Screening of solid and porous materials for pacemaker electrodes.

Several different materials, including one which was porous, were studied to assess their properties as pacemaker electrode tips. Leads were implanted in sheep for periods up to one year. Electrical measurements were made during the implant period and histopathological examination performed after sacrifice. Although titanium vapor-deposited carbon, and silver did not lower the chronic stimulation threshold below that of platinum, their electrical characteristics were within generally acceptable limits. Zinc evoked a severe tissue reactions and a high threshold. Porous titanium alloy electrodes demonstrated reduced dislodgement, more frequent attachment and a lower sensing impedance than other electrodes.