bluuebunny/crossref_metadata_2025_split huggingface dataset:
Suppression of Demand Mechanism by Inactive Myocardial Electrodes
Authors: YOKOYAMA MASAYOSHI , HORI MOTOKAZU , GRECHKO MICHAEL 
Published: July 2006

A 14 year old girl, at age 8, had had a bipolar pulse generator implanted with myo‐cardial leads. Because one of the myocardial leads fractured near the electrode, a second pair of myocardial leads were implanted. Thus, the patient had two pairs of myocardial leads and one demand pulse generator implanted.When the patient was readmitted to the hospital because of light‐headedness, the ECG monitor revealed frequent suppression of pulse generator pulses when hand pressure was exerted over the pulse generator site. Converting the pulse generator into the asynchronous mode with a magnet prevented inhibition. The pacemaker pocket was reopened. The pulse generator could not be inhibited either by pulling on the active myocardial leads or by moving the pulse generator, but the pulse generator could be inhibited by manipulation of the inactive leads which produced electrical signals having amplitudes and frequencies which were in the bandwidth of the sensing circuit. The probable cause of the electrical signals was the irregular conta of the terminals of the inactive leads with the patient's abdominal muscles. Replacement of the demand pulse generator by an asynchronous type resulted in cessation of the patient's light‐headedness.
The Porous Endocardial Electrode
Authors: AMUNDSON DAVID C. , MCARTHUR WILLIAM , MOSHARRAFA MOSTAFA 
Published: July 2006

AMUNDSON, D.C., McARTHUR, W., AND MOSHARRAFA, M.: The porous endocardial electrode. The permanent endocardial electrode has exhibited the problems of dislodgement, excessive threshold rises and Joss of sensing. These failure modes are addressed with a new electrode incorporating a porous body of Pt‐Ir fibers with a fiber diameter of 20 μm and an overall density of 10%. Porous electrodes have the advantages of utilizing the electrode interior both for tissue ingrowth to improve anchoring and for electrolyte penetration which improves fl wave amplitude and reduces polarization losses. A series of 20 porous electrodes was compared with 17 solid electrodes of similar dimension. Electrodes were implanted in dogs in the apex of the right ventricle, and were subsequently followed up to 210 days. Comparison of the electrode data revealed that the porous electrodes had a 40% reduction in chronic voltage thresholds and had an overall dislodgement rote of 10%, compared to 53% for (he solid electrodes. Histological examination revealed tissue ingrowths throughout the electrode interior and a fibrotic capsule about half (he thickness of the solid electrodes. R wave stability was enhanced with the porous electrode due to improved anchoring, reduction in slew rate changes and less R wave attenuation. Assuming results are translatable to humans, the porous elctrode will provide a greater pacing safety margin when used with a standard demand pacemaker, or improved longevity with the same safety margin as solid electrodes if used with a programmable pacemaker. The incidence of dislodgement and sensing failure will also be diminished with the porous electrode. (PACE, Volume 2, January‐February, 1.979)
The Interdependence Between Electrogram, Total Electrode Impedance and Pacemaker Input Impedance Necessary to Obtain Adequate Functioning of Demand Pacemakers
Authors: OHM OLE‐JÖRGEN 
Published: July 2006

Electrogram maximum derivatives (DMAX, SMAX) and electro‐gram amplitudes (AMAX, UMAX) (Figure 2), were studied in 71 cases during permanent pacemaker treatment. During the acute phase, (at first implantation), 29 patients were studied, and during the chronic phase, (at pulse generator replacement), 42 patients were studied. Of these patients, 27 (acute phase) and 36 (chronic phase) were studied for tissue impedance (Ry) and interface impedance (Faraday resistance Rp and Helmholtz capacitych)‐ DMAX and SMAX changed from 3.47 ± 0.33 V/s (mean ± SEM) to 2.48 ± 0.23 V/s and 1.93 ± 0.20 V/s to 1.32 ±0.12 V/s; p < 0.02; p < 0.01. AMAX and UMAX remained nearly unchanged from acute to chronic phase. A paired comparison in 13 patients showed almost identical results.Electrograms recorded in patients with bundle branch block showed no statistical difference in DMAX, SMAX, AMAX, and UMAX compared with electrograms recorded in patients with QRS‐complexes of normal duration.No correlation was found between rise in myocardial threshold and fall in DMAX and SMAX from acute to chronic phase; p > O.8, p > 0.5.Patients with coronary heart disease were found to have significantly higher AMAX than patients classified as having rhythm disturbances of primary cause; p < 0.01. Extremely low values of amplitudes and maximum derivatives were found in some patients with myocardial infarctions and cardiomyopathies. No difference existed in DMAX, SMAX, AMAX, and UMAX recorded from electrodes with a 8 mm2area compared with a 12 mm2area (p > 0.5).rtwas statistically significantly higher on the smaller compared with the larger surface electrodes (p < 0.005). There was a slight but not statistically significant fall inrtfrom acute to chronic phase (p > 0.2). Rp ranged from 2.0–94.6 Kohms. There was no statistically significant differences between the 8 mm2compared with the 12 mm2electrodes (p > 0.2).chvaried between 0.7 and 37.0 microfarads, with significantly lower values for the smallest electrodes (p < 0.05), In patients with electro‐grams of borderline amplitudes and maximum derivatives for being sensed, the lowchfound with the small tip electrodes, will give a higher risk of demand failure if the input impedance in the sensing circuit of a demand pacemaker is too low.
The Chronaxie Time and Its Practical Importance
Authors: IRNICH W. 
Published: July 2006

