High incidence of isolator fractures in transvenous implantation of cardioverter defibrillators

With the growing complexity of transvenous ICD-lead systems the incidence of lead complications might increase in comparison to usual pacemaker leads. The incidence of insulation defects of transvenous leads was determined during a mean follow-up time of 23.8 +/- 10.9 months. Among 130 transvenous ICD-patients, eight insulation-breaks in seven patients (6%) could be identified after a mean follow-up of 28 +/- 13 months. After a follow-up period of 12 months no lead defect was identified, after 24 months 96.3 +/- 1.8% of all transvenous leads were free of complications, after 36 months 87.9 +/- 6% and after 48 months in 61.2 +/- 18.7% of all leads no isolator fracture was found. In seven cases an operative revision was required. All insulation-defects were exclusively found in abdominally implanted silicone lead-systems type Endotak/CPI (Cardiac Pacemakers, Inc., USA): isolator fractures occurred in 12% of all Endotak leads used, 19% of the Endotak C models 62, 64, 72 and 74 were affected. In none of 66 implanted Transvene lead systems (Medtronic, Inc., USA) were isolator defects found. In six patients the proximal part of the sensing lead near the device was affected. All of these patients experienced potentially harmful repetitive device discharges. In one patient during elective ICD-replacement an isolation break of the proximal shock electrode was found, in another patient between the proximal and distal shock-electrode. Despite regular follow-ups with impedance-measurements, only in one case was the insulation break foreseeable. Stored electrograms were helpful to disclose insulation defects. With increasing age of the transvenous lead systems a growing number of insulation defects has to be expected. Especially the isolators of the first Endotak C models 60-74 seem to create major problems with increasing age.