Catheter-type defibrillation electrode using glassy carbon: results of electrode implantation

The implantable defibrillator, developed by Dr Michel Mirowski, is a remarkable electric therapeutic device which has been in clinical use since 1980 in the treatment of life-threatening arrhythmia. However, as the present life span of this device is only 3 years, research is being carried on to extend the lifetime with improved stimulation methods, circuits and electrodes. In particular, the electrode system which is inserted into the right ventricle has more than 50 times the electrode area of a pacing electrode and is prone to degradation. What is needed is biocompatibility and electrical stability, similar to that of cardiac pacemaker electrodes, which can be used for more than 10 years. For this purpose, we focused on a conductive ceramic as a new material for the defibrillation electrode instead of the previously-used metal. We selected glassy carbon as our electrode material and tested the surface condition through acute and chronic animal experiments. No clots formed around the electrodes after a 3-month implantation, nor were there surface disorders after the defibrillation stimulations. We concluded that glassy carbon is a promising material for future defibrillation electrodes.