Abstract
This paper describes several discussions about detection impedance of the endocardial electrodes related to the surface areas in order to evaluate the sensing function of cardiac pacemakers.
The conclusions reached are as follows :
(1) Detection impedance of the electrodes-meaning the electrode impedance when the electrodes are used to pick up the signals induced-were found to be approximately in inverse proportion to their surface areas. Polarization impedance became predominant under increasing detection impedance as the surface area became smaller. Therefore, reduction of electrode polarization is most effective to decrease the detection impedance, which would pose serious sensing problems for the pacemakers if conducted with such small electrodes.
(2) Detection impedance of the electrodes went down day by day during a few days after electrode implantation; it then increased gradually until the electrodes reached their own stable states.
This seems to be a safe side variation for pacemaker sensing because the decrease of detection impedance may compensate for the reduction of QRS amplitude that transitorily appears immediately after electrode implantation.
