The sensing and pacing performance of pacemaker electrodes is characterized by the electrochemical properties of the electrodes/tissue layer; the usually smooth metallic electrode surface results in a high pass filter characteristic. Consequently, the detected intracardiac signals, which control the implantable systems, are not optimally matched to the spectral contents of the depolarisation signal. To avoid interference caused by noise (EMI, muscle potentials, etc.) a shift of the frequency of the band pass towards the lower frequency spectrum is required. As previously reported, the electrochemical properties of sintered and surface-treated electrodes prove the predicted improvement of sensing performance if titanium-nitride coated electrodes are used. Our results demonstrate their superiority above all the other electrodes presently known. The advantages can be referred to the micro-crystalline surface structure achieved by sputter-deposited electrode coatings and the kinetics of the ionic exchange. Furthermore, the acute thresholds achieved with the TiN-systems were significantly better than those of the smooth metallic surface. These results were also confirmed for chronic implants and are attributable to the known biocompatibility of titanium and its alloys.

Electrocardiography↗

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[Motion energy as a control variable for adapting stimulation frequency].

An activity sensing rate-responsive pacing system is presented which adaptively controls heart rate to adjust cardiac output in response to increased metabolic demand, and more optimally restore homeostasis of the intact cardiovascular system. The current use of ventricular demand and DDD universal pacing systems, although rate and multi-parameter and multi-function programmable, are fixed at these programmed settings. These devices are adequate for patients at rest or during moderate exertion, but are suboptimal for physically active patients whose physiology requires increased oxygen supply to meet an increased cardiac demand. In the past, these patients may have experienced fatigue or dyspnea out of proportion to their cardiovascular disease. The Ergos rate-adaptive single- and dual-chamber pacing system is a second generation pulse generator which is rate responsive to a patient's increased physiologic demand by sensing a motion signal which reflects increased work load and the need for a compensating increase in heart rate. Ergos offers increased assistance to patients with sinus bradycardia who may require the rate-responsiveness with the additional advantage of AV synchrony. Clinical results show the effectiveness of the presented sensor control by motion energy for rate adaptive pacing therapy.

Cardiac Output↗

PubMedDate not supplied

[Measuring intracardiac impedance for determining sympathetic nerve activity in frequency-adjustment electrostimulation--1: Biomedical technical principles].

Modern Pacemaker technology makes it possible to adapt the pacing rate to hemodynamic requirements. The most ambitious approach aims at restoring the physiological closed-loop system by utilizing the information supplied by the Autonomic Nervous System and extracted from myocardial contractile performance. Measurement is accomplished by the impedance method using the stimulating electrode as the measuring electrode. The Ventricular Inotropic Parameter (VIP) has been identified as an ANS-dependent parameter. A special detection algorithm, the Regional Effective Slope Quantity (RQ), with a high ANS sensitivity has been developed specially for the purpose. Rate adaptation is achieved by using an individually-adjustable Inotropic Index (II). The concept has been evaluated in a multicenter study employing a standardized exercise protocol. The clinical results will be presented in Part 2 of this paper.

Algorithms↗