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Implantable Devices (implantable + device)

Distribution by Scientific Domains

Medical Sciences	93%

Selected Abstracts

Can Implantable Devices Detect and Pace-Terminate Atrial Fibrillation?

PACING AND CLINICAL ELECTROPHYSIOLOGY, Issue 10 2003
CARSTEN W. ISRAEL
No abstract is available for this article. [source]

A Segmental Polynomial Model of Ventricular Electrograms as a Simple and Efficient Morphology Discriminator for Implantable Devices

ANNALS OF NONINVASIVE ELECTROCARDIOLOGY, Issue 3 2006
Jeffrey L. Williams M.D.
Background: The goal of this study is to construct a polynomial model of the ventricular electrogram (EGM) that faithfully reproduces the EGM and can be implemented in current, low computational power implantable devices. Such a model of ventricular EGMs is still lacking. Methods: New Zealand White rabbits underwent chronic implantation of pacemakers through a left thoracotomy approach. Unipolar ventricular EGMs sampled at a frequency of 1 kHz were stored digitally in 1-minute segments before and after intravenous injection of isoproterenol or procainamide. Each cardiac cycle was divided into a QR and an RQ segment which were modeled separately using a 6th order polynomial equation. Results: The 14 coefficients of each cardiac cycle were reproducible throughout the baseline recordings (r , 0.94, P < 0.002). Isoproterenol caused no changes in the coefficients of the QR segment but significantly altered all but one of the seven coefficients of the RQ segment (p6= 0.0039, p5= 0.017, p4= 0.00007, p3= 0.112, p2= 0.00016, p1= 0.0086, pa= 0.00003). Procainamide caused statistically significant changes in both QR segment (p6= 0.018, p5= 0.287, p4= 0.019, p3= 0.176, p2= 0.016, p1= 0.362, pa= 0.000044) and RQ segment (p6= 0.0028, p5= 0.036, p4= 0.002, p3= 0.058, p2= 0.022, p1= 0.718, pa= 0.0018) coefficients. Conclusion: Our data demonstrate the feasibility of a segmental polynomial equation that reproduces the phases of depolarization and repolarization of the rabbit EGM. This model is reproducible and demonstrates the expected changes with antiarrhythmic drug administration. If reproduced in humans, these findings can have wide applications in patients with implantable devices, ranging from morphologic discrimination of arrhythmias to early detection of metabolic derangements or drug effects. [source]

Systematic review: applications and future of gastric electrical stimulation

ALIMENTARY PHARMACOLOGY & THERAPEUTICS, Issue 7 2006
J. ZHANG
Summary Background, Over the past 20 years, gastric electrical stimulation has received increasing attention among researchers and clinicians. Aim, To give a systematic review on the effects, mechanisms and applications of gastric electrical stimulation. Methods, Medline was used to identify the articles to be included in this review. Key words used for the search included gastric electrical stimulation, gastric pacing, electrical stimulation, stomach, gastrointestinal motility, central nervous system, gastroparesis, nausea and vomiting; obesity and weight loss. Combinational uses of these keywords were made to identify relevant articles. Most of the articles included in this review ranged from 1985 to 2006. Results, Based on the general search, the review was structured as follows: (i) peripheral and central effects and mechanisms of gastric electrical stimulation; (ii) clinical applications of gastric electrical stimulation for gastroparesis and obesity and (iii) future development of gastric electrical stimulation. Conclusions, Great progress has been made during the past decades. Gastric electrical stimulation has been shown to be effective in normalizing gastric dysrhythmia, accelerating gastric emptying and improving nausea and vomiting. Implantable device has been made available for treating gastroparesis as well as obesity. However, development of a new device and controlled clinical studies are required to further prove clinical efficacy of gastric electrical stimulation. [source]

