© 2002 by European Society of Cardiology
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Rate-adaptive pacing using intracardiac impedance shows no evidence for positive feedback during dobutamine stress test
1Department of Pharmacology and Toxicology, Medical Faculty, University of Technology Dresden, Germany; 2Department of Internal Medicine, St. George's Hospital Leipzig, Germany; 3Department of Biomedical Engineering, Friedrich-Alexander-University Erlangen-Nürnberg, Germany
BACKGROUND: The Inos2 DDDR pacemaker senses unipolar intracardiac impedance signals for adapting heart rate to meet the haemodynamic needs of physical activity. Theoretically, such pacing devices could be limited by positive feedback since increase in beating frequency per se enhances contractility. We have addressed this problem in patients with chronotropic incompetence who were subjected to a pharmacological stress test.
METHODS AND RESULTS: Twelve patients with chronically implanted Inos2 DDDR pacemakers were studied using the standard protocol of stress echocardiography. Most of the patients reached the programmable maximum closed-loop rate during the incremental dobutamine challenge. The time courses for increase in as well as for recovery of heart rate were not different from control patients receiving routine diagnostic stress echocardiography.
CONCLUSIONS: In patients implanted with the Inos2 DDDR pacemaker acute stimulation with intravenous dobutamine leads to a robust increase in paced heart rate without any evidence of positive feedback. Copyright 2002 The European Society of Cardiology. Published by Elsevier Science Ltd. All rights reserved.
Key Words: Closed-loop stimulation, rate adaptive pacing, contractility
Correspondence: Dr med. Torsten Christ, Institut für Pharmakologie und Toxikologie, Fetscherstr. 74, D-01309 Dresden, Germany. Tel: +493514586279; Fax: +493514586315; E-mail: Christ{at}rcs.urz.tu-dresden.de
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