COMMENTARY

Potential Major Problem With a Common Pacing Lead

John M. Mandrola, MD

Disclosures

May 18, 2018

The patient had done well since her pacemaker implant almost 2 years ago. Then the blackout spells started.

The pacer clinic sent me this ominous picture.

It shows oversensing of electrical noise on the right ventricular lead. When this occurs in a patient dependent on a pacemaker, it is an emergency because the patient has no heartbeats of her own. 

How could this happen to a less than 2-year-old lead, I thought?

Her surgery to place a new lead went well. The old lead had no gross defects. I removed it without trauma. The company analyzed the lead and described an external insulation abrasion at a point where the lead was touching the generator. The abrasion had exposed the outer coil.

At this point, I figured this was just one of those things that occasionally happen. The lead, a St Jude Medical (SJM; now Abbott) Tendril model 2088TC, is a workhorse lead used by operators across the world. Surely if there was a problem with this lead, normal postmarket surveillance would have found it.

Maybe not.

HRS Poster on Lead Failure

During a featured poster session at the Heart Rhythm Society (HRS) 2018 Scientific Sessions, Emory investigators presented their experience with Tendril lead malfunction.

They retrospectively identified patients in their system who had an SJM Tendril lead (2088TC or 1688TC) or a Medtronic CapSureFix Novus 4076 lead between January 2007 and May 2016.

The comparison group included 751 Tendril leads and 269 Novus leads. The researchers defined lead malfunction as insulation breach manifested as noise or low impedance or lead fracture and high impedance.

Most of the Tendril group had 2088TC leads (n = 665), the same lead as my patient's.

The two nonrandomized groups were evenly matched in baseline characteristics.

The results were stunning. In the Tendril group, 51 patients (6.8%) experienced lead malfunction compared with only 1 patient (0.37%) in the Novus group. One hardly needs a P value, but here it was calculated to be .00004

The average time to failure was only 2.6 years — similar to my patient's experience. Pacing leads typically last decades.

The authors found that the most common cause of Tendril lead malfunction was insulation breach (77%), manifesting mainly as noise (51%) or low impedance (26%). Lead fracture was observed in 22% of Tendril lead failures.

Poster Findings Echo EP Experiences

This was a retrospective single-center study with nonrandomized group comparisons. It has serious limitations and is not yet published.

That said, it's hard to dismiss an 18-fold greater risk for lead failure as spurious. Remember, Optim coating figured in fixing the Riata lead recalls. A short summary of the Riata issue was that these classes of leads are susceptible to abrasion because of internal motion of the cables within the lead. The main fix for this defect came when SJM added Optim insulation to the next generation of leads (Durata).

The safety of SJM leads therefore turns on the reliability of this proprietary insulation. Most SJM leads use Optim insulation. 

I am concerned. My patient had a breach of Optim insulation in less than 2 years. The Emory poster showed large numbers of similar cases, many due to insulation breaches over short time frames. Edward J. Schloss, MD, an established lead expert from Christ Hospital in Cincinnati, Ohio, echoed these worries in a series of comments on Twitter. Schloss wondered whether the 2018 HRS meeting would be remembered not for the CABANA trial but for the session in which this poster was presented. He called the results of the Emory findings troubling and asked: "Do we have a new lead failure problem on our hands?"

Other implanting doctors have also commented publicly. Mark Perrin, MD, an electrophysiologist from Geelong, Australia, shared a picture of noise from a 2088TC lead on Twitter. He expressed concern about his large population of patients with this lead. Perrin also cited a colleague who had to replace three similar leads for failure.

I asked senior authors Mikhael El-Chami and Faisal Merchant what made them study this question. In an email, they wrote that they too noticed a higher than expected rate of problems with these leads and discussions with other electrophysiologists seemed to provide anecdotal support for their observations.

The potential for insulation problems with this lead has a history. In 2013, Charles Swerdlow, MD, and colleagues from Cedars Sinai in Los Angeles, California, published a case of an SJM defibrillator lead failure[1] that implicated the failure of Optim insulation to prevent internal abrasion. SJM engineers and physicians countered the claim, saying that damage to the lead came from the trauma of extraction.[2] Another case report found external abrasion of an Optim-coated lead.[3]

A larger study, also published in 2013, queried the US Food and Drug Administration's Manufacturers and User Facility Device Experience (MAUDE) database and found numerous case reports of external and internal abrasions in Optim-coated SJM defibrillator leads over an average time frame of only 22 to 29 months.[4]

These observations would not make sense without plausibility. The Swerdlow case report cited an engineering paper that found the raw material used in Optim insulation can undergo hydrolytic degradation, which can reduce tensile strength.[5] This is critical because in the Tendril 2088TC pacing lead, a conducting cable within the lead is protected only by Optim insulation.

What Next?

These are early data from one center, but given the strikingly higher rate of Tendril lead failure, the history from published reports, the concerns of many implanting physicians, and a possible mechanism of insulation failure, I see enough signal to warrant much more investigation into this potentially major health problem.

And if this turns out to be a problem, we should also study how it eluded us for many years.

Editor's Note: theheart.org | Medscape Cardiology reached out to SJM for comment but did not receive a response by the time this column posted.

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