bluuebunny/crossref_metadata_2025 huggingface dataset:
The Use of Beep‐O‐Grams in the Assessment of Automatic Implantahle Cardioverter Defibrillator Sensing Function
Authors: BALLAS STEVEN L. , RASHIDI RASSOLL , MCALISTER HUGH , CORBELLI RICHARD , MCCOWAN RONALD , WILKOFF BRUCE L. , CASTLE LON W. , MORANT VICTOR A. , SIMMONS TONY W. , MALONEY JAMES D.
Published: July 2006

BALLAS, S.L., et al.: The Use of Beep‐O‐Grams in the Assessment of Automatic Implantable Cardioverter Defibrillator Sensing Function Noninvasive assessment of sensing performance in the automatic implantable cardioverter defibrillator is limited by the absence of telemetry or memory /unctions. The adaptation of the electrophysiological test mode into a “beep‐o‐gram” recording, with simultaneous audible tones and a surface electrocardiogram. was used in the confirmation of sensing maffunction. Eleven of 13 recordings in patients with documented or clinically suspected inappropriate defibrillator discharges (group 1) demonstrated evidence of definite oversensing. Nonspecific oversensing or undersensing was present in 77% of 27 randomly selected asymptomatic patients without known sensing malfunction (group 2). The sensitivity and specificity for identifying definite oversensing was 85% and 60%, respectively. The beep‐o‐gram system is a reliable, noninvasive means of confirming sensing malfunction in the automatic implantable cardioverter defibrillator. Its specificity is limited by the detection of subclinical sensing aberrations, to some degree related to the device's automatic gain controi sensing algorithm.
The Duration of the Sinus Node Depolarization on Transvenous Sinus Node Electrograms Can Identify Sinus Node Dysfunction and Can Suggest Its Severity
Authors: REIFFEL JAMES A. , ZIMMERMAN GAIL
Published: July 2006

REIFFEL, J.A., et al.: The Duration of the Sinus Node Depolarization on Transvenous Sinus Node Electrograms Can Identify Sinus Node Dysfunction and Can Suggest Its Severity Catheter recorded sinus node electrograms (SNE) allow visualization of sinus node depolarization (SND). The SND on a bipolar SNE is probably a composite reflecting both P cell action potentials and intranodal conduction. Reduced rate of rise, prolonged action potential duration and/or delayed intranodal conduction might each prolong the SND duration. Thus, SND duration might reflect several clinically important sinus node abnormalities and aid in the recognition of sick sinus syndrome. Moreover, the SND duraiion might be expected to be the most prolonged in patients with the most severe sinus node dysfunction. To test this hypothesis, we determined SND duration in 32 patients and correlated it with the presence or absence of evidence of sinus node dysfunction by ECG and/or electrophysiological (EP) studies. Seven patients had no sinus node dysfunction (group 1); 10 patients had mild sinus node dysfunction (a single abnormality of corrected sinus recovery time, sinoatrial conduction time, PCLp, or ECG) (group 2); and 15 patients had two or more abnormalities electrocardiographically and/or by EP testing (group 3). The SND duration (mean/ range) was 229/95‐ 190 msec in group 1, 151/95–225 msec in group 2, and 196/140–260 msec in group 3. In group 3, three patients who had ECG evidence of sick sinus syndrome and abnormalities on all three EP parameters, the SND duration was 230/200–260 msec. Carotid sinus massage (CSM) was found to prolong the SND duration in 5/7 patients in groups 2 and 3 where the SND could be measured both before and during CSM. CSM was necessary to allow visualization of the SND in 3/7 group 1 patients; thus their recorded values may be falsely long. The only normal with a SND duration >150 (190 msec) had it measured during CSM. None of the group three patients with SND duration < 150 msec had a prolonged CSRT or ECG evidence of sick sinus syndrome. Literature review revealed SNE recordings on 18 patients with sick sinus syndrome on which the SND duration could be measured; it was 200 msec in all. Thus, the SND duration appears to reflect the presence and degree of sinus node dysfunction. Sinus node dysfunction appears unlikely if the SND duration is >150 msec and is likely to be severe if the SND duration is <200 msec.
Circadian Variations of Heart Rate and STIMT Interval: Adaptation for Nighttime Pacing
Authors: DJORDJEVIC MILAN , KOCOVIC DUSAN , PAVLOVIC SINISA , VELIMIROVIC DUSAN , KOSTIC DUSAN
Published: July 2006

DJORDJEVIC, M., et al.: Circadian Variations of Heart Rate and STIM‐T Interval: Adaptation for Nighttime Pacing. In order to determine the optimal pacing rate for pacemaker patienfs at night, 150 normal subjects with regular sinus rhythm and free of manifest heart disease, were studied using 24‐hour Rolter monitoring. Minimum and average heart rates were analyzed on an hourly basis. The study group was divided into six age groups, 25 subjects each, ranging from 20–29 years to 60–69 years. The minimum heart rate during the night was found to be lower than 65 ppm for all groups. The youngest subjects showed the largest variation in the minimum heart rate. The results suggest that an automatic lowering of the pacing rate during the night would allow for longer periods of sinus rhythm, thereby improving hemody‐namic performance and reducing pacemaker power consumption. Suitable sensors for automatic lowering of the pacing rate include inbuilt 24‐hour clock systems and the QT interval that lengthens during sleep.
Transcatheter Electrical Ablation of Accessory Pathways in Children
Authors: BROMBERG BURT I. , DICK MACDONALD , SCOTT WILLIAM A. , MORADY FRED
Published: July 2006

