment for age and sex. In multivariate analysis, features independently associated with t‐PA antigen levels were AF, age, sex, body mass index, systolic blood pressure, total cholesterol, triglycerides, and left ventricular systolic dysfunction. Features independently associated with factor VIII activity levels included AF, age, and total cholesterol. Levels of both t‐PA antigen and factor VIII activity were primarily elevated in AF subjects with predictors of thromboembolism (age > 75 years, hypertension, diabetes, and left ventricular systolic dysfunction), whereas in AF subjects with no thromboembolic predictors, plasma levels of hemostatic factors examined were similar to those without AF.

Conclusion: We demonstrated that nonvalvular AF was independently associated with increased peripheral levels of t‐PA antigen and factor VIII activity. Levels of both hemostatic factors were primarily elevated in AF subjects with predictors of thromboembolism. Whether these hemostatic factors are independently predictive of future thromboembolic events in AF patients requires further investigation.
Acquired Pulmonary Vein Stenosis after Radiofrequency Catheter Ablation of Paroxysmal Atrial Fibrillation
Authors: YU WEN‐CHUNG , HSU TSUI‐LIEH , TAI CHING‐TAI , TSAI CHIN‐FENG , HSIEH MING‐HSIUNG , LIN WEI‐SHIANG , LIN YUNG‐KUO , TSAO HSUAN‐MING , DING YU‐AN , CHANG MAU‐SONG , CHEN SHIH‐ANN
Published: August 2003

PV Stenosis after AF Ablation.
Introduction: Elimination of the initiating focus within the pulmonary vein (PV) using radiofrequency (RF) catheter ablation is a new treatment modality for treatment of drug‐refractory atrial fibrillation. However, information on the long‐term safety of RF ablation within the PV is limited.

Methods and Results: In 102 patients with drug‐refractory atrial fibrillation and at least one initiating focus from the PV, series transesophageal echocardiography was performed to monitor the effect of RF ablation on the PV. There were 66 foci in the right upper PV and 65 foci in the left upper PV. Within 3 days of ablation, 26 of the ablated right upper PVs (39%) had increased peak Doppler flow velocity (mean 130 ± 28 cm/sec, range 106 to 220), and 15 of the ablated left upper PVs (23%) had increased peak Doppler flow velocity (mean 140 ± 39 cm/sec, range 105 to 219). Seven patients had increased peak Doppler flow velocity in both upper PVs. No factor (including age, sex, site of ablation, number of RF pulses, pulse duration, and temperature) could predict PV stenosis after RF ablation. Three patients with stenosis of both upper PVs experienced mild dyspnea on exertion, but only one had mild increase of pulmonary pressure. There was no significant change of peak and mean flow velocity and of PV diameter in sequential follow‐up studies up to 16 (209 ± 94 days) months.

Conclusion: Focal PV stenosis is observed frequently after RF catheter ablation applied within the vein, but usually is without clinical significance. However, ablation within multiple PVs might cause pulmonary hypertension and should be considered a limiting factor in this procedure.
Activation Patterns in the Left Atrium During Counterclockwise and Clockwise Atrial Flutter
Authors: NDREPEPA GJIN , ZRENNER BERNHARD , WEYERBROCK SONJA , SCHNEIDER MICHAEL A.E. , SCHMITT CLAUS
Published: August 2003

Activation of the LA During Atrial Flutter.
Introduction: Activation of the left atrium (LA) in patients with isthmus‐dependent right atrial flutter (AFL) has not yet been studied. The aim of this study was to analyze the activation patterns in the LA in patients with counterclockwise and clockwise AFL.

Methods and Results: The study population consisted of 12 patients (10 men and 2 women; mean age 61 ± 13 years) with documented AFL and atrial fibrillation referred for ablation. The LA was mapped with a 64‐electrode basket catheter inserted through a transseptal approach (10 patients) or an open foramen ovale (2 patients). In patients with counterclockwise AFL (10 episodes), the LA was activated for a mean of 133 ± 28 msec. Two endocardial breakthroughs of earliest activity on the left side of the interatrial septum, separated in time by an interval of 38 ± 15 msec, were observed in 9 episodes (90%). Two wavefronts originated from these breakthroughs, which activated the posterior and the anterior LA walls, respectively. In one patient, the entire LA was activated from the inferior breakthrough. In patients with clockwise AFL (five episodes), the LA activation time was 130 ± 13 msec. During ongoing episodes, two early electrical breakthroughs, separated in time by an interval of 41 ± 15 msec, appeared in the high anteroseptal and low posteroseptal LA regions. The superior wavefront that emerged from the high anterolateral LA region was the dominant activation pathway in 4 (80%) of 5 episodes.

