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SAN FRANCISCO -- Longer-term results from the first-in-man study of the Nanostim leadless pacemaker showed the device continued to work as expected, but a postmarketing study in Europe has been temporarily halted following reports of perforations and deaths.

Through 1 year, measures of pacing threshold, impedance, R-wave amplitude, percentage pacing, and battery voltage remained similar to those seen in the initial 3 months of follow-up, according to , of the Icahn School of Medicine at Mount Sinai in New York City.

Also, there were no additional adverse events uncovered from 3 to 12 months in the 33 patients enrolled in the preliminary study, Reddy reported at the Heart Rhythm Society meeting here.

The results indicate that leadless right ventricular pacing is feasible, Reddy said. He acknowledged that the study was small, but said that "this raises the possibility of being able to remove the weakest link of pacemaker systems, which is of course the lead."

European Hiccups

The leadless pacemaker, which is about 4 cm long with a 6 mm diameter and attaches to the heart muscle inside the right ventricle, is currently being further evaluated in the in the U.S. and in Europe -- where it has been approved -- in a postmarketing study.

However, the European study recently stopped enrolling patients after reports of six perforations, including two that resulted in death. Patient enrollment up until that point was in the "mid-100s," according to , vice president of global clinical affairs and chief medical officer for device maker St. Jude Medical, headquartered in St. Paul, Minn.

He said the study was halted immediately after the company learned of the deaths to investigate the contributing factors, an investigation that included speaking with leaders of both the U.S. and European studies and all appropriate regulatory bodies -- including the FDA -- and conducting a thorough analysis of every aspect of the study.

After that, the company brought suggestions to the steering committee of the postmarketing study about making the inclusion criteria consistent with those that were already present in the U.S. study, such as excluding patients with a cardiovascular surgery in the last 30 days. They also reinforced certain methods of implantation and developed a training video detailing best practices and also what not to do.

Carlson said the postmarketing study will begin enrolling patients again in the next 2 weeks, adding, "We remain very excited about this technology."

, an electrophysiologist at Intermountain Heart Rhythm Specialists in Utah and program chair for this year's meeting, also expressed excitement about leadless pacing.

"This is truly a disruptive technology. For years, the Achilles' heel has really been these wires," he said. "This has the potential to completely disrupt the whole pacemaker concept."

Addressing the complications seen in the postmarketing study, Day said, "What's always a challenge whenever you roll out new technologies is that learning curve."

Problems will arise with any new technology, he added, and "as with any new disruptive medical technology, there will be refinements to make it safer, to make it easier, and to make it more effective."

Feasibility Study

The feasibility study enrolled 33 patients with one of three main indications for a pacemaker (although none were pacemaker-dependent):

• Permanent atrial fibrillation with second- or third-degree atrioventricular block (67%)
• Normal sinus rhythm with second- or third-degree atrioventricular block and significant comorbidities (18%)
• Sinus bradycardia with infrequent pauses or unexplained syncope (15%)

The implant success rate was 97% and the complication-free rate was 94%.

Pacing and sensing parameters observed in the first 3 months of follow-up remained consistent up to 1 year.

Previously reported early safety events included one inadvertent placement of the pacemaker in the left ventricle, one case of ventricular tachycardia, one minor groin hematoma, and one case of tamponade requiring surgery. That last patient -- who had atrial fibrillation but was not taking anticoagulation -- ultimately died of stroke.

No additional events were seen after 3 months of follow-up. Reddy said there were no instances of device migration or dislodgement, infection, mechanical failure, early battery depletion, or pro-arrhythmia. There were about six hospitalizations, but none was considered related to the device.

"I think what he's shown us now in this pilot study is basically it's a safe device, the numbers look very good after about 12 months, it appears to be working fine, and the complication rate is tremendously low," commented , of the Nevada Heart and Vascular Center in Las Vegas. "I'm very excited about this type of technology. It certainly could be a game-changer in many ways."

Outgoing HRS president , director of the cardiac arrhythmia service at the Johns Hopkins Hospital in Baltimore, also had a positive view of the device.

"The whole concept of leadless devices is extremely important and interesting, and I think the data that were presented are certainly supportive that this is going to be a real success story," he told 番茄社区.

He said proof of safety and efficacy will come in the IDE trial, but predicted that the device would be approved in the U.S. within the next 2 years.

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