Évaluation d’une intervention infirmière basée sur une approche caring et cognitive comportementale sur l’acceptation d’un défibrillateur cardiaque implantable

Le taux de mortalité chez les patients à risque d’arythmies cardiaques menaçantes à la vie a été considérablement réduit grâce au défibrillateur cardiaque implantable (DCI). Toutefois, des préoccupations uniques face au DCI, y compris les chocs que l’appareil peut déclencher, sont susceptibles de provoquer des symptômes d'anxiété et une limitation perçue des activités chez les porteurs de DCI. Ces réactions émotives et modifications de comportement peuvent affecter l’acceptation du patient envers le DCI. Cette étude pilote randomisée avec groupe contrôle (n=15 /groupe) visait à examiner la faisabilité et l'acceptabilité d'une intervention infirmière individualisée de même que ses effets préliminaires sur l’anxiété, le fonctionnement dans les activités de la vie quotidienne et l’acceptation du DCI auprès de nouveaux porteurs de DCI. L'intervention infirmière, basée sur la théorie du Human Caring et teintée d’une approche cognitive comportementale, ciblait les préoccupations individuelles face au DCI. À partir des préoccupations identifiées, l’infirmière intervenait en mettant l'accent sur les croyances contraignantes du patient, qui pouvaient mener à de l’anxiété et des comportements d'évitement. Après randomisation, les patients du groupe intervention (GI) ont participé à un premier entretien en face-à-face avant le congé hospitalier. Subséquemment, deux entretiens se sont faits par téléphone, à environ 7 et 14 jours suite au congé hospitalier. Les résultats soutiennent la faisabilité et l’acceptabilité du devis de l’étude et de l’intervention évaluée. De plus, ils soulignent le potentiel de l’intervention à diminuer les sentiments anxieux chez les participants du GI. Les résultats de cette étude pilote offrent des pistes de recherches futures et permettront de guider la pratique clinique.

Towards Batteryless Cardiac Implantable Electronic Devices – The Swiss Way

Energy harvesting devices are widely discussed as an alternative power source for todays active implantable medical devices. Repeated battery replacement procedures can be avoided by extending the implants life span, which is the goal of energy harvesting concepts. This reduces the risk of complications for the patient and may even reduce device size. The continuous and powerful contractions of a human heart ideally qualify as a battery substitute. In particular, devices in close proximity to the heart such as pacemakers, defibrillators or bio signal (ECG) recorders would benefit from this alternative energy source. The clockwork of an automatic wristwatch was used to transform the hearts kinetic energy into electrical energy. In order to qualify as a continuous energy supply for the consuming device, the mechanism needs to demonstrate its harvesting capability under various conditions. Several in-vivo recorded heart motions were used as input of a mathematical model to optimize the clockworks original conversion efficiency with respect to myocardial contractions. The resulting design was implemented and tested during in-vitro and in-vivo experiments, which demonstrated the superior sensitivity of the new design for all tested heart motions.

New encapsulating materials for implantable devices

Synthetic, natural, or composite, biomaterials occupy a key position in the management of disease and support continuous advancement of health care. Clinical utility of many permanent and biodegradable implants can be significantly improved via surface modification. Here, we discuss a novel polymer material developed from essential oil-based monoterpene alcohol using plasma polymerisation. The developed coatings are cytocompatible and limit adhesion and proliferation of a variety of pathogens. The coating can also be used to control degradation behaviour of resorbable materials, such as magnesium.

