Pacing systems

M. MAYOS, A. SCHUMM, C. SOORS, O. VAILHEN, E. FLEUET Application of the PACE system to the analysis of multitechnique NDT data on a power plant component -Review of Progress in QNDE, vol. 16B, eds. D. Thompson and D.E. Chimenti, Plenum, 1997, pp. 2175-2182. 

There are two types of process equipment to feed hypochlorite solution (a) basic system and (b) complex systems. Both basic and complex systems are electrically and hydraulically activated. The basic liquid hypochlorination systems include two metering pumps (one serving as a standby), a solution tank, diffuser, and appropriate quantities of tubing. The more complex system adds a diffuser corporation cock, antisiphon backflow preventer, a safety housing enclosure, a flow pacing system, and a flow meter and signal. 

A woman with congenital heart disease and atrial and ventricular arrhythmias managed by an implanted cardioverter defibrillator, epicardial pacing and amiodarone 400 mg daily, experienced deterioration in the control of her condition. She developed palpitations and experienced a shock from the defibrillator. Her amiodarone serum levels were 40% lower than 2 months previously, and her A-desethylamiodarone levels were undetectable. It was noted that 5 weeks earlier rifampicin 600 mg daily had been started to treat an infection of the pacing system. The amiodarone dose was doubled, but the palpitations continued. Amiodarone and A-desethy-lamiodarone levels increased after rifampicin was discontinued. Rifampicin is a potent enzyme inducer and it may have increased the metabolism and clearance of amiodarone. This case suggests that combined use of amiodarone and rifampicin should be well monitored. 

Flow lines and series systems can be divided up into two broad classes, based on their influence on the worker paced and unpaced. In a paced system the time allowed to perform a task is limited and once this time is up the job or customer can no longer be worked on, so it is possible that the task may not be completed. In an unpaced system there is no maximum time limit imposed on the time for the worker to perform the task. 

Paced systems lose throughput because of the incomplete processing of jobs or customers, while unpaced systems lose throughput because of the variability of task times. 

In a paced system, the tolerance time, t, the maximum time available to perform the tasks at any workstation, is set. Thus if T, the time required by the worker at station i to perform their required tasks, exceeds t, the tasks will be incomplete and defective products will result. Hence the probability Q t) that a product will not contain any defects is... 

One of the managerial controls in a paced system is the tolerance time t, which is related to the line... 

Neuronal pacing systems were used to detect and prevent epileptic seizures. 

This chapter discusses in further detail the components of the modern pacing system and the significant evolution that has occurred since its inception. The emphasis here is on system operation an in-depth discussion of the fundamental electrophysiology of tissue stimulation can be found in Ellenbogen et al. (2007). 

FIGURE 11.1 A pacing system comprises a programmer, pulse generator, and lead. 

FIGURE 11.9 Illustration of a dual-chamber pacing system. 

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. 

Figi 1.43 Contrast venography of both subclavian veins in a patient with superior vena cava syndrome. He carried a monocatheter pacing system on the left (implanted 4 years earlier) and had two abandoned leads on the right (the pacemaker, implanted 21 years earlier, had been removed from the right pocket due to local infection). Subocclusive obstruction between the right subclavian and innominate veins (a). Total obstruction is visible in the first tract of the superior vena cava arrow). Occlusive obstruction visible in the middle tract of the left subclavian vein h) arrow)... 

Klug D, Wallet F, Kacet S et al (2005) Detailed bacterio-logic tests to identify the origin of transvenous pacing system infections indicate a high prevalence of multiple organisms. Am Heart J 149 322-328... 

TLE without reimplantation Temporary PM, vacuum drainage, and arterial line (if still present) are removed the day after the procedure and the patient is completely mobilized. Chest X-ray is planned to confirm radiological success of the procedure and identify possible occult complications (i.e., pleural effusion, pulmonary embolism, mild pneumothorax). Discharge is feasible after 48 h if infective problems or other complications do not emerge. Sometimes, it is necessary to remove a PM from one side while another pacing system is present contralaterally. In such cases, the temporary PM is usually removed at the end of the procedure and the maintained system is checked before discharge, especially in case of complex procedures, in order to exclude a post extraction malfunction. 

Fig 7.1 Posteroanterior a) and laterolateral (b) chest radiograph of a man referred for lead-related endocarditis. The patient has a dual chamber pacing system in the right pectoral region and three additional abandoned leads, for a total of two atrial and three ventricular leads... 

Fig. 7.2 Serial anteroposterior fluoroscopic images taken during transvenous removal of a left-sided dual-chamber implantable cardioverter-defibrillator (ICD) system. After placement of a temporary right-ventricular (RV) pacing system

Pacing system related infection of a previously noninfected site... 

Support of this research was provided under the Generic Technology component of the Industry Research and Development Act 1986 (Australia), in conjunction with Telectronics Pacing Systems, Terumo (Australia) Ltd., and Cyanamid Australia Pty. Ltd. We thank Donna McIntosh, Edith Cheong, Kate Noble, and Vicki Tatarinoff for technical assistance. 

Granato, P A. and Franz, M. R. (1990) Use of the Gen-Probe PACE system for the detection of Neisseria gonorrhoeae in urogenital samples. Diag Microbiol. Infect. Dis. 13,217-221... 

Tyers, G. F. O., Mills, P., Clark, J., Cheesman, M., Yeung-Lai-Wah, J. A., and Brownlee, R. R., Bipolar leads for use with permanently implantable cardiac pacing systems A review of limitations of traditional and coaxial configurations and the development and testing of new conductor, insulation and electrode designs, /. Invest. Surg., 1997 10(1-2) 1-15. 

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). 

Fig. 1.9 Atrial and ventricular electrograms (EGM) as obtained through a Medtronic Pacing System Analyser Model 5311. Ventricular. Above A typical rS configuration with a minor current of injury pattern. Below The current of injury pattern is more pronounced. Atrial Above A typical rS pattern. Below Approximately 150ms after the atrial electrogram lies a large far-field ventricular electrogram.

Sensing of intracardiac electrograms. With its broad inter-electrode distance, the unipolar system sees more of the heart in which to detect a spontaneous intracardiac electrical event and thus it was assumed that unipolar was superior to bipolar sensing. In reality, the modem unipolar and bipolar pacing systems show comparable and usually excellent atrial and ventricular electrogram amplitudes and slew rates which usually exceed the standard limits of the sensing circuit by a comfortable margin. 

Skeletal muscle myopotential over-sensing. Unipolar pacing systems are far more susceptible to skeletal myopotential sensing and consequent inhibition than are bipolar systems. Such inhibition represents the most common source of unipolar over-sensing (5) particularly in the atrium, because of the necessity to use high sensitivity settings. 

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