BROMBERG, B.I., et al.: Transcatheter Electrical Ablation of Accessory Pathways in Children. Supraventricular tachycardia (SVT), the most common sustained symptomatic arrhythmia of childhood, is often supported hy a manifest or concealed accessory pathway. Permanent interruption of the accessory pathway usually requires surgical division. Recent experience with electrical ablation of posterior septal pathways in adults prompted us to apply the technique to children. Six children, ages 8 to 15 years, underwent a complete electrophysiological study followed by transcatheter electrical ablation. Five of the 6 children, 3 with a right posterior septal and 2 with a left posterior septal pathway, were approached with the ablation catheter at the os of the coronary sinus. In the remaining patient, a left lateral pathway was mapped with an electrode catheter in the coronary sinus and then approached with the ablation catheter through the patent foramen into the left atrium. Two patients are asymptomatic 18–24 months postabla‐tion; one patient had return of anomalous conduction between 7 and 21 days after ablation. Two patients had transient interruption of anomalous conduction, whereas one patient experienced no effect. We conclude that in carefully selected patients, transcatheter electrical ablation ofers an alternative to surgery for permanent interruption of an accessory pathway. (PACE, Vol. 12, November 3989)
Modified Magnet Test for a Reversed Automatic Implantable Cardioverter Defibrillator
Authors: GERING LAWRENCE E. , RUSKIN JEREMY N. , GARAN HASAN
Published: July 2006

GERING, L.E., et al.: Modified Magnet Test for a Reversed Automatic Implantable Cardioverter Defibrillator We present the case of a 55‐year‐old man with atrial septal defect and cardiomyopathy who underwent implantation of an automatic cardioverter defibrillator (AICD) for ventricular tachycardia resulting in collapse. This case demonstrates multiple unusual complications related to AICD, including rotation of the pulse generator unit about its long axis requiring a “left‐handed” magnet test to determine the appropriate counts.
Inadvertent Catheter‐Induced Right Bundle Branch Block in a Patient with Preexistent Left Bundle Branch Block and Recurrent Macroreentrant Ventricular Tachycardia
Authors: GÖSSINGER HEINZ D. , SIOSTRZONEK PETER , WAGNER LUDWIG , LEITHA THOMAS , MÖSSLACHER HERBERT
Published: July 2006

GÖSSINGER, H.D., et al.: Inadvertent Catheter‐Induced Right Bundle Branch Block in a Patient with Preexistent Left Bundle Branch Block and Recurrent Macroreentrant Ventricular Tachycardia This article describes the inadvertent, catheter‐induced induction of right bundle branch block resulting not only in transient complete infra‐His heart block but also in temporary interruption of the macroreentry circuit of ventricular tachycardia. A patient with preexistent left bundle branch block and spontaneous ventricular tachycardia based upon the bundle branch reentry mechanism underivenf electrophysiological testing for the evaluation of sotalol drug efficacy. In search of an optimal His‐bundle recording, the manipulation of a 6 Fr quadripolar catheter caused a right bundle branch block, thus advancing the preexistent left bundle branch block to complete heart block. Retrograde ventriculoatrial conduction remained unaffected. The macroreentrant tachycardia with left bundle branch block configuration was no longer inducible. While the patient continued on unchanged sotalol medication (320 mg/d) he required temporary pacing for 16 hours until the block subsided. A subsequent induction attempt demonstrated initiation of the tachycardia. Finally, guided by invasive testing, the patient successfully received amiodarone therapy (300 mg/d). The patient completed an uneventful follow up of 27 months. No progression of conduction delay was observed. This case suggests that the inadvertent induction of right bundle branch block prevents the initiation of ventricular tachycardias relying on bundle branch reentry. Therefore, missed diagnosis or misinterpretation of antiarrhythmic drug efficacy might occur if there is no electrophysiological reevaluation after right bundle branch recovery.
Sequential Pulse Countershock Between Two Transvenous Catheters: Feasibility, Safety, and Efficacy
Authors: YEE RAYMOND , JONES DOUGLAS L. , KLEIN GEORGE J. , SHARMA ARJUN D. , KALLOK MIGHAEL J.
Published: July 2006

YEE, R., et al.: Sequential Pulse Countershock Between Two Transvenous Catheters: Feasihility, Safety, and Efficacy We evalualed the feasibility, safety, and efficacy of sequential pulse countershock (SqCS) delivered solely through two endocardial catheters for the termination of ventricular tachycardia (VT) and fibrillation (VF) in patients undergoing electrophysiology studies (EPS). Thirty‐four patients (31 men, 3 women) with a mean age of 56.8 ± 10.1 years were studied. Etiology of VT/VF was ischemic heart disease (n = 26), cardiomyopathy (4) repaired tetralogy of Fallot (n = 1), heart transplant (n = 1), and no identifiable heart disease (n = 2). Catheters were positioned successfully in 29 patients. These were positioned in the right ventricular apex (RVA) and the coronary sinus (CS), respectively. The RVA electrode served as the common cathode for both pulses. The two electrodes located near the right atrium/superior vena cava junction served as anode for pulse 1 while the distal CS electrodes served as anode for pulse 2. Twenty‐nine induced VT episodes with cycle length (CL) 220–370 msec were treated. SqCS successfully terminated 15 VT (100–500V) while 14 were accelerated or degenerated to VF. VTCL was longer in success ful SqCS episodes than in those that were accelerated (285 ± 17.3 vs 245 ± 30.8 msec, P < .003). Of 26 VF episodes, 21 were terminated with SqCS (500–900V) and 5 were terminated by transthoracic rescue shocks. On 2 occasions, failure to defibrillate was attributable to poor catheter position at the time of shock. No complications occurred. We conclude that SqCS delivered solely between endocardial catheter electrodes is feasible and effective using energy doses within the range of existing implantable cardioverter defibrillators.
Pacemaker‐Induced Superior Vena Cava Syndrome: Report of Four Cases and Review of the Literature
Authors: GOUDEVENOS JOHN A. , REID PETER G. , ADAMS PHILIP C. , HOLDEN MIGHAEL P. , WILLIAMS DAVID O.
Published: July 2006