Conclusion: In patients with AFL, the LA is activated by two wavefronts originating from the high anterior and the low posterior regions of the interatrial septum. The sequence of activation of these interatrial connections in counterclockwise or clockwise AFL and the conductive properties of the LA conduction pathways determine the activation patterns in the LA.
Clinical Outcome after Radiofrequency Catheter Ablation of Focal Atrial Fibrillation Triggers
Authors: GERSTENFELD EDWARD P. , GUERRA PETER , SPARKS PAUL B. , HATTORI KYOKO , LESH MICHAEL D.
Published: August 2003

Ablation of Focal Atrial Fibrillation.
Introduction: Ablative therapy for atrial fibrillation (AF) by targeting initiating triggers, usually in or around the pulmonary veins, has been reported by several centers. Evidence for an overall improvement in quality of life (QOL) and amelioration of symptoms is lacking.

Methods and Results: Seventy‐one patients undergoing attempted ablation of focal AF were followed for 60 ± 33 weeks. QOL and symptom questionnaires were completed 1 month before and 6 months after electrophysiologic study. Twenty‐three patients (32%) underwent electrophysiologic mapping but no ablation because of either insufficient or multifocal ectopy; the other 48 patients (68%) underwent attempted ablation. Sixteen of 48 patients (33%) undergoing ablation, or 16 (23%) of 71 on an intention to‐treat basis, were found at last follow‐up to have persistent sinus rhythm without antiarrhythmic drugs. Patients who underwent mapping without ablation reported no improvements in any QOL or symptom score, whereas patients who had long‐term successful ablation had significant improvements in all six QOL measures. Interestingly, patients who developed AF recurrence after ablation still reported significant improvements in 4 of 6 QOL measures. Four of 48 patients (8.3%) undergoing ablation developed pulmonary vein stenosis.

Conclusion: Paroxysmal AF can be treated successfully in some patients by ablating initiating triggers in the pulmonary veins; however, in our experience the recurrence rate (32/48 [68%]) and risk of pulmonary vein stenosis (8%) after ablation are high. Patients with recurrent AF after ablation of focal AF triggers have significant improvement in QOL and symptoms compared with before ablation. Patients and their physicians should carefully balance the risks and benefits before considering ablation.
Prevention of Chronic Atrial Fibrillation by Pacing in the Region of Bachmann's Bundle: Results of a Multicenter Randomized Trial
Authors: BAILIN STEVEN J. , ADLER STUART , GIUDICI MICHAEL
Published: August 2003

Bachmann's Bundle Pacing for AF Prevention.
Introduction: Atrial pacing locations that decrease atrial activation and recovery time may be preferable in patients with a history of atrial arrhythmias. This multicenter prospective randomized study compared the efficacy of Bachmann's bundle (BB) region pacing to right atrial appendage (RAA) pacing in patients with recurrent paroxysmal atrial fibrillation (AF).

Methods and Results: Patients with standard pacing indications (n = 120, 70 ± 11 years) were randomized to atrial pacing in either the RAA (n = 57) or BB region (n = 63). Implantation time was similar between groups (88 ± 36 min[n = 38] for BB vs 83 ± 34 min [n = 34] for RAA). No differences in pacing threshold, impedance, or sensing between BB and RAA groups were observed at implantation or after the 6‐week, 6‐month, and 1‐year follow‐up periods. Average length of follow‐up was 12.6 ± 7.4 months for the BB group and 11.8 ± 8.0 months for the RAA pacing group. The percentage of atrial pacing was similar between groups (61% ± 34% RAA vs 65% ± 31% BB at 2 weeks after implant). BB atrial pacing significantly (P < 0.05) shortened p wave duration compared with sinus rhythm (123 ± 21 msec vs 132 ± 21 msec, n = 50) 2 weeks after implant. In contrast, p wave duration was longer during atrial pacing from the RAA position compared with sinus rhythm (148 ± 23 msec vs 123 ± 23 msec, n = 37). Additionally, p wave duration was shorter during BB pacing than during RAA pacing. Patients with BB pacing had a higher (P < 0.05) rate of survival free from chronic AF (75%) compared with patients with RAA pacing (47%) at 1 year.

