January 20 2012 (Minneapolis, Minnesota) — A meeting of the minds here today aims, in part, to figure out what to do with the thousands of people in the US--about 79 000, according to St Jude Medical--who remain fitted with the company's "recalled" St Jude Medical Riata or Riata ST implantable cardioverter defibrillator (ICD) leads.
The company halted the leads' distribution in December 2010, by which time it estimates having sold about 227 000 of them worldwide over nine years. It issued a "dear doctor" cautionary letter in December 2010 and a stronger safety advisory in November 2011. Last month, the US FDA reclassified the advisory as a class I recall. The documents applied only to older Riata leads with a silicone sheath, not to a later incarnation coated in a silicone-polyurethane amalgam St Jude calls Optim.
The one-day conference, sponsored and supported by the Minnesota Heart Institute without financial help from industry, brings together a faculty of more than 20 clinician leaders in the field to tackle the real-world effects of what's been called a "unique" type of defibrillator lead failure [1].
The problem? With normal use, Riata internal conductor wires can abrade the inside of and erode through their silicone insulation, poking outside, where they can potentially touch other wires. The process appears to take at least a couple of years and as many as six years or more before it causes detectable problems, if it does at all. No one knows how often the conductor wires become exposed, but the prevalence is as high as 15% of Riata patients in some non–peer-reviewed reports [2].
The more recently manufactured Riata leads with the proprietary Optim sheaths don't seem to have the erosion problem.
Often nothing out of the ordinary happens, at least at first. The "externalized" wires are associated with electrical abnormalities perhaps only one-fifth of the time, according to St Jude [3]. They include predominantly changes in pacing or defibrillation impedance or inappropriate defibrillator therapy, it says, but also electrical "noise," altered pacing thresholds, and oversensing.
Now What?
There remains a lot of uncertainty about how to manage patients who have been implanted with Riata leads, whether or not they have shown signs of electrical abnormalities, according to Dr Robert G Hauser (Abbott Northwestern Hospital and Minneapolis Heart Institute, Minneapolis, MN), who along with Dr David L Hayes (Mayo Clinic, Rochester, MN) is directing today's meeting. One estimate puts the percentage of asymptomatic Riata recipients with externalized leads at 10% [3].
"What we hope to accomplish by the end of the day is some sort of consensus around patient management," Hauser told heartwire .
St Jude, which has launched a prospective registry study expected to include at least 500 Riata recipients with externalized conductor wires who aren't having electrical issues, has provided guidelines for managing patients [2].
Expert opinion on the matter is scarce in the literature. By and large, clinicians have been developing their own strategies independently. Hauser said he hopes the conference will produce a set of management guidelines or options to put everyone on the same page.
Déjà Vu?
It's tempting to compare the Riata recall to the recent and far-reaching recall of the popular Medtronic Sprint Fidelis ICD leads, but Hauser said there are important differences. The Riata affair "is a very complex one," he said, compared with the Fidelis problems, which were "much more straightforward--it was a conductor fracture, everybody understood that. Symptoms were similar [among affected patients], and the failure mechanisms were similar. With Riata, there are a lot of variables, and I think we're going to need more data to understand how best to manage patients than we usually need in a recall situation."
For example, he said, which signs of failure should be monitored most closely? What is the time course for all the different apparent modes of failure, such as impedance and pacing threshold changes or electrical noise? "Then, when it comes down to managing a failed lead, what's the best way to extract it? Or should you extract it?"
Then there are the frequent Riata patients with eroded leads but no apparent electrical abnormalities. "They have externalized conductors that are still electrically intact and functioning normally," said Hauser, lead author of a recent analysis of mechanisms behind the conductor externalizations in reported Riata failure cases [1].
It suggested that the externalized conductors still remain insulated by their thin coating of the plastic ethylene tetrafluoroethylene (ETFE) but also that the ETFE insulation itself eventually wears away. That probably explains how patients with externalized leads don't, at least at first, have electrical abnormalities. "That's a whole separate management problem," Hauser said.
In their report, Hauser and his colleagues speculate that "while the ETFE may appear to be electrically intact in low-voltage applications, it may not withstand the energy delivered by a high-voltage shock. In this study, we found abraded cables, meaning that the ETFE had been damaged; the patients who had abraded cables tended to receive inappropriate shocks."
"We're Early On" in the Riata Story
Reports that may be helpful in defining the rate of asymptomatic conductor externalizations keep trickling in. In a recent single-center study of 52 patients who underwent ICD interrogation and chest X-ray a mean of 71 months after Riata lead implantation, conductor externalizations were confirmed by fluoroscopy in 11.5% [4]. No abnormalities were apparent at device interrogation, and two of the patients had previously experienced appropriate and effective antitachycardia pacing and shocks.
"We're early on in trying to figure out the Riata story, so there are still a lot of unanswered questions," agreed Dr Charles A Henrikson (Oregon Health and Science University Portland), who published an editorial [5] on the Hauser et al report. "What do we do about a lead that, on fluoroscopy, shows that the conductors have eroded out through the insulation, but the lead interrogates fine?" he wondered to heartwire . "It would be my inclination not to trust the lead anymore, but there aren't really any data to support that."
But should every Riata recipient undergo fluoroscopy to see whether the conductors have eroded through the insulation? Henrikson pointed out that the problem leads went off the market in 2010, and the electrical abnormalities, if any, don't manifest for a number of years. It's much easier and less risky to remove an ICD lead after a year and a half than after five or six years. And that, he speculated, might just be incentive enough to start screening all Riata recipients with fluoroscopy.
"I wouldn't be surprised if we ended up at that point several months or a year from now," he said, "but I still question what we would do with the information." What he does now is follow Riata patients every three months (guidelines recommend every three to six months) with device interrogation. "And we tighten up the [allowable] impedance window, so if that starts to vary, we know a little earlier."
Also, many Riata patients now or will soon need a generator change-out. Henrikson said he counsels them about their lead options. If such patients are older and have never had an inappropriate shock, it may be best just to keep the Riata active and exchange only the generator. Another option is to add a new lead and leave the Riata in place but inactive. But, "we certainly encourage patients who are younger and healthier and have a longer life expectancy to have the old lead taken out and replaced."
Heartwire from Medscape © 2012 Medscape, LLC
Cite this: 'Recalled' Riata ICD Leads: Brainstorming Conference Aims for Guidance - Medscape - Jan 20, 2012.
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