Leadless Pacemaker Performs Well Through 1 Year

A novel leadless cardiac pacemaker demonstrates stable performance and reassuring safety over 1 year after implantation, according to results from a small study published in the April 21, 2015, issue of the Journal of the American College of Cardiology.

“With a leadless pacemaker design, lead and pocket complications can be eliminated, potentially resulting in lower complication rates,” write Reinoud E. Knops, MD, of the Academic Medical Center (Amsterdam, the Netherlands), and colleagues, adding that the system is a “promising” alternative to conventional devices.

For the LEADLESS trial, the researchers retrospectively looked at 33 patients (mean age 76 years; 65% male) with an indication for single-chamber pacing who were implanted with a temperature-responsive, rate-adaptive leadless cardiac pacemaker (Nanostim; St. Jude Medical) between December 2012 and April 2013 at 3 European centers. The main 90-day results of LEADLESS were published last year in Circulation.

Thirty-one patients were included in the current analysis of 1-year follow-up, as 1 patient died of a cerebrovascular accident and another had to have the device removed due to need for an implantable cardioverter-defibrillator.

Successful Implantation

All patients with 1-year follow-up had successful implantation in the apicoseptal region of the right ventricle, and median total implantation procedure time was 24 minutes. Mean threshold at implantation—the level that must be reached for an effect to be produced—was similar for the 29% of patients who required device repositioning and those who did not (0.83 V vs 0.75 V; P = .684). Likewise, there were no differences in this metric at discharge or at follow-up.

At a mean of 1.2 years postprocedure, all patients were alive with no pacemaker-related complications. Additionally, there was no evidence of pacemaker syndrome, device embolization, late perforation, device-related or other infection, thrombi on echocardiography, or device-induced ventricular arrhythmias. Furthermore, no patients required reintervention. Between 3 and 12 months of follow-up, 6 patients were hospitalized for causes unrelated to pacemaker implantation.

There were initial decreases in threshold and impedance and an increase in the R-wave between implantation and 1 day, but all of these performance measures remained stable from 3 months onward (P > .05 for the time effects between 3, 6, and 12 months; table 1).

Aside from a decrease in mean threshold between implantation and discharge in all patients (0.77 ± 0.51 V vs 0.41 ± 0.20 V; P = 0.001), no change in threshold of more than 0.25 V was observed in any patient between 3 and12 months postprocedure. Additionally, there were no early battery depletions, under- or oversensing, or pacing capture issues at follow-up.

The proportion of patients with a pacemaker-activated rate response set to activated rate response function grew over time:

• 6 weeks: 35%
• 12 weeks: 39%
• 6 months: 58%
• 12 months: 61%

Adequate rate response was obtained in all 19 sensor-activated patients.

Ongoing Studies to Answer Questions

“The occurrence of cardiac perforations, device embolizations, device-induced arrhythmias, and the need for reintervention needs to be assessed in the long term and in larger cohorts to evaluate the overall safety of this device,” Dr. Knops and colleagues suggest, noting that ongoing LEADLESS studies in Europe and the United States will provide clarity on long-term safety.

However, they observe that there is a learning curve associated with the percutaneous approach for leadless pacemaker implants. “Therefore, this new technique necessitates a solid training program for new implanters,” the authors advise.

‘The Future of Pacing’

In an editorial accompanying the study, Michael R. Gold, MD, PhD, of the Medical University of South Carolina (Charleston, SC), writes that “these early results are very encouraging.”

Approximately 65,000 lead failures occur annually in the more than 4 million implanted pacemakers worldwide, he reports. “Accordingly, this is a major problem that has persisted despite many improvements in lead and pulse generator design. For this reason, the leadless pacemaker was developed as a self-contained unit placed in the right ventricular apex via femoral vein access.”

The device has “many contemporary features, such as rate response, telemetry, and data logs.” Dr. Gold says. As shown in the current paper, he adds, it also has “remarkably stable pacing parameters.”

But he notes several study limitations, including a small sample size, limited number of experienced centers, and serious implantation complications. Drawbacks of the first-generation device include the ability to provide only right ventricular pacing, the lack of remote monitoring, and uncertainty regarding the usefulness of the temperature-based rate sensor, the editorial says.

Nevertheless, Dr. Gold expects that adoption of this technology could be high, especially in countries with cost-competitive traditional pacing systems. Long-term performance and retrievability will also be key to its success, Dr. Gold predicts.

The study points toward “a bright future for leadless pacing, with the likely possibility that the devices of the future will be largely devoid of intravascular leads, and many will not require subcutaneous pulse generators,” he concludes. “As such, these devices should become the future of pacing in many types of devices rather than persist as a niche to compete in the single-chamber pacemaker market.”

Sources:
1. Knops RE, Tjong FVY, Neuzil P, et al. Chronic performance of a leadless cardiac pacemaker: 1-year follow-up of the LEADLESS trial. J Am Coll Cardiol. 2015;65:1497-1504.
2. Gold MR. Are leadless pacemakers a niche or the future of device therapy [editorial]? J Am Coll Cardiol. 2015;65:1505-1508.

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