抄録
12 dogs (12kg in average weight) were experimented by the right thoracotomy under general anesthesia. Special electrodes made of stainless steel with the tip of 0.5mm in diameter and 7mm in length were used. They have the surface area of 10mm2 Four electrodes were inserted at intervals of 5mm, 10mm and 20mm into the right atrial and the right ventricular surface respectively. Stimulation current threshold was measured both in acute (immediately after insertion) and in chronic period (3 weeks after implant) using Medtronic 5880 A. No difference of stimulation current threshold between right atrium and right ventricle was observed either in acute or in chronic period. Bipolar and unipolar electrodes did not show any significant difference. Stimulation current threshold was almost equal even though the distance between two electrodes varried from 5 to 20mm in the atrium and in the ventricle.
Stimulation current threshold between stimulation electrode and indifferent electrode was almost equal even though the surface area of the latter ranged from 10mm2 to 80mm2. Intracardiac R wave both in acute and chronic period was not affected by the distance between two electrodes, changing from 5mm to 20mm.
Position of indifferent electrodes and area of indifferent electrodes did not induce the change of R wave height either as an average.