GOUDEVENOS, J.A., et al.: Pacemaker‐Induced Superior Vena Cava Syndrome: Report of Four Cases and Review of the Literature Superior vena cava syndrome due to transvenous pacing leads is a rare event. We describe four cases. One occurred among 3,100 primary pacemaker insertions performed at our institution. In the other three cases the primary insertion had been performed elsewhere. Over 30 cases have been reported previously. Local infection, which preceded the development of superior vena cava syndrome in each of our four cases, and the presence of a severed retained lead, as in three of our cases, are important predisposing factors. There is no strong evidence that multiple lead insertion, if each lead remains intact, significantly increases the risk. The pathology at the site of obstruction includes thrombosis and in some cases fibrotic narrowing. Venous angiography is useful to show the site of obstruction, the extent of collateral circulation and to assess the response to treatment. Treatment should include removal of any infected pacemaker apparatus, anticoagulation and, if symptoms are of recent onset, thrombolytic therapy. Most patients improve but in those who do not angioplasty or surgical relief of the obstruction may be helpful.
Extracorporeal Shock Wave Lithotripsy and Cardiac Arrhythmias
Authors: ECTOR H. , JANSSENS L. , BAERT L. , DE GEEST H.
Published: July 2006

ECTOR, H., et al.: Extracorporeal Shock Wave Lithotripsy and Cardiac Arrhythmias Holter monitoring was performed in 400 patients undergoing extracorporeal shock wave lithotripsy (ESWL). The highest heart rate occurred before and after ESWL. During respiratory‐triggered ESWL, 30% of the patients had one or more ventricular premature beats (VES), and 7% had couplets of VES. The number of ventricular and supraventricular premature contractions was significantly lower during ECG‐triggered ESWL. Ventricular tachycardia occurred in seven patients during respiratory‐triggered ESWL, and in one patient during nontriggered ESWL. All ventricular tachycardias were nonsustained, asymptomatic, and slow. Supraventricular tachycardia was seen in nine patients. The preference of the urologist for respiratory‐triggered ESWL, conflicts with its higher incidence of ventricular arrhythmias.
Continuous Right Ventricular Volume Assessment by Catheter Measurement of Impedance for Antitachycardia System Control
Authors: KHOURY DIRAR , MCALISTER HUGH , WILKOFF BRUCE , SIMMONS TONY , RUDY YORAM , MCCOWAN RONALD , MORANT VICTOR , CASTLE LON , MALONEY JAMES
Published: July 2006

KHOURY, D., et al.: Continuous Right Ventricular Volume Assessment by Catheter Measurement of Impedance for Antitachycardia System Control Current implantable defibrillators are unable to differentiate between hemodynamically stable and unstable arrhythmias. This may result in unnecessary high energy shocks during arrhythmias that are better managed with other interventions. This study assessed the efficacy of the impedance catheter in sensing relative volumetric changes in the right ventricle as a measure of the hemodynamic status during an arrhythmia, During electrophysiological testing, 37 arrhythmias were induced in 12 patients aged 28–74 years. Rhythms recorded were: (A) hemodynomically stable tachyarrhythmias (supraventricular tachycardia and sustained monomorphic ventricular tachycardia)—21 episodes; and (B) hemodynamically unstable ventricular arrhythmias causing syncope (hypotensive ventricular tachycardia and ventricular fibrillation)—16 episodes. During unstable arrhythmias, stroke impedance (32 ± 17%), arterial systolic pressure (40 ± 11%), end right ventricular pulse pressure (15 ± 20%), expressed as percentages of corresponding sinus rhythm values, were significantly lower than in stable arrhythmias (84 ± 26%, 72 ± 8%, and 111 ± 37%, respectively); P < 0.001. There was a good correlation befween stroke impedance and mean arterial pressure during arrhythmia (r = 0.84). Impedance sensing is a practical method for distinguishing between hemodynamically stable and unstable arrhythmias. Implementation of hemodynamic sensing into the algorithm of future antitachycardia systems may improve the management of arrhythmias by adding options for selective pace termination or cardioversion.
Interpolating Unipolar Epicardial Potentials from Electrodes Separated by Increasing Distances
Authors: BLANCHARD SUSAN M. , DAMIANO RALPH J. , SMITH WILLIAM M. , IDEKER RAYMOND E. , LOWE JAMES E.
Published: July 2006

