Leadless Dual-Chamber Pacemaker Clears Performance Hurdles

Cardiology, well into the age of leadless pacemakers, could be headed for an age of leadless pacemaker systems in which various pacing functions are achieved by multiple implants that "talk" to each other.

Even now, a leadless two-part pacemaker system has shown it can safely achieve atrioventricular (AV) synchrony in patients with standard indications for a dual-chamber device, at least over the short term, suggests a prospective observational study. Currently available leadless pacemakers can stimulate only the right ventricle.

Experienced operators achieved a 98% implantation success rate in 300 patients who received an investigational dual-chamber leadless system, the AVEIR DR i2i (Abbott).

Its two separately implanted miniature pulse generators achieve AV synchrony via "beat-to-beat wireless bidirectional communication," Daniel J. Cantillon, MD, said when presenting the study May 20 at the Heart Rhythm Society (HRS) 2023 Scientific Sessions in New Orleans. The system went on to best its predefined safety and performance targets, providing AV-synchronous pacing in 97.3% of patients for at least 3 months.

The system seemed to work well regardless of the patient's body orientation. "Sitting, supine, left lateral, right lateral, standing, normal walk, fast walk — we demonstrated robust AV synchrony in all of those positions and with movement," said Cantillon, of the Cleveland Clinic.

Should the device be approved, it could "expand the use case for leadless cardiac pacing" to include atrial-only, ventricular-only, fully functional dual-chamber pacing scenarios."

Cantillon is senior author on the study's online publication, timed to coincide with his HRS presentation, in the New England Journal of Medicine with first author Reinoud E. Knops, MD, PhD, Amsterdam University Medical Center, the Netherlands.

"The electrical performance of both the atrial and ventricular leadless pacemakers appears to be similar to that of transvenous dual-chamber pacemakers," the published report states.

More Data Needed

The study is important and has "significant implications for our pacing field," Jonathan P. Piccini, MD, MHS, told theheart.org | Medscape Cardiology. It suggests that "dual-chamber pacing can be achieved with leadless technology" and "with a very high degree" of AV synchrony.

"Obviously, more data as the technology moves into clinical practice will be critical," said Piccini, who directs cardiac electrophysiology at Duke University Medical Center, Durham, North Carolina. "We will also need to understand which patients are best served by leadless technology and which will be better served with traditional transvenous devices."

The AVEIR DR i2i system consists of two leadless pulse generators for percutaneous implantation in the right atrium and right ventricle, respectively. They link like components of a wireless network to coordinate their separate sensing and rate-adaptive, AV-synchronous pacing functions.

The right ventricular implant "is physically identical to a commercially available single-chamber leadless pacemaker" from Abbott, the published report states.

Leadless pacemaker systems inherently avoid the two main sources of transvenous devices' major complication — infection — by not requiring such leads or surgery for creating a pulse-generator subcutaneous pocket.

The first such systems consisted of one implant that could provide single-chamber ventricular pacing but not atrial pacing or AV synchronous pacing. The transcatheter single-chamber leadless Micra (Medtronic) for example, was approved in the United States in April 2016 for ventricular-only pacing.

A successor, the Micra AV, approved in 2020, was designed to simulate AV-synchronous pacing by stimulating the ventricle in sequence with mechanically sensed atrial contractions, as described by Cantillon and associates. But it could not directly pace the atrium, "rendering it inappropriate for patients with sinus-node dysfunction."

The AVEIR DR i2i system doesn't have those limitations. It was, however, associated with 35 device- or procedure-related complications in the study, of which the most common was procedural arrhythmia, "namely atrial fibrillation," Cantillon said.

Atrial fibrillation can develop during implantation of pacemakers with transvenous leads but are generally terminated without being considered an important event. Yet the study classified it as a serious complication, inflating the complication rate, because "the patients had to be restored to sinus rhythm so we could assess the AV synchrony and also the atrial electrical performance," he said.

Some of the devices dislodged from their implantation site within a month of the procedure, but "all of those patients were successfully managed percutaneously," said Cantillon.

"The 1.7% dislodgement rate is something that we will need to keep an eye on, as embolization of devices is always a significant concern," Piccini said. Still, the observed total complication rate "was certainly in line" with rates associated with conventional pacemaker implantation.

Reliable AV Synchrony

Fred M. Kusumoto, MD, Mayo Clinic, Jacksonville, Florida, lauded what seems to be the system's "incredibly reliable AV synchrony in different conditions, albeit in a very controlled environment."

Of interest will be whether its performance, including maintenance of AV synchrony, holds up in "a more long-term evaluation in the outpatient setting," said Kusumoto, speaking as the invited discussant for Cantillon's presentation.

Also missing or in short supply from the study, he observed, are insights about long-term efficacy and complications, battery longevity, effectiveness of its rate-responsive capability, and any effect on clinical outcomes.

Local Body Network

Of the study's 300 patients (mean age 69 years; 38% female) at 55 sites in Canada, Europe, and the United States, 63.3% had sinus-node dysfunction and 33.3% had AV block as their primary dual-chamber pacing indication; 298 were successfully implanted with both devices.

About 45% had a history of supraventricular arrhythmia, 4.3% had prior ventricular arrhythmia, and 20% had a history of arrhythmia ablation.

By 3 months, the group reported, the primary safety endpoint (freedom from device- or procedure-related serious adverse events) occurred in 90.3%, compared with the performance goal of 78% (P < .001).

The first of two primary performance endpoints (adequate atrial capture threshold and sensing amplitude by predefined criteria) was met in 90.2%, surpassing the 82.5% performance goal (P < .001).

The second primary performance goal (at least 70% AV synchrony with the patient sitting) was seen in 97.3% against the performance goal of 83% (P < .001).

What shouldn't be "glossed over" from the study, Kusumoto offered, is that it's possible to achieve a wireless connection "between two devices that are actually intracardiac." That raises the prospect of a "local body network" that could be "expanded even more dramatically with other types of devices. I mean, think of the paradigm shift."

The AVEIR DR i2i trial was funded by Abbott. Cantillon discloses receiving honoraria or fees for speaking or consulting from Abbott Laboratories, Boston Scientific, Biosense Webster, and Shockwave Medical; and holding royalty rights with AirStrip. Disclosures for the other authors can be found at NEJM.org. Piccini has disclosed relationships with Abbott, Medtronic, Biotronik, Boston Scientific, and other drug and medical device companies. Kusumoto reports no relevant financial relationships.

Heart Rhythm Society 2023. Abstract LB-456640-1, Late Breaking Clinical Trials and Science – Innovations. Presented May 20, 2023.

N Engl J Med. Published online May 20, 2023. Full Text

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