Detection algorithms in implantable cardioverter defibrillators

Presents a review of the evolution of tachycardia fibrillation detection algorithms designed for implantable cardioverter defibrillators (ICD) including those that have been incorporated into first, second, and third generation devices. The major emphasis of this review is an overview of the development of new and innovative means for improved detection in next-generation devices. Time-domain and frequency-domain methods of electrogram analyses are described, limitations are cited and promising new proposals for increased specificity which address the false shock incidence are presented     

Arrhythmia discrimination in implantable cardioverter defibrillators using support vector machines applied to a new representation of electrograms

Arrhythmia classification remains a major challenge for appropriate therapy delivery in implantable cardioverter defibrillators (ICDs). The purpose of this paper is to present a new algorithm for arrhythmia discrimination based on a statistical classification by support vector machines of a novel 2-D representation of electrograms (EGMs) named spatial projection of tachycardia (SPOT) EGMs. SPOT-based discrimination algorithm provided sensitivity and specificity of 98.8% and 91.3%, respectively, on a test database. A simplified version of the algorithm is also presented, which can be directly implemented in the ICD.     

Implantable pacemakers

Advances in cardiac pacing have greatly reduced the size of pacemakers, while improving their longevity and reliability, expanding their clinical applications and increasing their sophistication in terms of programming and automatic features. Significant reductions in the size of pacing systems have been mainly due to improvements in power sources, increased circuit integration, hybrid packaging, and the development of smaller leads and lead connectors. The use of sophisticated microprocessors has transformed some pacemakers into implantable computers. The incorporation of memory is enabling modern pacing devices to become more like Holter monitors, able to store significant amounts of intracardiac data. A trend toward the use of sensor technology has enabled pacemakers to provide rate response, taking the place of a damaged sinus node     

External defibrillators and emergency external pacemakers

The first experimental defibrillation occurred in 1900. Zoll first achieved external defibrillation of a human heart in 1956 and the first commercial external manual defibrillators were introduced in 1961. The author discusses the steady improvements in manual defibrillator performance which have occurred since 1961, particularly relating to added functionality, event documentation, and telecommunications, and speculate on likely trends in the next few years. The author then considers the most important developments of the last 30 years, i.e., the development and successful use of smart automatic or advisory external defibrillators (AEDs) which are capable of accurately analyzing the ECG and of making reliable shock decisions. The first generation AEDs were intended for use by paramedics or nurses. There is growing interest in developing very simple, reliable, and low cast AEDs for widespread use by minimally trained first responders (e.g., fire fighters) and even lay persons (“public access defibrillation”) and existing of forthcoming AEDs for that application are discussed. Finally, the author briefly discusses external pacemakers and self-adhesive electrodes which have become common features of modern defibrillators     

植入式片上系统的发展与现状

对目前国际上植入式片上系统的最新研究现状进行分析,总结了植入式生物信号检测与微电刺激系统的基本结构模型;介绍了系统的工作原理,讨论了系统实现的关键技术、存在的问题及可能的解决方法;最后,对植入式系统的发展趋势进行了展望.     

Implantable neuromorphic vision chips

The implantable neuromorphic vision chips are analysed and implemented. These proposed analogue integrated circuits are to implement four cell functions of the retina for implant. These retinal cells are photoreceptor cells, horizontal cells, bipolar cells, and ganglion cells. All simulation results are successfully verified and consistent with researches on biological retinas.     

Implantable Biomimetic Microelectronics Systems

This issue provides a comprehensive overview of state-of-the-art implantable biomimetic microelectronics systems, the diverse range of applications they serve, and the technologies enabling such systems. The 13 papers in this issue are summarized here.     

Implantable Blood Pressure Telemetry System

A telemetry system for long-term monitoring of the blood pressure of unrestrained animals is described. The wholly implantable transmitter is equipped with a pressure transducer suitable for chronic intravascular use. To achieve high performance and long battery life, a greater number of components were used than in conventional implantable devices. Pulse interval modulation is used with a mean sampling rate significantly higher than twice the maximum signal frequency. Together with a controlled pulse window in the receiver, an effective reduction of ignition spark interferences with the weak transmitted signal could therewith be achieved.     