In Vitro and Computational Thrombosis on Artificial Surfaces With Shear Stress

ARTIFICIAL ORGANS, Issue 7 2010
Scott C. Corbett
Abstract Implantable devices in direct contact with flowing blood are associated with the risk of thromboembolic events. This study addresses the need to improve our understanding of the thrombosis mechanism and to identify areas on artificial surfaces susceptible to thrombus deposition. Thrombus deposits on artificial blood step transitions are quantified experimentally and compared with shear stress and shear rate distributions using computational fluid dynamics (CFD) models. Larger steps, and negative (expanding) steps result in larger thrombus deposits. Fitting CFD results to experimental deposit locations reveals a specific shear stress threshold of 0.41 Pa or a shear rate threshold of 54 s,1 using a shear thinning blood viscosity model. Thrombosis will occur below this threshold, which is specific to solvent-polished polycarbonate surfaces under in vitro coagulation conditions with activated clotting time levels of 200,220 s. The experimental and computational models are valuable tools for thrombosis prediction and assessment that may be used before proceeding to clinical trials and to better understand existing clinical problems with thrombosis. [source]

Health Care Supply Chain Design: Toward Linking the Development and Delivery of Care Globally,

DECISION SCIENCES, Issue 2 2009
Kingshuk K. Sinha
ABSTRACT This article is motivated by the gap between the growing demand and available supply of high-quality, cost-effective, and timely health care, a problem faced not only by developing and underdeveloped countries but also by developed countries. The significance of this problem is heightened when the economy is in recession. In an attempt to address the problem, in this article, first, we conceptualize care as a bundle of goods, services, and experiences,including diet and exercise, drugs, devices, invasive procedures, new biologics, travel and lodging, and payment and reimbursement. We then adopt a macro, end-to-end, supply chain,centric view of the health care sector to link the development of care with the delivery of care. This macro, supply chain,centric view sheds light on the interdependencies between key industries from the upstream to the downstream of the health care supply chain. We propose a framework, the 3A-framework, that is founded on three constructs,affordability, access, and awareness,to inform the design of supply chain for the health care sector. We present an illustrative example of the framework toward designing the supply chain for implantable device,based care for cardiovascular diseases in developing countries. Specifically, the framework provides a lens for identifying an integrated system of continuous improvement and innovation initiatives relevant to bridging the gap between the demand and supply for high-quality, cost-effective, and timely care. Finally, we delineate directions of future research that are anchored in and follow from the developments documented in the article. [source]

Measuring Quality of Life in Stroke Subjects Receiving an Implanted Neural Prosthesis for Drop Foot

ARTIFICIAL ORGANS, Issue 5 2010
Anke I. Kottink
Abstract The aim was to determine if the treatment of a drop foot by means of an implantable two-channel peroneal nerve stimulator improves health-related quality of life (HRQoL). All subjects were measured at baseline and after a follow-up period of 12 and 26 weeks. Twenty-nine stroke survivors with chronic hemiplegia with drop foot who fulfilled the predefined inclusion and exclusion criteria were included in the present randomized controlled trial. The intervention group received an implantable two-channel peroneal nerve stimulator for correction of their drop foot. The control group continued using their conventional walking device, consisting of an ankle-foot orthosis, orthopedic shoes, or no device. HRQoL was assessed in two different ways: (i) by taking descriptive measures, that is, the Short Form-36 (SF-36; generic measure) and the Disability Impact Profile (DIP; specific measure); and (ii) by obtaining preference-based utilities both measured with the time trade-off (direct way) and by calculating them from the EuroQol (EQ-5D) and SF-36. A significant positive effect of the implantable device was found on the physical functioning domain, the general health domain, and the physical component summary score of the SF-36. For the DIP, a significant improvement was found on the domains mobility, self-care, and psychological status in the intervention group. Regarding the preference-based utility measures, a significant effect was found for the utility index calculated from the EQ-5D. The implantable two-channel peroneal nerve stimulator seems to be efficient to improve HRQoL, mainly the domains related to physical functioning. A relation was present between the utility indexes calculated from the EQ-5D and SF-36. [source]

