Histological reactions of porous tip endocardial electrodes implanted in sheep

The tissue reaction caused by a sintered tip electrode is compared with that of a platinum-iridium tip electrode in a work which employs implantation in sheep and follow-up of the implant for up to 90 days. Clinical tests and anatomo-pathological examination of the histological sections were performed. The results show a remarkably rapid fixation to the heart for the porous electrode with formation of limited inflammatory process, a thin fibrous capsule and modest alteration of the endocardial tissue. Conversely, the platinum-iridium electrode does not fix even in long periods and therefore continuously rubs the endocardial surface. Chronic inflammation and formation of remarkably thick connective capsule results, under which the heart seems mode deeply altered.