Conclusion: BB region pacing is safe and effective for attenuating the progression of AF.
Defibrillation Efficacy Comparing a Subcutaneous Array Electrode versus an “Active Can” Implantable Cardioverter Defibrillator and a Subcutaneous Array Electrode in Addition to an “Active Can” Implantable Cardioverter Defibrillator: Results from Active Can versus Array Trials I and II
Authors: GRADAUS RAINER , BLOCK MICHAEL , SEIDL KARLHEINZ , BRUNN JÜRGEN , ISGRO FRANK , HAMMEL DIETER , HAUER BERND , BREITHARDT GÜNTER , BÖCKER DIRK
Published: August 2003

Defibrillation Efficacy.
Introduction: Placement of implantable cardioverter defibrillators (ICDs) has been simplified by using the shell of a pectorally implanted ICD as a defibrillation electrode in combination with an endocardial right ventricular defibrillation lead. However, a sufficiently low defibrillation threshold (DFT) cannot be obtained in a few patients. Therefore, alternative approaches were systematically tested in the Active Can versus Array Trial (ACAT).

Methods and Results: In the first of two prospective randomized studies, the DFT of a subcutaneous left dorsolateral array anode introduced from a pectoral incision was compared to that of a standard active can anode in 68 patients. Intraoperatively, the DFT was determined twice in each patient using either the active can or, in patients with a subcutaneous array lead, once with all three fingers and once omitting the middle finger of the array. The second prospective randomized study included 40 patients. DFT also was determined twice in each patient using an active can in a left pectoral position as anode alone and combined with a left dorsolateral array electrode with two fingers. In ACAT I, stored energy at DFT decreased from 13.1 ± 7.7 J (active can) to 9.6 ± 6.1 J (three‐finger array lead) (P = 0.04), impedance decreased from 53 ± 8 Ω to 40 ± 6 Ω (P < 0.0001). Omitting the middle finger of the array lead, stored energy at DFT increased by 0.9 J (P = 0.47) and impedance by 2 Ω (P < 0.0001). In ACAT II, DFT and impedance using an active can device were significantly lower when a two‐finger array lead was added that decreased stored energy at DFT from 10.1 ± 5.2 J to 6.9 ± 3.9 J (P = 0.001) and impedance from 56 ± 5 Ω to 42 ± 5 Ω (P < 0.0001).

Conclusion: In combination with a right ventricular defibrillation electrode, a left pectoral subcutaneous array lead improves defibrillation efficacy if used instead of, or in addition to, a left pectoral active can ICD device. Implantation of the array lead can be simplified by using two instead of three fingers, without a significant loss of defibrillation efficacy.
Electrophysiologic Characteristics of Ventricular Extrastimulation‐Induced Dissipation of Functional Bundle Branch Block Associated with Supraventricular Tachycardia
Authors: WANG SHANE HAW , HAN JENNIFER , HOU CHARLES , SUNG RUEY J.
Published: August 2003

Dissipation of Functional Bundle Branch Block.
Introduction: Linking‐related anterograde functional bundle branch block during supraventricular tachycardia (SVT) is due to repetitive concealed retrograde conduction of impulses from the contralateral bundle branch and can be eliminated by a critically timed premature ventricular beat (PVB). We assessed the electrophysiologic characteristics of PVB‐induced dissipation of functional bundle branch block during SVT.