New signal processing algorithms for automated external defibrillators

[ES]La fibrilación ventricular (VF) es el primer ritmo registrado en el 40\,\% de las muertes súbitas por paro cardiorrespiratorio extrahospitalario (PCRE). El único tratamiento eficaz para la FV es la desfibrilación mediante una descarga eléctrica. Fuera del hospital, la descarga se administra mediante un desfibrilador externo automático (DEA), que previamente analiza el electrocardiograma (ECG) del paciente y comprueba si presenta un ritmo desfibrilable. La supervivencia en un caso de PCRE depende fundamentalmente de dos factores: la desfibrilación temprana y la resucitación cardiopulmonar (RCP) temprana, que prolonga la FV y por lo tanto la oportunidad de desfibrilación. Para un correcto análisis del ritmo cardiaco es necesario interrumpir la RCP, ya que, debido a las compresiones torácicas, la RCP introduce artefactos en el ECG. Desafortunadamente, la interrupción de la RCP afecta negativamente al éxito en la desfibrilación. En 2003 se aprobó el uso del DEA en pacientes entre 1 y 8 años. Los DEA, que originalmente se diseñaron para pacientes adultos, deben discriminar de forma precisa las arritmias pediátricas para que su uso en niños sea seguro. Varios DEAs se han adaptado para uso pediátrico, bien demostrando la precisión de los algoritmos para adultos con arritmias pediátricas, o bien mediante algoritmos específicos para arritmias pediátricas. Esta tesis presenta un nuevo algoritmo DEA diseñado conjuntamente para pacientes adultos y pediátricos. El algoritmo se ha probado exhaustivamente en bases de datos acordes a los requisitos de la American Heart Association (AHA), y en registros de resucitación con y sin artefacto RCP. El trabajo comenzó con una larga fase experimental en la que se recopilaron y clasificaron retrospectivamente un total de 1090 ritmos pediátricos. Además, se revisó una base de arritmias de adultos y se añadieron 928 nuevos ritmos de adultos. La base de datos final contiene 2782 registros, 1270 se usaron para diseñar el algoritmo y 1512 para validarlo. A continuación, se diseñó un nuevo algoritmo DEA compuesto de cuatro subalgoritmos. Estos subalgoritmos están basados en un conjunto de nuevos parámetros para la detección de arritmias, calculados en diversos dominios de la señal, como el tiempo, la frecuencia, la pendiente o la función de autocorrelación. El algoritmo cumple las exigencias de la AHA para la detección de ritmos desfibrilables y no-desfibrilables tanto en pacientes adultos como en pediátricos. El trabajo concluyó con el análisis del comportamiento del algoritmo con episodios reales de resucitación. En los ritmos que no contenían artefacto RCP se cumplieron las exigencias de la AHA. Posteriormente, se estudió la precisión del algoritmo durante las compresiones torácicas, antes y después de filtrar el artefacto RCP. Para suprimir el artefacto se utilizó un nuevo método desarrollado a lo largo de la tesis. Los ritmos desfibrilables se detectaron de forma precisa tras el filtrado, los no-desfibrilables sin embargo no.

A novel implantable multichannel silicon-based microelectrode

Silicon-based microelectrodes have been confirmed to be helpful in neural prostheses. The fabricated 7-channel silicon-based microelectrode was feasible to be implanted into the brain cortex. The manufacturing process by microelectromechanical system (MEMS) technology was detailed with four photolithographic masks. The microscopic photographs and SEM images indicated that the probe shank was 3mm long, 100 mu m wide and 20 mu m thick with the recording sites spaced 120 mu m apart for good signal isolation. To facilitate the insertion and minimize the trauma, the microelectrode is narrowed down gradually near the tip with the tip taper angle of 6 degrees. Curve of the single recording site impedance versus frequency was shown by test in vitro and the impedance declined from 150.5 k Omega to 6.0 k Omega with frequency changing from 10 k to 10MHz.

Subretinal implantable micro photodetector array

A subretinal implant device, Micro Photo Diode Array, which can partly imitate the function of photoreceptor cells, was presented. Process to fabricate the MPDA and characteristics of the MPDA in vivo were described.

Implantable Microsystem for Wireless Neural Recording Applications

A prototype microsystem is presented for wireless neural recording application. An inductive link was built for transcutaneous wireless power transfer and data transmission. Total 16.5 mW power and 50 bps - 2.5 Kbps command data can be received over 1 - 5 MHz with a distance of 0-10 mm. The integrated amplifiers were designed with a limited bandwidth for neural signals acquisition. The gain of 60 dB was obtained by preamplifier at 7 Hz - 3 KHz. An integrated FM transmitter was used to transmit the extracted neural signals to external equipments with 0.374 - 2 mW power comsumption and a maximum data rate of 500 Kbps at 100 MHz. All the integrated circuits modules except the power recovery circuit were tested or stimulated under a 3.3 V power supply, and fabricated in standard CMOS processing.

