Insulation Failure in St. Jude Riata Leads

A recent study evaluated the Manufacturer and User Facility Device Experience (MAUDE) database, which contains reports of adverse events involving medical devices6,9. The FDA updates the database every two months. A total of 107 Riata leads with reported inside-out insulation breaks were found, of which 105 were available for analysis. The average age of the leads was 62.1+/-18.6 months. A total of 226 insulation defects were found with 143 inside-out insulation abrasions. Twenty-eight of the 105 leads (26.7%) had inside-out insulation defects underneath one or more of the high voltage-shocking coil. Of these, 23 were 8F and five were 7F Riata ST leads. Exposed cables or conductors were present in 32 leads and six leads had melted cables, presumably due to one or more high voltage shocks. 22 of the 43 leads assessed (51.2%) also had abraded ETFE cable coating exposing the conductor. Noise and other sensing issues were the most common signs of failure. Seven leads were found to have externalized cables and five exhibited electrical abnormalities. 31 patients (29.5%) experienced inappropriate shocks of which 41% had abraded cables. A critical decision facing physicians is how to screen and manage patients who are found to have externalized cables. Externalized cables on fluoroscopy may precede any electrical abnormalities. Also noise may not be detected on all ICD models. A recent case report suggested that changes in lead parameters might be transient and may be missed. The lead may function normally as the high-voltage and pace-sense cables are covered with ETFE, which serves as the second insulating barrier. As this is a very thin layer (0.0015 inches) the reliability of this to withstand a high-energy shock is unknown. This may lead to failure of appropriate therapy for life threatening arrhythmias. The aim of this study is to screen patients with ICD leads that potentially could have multiple different failure mechanisms, including inside-out insulation breaks, to develop a novel new algorithm and methods to detect these defects, thereby enabling physicians to prevent complications from failure of these leads. It is hypothesized that current monitoring tools are insufficient for detecting the sometimes transient electrical failures of the Riata family of leads, and that additional device diagnostic information in combination with fluoroscopy may improve detection of electrical failures.