Methods and Results: During SVT with functional bundle branch block, PVB was delivered from the right ventricular apex, scanning the tachycardia cycle length (CL) with 10‐msec decrements in the coupling interval in 14 patients (3 AV nodal reentrant tachycardia and 11 orthodromic AV reciprocating tachycardia). Dissipation was achieved in group 1: functional right bundle branch block (RBBB) in 4, functional left bundle branch block (LBBB) in 4, and both functional RBBB and LBBB in 1 with a dissipation zone occupying 4% to 13% (mean 8.5%) of the tachycardia CL. The outer limits were 22 ± 16 msec and 68 ± 14 msec < tachycardia CL; the inner limits were 56 ± 18 msec and 90 ± 24 msec < tachycardia CL for RBBB and LBBB, respectively (both P < 0.05). Dissipation could not be achieved in group 2 (4 RBBB and 1 LBBB) due to CL‐dependent bundle branch block and/or local ventricular refractoriness.

Conclusion: During SVT, functional bundle branch block due to “linking” often can be dissipated by timely PVB delivered from the right ventricular apex within a narrow zone of the tachycardia CL. Our findings suggest that the dissipation zone is affected by the pattern of functional bundle branch block relative to the site of PVB delivery.
Usefulness of Midodrine in Patients with Severely Symptomatic Neurocardiogenic Syncope: A Randomized Control Study
Authors: PEREZ‐LUGONES ALEJANDRO , SCHWEIKERT ROBERT , PAVIA STEPHEN , SRA JASBIR , AKHTAR MASOOD , JAEGER FREDRICK , TOMASSONI GERY F. , SALIBA WALID , LEONELLI FABIO M. , BASH DIANNA , BEHEIRY SALWA , SHEWCHIK JEANNE , TCHOU PATRICK J. , NATALE ANDREA
Published: August 2003

Midodrine for Neurocardiogenic Syncope.
Introduction: The efficacy of midodrine for the management of patients with neurocardiogenic syncope was assessed prospectively in a randomized control study.

Methods and Results: Patients who had at least monthly occurrences of syncope and a positive tilt‐table test were included in the study. A total of 61 patients were randomly allocated to treatment either with midodrine or with fluid, salt tablets, and counseling. Midodrine was given at a starting dose of 5 mg three times a day and increased up to a dose of 15 mg three times a day when required. Midodrine was given during the daytime every 6 hours. Thirty‐one patients were assigned to treatment with midodrine; the other 30 patients were advised to increase their fluid intake and were instructed to recognize their prodromes and abort the progression to syncope. Patients were followed‐up for at least 6 months. A quality‐of‐life questionnaire was administered at the time of randomization and 6 months after. At the 6‐month follow‐up, 25 (81%) of 31 midodrine‐treated patients and 4 (13%) of the 30 fluid‐therapy patients had remained asymptomatic (P < 0.001). One patient had to discontinue taking midodrine due to severe side effects and another six patients experienced minor side effects that did not require drug discontinuation.

Conclusion: Midodrine appeared to provide a significant benefit in patients with neurocardiogenic syncope. To prevent recurrence of symptoms, dose adjustments were required in about one third of patients.
Prolongation of Activation‐Recovery Interval over a Preexcited Region before and after Catheter Ablation in Patients with Wolff‐Parkinson‐White Syndrome
Authors: INDEN YASUYA , HIRAI MAKOTO , TAKADA YASUNOBU , SHIMIZU ATSUYA , SHIMOKATA KEIKO , YOSHIDA YUKIHIKO , AKAHOSHI MAKOTO , KONDO TAKAHISA , SAITO HIDEHIKO
Published: August 2003

Activation‐Recovery Interval in WPW Syndrome.
Introduction: Preexisting changes in repolarization properties play an important role in T wave abnormalities (cardiac memory) after ablation in patients with Wolff‐Parkinson‐White (WPW) syndrome. However, no report has provided direct evidence for prolongation of action potential duration (APD) over a preexcited region before and after ablation.

