bluuebunny/crossref_metadata_2025 huggingface dataset:
Programmed Chest‐Wall Stimulation to Evaluate the Progress of A‐V Block After Pacemaker Insertion in Patients with Trifascicular Disease
Authors: MARINATO PIER GIORGIO , BRESSAN MARTA , BUJA GIAN FRANCO , NAVA ANDREA , BARBIERO MARIO , VERLATO ROBERTO , VOLTA SERGIO DALLA
Published: July 2006

Twenty six patients faged 46‐80, mean age 64) with bifascicular block in the presence of prolonged H‐V interval (trifascicular block), were followed for an average of 31 months after inserting an R‐wave inhibited pacemaker (PM) because of syncope and/or dizzy attacks. The underlying rhythm was evaluated at 4–6‐month intervals by three different techniques; 1) 12‐lead ECG when intrinsic patient rate was faster than PM rate; 2) abrupt PM inhibition (APMI) by the rapid chest‐wall stimulation technique, and 3) progressive PM inhibition (PPMl) using a programmed chest‐wall stimulation technique capable of decreasing the PM rate gradually to 30 beats/min before complete PM inhibition. In addition, (he PPMl allowed the underlying rhythm to be induced and sustained and properly evaluated without any discomfort to the patient. Following PM insertion, 4 patients (15%) developed complete hear! block after a mean follow‐up of 43 months, and one patient (4%) developed 2nd degree 2:1 A‐V block (VX) after 83 months. The P‐R interval increased in 5 patients (19%) and decreased in 2 (8%j. No change of A‐V conduction was found in 9 patients (34%). Three patients developed low atrial rhythm, atrial flutter and atrial fibrillation, respectively (12%). After PM insertion 2 patients still complained of dizziness. None reported syncope. Two patients died during follow‐up, both of congestive heart failure (8%). By detection of intrinsic rhythm it was recognized that a long symptomatic paroxysmal phase may precede the development of chronic complete A‐V block. Therefore, the insertion of a permanent PM is recommended in patients with unexplained neurologic symptoms and trifascicular disease, without waiting for documented episodes of complete A‐V block. (PACE, Vol. 5, September‐October, 1982)
Postoperative Electrophysiological Studies with a Modified Radiofrequency System. Technical Aspects and Clinical Usefulness
Authors: STRASBERG BORIS , FETTER JOSEPH , PALILEO EDWIN , LEVITSKY SIDNEY , ROSEN KENNETH M.
Published: July 2006

Technical aspects and clinical usefulness. Two patients who underwent a ventricular aneurys‐mectomy for treatment of ventricular tachycardia are presented. In both patients, a radiofrequency pacemaker was implanted at surgery (for therapeutic use if surgery should fail). In both patients, elec‐trophysiological studies were performed before discharge utilizing a radiofrequency pacemaker without recourse to repeat catheterization. This was possible by modifying the transmitter and coupling it to a commercially available programmable stimulator. (PACE. Vol. 5, September‐October, 1982)
Early Follow‐Up of Lead Performance in Atrioventricular Sequential Systems
Authors: NISHIMURA RICK A. , VLIETSTRA RONALD E. , MALONEY JAMES D. , MERIDETH JOHN
Published: July 2006

Recent developments in pacemaker technology led us to report our initial and follow‐up assessment of atrioventricular (A‐V) sequential systems in 50 consecutive patients. Primary indications for pacing were sinus node dysfunction or A‐V block. Leads were introduced through the subclavian vein. Atrial J‐tined leads (27 silicone, 19 urethane) were positioned in the atrial appendage or stump in 46 patients, and coronary sinus or Bisping leads were placed in 4 patients; all 50 patients had tined ventricular leads. A Medtroric 5992 generator was placed in 35 patients and an Intermedics 259–01 generator in 15. Median implantation time was 105 minutes. Complications requiring reoperdtion in 409 patient‐nnonths of follow‐up included lead retraction (one patient), phrenic nerve stimulation (one), pseudofracture (one), and atrial lead‐induced “cross talk” (one). Monthly telephone transmission confirmed atrial capture in 35 patients and loss of capturein 1; the remainder had no identifiable P wave. Ventricular capture was confirmed in all. Postimplant and follow‐up checks showed good stability of lead positions. We conch de that these systems have a low incidence of problems in short‐term followup. (PACE, Vol. 5, September‐October, 1982)
Magnet Application, a Cause of Persistent Arrhythmias in Physiological Pacemakers. Report of 2 Cases
Authors: VAN GELDER L.M. , EL GAMAL M.I.H.
Published: July 2006

Report of 2 cases. Magent application during routine pacemaker check‐up induced persistent arrhythmias in two patients with physiological pacemakers. One patient had received an atrial synchronous ventricular demand pacemaker (VDD) because of alternating second‐and third‐degree atrio‐ventricular block. During routine pacemaker follow‐up, a magnet was applied over the pulse generator to measure the pacemaker rate. This converted the system to fixed rate ventricular pacing at a rate of 65 bpm which resulted in retrograde atrial activation. When the magnet was removed the retrograde conducted P‐waves were sensed by the atrial amplifier and the ventricular output was triggered again, causing a re‐entry pacemaker tachycardia with a rate of 175 bpm. The tachycardia could be suppressed by applying a magnet once more, but the pulse generator had to be programmed in the VVI‐mode to prevent induction of the tachycardia again. A second patient had complete atrioventricular block and left heart failure. After three years of ventricular demand pacing, we decided to implant a DDD pacemaker because of persisting left heart failure and poor exercise tolerance. During a routine visit io the pacemaker clinic a magnet was applied over the pulse generator to measure the basic rate. The system was thus converted to fixed rate A‐V‐sequential pacing (DOO) which resulted in atrial flutter. When the magnet was removed and the pulse generator returned to its DDD mode, the atrial flutter was partially sensed by the atrial amplifier, resulting in a tachycardia with a variable rate up to 125 bpm. Fortunately we were able to terminate the atrial arrhythmia by applying the magnet again. In this patient fixed rate underdrive pacing stopped the atrial arrhythmia. (PACE, Vol. 5, September‐October, 1982)
A New Multiprogrammable Isotopic Powered Cardiac Pacemaker
Authors: SMYTH NICHOLAS P.D. , PURDY DAVID L. , And DIANE SAGER. , KESHISHIAN JOHN M.
Published: July 2006

