P2859Low rates of mechanical failures of silicone-polyurethane copolymer-coated ICD leads: 11 years prospective follow-up
Authors: Cairns J A , Balasubramanian K , Themeles E , Epstein A E , Healey J S , Connolly S J 
Published: October 2019

Abstract

Background
High rates of ICD lead mechanical failures (insulation abrasion and conductor fracture) resulted in FDA recalls and substantial design modifications. Most subsequent reports of lead failures of newer generation leads are based upon modest-sized, retrospective cohorts with relatively brief follow-up and may be unreliable. Following lead modifications (including silicone-polyurethane copolymer insulation coating), in 2007, one manufacturer established 3 prospective registries, and engaged a university-based methods center to independently review the registries, to adjudicate all reports of lead failures and to independently analyze lead survival. Up to 11 years of follow-up is now available.

Purpose
To adjudicate all reports of leads inactivated because of possible mechanical failure and to independently calculate rates of mechanical failure overall and by specific type.

Methods
Manufacturer expert staff confirm each lead inactivation by site interrogation. Following formal algorithms which incorporate lead testing and remote monitoring, they designate all-cause mechanical failure (fracture; insulation abrasion; failure at crimp, bond or weld; or uncertain) based upon the finding of electrical noise, very low or very high or rapidly rising impedance or alternatively they designate non-mechanical dysfunction (e.g. no impedance criteria but elevated thresholds, over or under sensing). The results of returned product analyses are incorporated when available (31%). The methods center receives electronic data transfers twice yearly, reviews all documentation, adjudicates all instances of possible lead failure, assigns probable cause (by 2 electrophysiologists) and conducts independent analyses of lead survival.

Results
10,866 patients (73% male, mean age 65.9 yr., LVEF 29.3%, NYHA class II or III 89%) with 11,132 leads had follow-up of 4.6 yr. (median) and 11 yr. (maximum) (Aug 31, 2018). Lead follow-up was censored at the time of lead inactivation, death/transplant or administrative withdrawal. Of leads enrolled, there were 26.6% still in follow-up and of those not the status was 7.4% inactivated, 29.5% death or transplant, 33.8% administrative withdrawal and 3.7% reason missing. Following adjudication, there were 156 all-cause mechanical failures (1.40% total, 0.29%/yr.). Rates of cause-specific mechanical failures were: fracture 1.02% total, 0.22%/yr.; insulation abrasion 0.28% total, 0.06%/yr.; miscellaneous/uncertain 0.12% total, 0.02%/yr.; and externalized conductors 0%. Life-table rates of freedom from lead failure by 11 years were: all-cause mechanical failure 95.9%, conductor fracture 97.0%, insulation abrasion 99.1%, mechanical failure other/uncertain type 99.9%, and externalized conductors 100%.

Conclusions
Up to 11 yr prospective follow-up of silicone-polyurethane-coated ICD leads with independent adjudication and analyses of events shows low rates of all-cause mechanical failure and no externalized conductors.

Acknowledgement/Funding
Abbott