BLANCHARD, S. M., et al.: Interpolating Unipolar Epicardial Potentials from Electrodes Separated by Increasing Distances In cardiac mapping, potentials for unexplored areas are estimated by interpolating values from nearest neighbor electrodes regardless of distances between these sites or wave front orientation. The effects of these variables on interpolated unipolar electrograms were analyzed two ways: with a computer model and with electrograms recorded 9.9 and 14.1 mm apart. For the model, wave fronts (n = 39) were generated from electrograms recorded during right ventricular (RV) activation in five dogs following the RV isolation procedure. Each wave front was assumed to propagate radially at 0.5 m/sec from a site 30 mm from the center of a square array with electrodes located at the center and corners. Each wave front crossed the array with its tangent at an angle of 0°, 45°, or 90° to the diagonal line connecting opposite corner electrodes. Potentials for all five sites were generated from each wave front and were interpolated for the center site from the generated corner potentials. Generated and interpolated center site potentials were compared using correlation coefficients (r) and percent root mean square differences (%RMSD). Mean r values fell below 0.90 for interelectrode distances of 15.6 mm, 2.8 mm, and 1.4 mm at 0°, 45°, and 90° wave front orientations, respectively. For experimentally measured potentials recorded 9.9 mm apart, results from interpolated electrograms were similar to results from the model at 0° propagation. Electrograms interpolated from potentials measured 14.1 mm apart had poorer r and %RMS values than those from the computer model. Thus, with linear interpolation unipolar electrograms can be inaccurately interpolated from electrodes less than 3 mm apart or correctly interpolated from electrodes more than 14 mm apart depending upon wave front orientation.
A Comparison of Platinized Grooved Electrode Performance with Ring‐Tip Electrodes
Authors: MIDEI MARK G. , JONES BENJAMIN R. , BRINKER JEFFREY A.
Published: July 2006

One of the determinants of the capture threshold of an endocardial pacing lead is the configuration of the electrode tip. To evaluate whether micro‐ and macroporous electrodes have better initial and chronic thresholds than nonporous electrodes, acute and chronic capture thresholds, stimulation impedance and sensing thresholds were determined in 22 patients in whom a ventricular ring‐tip electrode and a unipolar, dual chamber pacemaker with bidirectional teiemetry had been implanted. These values were compared to those obtained from 25 patients receiving an electrode constructed with a platinized groove surface at the time of implant of an identical pulse generator. The ventricular capture threshold at implant was 0.7 V ± 0.3 at 0.6 msec pulse width for both groups. The capture threshold was significantly greater in the ring tip electrode group at follow‐up periods of 1 month (1.1 V ± O.5 vs 1.6 V ± 0.6, P < 0.008), 4 months (1.0 V ± 0.2 vs 1.7 V ± 0.8. P < 0.002), and 10 months (1.2 V ± 0.4 vs 1.7 V ± 0.5, P < 0.04) following implantation. The stimulation impedance at the time of implantation was lower in the ring‐tip electrode group (530 ohms vs 603 ohms, P < 0.03), but thereafter no significant difference was seen between the two groups. The acute and chronic sensing threshoids ivere similar in both groups. While the microporous electrode had significantly lower chronic capture threshoids, the magnitude of this difference is small, and probably clinically inconsequential. Since three patients with ring‐tip electrodes and two patients with microporous electrodes had at least one chronic threshold exceeding 2.5 V, periodic threshold determination is prudent in all patients.
Epicardial Mapping: Ventricular Epicardial Activation is Unaffected by Heart Position
Authors: PAUL THOMAS , MORRIS CODY , GARSON ARTHUR
Published: July 2006

Epicardial ventricular mapping was performed in five dogs during sinus rhythm with a sock array containing 41 bipolar electrodes. Maps were generated with a computer‐assisted mapping system when the heart was in situ and when the heart was lifted by 44° out of the chest. Times of earliest and latest epicardial activation in these two states did not differ. Despite a different frontal plane QRS axis, location of earliest activation was not affected by lifting the heart. In two of the five animals, the site of latest epicardial activation was minimally different from the heart in situ, but the general pattern of epicardial activation was unchanged. Therefore, the change in frontal plane QRS axis with lifting the heart was due to a change in heart position rather than a general change of heart activation.
Chronic Rapid Atrial Pacing to Maintain Atrial Fibrillation: Use to Permit Control of Ventricular Rate in Order to Treat Tachycardia Induced Cardiomyopathy
Authors: MOREIRA DALMO A.R. , SHEPARD RICHARD B. , WALDO ALBERT L.
Published: July 2006

LR was a patient, followed over a 16‐year period, who presented with an atrial tachycardia which was initially intermittent, but became incessant. Neither the atrial tachycardia nor the associated rapid ventricular response rate could be treated successfully with available drug therapy, resulting in a dilated cardiomyopathy and New York Heart Association (NYHA) class III‐IV congestive heart failure. Acute induction of atrial fibrillation with rapid atrial pacing demonstrated that the associated ventricular rate could be satisfactorily slowed with digitalis therapy. Initially, short bursts from an implanted, radiofrequency controlled, patient activated pacemaker programmed to a rate of 600 bpm and connected to a permanent endocardial atrial J lead successfully interrupted the tachycardia and precipitated atrial fibrillation. Over a period of 3 months, this therapy changed the patient's heart failure to NYHA class II status. Subsequently, precipitation of atrial fibrillation with this technique failed, resulting in return to NYHA class III‐IV congestive heart failure. Therefore, a custom‐designed, high rate, rate‐programmabie pacemaker was implanted to pace the atria rapidly and continuously to maintain atrial fibrillation. A pacing rate of 375 bpm plus digoxin slowed the ventricular rate to 70–80 bpm, with stabilization of the congestive heart failure to NYHA class II. The pacemaker generator was replaced 6 months later, and after another 5 months, pacing was discontinued. The patient's subsequent rhythm remained stable atrial fibrillation with clinically successful control of both the ventricular rate and heart failure (NYHA class II) until the patient's death 72 months later. This unique case demonstrates another form of chronic therapy which, in selected cases, can be used for the long term control of rapid ventricular response rates to supraventricular arrhythmia.
Improved Rate Responsive Algorithm in QT Driven Pacemakers—Evaluation of Initial Response to Exercise
Authors: DEN HEIJER PETER , NAGELKERKE DICK , PERRINS E. JOHN , HORSTMANN ECKHARD , VAN WOERSEM RUURD J. , NIEDERLAG WOLFGANG , JORDAENS LUC , DE WILDE PHILIPPE , HAMELEERS AD J. , BOUTE WIM , LIE HENK
Published: July 2006

