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Pacemaker System (pacemaker + system)
Selected AbstractsProspects for Biological Cardiac Pacemaker SystemsPACING AND CLINICAL ELECTROPHYSIOLOGY, Issue 11 2003ARJANG RUHPARWAR No abstract is available for this article. [source] Development of PDF-immunoreactive cells, possible clock neurons, in the housefly Musca domesticaMICROSCOPY RESEARCH AND TECHNIQUE, Issue 2 2003Elzbieta Pyza Abstract Even though the housefly Musca domestica shows clear circadian rhythms in its behavioural and physiological processes, a circadian pacemaker system controlling these rhythms has not yet been described morphologically in this species. In M. domestica, neurons immunoreactive to pigment-dispersing factor (PDF), a neurotransmitter/neuromodulator of circadian information arising from a circadian clock and transmitted to target cells, are similar in their number and distribution to the PDF neurons of Drosophila melanogaster. In D. melanogaster these neurons co-localize PER protein and have been identified as clock neurons in that species. Here we report PDF-immunoreactive cells in the housefly's brain during postembryonic development in the larval and pupal stages, as well as in the adult fly soon after eclosion. In the housefly's brain, there are three groups of PDF-immunoreactive neurons: two groups with small (sPDFMe) and large (lPDFMe) cell bodies in the proximal medulla of the optic lobe; and one group in the dorsal protocerebrum (PDFD). Three out of four sPDFMe can be detected during the first hour of larval development, but the fourth sPDFMe is observed in the larva only from 48 hours after hatching, along with five lPDFMe neurons, seen first as two subgroups, and three out of four PDFD neurons. During postembryonic development these neurons show changes in their structure and immunoreactivity. New PDF neurons are observed during pupal development but these neurons mostly do not survive into adulthood. In the adult fly's brain, the PDF neurons have also been examined in double-labelled preparations made with a second antibody directed against the product of one of several clock genes: period (per), timeless (tim), or cryptochrome (cry). Among them, only immunoreactivity to CRY-like protein has been detected in the brain of M. domestica and has shown a daily rhythm in its concentration, as examined immunocytochemically. CRY was co-localized with PDF in the sPDFMe of the housefly's brain fixed during the day. The possibility that the sPDFMe neurons are the housefly's clock neurons is discussed. Microsc. Res. Tech. 62:103,113, 2003. © 2003 Wiley-Liss, Inc. [source] Does Bipolar Pacemaker Current Activate Blood Platelets?PACING AND CLINICAL ELECTROPHYSIOLOGY, Issue 5 2009GRUNDE GJESDAL M.D. Objective: The aim of this study was to investigate whether bipolar pacemaker current lead can activate blood platelets. The null hypothesis was that 1 minute of electrical stimulation of platelets would not influence their subsequent reactivity to adenosine diphosphate (ADP). Background: Both platelets and muscle cells contain actin and myosin filaments, and both cells are activated following calcium influx. Muscle cells open their calcium channels and contract when exposed to an electric current. Current through a bipolar pacemaker lead will expose a small volume of blood, including platelets, to the depolarizing current. Platelet activation may ensue, resulting in aggregation, release reaction, and contraction. In contrast, a unipolar pacemaker system will not depolarize blood, but transmit current directly into the myocardium, and the current afterward passes through other tissues before returning to the pacemaker can. Methods: Platelet-rich plasma was prepared from two healthy subjects. Platelet reactivity to the agonist ADP was tested in paired samples in an aggregometer in a case/control setup. Results: Eighteen of 46 tested pairs of platelet-rich plasma showed increased reactivity in the paced sample; 26 were unchanged while two showed decreased reactivity in the paced sample. Using a two-sided sign test, the null hypothesis was rejected (P = 0.0004). Conclusions: The study demonstrates increased reactivity to ADP in platelets exposed in vitro to stimulation by pacemaker current. The clinical relevance of these findings remains to be investigated. [source] DDD Pacemaker Implantation After Fontan-Type OperationsPACING AND CLINICAL ELECTROPHYSIOLOGY, Issue 1p2 2003MARKUS K. HEINEMANN HEINEMANN, M.K., et al.: DDD Pacemaker Implantation After Fontan-Type Operations.Bradyarrhythmias developing after Fontan-type operations impair the function of the univentricular heart causing fatigue, headaches, ascites, and protein-losing enteropathy (PLE). Transvenous inaccessibility, requiring epicardial implantation, accounts for the reluctance to implant a pacemaker (PM). Between 1997 and 2000, 24 patients (mean age 9.5 years, range 6 months to 19 years) with Fontan-type operations received DDD pacing systems with atrial steroid-eluting stitch-on electrodes (mean capture threshold 1.9 V/0.5 ms, range 0.4,3.5 V) and ventricular screw-in electrodes (mean capture threshold 1.7 V/0.5 ms, range 0.1,3 V). The systems were implanted at the time of conversion from atrio- to cavopulmonary connections in 5 patients, at the time of a total cavopulmonary