bluuebunny/crossref_metadata_2025 huggingface dataset:
Atrial Activation Sequence During Junctional Tachycardia Induced by Thermal Stimulation of Koch's Triangle in Canine Blood‐Perfused Atrioventricular Node Preparation
Authors: IWASA ATSUSHI , MOTOMURA SHIGERU , SASAKI SHINGO , DAITOKU KAZUYUKI , HIGUMA TAKUMI , OKUMURA KEN
Published: July 2003

IWASA, A., et al.: Atrial Activation Sequence During Junctional Tachycardia Induced by Thermal Stimulation of Koch's Triangle in Canine Blood‐Perfused Atrioventricular Node Preparation. Junctional tachycardia is observed during radiofrequency ablation of the slow pathway. The authors investigated the atrial activation sequence during junctional tachycardia induced with thermal stimulation in canine blood‐perfused atrioventricular node (AVN) preparation. The canine heart was isolated (n = 7) and cross‐circulated with heparinized arterial blood of the support dog. The activation sequence in the region of Koch's triangle (15 × 21 mm) was determined by recording 48 unipolar electrograms. Atrial sites anterior to the coronary sinus ostium (site AN), close to the His‐potential recording site (site N) and superior to site N (site F), were subjected to a continuous temperature rise from 38°C to 50°C with a heating probe. The temperature of the tissue adjacent to the heating site was monitored simultaneously. Junctional tachycardia at a rate of 92 ± 12 beats/min with the His potential preceding the atrial one in the His‐bundle electrogram was induced during thermal stimulation at site AN (temperature 42.1°C ± 0.9°C) in all seven preparations, whereas junctional tachycardia was induced during stimulation at site N in one and at site F in none. In each case, the temperature rose only at the site of stimulation. The earliest activation site during junctional tachycardia induced by site AN stimulation was at the His‐potential recording site in five preparations and the middle of Koch's triangle in the other two. After creating an obstacle between sites AN and N, atrial tachycardia at a rate of 85 ± 11 beats/min was induced during site AN stimulation. The earliest activation site during this tachycardia was site AN. Thus, junctional tachycardia induced by thermal stimulation was suggested to originate from the AN thermal stimulation site. The impulse from the stimulation site appeared to conduct via the posterior input to the compact AVN and junctional tachycardia was generated. When the posterior input was interrupted, atrial tachycardia was generated.
Left Atrial Tachyarrhythmia in Fetal Lambs
Authors: SHIRAISHI HIROHIKO , KIKUCHI YUTAKA , HOSHINA MASARU , MOMOI MARIKO Y.
Published: July 2003

SHIRAISHI, H., et al.: Left Atrial Tachyarrhythmia in Fetal Lambs. To evaluate the hemodynamic effect of rapid left atrial pacing on fetal circulation, a fetal supraventricular tachyarrhythmia model was made and the aortic pressure, central venous pressure, and left and right ventricular outputs were measured in ten fetal lambs. Under maternal anesthesia, the uterus was opened, and under local anesthesia, catheters were inserted into the fetal superior vena cava and ascending aorta through a neck incision. Pacing leads were then sutured onto the fetal left atrial appendage via left thoracotomy. Ventricular output was estimated using echocardiography by a transuterine approach. Fetal hemodynamics were observed without pacing (control), and at the pacing rates of 200, 300, 350, and 400/min. The aortic pressure decreased when the left atrium was paced at 300/min or more and the central venous pressure increased when the left atrium was paced at 350/min or more. The left and right ventricular outputs decreased when the left atrium was paced at 350/min or more. The left ventricular output was 215 ± 54 mL/kg per minute at control, 205 ± 60 mL/kg minute when paced at 200/min, 178 ± 58 mL/kg per minute when paced at 300/min, but decreased to 164 ± 44 mL/kg per minute when paced at 350/min and to 149 ± 57 mL/kg per minute when paced at 400/min. The right ventricular output was 338 ± 66 mL/kg per minute at control, 336 ± 95 mL/kg per minute when paced at 200/min, 273 ± 91 mL/kg per minute when paced at 300/min, but decreased to 256 ± 80 mL/kg per minute when paced at 350/min and to 202 ± 76 mL/kg per minute when paced at 400/min. Fetal circulatory failure was initially confirmed when the left atrium was paced at 300/min in this left atrial tachyarrhythmia model.
Atrial Pacing Lead Location Alters the Effects of Atrioventricular Delay on Atrial and Ventricular Hemodynamics
Authors: HETTRICK DOUGLAS A. , EULER DAVID E. , PAGEL PAUL S. , MUSLEY SHAILESH K. , WARMAN EDUARDO N. , ZIEGLER PAUL D. , MEHRA RAHUL
Published: July 2003

HETTRICK, D.A., et al.: Atrial Pacing Lead Location Alters the Effects of Atrioventricular Delay on Atrial and Ventricular Hemodynamics. The combined role of atrial pacing lead location and AV timing on cardiovascular performance has not been defined. This study tested the hypothesis that atrial pacing lead location can change the dependence of LA and LV hemodynamics on AV timing in vivo. Dogs anesthetized with isoflurane (n = 8) were instrumented for measurement of hemodynamics including LA pressure, LA volume, and pulmonary venous blood flow. Data were recorded during normal sinus rhythm, and atrial overdrive pacing from the right atrial appendage (RAA), proximal coronary sinus (CS), and LA lateral wall (LAW). The AV node was then ablated and measurements repeated during synchronous ventricular pacing and during dual chamber pacing from each atrial lead location at various AV delays (20, 60, 120, 180, 240, and 350 ms). Hemodynamics during intrinsic sinus rhythm and overdrive atrial pacing from different sites were similar. In contrast, ventricular or dual chamber pacing caused significant (P < 0.05) changes in cardiac output with different AV timing during RAA (3.5 ± 0.2 vs 2.9 ± 0.2 L/min at 120 and 350 ms, respectively) and LAW pacing but not CS pacing. A significant interaction between atrial lead location and AV delay was observed for changes in stroke volume, pulmonary venous blood transport, LA volume, and LV preload. The results indicate that the atrial contribution to cardiac output depends on AV timing and atrial lead location in isoflurane‐anesthetized dogs with AV nodal conduction block.
Long‐Term Follow‐Up of Pacing of the Conditioned Diaphragm in Quadriplegia
Authors: ELEFTERIADES JOHN A. , QUIN JACQUELYN A. , HOGAN JAMES F. , HOLCOMB WADE G. , LETSOU GEORGE V. , CHLOSTA WILLIAM F. , GLENN WILLIAM W.W.L.
Published: July 2003