Subretinal implantable artificial photoreceptor

The present study reports a subretinal implant device which can imitate the function of photoreceptor cells. Photodiode (PD) arrays on the chip translate the incident light into current according to the intensity of light. With an electrode at the end of every photodiode, the PDs transfer the current to the remnant healthy visual cells such as bipolar cells and horizontal cells and then activate these cells. Biocompatible character of the materials and artificial photoreceptor itself were tested and the photoelectric characteristics of the chips in simulative condition were described and discussed.

The mechanical and rheological characterisation of implantable medical devices formulated from binary mixtures of cellulose derivatives

This study highlights the potential associated with utilising multi-component polymeric gels to formulate materials that possess unique rheological and mechanical properties. The synergistic effect* and interaction between hydroxyethylcellulose (HEC) and sodium carboxymethylcellulose (NaCMC), polymers which are commonly employed as drug delivery platforms for implantable medical devices (1), have been determined using dynamic, continuous shear and texture profile analysis. * The difference between the actual response of a binary mixture and the sum of the two components comprising the mixture Increases in polymer concentration resulted in an increase in G', G? and ?' whereas tan d decreased. Similarly, significant increases were also apparent in continuous shear and texture analysis. All binary mixtures showed positive synergy values which may suggest associative interaction between the two components.

Fluoroscopic and electrical assessment of a series of defibrillation leads:prevalence of externalized conductors

Introduction : Insulation defects with externalized conductors have been reported in the St. Jude Riata(®) family of defibrillation leads (St. Jude Medical, Sylmar, CA, USA). The objective of the Northern Ireland Riata(®) lead screening program was to identify insulation defects and externalized conductors by systematic fluoroscopic and electrical assessment in a prospectively defined cohort of patients. We sought to estimate the prevalence, identify risk factors, and determine the natural history of this abnormality. Methods : All patients with a Riata(®) lead under follow-up at the Royal Victoria Hospital were invited for fluoroscopic imaging and implantable cardioverter-defibrillator lead parameter checks. Fluoroscopic images were read independently by two cardiologists and the presence of externalized conductors was classified as positive, negative, or borderline. Results: One hundred and sixty-five of 212 patients with a Riata lead were evaluated by fluoroscopy and lead parameter measurements. The mean duration after implantation was 3.98+/-1.43 years. After screening 25 (15%) patients were classified as positive, 137 (83%) negative, and three (1.8%) borderline. Time since implantation (P = 0.001), presence of a single coil lead (P = 0.042), and patient age (P = 0.034) were significantly associated with externalized conductors. The observed rate of externalized conductors was 26.9% for 8-French and 4.7% for 7-French leads. No leads that were identified prospectively with externalized conductors had electrical abnormalities. Seven of 25 (28%) patients had a defective lead extracted by the end of this screening period. Conclusion: A significant proportion (15%) of patients with a Riata lead had an insulation breach 4 years after implantation. High-resolution fluoroscopic imaging in at least two orthogonal views is required to identify this abnormality. (PACE 2012;35:1498-1504).

Use of the impedance cardiogram in public access defibrillators as an indicator of cardiopulmonary resuscitation effectiveness

An algorithm has been developed for a Public Access Defibrillator which utilizes distinctive features from the impedance cardiogram (ICG) recorded via defibrillator pads to advise both lay users and minimally trained bystanders to ensure CPR effectiveness. Following ethical approval, data were collected and marked. CPR was administered by trained personnel. 211 cases were gathered and the training set included 106 cases. A retrospective analysis was carried out of simultaneously recorded ECG and ICG. The speed of compressions was calculated by counting the outstanding waves in the ICG during CPR. Also if the base-to-peak amplitude of the ICG is greater than a minimum threshold, the corresponding compressions were classified as being applied with adequate force. For the validation set, adequate speed was detected with 91.45% sensitivity and 96.27% specificity (79826s) and adequate force with 99.94% sensitivity and 97.91% specificity (91973s). © 2011 CCAL.