Implantable telemetry in biomedical research

Animal models of human physiology, pathology, and pharmacology are indispensable tools in biomedical research. Totally implantable radiotelemetry systems provide an invaluable appendage to animal models because these systems are a means for acquisition of otherwise unavailable experimental data. Implantable systems for measurement of velocity, volume flow, dimension, pressure, strain, bioelectric potential, temperature, and pH in selected applications are discussed.     

Wearable and Implantable Triboelectric Nanogenerators

Triboelectric nanogenerators (TENGs) are a promising technology to convert mechanical energy to electrical energy based on coupled triboelectrification and electrostatic induction. With the rapid development of functional materials and manufacturing techniques, wearable and implantable TENGs have evolved into playing important roles in clinic and daily life from in vitro to in vivo. These flexible and light membrane‐like devices have the potential to be a new power supply or sensor element, to meet the special requirements for portable electronics, promoting innovation in electronic devices. In this review, the recent advances in wearable and implantable TENGs as sustainable power sources or self‐powered sensors are reviewed. In addition, the remaining challenges and future possible improvements of wearable and implantable TENG‐based self‐powered systems are discussed.     

Powering Implantable and Ingestible Electronics

Implantable and ingestible biomedical electronic devices can be useful tools for detecting physiological and pathophysiological signals, and providing treatments that cannot be done externally. However, one major challenge in the development of these devices is the limited lifetime of their power sources. The state-of-the-art of powering technologies for implantable and ingestible electronics is reviewed here. The structure and power requirements of implantable and ingestible biomedical electronics are described to guide the development of powering technologies. These powering technologies include novel batteries that can be used as both power sources and for energy storage, devices that can harvest energy from the human body, and devices that can receive and operate with energy transferred from exogenous sources. Furthermore, potential sources of mechanical, chemical, and electromagnetic energy present around common target locations of implantable and ingestible electronics are thoroughly analyzed; energy harvesting and transfer methods befitting each energy source are also discussed. Developing power sources that are safe, compact, and have high volumetric energy densities is essential for realizing long-term in-body biomedical electronics and for enabling a new era of personalized healthcare.     

A Modular Expandable Implantable Temperature Biotelemeter

An implantable biotelemetry system is described for multisite temperature measurements with ease of expansion by use of different master circuit boards to accommodate additional channels. Modular construction of the multichannel FM-FM system allows addition or deletion of channels as the experiment requires. The radio frequency carrer osciUlator is tunable to a "quiet" frequency in the 90-105 MHz range prior to implantation. The telemeter may incorporate enclosed or remote temperature probes which allow deep body temperature measurements in the range of 30-42 °C with an available resolution of ±0.015°C. Transmitters have been utilized in monitoring ovarian and subcutaneous temperatures, and also as an aid in detection of ovulation in the Macaca mulatta.     

The Packaging of Implantable Integrated Sensors

Integrated sensors are being designed for long-term implantation for physiological research using animal models and for permanent implantation for various types of prostheses in clinical applications. The problem of packaging these implantable integrated sensors outside of hermetically sealed hybrid packages is described. The electrolytic corrosion of cable conductors and integrated circuit metallizations is the principal danger. The published performance of the materials which have been used to date to encapsulate nonintegrated sensors and conductors is evaluated, and found to be unreliable for these applications. So, too, are the metals which have been used as electrical conductors. New techniques being developed in the attempt to achieve "hermeticity on a chip" are described. Finally, a critical, residual aspect of the overall problem is identified: how to make a mechanically rugged and inherently noncorrodible connection between a cable and a thin film on a silicon chip. No solution to this problem has been demonstrated.     