Fontan operation in 6, and 1,50 months thereafter (mean = 18) in 13 patients. A right ventricular anatomy was present in 13 (54%) of 24 of PM recipients, versus 35% of the overall population. After a mean follow-up of 3.5 years, the PM were functioning in DDD mode in 23 of the 24 patients. Length of hospital stay in the ten patients who underwent repeat sternotomy was 5 days, without procedure related complications. In three children a repeat sternotomy was avoided by implanting the atrial electrodes during the Fontan operation. All patients improved clinically, including resolution of PLE in four patients. Bradyarrhythmias may lead to significant morbidity after Fontan-type operations. Electrophysiological evaluation is advised at follow-up. The indication for implantation of a DDD pacemaker system should be liberal. Placing atrial electrodes during the Fontan operation, especially in the presence of a right ventricular anatomy, avoids repeat sternotomy. (PACE 2003; 26[Pt. II]:492,495) [source] Percutaneous Treatment for Pacemaker-Associated Superior Vena Cava SyndromePACING AND CLINICAL ELECTROPHYSIOLOGY, Issue 11 2002ALBERT W. CHAN CHAN, A.W., et al.:Percutaneous Treatment for Pacemaker-Associated Superior Vena Cava Syndrome. Superior vena cava (SVC) obstruction is an uncommon but serious complication associated with permanent pacemaker implantation. The mechanical stress associated with pacemaker wires may lead to vessel wall inflammation, fibrosis, and thrombus formation, and ultimately to venous stenosis and occlusion. The surgical treatment of pacemaker related SVC syndrome requires thoracotomy and carries significant morbidity. This article illustrates the authors' initial experience with a "one-step" percutaneous approach for this problem, consisting of percutaneous retrieval of a pacemaker system, followed by venous revascularization with angioplasty and stenting, and installation of a new pacemaker device. [source] Electronic Security Systems and Active Implantable Medical DevicesPACING AND CLINICAL ELECTROPHYSIOLOGY, Issue 8 2002WERNER IRNICH IRNICH, W.: Electronic Security Systems and Active Implantable Medical Devices. How do active implantable medical devices react in the presence of strong magnetic fields in the frequency range between extremely low frequency (ELF) to radiofrequency (RF) as they are emitted by electronic security systems (ESS)? There are three different sorts of ESSs: electronic article surveillance (EAS) devices, metal detector (MDS) devices, and radiofrequency identification (RFID) systems. Common to all is the production of magnetic fields. There is an abundance of literature concerning interference by ESS gates with respect to if there is an influence possible and if such an influence can bear a risk for the AIMD wearers. However, there has been no attempt to study the physical mechanism nor to develop a model of how and under which conditions magnetic fields can influence pacemakers and defibrillators and how they could be disarmed by technological means. It is too often assumed that interference of AIMD with ESS is inevitable. Exogenous signals of similar intensity and rhythm to heart signals can be misinterpreted and, thus, confuse the implant. Important for the interference coupling mechanism is the differentiation between a "unipolar" and a "bipolar" system. With respect to magnetic fields, the left side implanted pacemaker is the most unfavorable case as the lead forms approximately a semicircular area of maximum 225 cm2 into which a voltage can be induced. This assumption yields an interference coupling model that can be expressed by simple mathematics. The worst-case conditions for induced interference voltages are a coupling area of 225 cm2 that is representative for a large human, a homogeneous magnetic field perpendicular to the area formed by the lead, and a unipolar ventricular pacemaker system that is implanted on the left side of the thorax and has the highest interference sensitivity. In bipolar systems the fields must be 17 times larger when compared to a unipolar system to have the same effect. The magnetic field for interfering with ICDs must be 1.7 stronger than that of the most sensitive unipolar pacemaker. The lowest interference thresholds measured over the last 10 years in the low frequency range (16 2/3 Hz,24 kHz) together with thresholds > 24 kHz that were supplied by the CETECOM study are listed. Both sets of data together with the coupling model, allow for judging which fields of ESSs could influence AIMDs. From measurements at gate antennas, it is possible to derive a "maximum allowed field" curve over the whole frequency range, below which no interference will occur. Comparison of data from literature with these maximum allowed fields confirm the correctness of the calculations. Thus, it is possible to predict interference situations in gates if the magnetic field is known. If all future pacemakers were to have the immunity against interference of the better 50% of today's pacemakers, the magnetic field ceiling values could be at least four times higher. The same is true if the ventricular sensitivity is routinely set at 7 mV. Pacemaker manufacturers should consider filter improvement with modern technology, but gate manufacturers should not claim the privilege of being out of