[Heart rate changes in a new generation of activity controlled pacemakers during stair climbing]

A study was undertaken to determine whether a new generation of accelerometer controlled rate adaptive pacemakers has advantages over the older type of activity controlled pacemaker.

Pacemaker rates of 21 patients (15 women, six men; mean age 64.1 [44-85] years) with the new pacemakers were compared with those of a control group of patients free of cardiac disease (four women, six men; mean age 50.5 [39-75] years) in whom a vibration controlled pacemaker system had been attached to the right pectoral area. Heart rate was monitored by a rate analyser, data recorder and rate watch throughout the period of activity. Step frequencies of 92, 108 and 120 steps/min were fixed by metronome.

The new pacemaker responded with a rate increase at a step rate of 92/min (P < 0.001): from 106.6 +/- 7.9 beats/min on walking on the even, to 123 +/- 8.4 beats/min on stair climbing. There was a significant fall in frequency, to 105 +/- 11.7 beats/min, when descending steps. The conventional pacemakers responded with a decrease in frequency on stair climbing (97.2 +/- 8.7 beats/min compared with 112.6 +/- 7.4 when descending).

The results indicate that the new system provides for a more physiological rate response. However, this difference between the older and the new generation of pacemakers is less marked on walking at higher step rates.