The usefulness of sensor data storage for rate response simulation was evaluated using a new dual chamber rate modulated pacemaker sensitive to acceleration forces (Relay 294-03 [Intermedics Inc.]). The pacemaker can ...
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The usefulness of sensor data storage for rate response simulation was evaluated using a new dual chamber rate modulated pacemaker sensitive to acceleration forces (Relay 294-03 [Intermedics Inc.]). The pacemaker can store the sensor output during routine exercise and those values can be used to simulate rate profiles for other rate response settings. The predictive value of this feature was evaluated in three studies (mechanical, external pacemaker, and implanted pacemaker). In the first study, the pacemaker was submitted to three runs of eight different mechanical calibrated to-and-fro movements. In the second study, nine external pacemakers were strapped on healthy volunteers who performed three jogging tests. Finally, the predictive value of the simulation was studied in five implanted patients during three successive walking tests. In each study, the pacemaker was submitted three times to the same activity. The responsiveness was successively set to 5, 1, and 10, and the pacemaker outputs were continuously recorded on a Holter monitor. At the end of the first run, rate profile simulations for slopes 1 and 10 were performed;slope 5 rate response was simulated after the second run. A regression analysis was used to establish the correlation between predicted and achieved pacing rates for each study. The coefficients of correlation between predicted and measured pacing rates for the mechanical, external, and clinical studies were 0.999, 0.985, and 0.823, respectively. The corresponding slopes of regression lines were 1.005, 0.971, and 0.935. Calculated rate profile has a high predictive value and could be used to optimize rate responsive settings without serial exercise testings.
It is essential that patients with pacemakers capable of rate modulation undergo some form of exercise testing to assure appropriate rate modulation. Informal exercise testing is a reasonable and less expensive altern...
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It is essential that patients with pacemakers capable of rate modulation undergo some form of exercise testing to assure appropriate rate modulation. Informal exercise testing is a reasonable and less expensive alternative to formal treadmill testing. Empiric adjustment of the rate response parameters by assessing the patient's rate response while walking at a self-determined casual and brisk pace has been used. However, no normals exist to determine the appropriate rate response for a "casual" and "brisk" walk. Volunteers were tested with metronome-guided casual and brisk walks in an effort to standardize the informal exercise and determine expected heart rate response for these levels of activity. Results of the metronome-guided rate response in normal volunteers may be useful in determining the appropriate rate response for pacemaker patients when tested in such an informal manner.
The pacing threshold of the human heart may be altered by physiological factors such as physical exercise. These changes may influence the individual programming of a pacemaker, since pacemakers can be programmed at p...
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The pacing threshold of the human heart may be altered by physiological factors such as physical exercise. These changes may influence the individual programming of a pacemaker, since pacemakers can be programmed at pulse amplitudes of 2.5 volts and less. We investigated 22 patients with a multiprogrammable ventricular demand pacemaker 3 months after implantation;16 patients had received a steroid-eluting lead and six patients had an Elgiloy lead. Parameters measured at rest and immediately after exercise were: Voltage threshold at pulse durations between 0.05 and 0.6 ms, impedance, R wave amplitude and energy consumption for the pacing threshold at 0.5 ms pulse duration. All patients performed a symptom limited supine bicycle exercise test. None of investigated parameters showed a significant difference between rest and exercise, neither for the steroid eluting lead nor for the Elgiloy lead. The data suggest that the individual programming of a pacemaker adapted to the measurements at rest is also reliable and safe during exercise.
A mathematical model of the cardiac conduction system, including external pacemakers, has been developed. The heart is modeled as a network in which the impulse propagation is described by differential equations; seve...
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A mathematical model of the cardiac conduction system, including external pacemakers, has been developed. The heart is modeled as a network in which the impulse propagation is described by differential equations; several arrhythmia-generating mechanisms, such as modulated parasystole, reflection, macro and micro re-entry and block, can be simulated. Different kinds of pacemaker modes have been incorporated in the model, thus making it possible to simulate the interaction between the heart and the pacemaker. The model can be tuned by the user according to electrophysiological data so that pacemaker programs can be tested under different underlying conditions. During a simulation, the program generates ECG signals and pacemaker diagnostic diagrams. This model can be used for training and testing, and also as a support system when searching for the optimal pacing therapy for a particular patient.
The DDI mode is a new pacing mode with potential advantages over DVI pacing. We describe anomalous post R wave ventricular pacing due to the presence of inappropriate ventricular blanking periods in a pacemaker progra...