A new multi‐programmable, isotopic‐powered cardiac pacemaker was implanted in six patients as a custom device. Five were initial implants and one was a replacement The patients were studied for up to two years. In five of the six cases it was found advantageous to change one of the programmable parameters. Multiprogrammability is obviously as important in an isotopic pulse generator as in a lithium unit, if not more so, because of the unit's greater longevily, Further studies are continuing in an FDA approved clinical trial. (PACE, Vol. 5, September‐October, 1982)
The Underlying Heart Rhythm in Patients with an Artificial Cardiac Pacemaker
Authors: STAESSEN JAN , ECTOR HUGO , DE GEEST HILAIRE
Published: July 2006

One‐hundred forty‐two patients with atrioventricular block (AVB) and 61 patients with sick sinus syndrome (SSS) were followed for an average of 50 months after permanent pacemaker insertion. Their underlying heart rhythms (UHR) were evaluated repeatedly by chest wall Stimulation (CWS). A deficient UHR was defined as ventricular asystole lasting 4 seconds or longer. The underlying conduction disturbance increased in 14% of AVB patients, decreased in 14%, and remained constant in 68%. The occurrence of Adams‐Stokes attacks before pacemaker implantation was associated with a higher incidence of deficient UHR both in AVB and SSS; a deficient UHR was seen more frequently in AVB than in SSS. Among AVB patients (1) atriaJ fibrillation, flutter or tachycardia and (2) sinus rhythm with incomplete AVB, especially Möbitz 1, when present before pacemaker implantation, were associated with a significantly lower incidence of deficient UHR during subsequent pacing in comparison with other AVB patients. CWS is a non‐invasive method which allows the evaluation of UHR and which can contribute to the early recognition of pacemaker‐dependent patients.
Heart Block and Idiopathic Pulmonary Hemosiderosis
Authors: MOSES H. WESTON , SCHREINER BERNARD F. , HYDE RICHARD W. , KALLAY MICHAEL C.
Published: July 2006

A young woman with idiopathic pulmonary hemosiderosis (IPH) and advanced heart block below the atrioventricular node requiring pacemaker therapy is discussed. Thirteen years after the onset of IPH she is free of pulmonary symptoms despite having never received steroid or antimetabolite therapy.
Central Venous Oxygen Saturation for the Control of Automatic Rate‐Responsive Pacing*
Authors: WIRTZFELD ALEXANDER , GOEDEL‐MEINEN LIESELOTTE , BOCK THOMAS , HEINZE ROLAND , LISS HANS DIETER , MUNTEANU JOSEF
Published: July 2006

A rale‐adjusting pacemaker system is described which uses central venous oxygen saturation (SO2) for the regulation of the pacing rate. This system was tested externally in ten patients with chronically implanted VVI units. There was an average increase in cardiac output of 18% with the SO2‐regulated pacemaker as compared to the situation during fixed rate stimulation. Central venous oxygen saturation appears to be an ideal biological parameter for autoregulating the pacing rate. It represents the only sensor suitable for the realization of a closed feedback loop concept
Ventricular Pacing in Children
Authors: SIMON ARTHUR B. , DICK MACDONALD , STERN AARON M. , BEHRENDT DOUGLAS M. , SLOAN HERBERT
Published: July 2006

Ventricular pacing in children. Ventricular pacing was performed in forty‐one children ranging from one day to twenty years of age (median age = 10). Weight of the recipient at implant ranged from 2 kg. to 86 kg. Indications included presyncope, syncope, dyspnea on exertion, congestive heart failure, postoperative infra‐Hisian heart block, and inadequate cardiac rate during pharmacotherapy. Four patients died during follow‐up, but no deaths were attributable to pacemaker management. In contrast, 66% of the patients required more than one pacemaker related‐operative procedure, and 43% of leads implanted failed by 48 hours. Indications for permanent cardiac pacing in this population at this time are symptomatic congenital AV block, symptomatic sinus node disease, and AV block in the postoperative period. Technological developments which might reduce complications seen in this population and electrophysiologic techniques which may better define indications for pacing in children are also reviewed.
A Versatile Cardiac Electrical Stimulator for Clinical and Experimental Use
Authors: TOL R.R. , GRIMBERGEN C.A.
Published: July 2006

A cardiac electrical stimulator developed for clinical und laboratory applications is described. The stimulator has 5 separate generators and 4 output channels. The generator settings are defined by the operator using a special keyboard, with the same structure as a television screen on which all the parameters are displayed. A number of user‐specified settings can be stored in the apparatus and are available within seconds. Several programming modes provide a simple way to determine stimulation thresholds and/or refractory periods. Hardware and software security checks prevent dangerous stimulation in case of malfunction or erroneous settings. The stimulator control unit is digitally connected to constant current output stages located near the stimulation site. The stimulator functions are performed by programmable hardware controlled by a microcomputer dedicated exclusively to the presentation and inpul of stimulator settings. The application of a simple (personal) microcomputer leads to a vavorable price/performance ratio.
The Anatomic Relationship of the Esophageal Lead to the Left Atrium
Authors: BINKLEY PHILIP F. , BUSH CHARLES A. , KOLIBASH ALBERT J. , MAGORIEN RAYMOND D. , HAMLIN ROBERT L. , LEIER CARL V.
Published: July 2006