ELEFTERIADES, J.A., et al.: Long‐Term Follow‐Up of Pacing of the Conditioned Diaphragm in Quadriplegia. The authors have previously shown that conditioning of the diaphragm for continuous bilateral pacing is a feasible and effective means of ventilation in patients with complete respiratory paralysis from high cervical (above C3) quadriplegia. The present study reports the long‐term results of continuous diaphragmatic pacing. Twelve quadriplegia patients underwent bilateral phrenic nerve pacemaker placement and diaphragm conditioning from 1981 to 1987. Pacing was initiated at 11 Hz and progressively decreased to 7.1 Hz. A pulse train duration of 1.3 seconds for adults and 0.9 seconds for children was used. Long‐term follow‐up information obtained included pacing status (full‐time, part‐time, or mechanical ventilation), ventilation parameters, and social circumstances. Of the 12 patients, 6 continued to pace full time (mean 14.8 years); all were living at home. Three patients paced for an average of 1.8 years before stopping; two were institutionalized. One patient who paced full time for 6.5 years before lapsing to part time, lived at home. Two patients were deceased; one paced continuously for 10 years before his demise, the other stopped pacing after 1 year. Patients who stopped full‐time pacing did so mainly for reasons of inadequate social or financial support or associated medical problems. All patients demonstrated normal tidal volumes and arterial blood gases while pacing full time. Despite theoretical concerns about long‐term nerve damage, no patient lost the ability to pace the phrenic nerve. Threshold currents did not increase over time (original/follow‐up: 0.46/0.47 for right, 0.45/0.46 for left), nor did maximal currents (original/follow‐up: 1.16/1.14 for right, 1.37/1.26 for left). This follow‐up confirms that quadriplegic patients are able to meet long‐term, full‐time ventilation requirements using phrenic nerve stimulation of the conditioned diaphragm. Careful review of diaphragmatic pacing candidates with respect to associated medical conditions, social support, and motivation is essential for appropriate patient selection and successful long‐term results.
Implantable Defibrillator Use for De Novo Ventricular Tachyarrhythmias Encountered After Cardiac Surgery
Authors: TELFER EDWARD A. , MECCA ANDREW , MARTINI MAUWIA , OLSHANSKY BRIAN
Published: July 2003

TELFER, E.A., et al.: Implantable Defibrillator Use for De Novo Ventricular Tachyarrhythmias Encountered After Cardiac Surgery. De novo postoperative life‐threatening ventricular arrhythmias are poorly understood. Long‐term benefits of, and need for, treatment is uncertain. To assess the therapeutic advantage of ICD to manage new‐onset, life‐threatening ventricular tachyarrhythmias after cardiac surgery. Patients included were those with an ICD implanted for de novo life‐threatening ventricular tachyarrhythmias encountered 48 hours or more after cardiac surgery. Primary endpoints were total survival, time to first ICD therapy, and appropriateness of ICD therapy. Mean projected survival and projected time to first ICD therapy were calculated by the Kaplan‐Meier method. Twenty‐seven postoperative patients (left ventricular ejection fraction 0.22 ± 0.07) were followed for 26 ± 17.6 months. The index arrhythmia was sustained monomorphic ventricular tachycardia in 17 (63%) and ventricular fibrillation in 10 (37%). Electrophysiological study was positive in 22 (81%) of 27. Total survival and mean projected survival after ICD implant were 22 (81%) of 27 and 25.6 months, respectively, to end of follow‐up. The majority received ICD therapy (21/27 [78%]), 20 (74%) of 27 receiving appropriate therapy. The mean time to first ICD therapy and mean projected time to first ICD therapy was 5.6 ± 7.8 months and 10.5 months, respectively. De novo postoperative ventricular arrhythmias are associated with a high probability of late recurrence. The ICD is useful for these patients.
Permanent Left Atrial and Left Ventricular Single‐Lead DDD Pacing with a Coronary Sinus Electrode
Authors: MERKELY BÉLA , VÁGÓ HAJNALKA , BARTHA ELEKTRA
Published: July 2003

MERKELY, B., et al.: Permanent Left Atrial and Left Ventricular Single‐Lead DDD Pacing with a Coronary Sinus Electrode. This report describes a patient with drug refractory severe chronic congestive heart failure, first‐degree AV block, and wide QRS complexes of 175‐ms duration with left bundle branch block who was successfully treated by a left‐sided dual chamber pacemaker system using a single‐lead coronary sinus electrode. Left atrial and ventricular signal amplitudes, left atrial and ventricular pacing thresholds were 2.5 mV, 13 mV, 1.8 V and 0.7 V (0.5ms), respectively. Using DDD pacing with an optimal 120‐ms AV delay the QRS duration decreased to 150 ms and the mitral filling pattern improved. Three months after implantation the patient's functional status improved from NYHA Class III‐IV to Class II.
Optimal Location for Temporary Epicardial Pacing Leads Following Open Heart Surgery
Authors: HURLÉ AQUILINO , GÓMEZ‐PLANA JESÚS , SÁNCHEZ JOSÉ , MARTÍNEZ JUAN G. , MESEGUER JUAN , LLAMAS PATRICIO
Published: July 2003

