BOSTON – An independent investigation by seven U.S. centers has shown that recently recalled Riata implantable cardioverter defibrillator leads are significantly more prone to failure than are leads made by a different manufacturer.
A retrospective study of all patients older than 18 years who received ICDs with either Riata or Riata ST leads (St. Jude Medical) showed a failure rate of 1.93% per patient-year for Riata leads, significantly more than the rate of 0.43% for the comparator lead, Quattro Secure (Medtronic) (P less than .0001). The failure rate for Riata ST leads was 0.50%, a nonsignificant difference, reported Dr. Raed Abdelhadi of the Minneapolis Heart Institute.
Dr. Raed Abdelhadi
The Riata and Riata ST ICD leads are prone to inside-out and outside-in silicone insulation defects, which can cause lead malfunction and externalization (breach of the outer insulation, visible outside the lead body) of the conductor cables, but until this study, there were no independent, multicenter investigations into the rate of lead failure, failure signs, or clinical sequelae, he said.
"Without such data, it is not possible to design evidence-based management strategies or to advise Riata patients of their risks," he said at the annual meeting of the Heart Rhythm Society.
Investigators at the seven centers looked at all-cause failures and electrical malfunctions in 774 patients who received an 8-French Riata lead (mean follow-up, 4.2 years), and 307 patients who received a 7-French Riata ST lead (mean follow-up, 3.3 years). ICD leads with silicone-polyurethane copolymer insulation (RIATA ST Optim and Durata leads) were excluded.
For comparison, they obtained data on the Quattro Secure ICD leads from a three-center study of the longevity and risk factors for failure of Sprint Fidelis leads (Circulation 2011;123:358-63).
The investigators defined lead failure as either "abnormal impedance leading to replacement, electrical noise manifested by nonphysiologic signals, increase in pacing threshold or decline in R-wave amplitude necessitating lead placement, inability to provide effective therapy due to apparent lead abnormality, or externalized conductor, clearly demonstrated on fluoroscopy or x-ray ... even if the lead was functioning normally and electrically intact."
Neither functional abnormalities (for example, exit block and physiologic oversensing in the presence of an electrically intact lead) nor lead displacement (unless caused by a bad fixation mechanism) were considered to be failures.
Of the 1,081 Riata and Riata ST leads implanted, 712 (66%) were active and functioning normally at last follow-up. Of the 302 (28%) removals from service, 266 were owing to death, 10 to transplant, 5 to perforation, 4 to infection, and 17 to other causes.
In all, 10% of leads in the study were examined for externalized conductors, and 27 (25%) were found to have them. Of this group, seven (26%) leads were malfunctioning.
There were 65 Riata failures and 5 Riata ST failures, for a 6.2% incidence of all-cause failures. Of this group, 47 failures were due to electrical malfunctions, including seven from the externalized conductors contributing to the malfunction, as noted before. An additional 20 leads had externalized conductors with normal function, but met the study definition of failure.
In contrast, there were 23 lead failures among 1,668 patients with Quattro Secure leads (1.37%).
In univariate analysis, neither age, gender, primary or secondary indication for ICD implantation, ejection fraction, type of cardiac disease, nor lead placement location were significantly associated with risk for lead failure. The same was true when the Riata ST leads were subtracted from the equation.
Signs of failure included noise resulting in inappropriate therapy, elevated thresholds requiring lead replacement resulting in loss of capture and syncope, abnormal pacing impedance, abnormal high-voltage impedance, decline in R value requiring lead replacement, and failed defibrillation threshold testing with abnormal high-voltage impedance, requiring lead replacement.
Dr. Abdelhadi noted that the study was limited by its retrospective design, the fact that only 10% of leads were examined for externalized conductors, and the relatively short follow-up in the Riata ST group compared with the other two groups. In addition, most lead failures were not confirmed by returned-product analysis.
Dr. Hugh Calkins
The study confirms what was already known and what many meeting attendees expected to hear, commented Dr. Hugh Calkins, professor of cardiology at the Johns Hopkins Heart and Vascular Institute, Baltimore, and vice president of the Heart Rhythm Society, in an interview.
"The bottom line is that it’s all about the patients, and how we take care of them, advise them, and whether we explant the leads. The whole international heart rhythm community is focused on this question and what to do so that there aren’t deaths that result from noise, that there aren’t deaths from unnecessary lead extractions," he said. Dr. Calkins was not involved in the study, but he moderated a media briefing where Dr. Abdelhadi presented the data.