Externalized conductors and electrical dysfunction in transvenous ventricular leads: Results of the Cardiac Lead Assessment Study

Background: The Cardiac Lead Assessment Study (CLAS) was a large prospective, multicenter, international postmarket surveillance study conducted at 45 sites. Objective: The purpose of CLAS was to examine the prevalence and incidence of externalized conductors and electrical dysfunction in subjects with selected St. Jude Medical defibrillator and left ventricular leads. Methods: Cinefluoroscopy was used to determine the presence of externalized conductors at enrollment and at 12-, 24-, and 36-month follow-up visits. Lead electrical measurements were collected systematically. Results: The study enrolled 2216 subjects with a total of 2847 study leads. The prevalence of externalized conductors through 36 months for Riata leads was 30.9%, Riata ST leads 12.6%, Durata leads 0.5%, and QuickSite/QuickFlex leads 4.7%. The prevalence of electrical dysfunction through 36 months for Riata was 4.0%, Riata ST 3.3%, Durata 2.4%, and QuickSite/QuickFlex 0.3%. In Riata and Riata ST leads with externalized conductors, there was a low risk of electrical dysfunction. None of the Durata or QuickSite/QuickFlex leads with externalized conductors developed electrical dysfunction. There was no evidence of an electrical short in a high-voltage shocking circuit leading to failed shock. Conclusion: A high prevalence of externalized conductors was found in Riata and Riata ST defibrillator leads, with a higher risk of externalization for 8F Riata leads than for 7F Riata ST leads. The 98% reduction in prevalence of externalized conductors in Durata leads compared to Riata/Riata ST leads confirms that the design improvements culminating in Durata leads significantly improved abrasion resistance and durability.