HURLÉ, A., et al.: Optimal Location for Temporary Epicardial Pacing Leads Following Open Heart Surgery. Temporary epicardial pacing wires are routinely placed in patients undergoing cardiac surgery. Eighteen suitable patients undergoing elective surgery were prospectively studied. Their sensing and stimulating characteristics were studied at various locations. Subepicardial pacing leads were applied to the lateral wall of the LV, apex of the LV, anterior wall of the RV, diaphragmatic wall of the RV, and diaphragmatic wall of the LV. Impedance, R wave amplitude, slew rate, and stimulation thresholds were measured on postoperative days 1 and 5. Impedance remained unchanged in time with no significant differences between locations. R waves and slew rates were significantly lower in the anterior RV wall. Stimulation thresholds displayed no differences on day 1, but they increased significantly in all locations on day 5. These thresholds were significantly lower in the lateral and diaphragmatic LV walls on day 5, and the rate of voltage increase was also lower in these two locations. Five patients presented phrenic nerve stimulation when stimulating the lateral LV wall. The authors advocate the diaphragmatic wall of the LV as the best location for placing temporary leads. The anterior wall of the RV is not recommended for pacing purposes.
Matching Approved “Nondedicated” Hardware to Obtain Biventricular Pacing and Defibrillation: Feasibility and Troubleshooting
Authors: KANAGARATNAM LOGAN , PAVIA STEPHEN , SCHWEIKERT ROBERT , MARROUCHE NASSIR , LAM CATHY , ABREU MIGUEL , CHING ELIZABETH , CHUNG MINA , SALIBA WALID , NIEBAUER MARK , WILKOFF BRUCE , TCHOU PATRICK , NATALE ANDREA
Published: July 2003

KANAGARATNAM, L., et al.: Matching Approved “Nondedicated” Hardware to Obtain Biventricular Pacing and Defibrillation: Feasibility and Troubleshooting. Biventricular ICDs may offer increased benefit for patients with severe congestive heart failure and ventricular arrhythmia. Currently there are no approved dedicated biventricular ICDs available. Twenty‐one consecutive patients who had approved nondedicated hardware implanted for biventricular pacing and defibrillation were included in this study. All device therapies were evaluated using stored electrograms. During mean follow‐up at 13 ± 7 months, 8 (36%) patients had inappropriate shocks. Ventricular fibrillation therapy was delivered for slow ventricular tachycardia because of double counting in two patients. In one patient, AV nodal reentrant tachycardia below detection rate cut off triggered device therapy because of ventricular double counting. Sinus tachycardia or premature atrial contraction initiating AV conduction and ventricular double counting resulted in shocks in five patients. The number of shocks per patient ranged from 1 to 64. Two patients required transient disconnection of the LV lead and subsequent ICD generator replacement for premature battery depletion. Two patients required AV junction ablation and three needed slow pathway ablation. Two patients were treated by upgrading to a device that was capable of a higher atrial tracking rate. The patients with impaired AV conduction or constant ventricular pacing did not have inappropriate therapy for sinus tachycardia or supraventricular arrhythmia. Use of conventional nondedicated hardware for biventricular pacer/defibrillator is feasible but should be considered only in patients with poor AV node function or less likely to require antitachycardic therapy, to avoid ICD double counting of ventricular sensed events and consequent high incidence of inappropriate therapies.
Pacing of Bachmann's Bundle After Coronary Artery Bypass Grafting
Authors: GOETTE ANDREAS , MITTAG JOERG , FRIEDL ANDREA , BUSK HENNING , JEPSEN MARILENE S. , HARTUNG WOLFGANG M. , HUTH CHRISTOF , KLEIN HELMUT U.
Published: July 2003

GOETTE, A., et al.: Pacing of Bachmann's Bundle After Coronary Artery Bypass Grafting. The purpose of this randomized, prospective trial was to determine if Bachmann's bundle pacing reduces the incidence of AF after CABG. The study included 161 patients with no history of AF who were randomized to three groups. Group 1 included 50 patients as controls. Group 2 included 60 patients who had an epicardial wire placed at the lateral wall of the right atrium. In the 51 patients of group 3, the wire was placed at the Bachmann's bundle. In groups 2 and 3, atrial pacing (AAI 96 beats/min) was initiated immediately after CABG and continued for 5 days. The study endpoint was AF lasting ≥ 1 minute. Baseline clinical parameters were similar in all three groups. The incidence of AF was not reduced by pacing (group 1: 42%; group 2: 48%; group 3: 37%; P = NS). The paced P wave duration was increased in group 2 (129 ± 14 ms vs group 3: 96 ± 21 ms; P < 0.05). Paced P wave duration was a risk factor for postoperative AF (odds ratio 1.015; 95% CI 1.0021–1.028; P < 0.05). Analysis comparing the pacing groups revealed a reduction in AF during Bachmann's bundle pacing (50 vs 29%; P < 0.01). Pacing thresholds were significantly better at Bachmann's bundle compared to group 2. In conclusion, an anatomically guided pacing at the Bachmann's bundle does not reduce the overall incidence of postoperative AF compared to controls. However, the Bachmann's bundle offers favorable capabilities for postoperative atrial pacing, and thus it is a preferable site for electrode placement if postoperative atrial pacing is required.
Characterization of the Electroanatomic Substrate for Monomorphic Ventricular Tachycardia in Patients with Nonischemic Cardiomyopathy
Authors: HSIA HENRY H. , MARCHLINSKI FRANCIS E.
Published: July 2003

