Another Study Raises Concerns Over Tendril Pacing Leads

Patrice Wendling

December 17, 2018

Another single-center study suggests that problems with the St. Jude Medical (now Abbott) Tendril pacing leads are higher than expected and well above company reports.

Inappropriate noise sensing occurred in 9% of Tendril bipolar pacing leads (models 1688 TC, 1788 TC, 1888 TC, and 2088 TC) implanted in 870 patients between September 2003 and June 2015.

Reprogramming reduced noise detection in 63% of the cases; however, 17% of patients required lead replacement. Insulation breach was confirmed in two of the four extracted leads.

According to the company's 2012 product performance report, these leads had an incidence of oversensing of less than 0.05% and a total malfunction rate between 0.12% and 0.02%, noted senior author Dennis W. Zhu, MD, director of electrophysiology, Regions Hospital, St. Paul, and professor of medicine, University of Minnesota, Minneapolis.

"I talked to the engineers 3 years ago because we ran into this noise problem and they said their device was too sensitive," Zhu told | Medscape Cardiology. "They did not say there was anything wrong with their leads but we had to reprogram the device to make the leads a little bit less sensitive. It helped but it did not solve the problem."

The study involved 1065 Tendril leads (178 model 1688 TCs, 215 model 1788 TCs, 283 model 1888 TCs, and 389 model 2088 TCs) and 145 Medtronic CapSureFix Novus leads (57 model 4076s and 88 model 5076s). Patients were followed every 3 months with remote home monitoring and annually in the clinic.

Tendril leads were implanted in slightly older patients and were more commonly part of a permanent pacemaker (62% vs 53.4%), whereas Medtronic leads were more commonly implanted in patients with atrioventricular block (28.7% vs 21.5%).

The rate of inappropriate noise sensing was significantly higher for Tendril model 1688 TC, 1788 TC, 1888 TC, and 2088 TC leads than for Medtronic 4076 and 5076 leads (8%, 5%, 10%, 10% vs 2%, 1%; P = .007).

Rates of abnormal impedance were also higher (3%, <1%, 1%, 1% vs 0%, 0%; P = .007).

To exclude a primary generator issue as the cause of the noise, Zhu and his colleagues also enrolled 145 patients with Medtronic leads connected to a St. Jude pacemaker or defibrillator. Among these patients, the incidence of inappropriate lead noise was only 1% during an average follow-up of 3.6 years.

"We don't use St. Jude leads anymore because there is too much noise," Zhu said. "We need a better way to monitor leads and to improve the follow-up because the company is still making these leads."

The study was reported in a poster at the American Heart Association 2018 Scientific Sessions and follows a similar poster presentation by Emory investigators this spring.

As reported at the time by Medscape Cardiology, lead malfunction occurred in 6.8% of Tendril 2088 TC or 1688 TC leads, compared with only 0.37% of Medtronic's 4076 leads. The most common cause of Tendril lead malfunction was insulation breach (77%), which manifested as "noise" (51%) or low impedance (26%). Lead fractures occurred in 22% of Tendril leads. The average time to failure was only 2.6 years.

Justin Paquette, Abbott director of public affairs for cardiac arrhythmias and heart failure, told | Medscape Cardiology in an email that "we take all single-center experiences with our products seriously and based on Emory's initial analysis, felt that a deeper dive into our own data was important."

As a result, Abbott recently assessed data, examined product returns, reviewed US Food and Drug Administration (FDA)'s Manufacturers and User Facility Device Experience (MAUDE) data, and performed an additional analysis of Abbott active registries.

"Our analyses showed that while Abbott devices are more likely to record and store noise events than other manufacturer's devices to help physicians assess patient needs, lead noise is not always indicative of lead malfunction," Paquette said.

"In fact," he said, "Tendril leads continue to demonstrate strong overall reliability, and 8-year survival rates for the Tendril lead are among the industry's best."

Paquette declined to disclose the results because "we are pursuing publication or presentation of the data."

A second, larger study by the Emory investigators, recently published in Heart Rhythm, suggests that the higher malfunction rates reported with Tendril leads are driven in part by the newer 6-French 1888 and 2088 leads. Both models feature the proprietary Optim insulation, designed to overcome the high rate of insulation failure that contributed to St. Jude's 2011 worldwide recall of Riata leads.