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The DDI mode is a new pacing mode with potential advantages over DVI pacing. We describe anomalous post R wave ventricular pacing due to the presence of inappropriate ventricular blanking periods in a pacemaker programmed to the DDI mode. Although no adverse consequences were seen in our patients, potentially dangerous R-on-T pacing could occur, particularly if long atrioventricular delays are programmed. A method for eliminating this pacing anomaly is described. Patients programmed to the DDI mode with the pacemaker model described should be evaluated for post R wave ventricular pacing and corrective measures should be taken.
While being evaluated for a recurrent tachyarrhythmia, a patient with a permanent pacemaker underwent reprogramming of the unit from the DVI to the VVI mode for assessment of the underlying rhythm. Subsequent reprogra...
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While being evaluated for a recurrent tachyarrhythmia, a patient with a permanent pacemaker underwent reprogramming of the unit from the DVI to the VVI mode for assessment of the underlying rhythm. Subsequent reprogramming of the pacemaker to the DVI or DDD mode was impossible despite multiple attempts and the use of multiple programmers. The problem was considered to be a malfunction of the pacemaker circuitry, and plans were made for the pacemaker to be explanted and a replacement unit implanted. Before the procedure, the pacemaker company was notified of the explantation. We subsequently learned that a special programming sequence had to be carried out because of reversion circuitry present in the pacemaker but not described in the available literature. This report emphasizes the need for familiarity with each of the individual pacemakers being implanted and the need for the manufacturer to be as specific as possible given the complexity of current units.
La surveillance des pacemakers DDD est devenue de plus en plus difficile à cause de la complexitSeA croissante des générateurs d'impulsion. Un “test type” devrait être développé pou...
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La surveillance des pacemakers DDD est devenue de plus en plus difficile à cause de la complexitSeA croissante des générateurs d'impulsion. Un “test type” devrait être développé pour permettre une analyse systematique et l'enrégistrement des données. Pour suivre efficacement un patient porteur d'un pacemaker DDD il est nécessaire de connaître son rythme sousjacent celeri du générateur d'impulsion, la souplesse de sa programmation et ses autres
Les différentes possibilités pour programmer les stimulateurs sont présentées. Un stimulateur à base “hardware” fournit une stimulation bien fiable mais avec des limites étroites. De l\...
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Les différentes possibilités pour programmer les stimulateurs sont présentées. Un stimulateur à base “hardware” fournit une stimulation bien fiable mais avec des limites étroites. De l\'autre côté, un stimulateur logiciel (à“software”) aurait une flexibilité maximale en ceoui concerne les programmes, mais restera plus susceptible d\'erreurs de software. La solution mediane diviserait le programme entre mémoire ROM passive et mémoire RAM active. Cette alternative pourrait fournir une réponse sophistiquée sans sacrifier l
Nous avons récemment développé des stimulateurs à base de microprocesseur avec flexibilityé reélle du software. Les 25 premiers appareils implantés (type DPG-1) ont démontré...
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Nous avons récemment développé des stimulateurs à base de microprocesseur avec flexibilityé reélle du software. Les 25 premiers appareils implantés (type DPG-1) ont démontré un phénomène inattendu suite à une erreur du microprocesseur. Un système de securityé a annullé toutes les fonctions spéciales et a remis tous les parametres aux paramètres “standards.” Le problème a été résolu par la modification noninvasive du software. Plus de 200 stimulateurs (type TX-1) qui fournissent un rythme asservi aux variations de l'espace QT, ont été impiantés jusqu'en mai 84. Ces stimulateurs étaient construits avec les mêmes circuits microéléctroniques que ceux du type DPG 1. Les connaissances obtenues au cours des essais cliniques étaient directement appliquées non seulement aux nouveaux implants mais aussi aux anciens implants. Ceci a étééffectué par la reprogrammation du software dans Jes slimulateurs implantés. Recently, we have developed microcomputer-oriented pacemakers with true software flexibility. The first 25 devices implanted (DPG-1 type * * Vitatron, Dieren, The Netherlands ) exhibited an unexpected phenomenon caused by a microcomputer error. A safety mechanism switched off all special functions and automatically reset all parameters to standard settings. The problem was solved by noninvasive modification of the software. More than 200 units (TX-1 type * * Vitatron, Dieren, The Netherlands ), which are rate responsive pacemakers based on the QT principal, were implanted up to May 1984. These pacemakers were built using the same microelectronics as used in the DPG 1 pacemaker. Knowledge gained from clinical evaluation was directly applied not only to the patients receiving new implants but also to the preexisting implantees. This was done by software reprogramming in the implanted unit.
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