[Measurement and evaluation of three-dimensional acceleration signals for rate adaptation of cardiac pacemakers].

The aim of this study was to determine which of the one-dimensional acceleration signals best correlates with the heart rate under the conditions of daily activities, or whether such correlation is shown by three-dimensional acceleration signals. A commercially available biosignal system (ZAK, Germany) was used to record electrographic data and acceleration caused by body movements in the three directions vertical, sagittal and lateral. The evaluation was performed on 12 young healthy volunteers and 4 elderly volunteers with cardiovascular disorders but adequate chronotropic function. Informed consent was given by all participants. Activity signals and heart rate were recorded while walking under two different conditions. For analysis, the pathways were divided into segments with different gradients. All the acceleration signals were analysed statistically and temporally with regard to peak-to-peak value, root mean square value, and step frequency by means of cross correlation. Both statistical and temporal analysis showed that the correlation of heart rate and all one-dimensional acceleration signals and the three-dimensional acceleration signal was relatively low (r < or = 0.6). Walking uphill even showed a negative correlation between acceleration signals and heart rate. Despite the widespread use of activity-controlled pacemakers, the correlation between heart rate and acceleration signals is not satisfactory.