Describing mathematically, the intensity duration curves of electrostimulation by hyperbolas, Lapicque introduced two terms which characterized the functional relationship: “Rheobose” was the lowest intensify with indefinite pulse duration which just stimulated muscles or nerves. “Chronaxie” was that pulse duration at which the threshold intensity was twice that of the rheobase. Up to now, both terms have never played an important role in cardiac pacing.However, it can be shown that the chronaxie, especially, is an important parameter—influenced by several factors such as electrode size, material, and stimulation mode—which may help match the generator to its electrode. Practical consequences may be derived from the concept of chronaxie:

A pulse duration longer than the chronaxie is not desirable because current consumption is increased without decreasing the threshold significantly.
Pacing with constant current needs twice that pulse duration of constant voltage stimulation.
Smaller electrodes are more favorable because the pulse duration they need may be reduced without losing safety.
Estimation of the safety margin with decreasing output of the generator or with programmable pulse duration is possible if the chronaxie of a specific electrode is known.
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.
Responses of an AV Universal (DDD) Pulse Generator (Cordis 233D) to Programmed Single Ventricular Extrastimuli
Authors: van MECHELEN ROB , HAGEMEIJER FRANS , de JONG JAN , de BOER HANS 
Published: July 2006

To evaluate factors playing a role in initiation and perpetuation of pacemaker‐mediated tachycardias (PMTs), 22 consecutive patients with symptomatic conduction disorders were studied after implantation of an AV universal (DDD) pulse generator (Cordis 233D). Patients were divided into two groups, depending upon the presence or absence of ventriculoatrial (VA) conduction during electrophysiological study (EPS) performed before pacemaker implantation. PMTs couid be initiated in six of eight patients of Group I and in none of 14 patients of Group II. Initiation and perpetuation of PMTs during DDD pacing were dependent upon the capacity of the patient to conduct ventricular premature beats (VPBS) and subsequent paced ventricular beats retrogradely to the atria, and upon three programmable parameters of the pulse generator (AV delay period, upper rate limit, tachycardia response).Programmed single ventricular extrastimulation demonstrated that: (1) merely the presence of VA conduction during EPS, although necessary, was not sufficient to induce PMTs after DDD pacemaker implantation; (2) VPBs introduced late rather than early in the cardiac cycle initiated PMTs in a different way; (3) the initiation of PMTs could be prevented during study by adjusting the programmable parameters (AV delay period, upper rate limit, tachycardia response); (4) one of the two available tachycardia responses of the pulse generator (gradual fall‐back response) was able to terminate and initiate PMTs consistently.These observations helped in understanding the responses of the Cordis 233D pulse generator to ventricular premature beats. They indicate that additional refinement of the pulse generator is necessary to solve the problem of PMT.
Rate Hysteresis Pacing: How Valuable Is It? A Comparison of the Stimulation Rates of 70 and 50 Beats per Minute and Rate Hysteresis in Patients with Sinus Node Disease
Authors: ROSENQVIST M. , VALLIN H.O. , EDHAG K.O. 
Published: July 2006

The main disadvantages of VVI pacing are absence of acceleration of the heart rate and loss of atrial synchronization. The alternatives to AAI and DDD pacing are stimulation at a low rate or hysteresis in order to decrease pacing time and thus reduce AV asynchrony. Nine patients who suffered from sinus node disease and who had been given a multiprogrammable pacemaker were monitored at each of three stimulation rates: 70, 50, and 70 bpm with an inhibition rate of 50 bpm (hysteresis).The total pacing time was shortest (p < 0.05) for the stimulation rate of 50 bpm as compared to 70 bpm and hysteresis. It was also shorter for the hysteresis mode than for the 70 bpm mode (p < 0.05).Only for hysteresis pacing was there a significant reduction in the number of changes from conducted cardiac rhythm to pacemaker‐induced rhythm. Most patients found the 50 bpm mode preferable. None favored the hysteresis mode.In patients with sinus node disease and intermittent bradycardia being permanently paced, the periods of AV‐conducted rhythm may be lengthened by reducing the stimulation rate from 70 bpm, with or without hysteresis pacing, to 50 bpm. In paced patients with sinus node disease and symptoms due to AV asynchrony, it might be worth trying a decrease in the stimulation rate before resorting to other pacemaker systems.
Clinical Experience with Implantable Devices for Control of Tachyarrhythmias
Authors: DULK KAREL den , BERTHOLET MICHEL , BRUGADA PEDRO , BÄR FRITS W. , DEMOULIN JEAN C. , WALEFFE ANDRE , BAKELS NOUD , LINDEMANS FRED , BOURGEOIS IVAN , KULBERTUS HENRI E. , WELLENS HEIN J.J. 
Published: July 2006