HSIA, H.H., et al.: Characterization of the Electroanatomic Substrate for Monomorphic Ventricular Tachycardia in Patients with Nonischemic Cardiomyopathy. Ventricular arrhythmias are common in the setting of nonischemic cardiomyopathy. The etiology for the cardiomyopathy is frequently not identified and the label of “idiopathic” is applied. Interstitial fibrosis with conduction system involvement and associated left bundle branch block characterizes the disease process in some patients and the mechanism for monomorphic ventricular tachycardia is commonly bundle branch reentry. However, most patients with nonischemic cardiomyopathy have VT due to myocardial reentry and demonstrate marked myocardial fibrosis and electrogram abnormalities. Although patient specific, the overall distribution of electroanatomic abnormalities appears to be equal on the endocardium and epicardium. The extent of electrogram abnormalities appears to parallel arrhythmia presentation and/or inducibility. Patients with sustained uniform morphology VT have the most extensive endocardial and epicardial electrogram abnormalities. Magnetic electroanatomic voltage mapping provides a powerful tool to characterize the location and extent of the arrhythmia substrate. Basal left ventricular myocardial involvement, as indexed by the location of contiguous electrogram abnormalities, is common in patients with sustained VT and left ventricular cardiomyopathy. The relatively equal distribution of electrogram abnormalities on the endocardium and epicardium, and the results of mapping and ablation attempts, suggest that critical parts of the reentrant circuit may be epicardial. Unique features of the electroanatomic substrate associated with cardiomyopathy due to Chagas' disease, sarcoidosis, and arrhythmogenic right ventricular dysplasia are also discussed.
Radiofrequency Catheter Ablation of “Typical” Atrial Flutter in a Patient with Kartagener's Syndrome
Authors: HUANG FAITH R. , HAU DUNCAN K. , LEE MICHAEL A.
Published: July 2003

HUANG, F.R., et al.: Radiofrequency Catheter Ablation of “Typical” Atrial Flutter in a Patient with Kartagener's Syndrome. Kartagener's syndrome and radiofrequency catheter ablation for the treatment of atrial flutter have been well described in separate reports. This case report includes both in describing a patient with Kartagener's syndrome who had medically refractory atrial flutter that was successfully treated with radiofrequency catheter ablation.
Ineffective ICD Therapy Due to Excessive Alcohol and Exercise
Authors: PAPAIOANNOU GEORGIOS I. , KLUGER JEFFREY
Published: July 2003

PAPAIOANNOU, G.I., et al.: Ineffective ICD Therapy Due to Excessive Alcohol and Exercise. A 49‐yearold man with dilated cardiomyopathy and an ICD received eight unsuccessful shocks for a single episode of ventricular tachycardia after excessive alcohol intake and exercise. The patient had low defibrillation thresholds just 8 days prior to his event during a routine 6‐week postimplant electrophysiological study. Defibrillation threshold testing after his incident confirmed the low energy requirement for ventricular tachycardia termination. A previous animal study reported that intravenous ethanol elevates the defibrillation energy in a dose dependent manner. However, a recent study in humans showed that modest alcohol intake had no effect on defibrillator thresholds. This case report supports the animal data and suggests that excessive alcohol consumption can cause a life‐threatening situation in ICD patients.
Delayed Complications Following Pacemaker Implantation
Authors: ELLENBOGEN KENNETH A. , WOOD MARK A. , SHEPARD RICHARD K.
Published: July 2003

ELLENBOGEN, K.A., et al.: Delayed Complications Following Pacemaker Implantation. Acute complications resulting from permanent pacemaker implantation are well known and include perforation of the right atrium or right ventricle. Recently, several reports have described the occurrence of perforation and pericarditis as late complications following pacemaker implantation. These complications may occur days to weeks following uncomplicated pacemaker implantation and may lead to death if they are not recognized early. Five patients with late complications caused by active‐fixation leads are reported and the clinical features of their presentation and management are reviewed. Late perforation of the right atrium or right ventricle is an uncommon complication after pacemaker implantation but should be suspected by the general cardiologist in a patient who has a device implanted within a week to several months prior to the development of chest pain.
Capture of Atrial Fibrillation Reduces the Atrial Defibrillation Threshold
Authors: VILLANI GIOVANNI Q. , NOLLO GIANDOMENICO , RAVELLI FLAVIA , PIEPOLI MASSIMO , CAPUCCI ALESSANDRO
Published: July 2003

VILLANI, G.Q., et al.: Capture of Atrial Fibrillation Reduces the Atrial Defibrillation Threshold. The effect of the atrial activity synchronization by single site right atrial pacing on atrial defibrillation threshold (ADFT) was investigated in patients with AF. Two series of randomized incremental cardioversion tests, with increasing energy levels from 0.5 to 10 J, were performed in 15 patients with recurrent episodes of idiopathic paroxysmal AF using two 7 Fr “single coil” catheters for internal cardioversion. After induction of sustained AF (> 10 minutes), shocks were delivered, preceded or not by 10 seconds of overdrive local atrial pacing, according to the randomization, using an external cardioverter defibrillator. A total of 187 shocks was delivered to the study population. ADFT was reduced when overdrive atrial stimulation preceded the cardioversion (3.6 ± 1.6 vs 2.9 ± 1.7 J, P = 0.02). Local atrial capture was considered on the basis of 1:1 phase locking between stimulus and atrial activation wave, and constant morphology of atrial wave criteria. Effective atrial capture was obtained in 8 of 15 patients. There was not significant difference in the mean of FF intervals of patients in which atrial capture was or was not stable (209 ± 22 vs 208 ± 28 ms). Patients were then considered according to the outcome of atrial pacing before direct current shock. A marked ADFT reduction was observed in patients with stable capture (3.8 ± 1.7 vs 2.5 ± 1.7 J, P = 0.0003), while no significant difference in ADFT was found when capture was not achieved (3.4 ± 1.6 vs 3.6 ± 1.5 J, P = NS). In conclusion, regularization of atrial electrical activity by atrial capture reduces the ADFT. A constant pacing entrainment seems to lower the energy required for electrical cardioversion by reducing the amount of fibrillating tissue.
Prospective Randomized Comparison of Cooled Radiofrequency Versus Standard Radiofrequency Energy for Ablation of Typical Atrial Flutter
Authors: ATIGA WALTER L. , WORLEY SETH J. , HUMMEL JOHN , BERGER RONALD D. , GOHN DOUGLAS C. , MANDALAKAS NICHOLAS J. , KALBFLEISCH STEVEN , HALPERIN HENRY , DONAHUE KEVIN , TOMASELLI GORDON , CALKINS HUGH , DAOUD EMILE
Published: July 2003