This study was undertaken to establish the “in vivo” anatomic relationship of the esophageal catheter to the left atrium. Fourteen patients, seven of whom had enlarged left atria, were included in the study. During cardiac calheterization, a bipolar recording catheter was placed in ihe esophagus; left atrial cineangiograms were then obtained in the posterior‐anterior (PA), left anterior oblique (LAO), and lateral views. The distance of the esophageal catheter, in each of four commonly used positions, to the interatrial septum‐right atrium was measured in the PA and LAO cineangiograms. The distance from the same catheter positions to the posterior left atrial wall was measured from the lateral view. In all positions and regardless of left atrial size, the catheter clearly lay behind the left atrium and was closer (0 the left atrial wall than any other cardiac structure, including the interatrial septum. Bipolar electrograms were recorded from the four commonly used esophageal locations; afrial wave amplitude and other parameters of the electrogram deflection did not vary significantly in ihe different lead positions. We conclude that esophageal electrograms reflect left atrial activity by virtue of the recording electrode's clear proximity to this structure. The amplitude and configuration of the atriai wave itself is generally not useful in determining the position of the esophageal lead.
Maximal Rate of Tachycardia Development: Sinus Tachycardia with Sudden Exercise vs. Spontaneous Ventricular Tachycardia
Authors: FISHER JOHN D. , GOLDSTEIN MARK , OSTROW ELIOT , MATOS JEFFREY A. , KIM SOO G.
Published: July 2006

In addition to providing basic physiologic information, knowledge of the maximal rate of sinus tachycardia development may be helpful in developing algorithms permitting new generations of antitachycardia pacemakers to distinguish accurately between sinus and ventricular tachycardia. To determine the maximal rate of sinus tachycardia development, 50 normal subjects rushed up 100 stairs as rapidly as possible, with continuous electrocardiographic monitoring. During the first second of exercise, the mean cardiac cycle length shortened from 709 to 570 ms, equivalent to an increase in heart rate from 85 to 105 beats per minute, or 20 beats per minute per second. Thereafter, a more gradual decrease in cycle length occurred. Differences between men and women, smokers and non‐smokers, and sedentary compared to active subjects were all insignificant. Analysis of 50 spontaneous episodes of ventricular tachycardia also revealed a sequential but more abrupt decrease in the cycle length during the first second from 757 to 360 ms, equivalent to a rate increase from 79 to 167 beats per minute, or 88 beats per minute per second. After approximately 1 1/4 seconds, the ventricular tachycardia cycle length remained virtually constant. Baseline cycle lengths were similar in the sinus and ventricular tachycardia groups, but differed in all subsequent beats, although overlap for individual subjects did occur.
Tachycardia and Apparent Sino‐Atrial Block Due to Concealed Sinus Node Re‐entry
Authors: SATAKE SHUTARO , BIANCHI JOHN , DREIFUS LEONARD S. , WATANABE YOSHIO , MICHELSON ERIC L.
Published: July 2006

The role of the middle intercavaJ area (“internodal pathway”) in the genesis of atrial re‐entry was studied using microelectrode techniques and the extra‐stimulus method in the rabbit heart. Following surgical interruption of the anterior and posterior internodal tracts, two patterns of re‐entry were observed using the middle internodaJ pathway manifesting alternatively as tachy‐ and brody‐arrhythmias. Re‐entry which was produced by critically timed extrastimulation at the septal branch of the crista terminalis (CT) caused tachycardia reciprocating between the sinus node (SN) and intercaval area. Spontaneous re‐entrant impulses were also observed, particularly following the addition of cedilanid (0.04 mg/L). In addition, in association with critical prolongation of conduction in the sino‐septal area, premature discharge of the dominant pacemaker fibers was observed and resulted in the appearance of bradyarrhythmias. These were commonly manifest as bigeminy and trigeminy on the surface septal electrogram. Hence concealed sinus node re‐entry could manifest itself as apparent sino‐atrial block or sino‐atrial re‐entry tachycardia.
One Monitored Case of Sudden Death
Authors: GOULD LAWRENCE , GOPALASWAMY C. , CHANDY F. , ABDOU O.
Published: July 2006

A 90‐year‐old female had a Holter monitoring recording because of a syncopal episode. She developed a fotal cardiac arrest during the recording. A severe bradycardia was the initialing fatal dysrhythmia. This was followed by ventricular tachycardia and fibrillation and finally cardiac standstill.
High Resolution Recordings of Atrial Flutter
Authors: BACIARELLO GIACINTO , DI MAIO FERNANDO , RUSSO GASPARE E. , SCIACCA ANDREA
Published: July 2006

We present high resolution tracings of atrial flutter which, to our knowledge, have not been previously described. Two patients have been studied; in both cases atrial activity was made by waves similar to each other, differing only in voltage. We discuss the nature of these waves, which are probably related to continuous atrial activity, with a segregation into small and large waveform activity. It is concluded that high resolution recordings may be valid support for the interpretation of atrial flutter activity.
Spontaneous Manifestation of Dual AV Nodal Pathways Resulting in Complex Patterns of AV Conduction
Authors: WARD DAVID , VALANTINE HANNAH
Published: July 2006

