Nanostim Still a Contender at One Year, Bigger Trial Welcome

May 10, 2014

SAN FRANCISCO, CA — The Nanostim leadless pacemaker (St Jude Medical) "behaved just as expected" in 33 patients evaluated a year after the tiny device was percutaneously inserted and attached to their right ventricular walls, reported investigators, with findings that build on promising 90-day data showing it can successfully achieve single-chamber RV pacing[1].

Dr Vivek Y Reddy (Mount Sinai School of Medicine, New York, NY) presented an update on the LEADLESS study of the Nanostim, which passed a regulatory milestone in October 2013 when it gained the CE Mark for commercial availability in Europe, here at the Heart Rhythm Society 2014 Scientific Sessions .

Reddy's presentation was mostly a recap of short-term results for the cohort, all non–pacemaker-dependent patients with indications for rate-responsive ventricular (VVIR) pacing  treated at two centers in Prague, Czech Republic, and one in Amsterdam, the Netherlands. Those results included acceptable pacing thresholds, impedances, and battery voltages, an average implantation procedure time of 28 minutes, and a freedom-from-complications rate of 94%.

After three months and out to one year, he said, "There were no additional safety events, no device migration or device dislodgements, no instances of infection, no mechanical failures of the device or early battery depletion, and no evidence of proarrhythmia." Six patients required hospitalization for reasons unrelated to the device, according to Reddy.

Dr Vivek Y Reddy

"What we found [at one year] is that the device behaves just as we expected it to. It continues to behave appropriately; there were no additional complications, and fundamentally, the device seems to work," Reddy told heartwire .

In his formal presentation, he acknowledged that the current feasibility study is small, but it has "raised the possibility of being able to remove the weakest link with pacemaker systems, which is of course the lead."

Largely unaddressed in the limited Nanostim experience are unknowns about how the device will behave not at one year, but five, 10, or 15 years down the line, and how it will interact with the myocardium over the long term.

Pull It Out, or Put More In?

After Reddy's formal presentation of the one-year Nanostim results, session moderator Dr Hugh Calkins (Johns Hopkins University, Baltimore, MD) brought up another issue that will become bigger as patients have the device for increasingly longer periods.

"What's the strategy for when the battery runs out? Do you pull it out and put in a new one, or just keep putting in new ones every 10 years?" Calkins said.

Dr Hugh Calkins

"That's a good question. The real answer is, I don't know," Reddy replied. "Having said that, let's think about the possibilities." He had earlier noted that the Nanostim has an "extremely impressive" projected lifetime for its tiny battery. "Based on impedance and on percent pacing, one can expect somewhere between nine to 19 years of battery life."

Still, the device is designed to be retrievable, and it indeed is based on preclinical work and two inadvertent cases in which retrieval became necessary, he said. In one patient, the device was accidently placed in the left ventricle. In another, the patient developed VT as it was affixed. "In both situations, we were able to go back in with the retrieval catheter and take out the device. So acutely and subacutely, we know we can retrieve it, no doubt about it."

How retrievable will the Nanostim be after say, a decade of use, Reddy asked. Will it endothelialize so thoroughly that the retrieval catheter won't be able to grab hold? "The answer is: we'll know 10 years from now when we start removing these devices." Data on late retrieval from animals should be available later this year, he said.

"The other possibility is, of course, that at the time when we need to change the battery, we can always put in another device," Reddy said. "We know that technically it's feasible. How practical is it? Well, the device has a displacement of only 1 cc. It's not impractical to think about putting one or two or three of these devices, ultimately, in the patient. If we have battery lives approaching 15-plus years, then I think it's certainly a possibility."

Or, he said, "You can always put in a traditional lead at the time of changing the device."

Next Steps

The prospective, observational LEADLESS 2 study, with a projected enrollment of about 670 patients with indications for VVIR pacing at 50 centers in the US and Canada, "commenced a couple of months ago," according to Reddy. And, the LEADLESS Observational Study is under way at four European centers with a projected enrollment of 1000 patients.

"And I should point out that, in development, there is an atrial leadless cardiac pacer," he said. "The hope is that this device will be able to communicate with the ventricular devices and, of course, I think everyone is aware of the potential implications, allowing this [approach] for multichambered pacing, not just ventricular pacing."

The LEADLESS study, LEADLESS 2, and the LEADLESS Observational Study are funded by St Jude Medical, for which Reddy discloses receiving compensation for consulting and serving on an advisory board. "In addition," according to a statement from Mount Sinai Hospital, " in 2013 he received one-time financial compensation from St Jude Medical in the form of an option buyout relating to St Jude Medical's acquisition of Nanostim." He has received consulting fees/honoraria from Biosense Webster, St Jude Medical, Medtronic, Biotronik, CardioInsight Technologies, Endosense, Sentreheart, ACT, Abiomed, Boston Scientific, and Coherex. He holds equity interests/stock options in ACT, Nanostim, and Vytronus. He has received research grants from Biosense Webster, St Jude Medical, Boston Scientific, and CardioFocus.

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