A 20-year study of endocardial pacing lead EMT 588. Lead durability and nature of failure

A report is presented of 1253 EMT 588 endocardial leads implanted in 1063 patients. The electrode surface area was large (47 mm2) in the 473 leads implanted during 1962-1973, and small (8-12 mm2) in the 780 leads implanted in 1974-1981. Replacement of 245 leads was necessary, in 187 cases due to lead failure and in 58 because of problems with normally functioning leads, such as infection. The highest lead failure rate occurred within the first 6 months after implantation, and was mostly caused by displacement and threshold increase. The dominating cause of late failure was lead lesion. The cumulative lead survival rates for the first and the second series were 88 and 94%, respectively after 1 year, 80 and 91% after 5 years, and 72 and 84% after 9 years. The polyethylene insulation proved to be the most vulnerable part of this lead. Insulation lesions could result in corrosion and/or fracture of the steel conductors. The chronic thresholds were largely stable.