March 28th, 2013
Case Report Of Durata Lead Failure Raises Fresh Concerns
A case report of a failed St. Jude Medical Durata ICD lead was published yesterday, raising suspicions that this lead may share some of the same potential failure mechanisms of its troubled predecessor, the Riata lead.
St. Jude’s ICD lead troubles date back to early case reports involving the Riata and Riata ST leads that ultimately led to FDA recall in December 2011. These leads have since been well documented to be subject both to increased electrical failures and structural breakdown of the lead as has been previously reported.
St. Jude’s Durata lead was designed as a successor to the Riata ST lead and continues to be marketed and implanted. The Durata lead shared a similar design to the predecessor Riata ST lead with the most notable difference being the addition of a outer coating made of the proprietary co-polymer Optim. This design modification has been promoted to improve abrasion resistance. It is hoped that this modification, would prevent the most prominent failure mechanism of the Riata family, inside-out abrasion and cable externalization.
St. Jude has staunchly defended the Durata lead and continues to promote its reliability. Although individual case reports and MAUDE database analysis have shown Durata failures, a pattern has not developed implicating similar failure mechanisms to the Riata family. Last month, Liu and colleagues reported favorable Durata lead survival data, although they recognized the limitations of the shorter follow up of this lead as compared to Riata and Riata ST.
Yesterday’s Heart Rhythm Journal case report from Swerdlow and colleagues at Cedars Sinai Heart Institute is the first detailed analysis of a Durata lead with inside-out abrasion leading to electrical failure. The lead, a Durata model 7121 was implanted in January 2008 and began to exhibit signs of electrical failure in July 2010. The patient initially declined operative intervention, but ultimately the lead was extracted and replaced in January 2013. There was no fluoroscopic externalization of the lead cables. Analysis of the lead after removal showed several area of insulation degradation. There were areas of visible abraded internal silicon and ETFE insulation under the distal shocking coil that resulted in electrical oversensing due to contact between the ring sensing cable and coil. In addition, several areas of degradation of the Optim outer insulation were found at sites of lead flexion. Based on detailed failure analysis, the investigators concluded that the lead failed due to inside-out abrasion of the silicon inner core of the lead. The analysis took care to exclude damage from the extraction process itself and included detailed photomicrographs in support of their conclusions.
The cardiac electrophysiology community has watched carefully for any signals that the Durata lead may exhibit failure similar to its predecessors. Last summer, a single case report of a Durata failure with lead externalization resulted in a 6% stock drop, as Wall Street reacted harshly to the news. That lead was later analyzed by St. Jude and reported in an investor press release to have failed due to outside-in abrasion from contact with another ICD lead. Last fall a study from scientists at rival Medtronic and University of Minnesota questioned the long-term biostability of Optim insulation in the body environment. More negative attention came this past winter as an FDA warning letter was released arising from inspections at the Durata manufacturing facility.
This most recent ICD lead failure suggests that the Durata lead can fail in a manner similar to the recalled Riata and Riata ST leads. The fundamental problem of inside-out abrasion does not appear to be fully prevented by Optim insulation. This is a failure mechanism predictable based on the design of the lead, but not reported until now. St. Jude has not yet commented publically on this most recent lead failure. All eyes will be watching to see if this is an isolated event or an early sign of systemic trouble for this lead.