Impedance pacing

Ellenbogen KA, Wood MA, Gilligan DM, et al. Steroid eluting high impedance pacing leads decrease short and long term current drain Results from a multicenter clinical trial. PACE 1999 22 39 8. 

Schmidinger H, Mayer H, Kaliman J, et al. Early detection of lead complications by telemetric measurement of lead impedance. PACE 1985 8 A23-A90. 

The latter authors used anode and cathode symmetrical cells in EIS analysis in order to simplify the complication that often arises from asymmetrical half-cells so that the contributions from anode/ electrolyte and cathode/electrolyte interfaces could be isolated, and consequently, the temperature-dependences of these components could be established. This is an extension of their earlier work, in which the overall impedances of full lithium ion cells were studied and Ret was identified as the controlling factor. As Figure 68 shows, for each of the two interfaces, Ra dominates the overall impedance in the symmetrical cells as in a full lithium ion cell, indicating that, even at room temperature, the electrodic reaction kinetics at both the cathode and anode surfaces dictate the overall lithium ion chemistry. At lower temperature, this determining role of Ra becomes more pronounced, as Figure 69c shows, in which relative resistance , defined as the ratio of a certain resistance at a specific temperature to that at 20 °C, is used to compare the temperature-dependences of bulk resistance (i b), surface layer resistance Rsi), and i ct- For the convenience of comparison, the temperature-dependence of the ion conductivity measured for the bulk electrolyte is also included in Figure 69 as a benchmark. Apparently, both and Rsi vary with temperature at a similar pace to what ion conductivity adopts, as expected, but a significant deviation was observed in the temperature dependence of R below —10 °C. Thus, one... 

Impedance spectroscopy is a helpful means for studying both the bulk transport properties of a material and the electrochemical reactions on its surface. The importance of impedance spectroscopy arises from the efficacy of the methodology in separating individual reaction-migration paces into a multistep process, since each reaction or migration step has, ideally, a single time constant related with it consequently, each step can be separated in the frequency domain ... 

These models provided a quantitative relationship between physicochemical parameters and impedance response, but the application of interpretation strategies did not keep pace with the model development. Interpretation was based on graphical examination of plotted data. In simple cases, plots could be used directly as described in Chapter 18. For more complicated cases, simulations could be compared graphically to data to reveal qualitative agreement. 

The translation of RSD into Innovative new products and services is an extremely complex and inherently risky operation. To find answers to why the pace of innovation might be lagging in the U.S., it was necessary to examine the question of why companies innovate anyway, and what specific actions, or lack of action, might stimulate or impede the process. 

The most common sensor is the activity sensor, which uses any of a variety of technologies (e.g., piezoelectric crystals and accelerometers) to detect body movement. Systems using a transthoracic-impedance sensor to estimate pulmonary minute ventilation or cardiac contractility are also commercially available. Numerous other sensors (e.g., stroke volume, blood temperature or pH, oxygen saturation, and right ventricular pressure) have been researched or market-released at various times. Some systems are dual-sensor, combining the best features of each sensor in a single pacing system. 

The same can be said of infrastructure - be it transportation, energy, health care, information technology networks or communications. Taken together, the institutional policy and infrastructure environments create a national infrastructure platform that can accelerate - or impede - the pace and quality of collaborative innovation. 

This design reduces pacing impedance and the redundancy prevents pacing failure if a filar breaks. A third design is the cable. A cable conductor is obtained by two or more wires twisted together as a strand and then bundled with other strands around each other as a rope. Cable-leads have lower electrical resistance but are less prone to crush failure and smaller than coils (Fig. 1.14) [1]. 

Skalsky M, Maddison D (1985) Evaluation of a new low polarisation high impedence Pt/Ir coated porous 6 mm 2 dish electrode. Pacing Clin Electrophysiol 8 788 [abstract]... 

Whenever electricity flows across a circuit, there is a resistance to flow encountered by the electrons. For pacing systems, the resistance is determined by the complex interaction of multiple components. Because some of these components are also characterized by the ability to retain charge or capacitance, the term impedance is preferred. At the time of lead implantation, it is this complicated series of resistance and capacitance factors that are measured and are referred to as system impedance. For a pacing circuit, the system impedance has five basic components a low, purely resistive conductor impedance, a high cathode electrode impedance, complex polarization effects at the electrode-tissue interface, a low tissue impedance, and the anode electrode impedance (Fig. 1.3). 

Gatnmage MD, Swoyer J, Moes R et al. Initial experience with a new design parallel conductor, high impedance, steroid-eluting bipolar pacing lead (Abstract). PACE 1997 20 1229. 

The pacing current drain during each paced cycle is a function of output voltage, pulse width, and lead impedance. The interrelationship between these factors can be expressed by the following equations ... 

The noninvasive measuranent of lead impedance was one of the earliest uses of measured pacemaker telemetry. Following the deployment of lithium iodide it soon became clear that the pacing lead was more likely to fail than the pulse generator. In fact, lead failure has been responsible for most of the serious recalls and advisories in the pacing industry in the past 30 years (7,36,37). Therefore, it should come as no surprise that lead impedance telemetry became a valuable diagnostic tool to help with the assessment of lead integrity (38,39). 

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