The study involved 9782 implanted leads, including 8512 Tendril (2088 TC, 1888 TC, and 1688 TC) leads, 731 Medtronic 4076 leads, and 539 Boston Scientific Fineline II Sterox Pacing EZ (models 4469, 4470, and 4471) leads.

At 5 years, the lead malfunction rate was significantly higher for the Tendril leads than for the non-Tendril leads (7.0% vs 2.1%; P < .001). Lead malfunction manifested primarily as noise and/or low impedance (95%).

The adjusted 5-year failure rate was highest for the Tendril 1888 TC (9.9%), followed by the older 7-French silicone-insulated 1688 TC (5.7%), 2088 TC (5.2%), Medtronic 4076 (2.6%), and Fineline II leads (1.7%).

There was also a trend for higher malfunction rates in the Optim- vs non-Optim-insulated leads at 5 years (7.1% vs. 5.2%; P = .112) that reached statistical significance at 10 years (24.5% vs 7.1%; P = .008), according to lead author Mikhael F. El-Chami, MD, Emory University, Atlanta, and colleagues.

There were 65 leads revisions, including 18 pacemaker-dependent patients with evidence of RV lead malfunction, all of whom had Optim insulated St. Jude leads.

Of special note, the workhorse 2088 TC leads comprised 88.5% of the 751 Tendril leads in Emory's initial single-center review.

"In our institution, we mainly used the Tendril leads for a long time, but over the last 3 or 4 years, when we started noting some of the problems with the Tendril, we switched to Medtronic or Boston leads," El-Chami told | Medscape Cardiology.

According to Abbott's 2018 product performance report, rates of insulation breach and conductor fracture for the 2088 TC are 0.10% and less than 0.01%, respectively. However, only 3.2% of the 585,050 model 2088 TC implants registered in the United States were returned for analysis.

"Abbott leads with Optim insulation have been some of the industry's most durable and reliable cardiac leads, with a history of strong performance and safety," Paquette said.

Asked whether Abbott is in contact with the FDA over the Tendril leads, he replied: "Abbott has maintained ongoing, transparent communication with the FDA related to both the construction of our own internal analyses as well as the results of those analyses, which have not raised any safety, effectiveness, or longevity concerns specific to the Tendril leads."

Laurence D. Sterns, MD, Vancouver Island Heath Authority, Victoria, British Columbia, who wrote an editorial accompanying the second Emory study, said in an interview: "I think there is a real issue. I think there is more noise out that these leads are picking up; I don't think it's true mechanical failures."

Sterns noted that when Abbott changed to the Optim insulation, it also went from 7-French to 6-French leads. "So it may not be the Optim but rather the fact that they went to a smaller construction with less insulation that might be the reason for it picking up this noise," he said. Contradicting this, however, is the fact that Boston Scientific's Fineline II 5.1-French leads had far lower failure rates than the Abbott leads.

Another potential confounder could be that some of the increased noise from the Abbott leads is the result of differences in its mode switch algorithm, compared with other devices.

"I don't think it's related to any device algorithms because if you look in our study, we've had Medtronic and Boston leads linked to St. Jude cans and the rate of noise was not high," El-Chami said. "We've also had the opposite — St. Jude leads linked to non-St. Jude cans — and the rate of noise was still high. So I don't think the theory of an algorithm that is very sensitive at detecting noise is the cause of this problem. On the contrary I think it is lead related."

What both men can agree on is that data collection on leads is flawed.

"We really need a better way of surveying the performance of these leads because if you look at every single recalled leads over the last few years, the original data from the performance report seems to point to a low failure rate until reports from individual institutions start showing higher failure rates," El-Chami said.

Sterns pointed out that Canada is trying to expand national data collection through the Canadian Registry of Implantable Electronic Devices Outcomes (CREDO), which has reported on the Riata leads and Abbott battery performance.

"We've got multiple centers across the country trying to use standard definitions of lead failure. I think that's the kind of thing that needs to be set up in the US because we need this in more than one country," he said. "That, I think, is where we really need to go."

Zhu and his coauthors report no relevant conflicts of interest. Sterns reported having no relevant conflicts. El-Chami reports consulting for Medtronic and Boston Scientific.

American Heart Association (AHA) Scientific Sessions 2018: Abstract Su3106. Presented November 11, 2018.

Heart Rhythm. Published online October 24 and November 9, 2018. Full text, Editorial

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