St. Jude reports strong U.S. clinical trial results for its leadless pacemaker

St. Jude's Nanostim leadless pacemaker--Courtesy of St. Jude Medical

St. Jude Medical's ($STJ) leadless pacemaker fared well in its investigational U.S. trial, as the company seeks to secure FDA approval for the device and overcome a safety scare that marred its European launch.

At the European Society of Cardiology Congress in London, the company announced that the Nanostim leadless pacemaker met its primary endpoints for effectiveness, defined as appropriate pacing and sensing, and safety, or freedom from serious device-related adverse events. More information is available in The New England Journal of Medicine.

According to a release, 22 serious adverse events were reported over the 6-month period. Cardiac perforation, device dislodgement and elevated pacing capture thresholds occurred at a rate of less than 2%.

The rate of perforation is particularly important because the problem caused two patient deaths in a 2014 European postmarket trial, which followed the Nanostim's CE marking in 2013. The deaths caused St. Jude to halt sales in Europe for about a year, though implantations have recently restarted. The adverse events have been blamed on operator error and less-than-optimal study inclusion criteria.

Overall, 6.7% of patients in the 526-subject U.S. trial experienced a serious adverse event at 6 months postimplantation.

"The 6.7% adverse event rate is on the high side, but, at the same time, for something as new and as disruptive as this, it is pretty good because only about 1% of patients had cardiac perforations and you can get cardiac perforations even with conventional cardiac pacemaker implantation," Dr. Jagmeet Singh of the Corrigan Minehan Heart Center at Massachusetts General Hospital told MedPage Today.

Device retrievability is an important consideration, Singh said in the MedPage Today article: "The big question is how long are the devices going to work before you have to replace them? Their estimated longevity is about 9-10 years. At that point in time, it will be a huge issue over whether you can take it out or do you have space to add another one in?"

St. Jude said that during the trial, retrieval of the Nanostim was successful 100% of the time in patients requiring the procedure. In addition, the company said that the device's battery is expected to last about 15 years, and the entire device should last about 10 years at 100% pacing.

Leadless pacemakers eliminate the need for leads, or electrical wires, which can fail, resulting in patient injury. In fact, the previous failure of St. Jude's Riata defibrillator leads resulted in fatalities and led the company to pay as much as $14.25 million to settle about 950 legal claims.

In addition, the Nanostim is less than 10% of the size of its traditional counterparts, so it can be implanted using minimally invasive techniques, such as delivery to the heart via the femoral vein.

Medtronic ($MDT) received CE mark approval for its Micra leadless pacemaker in April and hopes to overtake St. Jude's by avoiding the early perforation issues that plagued the Nanostim's European launch.

In May, Boston Scientific ($BSX) announced its plans to join the leadless pacemaker market and hopes to pair such a device with its subcutaneous implantable cardioverter defibrillator (S-ICD). The fast-selling S-ICD has shown the potential of cardiology products that eliminate or lessen the use of leads, albeit in the related but distinct market for implantable defibrillators. Sales of the S-ICD are more than $100 million per quarter.

The Micra and Nanostim are for single-chamber pacing only, which limits their applicability. The study's principal investigator, Dr. Vivek Reddy, told MedPage Today that about 15% of his pacemaker patients would be candidates for a leadless version.

Leerink Swann equity analysts Danielle Antalffy and Puneet Souda estimate that leadless pacemakers will earn $700 million in 2016. A dual-chambered leadless pacemaker that works on both sides of the heart has the potential to get the vast majority of the $3.5 billion pacemaker market, they say.

- read the release
- get the MedPage Today story
- here's more in the NEJM

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