Robert G. Hauser, MD, the Minneapolis Heart Institute cardiologist whose previous research focused on high-voltage failures in St. Jude Medical’s Riata and Riata ST implantable cardioverter-defibrillator (ICD) leads, has identified another potential flaw: a proprietary coating designed to prevent insulation abrasion in Riata ST Optim and Durata ICD leads. The findings were published online Aug. 21 in EP Europace.
In a March study, Hauser and colleagues identified four Riata and three Riata ST deaths that were associated with can abrasions. They wrote that these defects led to short-circuits and failure to deliver therapy. In contrast, their examination of Quattro Secure ICD leads (Medtronic) linked no reported deaths to can abrasions. They observed that the Quattro leads were protected by an abrasion-resistant polyurethane covering, which prompted them to look into St. Jude’s silicone-polyurethane copolymer coating, Optim.
As in the previous study, Hauser et al used the FDA’s Manufacturers and User Device Experience (MAUDE) database, which holds reports of adverse events reported by U.S. manufacturers of medical devices and results from companies’ investigations. For the current study, the researchers performed a search on April 13 using the terms “Riata ST Optim abrasion analysis” and “Durata abrasion analysis.” They estimated lead implant as three months after the lead’s manufacturing or shipping date.
Hauser et al found 15 reports for Riata ST Optim and 37 reports for Durata leads based on investigations of returned leads for events that occurred between December 2007 and January 2012. They found that the 15 Riata ST Optim leads had been implanted on average for 29.1 months. Eight had can abrasions and three abrasions were caused by friction with another device. Four of the abrasions resulted in high-voltage failures and one death. One failure was caused by an internal insulation defect.
The 37 Durata leads had been implanted for an average of 22.2 months; 12 had can abrasions, six had abrasions caused by friction with another device, and 72 percent of those 18 leads had electrical abnormalities.
“The results of this study suggest that Optim, a proprietary copolymer of silicone and polyurethane, does not prevent critical insulation failures in Riata ST Optim and Durata leads that are caused by friction with the can or another device,” Hauser and colleagues wrote. “Of equal concern is the fact that these failures occurred in leads that had only been implanted approximately four years or less.”
The authors observed that most of the insulation incidents were outside-in abrasions, which they defined as defects caused by friction or contact with other devices or anatomic structures such as the clavicle or a rib. “The most common abrasions were those caused by friction with the pulse generator can and with another device, most likely another lead or leads,” they wrote. “However, one Riata ST Optim lead failure and three Durata lead failures were internal abrasions, which appear to be similar to the inside-out abrasions that have been reported for Riata and Riata ST leads.”
Study results may underestimate the number of lead failures because the FDA’s post-market surveillance through MAUDE relies on reporting by physicians and hospitals, Hauser et al wrote. MAUDE data also may be incomplete or have gaps. Based on their findings, the authors recommended:
- Dressing the lead in the pocket to minimize contact with the pulse generator;
- Regular follow-up combined with remote monitoring and activation of available patient alerts;
- Evaluating leads visually and with high-resolution fluoroscopy when the pulse generator needs changing;
- Assessing the potential for short circuiting by impedance measurements and a high-voltage shock;
- Returning explanted Riata ST Optim or Durata leads to the manufacturer with detailed clinical and diagnostic information as well as stored electrograms; and
- Independent data collection of lead performance to ensure patient safety.
The FDA continues to monitor Riata and Riata ST leads. The agency reported Aug. 16 that it ordered St. Jude to collect data related to potentially premature insulation failure in Riata and Riata ST leads. The FDA also recommended that physicians and hospitals use x-ray or other imaging technologies to check for insulation abnormalities in Riata and Riata St leads, but it cautioned against routine removal of the leads without careful review.