Dual intranodal pathways are not uncommonly demonstrated at electophysiological study1 especially in patients with intranodal re‐entrant tachycardias.2‐3 This type of tachycardia is the most common spontaneous manifestation (albeit indirect) of dual AV nodal pathways. Other forms of spontaneous expression of dual atrio‐His conduction are rare,4–6 In this report we describe a patient who exhibited complex atrioventricular conduction patterns over two intranodal pathways.
Retrograde (Ventriculoatrial) Conduction
Authors: LÉVY SAMUEL , CORBELLI JEAN‐LOUIS , LABRUNIE PIERRE , MOSSAZ ROBERT , FAUGÉRE GÉRARD , VALEIX BERNARD , SANS PHILIPPE , GÉRARD RAYMOND
Published: July 2006

Ľinterêt dans la conduction VA rétrograde a été renouvelé depuis la découverte de tachycardies induites par les stimulateurs cardiaques de type physiologique qui incorporent le recueil des potentiels auriculaires. Seule ľétude de la conduction VA rétrograde associée à une parfaite connaissance de son comportement électrophysiologique dans dif‐ferents cos, permettra de dépister les malades susceptibles de faire une tachycardie induite par le stimulateur.

Interest in retrograde VA conduction has been renewed with the advent of tachycardias induced by physiologic pacemakers with atrial sensing capabilities. Accurate representation of ventriculoatrial conduction requires detailed electrophysiologic analysis during sinus rhythm, during tachycardias whether or not associated with accessory pathways, and during ventricular pacing studies. Retrograde conduction should be assessed in patieifts considered for implantation of atrial sensing and tracking pacemakers (VAT, VDD, DDD), until technologic advances overcome the problems of endless loop tachycardias.
The Electrocardiography of AV Universal DDD Pacemakers
Authors: HAUSER ROBERT G.
Published: July 2006

Ľinterpretation des traces eJectrocardiographiques des stimulateurs DDD peut être réalisée par des techniques habituelles et par ľapplication des principes fondamentaux des recueils des potentiels, des schémes des périodes, et des caractéristiques des stimulateurs. La parfaite connaissance des paramètres de cheque modèle est obligatoire a fin ?éviter les conséquences crées par des fausses interprétations. Les constructeurs doivent fournir des renseignements précis sur les stimulateurs DDD. En plus, le milieu médical devra développer une méthode de surveillance beaucoup plus sophistiquée.

The interpretation of DDD pacemaker electrocardiograms may be performed using basic techniques and by applying the fundamental principles of noncompetitive pulse generator sensing, timing, and pacing characteristics. Precise knowledge of individual model specifications and programmable parameters is mandatory if physicians are to avoid the consequences of misinterpretation. Manufacturers must provide adequate information regarding their DDD models, and the medical community should develop more sophisticated surveillance methods for following these pacemakers.
Electrode‐Heart Interface: Definition of the Ideal Electrode
Authors: RIPART ALAIN , MUGICA JACQUES
Published: July 2006

Dans la stimulation à deux chambres, pour garder aux stimulateurs leurs avantages de petite taille, de volume réduit et de longue durée, il est nécessaire de diminuer les seuils de stimulation. Ceci peut être accompli par ľoptimisation de ľinterface électrode‐coeur. Des nouvelles électrodes pourraient réquire les pertes de polarisation; de même, des nouveaux matériaux pourraient être envisagés. Les résultats de ces données doivent être rapportés à stimulation chronique.

In dual‐chamber pacing in order to maintain the advantages of small pulse generator size and volume, and increased longevity, it becomes necessary to reduce pulse generator output. This may be accomplished by optimizing the electrode‐heart interface. New electrode designs may reduce polarization losses; perhaps even newer materials should be considered. The results of accumulated data must be applicable to long‐term pacing.
Use of Synthetic Polymers for Biomedical Application
Authors: GUERIN PHILLIPPE
Published: July 2006

Ľinterêt pour les polymères de synthèse à utilisation biomédicale ou pharmaceutique va croissant depuis plusieurs annees: en particulier dans les domaines des implants. La biocompatibilité et la biostabililé des polymères biomédicaux dépendent de leurs propriétés physico‐chimiques et struclurales, de leur preparation et de ľenvironnement physiologique. Plusieurs techniques physiques ?analyse pour les phénomènes ?interface sont proposées. Ces méthodes peuvent être employees dans le cas des polysiloxanes et pofyuréthanes.

Synthetic polymers have been used for numerous biomedical and pharmacologic purposes. These indude prosthetic implants, suture material and drug carriers, Long‐term results are often unpredictable despite the continuing exposure to an often hostile physiologic environment. Biocompatibility in general is influenced by physical, chemical and structural properties of these polymers. While surface phenomena are important, reactions related to the bulk itself are not negligible. Methods for analyzing surface and bulk interfaces are described. These tests are directly applicable to studies of polysiloxane (silicone) and polyurethane cardiac pacing leads.
A Review of Implantable Sensors
Authors: KO WEN H.
Published: July 2006

Les capteurs biologiques en cours de developpement offrent: bonne performance, petite taille, cout réduit et compatibilité avec des circuits integrés, Ľétal actuel de ces capteurs en ce qui concerne le milieu biologique est presenlé, Des capleurs physiques peuvent mésurer la pression, les débits, ľaccéleration etc. Des capteurs chimiques peuvent mesurer les ions H+, K+, Na+, etc. La recherche nécessaire pour ľimplantalion chez ľhomme est envisagée.

