Pacemaker leads.

Present day pacemaker leads are far superior in every respect to those of the past. Modification of fixation characteristics has reduced displacement rates to 1% or less in most centers. Fracture of multifilar leads is a rarity. Biodegradation of polyurethane insulation appears to be an isolated problem specific to individual lead models and may be related to physical stresses incurred during manufacture or lead insertion. Recent evidence has incriminated an interaction of polyurethane with silver which arises from the drawn braised strand conductor substrate of those leads in which this problem has been noted. This may explain why the problem has been restricted to specific lead models of one manufacturer to date. Lack of uniformity of lead terminal size between manufacturers and even within the same manufacturer's product line continues to baffle this observer. Although past problems of lead displacement have been markedly reduced, the difficulty of removing chronic leads which have become septic appears to have worsened. Modification of existing leads to ensure that the interface between electrode tip and proximal shaft is unidiametric is essential.