ATIGA, W.L., et al.: Prospective Randomized Comparison of Cooled Radiofrequency Versus Standard Radiofrequency Energy for Ablation of Typical Atrial Flutter. In patients with atrial flutter, conventional RF ablation may not result in complete isthmus block. This prospective, randomized study tested the hypothesis that the cooled RF ablation is safe and facilitates the achievement of isthmus block with fewer RF applications than with standard ablation for typical atrial flutter. Isthmus ablation was performed in 59 patients (40 men, 64 ± 14 years) with type I atrial flutter using standard RF (n = 31) or cooled RF (n = 28) catheters with crossover after 12 unsuccessful RF applications. The endpoint was bidirectional isthmus block or a total of 24 unsuccessful RF applications. After the first 12 RF applications, 17 (55%) of 31 standard RF and 22 (79%) of 28 cooled RF patients had bidirectional isthmus block (P < 0.05). After the remaining patients crossed over to the alternate RF ablation system and underwent up to 12 more RF applications, bidirectional isthmus block had been demonstrated in 27 (87%) of 31 standard RF and 25 (89%) of 28 cooled RF patients (P = NS). Isthmus block was not achieved within 24 RF applications in four standard and three cooled RF patients. Mean measured tip temperatures for cooled RF were lower than for standard RF (38.5°C ± 6.98°C vs 57.2°C ± 7.42°C, P < 0.0001). Peak temperatures were also lower for cooled RF compared to standard RF (45.7°C ± 22.7°C vs 63.4°C ± 9.87°C, P < 0.0001). Importantly, mean power delivered was significantly higher for cooled than for standard RF (42.3 ± 9.48 vs 34.0 ± 14.0 W, P < 0.0001). There were no serious complications for either ablation system. During a 12.8 ± 3.76‐month follow‐up, there were two atrial flutter recurrences in the cooled RF group and four in the standard RF group (P = NS). In patients with type I atrial flutter, ablation with the cooled RF catheter is as safe as, and facilitates creation of bidirectional isthmus block more rapidly than, standard RF ablation.
Atrial Fibrillatory Frequency Predicts Atrial Defibrillation Threshold and Early Arrhythmia Recurrence in Patients Undergoing Internal Cardioversion of Persistent Atrial Fibrillation
Authors: BOLLMANN ANDREAS , MENDE MAIKA , NEUGEBAUER ANNEROSE , PFEIFFER DIETRICH
Published: July 2003

BOLLMANN, A., et al.: Atrial Fibrillatory Frequency Predicts Atrial Defibrillation Threshold and Early Arrhythmia Recurrence in Patients Undergoing Internal Cardioversion of Persistent Atrial Fibrillation. This study was conducted to analyze the meaning of AF frequency obtained from the surface ECG for prediction of energy requirements and early arrhythmia relapse in patients undergoing internal cardioversion of persistent AF. Nineteen consecutive patients (mean age 58 ± 11 years; 11 men, 8 women) with persistent AF (> 7 days) underwent internal cardioversion. A biphasic shock synchronized to the R wave was delivered between two catheters positioned in the high right atrium (HRA) and the coronary sinus (CS). AF frequency was estimated prior to cardioversion from surface ECG lead V1. After filtering, QRST complexes were subtracted using a template matching and averaging algorithm. The resulting fibrillatory baseline signal was subjected to Fourier transformation, displayed as a frequency power spectrum and the peak frequency was determined in the 3–12 Hz frequency band. Atrial defibrillation threshold (ADFT) was determined using a step‐up protocol. All patients were cardioverted successfully with a mean ADFT of 7.6 ± 6.5 J (range 0.5–25). There was a strong positive correlation between fibrillatory frequency and ADFT (R = 0.71, P = 0.001). AF recurrence within 30 days after successful cardioversion occurred in 11 (58%) patients. Receiver operating characteristic (ROC) analysis revealed a fibrillatory frequency ≥ 7 Hz to be 64% sensitive and 88% specific to predict AF recurrence. It was observed in 4 (36%) of 11 cases with a fibrillatory frequency < 7 Hz, as opposed to 7 (88%) of 8 cases with a fibrillatory frequency ≥ 7 Hz (P = 0.02). Fibrillatory frequency obtained from the surface ECG predicts ADFT and early AF recurrence in patients with persistent AF undergoing internal cardioversion.
The Immediate Reproducibility of T Wave Alternans During Bicycle Exercise
Authors: BLOOMFIELD DANIEL M. , RITVO BROOKE S. , PARIDES MICHAEL K. , KIM MICHAEL H.
Published: July 2003

BLOOMFIELD, D.M., et al.: The Immediate Reproducibility of T Wave Alternans During Bicycle Exercise. A number of recent studies have demonstrated that the microvolt level T wave alternans measured during bicycle exercise can identify patients at high risk for developing malignant ventricular arrhythmias. However, little is known about the reproducibility of T wave alternans measured during bicycle exercise. The purpose of this study was to prospectively evaluate the immediate reproducibility of T wave alternans measured during bicycle exercise testing. Thirty‐five patients with congestive heart failure underwent two sequential bicycle exercise tests with the measurement of T wave alternans. The T wave alternans tests were randomly sorted and then classified by two readers who were blinded to the patient and the sequence of the two tests. Tests were classified as determinate (positive or negative) or indeterminate according to previously published criteria. Of the 22 patients that had two determinate T wave alternans tests, 18 (82%) of 22 patients had concordant test results (kappa 0.58). Of the four patients who had discordant test results on the two tests, three patients had one test that was borderline and difficult to interpret. One patient had two sequential tests that were clearly different. Of the ten patients whose initial test was indeterminate, five became determinate on the second test. T wave alternans measured during bicycle exercise has an acceptable reproducibility when measurements are made from two sequential exercise tests performed within a short period. This data suggests that the measurement of T wave alternans during exercise is reliable. Repeating the exercise test with a second measure of T wave alternans during the same session can significantly reduce the proportion of patients with indeterminate test results.
Cardiac Interbeat Interval Increment for the Identification of Obstructive Sleep Apnea
Authors: ROCHE FRÉDÉRIC , DUVERNEY DAVID , COURT‐FORTUNE ISABELLE , PICHOT VINCENT , COSTES FRÉDÉRIC , LACOUR JEAN‐RENÉ , ANTONIADIS ANESTIS , GASPOZ JEAN‐MICHEL , BARTHELEMY JEAN‐CLAUDE
Published: July 2003