Solid state sensors offer high performance, small size, lower cost, and compatibility with computing circuits. The current status of these sensors for biomedi‐cal applications is reviewed. Physical transducers may be used to measure pressure, flow, acceleration, velocity, etc. Chemical transducers may measure H+, K+, Na+, etc. Research required for their implantation is suggested.
An Active Optical Sensor for Monitoring Mixed Venous Oxygen‐Saturation for an Implantable Rate‐Regulating Pacing System
Authors: WIRTZFELD A. , HEINZE R. , LIESS H.D. , STANGL K. , ALT E.
Published: July 2006

Les stimuJateurs dits “physiologiques” qui sont actuellement disponibles ne restaurent pos la fréquence optimale dans les cos de défaillance auriculaire. ?autres paramètres biologiques doivent servir de stimulus physiologique pour determiner ľouto‐reglage de la fréquence. La saturation veineuse mesurée par capteur optique serait probablement le paramètre idéal pour ce système de sfimulation. Des recherches supplémentaires sont nécessaires pour bien déterminer les modalités des reponse du système.

Presently available physiologic pacing systems do not fully restore rate regulation, especially in respect to little or no atrial response to activity. Other biologic parameters, detected by sensors, may provide the physiologic responsiveness necessary to rate‐regulating pacemakers. An optical sensor using mixed venous oxygen saturation may be the ideal parameter for such a pacing system. At present, further research is necessary to elaborate a suitable algorithm for optimal rate control.
False Inhibition of an Atrial Demand Pacemaker Caused by an Insulation Defect in a Polyurethane Lead
Authors: VAN GELDER L.M. , GAMAL M.I.H. EL
Published: July 2006

A patient who had an atrial demand pacemaker (AAI) presented with irregular pacing at a routine examination 5 months after implantation. When a magnet was applied over the pulse generator regular fixed rate pacing was obtained, thus proving oversensing in the system. Reprogramming the input sensitivity level to 2.5 and 5.0 m Vdid not solve the problem. Programming the pulse generator to the triggered mode (AAT) showed acceleration of the stimulation rate but also inhibition of the system. An S‐S interval of 1260 ms was measured at a programmed interval of 857 ms (70 bpm). The pulse generator was disconnected and the intra‐atrial electrogram was recorded. This showed different spurious signals varying in morphology and amplitude. Fortunately we were able to remove the lead (Medtronic 6991‐U) from the atrial appendage. Subsequently a Helifix 12 mm AT lead was successfully implanted in the right atrial appendage and the same pulse generator was connected to the newly implanted lead. When the removed lead was examined by the manufacturer, a small tear in the insulation of the wire was defected. The dimensions of the tear were 0.1 × 0.7 mm. The tear was caused by stress corrosion cracking in the polyurefhane tubing of the lead.
The Significance of Surface Changes on Explanted Polyurethane Pacemaker Leads
Authors: TIMMIS GERALD C. , WESTVEER DOUGLAS C. , MARTIN RICHARD , GORDON SEYMOUR
Published: July 2006

Although over 140,000 polyurethane leads have been implanted in humans, a controversy has recently arisen dealing with the significance of frequently detected irregularities on explanled insulator surfaces by scanning electron microscopy (SEM), and their relationship with lead failure. We therefore implanted ten, 6 Fratrial polyurethane leads and an equal number of 4 Fr ventricular leads in dogs for a mean 26 ± 2 and 29 ± 2 weeks, respectively. Fourteen leads were removed utilizing metered force. The remaining leads were removed surgically without force at the termination of the study. Specimens were stored in saline prior to physical testing (tensile strength and elongation) of intravascular and extravascular lead segments. Similarly stored samples were prepared for SEM analysis. The polyurethane insulator disconnected from the electrode on forcible removal in three atrial and two ventricular leads (concordant connected from the electrode on forcible removal in three atrial and two ventricular leads (concordant for two pairs). There was no significant relationship between the results of physical testing and extraction force, lead size, integrity on removal, sample location or SEM scores. Chemical analysis of surface changes employing both x‐ray and electron emission spectroscopy failed to reveal evidence of protein adsorption or liquid impregnation. Samples soaked in sodium hydroxide displayed the same SEM irregularities. The combined effects of fissuring and fluid absorption by polyurethane did not affect chronic anodal or cathodal thresholds, in conclusion, a clear relationship between chronic surface irregularities and the insulator function of polyurethane, its integrity in situ, or its strength atexplanthas not been established by this relatively short‐term study. On the other hand, a potential time‐dependent impact of these changes on lead performance has not been excluded. Moreover, only a single species of medical grade polyurethane has been clinically evaluated. Thus, the ultimate place of polyurethane leads in pacing systems hasyet to be determined.
Thermoplastic Polyurethanes as Insulating Materials for Long‐Life Cardiac Pacing Leads
Authors: PANDE CYAN S.
Published: July 2006

Historically, the material most widely used for permanent cardiac pacing lead insulation has been silicone elastomer. We have recently evaluated a variety of polyether polyurethanes and found them also to be suitable as insulating materials for cardiac pacing leads. Test results showed that these polyurethanes are extremely tough, hydrolytically very stable, non‐toxic, non‐carcinogenic, and very inert in a biological environment. In addition, because poiyurethane has a higher tensile strength than silicone elastomer, a thinner insulating layer can be used to construct smaller diameter leads. This facilitates the introduction of one or two leads through small veins or split sheath introducers. The smooth poiyurethane material is also very easy to advance through the venous circulation, thus improving the handling characteristics of the lead or leards.
Self‐Conversion of Drug Resistant Ventricular Tachycardia by Rapid Atrial Pacing
Authors: WAXMAN MENASHE B. , BONET JORGE F. , WALD ROBERT W.
Published: July 2006