Recharging the Battery of Implantable Biomedical Devices by Light

ARTIFICIAL ORGANS, Issue 10 2009
Carlos Algora
Abstract This article describes a new powering system for implantable medical devices that could significantly increase their lifetime. The idea is based on the substitution of the usual implantable device battery for an electric accumulator (rechargeable battery), which is fed by the electric power generated by a photovoltaic converter inside the implantable device. Light impinges on the photovoltaic device through an optical fiber going from the photovoltaic device to just beneath the patient's epidermis. Light can enter the optical fiber by passing through the skin. A complete power-by-light system has been developed and tested with a real implantable pulse generator for spinal cord stimulation. The feasibility of the proposed system has been evaluated theoretically. For example, after 13 h/week of laser exposure, the lifetime of the implantable device would increase by 50%. Other combinations resulting in lifetime increases of more than 100% are also possible. So, the proposed system is now ready to take a further step forward: in vivo animal testing. [source]

Patient-adjusted intermittent electrostimulation for treating stress and urge urinary incontinence

BJU INTERNATIONAL, Issue 1 2004
Israel Nissenkorn
OBJECTIVE To assess the safety and efficacy of pelvic floor muscle electrostimulation (ES) in women with stress urinary incontinence (SUI) or mixed UI (MUI, urge and interstitial cystitis), using a new portable electrostimulator (Miniaturo, Biocontrol Medical Inc., Yehud, Israel) which delivers different forms of stimulation for treating these two conditions. PATIENTS AND METHODS For SUI the stimulator is activated on demand only by a sudden increase in intra-abdominal pressure; for frequency and urgency a milder, continuous ES is used. The intensity of ES can be adjusted according to the patient's sensation. Women were enrolled into the study after satisfying inclusion criteria and pad testing; 23 participated in two study groups, i.e. 16 with SUI and seven with MUI (severe frequency, urgency and urge, and mild SUI). The pelvic floor muscles were stimulated through an electrode inserted paraurethrally, positioned similarly in all patients. In patients with SUI and MUI a pressure sensor was also inserted into the rectum, to record intra-abdominal pressure. Stimulation was applied for 1,4 h in patients with SUI and for 6 h in those with MUI. The evaluation was based on urinary symptoms (frequency, urgency, leaking episodes), quality-of-life questionnaires and pad tests at baseline and during stimulation. RESULTS All patients in both groups improved significantly; of the 16 patients with SUI, nine were completely dry during ES, and the remaining seven had a reduced mean pad weight, from 23 to 6 g (74%). There was no significant reduction in pad weight after sham ES (17 g before vs 24.2 g after). In four patients with SUI who continued ES for 4 h the mean cumulative stimulation time (calculated from the stimulator memory) was 3 min (1.3% of 4 h). In the MUI group there were no leakage episodes during ES and significant reductions in voiding variables (Student's t -test) in all. The mean (Sd) voiding frequency, urinary urgency and leaking episodes decreased from 8.1 (4.2) to 1.9 (1.5), 6.4 (2.3) to 0.7 (1.3) and 2.1 (0.7) to 0.7 (0.5) (all P < 0.001), respectively. CONCLUSIONS The concept of this ES system for treating UI is promising; this study supports the efficacy of this form of ES but no conclusions about clinical efficacy are possible at this stage, and thus a trial to evaluate the safety and efficacy of this implantable device is ongoing. [source]

Audiometric evaluation of an attempt to optimize the fixation of the transducer of a middle-ear implant to the ossicular chain with bone cement

CLINICAL OTOLARYNGOLOGY, Issue 1 2004
A. Snik
Audiometric evaluation of an attempt to optimize the fixation of the transducer of a middle-ear implant to the ossicular chain with bone cement Typically, an implantable hearing device consists of a transducer that is coupled to the ossicular chain and electronics. The coupling is of major importance. The Vibrant Soundbridge (VSB) is such an implantable device; normally, the VSB transducer is fixed to the ossicular chain by means of a special clip that is crimped around the long process of the incus. In addition to crimping, bone cement was used to optimize the fixation in six patients. Long-term results were compared to those of five controls with crimp fixation alone. To assess the effect of bone cement (SerenoCem®, Corinthian Medical Ltd, Nottingham, UK) on hearing thresholds, long-term post-surgery thresholds were compared to pre-surgery thresholds. Bone cement did not have any negative effect. Next, to test the hypothesis that aided thresholds might be better with the use of bone cement, aided thresholds were studied. After correction for the severity of hearing loss, only a small difference was found between the two groups at one frequency, viz. 2 kHz. It was concluded that there was no negative effect of using bone cement; however, there is also no reason to use bone cement in VSB users on a regular basis. [source]

