Rate Modulation by Arm Movements of the Respiratory Dependent Rate Responsive Pacemaker CHU-PAK LAU, DON RITCHE,* GHAZWAN S. BUTROUS, DAVID E. WARD, and A. JOHN CAMM From the Department of Cardiological Sciences, St. George's Hospital Medical School, Blackshaw Road, London SW17 ORE, United Kingdom LAU, C-P, ET AL.: Rate modulation by arm movements of the respriratory-dependent rate responsive pacemaker. The rate response to arm movements o/(he respiratory dependent rate responsive pacemaker {RDP3, Biotec) was assessed in four patients implanted with this pacemaker. The pacemaker was impJanted in the left prepectoraJ region and the auxiliary impedance measuring electrode positioned subcutaneousiy over the right second intercostal space with its tip lateral to the mid-ciavicular 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 /aster when the arm on the side of the auxiliary electrode was swung (mean ± SEM, 117 ±8 compared to 130 ±5 bpm, P < 0.5). The mean rate response of the subjects to brie/treadmill exercise (Bruce stage 1) 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 respec- tively. Impedance measurement confirmed the significant influence of arm movements on thoracic "im- pedance" 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 elec- trodes (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. (PACE, Vol. 11, June 1988] rate responsive pacemaker, respiratory sensing, thoracic impedance Introduction Rossi et al.^ have shown that the change in respiratory rate during exercise is significantly related to the change in heart rate. Futhermore it has also been suggested that this relation is valid in patients with lung diseases,^ The sensing of re- spiratory changes during exercise has been uti- lized in the construction of rate responsive pace- makers.^'^ "Principal Physics Technician, Department of Medical Phys- ics, St. George's Hospital Address for reprints: Chu-pak Lau. MB. Department of Car- diological Sciences. St. George's Hospital Medical School, Blackshaw Road, London SW17 ORE. United Kingdom. Received July 13. 1987; accepted August 25, 1987, The respiratory dependent rate responsive pacemaker (RDP3, MB-1, Biorate, Biotec, Interna- tional, Bologna, Italy) measures respiratory rate by means of an auxiliary lead implanted subcuta- neousiy across the chest. Thoracic impedance is measured by a bipolar electrode configuration, using the pacemaker casing as the active elec- trode and the auxiliary lead as the passive elec- trode.^ Respiratory movement above a program- mable level is detected and the sensed respiratory rate is converted into a pacing rate by a program- mable slope of rate response. The MB-1 is similar to the RDP3 but offers more basic pacemaker pro- grammable features and some telemetry func- tions. Satisfactory rate responses have been claimed, although most of the studies used leg exercises as a means of 744 June 1988 PACE, Vol, 11