Methods and Results: We studied 10 patients with ventricular preexcitation due to a left‐sided accessory pathway (AP) (group M) and 12 patients with concealed left‐sided AP (group C) to clarify prolongation of APD using activation‐recovery intervals (ARIs) from epicardial and endocardial unipolar electrograms in patients with WPW syndrome. ARI was calculated from unipolar electrograms at the His bundle and the coronary sinus adjacent to the AP during atrial pacing (100 beats/min) before and 30 minutes after ablation. Before ablation, ARIs at the AP site were significantly longer in group M than in group C (255 ± 21 msec vs 211 ± 24 msec; P < 0.01), whereas ARIs at the His bundle did not differ between the two groups (255 ± 20 msec vs 245 ± 27 msec; P = NS). After ablation, group M showed no significant changes in ARIs at the AP and His bundle (256 ± 19 msec and 253 ± 15 msec) compared with before ablation.

Conclusion: We found by direct analysis of ARIs from the epicardium that APD prolongation over the preexcited region was present before catheter ablation and persisted after catheter ablation. The gradual changes in repolarization properties, including APD prolongation after discontinuation of AP, may be one mechanism of cardiac memory after catheter ablation in patients with WPW syndrome.
Virtual Electrode Polarization Leads to Reentry in the Far Field
Authors: LINDBLOM ANNETTE E. , AGUEL FELIPE , TRAYANOVA NATALIA A.
Published: August 2003

Virtual Electrode Polarization.
Introduction: Our previous article examined cardiac vulnerability to reentry in the near field within the framework of the virtual electrode polarization (VEP) concept. The present study extends this examination to the far field and compares its predictions to the critical point hypothesis.

Methods and Results: We simulate the electrical behavior of a sheet of myocardium using a two‐dimensional bidomain model. The fiber field is extrapolated from a set of rabbit heart fiber directions obtained experimentally. An S1 stimulus is applied along the top or left border. An extracellular line electrode on the top delivers a cathodal or anodal S2 stimulus. A VEP pattern matching that seen experimentally is observed and covers the entire sheet, thus constituting a far‐field effect. Reentry arises from break excitation, make excitation, or a combination of both, and subsequent propagation through deexcited and recovered areas. Reentry occurs in cross‐field, parallel‐field, and uniform refractoriness protocols. For long coupling intervals (CIs) above CImakemin (defined as the shortest CI at which make excitation can take place), rotors move away from the cathodal electrode and the S1 site for increases in S2 strength and CI, respectively. For cathodal S2 stimuli, findings are consistent with the critical point hypothesis. For CIs below CImakemin, reentry is initiated by break excitation only, and the resulting reentrant patterns are no longer consistent with those predicted by the critical point hypothesis.

Conclusion: Shock‐induced VEP can explain vulnerability in the far field. The VEP theory of vulnerability encompasses the critical point hypothesis for cathodal S2 shocks at long CIs.
Atrial Defibrillation Thresholds of Electrode Configurations Available to an Atrioventricular Defibrillator
Authors: BENSER MICHAEL E. , WALCOTT GREGORY P. , KILLINGSWORTH CHERYL R. , GIROUARD STEVEN D. , MORRIS MILTON M. , IDEKER RAYMOND E.
Published: August 2003

Atrial Defibrillation Thresholds.
Introduction: Little investigation has been conducted to assess the atrial defibrillation thresholds of electrode configurations using electrodes designed for internal ventricular defibrillation (right ventricle [RV], superior vena cava [SVC], and pulse generator housing [Can]) combined with coronary sinus (CS) electrodes. We hypothesized that a CS → SVC+Can electrode configuration would have a lower atrial defibrillation threshold than a standard configuration for defibrillation, RV → SVC+Can. We also tested the atrial defibrillation thresholds of five other configurations.

Methods and Results: In 12 closed chest sheep, we situated a two‐coil (RV, SVC) defibrillation catheter, a left‐pectoral subcutaneous Can, and a CS lead. Atrial fibrillation was burst induced and maintained with continuous infusion of intrapericardial acetyl‐β‐methylcholine chloride. Using fixed‐tilt biphasic shocks, we determined the atrial defibrillation thresholds of seven test configurations in random order according to a multiple‐reversal protocol. The peak voltage and delivered energy atrial defibrillation thresholds of CS → SVC+Can (168 ± 67 V, 2.68 ± 2.40 J) were significantly lower than those of RV → SVC+Can (215 ± 88 V, 4.46 ± 3.40 J). The atrial defibrillation thresholds of the other test configurations were RV+CS → SVC+Can 146 ± 59V, 1.92 ± 1.45 J; RV
 → CS+SVC+Can:191 ± 89V, 3.53 ± 3.19 J; CS → SVC: 188 ± 98V, 3.77 ± 4.14 J; SVC → CS+Can: 265 ± 145 V, 7.37 ± 9.12 J; and SVC → Can: 516 ± 209 V,
 24.5 ± 15.0 J.