ROCHE, F., et al.: Cardiac Interbeat Interval Increment for the Identification of Obstructive Sleep Apnea. The prevalence of obstructive sleep apnea syndrome (OSAS) is high in developed countries but its diagnosis is costly. Based on physiological evidence, the frequency component of heart rate variability (HRV) was evaluated as a simple and inexpensive diagnostic tool in OSAS. The predictive accuracy of frequency‐domain HRV variables obtained from 24‐hour ECG Holter monitoring (the power spectral density of the interbeat interval increment of very low frequencies, “VLFIpsd,” and its percentage over the total power spectral density, “%VLFI”), and of established time‐domain HRV variables were analyzed by comparison with respiratory disturbances indexes assessed by complete polysomnography in 124 consecutive patients (98 men aged 53.8 ± 11.2 years) with clinically suspected OSAS. OSAS was present in 54 (43.5%) patients according to standard criteria. Using receiver operating characteristic curve analysis, two of the three most powerful predictors were frequency‐domain variables: %VLFI (W = 0.80, P < 0.0001), and VLFIpsd (W = 0.79, P < 0.0001). Using a multiple logistic regression analysis, %VLFI was the most strongly associated with diseased status (adjusted OR: 8.4; 95% CI: 3.4–19.5). Using an appropriate threshold, %VLFI demonstrated a diagnostic sensitivity of 87%. A 3‐month continuous positive airway pressure treatment significantly improved the same parameter. Frequency‐domain analysis of the interbeat interval increment appears as a powerful tool for OSAS diagnosis and follow‐up. The simplicity of its analysis and of its use makes of it a well‐suited variable for mass screening of OSAS patients.
The Effect of Sex on Ventricular Arrhythmic Events in Patients with Congestive Heart Failure
Authors: ARONSON DORON , BURGER ANDREW J.
Published: July 2003

ARONSON, D., et al.: The Effect of Sex on Ventricular Arrhythmic Events in Patients with Congestive Heart Failure. The propensity to develop specific arrhythmias varies between the sexes. Patients with congestive heart failure (CHF) have a high prevalence of ventricular ectopy. However, it is not known if sex related differences exist in the susceptibility to arrhythmias in the setting of CHF. The study population included 159 men and 77 women (mean age 61 ± 14 years) admitted for decompensated CHF. The severity of atrial and ventricular arrhythmias was assessed by 24‐hour Holter monitoring. None of the patients were on parenteral vasoactive therapy during Holter recording. All measures of ventricular ectopy were markedly lower in women compared to men. The mean hourly ventricular pairs (283 ± 67 vs 106 ± 30, P = 0.04), mean hourly repetitive ventricular beats (28 ± 7 vs 10 ± 3, P = 0.04), and the frequency of ventricular tachycardia episodes per 24 hours (31 ± 9 vs 7 ± 3, P = 0.01) were significantly lower in women. After inclusion of clinical variables and drug therapies in a multivariate analysis, the negative relationship between female sex and the frequency of ventricular pairs (P = 0.04), repetitive ventricular beats (P = 0.04), and ventricular tachycardia episodes (P = 0.0005) remained independent. No differences in atrial ectopy between men and woman were found. Complex ventricular ectopy and episodes of ventricular tachycardia are significantly lower in women with CHF. Whether these finding are relevant to female survival advantage in the setting of heart failure can only be determined by a prospective study. Further understanding of the mechanisms involved in the protection conferred by the patient's sex would advance our understanding about arrhythmias in heart failure.
Measurement of Body Surface Energy Leakage of Defibrillation Shock by an Implantable Cardioverter Defibrillator
Authors: NIWANO SHINICHI , KOJIMA JISHO , INUO KIMIATSU , SAITO JUNKO , KASHIWA TETSUO , SUYAMA MAKOTO , TOYOSHIMA TAKESHI , AIZAWA YOSHIFUSA , IZUMI TOHRU
Published: July 2003

NIWANO, S., et al.: Measurement of Body Surface Energy Leakage of Defibrillation Shock by an Implantable Cardioverter Defibrillator. Leakage of electrical current from the body surface during a defibrillation shock delivery by an ICD device was evaluated in 27 patients with life‐threatening ventricular tachyarrhythmias. All patients underwent the implantation of the Medtronic Jewel Plus ICD system, and the defibrillation shocks were delivered between the active can implanted in the left subclavicular region and the endocardial lead placed in the right ventricle. At the time of measurement of the effect of electrical energy delivery for defibrillation, the shocks were delivered in a biphasic form at the energy level of 20 or 30 J. During each delivery of the defibrillation shock, the electrical current to the body surface was measured through large skin electrodes (6.2 cm2) that were pasted at the following positions: (1) parallel position: the electrodes were placed at the left shoulder and the right low‐chest, and the direction of the electrode vector was parallel to the direction of the defibrillation energy flow, and (2) cross position: the electrodes were placed at the right shoulder and the left low‐chest, and the vector of the electrodes was roughly perpendicular to the direction of the energy flow. The energy leakages were measured in 80 defibrillation shocks. The peak leakage current during the shock delivery at energy of 30 J was 48 ± 26 mA at the parallel position and 19 ± 15 mA at the cross position (P = 0.0002). The energy leakage at a 30‐J shock was 7.4 ± 7.2 mJ at the parallel position and 1.4 ± 2.3 mJ at the cross position (P = 0.0002). The actual maximum energy leakage was 105 mA, 29 mJ, and 106 V that appeared at the parallel position. The body surface leakage of the defibrillation energy of the ICD device was evaluated. The power of the energy leakage strongly depended on the angle between the alignment of the recording electrodes and the direction of the energy flow. The highest current leakage to the body surface reached a considerable level, but the energy leakage was small because of the short duration of the defibrillation shock.
Quantification of T Wave Shape Changes Following Exercise
Authors: LANGLEY PHILIP , BERNARDO DIEGO DI , MURRAY ALAN
Published: July 2003