Pacing is becoming an accepted form of treatment for reentry tachycardias. The different pacing modalities available and experience with a patient‐activated antitachycardia pacemaker are presented in this paper. This system has bidirectional communication between pacemaker and pacemaker‐activator and between pacemaker and prescription formulator (which is a sophisticated portable stimulator used for non‐invasive electrophysiological evaluation of the system). This pacemaker was implanted in 18 patients with drug‐resistant tachycardias. Six patients had ventricular tachycardia, 3 had A‐V nodal reentrant tachycardia, 4 had the concealed accessory pathway, and 5 had the WPW syndrome. In the 3 months before implantation the mean number of admissions for termination of tachycardia was 2.1 per patient‐month. During a follow‐up period of 3–26 months only 6 patients were admitted once for termination of tachycardia (0.02 admissions per patient‐month). The reasons for admission of these 6 patients were: defective pacemaker activator in 2 patients, inadequate control of tachycardia in 2 patients, inappropriate use of the device in 1, and inadequate intake of medication in 1. All these problems were solved easily. Eight pacemaker activators required reprogramming, which was done in 5 patients on an out‐patient basis. The interval scanning mode was used in 9 patients. Nine patients required more than 2 stimuli for reproducible termination. A step‐wise increase in number of stimuli was used in 5 patients.This system has proven to be a safe and effective form of treatment of drug‐resistant supraventricular and ventricular tachycardias and has resulted in marked improvement of the quality of life of these patients.
One Turn More: Threshold Superiority of 3‐turn versus 2‐turn Screw‐in Myocardial Electrodes
Authors: KORHONEN ULLA , KÄRKÖLÄ PENTTI , TAKKUNEN JUHA , POKELA RISTO 
Published: July 2006

Epicardial electrodes are an alternative for patients in whom the transvenous approach presents technical difficulties. We have had clinical experience with two types of myocardial sutureless electrodes inserted in the anterior left ventricular wall: the 3‐turn screw‐in electrode (Medtronic 6917) was used in 209 patients from 1974 to 1977 and the 2‐turn screw‐in lead (Medtronic 6917 A) was used in 61 patients from 1978 to 1981. The initial threshold was equal and acceptable with both types of electrodes.During a follow‐up period (up to 48 months), critical elevation of the pacing threshold resulting in exit block was found in 12% (25) of the patients with the 3‐turn screw‐in electrode and in 20% (12) of the patients with the 2‐turn electrode (p < 0.05). Elevation of the pacing threshold developed fairly early, usually within 6 months, with the 2‐turn screw‐in electrode, but much later, within 2–4 years, with the 3‐turn electrode. During a longer follow‐up time of up to 96 months the frequency of exit block increased up to 16% with the 3‐turn electrode.Our results indicate that late critical elevation of the pacing threshold is surprisingly frequent with screw‐in electrodes inserted into the left ventricular myocardium, and it is especially common with the 2‐turn screw‐in electrode.
The Effects of Nuclear Magnetic Resonance Imagers on External and Implantable Pulse Generators
Authors: FETTER JOSEPH , ARAM GEORGE , HOLMES DAVID R. , GRAY JOEL E. , HAYES DAVID L. 
Published: July 2006

This study evaluates the effect of nuclear magnetic resonance (NMR) scanning on pacemaker function. it must be emphasized that each manufacturer's pulse generators and each pacing modality may behave differently and, therefore, require individual evaluation. According to our results, patients with pacemakers should have their pacing activity monitored continuously during scanning with the NMR 1500 gauss imaging system. External pulse generators should he net to the asynchronous mode and placed outside the NMR image volume but within the radiofrequency [RF] shield. Implanted pacemakers should be verified for type and mode of operation. Ail implantable pulse generators evaluated reverted from the demand to the asynchronous mode within the magnetic field of the scanner. There was no observable damage to the discrete pacemaker components that were tested.In vivo testing of implantable single‐chamber pulse generators did not significantly alter the pacemaker's operating parameters. Changes in stimulation rate analogous to the RF field pulse rate were seen. In single‐chamber devices the resultant rate was a multiple of the RF frequency, changing to a value less than the normal asynchronous magnetic rate. With morn sophisticated dual‐chamber devices the results varied. With VDD pacing during RF scanning, the cardiac stimulation rote increased to a value analogous to the value of the RF field modulation period.More extensive in vivo testing using different models of pulse generators of various manufacturers is needed to identify specific device susceptibility to the RF, time variance and steady‐state magnet fields. From these data a comprehensive statement about NMR scanning of patients with implanted pacemakers can be made.