Rate Responsive Pacing Using the TX Pacemaker
We have evaluated clinically a rate-responsive pacemaker which uses the evoked QT principle as indicator of physiological demand. This pacemaker is microprocessor-based and fully programmable noninvasibly through radiofrequency coupling to an external microcomputer. To date this system has been implanted in 15 patients. With this QT sensing pacemaker the rate response to exercise was smooth and progressive, and gradually returned the basic paced rate after termination of activity. Physiological rate responsive pacing resulted in significant improvement in exercise tolerance and a 40% increase in cardiac output when compared to fixed-rate pacing in 8 patients.
This initial experience confirms the possibility of obtaining a physiological response to exercise using a pacing system dependent only on a unipolar electrode which is independent of the problems of atrial activity and sensing. Rate responsive pacing might prove to be a useful alternative to atrial synchronous systems, particularly advantageous in those patients whose sinoatrial function is abnormal or who suffer from atrial arrhythmias.
KeywordsCardiac Output Exercise Tolerance Peak Exercise Atrial Arrhythmia Atrial Activity
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