Riata Lead 'Externalizations' Promote Electrical Failure: Longitudinal Study

July 11, 2014

COPENHAGEN, DENMARK — Prospective follow-up of nearly all patients in Denmark who had been implanted with Riata and Riata ST defibrillator leads (St Jude Medical), which had been recalled worldwide in 2011 because of electrical abnormalities and apparent tendency for a unique kind of wear-and-tear damage, has largely confirmed that the two problems are related and are likely to get worse over time[1]

"This is an important paper," according to Dr Laurence Epstein (Brigham and Women's Hospital, Boston, MA), referring to the report published July 4, 2014 in Heart Rhythm. Epstein, who isn't a coauthor but has been on top of the Riata saga from its outset, told heartwire that its main messages are that "the electrical failure rate is much higher than people had thought, and two, it is linked to cable extrusion."

Indeed, the analysis suggests that Riata leads confirmed to have externalizations are more than four times as likely to develop electrical abnormalities as those without evidence of externalization.

The findings don't prove cause and effect or, instead, whether externalizations are simply a marker for "potentially failing 'stressed' leads," lead author Dr Jacob M Larsen (Aalborg University Hospital, Denmark) cautioned heartwire by email. "We cannot tell from the available data. But the data strongly suggest that a recalled Riata lead with visible externalization is associated with a higher risk of electrical abnormalities in the clinical setting."

Epstein said the report pretty much confirms that the externalization process is an ongoing one. But despite all the focus on externalizations, the main point is that "the leads have this potential to fail, and a potential to fail in a catastrophic way, when the patient needs the device to save their life, but it shorts and doesn't deliver therapy."

In fact, he added, the new report probably underestimates the hazard associated with Riata leads that are not replaced, because it does not describe the "life-threatening" shorting risk associated with the externalizations.

What to Do?

Larsen said that "the progressive nature of externalizations and the strong association with new electrical abnormalities emphasize that fluoroscopic screening seems to contribute valuable clinical information," supporting the FDA stance that patients with the leads undergo appropriate imaging.

Still, Larsen pointed out that "Riata leads without visible externalizations also have a higher rate of electrical abnormalities than seen for contemporary benchmark leads, and fatal electrical failures with short circuits in the pocket area or under shock coils have mostly been associated [with] leads without externalizations in previous studies and case reports." A normal fluoroscopy study, he emphasized, "is not sufficient to reliably risk-stratify the patients with recalled Riata leads."

An FDA statement with a most recent date of June 3, 2014 recommends that "patients who have not had a recent evaluation and device interrogation should undergo those exams to assess for any electrical abnormalities."

It further recommends that "physicians image Riata and Riata ST leads implanted in patients to assess for externalization or other visible insulation abnormalities" but also states that "the value of repeat imaging for leads initially assessed as intact is uncertain."

Even as of today, the most recent document for physicians available through St Jude's dedicated Riata web information site states, "The majority of studies have shown no correlation between the presence of externalized conductors and electrical failures."

Riata Design Issues

As heartwire has long reported, the Riata lead's design was such that its internal conductor cables can move longitudinally within the exterior silicone insulation as the lead flexes, sometimes eventually eroding through. Such externalizations were long seen as related to noninvasively observed electrical abnormalities in Riata leads, which had been associated with inappropriate shocks and possibly high-voltage shorts. Fluoroscopy can but may not visualize the problem, and it may or may not be electrically evident right away.

But fluoroscopic Riata externalization rates are much lower than electrical failure rates, which have long been distinguished from each other without much solid understanding of whether they are linked. In the face of widespread perception that the two issues must be related, St Jude had long asserted that the cables have an insulation coating that likely protects them against electrical failure even if externalized.

The New Data

The new analysis is based on longitudinal follow-up of a nationwide cohort that had been previously described in cross-sectional fashion and that saw an 11% externalization rate a mean of 5.1 years after lead implantation, with 19 Riata-related electrical abnormalities among the 295 patients. The externalization rate ranged from 6% over 4.5 years for 7F leads to 21% over 6.4 years for 8F leads, heartwire previously reported.

In the new analysis of the cohort, 239 patients who still had normal fluoroscopy at the cross-sectional analysis showed a 3.7 per 100 person-year rate of new fluoroscopic externalization after about a year of follow-up, independent of time since implantation. Among 27 patients with externalizations at baseline of the current study, the length of externalized cable had grown a mean of 4 mm (p<0.001). Patients with normal Riata electrical function at baseline of the current analysis showed a new electrical abnormality rate of 7.1 per 100 person-years.

Importantly, new electrical abnormalities were 4.4 times more common in leads with baseline externalizations than those without (p=0.002).

Replace Them, but Extract Them as Well?

 
It's never [going to be] easier to take the leads out than it is today.
 

"Replacements of recalled Riata leads with or without lead extraction should be considered in high-risk patients and patients with long life expectancy," Larsen said, "especially if a golden moment of opportunity arises, as in elective generator replacement due to battery depletion or system upgrade."

The risks of lead extraction "aren't trivial," according to Larsen, so "an individualized approach weighing risk and benefits should guide the decision, always in respect of the wishes of the patient. The progressive nature of externalizations indicates that lead extraction may be the better choice in young patients with long life expectancy."

In the report, there were 15 extractions, which were associated with two major complications; the leads in 23 other patients were abandoned as replacements went in. Those in whom the leads were extracted averaged 11 years younger (p=0.01).

Extraction was associated with "one minor and two major complications: a large pocket hematoma postponing discharge for five days, a stroke due to paradoxical thromboembolism passing through a persistent oval foramen causing long-term mild cognitive injury, and a right ventricular wall tear with cardiac tamponade treated successfully by thoracotomy but leading to postoperative death after nine days due to respiratory failure," Larsen et al write.

"The present study was not powered to investigate extraction outcomes, and the two major complications observed in 15 extractions should be used only as a reminder that lead extraction is not without risk."

Epstein is one of the world's most experienced at removing defibrillator leads and acknowledges that he is more aggressive than most in recommending Riata extraction. He says he has the exceptionally low complication rate to justify such a course and offers it to patients whether or not the leads appear to be working as intended.

"At high-volume centers with excellent outcomes, I think being more aggressive with these leads is warranted," Epstein said. "I think leaving these leads behind is going to be dangerous. The bottom line is this: It's never [going to be] easier to take the leads out than it is today."

Larsen discloses receiving fees for speaking from Biotronik; disclosures for the coauthors are listed in the paper. Epstein discloses consulting or lecturing for Spectranetics, Medtronic, Boston Scientific, St Jude Medical, and General Electric.

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