Porous Cathodes for Implantable Hybrid Cells

The in vivo power output of implantable power sources using porous platinum- or palladium-black cathodes is approximately four to five times greater than ones using commercially available cathodes of platinum black dispersed in Teflon. Porous electrodes produce a much lower foreign-body reaction than electrodes with plastic binders. Comparison of BET surface-area measurements for the powders and compacted electrodes illustrate that there is an approximate 20-percent decrease in surface area following compaction. The particle size, distribution, and shape of the powders were studied with the aid of scanning electromicrographs. In vitro galvanostatic measurements were made on the implantable power sources to study the electrochemical activity before implantation.     

Implantable Electric-Field Probes?Some Performance Characteristics

Performance characteristics of three implantable triaxial field probes for measuring intensities of the internal electric fields in biological tissues at radio frequencies are given. The sensitivity in air between 100 MHz and 3 GHz, and in phantom materials at 350, 915, and 2450 MHz, are given for the Holaday model IME-01, EIT model 979, and Narda model 2608 implantable probes, as well as their noise and modulation characteristics.     

An Implantable CMOS Amplifier for Nerve Signals

In this paper, a low noise high gain CMOS amplifier for minute nerve signals is presented. The amplifier is constructed in a fully differential topology to maximize noise rejection. By using a mixture of weak- and strong inversion transistors, optimal noise suppression in the amplifier is achieved. A continuous-time current-steering offset-compensation technique is utilized in order to minimize the noise contribution and to minimize dynamic impact on the amplifier input nodes. The method for signal recovery from noisy nerve signals is presented. A prototype amplifier is realized in a standard digital 0.5 m CMOS single poly, n-well process. The prototype amplifier features a gain of 80 dB over a 10 kHz bandwidth, a CMRR of more than 87 dB and a PSRR greater than 84 dB. The equivalent input referred noise in the bandwidth of interest is 4.8 nV/ . The amplifier power consumption is 275 W, drawn from a power supply; V _DD = –V _SS = 1.5 V.     

A Chip for an Implantable Neural Stimulator

This paper describes a chip for a multichannel neural stimulator for functional electrical stimulation (FES). The purpose of FES is to restore muscular control in disabled patients. The chip performs all the signal processing required in an implanted neural stimulator. The power and digital data transmission to the stimulator passes through a 5 MHz inductive link. From the signals transmitted to the stimulator, the chip is able to generate charge-balanced current pulses with a controllable length up to 256 s and an amplitude up to 2 mA, for stimulation of nerve fibers. The quiescent current consumption of the chip is approx. 650 A at supply voltages of 6–12 V, and its size is 3.9×3.5 mm². It has 4 output channels for use in a multipolar cuff electrode.     

An Implantable Blood Pressure and Flow Transmitter

A miniature totally implantable FM/FM telemetry system has been developed to simultaneously measure blood pressure and blood flow, thus providing an appreciation of the hemodynamics of the circulation to the entire body or to a particular organ. Developed for work with animal subjects, the telemetry system's transmission time is controlled by an RF signal that permits an operating life of several months.     

Design and Implementation of an Implantable Goniometer

A design for an implantable goniometer is presented with potential application in control of neural prostheses. Joint angle is detected magnetically utilizing a linear Hall-effect device and two permanent magnets. The transducer was evaluated in bench tests to determine its response along three orthogonal axes. A preliminary version of the system was then evaluated on a dog cadaver limb. An improved version was bench tested on a plastic model of the human knee. Finally, a fully implantable unit with transcutaneous transmission of power and joint angle information was evaluated in a chronic dog. Silicone elastomers and surface primers, used in the implant packaging, provide biocompatibility and protection against corrosion. While long-term performance studies remain to be done with respect to implanted calibration and drift, the results from this study demonstrate the feasibility of a chronic implanted goniometer system.     

Implantable defibrillator with high-output pacing function afterdefibrillation

An experimental implantable defibrillator with a temporary pacing function was developed. The pacing function was activated after defibrillation to work as a high-output ventricular-demand pacemaker. The developed system was tested in animal experiments involving anesthesized and mechanically ventilated mongrel dogs. In the animal experiments, fibrillation was electrically induced, and the automatic defibrillation and pacing function were confirmed. After defibrillation, it was possible to continue the fixed-rate pacing for more than three minutes