bounds. [source] Are Routine Arrhythmia Inductions Necessary in Patients with Pectoral Implantable Cardioverter Defibrillators?JOURNAL OF CARDIOVASCULAR ELECTROPHYSIOLOGY, Issue 2 2000MICHAEL GLIKSON M.D. Routine Arrhythmia Inductions in Patients with ICDs. Introduction: The value of ventricular arrhythmia inductions as part of routine implantable cardioverter defibrillator (ICD) follow-up in new-generation pectoral ICDs is unknown Methods and Results: We performed a retrospective analysis of a prospectively collected database analyzing data from 153 patients with pectoral ICDs who had routine arrhythmia inductions at predismissal, and 3 months and 1 year after implantation. Routine predismissal ventricular fibrillation (VF) induction yielded important findings in 8.8% of patients, all in patients with implantation defibrillation threshold (DFT) , 15 J or with concomitant pacemaker systems. At 3 months and 1 year, routine VF induction yielded important findings in 5.9% and 3.8% of tested patients, respectively, all in patients who had high DFT on prior testing. Ventricular tachycardia (VT) induction at predismissal, and 3 months and 1 year after implantation resulted in programming change in 37.4%, 28.1%, and 13.8% of tested patients, almost all in patients with inducible VT on baseline electrophysiologic study and clinical episodes since implantation. Conclusion: Although helpful in identifying potentially important ICD malfunctions, routine arrhythmia inductions during the first year after ICD implantation may not be necessary in all cases. VF inductions have a low yield in patients with previously low DFTs who lack concomitant pacemakers. VT inductions have a low yield in patients without baseline Inducible VT and in the absence of clinical events. Definite recommendations regarding patient selection must await larger prospective studies as well as consensus in the medical community about what comprises an acceptable risk justifying avoidance of the costs and inconveniences of routine arrhythmia inductions. [source] Induction Ovens and Electromagnetic Interference:PACING AND CLINICAL ELECTROPHYSIOLOGY, Issue 7p1 2003What is the Risk for Patients with Implanted Pacemakers? Electromagnetic fields may interfere with normal pacemaker function. Despite the introduction of modern pacemakers and bipolar lead systems, electromagnetic interference (EMI) still remains to be a concern during daily lives when patients are exposed to cellular phones, electronic security systems, and several household appliances. The aim of this study was to evaluate potential EMI risk of induction ovens, which are increasingly used in private households. The study included 40 consecutive patients (22 men, 18 women; age73 ± 11 years) with implanted DDD, VVI, VDD, and AAI pacemaker systems. The pacemakers were programmed to unipolar sensing and pacing. Sensitivity remained unchanged, if the measured sensing threshold was more than twice the programmed value; otherwise, it was set at half of the measured sensing threshold. Patients were placed in a sitting position at the closest possible distance of about 20 cm between two cooking pots and pacemaker bending the upper part of the body slightly over the induction oven. The energy was increased stepwise to the maximum. One pot was removed and placed again at the highest oven level. Potential interference was monitored continuously. The study showed no incidence of pacemaker malfunction during the entire test while the patients with intrinsic cardiac rhythms were exposed to the induction oven at varying energy strengths. Likewise, there was no external interference when the patients were paced at heart rates of 10,15 beats/min above their heart rates. The programmed parameters remained unchanged after the study. In conclusion, this study shows no EMI risk of an induction oven in patients with bipolar or right-sided unipolar pacemakers. (PACE 2003; 26[Pt. I]:1494,1497) [source] Electromagnetic Interference of an Implantable Loop Recorder by Commonly Encountered Electronic DevicesPACING AND CLINICAL ELECTROPHYSIOLOGY, Issue 10 2000CAREL C. DE COCK De COCK, C.C., et al.: Electromagnetic Interference of an Implantable Loop Recorder by Commonly Encountered Electronic Devices. Electromagnetic interference of pacemaker systems has been well established and can lead to an inappropriate function of these devices. Recently, an implantable loop recorder (ILR) (REVEAL, Medtronic Inc.) has been introduced to evaluate the possible arrhythmic etiology of patients with recurrent syncope. We evaluated the interference of this device in two patients with implantable ILR and in three nonimplanted ILRs with four electromagnetic sources: cellular phones (GSMs), electronic article surveillance systems (EASs), metal detector gates (MDGs), and magnetic resonance imaging (MRI). The GSM did not affect appropriate function of the ILR whereas radiofrequency (RF) EAS could interfere with normal function in implanted and nonimplanted systems. The MDG had no influence on ILR function. The magnetic field induced by the MRI resulted in an irreversible error in one nonimplanted ILR. Therefore, although interference between electromagnetic sources and ILRs appears to be rare in our study, physicians should be aware of possible malfunctioning of these devices. [source] | ||||||||||