The QT pacemaker is a rate modulated pacemaker that uses the evoked QT interval as an indicator to determine its optimal pacing rate. Despite the generally favorable clinical results with this form of pacing, some flaws in the system have been reported, such as the frequently observed rather slow initial response of the pacing rate to physical exercise, and the phenomenon of oscillation of the heart rate. These problems can be attributed to the rate adaptive algorithm used in the current QT pacemaker. Recently, in a reexamination of the relationship between evoked QT interval and pacing rate, a curvilinear relationship between these parameters has been demonstrated. As a result, a new algorithm has been developed for the next generation of the QT pacemaker. Before this new algorithm was implemented in new impiantable devices, it was evaluated in a multicenter clinical investigation, with emphasis on the initial response of the pacing rate to exercise. This study was carried out by means of special software in the programmer of the QT pacemaker. By employing real‐time bidirectional telemetry, it was possible to submit the study population, consisting of 37 patients with implanted QT pacemakers of the current generation, to identical exercise tests. Comparing these exercise tests, it appears that a considerable gain in speed of response to exercise can be achieved by using the same sensor with a faster reacting, nonlinear rate adaptive algorithm.
His Bundle Ablation with the Laser Thermal Probe (“Hot Tip”): A Feasibility Study
Authors: ROSENTHAL ERIC , MONTARELLO JOE K. , BUCKNALL CLIFFORD A. , FAGG NUALA , CURRY PAUL V.L.
Published: July 2006

Successful percutaneous ablation of the bundle of His requires accurale localization together with delivery of the minimum effective energy to avoid unwanted effects. The energy output from laser sources can be controlled very precisely but is not easily directed to the bundle of His using conventional fiber optics. The laser thermal probe (“hot tip”) consists of an optical fiber and a terminal metal cap that is rapidly heated during energy delivery. When applied to cadaver hearts at energies of 100–150 joules (10 watts for 10–15 seconds) the 2.0‐mm diameter peripheral artery probe was able to damage the bundle of His without extensive surrounding damage. The right ventricular free wall and interventricular septum were perforated during some applications at these energies leaving a tract with a diameter of less than 2.0 mm. The atrioventricular (AV) membranous septum, Foramen Ovale, right atrial appendage, and septal leaflet of the tricuspid valve were more resistant at these energy levels and perforations were always less than 1.0 mm in diameter. The probe was modified for use during electrophysiological studies and good quality unipolar electrograms were recorded from the metal cap confirming that the probe could be accurately positioned adjacent to the bundle of His. The laser thermal probe deserves further study as a “self directing” ablation tool.
Functional Electrical Stimulation: An Overview
Authors: HAMBRECHT F. TERRY
Published: July 2006

The development of future neural prostheses involves much more than connecting commercially available stimulators to disabled individuals. Safe and effective operation of prostheses requires fundamental studies of the electrode‐tissue interface. The electrochemistry of the interface must be controlled to prevent toxic byproducts. Histopathological studies of stimulated tissue are necessary to establish safe limits of stimulation and to determine mechanisms of neural damage when it does occur. Electrophysiological studies elucidate which neural pathways are excited and help in the design of more selective electrode arrays. Biomaterials are required that protect the implant from the hostile environment of the body. Presently available materials are being improved and totally new materials are being developed. One of the goals of neural prostheses developers is a nonhermetic packaging material that can be applied to miniature implants without appreciably increasing their size. The techniques used to make integrated circuits on silicone substrates are ideally suited to making ultraminiature electrodes with self‐contained electronic signal processing. Both integrated circuit stimulating and recording electrodes are being designed and fabricated.
Atrial Refractory Periods after Atrial Premature Beats in Patients with Paroxysmal Atrial Fibrillation
Authors: CHAUVIN MICHEL , BRECHENMACHER CLAUDE
Published: July 2006

To study the effects of an atrial premature beat on atrial refractory periods, we investigated 11 patients (group A) who were the control group, 12 patients suffering from paroxysmal atrial fibrillation (group B), and 10 patients (group C) without arrhythmias but with cardiopathy or cardiomyopathy. At every eighth complex of a constant atrial electrostimulated rhythm a fixed premature extrastimulus was introduced, and effective and functional refractory periods (ERP and FRP) were measured in three different sites of the right atrium, before and after introduction of this extrastimulus. Average ERP and FRP shortened respectively in group A, from 220.28 ± 25.68 msec and 281.17 ± 28.15 msec before extrastimulation, to 190.58 ± 22.74 msec and 245.88 ± 19.86 msec after; in group B, from 219.44 ± 27.38 msec and 284 ± 30.06 msec to 191.66 ± 28.72 msec and 253.23 ± 34.01 msec; and in group C from 229.03 ± 29.65 msec and 289.67 ± 51.62 msec to 194.19 ± 24.6 msec and 237.74 ± 39.59 msec. The average dispersions of ERP and FRP in group A were, respectively: 41.81 ± 21.36 msec and 36.36 ± 18.04 msec before extrastimulation, 28.18 ± 18.14 msec and 35.45 ± 15.72 msec after. In group B: 26.66 ± 19.46 msec and 41.66 ± 16.96 msec versus 45.83 ± 23.91 msec and 45 ± 34.77 msec and in group C: 27 ±11.59 msec and 45 ± 29.15 msec versus 29 ± 18.52 and 27 ± 18.88. It is concluded that an atrial premature beat tends to shorten the dispersion of atrial refractory periods when patients are free of arrhythmias, and to lengthen them when paroxysmal atrial fibrillation are documented.
Pacing Rate Increase as Cause of Syncope in a Patient with Severe Cardiomyopathy
Authors: MOREIRA LUIZ FELIPE P. , COSTA ROBERTO , STOLF NOEDIR A.G. , JATENE ADIB D.
Published: July 2006

