Rate modulation by arm movements of the respiratory dependent rate responsive pacemaker

The rate response to arm movements of the respiratory dependent rate responsive pacemaker (RDP3, Biotec) was assessed in four patients implanted with this pacemaker. The pacemaker was implanted in the left prepectoral region and the auxiliary impedance measuring electrode positioned subcutaneously over the right second intercostal space with its tip lateral to the mid-clavicular line. The lower rate of the pacemaker was programmed to 75 bpm. While holding the breath, swinging arm movements (30 times) resulted in rate acceleration. The peak rate was faster when the arm on the side of the auxiliary electrode was swung (mean +/- SEM, 117 +/- 8 compared to 130 +/- 5 bpm, P less than 0.5). The mean rate response of the subjects to brief treadmill exercise (Bruce stage I) performed with both hands holding the support rails, swinging the right arm only, swinging left arm only and swinging both arms were 108, 140, 135 and 128 bpm respectively. Impedance measurement confirmed the significant influence of arm movements on thoracic "impedance" changes, which was mainly caused by electrode motion artifacts affecting the two electrode measuring system. This effect was dependent on the relative positions of the impedance measuring electrodes (i.e., between the pacemaker casing the auxiliary lead). Subsequently the auxiliary lead of the respiratory pacemaker (MB-1, and Biorate) was implanted in the lower part of the chest on the right sternal edge in another patient. Rate acceleration was only observed when the arm on the side of the pacemaker was swung. As arm movements often accompany physical activities, pacing rate can be affected and should be considered when programming this pacemaker.