Successful Cervical MR Scan in a Patient Several Hours after Pacemaker Implantation

PACING AND CLINICAL ELECTROPHYSIOLOGY, Issue 10 2009
DORITH GOLDSHER M.D.
Recent data showed that patients with electrical implanted devices may under certain conditions be scanned safely by magnetic resonance imaging (MRI). The device must have been in place preferably for at least 4,8 weeks [Correction added after online publication 31-Aug-2009: number of weeks has been updated.] prior to MR imaging to allow healing and pacemaker pocket formation. We report on a patient with quadriplegia and suspected epidural hematoma referred for MR scan a day after he had a pacemaker implantation. The patient was also pacemaker-dependent. After considering the risk/benefit ratio in this patient, it was decided to perform the scan. The pacemaker was reprogrammed. MRI was performed under strict monitoring. A spinal cord contusion at the level of C1,3 was diagnosed. Based on the imaging findings no invasive procedure was done. Device interrogation found no change in sensing or pacing parameters or in the pacemaker's battery. At the end of the scan, the device was reprogrammed back to the initial settings. In this population, each scan should be discussed thoroughly and the risks to benefit ratio should be considered. Given appropriate precautions, in well-experienced imaging centers, MRI may be safely performed in patients with permanent cardiac electronic implantable devices. [source]

Automatic Mode Switching of Implantable Pacemakers: I. Principles of Instrumentation, Clinical, and Hemodynamic Considerations

PACING AND CLINICAL ELECTROPHYSIOLOGY, Issue 6 2002
CHU-PAK LAU
LAU, C.-P., et al.: Automatic Mode Switching of Implantable Pacemakers: I. Principles of Instrumentation, Clinical, and Hemodynamic Considerations. Automatic mode switching (AMS) is now a programmable function in most contemporary dual chamber pacemakers. Atrial tachyarrhythmias are detected when the sensed atrial rate exceeds a "rate-cutoff,""running average,""sensor-based physiological" rate, or using "complex" detection algorithms. AMS algorithms differ in their atrial tachyarrhythmia detection method, sensitivity, and specificity and, thus, respond differently to atrial tachyarrhythmia in terms of speed to the AMS onset, rate stability of the response, and speed to resynchronize to sinus rhythm. AMS is hemodynamically beneficial, and most patients with atrial tachyarrhythmias are symptomatically better with an AMS algorithm in their pacemakers. New diagnostic capabilities of pacemaker especially stored electrograms not only allow programming of the AMS function, but enable quantification of atrial fibrillation burden that facilitate clinical management of patients with implantable devices who have concomitant atrial tachyarrhythmia. [source]

Effect of Ventricular Fibrillation Duration on the Defibrillation Threshold in Humans

PACING AND CLINICAL ELECTROPHYSIOLOGY, Issue 1 2002
RAINER GRADAUS
GRADAUS, R., et al.: Effect of Ventricular Fibrillation Duration on the Defibrillation Threshold in Humans. Early during ventricular fibrillation, the defibrillation threshold may be low, as ventricular fibrillation most probably arises from a localized area with only a few wavefronts and the effects of global ischemia, ventricular dilatation, and sympathetic discharge have not yet fully developed. The purpose of this study was to explore the effect of the timing of shock delivery in humans. During implantation of an ICD in 26 patients (24 men, 60 ± 11 years, 19 coronary artery disease, NYHA 2.2 ± 0.4, left ventricular ejection fraction 0.42 ± 0.16), the defibrillation threshold was determined after approximately 10 and 2 seconds of ventricular fibrillation. Ventricular fibrillation was induced by T wave shocks. Mean defibrillation threshold was 9.9 ± 3.6 J after 10.3 ± 1.0 seconds. Within 2 seconds, 20 of 26 patients could be successfully defibrillated with , 8 J. In these patients, the mean defibrillation threshold was 4.0 ± 2.1 J after 1.4 ± 0.3 seconds compared to 9.5 ± 3.1 J after 10.2 ± 1.1 seconds (P < 0.001). There were no clinical differences between patients who could be successfully defibrillated within 2 seconds and those patients without successful defibrillation within 2 seconds. In the majority of patients, the defibrillation threshold was significantly lower within the first few cycles of ventricular fibrillation than after 10 seconds of ventricular fibrillation. These results should lead to exploration of earlier shock delivery in implantable devices. This could possibly reduce the incidence of syncope in patients with rapid ventricular tachyarrhythmias and ICDs. [source]