A 52‐year‐old man with recurrent ventricular tachycardia two months post myocardial infarction is described. The tachycardia resulted in low output and heart failure af the lime of presentation. Following elcclrocardioversion of ventricular tachycardia, sinus rhythm would last for only a few seconds, and ventricular tachycardia could not be terminated or prevented by drugs, nor by overdrive pacing. Over a 20‐hour period, asynchronous right ventricular pacing at 30/min resulted in repeated random interruption of successive paroxysms of ventricular tachycardia, resulting in maintenance of sinus rhythm about 60 to 70% of the time. This produced marked hemodynamic improvement and a decrease in the frequency of paroxysms of tachycardia which, however, continued to recur once every few days. Despite theirreduced frequency, these paroxysms continued to be resistant to drugs and had to be terminated by cardioversion. At this point it was discovered that rapid a trial pacing was able to terminate the patient's tachycardia reliably and reproducibly. A permanent right atrial externally activated radio frequency pacemaker device was inserted and over the ensuing eighteen‐month period the patient self‐terminated over fifty discrete episodes of ventricular tachycardia
Late Fractionated Potentials and Continuous Electrical Activity Caused by Electrode Motion
Authors: IDEKER RAYMOND E. , LOFLAND GARY K. , BARDY GUST H. , SMITH WILLIAM M. , WORLEY SETH J. , WALLACE ANDREW G. , COX JAMES L. , GALLAGHER JOHN J.
Published: July 2006

Late fractionated potentials, recorded during cardiac mapping to find the source of a ventricular arrhythmia, have been ascribed particular localizing value. Re‐entry is assumed when these highly amplified and filtered recordings span diastole during tachycardia. The purpose of this study was to see if such potentials can occur artifactually. A saline soaked 7 ± 2 ± 3 cm sponge was sewn to the epicardium of the right ventricle in five non‐infarcted, open‐chest dogs. Two bipolar button electrodes, one with 1 mm and one with 1 cm interelectrode spacing, were attached to the outer surface of the sponge and a bipolar wire hook electrode was placed just under the outer surface of the sponge. Thus all three electrodes were 3 cm from the nearest myocardium yet still subjected to cardiac motion. The electrodes were recorded at gains of 4,000–40,000 and filtered to pass 50–300 hertz. One to three rapid deflections were recorded during the QRS from all electrodes. In seven of the 15 electrode recordings, two or three additional deflections, 100–200 μV in amplitude, occurred after the QRS. These late potentials were fractionated and recurred reproducibly from cycle to cycle. In two cases, these late fractionated potentials could be made to span diastole by rapid pacing to Simula te tachycardia. Clamping the sponge to eliminate motion between the sponge and electrode caused this late activity to disappear. Thus, in highly amplified and filtered recordings, electrode motion can cause artifacts resembling late fractionated potentials and continuous electrical activity.
Increased Risk of Ventricular Fibrillation Associated with Temporary Pacemaker Use During Coronary Arteriography
Authors: LEHMANN MICHAEL H. , CAMERON AIRLIE , KEMP HARVEY G.
Published: July 2006

Each injection of angiographic contrast dye during coronary arteriography represents a “natural experiment” in which the human ventricular fibrillation threshold is transiently reduced. Few factors, however, have been identified which favor the actual occurrence of ventricular fibrillation in this setting. Of 3906 consecutive patients undergoing selective coronary arteriography with sodium meglumine diatrizoate, 66(1.7 percent) experienced dye‐induced ventricular fibrillation, from which all were successfully defibrillated. Analysis of these cases revealed, unexpectedly, that patients in whom temporary right ventricular pacemakers were employed had an incidence of ventricular fibrillation nearly six times that found in the entire group undergoing arteriography (10 percent vs. 1.7 percent, respectively; P<.001). Those individuals receiving pacemakers were distinguished from other studied patients only by a higher prevalence of conduction abnormalities. Although there is normally a low probability that mechanical stimulation by a pacing catheter can induce ventricular fibrillation, it is postulated that such an occurrence may be more likely after ventricular vulnerability has been increased by contrast dye.
Modulation of the Q‐T Interval by the Autonomic Nervous System
Authors: BROWNE KEVIN F. , PRYSTOWSKY ERIC , HEGER JAMES J. , ZIPES DOUGLAS P.
Published: July 2006

Recent investigations have clarified some of the effects of the autonomic nervous system on duration and spatial distribution of the Q‐T interval in humans. The use of atrial pacing to fix heart rate or 24‐hour continuous electrocardiographic recording to develop a regression formula for individual patients has provided a means to interpret the effects of an intervention that alters both the heart rate and the Q‐T interval. Drugs that affect Ihe autonomic nervous system can influence Q‐T interval directly or by changing rate. Bazett's formula to correct for rate may be misleading after certain drug interventions. For example, the Q‐T interval during sinus rhythm or afrial pacing and the ventricular effective refractory period shorten after atropine plus propranolol, but corrected Q‐T interval using Bazetf's formula does not change. No change occurs in the Q‐T interval during sinus rhythm or atrial pacing, or in ventricular effective refractory period after administration of propranolol although corrected Q‐T interval using Bazett's formula markedly shortens. Q‐T interval during sinus rhythm and atrial pacing and ventricular effective refractory period decrease after atropine but correct Q‐T interval lengthens. To define further the relationship of the autonomic nervous system on the duration of the Q‐T interval we studied the effects of sleep. Fifteen patients receiving no drugs underwent 3–6 days of continuous electrocardiography recordings. The duration of the Q‐T interval was longer during sleep in all 15 patients independent of heart rate change. This prolongation of the Q‐T interval during sleep may reflect increased parasympathetic tone or decreased sympathetic tone on the ventricle. Further investigation of the relation of the autonomic nervous system to ventricular depolarization and repolarization may delineate some of Ihe trigger mechanisms for the development of lethal ventricular arrhythmias in humans.
Identical QRS Complexes during Atrial Fibrillation with Aberrant Conduction and Ventricular Tachycardia. The Value of a His Bundle Recording
Authors: BRUGADA PEDRO , WYLICK ALPHONS R V. , ABDOLLAH HOSHIAR , STAPPERS JAN , WELLENS HEIN J.J.
Published: July 2006