LANGLEY, P., et al.: Quantification of T Wave Shape Changes Following Exercise. T wave shape is increasingly used to provide insights into cardiac repolarization and, although shape is known to change as heart rate changes, there are no published quantitative clinical data. The aim of this study was to quantify these changes. Heart rate (HR), T wave amplitude, and two measures of T wave symmetry (SRarea—ratio of areas about the peak, SRtime—ratio of centrality of peak), were quantified over a period of 360 seconds following exercise in 20 healthy human subjects. As HR decreased, in all subjects the T wave became more asymmetrical (SRarea 20/20, SRtime 20/20, P < 0.0001). Resting reference HR and symmetry ratios were (mean ± SD), HR 63 ± 10 beat/min, SRarea 1.68 ± 0.25, and SRtime 2.13 ± 0.39. Fifty seconds postexercise, HR was significantly higher than reference at 92 ± 11 beat/min (P < 0.0001), and symmetry ratios were significantly less at SRarea 1.04 ± 0.15, SRtime 1.24 ± 0.36 (P < 0.0001). Significant differences in HR and both symmetry ratios remained at 300 seconds postexercise. Amplitude increases had returned to their reference values at 300 seconds. T wave shape was significantly more symmetrical at higher HRs. These findings confirm qualitative reports of shape changes.
Catheter Ablation of Atrial Flutter in a Heart Transplant Recipient
Authors: KRISHNAN SUBRAMANIAM C. , FALSONE JOSEPH M. , SANDERS WILLIAM E. , CHEN HONG , MILL MICHAEL R. , KUSHWAHA SUDHIR S.
Published: July 2003

KRISHNAN, S.C., et al.: Catheter Ablation of Atrial Flutter in a Heart Transplant Recipient. In the transplanted heart with biatrial anastomosis, atrial flutter is common and is amenable to catheter ablation. Although this arrhythmia is isthmus dependent, the unique atrial architecture with a suture line through the inferior vena cava‐tricuspid annulus isthmus makes the substrate atypical. A cardiac transplant recipient with atrial flutter underwent successful catheter ablation. Five weeks after the procedure, the patient died of a myocardial infarction. The autopsy and histological findings are described and correlated with the electroanatomic map obtained during the ablation. Due to the atrial suture lines, atrial flutter following cardiac transplantation is an isthmus dependent arrhythmia with a different arrhythmogenic substrate. The electrical isthmus (atrial tissue from the tricuspid annulus to the suture line) in these hearts is smaller than the anatomic isthmus.
Arrhythmogenic Right Ventricular Dysplasia in the Elderly
Authors: MORE DANIEL , O'BRIEN KEVIN , SHAW JANET
Published: July 2003

MORE, D., et al.: Arrhythmogenic Right Ventricular Dysplasia in the Elderly. Arrhythmogenic right ventricular dysplasia (ARVD) is a syndrome characterized by recurrent ventricular tachycardia. However, cases of ARVD have also presented as dilated cardiomyopathy later associated with ventricular arrhythmias. Histologically, this syndrome manifests as a fibrofatty replacement of the RV myocardium, predisposing the heart to ventricular arrhythmias. ARVD was once considered a disease of the young, but may be underrecognized in the older population. This report presents two cases of elderly men with newly symptomatic ARVD, believed to represent the oldest patients with ARVD described in the literature to date. The diagnosis of ARVD should be considered in individuals of all ages who present with a clinical syndrome consistent with ARVD and supportive evidence on ECG.
Syncope with ST‐Segment Abnormalities Resembling Brugada Syndrome Due to Reversible Myocardial Ischemia
Authors: INDIK JULIA H. , OTT PETER , BUTMAN SAMUEL M.
Published: July 2003

INDIK, J. H., et al.: Syncope with ST‐Segment Abnormalities Resembling Brugada Syndrome Due to Reversible Myocardial Ischemia. This report describes a case of syncope with an initial ECG that showed ST‐segment elevation in the right precordial leads suggestive of Brugada syndrome. Procainamide infusion induced a significant increase in the ST‐segment abnormalities, further increasing the suspicion for this syndrome. Cardiac catheterization showed lesions in the proximal left anterior descending artery and distal right coronary artery. Following percutaneous coronary intervention at these sites, the ST‐segment abnormalities resolved and a repeat procainamide challenge was negative. Electrophysiological study did not provoke any ventricular arrhythmias. Silent myocardial ischemia may result in ECG changes that resemble those seen in patients with Brugada syndrome.
Alternans of Blood Pressure and Heart Rate in Dilated Cardiomyopathy
Authors: LEDER UWE , POHL HANS‐PETER , BAIER VICO , BAUMERT MATTHIAS , LIEHR MARIO , HAUEISEN JENS , VOSS ANDREAS , FIGULLA HANS R.
Published: July 2003

