Long-term follow-up of pacemaker lead systems: establishment of standards of quality

The functional details of all 5,405 pacemaker leads implanted on Montefiore Medical Center were contemporaneously recorded between 1960 and May 31, 1993. Some models have been observed for as long as 24 years. Ventricular leads with more than 50 and atrial leads with more than 30 implanted units have been continually and repeatedly subjected to actuarial cumulative survival rate (CSR) analysis during which clinical decisions, such as continued lead implantation, cessation of use, or early withdrawal from service, were made. CSR evaluation for many lead models by the Mantel-Haenszel method allowed comparison of the performance of contemporaneous lead models with older and new technologies. No effect on lead longevity, durability, on mode of end of lead service, lead removal independent of function (e.g., for infection), materials, or physiological failure was found due to an operator or anatomical route of venous access. Multifilar silicone rubber insulated leads have longevity (CSR) superior to monofilar silicone rubber leads. The cumulative survival of silicone rubber insulated monofilar models 6901, 6907, continuous lead (CL), 4 mm, and 2 mm was 79%-91%, 20 years after implantation. Multifilar silicone rubber insulated models 6961 and 4116 had a cumulative survival of 99%-100%, 15 years after implantation. Among multifilar polyurethane insulated leads, distinct longevity differences exist between formulations and contemporaneous models that are normally similar, yielding a bimodal longevity distinction; model 6971 (ventricular) has 95% CSR and 6991U (atrial) has 94% CSR, 10 years after implantation. Both performed less well than other contemporaneous models, which approximate 100% CSR. The 10-year CSR for leads implanted between 1960-1975 (Era 1) is 98.7%, and the 10-year CSR of leads implanted between 1981-1985 (Era 3) is 99.4%. Comparison of individual lead models, and all leads of specific eras, allows development of survival expectations and standards of quality for comparison between contemporaneous lead models and different eras of manufacture. As the highest available lead CSR sets the standard, statistical deviation of a model from the best performance of a specific era should be considered as an indication of reduced quality.