Hemodynamic deterioration occurs with ventricular pacing rate increase in the presence of severe chagasic cardiomyopathy. Syncope and orthopnea occurred during ventricular pacemaker evaluation when the pacing rate was temporarily increased by magnet application. Cardiac output decreased by 54%, the arterial blood pressure by 38%. and the pulmonary wedge pressure increased by 54%. Such severe myocardial compromise may limit the use of rate modulated pacemakers.
Iliac Vein Approach to Permanent Pacemaker Implantation
Authors: ELLESTAD MYRVIN H. , FRENCH JAMES
Published: July 2006

Since July 1980, 90 patients have had 95 permanent pacemakers implanted via an iliac vein approach. An incision is made superior to the inguinal ligament and the iliac vein is cannulated with a single lead for the ventricle or two leads for the atrium and ventricle. The pulse generator is placed in the subcutaneous tissue of the abdomen lateral to the umbilicus via a second incision. Overall 28 pacemaker implants were for atrial pacing, 53 for ventricular pacing and 14 were dual chamber. Nine (21%) of the atrial leads displaced and required repositioning and 5 (7%) of the ventricuiar leads dislodged and required revision. Lead dislogement, especially in the atrium, remains a major weakness of the approach, and decreases its utility. Eleven percent of the last 19 atrial leads have dislodged. Nevertheless, the method is simple to perform and is presented as an alternative to the usual pectoral implantation site.
Pleomorphic Ventricular Tachycardia: Demonstration of Conduction Reversal Within the Reentry Circuit
Authors: KUCK KARL‐HEINZ , SCHLÜTER MICHAEL , KUNZE KLAUS‐PETER , GEIGER MANFRED
Published: July 2006

A case is presented of a patient with incessant venfricular tacbycardia of left bundle branch block morphology. Endocardial mapping revealed the site of earliest activation during tachycardia to be the proximal right ventricular septum. Pacing at this site elicited the clinical tachycardia, whereas pacing at the proximal left ventricular septum induced a right bundle branch block morphology identical to that of a previously recorded spontaneous ventricuiar tachycardia. Electrophysiological evidence is given that both types of tachycardia originate from a single reentry circuit located in the proximal ventricular septum in which the reentrant wavefront may travel either orthodromically (during spontaneous tachycardia and right ventricular pacing) or antidromically (during left ventricular pacing).
Effects of Different Pacing Modes on Left Ventricular Relaxation in Closed‐Chest Dogs
Authors: LITWIN SHELDON E. , GORMAN GRACE , HUANG SHOEI K. STEPHEN
Published: July 2006

Ventricular relaxation is an important determinant of ventricular filling; impaired relaxation may decrease cardiac output and stroke volume. Relaxation hos been shown to occur more quickly following beats with an increased extent of systolic fiber shortening. Since cardiac output and stroke volume are greater during atrioventricular (AV) sequential pacing than during ventricular pacing at identical heart rates, we reasoned that AV sequential pacing would improve relaxation. To assess this hypothesis we studied 11 dogs with chronic (1‐3 months) complete heart block (CHB) induced by radiofrequency catheter ablation of the His bundle. Right and left heart pressures, thermodilution cardiac output, und single plane ventriculography were recorded during baseline rhythm (CHB), and VVI, and AV sequential pacing at a heart rate greater than the sinus rate. None had ventriculoatrial conduction. During AV sequential pacing, the AV interval was set at 150 msec. Cardiac output and stroke volume were significantly increased in the AV sequential compared to the VVI pacing mode. Left ventricular pressures, maximal positive and negative dP/dt, and the time constant (T) of isovolumic pressure decay were not different in the two modes. We conclude that despite increased stroke volume in the AV sequential pacing mode, relaxation is unchanged. We believe the lack of change in relaxation is due to nonuniform ventricular activation when depolarization is initiated at the right ventricular apex.
Catheter Ablation Without Fulguration: Design and Performance of a New System
Authors: AHSAN ARIF J. , CUNNINGHAM DAVID , ROWLAND EDWARD , RICKARDS ANTHONY F.
Published: July 2006

A new system is described for catheter ablation which comprises a short time capacitive power source and a specially designed catheter. The aim of the new system is to deliver high voltages with minimal or no arcing and thus avoid the risks associated with barotrauma. The performance of the new system was compared in a saline tank with that of the conventional system. The new system allowed significant increases in delivered voltage, current and energy without arcing. This new system should allow safer catheter ablation.
Coagulation of Ventricular Myocardium Using Radiofrequency Alternating Current: Bio‐Physical Aspects and Experimental Findings
Authors: HAVERKAMP WILHELM , HINDRICKS GERHARD , GULKER HARTMUT , RISSEL ULRICH , PFENNINGS WINNFRIED , BORGGREFE MARTIN , BREITHARDT GUNTER
Published: July 2006

