Interference voltage and interference threshold in pacemakers with unipolar and bipolar electrodes

This paper presents the coupling-model between low frequency magnetic fields and the induced voltage at the sensing input of the pacemaker (PMK) with unipolar and bipolar electrodes. For this purpose an analytical model has been developed, allowing the determination of induced voltage into a pacemaker in a magnetic field with low frequencies between 10 Hz and 30 kHz. Furthermore the electric conductivity of the surrounding tissue and the different positions of the bipolar electrode were taken into consideration. In that regard, measurements were carried out to investigate the induced voltage in bipolar and unipolar electrodes as well as interference thresholds. A comparison between the interference resistance of real pacemakers with unipolar and bipolar electrodes and the induced voltage in these electrodes are going to be presented in this paper. The extensively discussed safety factor of bipolar electrodes can therefore be calculated with the above-mentioned findings.