Conclusions: The atrial defibrillation threshold of CS → RV SVC+Can. In addition, the low atrial defibrillation threshold of RV+CS → SVC+Can merits further investigation. Based on corroboration of low atrial defibrillation thresholds of CS‐based configurations in humans, physicians might consider using CS leads with atrioventricular defibrillators.
His‐Bundle Parasystole Masquerading as Exercise‐Induced 2:1 Atrioventricular Block
Authors: KASAOKA YUJI , AJIKI KOHSUKE , HAYAMI NORIYUKI , MURAKAWA YUJI
Published: August 2003

His‐Bundle Parasystole. We describe a case of symptomatic pseudo‐AV block due to His‐bundle parasystole masquerading as exercise‐induced 2:1 AV block. Electrophysiologic study revealed the presence of His‐bundle parasystole, and the fluctuation of parasystolic cycle length could be explained by the concept of modulated parasystole. Modulated parasystole is a possible explanation for maintenance of stable 2:1 AV conduction at an atrial rate of specific range during exercise.
Demonstration of the Reentrant Circuit of Verapamil‐Sensitive Idiopathic Left Ventricular Tachycardia: Direct Evidence for Macroreentry as the Underlying Mechanism
Authors: MARUYAMA MITSUNORI , TADERA TAKESHI , MIYAMOTO SHINJIRO , INO TAKESHI
Published: August 2003

Reentrant Circuit of Idiopathic LV Tachycardia. The exact reentrant circuit of verapamilsensitive idiopathic left ventricular tachycardia (ILVT) remains unclear. This case report demonstrates the reentrant circuit of ILVT. A 20‐pole electrode catheter was placed along the left posterior fascicle during electrophysiologic study. ILVT was reproducibly induced by programmed ventricular stimulation. During the tachycardia, sequential diastolic potentials bridging the entire diastolic period were observed in the recordings from the electrodes positioned from left ventricular mid‐septum to inferoapical septum. The slow conduction zone appeared to be composed of a false tendon in this patient. Entrainment of the ILVT from the right ventricular outflow tract at a different pacing cycle length revealed that a dominant conduction delay occurred at the proximal site of the slow conduction zone. Entrainment studies from several sites on the left ventricular septum confirmed that these sites where sequential electrical activity was recorded were included within the reentrant circuit. However, the left posterior fascicle itself seemed to be a bystander. This report provides the direct evidence of macroreentry as the underlying mechanism of this ILVT, adjacent to the left posterior fascicle.
Mechanism of Ventricular Arrhythmias in the Long QT Syndrome: On Hermeneutics
Authors: EL‐SHERIF NABIL
Published: August 2003

VT Mechanisms in LQTS. Both the congenital and acquired long QT syndrome are due to abnormalities (intrinsic and/or acquired) of the ionic currents underlying repolarization. The prolongation of repolarization acts as a priming step for the generation of early afterdepolarizations. In the long QT syndrome, it also is associated with increased dispersion of repolarization. Focal early afterdepolarization‐induced triggered beat(s) can infringe on the underlying substrate of inhomogeneous repolarization to initiate polymorphic reentrant ventricular tachycardia that sometimes has a characteristic twisting of the QRS axis, referred to as torsades de pointes.
Relationship Between Rehospitalization and Future Death in Patients Treated for Potentially Lethal Arrhythmia
Authors: HALLSTROM ALFRED P. , GREENE H. LEON , WILKOFF BRUCE L. , ZIPES DOUGLAS P. , SCHRON ELEANOR , LEDINGHAM ROBERT B.
Published: August 2003

Rehospitalization and Future Death.
Introduction: It is generally considered that death is the only appropriate endpoint to evaluate interventions for preventing death; however, this belief may be based on the previous use of inappropriate or inadequate surrogates for death. The aim of this study was to evaluate whether rehospitalization following implementation of an intervention is a reasonable surrogate for death.