Within the last years, a variety of different energy sources has been investigated to test their feasibilty for catheter ablation of myocardial tissue. This report summarizes our experience of the use of radiofrequency alternating current (500 kHz, unipolar mode) for coagulation of ventricular myocardium in canine experiments. Under standardized in vitro conditions, we found a significant correlation between actually delivered radiofrequency energy and assesed myocardial necrosis (r = 0.87). However, this did not hold for percutaneous application of radiofrequency alternating current to the beating dog heart (r = 0.32). In the intact dog heart, the size of induced lesions paralleled catheter contact pressure which was varied until ST‐egment elevation was either 0–2 mV or 5–7 mV. However, no statistical significant differences in either calculated energy or tissue impedance were observed. Under in vivo conditions, a significant improvement in the predictability of the resulting size of lesions was observed when catheter tip temperature, measured via a built‐in Ni/CrNi thermoelement, was monitored (r = 0.07). Changes in tip temperature during coagulation also indicated the quality of catheter contact, catheter damage and the appearance of carbonization at the tip of the ablation catheter. Total perforation of the myocardial wall and proarrhythmogenic effects were only rarely observed. In conclusion, catheter coagulation of myocardial tissue using radiofrequency energy can be considered as safe and effective. Since changes in catheter tip temperature occurring during coagulation were found to predict the extent of induced tissue necrosis, the development of temperature controlled radiofrequency devices seems promising and necessary.
Fulguration of Accessory Pathways in any Location: Report of Seventy Cases
Authors: WARIN J.F. , HAISSAGUERRE M.
Published: July 2006

Ablation of accessory pathways (AP) in any location was performed in 70 consecutive patients using either a right or a left approach. Left free wall pathways were approached via a patent foramen ovale (eight patients) or by transseptal catheter (eight patients). The best ablation site was localized by recording a potential most likely due to Kent bundle activation (33/70 patients), the earliest site of retrograde atrial activation during orthodromic reciprocating tachycardia, earliest ventricular potentials recorded before or synchronous with the delta wave in standard ECG leads, disappearance of preexcitation due to pressure of the catheter on the AP (eight patients), good degree of pacemap concordance with ventricular preexcitation. Two 160 joules cathodal shocks in close succession were delivered and the sequence reeated depending on the results. Preexcitation disappeared in 63 patients and there was no recurrence of arrhythmia in 68 patients without any antiarrhythmic therapy over a follow‐up ranging from 1 to 42 months. No serious side effects were observed except for two patients who developed permanent complete AV block. However, one of them occurred after an unsuccessful surgical attempt which had damaged the AV function. Fulguration is effective for APs in diverse locations. These results indicate that appropriate treatment of patient with the Wolff‐Parkinson‐White syndrome should be reassessed. At present, the therapy of arrhythmias related to the Wolff‐Parkinson‐White syndrome is no longer a question of either antiarrhythmic drugs or surgery. Fulguration, in our experience, is effective for abolishing accessory pathways in any location.
Advances in Catheter Ablation use of Unipolar Electrograms
Authors: FLETCHER ROSS , SWARTZ JOHN , LEE BENJAMIN , COHEN ANDREW , WISH MARK , JONES JANICE
Published: July 2006

Ventricular tachycardia in man can be eliminated by relatively small lesions in the reentrant circuit. This report includes a review of available energy sources, and methods for localizing arrhythmias. Methods to assure contact and prevent perforation using low frequency electrograms are presented including the new finding of reverse ST deflection with contact. Experience with laser energy in dogs showed discrete homogenous lesions. When compared with DC shock the animals showed far less arrhythmia and the lack of far field effect greatly reduced echo abnomalities in the post shock period. Studies with radiofrequency show ability to produce localized lesions similar to the laser but with a more flexible catheter. Localization requires a correlation of techniques including pacemapping, activation maps and pacing during tachycardia. Early activation (< −60 ms) at times 180–320 ms, with comparable pace to QRS during tachycardia with no change in morphology best localized the slow zone of the reentrant circuit. The low frequency unipolar electrogram from the tip and immediately proximal electrode revealed contact with ST deviation. The distal deviation was always greater than the proximal RV free wall and posterior basal produced depression rather than elevation of the electrogram. While the mechanism of ST reversal with contact is not understood and may relate to the type of indifferent reference used (Wilson central terminal), the ST depression reveals the same information about contact that elevation does in most other areas of the heart studied in our patients.
Use of Transient Entrainment During Ventricular Tachycardia to Localize a Critical Area in the Reentry Circuit for Ablation
Authors: WALDO ALBERT L. , HENTHORN RICHARD W.
Published: July 2006

We have previously shown that demonstration of any of the criteria for transient entrainment is possible only when pacing is performed orthodromically proximal to the area of slow conduction in a reentrant circuit with an excitable gap. Pacing orthodromically distal to the area of slow conduction will not permit demonstration of the transient entrainment criteria (concealed entrainment). Additionally, the demonstration of one form of concealed entrainment, namely pacing during a ventricular tachycardia from a site which increases the tachycardia to the pacing rate but does not change the morphology of the QRS complexes, we suggest also identifies the area of slow conduction is a keystone for maintenance of the reentrant circuit, ablation of this area should be expected to provide effective therapy of the tachycardia. Thus, we propose that using the principles of transient entrainment, one should be able to localize a critical area of slow conduction in the reentrant circuit of Q ventricular tachycardia, ablate it effectively, and thereby successfully treat the ventricular tachycardia.
Fulguration of Ventricular Tachycardia Using High Cumulative Energy: Results in Thirty‐one Patients with a Mean Follow‐Up of Twenty‐seven Months
Authors: HAISSAGUERRE M. , WARIN J.F. , LEMETAYER Ph. , GUILLEM J.P. , BLANCHOT P.
Published: July 2006