In a patient with chronic congestive heart failure, right bundle branch block‐shaped QRS complexes occurred in salvos during atrial fibrillation. The site of origin of these complexes could not be determined from the 12‐lead ECG alone. Recording of a His bundle electrogram showed that both intraventricular aberrant conduction and ventricular tachycardia were responsible for salvos having the same QRS complexes in the 12‐lead ECG.
Implications of Constant‐Energy Pacing
Authors: BERNSTEIN ALAN D. , PARSONNET VICTOR
Published: July 2006

Some cardiac pacemakers main tain constanl energy per stimulus by automatically increasing the stimulus duration as battery depletion causes the stimulus amplitude to decline. This feature does not guarantee an invariant capture safety margin, however, because the stimulus energy at threshold increases for stimulus durations exceeding the geometric mean of the voltage and current chronaxie times. A method is described for identifying the impulse duration at which the initial capture safety margin begins to be lost with constant‐energy pacing.
Retrograde Gap in Fast Pathway Conduction Accentuated by the Class I Antiarrhythmic Agent, Flecainide
Authors: BEXTON RODNEY S. , HELLESTRAND KEVIN J. , NATHAN ANTHONY W. , BANIM SEAMUS O. , CAMM A. JOHN
Published: July 2006

A case is reported of a patient with functional duality of AV nodal conduction in whom, during ventricular extrasfimulus testing, there was a gap in retrograde fast pathway conduction which allowed the temporary expression of retrograde slow pathway conduction. The administration of the antiarrhythmic agent flecainide, which has disparate effects on retrograde fast and slow pathway conduction characteristics, accentuated this phenomenon. The electrophysioJogical basis of gap phenomena is discussed.
The Effect of Power Frequency High Intensity Electric Fields on Implanted Cardiac Pacemakers
Authors: BUTROUS GHAZWAN S. , MALE JOHN C. , WEBBER ROBERT S. , BARTON DAVID G. , MELDRUM STUART J. , BONNELL JOHN A. , CAMM A. JOHN
Published: July 2006

Thirty‐five patients fitted with 16 different pacemaker models (from 6 manufacturers) were exposed to 50 Hz electric fields up to a maximum of 20 kV/m. Four different response patterns were encountered: (1) normal sensing and pacing in all Medtronic and some Vitatron units; (2) reversion to the fixed (interference) rale in ail Telectronics. all Pacesetter, some Vitatron and CPI units; (3) slowand irregtilarpacing in one CPI and in all Cordis units; (4) mixed behaviorovera critical range of field strengths in which slow and irregular pacing preceded reversion to fixed‐rate, in some Telectromics and Pacesetter units. The field strengths required to induce such behavior varied from unit to unit and from model to model, with Telectronics being the most sensitive. In general, the interference threshold depended on the magnitude and distribution of induced body current relative to the pacemaker as well as field strength and thus varied with patient height, build and posture. While only a small proportion of pacemaker patients are likely lo encounter electric fields strong enough to interim.1 with pacemaker behavior, this possible hazard should be recognized.
Rate Responsive Pacing Using the Evoked QT Principle. A Physiological Alternative to Atrial Synchronous Pacemakers
Authors: DONALDSON R.M. , RICKARDS A.F.
Published: July 2006

We have evaluated clinically a rate‐responsive pacemaker which uses the evoked QT principle as indicator of physiological demand. This pacemaker is microprocessor‐based and fully programmable noninvasively through radiofrequency coupling to an external microcomputer. To date this system has been implanted in 15 patients. With this QTsensing pacemaker the ra te response to exercise was smooth and progressive, and gradually returned to the basic paced rate after termination of activity. Physiologic rate responsive pacing resulted in significant improvement in exercise tolerance and a 40% increase in cardiac output when compared to fixedrate pacing in 8 patients. This initial experience confirms the possibility of obtaining a physiological response to exercise using a pacing system dependent only on a unipolar electrode which is independent of the problems of atrial activity and sensing. Rate responsive pacing might prove to be a useful alternative to atrial synchronous systems, and particularly advantageous in those patients whose sinoatrial function is abnormal or who suffer from atrial arrhythmias.
Usefulness of Doppler Echocardiography in Cardiac Pacing: Assessment of Mitral Regurgitation, Peak Aortic Flow Velocity and Atrial Capture
Authors: ZUGIBE FREDERICK T. , NANDA NAVIN C. , BAROLD S. SERGE , AKIYAMA TOSHIO
Published: July 2006

Doppler echocardiographic studies were performed in 14 patients with dual chamber pacemakers. Transmitral flow studies (12 patients) revealed absence of mitral regurgitation (MR) or no change in MR severity in 6, new development or increased MR during VVI and/or short or long A V interval lengths compared to more normal AVintervals(150–160 ms) in 5, and appearance of MR when the pacing mode was changed from VVI to DVI with a fixed AV interval of 250 ms in 1 patient. Aortic peak flow velocity measurements (7 patients) showed significant increases in stroke volume(range9 to 25%. mean 19.5%) in all patients with DVI/VDD pacing compared to VVI pacing (4 patients) or to shortest available AV interval (3 patients). Presence of Doppler left atrial systolic flow correlated with evidence of atrial depolarization in all 7 patients in whom high quality 12‐lead surface electrocardiograms were obtained. Our preliminary study demonstrates the value of Doppler echocardiography in the “fine tuning” of cardiac pacemaker parameters by assessment of presence, absence, or change in severity of MR, estimation of relative changes in stroke volume, and determination of atrial capture in different pacing modes and at various AV intervals.
Clinical Experience with a Bradycardia Indicating Pacemaker
Authors: ROSENQVIST MÅRTEN , EDHAG K. OLOF , VALLIN HANS O.
Published: July 2006