Robust implantable antenna for in-body communications

A compact implantable printed meandered folded dipole antenna with a volume of 101.8 mm3 and robust performance is presented for operation in the 2.4 GHz medical ISM bands. The implant antenna is shown to maintain its return loss performance in the 2360???2400 MHz, 2400???2483.5 MHz and 2483.5???2500 MHz frequency bands, simulated in eleven different body tissue types with a broad range of electrical properties. Bandwidth and resonant frequency changes are reported for the same antenna implanted in high water content tissues such as muscle and skin as well as low water content tissues such as subcutaneous fat and bone. The antenna was also shown to maintain its return loss performance as it was moved towards a tissue boundary within a simulated phantom testbed.

Correcting Interdevice Bias of Horizontal White-to-White and Sulcus-to-Sulcus Measures Used for Implantable Collamer Lens Sizing.

PURPOSE: To assess the agreement and repeatability of horizontal white-to-white (WTW) and horizontal sulcus-to-sulcus (STS) diameter measurements and use these data in combination with available literature to correct for interdevice bias in preoperative implantable collamer lens (ICL) size selection. DESIGN: Interinstrument reliability and bias assessment study. METHODS: A total of 107 eyes from 56 patients assessed for ICL implantation at our institution were included in the study. This was a consecutive series of all patients with suitable available data. The agreement and bias between WTW (measured with the Pentacam and BioGraph devices) and STS (measured with the HiScan device) were estimated. RESULTS: The mean spherical equivalent was -8.93 ± 5.69 diopters. The BioGraph measures of WTW were wider than those taken with the Pentacam (bias = 0.26 mm, P < .01), and both horizontal WTW measures were wider than the horizontal STS measures (bias >0.91 mm, P < .01). The repeatability (Sr) of STS measured with the HiScan was 0.39 mm, which was significantly reduced (Sr = 0.15 mm) when the average of 2 measures was used. Agreement between the horizontal WTW measures and horizontal STS estimates when bias was accounted for was г = 0.54 with the Pentacam and г = 0.64 with the BioGraph. CONCLUSIONS: Large interdevice bias was observed for WTW and STS measures. STS measures demonstrated poor repeatability, but the average of repeated measures significantly improved repeatability. In order to conform to the US Food and Drug Administration's accepted guidelines for ICL sizing, clinicians should be aware of and account for the inconsistencies between devices.

Omega-3 fatty acids, cardiovascular disease and stability of atherosclerotic plaques

Long-chain n-3 polyunsaturated fatty acids are found in oily fish and in fish oils and similar preparations. Substantial evidence from epidemiological and case-control studies indicates that consumption of fish, oily fish and long-chain n-3 fatty acids reduces risk of cardiovascular mortality. Secondary prevention studies using long-chain n-3 fatty acids in patients post-myocardial infarction have shown a reduction in total and cardiovascular mortality with an especially potent effect on sudden death. Long-chain n-3 fatty acids have been shown to beneficially modify a range of cardiovascular risk factors, which may result in primary cardiovascular prevention. However, reduced non-fatal and fatal events and a reduction in sudden death probably involve other mechanisms. Reduced thrombosis following long-chain n-3 fatty acids may play a role. A decrease in arrhythmias is a favoured mechanism of action of long-chain n-3 fatty acids and is supported by cell culture and animal studies. However human trials using implantable cardiac defibrillators have produced inconsistent findings and a recent meta-analysis does not support this mechanism of action. An alternative mechanism of action may be stabilisation of atherosclerotic plaques by long-chain n-3 fatty acids. This is suggested by one published human study which showed that incorporation of long-chain n-3 fatty acids into plaques collected at carotid endarterectomy resulted in fewer macrophages in the plaque and a morphology indicative of increased stability. These findings are supported from observations in an animal model and suggest that the primary effect of long-chain n-3 fatty acids might be on macrophages within the plaque.