Catheter electrical ablation of ventricular tachycardia (VT) was attempted in 31 patients (57 ± 15 years) who had refractory recurrent VT. Fifteen patients had coronary artery disease, seven had arrhythmogenic right ventricular dysplasia, four had cardiomyopathy and five had no structural heart disease. Ten patients were NYHA class III‐IV. Ten patients experienced cardiac arrest or syncope during VT. Twenty‐two patients had only one documented morphologic type of spontaneous VT. Whereas nine patients had more than one: the VT was incessant or daily in 17 patients. One to 16 shocks (mean 5.6) of 160 to 240 joules each (1162 ± 1060 joules) were delivered to the endocardial exit site of VT—as identified by endocardial activation mapping (29 patients) and pacemapping (31 patients)—during one (22 patients) or more than one session (nine patients). Cumulative delivered energy was 840 ± 558 joules for right ventricular VT (11 patients) and 1362 ± 1240 joules for left ventricular VT (20 patients). Reversible side effects occurring immediately after shocks included: nonclinical VT (two patients), ventricular fibrillation (two patients), AV block (three patients). Mean CK—MB fraction 6 hours after shocks was 93 ± 46 IU/1. An electrophysiology study performed 7 to 10 days later demonstrated that the original clinical VT was inducible in seven patients, nonclinical monomorphic VT was inducible in eight patients and no VT was inducible in 13 patients. The procedure was successful in 25/29 patients (86%) who had no recurrence of the original VT (or sudden death) either on no antiarrhythmic therapy (16 patients) or on the same regimen that was ineffective before ablation (nine patients) over a follow‐up period of 27 ± 11 months. A nonclinical VT occurred in two patients. The ablation result was not interpretable in two patients and unsuccessful in four patients: the endocardial activation time at site of shocks was –5 ± 5 ms in the failures versus −43 ± 29 ms in the successes (P < 0.05).
Bundle Branch Reentrant Tachycardia Treated by Transvenous Catheter Ablation of the Right Bundle Branch
Authors: VOLKMANN H. , KÜHNERT H. , DANNBERG G. , HEINKE M.
Published: July 2006

Recurrent episodes of ventricuiar tachycardia not responding to medical treatment occurred in a 56‐year‐old man. Electrophysiological investigation showed ventricular tachycardia due to bundle branch reentry. Using a method similar to catheter ablation of the atrioventricular junction, ablation of the right bundle branch was performed by an electrical shock of 250 joules. While before the ablation ventricular tachycardia occurred several times a day and its induction by programmed ventricular stimulation was facilitated by the administration of antiarrhythmic drugs, no initiation of ventricular tachycardia was possible after ablation of the right bundle branch. Over a follow‐up of 30 months the patient has not suffered from tachycardia and the right bundle branch block persists.
The Effect of Chronic Oral and Acute Intravenous Amiodarone Administration on Ventricular Defibrillation Threshold Using Implanted Electrodes in Dogs
Authors: FRAME LAWRENCE H.
Published: July 2006

The effect of acute intravenous administration and chronic oral loading of amiodarone on defibrillation threshold was evaluated in normal anesthetized dogs using implanted superior vena caval spring and left ventricular patch electrodes. The effect of oral loading with amiodorone was evaluated by comparing three groups of six dogs each that received either no drug, 200 mg/day for 9 days, or 400 mg/day for 9 days. Defibrillation threshold was evaluated by administering a fixed sequence of shocks with increasing energies until defibrillation was successful. Defibrillation was determined 13 times in each animal. The mean defibrillation threshold (plus or minus standard error of the mean) was 7.5 ± 0.3 J in the control group, 15.4 ± 0.6 J in the group receiving amiodarone 200 mg/day, and 17.9 ± 0.8 J for the group receiving 400 mg/day. These values are significantly different using analysis of variance and Tukey's test. The acute effect of intravenous amiodarone, 5 mg/Kg was evaluated in five dogs using each dog as its own control. The mean defibrillation threshold during control period was 10.8 ± 0.4 J, and during the first two hours after amiodarone administration was 10.8 ± 0.4 J. There was no significant difference. Thus, in this study oral administration of a loading dose of amiodarone comparable to that used in patients produced a dose dependent increase in defibrillation threshold, whereas no change in defibrillation threshold was observed acutely after intravenous administration.
VOOR—Nondemand Rate Modulated Pacing Necessitated by Myopotential Inhibition
Authors: VOLOSIN KENT J. , RUDDEROW ROSEMARY , WAXMAN HARVEY L.
Published: July 2006

This report describes the use of the temperature sensitive rate modulated nondemand pacing mode (VOOR) in a patient with significant myopotential inhibition of pacemaker output during exercise. The VOOR mode eliminated myopotential sensing which had prevented an exertion related increase in heart rate. The patient has done well with VOOH pacing for the past year. VOOR pacing is useful in selected cases.
Long‐Term Internal Cardiac Defibrillation Threshold Stability
Authors: WETHERBEE JULE N. , CHAPMAN PETER D. , TROUP PAUL J. , VESETH‐ROGERS JAN , THAKUR R.K. , ALMASSI G. HOSSEIN , OLINGER GORDON N.
Published: July 2006

The automatic implantable cardioverter‐defibrillator is tested intraoperatively with defibrillation trials to ensure effectiveness. It is unknown if the energy requirement for internal defibrillation remains stable and that once demonstrated effective, if the device will continue to be effective in terminating lethal ventricular arrhythmias. In this study, the defibrillation energy requirement was compared in 56 patients at the time of lead implantation to that obtained at the time of generator replacement. Mean time to generator replacement was 17. ± 6.6 months. The defibrillation threshold was stable over that time (11. 9 ± 6.7 joules compared to 12.7 ± 8.4 joules, NS). There was no relation between transmyocardial impedance and defibrillation threshold. In addition, no effect on defibrillation threshold was demonstrated by the use of various cardiac medications, concomitant surgery or the occurrence of clinical shocks during follow‐up.