The beneficial effect of permanenl pacing is controversial in certain patient groups. Once pacing has been instituted it isseldom terminated and an evaluation of pacemaker depen‘dence is therefore not possible. An implantable puise generator, detecting bradycardia beiow 30 bpm has beendeveiopedin order tobroaden ourknowledgeabout the natural history of bradyarrhythmias treated by permanent pacing. This pacemaker has been implanted in 30 patients who did not have clear‐cut indications for permanent pacing. They have been followed for a mean of 13 months. Bradycardia was detected in 33 patients 1 to 21 months (4.6 mean) affer implantation. Twenty‐one patients did not have a defected bradycardia for Jong periods (months‐years). Minor symptoms of lightheadedness a dributable to bradycardia were reported by 15 patients during periods when the pacemaker had been activated. Holter monitoring for at least 24 hours was carried out in all patienls and electronic analysis of explanted generalors was performed in eieven cases. No tecnnical failure relaled to the bradycardia‐detecting facility was observed. The combination of diagnostic and therapeutic properties in the bradycardia‐indicating pacemaker provides means for safe evaluation of pacemaker dependency over long time periods in patienl groups with controversial indications for permanent pacing.
Multivariate Analysis of Pacemaker Patient Survivorship
Authors: HSU PING‐HWA (BEN) , KIM JOHN S.
Published: July 2006

Multiple risk factors of patient mortality need to be evaluated and combined to serve practical purposes. A mul‐tivariate statistical model is illustrated here with a large data set and a simulated example. The piecewise parametric model is shown to be simple, efficient, and is suggested to be a good tool for routine usage. The approach should provide a more concise characterization of mortality in terms of multiple risk factors. The results of data analysis also provide a good reference for further explorations.
Idiopathic Recurrent Parasystolic Ventricular Tachycardia in a Child
Authors: LIGHTFOOT PAUL R. , BHATT DILIP R.
Published: July 2006

An asymptomatic 31/2‐year‐old boy demonstrated parasystolic ventricular tachycardia with AV dis‐sociation, early sinus capture beats, marked variability in coupling intervals between conducted and ectopic beats, fusion beats, and interectopic intervals which were multiples of the ectopic cycle length. The arrhythmia initially responded to quinidine, reappeared over an 11‐month observation period, and finally was suppressed at a high quinidine dose. An invasive and noninvasive work‐up failed to demonstrate organic heart disease.
Amiodarone in the Management of Patients with Ventricular Tachycardia and Ventricular Fibrillation
Authors: MORADY FRED , SCHEINMAN MELVIN M. , HESS DAVID S.
Published: July 2006

Fifty‐eight patients with symptomatic ventricular tachycardia (VT) or ventricular fibrillation (VF) were treated with amiodarone. All had clinical episodes of VT/VF or inducible VT during electropharmacologic testing despite treatment with maximumtolerated doses of conventional antiarrhythmic agents. Chronic treatment with amiodarone was begun at a dose of 800–1000 mg per day. Thirty‐two patients were also treated with a previously ineffective conventional agent. Thirty patients underwent programmed ventricular stimulation after 2.6 ± 1.7 months (mean ± S. D.) of treatment with amiodarone at a mean daily dose of 588 ± 155 mg. VT was induced in 25 patients (sustained in 20, nonsustained in five). Seventeen patients had a recurrence of VT or VF after 0.5–9 months of treatment with amiodarone (fatal in seven, non‐fatal in 10). Forty‐one patients (71%) had no recurrence of symptomatic VT or VF while being treated with amiodarone (mean follow‐up period, 17.1 ± 12.4 months). Among the 25 patients who had inducible VT with programmed ventricular stimulation while being treated with amiodarone, 19 patients (76%) have had no recurrence of symptomatic VT or VF overa follow‐up period of 21.5 ± 7.3 months. Ambulatory electrocardiographic recordings obtained after one week of treatment with amiodarone were not helpful in predicting clinical response. Twenty‐two patients (38%) developed ataxia and/or an intention tremor which improved with a decrease in the amiodarone dose. Amiodarone, either by itself or in combination with conventional antiarrhythmic drugs, has a significant therapeutic effect in high risk patients with refractory VT. The finding of inducible VT during electropharmacologic testing in patients taking amiodarone does not preclude a favorable clinical response. Neurologic toxicity is common in patients treated with 600–800 mg per day of amiodarone.
AV Pacing and LV Performance
Authors: COSKEY RICHARD L. , FEIT THEODORE S. , PLAIA RITA , ZICARI TONY
Published: July 2006

Five patients with impaired left ventricular function (LV) and implanted AV sequential pacemakers underwent serial radionuclide angiograms. The goal was a non‐invasive evaluation of the rapid changes in left ventricular performance elicited by rate, pacing mode and AV interval manipulation. End diastolic volume, end systolic volume, stroke volume and cardiac output were increased by AV sequential pacing in comparison with ventricular pacing at 70 beats per minute. No significant change in ejection fraction and blood pressure were noted with changing AV sequential pacing rates at usual pacing rates. Our data suggest that a short A V interval (150 ms) improved LV performance more than a long AV interval (250 ms). A non‐invasive technique to optimize left ventricular performance on an acute basis by varying heart rate, AV interval and pacing mode with the implanted AV sequential pacemaker is feasible and may be useful in selective clinical situations.