A new study has found that deaths associated with Riata and Riata ST Silicone Endocardial Leads is due to short-circuiting between high voltage components caused by insulation defects, not due to externalized conductors as previously thought.
The Riata and Riata ST leads connect an implantable cardioverter defibrillator (lCD) or cardiac resynchronization therapy defibrillator (CRT-D) to cardiac tissue in order to monitor and regulate a patient’s heart rate by providing pacing and delivery of high voltage therapy for ventricular arrhythmias.
St. Jude Medical, manufacturer of the Riata leads, estimates that 79,000 patients in the United States currently have this defective medical device. Patients may have received a Riata model lead in pacemaker procedures from June 2001 to December 31, 2010.
The study entitled Deaths Caused By the Failure of Riata and Riata ST Implantable Cardioverter-Defibrillator Leads appears in HeartRhythm, the official journal of the Heart Rhythm Society. The Minneapolis Heart Foundation and Abbott Northwestern Hospital Foundation funded the study.
In February 2012, Dr. Robert G. Hauser and colleagues from the Minneapolis Heart Institute Foundation searched the U.S. Food and Drug Administration’s (FDA) Manufacturer and User Facility Device Experience (MAUDE) database for deaths associated with the Riata, Riata ST and a competitor’s lead called the Quattro Secure. According to the published study, they found 22 deaths caused by Riata or Riata ST lead failure, typically by short-circuits between high voltage components. There were five deaths associated with the Quattro Secure.
Riata leads are known to have an increased rate of premature abrasion of the silicone insulation covering the leads that can cause the wires to protrude from their protective coating. St. Jude Medical and the U.S. Food and Drug Administration have previously warned that where this insulation abrasion also causes exposure of the conductors, they may not work as intended and the malfunction could result in serious adverse events, including death. Data shows 15% of Riata leads with insulation abrasion also exhibit externalized conductors.
In December 2010, St. Jude Medical notified doctors in a letter that increased rates of Riata lead abrasion could result in under-sensing and failure of the lead to deliver high voltage therapy when needed, inability to deliver the therapy, or over-sensing and initiating therapy when not needed if conductors become externalized and come in contact with other leads or devices. The company said it was “completing the planned phase-out of all models of Riata and Riata ST silicone leads by December 31, 2010” due to the silicone insulation abrasion problems and development of a new, improved lead insulation.
St. Jude Medical sent a letter by certified mail as an update in November of 2011, updating doctors of failure rates associated with lead insulation abrasion and included new patient monitoring recommendations and mitigation instructions.
While St. Jude Medical considered the letter a “voluntary medical device advisory,” the FDA classified the action as a Class I Recall of the Riata, the most serious type of recall saved for situations in which there is a reasonable probability that use of the products will cause serious adverse health consequences or death.
Dr. Hauser and his colleagues concluded from their study that the Riata and Riata ST leads were prone to high voltage failures, surprisingly they found that external conductors were not a factor in Riata lead related deaths. Instead, they found that insulation defects caused the breakdown of the insulation and resulted in short-circuiting between high-voltage components.
“As the manuscript noted, the MAUDE database often contains incomplete reports that do not fully reflect the conclusions following testing and review of the reported device malfunction,” St. Jude Medical said in response to the study. “Given this understanding of the lack of information and reliability of the MAUDE database, it is not surprising that the manuscript published this week is not entirely accurate. We were not asked to review the information the author found in the MAUDE database prior to publication.”
The manufacturer contends that Riata lead failures are the result of abrasion of silicone leads, that this is a known risk documented in the literature and that the Riata failure rates are comparable to failure rates of other silicone leads in the industry.
St. Jude Medical is conducting a 500 patient Riata Lead Evaluation study to investigate the electrical failures associated with the device.
According to The New York Times, Dr. Hauser also found that eight patients have died during procedures to remove their Riata lead.