Placing of tunneled central venous catheters prior to induction chemotherapy in children with acute lymphoblastic leukemia,

PEDIATRIC BLOOD & CANCER, Issue 2 2010
Mette Møller Handrup MD
Abstract Background Tunneled central venous catheters (CVCs) are inevitable in children with acute lymphoid leukemia (ALL). The aim of this study was to evaluate the risk of CVC-related complications in children with ALL in relation to timing of catheter placement and type of catheter. Procedure All children hospitalized from January 2000 to March 2008 with newly diagnosed ALL and with double-lumen total implantable devices (TIDs) or tunneled external catheters (TEs) were included retrospectively. We only used data related to the patient's first catheter. Results We included 98 children; 35 received a TID and the remaining 63 received a TE. A total number of 29,566 catheter days and 93 catheter-associated blood stream infections (CABSI) was identified. We found a CABSI rate of 3.1/1,000 catheter days (5.4/1,000 catheter days for TEs and 1.4/1,000 catheter days for TIDs, incidence rate ratio (IRR) 3.82 (95% CI 2.37,6.35) P,=,0.0001). No difference was found in CABSI between neither early versus later placed TIDs (IRR,=,0.99 (95% CI 0.41,2.45) P,=,0.98) nor early versus later placed TEs (IRR,=,0.81 (95% CI 0.40,1.86) P,=,0.54). We found no difference between early and later placed catheters regarding non-elective removal (RR,=,0.86 (95% CI 0.72,1.03) P,=,0.09). TEs had a higher risk of non-elective removal compared with TIDs (RR,=,3.95 (95% CI 1.88,8.29) P,<,0.001). Conclusions The study did not find that children with ALL and with early placed CVCs experienced significantly more complications compared with children with late placed catheters. This study found that children with ALL and TEs experienced more complications than children with TIDs. Pediatr Blood Cancer. 2010;55:309,313. © 2010 Wiley,Liss, Inc. [source]

A Segmental Polynomial Model of Ventricular Electrograms as a Simple and Efficient Morphology Discriminator for Implantable Devices

A Novel Low Temperature Transcutaneous Energy Transfer System Suitable for High Power Implantable Medical Devices: Performance and Validation in Sheep

ARTIFICIAL ORGANS, Issue 5 2010
Thushari D. Dissanayake
Abstract Transcutaneous energy transfer (TET) systems use magnetic fields to transfer power across the skin without direct electrical connectivity. This offers the prospect of lifetime operation and overcomes risk of infection associated with wires passing through the skin. Previous attempts at this technology have not proved suitable due to poor efficiency, large size, or tissue damage. We have developed a novel approach utilizing frequency control that allows for wide tolerance in the alignment between internal and external coils for coupling variations of 10 to 20 mm, and relatively small size (50 mm diameter, 5 mm thickness). Using a sheep experimental model, the secondary coil was implanted under the skin in six sheep, and the system was operated to deliver a stable power output to a 15 W load continuously over 4 weeks. The maximum surface temperature of the secondary coil increased by a mean value of 3.4 ± 0.4°C (±SEM). The highest absolute mean temperature was 38.3°C. The mean temperature rise 20 mm from the secondary coil was 0.8 ± 0.1°C. The efficiency of the system exceeded 80% across a wide range of coil orientations. Histological analysis revealed no evidence of tissue necrosis or damage after four weeks of operation. We conclude that this technology is able to offer robust transfer of power to implantable devices without excess heating causing tissue damage. [source]