Dual-Chamber Leadless Pacemaker Impresses in Safety-and-Performance Study

NEW ORLEANS -- A leadless dual-chamber pacemaker with bidirectional wireless communication turned in very promising short-term results in patients with standard indications for dual-chamber pacing, according to the Aveir DR i2i Study.

The implantation procedure, consisting of two functioning leadless pacemakers that established implant-to-implant communication, was successful in 98.3% (n=295 of 300) of trial patients, reported Daniel Cantillon, MD, of Masimo in Irvine, California, at the Heart Rhythm Society (HRS) meeting.

"These results at 3-months follow-up were very encouraging and positive," he said at an HRS press conference. The study findings were simultaneously published in the New England Journal of Medicine. Cantillion is an Aveir DR i2i Study co-investigator and was at the Cleveland Clinic when the dual-chamber leadless pacemaker system was developed.

He reported that for the current study, 190 patients were diagnosed with sinus-node dysfunction and 100 patients were diagnosed with atrioventricular block as the primary pacing indication. The ongoing study will eventually include up to 550 patients eligible for dual-chamber pacing.

Cantillion and colleagues reported that the study's primary safety endpoint -- freedom from device- or procedure-related serious adverse events (AEs) at 90 days -- was met in 90.3% ( 95% CI 87.0-93.7) of patients, and that exceeded the performance goal of 78% (P<0.001). There were 35 of these AEs in 29 study patients.

Also, the first primary performance endpoint -- a combination of adequate atrial capture threshold and sensing amplitude at 3 months -- was met in 90.2% of the patients (95% CI 86.8-93.6), which exceeded the performance goal of 82.5% (P<0.001).

The mean atrial capture threshold was 0.82 V, while the mean P-wave amplitude was 3.58 mV, according to the researchers, who also reported that among 7% with a P-wave amplitude of <1.0 mV, no one needed device revision for inadequate sensing.

And the second primary performance endpoint was at least 70% atrioventricular synchrony at 3 months while the patient was seated, and 97.3% (95% CI 95.4-99.3) achieved this, thereby exceeding the performance goal of 83% (P<0.001).

"Each leadless pacemaker is 6.5 mm in diameter and affixes to the endocardium through an active fixation helix," the researchers explained. "The ventricular leadless pacemaker measures 38 mm in length and has a target site for implantation in the lower to mid-septal area of the right ventricle." Fluoroscopy was required for all procedures, while intracardiac echocardiography could be used as an assist for guiding implantation.

A little over 62.7% of the patients were male (age 69.2) while around 67% where white. About 61% were in the U.S. and about 63% had a primary pacemaker indication of sinus-node dysfunction.

The researchers reported 28 complications occurred within 2 days after implantation. Complications included atrial fibrillation, serious cardiac injury events, and intraprocedural dislodgements of a leadless pacemaker. "Five dislodgements were related to inadequate fixation, and in one case the pacemaker was mechanically dislodged by an intracardiac echocardiography catheter. In all cases, the dislodged leadless pacemaker was retrieved successfully and reimplanted during the initial procedure," the researchers said.

They also noted that "no procedure or device-related deaths occurred. The incidence of acute complications was similar to that observed in studies of transvenous dual-chamber pacemakers. In our study, serious cardiac injury of pericardial effusion occurred in 0.7% of the patients, which compares favorably to both the 0.8% incidence of perforation in a recent meta-analysis of transvenous pacemaker studies and the 1.5% incidence of perforation in the initial single-chamber leadless pacemaker trials."

Study limitations included its "single-group nature, which precluded a direct comparison of [the device's] safety and performance with those of conventional transvenous pacemakers." Also, only short-term follow-up data were reported.

"Although this dual-chamber system requires implantation of two devices, the low percentage of patients with perforation in our study most likely stems in part from the selection of investigators who had substantial experience with leadless pacemaker implantation and rigorous pre-study training. We observed a higher-than-expected incidence of dislodgement during and after the implantation procedure: 1.7% for each, as compared with the 1.1% in the initial trial of the ventricular leadless pacemaker, 0.11% in real-world experience with ventricular leadless pacemakers, and 1.9% for atrial lead dislocation within 2 months in real-world experience with transvenous pacemakers," the researchers reported.

Cantillion stressed that "all of these dislodgements were successfully managed percutaneously."

He pointed out to MedPage Today that traditional pacemakers have complications that affect one in six patients after 3 years of follow-up, and those are overwhelmingly related to the transvenous leads and to the incisional access necessary for the surgical pocket. Leadless pacemakers have neither, he said.

HRS press conference moderator Fred Kusumoto, MD, of the Mayo Clinic in Jacksonville, Florida, told MedPage Today that "the lead is the weakest link in pacemaker technology. There are many times when we have issues with leads. Getting rid of leads is a valuable strategy."

"But whenever we put in any kind of device, it is over the arc of a patient's lifetime that they are trying to give therapy, so the question is how is this going to fit into something that we have a very established technology for [that] has been around now for 70 years," Kusumoto said.

"We don't know if this new device will provide the optimal way to pace the heart. This is exiting technology, and great proof-of-concept, but it is the first step in a large staircase," he said.