LEDER, U., et al.: Alternans of Blood Pressure and Heart Rate in Dilated Cardiomyopathy. Impaired myocardial performance is known to be associated with electrical and mechanical beat‐to‐beat alternans phenomena. The alternans in blood pressure and heart rate and their interdependency in idiopathic dilated cardiomyopathy (IDC) were studied. The arterial blood pressure and the electrocardiograph (ECG) were continuously recorded in 22 patients suffering from IDC (age 49 ± 13 years, ejection fraction 0.33 ± 0.13, left ventricular diameter of 67 ± 8 mm) and in 21 healthy controls (age 52 ± 15 years). The beat‐to‐beat variations of the interbeat intervals (IBI) and of the blood pressure amplitudes (AMP) were measured. An alternans beat was defined as a beat preceded and followed by beats that had higher or lower values in the respective modality. The percentages of singular and repetitive alternans patterns, and the interdependency of the alternans patterns in AMP and IBI were assessed. The study found significantly more singular and repetitive alternans patterns in the IDC group compared to the control group both in the analysis of AMP and IBI (singular alternans in IBI: 55 ± 11 vs 47 ± 7%, P < 0.01; singular alternans in AMP: 61 ± 15 vs 45 ± 6%, P < 0.01; triple alternans in IBI: 29 ± 18 vs 16 ± 9%, P < 0.01; triple alternans in AMP: 34 ± 24 vs 12 ± 7%, P < 0.01). The amplitudes of the AMP alternans patterns were higher in IDC compared to controls (9 ± 7 vs 4 ± 2% of AMP, P = 0.01) whereas they did not differ in IBI. The correlation analysis revealed a significant interdependency of the alternans pattern in IBI and AMP in 18 of 22 IDC patients and in 12 of 21 controls (r = 0.50 ± 0.21 [IDC]; r = 0.26 ± 0.05 [controls]). The slope of the linear regression (ΔAMP vs ΔIBI) was steeper in the IDC group compared to the control group (62 ± 50 vs 20 ± 22 mmHg/s, P < 0.01). The percentages of alternans patterns appearing in IBI and AMP were positively correlated to the left ventricular diameter (r = 0.70 in the IBI, and r = 0.30 in the AMP). The blood pressure amplitude and the heart rate did not differ between the two groups. Patients suffering from IDC have a higher prevalence, stability, amplitude, and interdependency of alternans patterns in IBI and AMP compared to the control group. The amount of alternans patterns indicates the stage of disease. The alternans analysis may have impact on the functional assessment of patients suffering from heart failure.
Baroreflexes in Vasovagal Syncope: Two Types of Abnormal Response
Authors: FLEVARI PANAGIOTA P. , LIVANIS EFTHIMIOS G. , THEODORAKIS GEORGE N. , MESISKLI THEONI , ZARVALIS ELIAS , KREMASTINOS DIMITRIOS TH.
Published: July 2003

FLEVARI, P.P., et al.: Baroreflexes in Vasovagal Syncope: Two Types of Abnormal Response. Heart rate changes to hypotensive stimuli (baroreceptor sensitivity [BRS]) and forearm blood flow (FBF) reduction during head‐up tilt are mediated by arterial and cardiopulmonary baroreceptors. Regarding baroreflexes in neurocardiogenic syncope (NCS), an apparent variation exists in findings reported in the literature. This may be due to the existence of different types of response. This study included 39 patients with NCS and positive tilt test and 26 normal subjects with negative test. Patients were grouped according to the type of tilt test response (mixed, cardioinhibitory, vasodepressor). BRS was noninvasively assessed in the supine position as an estimate of arterial baroreceptor sensitivity. As an estimate of cardiopulmonary baroreceptor reactivity, FBF was measured by venous occlusion plethysmography in the supine position and every 2.5 minutes during the first 15 minutes of tilt. BRS was related to percent of FBF changes. BRS was impaired in syncopal patients relative to controls (7.2 ± 0.9 vs 10.4 ± 0.3 ms/mmHg, P = 0.01), especially in vasodepressive type (4.9 ± 1.0 ms/mmHg, P = 0.0001). FBF changes during tilt were subnormal in NCS, ascribed to two different patterns: one, characterized by impaired vasoconstriction (FBF during tilt showing < 10% mean reduction relative to baseline, especially in vasodepressive type) and another, characterized by a great variability across time (unstable response, especially in cardioinhibitory type). In controls, BRS was related to the percent of FBF changes after 2.5, 5, and 10 minutes of tilt (P values 0.0001, 0.004, and 0.008). In patients, BRS was uncoupled from FBF changes. In conclusion, baroreflexes in NCS are impaired, unstable, and disorganized. Impairment predominates in the vasodepressive type and instability in the cardioinhibitory. The results of this study are indicative of more than one baroreflex‐mediated response types.
Cumulative Effect of Preceding Pacing Cycle Length on Ventricular Repolarization After a Pause
Authors: KIRA TETSUYA , TAKAHASHI NAOHIKO , SATO YASUKAZU , TAKAKURA TAKESHI , HARA MASAHIDE , SAIKAWA TETSUNORI , SAKATA TOSHIIE
Published: July 2003

KIRA, T., et al.: Cumulative Effect of Preceding Pacing Cycle Length on Ventricular Repolarization After a Pause. This study was designed to investigate if the components of the QT interval after a pause are influenced by the preceding pacing cycle length. Ten patients (seven women and three men; age 79 ± 9 years, means ± SD) with complete atrioventricular block or sick sinus syndrome whose own heart rate was < 40 beats/min were examined. All patients had already undergone implantation of a permanent pacemaker. Ventricular pacing protocol was performed with simultaneous recording of a 12‐lead electrocardiogram. One set of regular stimuli for 30 seconds (S1) with a variable cycle length (1,000, 700, and 400 ms) was followed by a single stimulus (S2) with a fixed coupling interval of 1,500 ms. QT intervals in response to the last S1 (S1‐QT) and S2 (S2‐QT) were measured. The QT interval was divided into two components, the interval from start of Q wave to the peak of T wave (QaT) and that from the peak to end of T wave (Tae). The S2‐QT and S1‐QT interval shortened in association with a decrease in the S1S1 interval. The abbreviation of S2‐QT interval was not associated with a significant change in the Tae interval. The results demonstrated that the QT interval after a pause shortened by reducing the preceding pacing cycle length. This shortening is probably due to a homogenous abbreviation of action potential duration across the ventricular wall.