Rate Response During Submaximal Exercise: Comparison of Three Different Sensors

Since 1983, 248 rate responsive pacemakers were implanted at our hospital. The main emphasis during clinical follow-up has to be placed on (he adjustment and control of its rate adaption, to meet the requirements of the aged patient's daily life. Repeated submaximal exercise but not extreme strain, come to the fore. Kaltenbach's step test (individually by stencils defined normal ranges of the heart rate during a 6 minute submaximal exercise and a 6 minute recovery period; age and sex dependent work load relative to body surface area) is able to mimic everyday efforts in an easy and reliable way. Nineteen patients with QT-related pacemaker, 12 patients with respiratory dependent pacemaker and 45 patients with body activity directed pm Activitrax were exercised using Kaltenbach's step test (mean wattage QT: 56 ± 14, HDP: 75 ± 29, Activitrax: 64 ± 20). Fifty-two patients performed 3 rounds. In comparison, 42 patients with DDD-pm underwent the same test (75 ± 28 Watt). The average curve [heart rate] with QT-pm settled in the normal range of the step test but was distorted. Only 42% of the patients reached normal range in ail three rounds. The mean heart rate of the RDP-group bordered on the basis of the normal range. The average curve (heart rate) of patients with Activitvax or DDD settled exactly in the desirable range. Problems with the rate response under repeated exercise did not occur either in the RDP or in the DDD group. The rate response behavior of the QT-related pm, the RDP and the Activitrax was of different quality. The Activitrax, with all its limitations as a device witb a non physioiogical sensor, came off very well; even though modifications of the programmable gradings of the rate response (thresholds) should be considered. Kaltenbach's step test is an excellent method to adjust and control rate responsive pacemaker.