Methods and Results: The time from discharge following intervention to rehospitalization was evaluated for 997 patients discharged after baseline hospitalization in the Antiarrhythmics Versus Implantable Defibrillators Trial. The relationship between rehospitalization for various reasons and subsequent death was compared in the two treatment arms to assess the adequacy of rehospitalization as a surrogate for death. Included were rehospitalization for: any reason, a cardiac problem, a noncardiac problem, new or worsened congestive heart failure (CHF), an acute coronary syndrome, and a cardiac procedure. For all of the reasons except cardiac procedure, rehospitalization was associated with a substantially increased hazard for subsequent death. Rehospitalization for new or worsened CHF was most closely (that is, temporally) related to subsequent death and was the only reason for rehospitalization, which fully explained the treatment effect of implantable cardiac defibrillators compared with antiarrhythmic drugs on death.

Conclusion: Rehospitalization is a significant risk factor for subsequent death. However, only rehospitalization for new or worsened CHF appears to be a potential surrogate for death in the setting of antiarrhythmic interventions.
Prognostic Value of Electrophysiologic Investigations in Brugada Syndrome
Authors: BRUGADA PEDRO , GEELEN PETER , BRUGADA RAMON , MONT LLUIS , BRUGADA JOSEP
Published: August 2003

Brugada Syndrome.
Introduction: The prognostic value of electrophysiologic investigations in individuals with Brugada syndrome is unclear. Previous studies failed to determine its value because of a limited number of patients or lack of events during follow‐up. We present data on the prognostic value of electrophysiologic studies in the largest cohort ever collected of patients with Brugada syndrome.

Methods and Results: Two hundred fifty‐two individuals with an ECG diagnostic of Brugada syndrome were studied electrophysiologically. The diagnosis was made because of a classic ECG with a coved‐type ST segment elevation in precordial leads V1 to V3. Of the 252 individuals, 116 had previously developed spontaneous symptoms (syncope or aborted sudden cardiac death) and 136 were asymptomatic at the time of diagnosis. A sustained ventricular arrhythmia was induced in 130 patients (51%). Symptomatic patients were more frequently inducible (73%) than asymptomatic individuals (33%) (P = 0.0001). Fifty‐two individuals (21%) developed an arrhythmic event during a mean follow‐up of 34 ± 40 months. Inducibility was a powerful predictor of arrhythmic events during follow‐up both in symptomatic and asymptomatic individuals. Overall accuracy of programmed ventricular stimulation to predict outcome was 67%. Overall accuracy in asymptomatic individuals was 70.5%, with a 99% negative predictive value. Overall accuracy in symptomatic patients was 62%, with only a 4.5% false‐negative rate. No significant differences were found in the duration of the H‐V interval during sinus rhythm between symptomatic or asymptomatic individuals. However, the H‐V interval was significantly longer in the asymptomatic individuals who became symptomatic during follow‐up compared with those who did not develop symptoms (59 ± 8 msec vs 48 ± 11 msec, respectively; P = 0.04).

Conclusion: Inducibility of sustained ventricular arrhythmias is a good predictor of outcome in Brugada syndrome. In asymptomatic individuals, a prolonged H‐V interval during sinus rhythm is associated with a higher risk of developing arrhythmic events during follow‐up. Symptomatic patients require protective treatment even when they are not inducible. Asymptomatic patients can be reassured if they are noninducible.
Catheter Ablation: A Personal Perspective
Authors: Scheinman Melvin M.
Published: August 2003

Catheter Ablation. Catheter ablation for control of cardiac arrhythmias was introduced 20 years ago. Since then, this technique has been applied successfully to virtually all cardiac rhythm disturbances. In this essay, some of the newer applications of ablative techniques for patients with AV nodal reentrant tachycardia, atrial flutter, and atrial fibrillation are emphasized. “AV nodal reentrant tachycardia” may involve a nodofascicular tract. A new classification of atrial flutter is proposed and various causes of atrial fibrillation are discussed.